Conference vmszoo::rc

    Dan,
    
    I know, that's why I suggested it as "food for thought". :-)
    
    Also, if you want great success at Electrics, may I suggest a Goldberg
    Electra.  Several fly at our field and are fantastic.  It is available
    without motor for about $30 and for about $50 with electrics.  And
    they fly very well and see to land in the grass with no damage.
    Flights are generally 15 minutes plus when there is NO thermal activity
    an 20 plus when there is.
    
    Chris

	re .7

>								 I
>    usually only got two or three flights before the prop was broken.
>    (No landing gear is rough on props!!)
    
             
	Not if you put the prop on correctly... My Mirus has no u/c and
	I've yet to break the prop.

	cheers

	bob
    

    Glad this topic has stirred up some interest.
    
    I'm still confused. There must be 3 or 4 motors (540, 340RS? etc)
    mentioned. Here are some questions:

    *    What do all those numbers mean? 

    *    Is there any anaolgy with infernal cumbustion engine numbers? 

    *    What about field chargers? (functionality etc)

    *    How much heat do the cells generate?

    *    There seems to be a huge price range for these motors, what do you
    	 get for your money? (other than for Cobalt motors)

    *    Is there any truth in the rumour that "pulsed" electric speed
	 controllers destroy anything but a Cobalt motor (I understand how 
	 Cobalt motors are better than the rest!)? 

    *    How large are the currents involved: one wiring diagram I saw showed a
	 micro-switch for controlling the motor. Would a micro-switch be "man
	 enough" for the job?
    
    Cheers,
    
    Keith.

    Dan,
    
    Thanks for the information so far. I must admit, my understanding
    of electricity and electronics can be likened to islands in the
    sea; I seem to understand something the experts see as complex (the
    islands) and totally fail to comprehend things they see as simple
    (the majority of the time, the sea). This is my excuse for dumb 
    questions and I'm sticking to it...
    
    The "pulsed" speed controller is my way of describing a proportional
    electronic speed controller which works by "squirting" current at
    the motor in short bursts, each burst being separated by a varying
    time interval: the longer the interval, the slower the motor runs.
    If you give enough "bursts per minute", the effect is smooth but
    controlled rpm. Now my question relates to the fact that such a
    set up is constantly starting and stopping the motor and generally
    doing strange things with the magnetic fields within the motor.
    This (I think) may cause the permanent magnets in the motor to become
    "confused" and so reduce the power of the motor (wow, I may have
    fouled up electricity AND physics with that one!). Right/wrong?
    
    Keith.

    Another question:
    
    
    This has always puzzled me: why if a 1000mah pack can deliver 1
    amp for 1 hour or 60 amps for 1 minute doesn't it always deliver
    60 amps for 1 minute? I guess someone will mention "back EMF" or
    something, and I follow the principle, but given that, why does
    a motor ever burn out at all?
    
    (Really dumb question sorry)
    
    Keith.

Well, a couple of answers here:

Dan, I think that motor currents generally run much higher than
the 6-10 amps you mention.  My .035 draws approximately 7 amps in
normal running with 5 cells and a 6-3 prop.  Generally, a .05
size motor, with the usual 6-7 cells will hit 15 to 20 amps.  The
bigger motors with more cells will run at higer currents than
that, up to 50 amps or so.  The thing about an electric motor is
that as you put a load on it, it doesn't slow down; it runs at
its rated speed and draws more current, until it burns up.  This
is the reasoning behind the movement to rate motors in terms of
its power (watts), rather than in terms of equivalent 2-cycle
sizes; that the maximum power a motor can handle is its true
capacity.  Makes prop selection and comparison easy because you
just hook up an ammmeter and try props.  The cobalts, with their
denser magnetic fields can handle more power more efficiently.

On pulsed dc controllers.  Yes that has been done, I don't think
that there is any problem with it.  What they do is give the
motor a "high voltage" shot, then let it "coast"; the timing of
the pulses determines the speed.  The risk is that the high
voltage; that is a higher voltage than would be applied in steady
state for the same power causes higher currents in the motor and
therefore higher chance of overheating damage.  Normally, the
controllers don't cause this problem.  Nowadays, with power FET
technology, I believe they just regulate the conduction of the
FET directly so the motor gets a steady state voltage.  I may
well be wrong on that one.

Yes, a 1000 mA/hr battery will produce 60 amps for 1 minute, no
questions asked.  Of course, it will generate lots of heat in the
process, thereby disturbing the direct relationship; I mean that
the actual time may be less than 1 minute, but its close enough.
Also, doing this will reduce the battery's life, but it'll do it.

I use a 44 ah single nicad for my glow plug lighter.  I refer to
it as "The Nicad That Ate Chicago".  Found it in a surplus store.
I've charged it once, the inital charge, about a month ago; its
still going very strong. 

	re .a couple ago    
    
>    This has always puzzled me: why if a 1000mah pack can deliver 1
>    amp for 1 hour or 60 amps for 1 minute doesn't it always deliver
>    60 amps for 1 minute? I guess someone will mention "back EMF" or
>    something, and I follow the principle, but given that, why does
>    a motor ever burn out at all?
    
 
      The discharge rate of a cell depends on the resistive load you
	put accross it... if you liken you cell to a bucket of water(?),
	the water could come out of a hole in the bottom of the bucket
	at a rate proportional to the size of the hole... If you put
	a small hole( high resistance) in you bucket the water will come
	slowly for a long time (and your plane would go soggy). if you
	make a big hole (low resiatance) the water come out quickly for
	a shorter time...

	The rate of water flow is analogous to the current supplied
	by the cell.. I guess you could take a liberty with ohm's
	law as follows :-


	Flow rate (current)= volume of bucket (volts)
                                 ----------------             
		               size of hole (ohms)
                                                  
	With an electric motor the resistance depends on the length of wire
	used in the winding. The shorter the wire the less the resistance
	the higher the current the quicker the cell discharges...

	However the higher current produces a higher magnetic field in the
	armature and makes it turn faster/more torque...

	bob


	ps that bitr with 540 being the run time in seconds is really neat.
	   Almost too neat to be true..... Learn something every day eh?

    Let's clear up some things about DC motors.  All small DC motors
    use permanent magnets to generate the Magnetic Field.  The Torque
    produced by the armature is proportional to the Field strength
    times the Armature Current times the number of turns of wire on
    the Armature. (only count the turns that are energized)
    
    The motor speed is not constant!  A DC motor runs at rated speed
    only when presented with its rated load and rated terminal voltage.
    Assuming a fixed terminal voltage, two things determine the motor's
    current draw:
    
    1. The resistance of the armauture Ra
    2. The armature back EMF (this is the voltage generated by the
       armature rotating in the permanent magnet's field.  The back
       EMF is therefor proportional to the motor speed in RPM and the
       field strength. (field is fixed by the magnets)
    
    The following equation describes this relationship:
    
    		Vt = Ia*Ra + V(EMF)
                
    If you stall the motor, then the armature resistance is the only
    thing limiting the current, and the current will be high.  If you
    run the motor with no load, it will accelerate until the current
    draw drops to just compensate for friction and windage losses.
    You will get high RPM and low current.
                                          
    Torque produced times the speed in RPM defines the useful work done
    by a motor. (any motor)  The heat losses in a DC motor are proportional
    to the Armature Current, Ra.  The loss in Watts (my pen name) =
    Ia*Ia*Ra.  To get a DC motor to run at its rated speed with the
    rated voltage applied to it, you must load it to its rated torque.
    This might require a gearbox or a different prop for an airplane.
    You can measure motor current (or time the discharge of a known
    capacity battery) to determine if the motor is properly loaded.
    
    
    I will go into details of pulsed and resistive speed controllers
    later.  There are several design tradeoffs that must be considered.
    
    I hope this info proves interesting to someone out there.
    
    Charlie Watt (Volt Ampere)

    
    	Let's get back to the original questions.
    
    If you want to fly a slow trainer type or are into gliders then
    the Electra is a good choice.  It is a matched system that is a
    proven combination.  Weight is the name of the game when it comes
    to electrics.
    
    If you are past this stage or want something with more performance
    try the Wasp form Leisure.  I have been flying one since summer
    and it performs very well with the Leisure LT50 system.  That is
    an 05 rated motor with a 6 cell 1.2AH pack.  It is a semi sym wing
    no dehedral and weighs about 29oz ready to fly.   I get about 7
    min of fast aerobatic flying.  The kit and motor go for about 60
    bucks.  It is not a cobalt motor but then who want's to spend $100
    or more  for an electric when you are just starting.  
    
    I use a 6/7 cell astro dc charger and have 2 battery packs.  The
    plane is covered with mono no landing gear and is hand launched.
    It uses a cox 6/3 grey prop and turns about 13000 rpm.  I use micro
    servos and have on/off.  I don't think propo on a small motor would
    be very helpfull.
    
    I would stay away from the rs series motors and start with a proven
    setup, get something that performs then experiment.  Also don't
    forget to put a fuse in the circuit in case of crash. A stuck motor
    will burn itself out in no time at all.
    
    Don't be afraid of electrics, they are a lot of fun and eliminate
    some of the hassles when you fly in the winter.  Easy to start and
    no messy fuel freezing your hands.
    
    I have the plans for the Electrostreak from the AMA mag.  It is
    a 4 channnel 05 size.  Plan to build it this winter.  Will let you
    know how it flys.
    
    

    Charlie,
    
    .20 just did what several physics teachers couldn't! Thanks! The
    bit I never understood was the part about "load". 
    
    Now I understand the comment about trying different props and noting
    the current drawn each time - presumably the wrong prop will at best be
    inefficient and at worst shorten the life of the engine. One question
    around that area is: will the behaviour of the motor in flight be
    different than when static and if so, what do you reckon will happen to
    the current drain? 
    
    Question 2: (I can ask questions for hours!) there seems to be two
    types of motor classification in use: 540 380 etc and .05, .10 and
    .20. I guess the latter relates to equivalent IC power (?) but how
    do the two electric motor classes relate to each other?

    Cheers,
    
    Keith.

One of the columnists, probably in MA mentioned this one a few
months ago.  The Japanese motors are classified in seconds of
running time, as an earlier note stated.  The German motors, such
as Keller, are rated by power, I think in Watts.   The columnist
took note of this since it is just what he is avocating. 

Thanks, Charlie for a far better explaination than I gave.  

Just had to add my $.02 worth

1.  There was a recent review of the Carl Goldberg Electra (in RCM I think)
    and the author said it was OK - until he threw away the 540 and put in
    an Astro Cobalt 05.  Then he thought it was good.
 
>    Question 2: (I can ask questions for hours!) there seems to be two
>    types of motor classification in use: 540 380 etc and .05, .10 and
>    .20. I guess the latter relates to equivalent IC power (?) but how
>    do the two electric motor classes relate to each other?

2.   I believe (I'm sure I'll be corrected here if I'm wrong) that the
     motor size equaling the run time is just a cute model designation
     done by Kyosho on there Lemans motors.  The 540 number was originally
     from Tamiya (MRC (Model Rectifier Corporation)) and has been universally
     applied to a series of motors with the same physical dimensions and
     ruffly the same current draw.  In fact the "Black" and "Gold" versions
     are also considered types of 540s (Hot 540s).  The Lemans 600 would
     go approximately 600 seconds, 240 = 240 seconds, etc... but only
     with a 7.2 Volt battery (6 cell pack) and now the RC car nuts have all
     switched to 8.4 Volt batteries (7 cell pack) and I'm sure the minutes
     are close but they changed.  Also your mileage will very.  If you 
     have a car with full bearings you will run noticeably longer and faster
     than one without.

     Bottom line is that electrics are not yet of age.  If you have to build
     a plane lighter - throw away the landing gear - live with .049 performance
     - and 6 minute flights - then they are not of age.  What they are
     waiting for is a breakthru in battery technology.  As soon as someone
     develops light weight (and not overly large) battery then the glow
     engine manufactures will go out of business in a year.

     Don't start the hate mail.  I want the electrics to succeed.  When ever
     somebody shows up at the field with an electric I'm the first one to
     start asking questions and examining the thing.  I think that Carl
     Goldberg probably will be the catalytic provokitour(sp) of electric flying
     and I may someday also get an Electra and I may also try it on the
     standard RS540 (to save a buck).

     Soooooo
	Good luck electrics - now where is that Ni-Starter again.

              _!_      
Bye        ----O----   
Kay R. Fisher / \     

================================================================================

>     I believe (I'm sure I'll be corrected here if I'm wrong) that the
>     motor size equaling the run time is just a cute model designation
>     done by Kyosho on there Lemans motors.  The 540 number was originally
>     from Tamiya (MRC (Model Rectifier Corporation)) and has been universally
>     applied to a series of motors with the same physical dimensions and
>     ruffly the same current draw.  In fact the "Black" and "Gold" versions
>     are also considered types of 540s (Hot 540s).  The Lemans 600 would
>     go approximately 600 seconds, 240 = 240 seconds, etc... but only
>     with a 7.2 Volt battery (6 cell pack) and now the RC car nuts have all
>     switched to 8.4 Volt batteries (7 cell pack) and I'm sure the minutes
>     are close but they changed.  Also your mileage will very.  If you 
>     have a car with full bearings you will run noticeably longer and faster
>     than one without.

Case in point the Tamiya (MRC) RS-380 does not run 380 seconds (6.3 minutes)
it in fact runs approximately 15 minutes.  It is much less powerful than
the RS-540, and smaller and draws less current and runs much longer on the
same battery.  And it is from Japan.  Warning for car buffs.  If your thinking
about a Christmas toy car - don't get one with a RS-380 motor because in
many cases because they are smaller the space allocated for them is also smaller
and you can't upgrade them to a RS-540/"Black"/"Gold"/Lemans series/etc.

              _!_      
Bye        ----O----   
Kay R. Fisher / \     

================================================================================

    re.24
    Keith,
    	The issue of electric motor specs for hobby use is confusing.
    The large numbers are run time in seconds on a standard battery
    under normal load.  These were primarily designed for RC Cars since
    this is the major electric hobby application.  The smaller the number,
    the higher the current draw.
    
    	You are right on the money on the issue of prop selection. 
    The motor will pick up rpm's in the air over static on the ground,
    and therefor the current draw will be less in the air.  Timing the
    flight on a full charge should give you an idea of what the in flight
    current draw is on average.  First time a run on the ground, and
    then time a couple of flights.  The per-cent difference in current
    in the air will be the same as the per-cent difference in run time.
    
    	By the way, there is another interesting difference between
    DC electric motors and Gas powered ones: and this is the torque
    and horsepower curves.  In an electric motor, the torque is directly
    proportional to current: T=K*I  Therefor, the more current you draw,
    the higher the torque.  Since the back EMF is proportional to speed
    in RPM, this says that with a constant voltage load (Battery) the
    motor will generate more torque if you slow it down with a bigger
    load.  This works all the way down to zero RPM or stalled.  I have
    driven electric cars and you can put it in gear with the motor stopped
    and jump on the power pedel (no gas pedel) and spin the wheels from
    a dead stop.  A gas engine has a nonlinear torque curve that peaks
    at some RPM.  Maximum horsepower or work done by the motor is
    calculated by multiplying torque times speed.  For a gas engine,
    the nonlinear peaking torque curve determines the optimum operating
    rpm to get maximum power.  Maximum power does not occur at maximum
    torque RPM for all gas engines, but it is usually close.  For sure,
    it is usually at HIGH rpms.  For a non turbocharged gas engine,
    torque falls off at high rpm because you can't get enough fuel,air
    mixture in through the valves or ports.  Since an electric motor
    increases torque as you slow it down with an increased load, you
    do not get more power by getting the rpm's up by putting on a smaller
    prop.  The best thing to do with an electric motor is to adjust
    the load with a gearbox or prop diameter/pitch change to get the
    rated current draw.
    
    One thing I would highly recommend when building an electric car
    or plane, is to make sure to minimize the resistance in the wiring
    and switches.  You can really loose alot of performance if you are
    sloppy or use wire that is too small in diameter.  For example,
    If you draw 20 amps out of a 12Volt battery, this is 240Watts of
    total power.  If you had .1 ohms of wiring resistance, you would
    drop 20 * .1 or 2 volts across the wiring.  The power dissipated
    in the wiring would be I*I*R = 40 Watts!  you just wasted 17 per-cent
    of your total power and made your wiring hot as well.
    
    Also, even though it will dissipate some power, always use a fuse
    in the battery lead to protect your wiring and the battery from
    certain destruction due to shorting.  Nicads can explode if you
    short them.  If the short circit current was 100 amps, the battery
    would dissipate 1200 Watts.  This is about what a coffe pot heater
    dissipates to make a pot of coffee. (Burn City!)
    
    Enough for now,
    
    Charlie
    

    Re: -.26..., Kay,
    
    I just have to disagree with yer' statement that glo-engine
    manufacturers will go out of business within a year if/when electric
    comes of age.  Yer' statement may well be true regarding surface
    craft [electric "already" dominates this field] but I frankly doubt
    that electric could ever totally supplant internal combustion [IC]
    power for aircraft...there're just too many things I doubt the electrics
    could ever do [at least well] with respect to aircraft, e.g. I
    can't imagine electric powered ducted fans.
    
    I realize that noise is one of our biggest enemies presently [though
    the impact is minimal to non-existant out here in the wide open
    spaces] but a large segment of modelers are going to prefer the
    sound [even muffled] of an IC engine over electric even "if" all
    other parameters "were" equal.  `Til the day when electric [or some
    other silent] power is the accepted norm for full scale power plants,
    my opinion [and that's "all" it is] is that IC engines will predominate
    as the preferred power source for model aircraft. 
    
    No one asked, just my opinion...., adios,	Al

    Al is completely right!  The only way electric will replace IC is
    if IC engines are banned for noise reasons.  Battery technology
    is the limiting factor for electric, and that field moves at a snail's
    pace if at all.  The battery you have in your car is the same as
    was used 30-40 years ago except for minor improvements like a plastic
    case instead of a rubber one.  The hobby industry could not afford
    any of the higher energy density batteries that have been invented
    as of yet.  Also, most of them are very chemically active and difficult
    to handle savely.  Some use liquid sodium.  Have any of you seen
    what happens when this stuff comes in contact with H20?  Not to
    mention that the melting point is way up there.  We could have some
    really interesting crashes with these batteries.  I really doubt
    that we will see much improvement over the NICADS that we presently
    have available to us.  By the way, if I'm wrong, I will be the first
    one to switch to electric, but I won't do this until the performance
    and price is as good as a gas powered plane.
    
    Charlie
    

    Charlie, thanks for the extra input - keep it coming, I may soon
    be able to re-take my school exams!!! :-) Seriously, it is appreciated.
    
    Kay, Al - I have to agree. The reason I started this topic however,
    was a very interesting article I read in a recent magazine. Here
    the writer was talking about 7.5lb single engined scale models (Hawker
    Tomtit I think) and an 11.5lb twin engined LeO II (???). Both these
    had flight times around the 10 minute mark and claimed to be able to
    ROG at half to three quarter power. He also talked about the �150.00
    motor (read EXPENSIVE) and motors capable of handling 2000+ watts
    - anyone seen/tried these bigger motors?? So you see, it's not the
    less-power-than-a-.049 that I expected. Just thought I'd check with
    the experts. RC.NOTE is great forum for researching an interest,
    be it real or academic.
    
    Notice however that the 'planes mentioned aren't exactly high
    performance. But (and here I guess Al will throw a spanner at me across
    the "pond"!) I think that electric powered scale models especially the
    slower flying types might have quite a future in them. Certainly,
    electrics do have several distinct advantages over glo powered models -
    there is for me a great charm in being able to walk to the runway, push
    the throtle forward and take off: no fuss! I'm almost certain to give
    one a try! 
    
    Keith.
    
    BTW: Kay - if they ever sort out rechargeable cells properly, I
    think we can wave good bye to 99% of the worlds Infernal Combustion
    engines, not just in the modelling sphere. No bad thing too (and
    this from someone who LOVES tinkering with his car engine each
    Sunday...)

    Next questions:
    
    Are all nicads suitable for fast charging?
    
    How are field chargers designed? I don't want to build one myself
    (not yet anyway) but I like to know how these things work. Question
    is, how much current does the charger push into the pack and what
    criteria does it use to decide when enough's enough?
    
    Keith.

In the whole world of nicads, not all are suitable for fast
charging.  However, most of the ones of recent manufacture are
fast chargable.  All fast charging nicads are so marked on their
case.

As to fast chargers.  The garden variety is composed of a simple
shutoff switch timer and a load resistor.  The amount of charge
the nicad gets is strictly dependent on the resistor and the time
of charge; there is no monitoring of the pack.  More
"sophisticated" chargers monitor the pack temperature, based on
the fact that the pack heats rapidly at full charge.  Personally,
I don't find this very dependable because the temperature is
dependent on the contact between the probe and the cells, because
the cells heat at different rates, and because the temperature
lags enough behind the charge to still harm the battery.

Still more sophisitcated chargers deliver the current to the
battery in pulses, then monitors the battery voltage.  This is
based on the fact that the battery resistance goes up at full
charge, so the pause is to check the resistance of the cell --
the charger puts a load on the battery for this.  Charging
terminates when the cell resistance reaches about .3 ohms.  The
most sophisticated contains a small microprocessor to do this. 

My own philosophy is that all that is pure bunk; there is no good
way to fast charge batteries and to ensure not destroying them.
My charger uses a strict 15 hour timer and C/10 rate; but then
again it is  designed for transmitter and flight packs.  Fast
charging those asks for trouble.  I consider a battery fully
charged at 1.31 Volts/cell, though it can go as high as 1.35
V/cell (this is measured with a C/2 load; about 250 mA for a 500
mA pack).

I would not be so particular about a motor battery, and would
charge one without qualm at a 1-hr rate for a 800 mA pack; about
1 amp.   The typical fast charging rate is 15 minutes, about 3A
rate. 

    GE has an excellent book on NICAD batteries that goes into all of
    the technical details on applications and proper charging as well
    as failure modes and their causes.  I learned alot from this book.
    I will add an entry on the title and author if I can dig it up at
    home.  

    
    Yeah I read that book you're talking about.  It was very good.
    I think it said that the vented-cell batteries are the ones you
    can fast-charge.  There is definitely a penalty for fast-charging.
    As the cell heats up it vents gases and loses a small portion of
    its capacity.  If you overcharge while fast charging you really
    reduce the life of the battery, but if you overcharge with a C/10
    rate it doesn't hurt much at all because the cell doesn't heat up.
    	If memory serves me right, it said that you CANNOT fast-charge
    sealed cells (you can tell the vented ones by a hole on one end).
    I guess the sealed ones can explode, but their advantage is that
    they last longer (more recharge cycles that is).

    Bill

A third vote for that GE book; I read an early edition of it.

Unfortunately, GE's commercial cells, and the cells that you find
in the dept store, are very second rate.   There's a big
difference between these and the ones we use.  When I talk of
nicad cells I mean the ones by Sanyo and other manufacturers that
we find in the hobby shops.  Those are made for the kinds of
stresses we put on them. 

If memory serves me right, and I am very unsure on this point, I
think that venting in itself is not the only criteria that
qualifies a cell for fast charging.  It seems that I've read in
one of the model columns that the cell must be marked for fast
charging.  I believe there is something in the internal
construction that does this.  For instance. the commercial AAA
cells that I use in my pocket radio; they're made by Eveready and
are vented, but are not marked "fast charging". 

    	On the way into work this AM the news had a piece about SONY
    discovering a new battery technology. Something-lithium batteries
    that are 1/4 the weight and twice the power of Ni-cads. Should be
    available for consumers sometime late next year.
    
    	Al - They're closing in on the IC engines 8^)
    
    	Art

    
    	I believe in the last AMA rag there was an artical about a new
    nicad that will be out in a few months.  The example that was cited
    is a 1.7ah in a 1.2ah size that was only about .1 oz heaver with
    an increase in cost of about 30%.  Progress may be slow but as the
    demand for the technology increases so will the products.  
    	Ref .-1 I wonder what the cost will be?
                                       

    
    	Beware of lithium-air batteries!  The ones I've seen are not
    rechargeable.  The advantages are that they have a tremendous shelf
    life and great capacity/weight.  This disadvantage is that they
    have an almost perfectly flat discharge curve followed by a sharp
    knee.  I wouldn't use one of these in any critical application since
    you never know how much capacity is left.  But they are great for
    flashlights and ELTs...

The lithium batteries are part of an new technology that I've
been keeping an eye on for several years now.  I think that the
other material is silver, could be wrong.  Anyway, the latest
information I've seen on it, in EDN earlier this year puts the
batteries a couple of years off yet.  They will be rechargable,
and will have the 3V/cell output of the current lithium cell.  By
then the 3V logic technology should be well on its way, and we'll
be seeing surface mounting technology PCM sets with 3V supplies.

    The black GE rechargeables you can buy at Leechmeres are the worst
    batteries off the GE production line.  Literally.  They're the ones
    that flunk the higher-quality inspection, yet still hold a charge.
    	
    The best grade NiCad GE battery is the gold-top; they aren't sold
    in retail stores.  GE distributors sell them; you can also get them
    from 
    	
    		Herbach and Raedermann,
    		Philadelphia, PA.
    	
    (H&R are very dependable people; call Philadelphia Info. and get
    their newest phone number; I know they've moved since my last purchase
    (about 6 months ago)).  Their normal delivery mode is UPS second
    day air, they will "next-day" it for a couple of bucks more.  
    	
    	H&R also sell the cheap GE NiCads and the middling ones.  They'll
    read you specs over the phone fearlessly.  As I recall a black GE
    had about 1 AH capacity, the gold-cap GE had nearly 4 AH.  Gold-caps
    cost about 3$ per, though.
    	
    	H&R also sells Gates lead-acid superbatteries; they weigh about
    20% more than NiCads but REALLY put out the current; the maximum
    current for the 6" cell is on the order of 2000 amperes!  (enough
    to turn copper to vapor).  I keep thinking of neat things to do
    with such a critter ("Got any 40-watt plasma rifles?" "Just what
    you see here, Mac.")   
    
    	Cripes, all this talk makes me wanna hang up my SuperShot and
    get a Duet!
    	         
    ------------------------------
    	
    Solid-state (pulser) speed controllers: I have a Futaba solid-state
    controller controlling a 6-cell racing pack into an RS-540 Black.
    No problems in at least 300 runs.  The motor does not appear to
    have been "demagnetized".  Both the motor and the battery
    get somewhat warm after a hard race.   The controller stays cool.
    It only weighs about 1.5 ounces, too.  The controller went in when
    the switch-and-resistor-board system caught fire on the starting
    line.
    	
    The folder from Futaba says that one should carefully insulate the
    motor leads.  Futaba says the controller is thermally protected and
    will shut down itself AND the motor in event of protracted motor stall-
    but will destroy itself if the motor leads themselves are shorted. I
    find I get about 20% longer runs with the electronic control over the
    switcher (but I do a lot of flat-out full throttle abuse). There's a
    relay inside the Futaba that cuts out the .7 volts voltage drop of the
    switching transistor when you hit full throttle. 
    
    The electronic controller also regulates 6 volt power for it's own
    use, and feeds extra 6 volt power out the servo control line for
    the reciever pack and other servos to use.  Hence, as long as you
    have propulsion power, you have RX power too.  Corrolary: lose
    propulsion, lose RX too!  OK in a car, something to think about
    in a plane.  At least it can't fly away at full throttle.
     
    	-Bill Yerazunis
                                                    

    re: .-1
    
    Bill,
    
    I've seen several motor-and-RX power packs - I must confess they
    scare me more than a little for a 'plane. Don't think I'll be getting
    one of those...
    
    re. -??
    
    Kay,
    
    Heresay only I'm afraid, but the article which sparked off my interest
    was one describing a 7.5 lb scale bi-plane with enough power for
    ROG from hard runway OR grass and then 10-12 minute flights. Sounds
    too good to be true - which is why I decided to ask the experts.
    
    Keith.

    Another point occured to me on the weekend: If fast charge cells
    need venting when fast charging, do they also vent when fast
    discharging? If so, what gases are they giving off and how important
    is it to get those gases out of the model?? (I have visions of a
    gas build up, a small spark and a LOUD bang!)
    
    Keith.

    The vent serves two purposes: First to allow for expansion as the
    cell gets warm from resistance losses during charge and discharge;
    and second to vent gasses generated during overcharge.  The
    disadvantage to fast charging is that you MUST NOT overcharge.
    Cell life will suffer and you will blow the seals if you do.
    In electric car applications, it works out ok if you know that
    the pack is discharged fully and time the charge carefully.
    I would strongly recommend that noone fast charge the flight
    batteries for a plane.  First, you usually don't discharge them
    fully before charging, and second, the batteries are really not
    high current ones.  If you charge at .1C or 50 ma for most flight
    packs, you don't have to worry about over charging the batteries.
    
    Charlie
    

    Charlie,
    
    By flight pack I assume you mean the power pack for the radio and
    not for the propulsion, right?
    
    If wrong, I'm a bit confused. Help!
    
    Keith.

    Keith,
    	Yes, I was only refering to the flight radio batteries, both
    TX and RX.  The propulsion batteries are designed for high currents
    and can be safely fast charged.  I wouldn't expect that anyone would
    want to wait around while slow charging between flights.  You would
    need a large handful of batteries for a flying session.  
    	I do not trust most fast chargers for small 500MA-HR cells as
    far as I could throw them.  There are too many variables to consider
    and most of the units cut corners to save $$$.  I have talked to
    serveral people who have experienced battery failure due to trying
    to fast charge flight radio batteries.  If you have a charger that
    senses battery voltage to shut down charge, a poor connection to
    the battery will raise the measured voltage and cause premature
    charger shutdown.  You never can be sure that you have a fully charged
    battery!  If this happens to the propulsion battery, you get a short
    flight and you can fly again after charging.  If it happens to the
    RX battery, you also get a short flight, but usually you don't fly
    that plane again if you are lucky enough to find it.
    
    DON'T FAST CHARGE any battery pack that you need to rely on for
    flight safety.
    
    CHarlie
    

    I'm a bit confused by the various electronic speed controls available.
    I'm looking for something that can do fully proportional forward
    and fully proportional reverse, but there's only one that I've seen
    that claims both (and given the advertising hype I've seen in RCM,
    I don't trust any manufacturer!  I keep getting the feeling I've
    picked up a DAK catalog....).  I don't think I need braking, but
    are the "fully proportional forward and reverse" controllers really
    proportional forward and FIXED reverse, or what?  Anyone have any
    experience with various controllers care to offer any hints?  I'm
    also wondering why anyone would need a speed controller that can
    handle 75 or so amps....   Also does the peak rating on speed
    controllers mean 'on the order of seconds' or 'not for more than
    10 microseconds'?
    
    Willie
    

    
    I've been discussing my plane under winter projects '88, but decided
    it was time to bring it and some questions to this note. The plane
    is an original design fuse' and tail feathers using the Piece O'
    Cake 6' wing. Weight is 3 pounds, power is an RS540 swinging a Kyosho
    9-8 prop thru a 2:1(approx.) gear reduction, 7.2V 1200mah power
    source. Right now I'm getting about 6 minute runs on the motor,
    and was able to stretch a flight Sunday to about 15+ minutes. I
    may have gained about 1 minute on flying time by finally attacking
    the badly wrinkled wing (my first attempt at iron-on's) with my
    heat gun and got all the wrinkles out. My question is this, what
    will I gain if I put an Astro 05 (non-cobalt) in this plane? And
    would changing props buy me anything, and if so, which direction
    should I start in? Please try not to be too technical, I got completly
    confused trying to follow the discussion on props a few months ago.
    
    Dan
    

    Since I don't have the time to read all of the notes in this section,
    I'll just say my piece and see what kind of response I get.
    
    1. The Electra is an excellent introduction to electrics.  I built
    mine and flew it right off the building board to many successful
    flights (but bought the farm due to a failure of one of the rudder
    hinges)
    
    2. Cobalts are vastly superior to ferrite motors both in their ability
    to do work, and because of the higher quality construction, their
    ability to withstand heat (which is important when turning a larger
    prop)
    
    3.  motor/battery ventilation is only improtant if you are going
    to fly successive flights on the same motor/battery without allowing
    any cooldown (I find it is best to vent the motor, and switch packs
    every flight)
    
    4.  Pulse speed controllers due not harm the motor in any way, and
    make more efficient use of the critical resource (batter power) than
    resitive controllers.
    
    5.  the ASTRO-SPORT with an ASTRO-05 is a very fast aerobatic plane,
    much like the WASPS i've seen, only faster.
    
    6.  Although I have yet to fly it, the Great-Planes electiCub promises
    to be a good electric flyer.
    
    7.  SANYO has announced, and is shipping in limited quantity, their
    new SCE series batteries.  the 1200MAH SC SUB-C cell is now available
    as a 1700MAH SCE SUB-C cell with the same weight as a 1200, and a slightly
    higher internal resistance. static tests on the ground with an astro-05
    turning a cox 6-4 yields almost a 9 minute run before loss of rpm,
    this is up from a little better than 6 minutes with 1200MAH cells.
    Sanyo also has a 1000MAH cell in the SUB-A size, which would be
    excellent for 035/020 sized electrics (and maybe even 05 electrics,
    since they weigh in at slightly more than 1/2 a SUBC, but are not
    really all that lower in power than a 1200)
    
    8.  I am interested in hearing about motor/plane/battery combos
    that others have tried out, success or failure.  It is important
    to describe overall weight, wingspan/chord/thickness/airfoil, motor
    size and manufacturer, prop size and manufacturer, battery size
    (AH and # of cells), on the ground motor duration, and in the air
    motor duration. electric flight seems to be emprical right now,
    but given enough info, it can be distilled to a science.
    
                                                                   

    Boy!! A couple of weeks out of the office and it takes another 2 weeks
    to catch up!! This is some popular notes file!
    
    Glad to see more interest in electrics in the notes file. So far
    however, I've only seen Cobalt 035 and 05 motors mentioned. Recently, a
    shop in the UK has started to stock 10 and 15 size motors (priced and
    EXPENSIVE!) and they say they have bigger (up to 60 size) cobalts in
    stock (not priced, I guess the danger of heart failure due to cost
    isn't worth the risk of advertising it :-}). Anyway, has anyone
    used/seen any of these bigger motors and if so is there anything
    special to using them (e.g. what sort of cabling does one use, how many
    cells etc etc). 
    
    Keith. 

    Kyosho is now claiming that their DUET dual-motored 6-cell electric
    is capable of full aerobatics, including climbing straight up.
    
    Does anyone either have this plane or know someone who does?  Is
    it any good, or just hype?
    	
    	-thinkin-about-a-plane-Bill
    

My Watts Up with an Astro .035 should be ready for flying this
weekend.  I bashed this one up last year trying to learn, now
that I can control a model, I shouldn't have as much trouble
flying it.  I'm putting a charge into the 5-cell 800 mA motor
battery pack today.

This evening or tomorrow I will cover the portions of the wing
that were fixed.  The only thing that will mess me up will be the
wind; I'm hoping for a light wind for the first flights to allow
me to get to altitude for trimming. 

I'm using a Tower micro system in the model for rudder, elevator,
and motor on/off.  The motor control is with a microswitch on a
dedicated servo in the usual manner. 

Since I have not had the pleasure of flying an electric for over
30 seconds, I'm looking forward to the experience.

I believe the Astro .035 ferrite is less powerful than either the
.05 you mentioned or its equivalent Mabuchi 540.  The discussion
we had earlier about comparing motors by wattage rather than
equivalent engine sizes is relevant there.  I think that we'll be
seeing wattage as a criterion in the future.  The european
motors, like the Keller, are rated on wattage, though I forget how
the name translates into power.

I think that the prop is a large factor in performance.  I
have an article by Pappy DeBolt from, I think, Model Builder on
how to modify props for better performance.  Let me know if you
want a copy.   Its possible that the model you saw is just fitted
with the wrong prop. 

    My two cents worth about motor ratings :
    
    The "SIZE" of an electric is a good method for comparing relative
    power output (an 035 is definately less powerful that an 05) but
    the distinction blurs if you match cobalts to ferrites.  an 035
    coblat produces about the same power in watts as a typical 540 (05)
    ferrite motor.  If you order a cobalt from ASTRO, they will (or
    used to) send you a little "poop" sheet on their motors, which included
    power ratings in watts for the entire family.  ASTRO produces an
    020, 035, 05, FAI 05, 15, 25, 40, and 60 size cobalt motor, and
    similar ratings in ferrites.  The FAI 05 is a motor wound for speed,
    and it produces the same power output as their 15 cobalt, but runs
    on half the cells (and obviously half the duration).
    
    Re the comment on a poor performance electra :  my experience with
    this plane was that it had pretty good performace.  One factor that
    was very important though was batteries.  At the time I first flew
    the electra I had a couple of packs from my cars, which I used.
    two of the packs were TAMIYA, which use the SANYO cells, one pack
    was a "bogus" brand that used some unknown cell.  The electra flew
    great with the TAMIYA packs, but barely stayed in the AIR with the
    cheepo brand.  Many non-electrically minded people would not know
    to look for performace degradation due to bad batteries, and would
    instead chalk a poor flight up to "bad charge" or something.  Batteries
    are probably the most significant factor in successful electric
    flight.
    
    Re Props :  I flew my Etude with a wooden topflight 9-8, and it
    did just fine.  since I invariably broke a prop when landing, this
    was a very economical solution to anotherwise expensive "prop"osition.
    
    I typically choose a prop for an electric by performing a static
    duration test.  hold the plane down and run the motor full throttle
    with the chosen prop, timing the run.  If you don't like the duration,
    try the next lower pitch or diameter until you do like the duration.
    I have found that my planes won't fly on any prop that gives them
    more that a 5 minute static duration (the duration goes up some
    when the plane is flying, since the prop "unloads" some in the air).
    
    that all folks...
    

    as i recall, i found the props at Henrys Hobby House on front street
    in worcester, but I really don't recall anything other than the
    fact that they were 9-8s, and topflight, and they seemed to work
    just fineon the etude.  sounds like you had a lot more success with
    your etude than i had with mine.  currently the wing is resting
    on the modified fuse of an astro-sport ( are you interested in a
    spare etude fuse ? ), which when complete will be 4 channel with
    a cobalt 05.  If you havent flown with a cobalyt, i strongly reccomend
    trying one, the difference is really quite amazing.
    
    on the electra subject, as i said, my electra had a fairly good
    rate of climb, and could easily attain altitudes well above your
    typicall high-start two and sometimes 3 times on a charge, with
    flights lasting as long a 30 minutes (which is about my duration
    tolerance).  On good flights, I always ended up bringing it down
    intentionally so that i could take a rest.  I liked it *SNIFF* a
    lot, but its dead now.....
    

Dan, I've had more luck with a microswitch on the on-off servo.
I CYA'd the switch to the side of the servo.  Haven't flown the
Watts Up yet, we've been getting some windy days here, and I want
it dead calm or nearly so for the first flights. 

    dan,
    I purchased one of the astro speed controllers from tower for around
    $50.00.  This was an FET style PWM motor controller.  It does *NOT*
    provide dynamic braking.  It is a very simple unit based on the
    National Semiconductor servo controller chip (I forget the number
    at the moment).  Although It worked well, I did have a problem with
    it.  This problem was that full throw on my transmitter throttle
    stick did not provide "Full off" to "Full on" at the motor.  I could
    adjust the controller (It has a trim pot) so that off throttle on
    the xmitter was "off" at the motor, only to find that full on at
    the throttle stick was not full on at the motor, or adjust the
    controller so that full on at the xmitter did provide full on at
    the motor, only to find that full off at the xmitter had the motor
    still powered at the controller.  I called Astro, and they refered
    me to the guy who designed the controller.  He said that the japanese
    radios (in this case a conquest 4-ch) are often very "sloppy" in
    the adjustment of the transmitter channel nuetral points and other
    "things", and that his design was not as forgiving as a mechanical
    servo.  He suggested I adjust a feedback resistor in the controller,
    which I did, but this did not have the deisred effect.  Ultimately,
    I traced the controller circuit, drew a schematic, and found what
    I needed to adjust to increase the control "range" of the circuit.
    Now it works fine.
                      

    Dan,
    
    I recently bought a catalogue from one of the bigger Electric Flight
    suppliers here in the UK called MOLE TECHNOLOGY. They sell a small
    electric flight switch which replaces a servo and I belive provides
    dynamic braking. The switch sells for something like �16.00 in the
    UK. This might be what you're looking for. Let me know if you want
    some more details.
    
    Keith.

    Dan,
    	I'm not an electric plane expert, but I do know a bit about
    DC motors and their characteristics.  A given motor wants to see
    a fixed load on it for best performance.  Too much load and you
    draw too much current and it turns slow - hard on motor, battery,
    and switch.  Too little load and it will generate less useful
    power and turn faster than it is designed to do.  A gear reduction
    unit can match a High RPM motor to a larger, more efficient prop.
    The gear reduction unit will have some losses, though.  Another
    advantage of a gear reduction unit is shaft size.  It is easy to
    bend the shaft on many direct drive motors in a crash.  The motors
    with small shafts are not designed to take the side loads that
    occur when the prop hits the ground.  High speed motors tend to
    be smaller in size than lower speed ones.  They tend to be lighter
    as well.
    
    Charlie
    

    Dan,
    	Randy here, I was the one at the fly-in that was so interested
    in your electrics.  I agree with Charlie about the advantages of
    a gear drive.  One consideration though, the Astro flight 05 electric
    motor (cobalt that is) has an output shaft that is close to 2/10
    of an inch thick.  this is substantially larger than the typical
    05 "can" motor you are familiar with, and my feeling (since I haven't
    actually had the opportunity to discover empirically) is that it
    would take a fairly substantial smash-up to harm the output shaft.
    Also, Astro gear drives are all aluminum, and the output shaft of
    these are standard .25 inch shafts like you see on a typical gas
    motor.  Astro motors are built very rugged, with all aluminum bell
    housings that are turned from a solid piece of stock, rather than
    stamped like most cheap 05s.  If you are looking for a new motor
    to buy, I would highly recommed the Astro motors as a solid investment.
    Sure, they are much more expensive that ferrite motors, but they
    WILL LAST much longer than something like a Kyosho Le Mans motor,
    and have a much higher survivability.  Also, a nice feature of Astro
    motors is that if your wreck one, you can send it back to Astro
    and they will rebuild it for you.  They say the cost of rebuilding
    is guarnateed not to exceed 75% of the original cost of the motor
    (or some such figure like that, I don't remember exactly right now),
    since the highest cost item in a Cobalt motor is the Magnets, and
    they are virtually indestructable.  If you decide to go the Cobalt
    route, I recommend you buy a 15, instead of an 05.  The 15 is only
    about 1 once heavier than the 05, and only slightly larger in diameter,
    it will turn a prop at about the same speed (on 6 cells) as an 05 will 
    on 6 cells, and the advantage is that you can use two 6 cell packs in 
    series with the 15 and fly a much larger plane, if you decide to
    step up to larger aircraft.  Also, Astro motors have brushes that
    are over twice the size (and therfore contact area) of something
    like a Le Mans, allowing these motors to pull much higher currents
    (and therefore turn mmuch larger props at higher speeds), and the
    brushes can be replaced without dissasembling the motor.  Astro
    motors also have the armature suspended in ball bearings, they are
    run in at the factory for at least an hour before you get them,
    and they are optimally "timed" when bench checked.  I think that
    if you plan to continue in electrics (which is seems you do) your
    best bet is a Cobalt, since in performance, quality, and durability
    they are considerably superior to typical ferrite motors.

    re -.77
    
    I believe that Tower Hobbies has several prop adapters available
    ( as part of their Graupner,etc offering).
    
    Also, there's a guy locally that builds sailplanes and also mills
    a prop adapter out of aluminum stock (approx $5.00).  Let me know
    if you need his name/#.

    post the name here so that others can reference it without having
    to explicitly call you.  Also, I recommend the Master Airscrew 05
    prop adapter, I use it on "can" 05s, and a drilled out version (for
    the larger armature shaft) on my cobolt

                  <<< IOALOT::DUA1:[NOTES$LIBRARY]RC.NOTE;2 >>>
                  -< Welcome to the Radio Control conference >-
================================================================================
Note 387.84                   Beginners ELECTRICS?                      84 of 84
MJOVAX::BENSON "__Frank Benson, DTN 348-2244__"      13 lines  15-APR-1988 15:55
                           -< Another Great Source! >-
--------------------------------------------------------------------------------

    Prop Adapter Source:
    
    The Institute of Silent Flight
    Elliott J.W. Boulous
    P.O. Box 430
    Morgantown, PA 19543
    717-286-5129
    
    Also, Elliott is known locally as a builder SUPREME.  He specializes
    in Bob Martin Pussycats but will build to your requests.  I bought
    my Pussycat from him for $100 beautifully finished and ready for
    my radio.  It is built like a truck!!! While learning Hi-Start,
    I nosed in HARD twice and did little/no damage.   Give him a call!
    
                             |                      
   \	       	         ____|____                      /   Regards,
    \________________________O_________________________/    Frank.
    

    Hey, I flew my new electric design on tuesday, it went great ! 
    Its a mmodified Electra.  Wing span increased 8 inches for a total
    size of 86 inches, V-tail, and a geared 550 size motor (about 3:1
    ratio) turning a master airscrew 12-8, tached at about 4000 RPM,
    with a 6 cell 1200 MAH pack.  The wind was steady at about 15MPH,
    gusting higher, so when the plane was released it went up like it
    was in an elevator, little or no foward motion but a really excellent
    rate of climb.  Id'e have to say that the geared motor pulls the
    plane much better than the stock 550 direct drive did on my ealier
    Electra.  This is the first time I've really flown a plane with
    both gear and direct drive, and I've been convinced.  If your not
    interested in speed, but you do want the security of a decent rate
    of climb, gearing the the best way to go.

    
    What kind of flight duration did you get per charge?
    
    Bill
    

    geeze, Bill, you could just walk over to my office to ask, if you
    like, its not like I'm much more than 75 feet away...  But anyways,
    in answer to your question... When I flew, I did not put a full
    charge on the battery, since both Dave and Charlie were at the field,
    and they were giving me a real load of SH*T about how long it was
    taking to charge, and why didn't I charge up the night before. 
    I launched and ran the motor for about 2.5 minutes before I shut
    down and glided a bit, when I got down wind I powered up and flew
    back.  Did this a couple of times before I landed (it was so windy,
    I was sure I would wreck on landing, so I wanted to savor every
    minute of flight)  there was still a decent charge on the battery
    after I came down.  Static (not flying) motor duration is not accurate,
    since the motor "unloads" some when the plane is moving, but on
    the ground I can turn the prop at about 4 grand for 5 to 5.5 minutes.
    last year, I found I generally got another 2 minutes of useful power
    once I was airborn (but this was on a different motor/prop/airplane).
    Of course, I do have a 1700MAH pack of the new Sanyo SCE cells,
    and these should give me a 40% increase, the above mentioned flight
    was with 1200MAH cells.  

    One of the current model mags (can't remember which one) has as
    its cover story an electic powered B36.  Details (from memory)
    include 6 Astro 05 cobalt motors, 42 cells, weight just under 18
    pounds (!) and 7 channel control.  Some really neat pictures of
    this thing on the ground and in the air.  Typical flights seem to
    be on the order of 5-6 minutes.  Interesting form of motor control:
    servo moves stepping switch to turn on motors in pairs, e.i. you
    can have 2, 4 or all 6 motors on for a degree of power control.  
    Article includes picture during construction.  It says they (mother
    and son team?) did a great deal of research and then built the 
    plane in less than two months from first cut to first flight.
    It's this kind of nut which makes this hobby worthwhile!
    
    Kevin C.
    
    P.S.  I lent out the mag and when I get it back I'll enter any 
          corrections or details that I missed.
    

Somehow the thought of a quiet B-36 seems foreign to me.  When I
was a kid we lived on the final approach to Oakland Calif
airport.  The B-36s there used to shoot landings in case of
emergency.  I can tell you that when that baby came over, all six
engines droning (and maybe the wingtip jet engines too) it was
anything but silent!  The only other thing that was as noisy was
when the R3Y Tradewind, the last of the large flying boats, with
four (or maybe six) countra-rotating prop turbines came into
Alameda -- along a similar approach path. 

The Nacarros (sp?), Addie and Tony have long pioneered in unusual
modelling applications, such as control-line electric.  I assume
that they are the mother-son team you are talking about -- an
electric B36 is right up their alley.

    It was last month's Model Builder magazine which is now called
    "Model Airplane Builder" to be more clear about their contents.
    I have the issue.
    
    Glenn

    RE: .90-.92
    
    Just recovered my magazine.  It is indeed the May issue of Model
    Aircraft Builder and the B36 was indeed built by Addie and Tony
    Naccarato of T & A's Hobby Lobby.  By the way, the beast in question
    has a wingspan of 112-1/2 inches.
    
    Kevin C.
    

    
    
    I just got the mag last night.  It is RC Scale Modeler last month
    (MAY).  The dealer was throwing it out and I took it home.
    

    The current (June, I guess) issue of Scale R/C Modeler has the debut
    article of a new R/C electric-scale column authored by Tony and
    Addie Naccaratto.  The Naccarattos' electric B-36 is featured in
    yet another photo and Tony describes the test-flight in the text.    

      |
      | |      00	 Adios,      Al
    |_|_|      ( >o
      |    Z__(O_\_	(The Desert Rat)

    Well, last week I promised I'd tell y'all about my new
    Electrostreak so, here it goes...  (rather long winded and probably
    should be considered a "ramblin' note"...  The "executive summary"
    is that it flies great and might be a good enough performer to get
    even Charlie Watt and Bill Lewis into electric.  ;-)

    First of all, for those of you that may not get "Model Aviation" (or
    don't have/remember the November 1987 edition) - a quick run down on
    what an Electrostreak is (and isn't).  

    The Electrostreak is: an aerobatic electric that is a shoulder wing
    design and the outline looks similar to modern pattern planes.  It
    has a 44 inch wingspan with a symmetrical airfoil, is about 39 (?)
    inches long, and has no landing gear (to reduce weight and drag). 
    It is designed to use one of the popular direct drive "05" type of
    electric motors from Leisure on 6 cells or (for better performance)
    an Astro Cobalt 05 on 7 cells.  The plans state the weight should be
    32 to 38 ounces.  Ready to fly, mine weighs 39 ounces.

    The Electrostreak is NOT: a beginner's plane!!

    Building the Electrostreak:  As far as I know, the plane is not
    available in kit form (although I hope it will be someday) and must
    be scratch built from plans (Nov. 1987 Model Aviation).  Building
    goes along pretty much as the designer's article says and took me
    about 1.5 months.  There were only 3 problem areas that I was able
    to figure out fairly easily:  

    1)  On the plans, the aileron servo mounting scheme was not
        specified and in fact, some of the pieces in the center need
        to be modified to put the servo in there - no biggie if
        you've built a few aileron wings before.  (Even if they've
        all been from a kit.)

    2)  The front former of the fuselage (I think it's called "F0")
        should be modified if you are using an Astro Cobalt 05 (as I
        have).  Otherwise, the motor brush holders would hit on the
        piece of triangle stock in the upper left corner of the
        fuselage.  Basically, think this out BEFORE you cut F0 and
        rotate the motor 45 degrees counter-clockwise (from the
        front view).  This requires that the center cut-out of F0 be
        modified and the mounting holes moved.  This would not be
        mandatory but I recommend it.  

    3)  Despite the designer's good attempts at ensuring proper down
        and right thrust (2 degrees each), I still managed to mess up
        the down thrust.  Mine came out to 0 degrees.  My solution
        (hack) was to slot the motor mounting holes and put a couple
        of washers behind the lower hole.  Now I have (about) 2
        degrees of down thrust.  Next time, I'll make _SURE_ that I
        align F0 _AND_ F1 correctly in the vertical direction relative
        to the fuselage bottom (which is where I went wrong).

    In addition to these points, I made a list of notes to myself
    about things I'll make sure I remember to do next time (or do
    differently).  I won't bore you with any more details except that
    I think the bottom sheeting of the fuselage under the wing area
    should be replaced with 1/16 inch plywood instead of balsa.  This
    is needed because of the extra weight (and stress) that the motor
    battery puts on this area.

    By now you're saying:  "Gee Dan, when are you going to shut up
    about building and tell us how it _FLIES_?!?!?"

    I finished it late Sunday night last week and woke up Monday to a
    perfect test flight day:  _NO_ wind and overcast (yes, overcast is
    good - no one else will show up at the field).  So at about 8 AM I
    hand-launched the Electrostreak for it's maiden flight.  It flew
    beautifully and required no trim.  In one circle around the field,
    I was quickly up to about 300 feet and decided it was time to see
    what she could do.  (Yeah, I know I, _should_ have flew it straight
    and level for a while first - I just couldn't resist...  ;-)  

    So, I went for the simplest maneuver; a loop.  Just after it pulled
    up (1/4 of the way around) I heard this loud "RIP" and then the
    sound of a long streamer of Ultracote flapping in the breeze.  This
    is a VERY bad thing to hear on a maiden flight...  I finished the
    loop, quickly cut the throttle (electronic speed control), and began
    to set up for a landing.  Much to my surprise, it still flew OK and
    I began to suspect a piece of the fuselage covering had come off. 
    Although I couldn't tell from this angle, it was actually a piece of
    the covering from the top of the right wing...  (Please insert your
    favorite suspenseful music here ...)

    Since I'm used to landing dead-stick on every landing (from my COX
    .049 plane), I have a tendency to just put the plane down wherever
    seems easiest.  Well, this landing approach wasn't the best - I was
    bound to crash land in the dug up dirt area in the middle of our
    field where they're doing some field repair (CRRC club).  I had
    intended to land in the deep grass at the edge of the field
    (remember - no landing gear).  Just as I was about 3 feet above the
    rough dirt and resigned to go pick up many little pieces of balsa, I
    remembered "Hey wait a minute dummy - this isn't a dead stick
    landing - this is an electric and I've used only about 1 minute of
    run time!!  Let's add power and go around!!"  So I did.  Second
    approach was OK but too high.  Add power and go around again.  All
    the time with this very loud flapping of the Ultracote streamer. 
    Third approach was perfect and a nice landing followed.  When my
    knees stopped shaking enough to allow me to walk again, I walked
    over to the plane to assess the damages: a broken wooden prop
    (expected on most landings without landing gear) and the Ultracote
    streamer from the wing.

    Now, you're probably wondering "If the covering was torn off the
    wing, how come this didn't effect the flight characteristics?" 

    Well, I'm not sure which 4 leaf clover I stepped on but, I sure got
    lucky.  The covering only came off the leading third of the wing and
    this area is sheeted with balsa.  So, other than a little extra drag
    pulling from the center of the wing, the plane was aerodynamically
    intact.  The "excited little boy" part of my mind was telling me to
    cut off the streamer and fly it again...  Fortunately, sensibility
    prevailed and I packed up to go home (and then to work).

    As I got into my car and began to drive home, I began to remember
    making a mental note to myself the night before... "The covering on
    the leading edges of the wings aren't tacked down very well and
    should be sealed with the iron again before you fly".  

    The moral is: ALWAYS WRITE DOWN THOSE "LAST LITTLE THINGS" AND MAKE
    SURE YOU CHECK (THEN RE-CHECK) ALL OF THE ITEMS BEFORE FLYING!!!!  I
    know this has been said many times before in this notes file but,
    not enough times for dummy-me.

    So, at lunch time, I went home from work and re-covered the bare
    area.  Then, I went over every seam on the plane with the iron set
    on high.  In addition, on the leading edge of the wing, I added a
    strip of 1/4" striping tape to make sure that wouldn't come loose
    again.

    I guess I should comment on the color scheme: the wings are all
    yellow with the exception of the sheeted area on the top 1/3 of the
    leading edge which is orange (this is the piece that came off). 
    This makes it easy to keep track of top/bottom in rolls, etc.  The
    tail is done similarly to the wings.  The fuselage is red.  It might
    sound ugly here but I think it's quite sharp (and others think so
    too).

    Enough of that blabbing - back to how it flies.  After work that
    same day, the weather was the same as it was in the morning: no wind
    and overcast.  So, back to the flying field.  This time I got in 3
    great flights and 2 great landings.  The Electrostreak is _VERY_
    aerobatic and beautifully performs all of the maneuvers that I'm
    capable of so far: loops, slow rolls, snap rolls, stall turns and
    sometimes I do a nice Immelmann or split-S.  (Not really much to
    brag about - YET!  Pattern competitions - beware!!)

    When I'm flying full throttle all the time, the batteries last for
    about 4 to 4.5 minutes before they start slowing down.  One of the
    flights, I decided to go for maximum flight duration - climb, glide,
    repeat (no aerobatics).  There was no lift in the area and I was
    able to stay up for about 7.5 to 8 minutes.  

    The third (last) landing wasn't so nice.  I did not set up for the
    landing too well (I would have had to walk too far!!) and tried to
    go around.  However the batteries couldn't do it.  "Scotty we need
    more power!!"  "Capt'n ah' can't change the laws of physics..." 
    Thus, I crashed in the dirt I mentioned earlier.  I'm still kicking
    myself - I could have landed safely on my first set-up - I was just
    trying to be "precise" in landing.  Next time "safe" comes before
    "precise".

    The fuselage was cracked just in front of the horizontal stab, which
    had hit one of the little piles of dirt.  All 3 landings of the
    evening broke a wooden prop.  I decided it was time to mount the 7-4
    folding prop I bought from K&W Enterprises.

    That night, I repaired the damages and beefed up the area with a
    little carbon fiber and Slo-ZAP.  However, the folding prop couldn't
    go on right away - the screw that comes with the Astro Cobalt 05 is
    a little too short to reach through the (thicker) hub of the folding
    prop.  I needed to find a longer screw.  

    I used a Top Flight 7-4 "Super-M" maple prop on all of the first 4
    flights.  The designer recommends a 7-5 or 7-6.  So I decided to
    give a wooden Zinger 7-5 a try.  The next day was nice and I took
    the Electrostreak to the field at lunch time.  The difference in
    performance with the 7-5 was _INCREDIBLE_.  It now climbed at least
    twice as fast (about a 30 degree angle) and was noticeably better in
    many of the maneuvers.  It really performed like some of the average
    to "hot" gas powered planes - honest!!  I was having too much fun to
    time the flight.  I hope (but don't expect) the 7-4 folding prop
    will perform as well.  

    On the landing, I wasn't quite level and did a "spin around" when
    the wingtip hit first.  The elevator took a hit from behind and the
    fuselage cracked in nearly the same place again.  (The carbon fiber
    held - the wood around it broke...sigh.)  At first, I was excited
    because the blades on the Zinger prop are thicker and didn't break. 
    Later that night, (at the CRRC club meeting) I found out this was
    NOT good.  The motor shaft was bent and needed to be sent back to
    Astro Flight for replacement.  (Arrgh!!)

    So, later this week (or early next week) I'll get the motor back and
    will be in operation again.  I've mail ordered a bunch of new props
    (_NOT_ ZINGERS) in the 7-4, 7-5, 7-6 range so I can do a good study
    of prop performance vs. run time.  I also have a longer screw for
    the folding prop.  I'll let you know (in a MUCH shorter message) how
    it goes.

    (Oh dear - 212 lines - this must be a record for ramblin'  :-)

                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|            Happy Landings!
     |_/      |___________|  |_________|  |
                      |       /           |
                      |      /                           - Dan Miner
                      |_____/

    Dan,
    	Congrats on your success with the Electrostreak!  Bill L. and
    I are indeed interested in trying out this bird.  We are about to
    order plans and electric equipment.  I don't think that I will get
    one built this summer, but I may get started.  What kind of servos
    did you use?  Did you run the radio off of the motor battery or
    do you also have a radio battery in the plane?  Sounds like it would
    be worth while developing a way to get the prop to stop horizontal
    to minimize breakage and shaft bending.  Maybe the folding prop
    would solve this problem.  It doesn't sound like fun to have to
    replace the prop after every landing.
    
    Again, It's great to hear of your success!
    
    Charlie
    

    dan, i enjoyed your story.  i too have been amazed how well a plane
    will fly with half the monocote ripped off a wing.  if it werent
    for the "bent shaft" problem i'd say nylon props are sturdier and
    would break less frequently than wood.  maybe you can make some
    kind of skid to help, like a piece of wire sticking down behind
    the prop with no wheel...
    having no landing gear is neat; light and looks excellent in the
    air.
    was this the black plane on the cover of ma?  i'm not sure if i
    remember the electrostreak or not.
    congrats,
    kevin

    I would strongly caution anyone flying electric against using
    "sturdier" props to elimitate breakage.  As anyone with a little
    electric experience knows (probably just myself and Dan Snow), the
    most sensitive spot on any 05 powered electric is the armature shaft.
    When you have a gear drive (like a Kyosho has), it is invariably
    the spur gear shaft that bends.  When I was (unsuccessfully) flying
    my Kyosho Etude, I broke a bunch of the 9-8 Kyosho props before
    I found some Topflight wooden 9-8s.  the first time I flew with
    one, I bent the gear shaft on landing.  My solution (picked up from
    an electric column in a magazine) was to notch the blade at the
    hub with a hole saw, so that when a blade hit the ground, it would
    break easily.  The lower rpms of electric powerplants do not stress
    the prop enough to have to worry about throwing a blade.  recently,
    I saw an article on electrics from 1984, that reccomended a real
    good means of preventing prop/motor damage.  Basically, on on/off
    only motor control systems that used a servo to actuate a switch,
    a piece of piano wire was attached to the servo arm and extended
    out the front of the plane.  When the servo was actuated a little,
    it moved enough to throw the switch and stop the motor.  if the
    servo was sent to the far travel limit, though, the piano wire going
    to the front of the plane extended far enough out of the nose to
    interrupt the prop and so stop it horizontally.  Motor shafts are
    a big problem with electrics that have no landing gear.  My electric
    glider uses a MasterAirscrew 12-8 folder, which is the only means
    I know of, other than those listed above, to protect the motor.
    Unfortunately, folders are only available in very limited sizes,
    and in electric flight it is important to be able to match the prop
    to the plane for the best efficiency/motor duration/performance.
    
    Oh, one other suggestion.  On electronic speed controls that provide
    a "brake" function, sometimes it is possible to "blip" the throttle
    to get the prop horizontal, but this is a method that leaves something
    to be desired, because the results are pretty much a matter of luck.

    Brainstorm!!!  Brainstorm!!!   CHEAP!!!!   EASY!!!   UGLY!!!
    
    Go to Radio Shack and pick up a pair of their cheap little magnets,
    the ones that look like large aspirin pills.  Now, make from flat
    steel (tin can is thick enough) a little bar with a hole in the
    middle, said hole big enough for prop shaft, said bar about 3/8"
    by 1.5", hole in the middle.
    
    Mount the bar behind the prop, _right_ behind the prop.  You should
    bend the flats to sort-of follow the prop profile line.
    
    Get out the 5-minute epoxy and microballoons.  Epoxy those two little
    aspirin-magnets to the front cowl so that the steel bar just clears
    them (say, by .005") when the propshaft is not under tension (like
    when the prop is not pulling the ship aloft).  When the aircraft
    is "hanging from the prop" the propshaft play will pull the shaft
    out significantly further, like .1 inch or so.
    
    Now, you notice that when there's slipstream on the prop, it tends
    to windmill.  That, plus the inherent propshaft play, is the key
    to the system.  When power's on, the magnets aren't close enough
    to have any real effect (even if they did, the effect is to alternately
    slow down and speed up the prop- no net change).
    
    When you switch off, the propeller slows down, moves back, and
    windmills to a stop, or near-stop.  Well, the magnets now have enough
    proximity and power to grab and hold that prop in whatever position
    the magnets catch it.  (you can tweak it by tweaking the bar-prop
    angle.)
    	
    When the motor switches on again, it pulls the bar from the magnets
    and away you go.  Switch off again, magnets pull the bar and prop
    into landing configuration again.
    
    Jus' dont put it into the ground with the motor on full, OK?
                       
    -----
    
    Another alternative if you don't want to uglify your cowl: 
    epoxy the bar (or a piece of paper-clip) to the tail end of the
    motor or gearbox propshaft.  Install aspirin magnet(s) the same
    way.  Now you've created a magic motor that always stops the same
    way...
    
    	-Bill

RE: .113 ? (Charlie Watt)

    When the Electrostreak is back in commission, I'll send you guys mail
    and maybe we can meet at the CMRCM field some lunch time or after
    work.  I'd really like to see what this plane can do in the hands of
    a GOOD pilot.  :-)  

    As the author recommended, I used Futaba microservos for rudder,
    elevator, and ailerons.  There is _NO_ room for anything larger.  My
    receiver is not the 4 channel micro Rx that he recommended - it is
    the standard Conquest 4 channel Rx (larger and heavier) and just
    barely fits (this is part of the reason mine came out slightly
    heavy).  I use a home-built forward only speed controller with no
    braking.  (Charlie, the following is not an attack on you, I'm
    putting it in big letters for anyone else who reads this.)

    ********************************************************************
    NO, I DO NOT USE THE MOTOR BATTERY FOR THE RECEIVER ALSO.  THIS IS
    VERY DANGEROUS AND SHOULD NOT BE DONE FOR AN AIRPLANE UNDER ANY
    CIRCUMSTANCES!!!     (I use a 300 mAh Rx pack for the receiver.)
    ********************************************************************

    Typically, what happens during a flight is you get so involved with
    having fun that you don't realize the motor battery is getting low
    until it's almost dead.  If you were powering your Rx from this, you
    might as well turn off your Tx in mid-air.

    I just called Astro to check the status of my motor.  They said they
    got it Monday and it was scheduled to be worked on this Friday.  I
    should get it back sometime late next week.  :-(  Gee, I guess lots
    of people are putting Zinger props on their Cobalt 05's.  

    I should have gone with my instinct last Saturday when I phoned in
    an order to Tower and just got another motor (that way, I could be
    flying by THIS Friday and when my first motor came back from Astro,
    I'd have an excuse to build another Electrostreak. :-)  Well, I
    guess I can wait another week - I don't think I'll die from lack of
    flying even though it feels that way some times...  :-)

RE: .114 (Kevin Ladd)

    Yeah, the nylon props don't break (at least as often) but I didn't
    have any of the correct diameter / pitch.  I am going to order some
    Taipan nylon props which were recommended by the designer.  (Does
    anyone know where to buy them here in Eastern Mass.?)  My experience
    with nylon props on my last plane (Astro Sport w/ Leisure LT-05) was
    that they flexed enough to NOT bend the shaft.  The added bonus was
    that the prop didn't break.  Note that I'm talking about the ones
    that are easy to bend by hand (COX) not the hard-as-rock ones like
    Master Airscrew.

    The wire skid sounds like a good idea - I had thought of it while
    building but decided not to change too many things from the plans
    for the first try.  I might give it a try on the next fuselage I
    build (maybe in a few months).  I don't think it would be easy to
    retrofit the current fuselage and still have the wire stay on after
    each landing...

    The Electrostreak was not black and was not on a cover.  The cover
    of the Nov. 1987 issue of MA had a photo from some obscure,
    un-important event called the "1987 NATs".  :-)  The prototype
    Electrostreak was all red with a little bit of white trim on the
    wings and tail.  The article starts on page 24.

RE: .115  (Randy Cohen)

> I would strongly caution anyone flying electric against using
> "sturdier" props to elimitate breakage.  

    I agree.  When I put on the Zinger, I wasn't trying to prevent prop
    breakage with a sturdier prop - I knew that if the prop didn't
    break, the motor shaft would.  What I WAS trying to do was to
    increase the pitch to see the performance difference.  It just
    happened that the only 7-5 prop I had was a Zinger.  I actually
    didn't think too much about the thicker blades until it was too
    late.  From now on, I'm only going to use "thin" bladed props on my
    electrics.  If I have to use a thick bladed prop, I'll try the
    notching idea.  (Do NOT try this for gas engines...)

    The music wire from a servo sounds like a neat idea.  Unfortunately,
    I use an electronic speed control and I prefer it to an on-off servo
    control.  Having both would be too heavy.

    I think the best idea from all points of view is the folding prop. 
    The bad news is that I think a 7-5 or 7-6 prop will work best and as
    far as I know, a folding prop with this pitch doesn't exist.  (Mine
    is a 7-4.)  By the way, K&W Enterprises DOES have a large selection
    of folding props from 6 inches up to the 12 to 14 inch range (don't
    have the exact info here...)  They just don't have the pitch I'd
    like.  On the bright side, since blade shape is VERY important on an
    electric, the 7-4 folder MAY perform as good as the 7-5 Zinger
    "motor-shaft-bender-special".

> Oh, one other suggestion.  On electronic speed controls that provide
> a "brake" function, sometimes it is possible to "blip" the throttle
> to get the prop horizontal, but this is a method that leaves something
> to be desired, because the results are pretty much a matter of luck.

    As it turns out, I don't have braking on my speed controller, but
    the Astro Cobalt 05 has enough "compression" that it stops by itself
    anyway.  (The Electrostreak designer mentions this too.)  I have
    sometimes tried to "blip" the throttle but I'm usually too busy with
    aileron, rudder and elevator to give it much thought.  :-)

RE: .116  (Bill Yerazunis)

    Well, I give you an "A" for creativity.  However, I don't think it
    will work too well.  First of all, on motors where it's really needed
    (like my Leisure LT-05), I don't think your scheme would be strong
    enough to stop the prop.  In addition, if it were strong enough, you
    would be trying to "hold back" the prop when you're running the
    motor.  This would suck out enough % performance to make a difference.

------------------------------------------------------------------------------

    (Sorry for the long reply...  I just am so excited about my new
    "baby" that my fingers won't stop!!  :-)

                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|            Happy Landings!
     |_/      |___________|  |_________|  |
                      |       /           |
                      |      /                           - Dan Miner
                      |_____/

    I have most of the October '83 through September 84 MA, which contains
    a 10 part series on electric flight.  This is where the prop stop
    wire suggestion came from.  I am in the process of encapsulating
    these 10 articles, and when I'm done, I'll post it here.  A few
    things that I feel are the most significant aspects of electric,
    that I gained from these articles are...
    
    Weight.  The author claims, I and beleive him, that the power (in
    Watts, at the motor) needed to fly a plane increases with the square 
    of weight.  This means that fractions of an ounce can be significant
    in the construction of an electric. 
    
    Props/gear drive.  The object here is to fly using the motor/prop
    most efficiently.  This means that the prop size/motor speed
    combination should be matched to the typical flight speed of the
    plane so that the motor unloads as much as it can when the plane
    is flying straight and level.  Gear drives turning larger props
    at lower RPM are more efficient in big, slow planes, since the airspeed
    of the plane is closer to the speed of the air displaced by the
    prop, and the motor sees a lower "load".  Small fast props are better
    on smaller, faster airplanes, for the same reason.  There is a large
    variation is prop design from manufacturer to manufacturer, and
    this variation can have a huge effect on the performance of a plane.
    

    I've got an idea on this prop breakage/shaft bending problem. What is
    sounds like is needed is a shock mount for the prop. So how about
    reaming out the prop shaft hole to an appropriate size for a piece of
    rubber tubing or a rubber block, CA to rubber in place, and mount the
    whole mess with the motor shaft going through the rubber. In hard
    landings the rubber should deform rather than bending the shaft. Does
    it sound like it's worth trying?? 

                     !
                   --+--
G. Schrader     o___<0>___o
                  *  *  *

RE: < Note 387.119 by MAMIE::SCHRADER "Buddy can you Paradigm?" >

    HEY!!  That sounds like a _GREAT_ idea!!!  The thing I guess you
    should do is first find some tubing that has an inside diameter the
    same as the outside of your motor shaft.  Then, measure the outside
    of the tube and ream the prop to this diameter or slightly smaller
    so no glue is needed - just force fit the tube into the prop.  Then,
    balance the prop.

    I like it, I like it!!  OK, which hobby shop in central Mass. has
    the largest selection of fuel tubing?

    Dan to store owner:  "Hey, do you have any fuel tubing that will fit
    my Astro Cobalt 05?"

    Confused store owner: "Isn't the Astro an electric motor??"

    Wait a minute...  I just thought of a possible problem...  The prop
    gets tightened down to the thrust plate by a screw and washer.  This
    would keep the prop from moving and prevents the rubber tubing from
    doing any good.  So, to fix this problem, rubber should also be
    added in front and behind the prop.  (I guess that's what you were
    thinking of when you mentioned the rubber block.)

    Or, better yet is to use a piece of tubing that is longer than the
    prop is thick.  This way, the thrust plate and washer won't touch
    the prop but will compress the tubing and hold the prop.  An attempt
    at a diagram (side view cross section):


                    __   |  prop |
                      |  |       |
                thrust|  ---------  | <- washer
                 plate|/\---------/\| 
                    =================O <- screw
                      |\/---------\/| 
                      |  ---------  |
                    __|  |       |          
                         |  prop |               

           The:  "/\----/\
                  \/----\/"  is the fuel tubing squished on the ends

    

    I just realized my diagram isn't quite right.  Actually, part of the
    thrust plate normally goes inside the center of the prop.  So,
    imagine that there is a cylinder of metal around the screw but
    inside the fuel tubing...  The thrust plate itself looks something
    like:

                            ___
                           |   |    (Prop goes here)
                           |   | 
         Motor shaft goes  |   |______
                 in here ->     ______  <- Prop screw goes in here.
                           |   |
                           |   |
                           |___|

    
    Dan, that does it!  Charlie and I are gonna go for it.  I agree
    with separate receiver battery.  The microservos you used are S33s?
    I'd love to see it fly, meeting at CMRCM for lunch would be great.
    You mentioned a speed controller - is it just a switch or can you
    actually adjust motor speed?
    
    Bill

    gee, theres more activity here in the last week then there has been
    in the last 4 months !  Dan, you were a little tough on the rubber
    hose idea.  There is no progress without innovation.  I was thinking,
    though, and I beleive the best way to prevent shaft bending is to
    glue a really big pillow to the bottom of the plane.  this will
    also act as a shock absorber, allowing you to build your fuselage
    less strong (and so lighter).  Another alternative is to just catch
    the plane in your hand before it touches ground.
    
    On the subject on receiver batteries.  Remeber that an aerobatic
    electric is only in the air for a few minutes.  A 50Ma battery pack
    (SR sells them) for the reciever is more than sufficient for 20
    to 30 minutes of radio power.  This equates to 5 or 6 flights of
    the plane.  Between each flight you have to recharge the flight
    pack, this can take 15 to 20 minutes for a 1200Ma pack.  There is
    no reason why you can't be topping off the Rx battery too, at the
    same time.  My ElectriCub has a 100Ma battery for the Rx.  The weight
    savings is substantial.

    Dan,
    	I have seen car speed controls that shut off the motor when
    the battery sags to a voltage that is still higher than that required
    for the radio to function.  By the way, I agree with you that it
    is not a good idea to run the radio off of the motor battery, but
    it seems like it might be worth the weight savings to design a safe
    way to do it.  I also think that the prop breakage thing is totally
    unexecptable in the long run.  I'll ponder this problem and hopefully,
    either myself or someone else will come up with a satisfactory means
    of stopping the prop in the proper position without adding weight
    or complexity to the plane.  The magnet idea would not lower
    performance because it would average out over rotations.  However,
    it would add vibration as a new problem because it would be alternately
    pushing and pulling on the prop.  The end play in the shaft would
    not be enough to pull away from the magnets influence.  Maybe you
    could custom make a folder and adapt blades from a non-folding prop.
    
    Charlie
    

RE: < Note 387.122 by LEDS::LEWIS >

    Bill,

    Yes, the servos I used were the S33's.  My speed controller is a
    slight variation on one of the Jomar speed controllers (JC-1 ?) and
    is fully proportional.  The circuit was printed in some book on
    Electric Flight that a friend of mine has.  (I can't remember the
    name of the book right now...)  The only variations I made was to
    add an opto-isolator (to reduce possible interference with the Rx)
    and modify the MOSFET driver circuit.  It costs about $15 to $20 in
    parts.

    I'm planning to make a few circuit boards up (of the speed
    controller).  Does anyone have or know of a good way to expose the
    photo sensitive boards to UV?  Will an EPROM eraser work?

    When I get my motor back from Astro next week, I'll let you know
    and we'll fly at lunch time (weather permitting of course).

    I just got my order of "Rev-Up" brand wood props (7-5 and 7-6). 
    They have a very thin blade and look like they will always break
    if needed (instead of bending the motor shaft).  (YEAH!!)

                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|            Happy Landings!
     |_/      |___________|  |_________|  |
                      |       /           |
                      |      /                           - Dan Miner
                      |_____/

    I don't know about the safety aspects of custom-cutting a prop to be a
    folder, but jewelers saws are about the right kerf width to do it. 
    
    X-acto makes such a saw.  The kerf is only about .003" for their
    "extra-fine" blades.
    
    -----
    
    How to get a Little Extra Juice:
    	
    Carry a second battery in a droppable (with a parachute) belly pod.
    Get into the air and get some altitude on the belly battery, then "drop
    the tanks" when you want to dogfight.
    	
    		:-)   :-)   :-)                                       
    
    
		\__    		-Bill
	  {((___O===--0'         Yerazunis
    

RE: < Note 387.123 by LEDS::COHEN >

> gee, theres more activity here in the last week then there has been
> in the last 4 months !  
    That's what I'd hoped would happen!!

>                         Dan, you were a little tough on the rubber
> hose idea.  There is no progress without innovation. 
    Sorry, I didn't mean to be "tough" on the idea.  I think it's a 
    great idea.  I'll have to try the pillow on my next flight.  :-)
        (Have I just been taken hook, line, and sinker?? )  

                            - Dan Miner

    Dan,
    
    I've been thinking about my Pillow Idea.  Upon reflecting on
    suggestion, I have decided that it just wont work.  Sure, you save
    weight by lightening the structure, and prop breakagw would be
    eliminated, but the pillow itself adds weight (although you could
    use a helium filled inner tube type setup that actually reduces
    weight), and more importantly, the pillow adds drag that the electric
    motor just won't be able to overcome, ruining the high performance
    characteristics of the 'Streak.  I have a better suggestion, though,
    and it still uses the pillow (so you don't have to toss out the
    one I know you rushed out to buy when you read my last note).
    Basically, when the plane is on final, bring it in over your shoulder,
    as it passes you on the glide path, run along side it, and just
    before it touches ground, shove the pillow underneath it.  I'm sure,
    if you use this method, you will never break another prop or bend
    a motor shaft.
    
    If you are really concearned about bending the shaft again (and
    you should be, Astro doesn't fix the motors for free)  I seriously
    suggest that you "weaken" the prop by sawing a notch partway
    through the blade on either side of the hub.  The Astro doesn't
    spin the prop fast enough to worry about throwing a blade (RPM is
    probably below 12K), and this will ensure you don't damage the 05.
    Admittedly, it is sort of hard on the prop expenses, but it'll hold
    you until someone comes up with a better idea.

If you really don't want to break props why don't you land the same way
you take off - that is cheat.

Obviously your doing hand launches.
You could get one of these parachutes that they advertise
and deploy it for landings.  It might be fun and if you
think about it wouldn't look any stranger than hand launches.

Another suggestion is to add landing gear.  There are some light weight
foam wheels available now and somewhere I read about some
composite landing gear (looks like the dural aluminum but it is lighter).

Another suggestion is to add a landing skid.  Similar to what Dan Snow
had on the Pilgrim II but you could use a single wire on the fuselage
similar to seaplanes.

Now about that pillow - Just put it on the field and use it for a landing
spot zone.  Dive bomb the rascal.

Hand recovery is not unheard of either.  I've seen several folks snatch
gliders on landings (I've caught mine 2 or 3 times).  I've seen one 
guy land his Swizzle Stick by making a low pass and snatching the wing.
The engine WAS off!  If there is a decent breeze it is easy since
the ground speed is close to zero with light planes and gliders.  Last weekend
I watched a guy with a standard class glider skim over the runway straight
towards himself about 1 foot high.  Then he pulled up right in front
of his face and it stood on end and stalled.  Then he reached out and grabbed
the fuselage.  He was a very experienced flyer.

Bye          --+--
Kay R. Fisher  |
---------------O---------------
================================================================================

    Dan, the metal core and end plates were a nice touch. Another weird and
    crazy idea just hit me... How about taking a prop that you like and
    using it as a core to make a two piece mold. Then lay in some carbon
    fiber bundle or whatever works and squirt in a bunch of silicone rubber
    (RTV or Windsheild sealer or whatever). What you'd have is a limp prop
    that would just bend when it hit on landing. Under power the
    centrifugal force from the spinning would keep it flat (just like
    helicopter blades). What cha think?

                     !
                   --+--
G. Schrader     o___<0>___o
                  *  *  *

RE:< Note 387.130 by MAMIE::SCHRADER "Buddy can you Paradigm?" >

    Hmmm...  Sounds like it might work.  Making molds and such is to
    much work for me, though.  Although I agree about what you said
    regarding the centrifugal force, I wonder if the blades would be
    stable in the pitch direction.  In other words, would the blade
    "flutter" in pitch?  Anyone out there good at making molds to try
    this out?  I think the best idea (so far) is the rubber tubing idea
    and I'm going to try it.

    Keep up the good "brainstorming".  Yes, even the pillow idea showed
    some imagination.  :-)  In fact, I just thought of a similar idea
    that might actually work.  Use one of the CO2 cartridges and an
    inflatable pillow - an "air bag" for the plane!!  (OK, OK, so it's
    a silly idea too... :-)

    For those of you that have the July 1988 issue of Model Aviation,
    there is an interesting letter to the editor about the Electrostreak
    on page 6.  (Note:  This guy's 'Streak weighs 35 oz. w/ seven 800mAh
    cells - mine weighs 39 oz. w/ seven 1200mAh cells.)  There is also a
    nice chart (advertisement) showing the performance of Astro Cobalt
    motors on page 9.  (The 60 direct drive turns a 13-8 prop at 9000 RPM!)

RE: Note 387.128 LEDS::COHEN

    Although the idea of throwing the pillow under the plane at the last
    minute might just work, there is one major flaw in the plan:  The
    pilot (yours truly) isn't good enough to get the plane close enough
    to throw a pillow at it.  I guess I'll have to start improving my
    throwing arm!!  :-)  After all, I really don't have any other use
    for that new pillow I bought last night...  Oh, wait a minute - you
    said _RUN_ next to the plane and shove the pillow under it.  What
    does it mean to "run"?  :-)  (This is a _hobby_, not a _sport_!!)

    Seriously, you're right - Astro does not fix motors for free.  It's
    costing me $30 this time ( = $20. new armature + $10. labor).  One
    of the problems (for me) to cut the props as you suggested is that I
    don't have a hole saw.  Besides, I think the Rev-Up brand props will
    break just fine as they are.  The blades are MUCH thinner than on
    the Zingers.  If I bend the shaft with a Rev-Up, then I'll make it a
    rule to cut any prop and you can say "I told you so!"  

    BTW, according to the Astro info, the standard (7 turn) Cobalt 05
    turns a 7-4 prop at 14,500 RPM and the FAI (6 turn) Cobalt 05 turns
    a 7-6 at the same RPM.  (I have the 7 turn and don't have a tach. to
    check these numbers.)

RE: < Note 387.129 by K::FISHER "There's a whale in the groove!" >

    The parachute may work but I'm suspect of the size/weight/drag of 
    the little "parachute box".  Has anyone seen one of these?

    I plan to add a single wire skid to the next one I build.  I think
    the light weight wheels would be OK but would probably add too much
    drag.  The designer specifically mentions that he tried to add
    landing gear but took them off due to weight and drag.

    Catching an Electrostreak has two problems:
        1.  It flies (glides) a little too fast to try to catch.
        2.  Said pilot (me) isn't (yet) good enough to attempt this.
            (although maybe later in the summer...  :-)  

    I would also be concerned about bumping the throttle stick by
    accident just as I was about to catch it.  "Just call me lefty."
    Gliders do not equal electric planes.  :-)

                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|            Happy Landings!
     |_/      |___________|  |_________|  |
                      |       /           |
                      |      /                           - Dan Miner
                      |_____/

    
    RE: breaking props - how about a crude control circuit that takes
    over when the motor is turned off?  You probably still need to
    add something like a hall sensor to the shaft, but you could have
    a relatively low-power control circuit take over and control the motor
    to keep it stopped at the desired position.  I haven't thought it
    completely through yet but it doesn't seem too difficult and would
    be light!
    
    Bill

RE: < Note 387.133 by LEDS3::LEWIS >
    
    Bill, 

    Sounds like a very clever solution.  Maybe an optical sensor would
    be best - you could just point it at the prop from inside the
    fuselage.  That way nothing would have to be added to the prop or
    motor shaft (it might throw it off balance) 

    ----------------------------------------------------------------------

               THE ELECTROSTREAK IS READY TO FLY AGAIN!!

    I just got the new motor at lunch time and popped it in.  I'll be
    using the 7-4 folding prop to begin with.  I've been trying to call
    Astro Flight all week to see if they did / did not repair and return
    my old motor yet.  They must all be on vacation this week or
    something...

    Anyway, there is an Electric Fun Fly in Northern Conn. this Sunday
    (June 5th) that I am going to attend (see Model Aviation or send me
    mail for information).  Since I couldn't verify from Astro Flight
    that my old motor would be here in time, I got nervous and mail
    ordered another motor.  (It's a good thing I did - the old one is
    not here yet.)

    The new motor I ordered is the "souped up" version: the 7 cell Astro
    Cobalt 05 FAI Racing Motor.  It is the same size and weight as the
    normal Cobalt 05 but puts out 200 watts instead of only 125.  Since
    "Ah' can't change the laws of physics", I expect it will run only a
    little better than half as long (maybe 2.5 to 3 minutes).  However,
    with this much power, it might be able to go STRAIGHT UP with the
    right prop.  At least I'm hoping it will do that... we'll see.

    When I got the motor installed I tried to bench run it for a few
    seconds.  Started up fine (as all electrics always do :-) but when I
    got it to full throttle: "POP!".  The 20 A fuse blew.  Darn!  I
    should have known that ahead of time.  So off to the store to buy
    some 25 and 30 A fuses.  I'll try it again after work.

    Sooo...  This leads us to the next point:  Bill, Charlie, Randy,
    (anyone else):  Want to see it fly??  If I don't get an answer from
    you guys by 5 PM, I'll assume you're busy tonight and I'll go to the
    CRRC field.  If you guys can make it, I can meet you at the CMRCM
    field right after work.  I'll probably be flying it tomorrow too (if
    I don't decide to go see the Blue Angles at the last minute).  I'll
    check my mail and the notes file tomorrow...

                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |            Happy Landings!
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|              - Dan Miner
     |_/      |___________|  |_________|  |
                      |       /           |     " The Earth needs more OZONE,
                      |      /                       not Caster Oil!! "    
                      |_____/

    Dan, be on the lookout for Sanyo 1700 MAH cells, they can be had,
    although they are few and far between, and the increased 40% cell
    capacity will help make up for the 60% increase in motor power draw.

    Sorry, but electricity and rain don't mix well, and I think you
    will find it raining by 5:00 today.

    
    Ok Dan, as promised here's my "review".
    
    Friday night the clouds were menacing but Charlie Watt and Dan Miner
    had made a date to meet at the CMRCM field - saw Charlie on the way out
    of work and told him I probably wouldn't be able to make it.  As I left
    work around 6:00, the rain hadn't started so I figured I'd shoot
    over to the field (just had to see the Electrostreak, what with
    all these wild claims I've been hearing).

    Dan and Charlie were there, and I have to say the 'streak is a beauty!
    Dan did a real nice job on it.  He asked me to do the honors on
    the first flight - I didn't know what to expect but was happy to
    oblige.  Fed in some throttle (Dan later mentioned that I didn't
    have to feed in throttle so slowly but it's force of habit) and
    Dan hand launched it.
    
                           -- WOW --

    What I had here was _not_ a marginally powered electric plane.
    This was a zippy, aerobatic beauty that could climb like crazy,
    do inside and outside loops, rolls, snap rolls, inverted flight,
    you name it.  Not only that, but with power off if floated beautifully.
    
    We didn't get long flights out of it, since as Dan mentioned before
    he has the hot engine in it with the same battery.  I'm convinced
    that the 'streak with a standard Astro 05 cobalt would be plenty,
    and with the new 1.7 AH batteries it should get flights in the 8-10
    minute range (I think we were getting about half that).

    Anyhow, I'm convinced that electric is for real.  I'm going to order
    an Astro cobalt engine for myself!
    
    Bill

    	Bill beat me to it, but I was also very impressed with the
    'Streak's performance.  It was light and zippy.  It flies like a
    small pattern ship and glides very nicely with the power off.  We
    had a perfect evening to test fly it with almost zero wind.  The
    rain held off and we flew until the mosquitos started feasting on
    us.  Thanks Dan for letting us fly your excellent ship.  You've
    got Bill and I hooked.  This is the first electric that I have been
    impressed with.  I'm not into powered sailplanes and those are the
    only other really successful electrice that I have seen.  I haven't
    seen Randy's Cub fly yet, so I can't comment on it's performance.
    
    If Dan can get those new 1700 Ma batteries, he will get good duration
    and performance together.  More prop experimentation may give him
    more duration as well.  I would like to see the difference with
    the other Astro 05 that makes less power for more minutes before
    I order a motor.
    
    Thanks again, Dan
    
    
    Charlie
    

    DAN: 
    	How much of the prop sticks out beyond the bottom of the fuselage?
     I am curiou because I have a Leisure Wasp with an LT-50 motor that
    I have been flying for 2 seasons.  I run a Cox 6-4 prop and am still
    on the first prop and have never bent the shaft(which is considerably
    smaller in diam than the Astro).  This ship will also do many
    aerobatics but is limited  due to no rudder control.  
    	This topic is sparking my interest again.  My streak has been
    1/2 finished since the snow was on the ground.  I think I'll finish
    it and use my LT-50 for starters.

    Dan,

    Firsthand experience with "stock" 05 motors (like the one that
    comes with the PT) dictates that you should buy a higher
    performance motor.  A guy here at LEDS has purchased  a PT, but he
    also bought an Electra, and he's building that first.  I suggest
    that you spring for a Cobalt 05 geared motor to go along with the
    PT, you will get much better results from the plane, and may even
    be able to ROG from grass.

Since this is a _long_ note, I'll give you a Fun Fly summary up front:
  - It was a VERY windy day!!
  - The contest was a lot of fun in spite of the fact that probably
    1/2 to 2/3 of the entries crashed.  (Some with only minor damage.)
  - The Electrostreak (and I) won THIRD PLACE in an event!!  :-)  (My first!!)
  - The Electrostreak crashed and needs a nose job.  :-(
  - There was a pattern plane there that performed MUCH better than the 
    Electrostreak!!  It even did R.O.G.!!  (Rise Off GRASS!!)  
    (Sorry, you'll have to read on for details...  :-)

------------------------------------------------------------------------------

First, I'll catch up on some previous notes:

Bill and Charlie:  Thanks for the "good press"!!  I'm really tickled
pink that you two experts like my little electric!!  As you guys said,
the 'streak performs well on the 7-4 folding prop with the Astro Cobalt
05 FAI Racing Motor.  It performs even better with a wooden Rev-Up 7-6!! 
(I just got my "old" Astro Cobalt 05 (non-FAI) back from Astro Flight
last Thursday.  About a 3 week turnaround!!)

-.135: Chris True told me that the 1700 mAh cells are great for car use
but can't supply the current required for these hot Cobalt motors.  
(This guy is a genuine electric EXPERT:  His picture appears in the
Jan. 1988 Model Aviation electrics column.)  I'm going to try to get
some more facts about this before I buy any of the 1700's.

-.138: About 2 inches of the prop hangs below the fuselage.  With my
older Astro Sport and Leisure LT-50, I had good luck with the Cox 6-4,
too.  However, the Astro Cobalt works best on a 7-4 to 7-6 prop and Cox
doesn't make these (as far as I know).  Astro Flight recommends Taipan
brand plastic props and I plan on getting some - just haven't gotten
around to it yet...  The plastic prop should basically eliminate the
prop breakage/bent motor shaft problem.

-.139 & .140: Dan Snow: Good Luck with the PT-Electric!!  I'm very
interested in seeing it fly when you get it done.  I too would like to
recommend that you throw away the motor that comes with it and use an
Astro Cobalt.  I am even willing to let you "Test Fly" one of my motors
if you aren't convinced.

------------------------------------------------------------------------------

And now, on to the Electric Fun Fly from June 5th!!

Sunday, June 5th was a very, VERY windy day.  I don't know the actual
wind speed but would guess it was about 10 to 15 mph on average with
some gusts pushing 25 to 30 mph.  This wind was the cause of the demise
of quite a few of the entries.  I didn't count them exactly, but I think
there were about the following mix of planes:

    - The infamous Electrostreak    ;-)
    - An Astro Challenger with a geared Astro 05 (A _GREAT_ performing
      motor glider that belongs to a friend of mine.)
    - about 5 or 6 Goldberg Electras (motor gliders)
    - a Great Planes ElectriCub
    - an Old Timer I didn't catch the name of  (It won first in an event)
    - A Leisure Playboy Old Timer
    - The "Mystery Plane" that was a _HOT_ performer...  (keep reading...)
    - and maybe a few others I can't remember right now...

All in all, about 12 to 15 planes.  The contest events were:

    - Duration - Limited Motor run:  3 rounds (flights) - 45 seconds of 
      motor run - stop motor - glide down.  Each flight is timed and the
      best total of all 3 flights wins.  (NO scores dropped...)
    - Duration - Limited power: 3 rounds (flights) with _NO_ charging of
      the motor batteries allowed between flights!!  (All entrants never
      reached the 8 minute maximum on their first flight - they
      intentionally used up all of the battery on the first flight and
      took zero scores for the 2nd and 3rd flights.)
    - A pylon race ONLY FOR STOCK GOLDBERG ELECTRAS!!  (This was FUNNY!!)
    - A "sort-of-scale-electric" event.  Since the ElectriCub was the only
      entry, it won.  (Flew OK too...)

Registration started at 9:00 AM and the events started at 10:00 AM. 
This was a _VERY_ casually run contest.  Basically, the C.D. just said
"OK, it's 10:00 - let's start the events.  Go ahead whenever you're
ready."  And that's ALL he did - we were on our own to decide which
events to do in whatever order we wanted!!  This was good because it
gave you the flexibility to wait for a good thermal but was bad because
people just waited around for the wind to die down.  All the wind did
throughout the day was to blow harder.  If the CD had pushed us more to
get in the air maybe not quite as many would have crashed.  (MAYBE!!)

The Electrostreak generated lots of interest from everyone there - I
felt like a TV celebrity or something!!  It was GREAT!!  I'm so proud of
that little hunk of balsa, plastic, and Cobalt.  It made me feel good to
have it generate so much interest.

Anyway, I figured that the only event the 'streak would have a chance in
was the Limited Motor Run Duration event since it can climb really fast
and glides pretty well.  It turns out I probably could have done well in
the Limited Power Duration event also, but I didn't enter.  

My first flight of the day was for the contest - I decided since it was
so windy I should get at least one score before a possible crash.  This
flight lasted 2 minutes, 57 seconds - the longest flight in this event
of ANYONE for the whole day!!  (Remember, only 45 seconds of motor run
at the beginning.)  The landing was textbook.  I greased it in nicely
and even had time to "blip" the throttle to get the prop stopped
horizontal. (I used a wooden Rev-Up 7-6 prop).  
    No broken prop, no bent shaft!!  (YEAH!!)

After recharging and "chewing the fat" for a while, I decided to take
the 'streak up and show everyone what she could do.  In other words, a
flight NOT for the contest - just a "show off" flight...  It was a great
flight and I could hear a lot of "Wow!!" 's and such from behind me. 
The landing was nice but I broke a prop.  (Motor shaft OK.)

Next, my friend Hogan decided he'd take a practice flight before
competing with his Astro Challenger and asked for my assistance.  
(This in itself is a long winded story and I've decided to put it in
"Ramblin'".)

After I had recovered from this mess of excitement, I decided to go for
my second competition flight on the Electrostreak.  Once again it went
up like a rocket and glided pretty well.  However, mother nature wasn't
cooperating, and all I could find was sink instead of lift.  Flight time
was only about 2 minutes.  (Typical times for other contestants varied
from 1.5 to 2 minutes.)

When I was getting ready to land, I tried to keep up some extra airspeed
because it was so gusty.  I set up in the landing pattern going
downwind.  I did the turn around (a right turn) for the final approach
and was just starting to feed in left aileron to level out.  
All of a sudden : 
    - SNAP!!  (A nice snap roll to the right)
    - ZIP!!   (The sound of the plane heading straight down for 15 feet)
    - POP!!   (The sound of the fuselage slamming into the ground.)

The fuselage in front of the wing was very crunched and was NOT field
repairable.   :-(   The wing and the rest of the fuselage is in fine
shape and I'm now in the process of replacing the nose.  

I now realize that I should have used more rudder to help prevent the
snap roll and should have kept up even more airspeed than I did.  I'm
not too sure, but I think part of the cause of the crash was because the
wind slowed down just before the snap - thus causing the airspeed to
drop and the wing to stall.  Looking on the bright side, I can say the
this was my first crash that wasn't 100% pilot error.  (Only 90%  :-)

So, I got a zero for my third flight and STILL managed to get THIRD
PLACE (out of about 12 contestants)!!  Most of the other contestants
survived at least long enough to get their third flight in this event. 
I am certain I would have won first if I were able to fly the third
flight.  Oh well... I'll have to try again at the next contest...

And now, as promised, some info on the TOTALLY AWESOME electric pattern
plane that was there.  Chris True (mentioned above) brought his "Blue
Angel" which is a pattern plane kit from "MK" designed for a .25 glow
engine.  (He said that the kit can be mail ordered from Indy.)  Chris
built the plane almost totally as per the plans and strapped an Astro
Cobalt 15 geared motor in the nose.  This plane was INCREDIBLE!!  It was
in every way a true pattern plane.  He could taxi and take off from GRASS,
perform all of the pattern maneuvers including 4 point rolls, and then
land without breaking the prop.  :-)  The performance was outstanding!! 
It definitely took some of the "shine" off of my Electrostreak.  :-)  

Other vital statistics of the plane are: 
    flight times of about 3.75 minutes, 
    14 x 800 mAh Sanyo cells (1200 mAh cells won't fit), 
    a Kyosho 9-8 prop (from an Etude), 
    Jomar speed controller with large heat sink, 
    3 Futaba S-33 microservos, and 
    fixed trike landing gear.

Simply: AWESOME!!  This is the plane that MIGHT convince even the Desert
Rat to at lest TRY electric!!  ;-)  (Al, do you read the electric notes??)

                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |            Happy Landings!
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|              - Dan Miner
     |_/      |___________|  |_________|  |
                      |       /           |     " The Earth needs more OZONE,
                      |      /                       not Caster Oil!! "    
                      |_____/

    R: .141, Dan,
    
    Yep', I read virtually all new notes though, if pressed for time,
    I confess to just "scanning" the car/boat stuff.  (Before I get
    tons of hate-mail, no offense intended, guys, it's just not my bag,
    too limited in dimension for my tastes, i.e. if it don't fly, I
    ain't interested.)
    
    On the electrics, Dan, I'll consider one on the day when I see an
    electric-powered, full-scale prototype.  Since I'm almost exclusively
    into WW-II fighters, that likelihood seems pretty remote.  Maybe
    what we'll wind up with someday is electric powered aircraft with
    onboard "engine-noise generators."  At the present, my primary
    objection to electric, aside from the low available power vs. power-
    plant weight, is the lack of engine-noise;  I KNOW, I know, that's
    considered a plus by some and salvation by others with field/noise
    problems, but I just can't adjust to the lack of some/any engine
    sound.  Please don't take offense as none's intended, but this adds
    to the toy-image, to me, and I avoid that stigma like the plague.
    
    I'll concede in a heartbeat, however, that it must be great not
    to have to scrape all that greasy gluck offa' yer' bird at the end
    of a flying session..._that_ I truly envy!   

      |
      | |      00	 Adios,      Al       
    |_|_|      ( >o
      |    Z__(O_\_	(The Desert Rat)

RE: < Note 387.143 by PNO::CASEYA "THE DESERT RAT (I-RC-AV8)" >

>    On the electrics, Dan, I'll consider one on the day when I see an
>    electric-powered, full-scale prototype.  

    Well, there HAS been a full scale electric powered plane.  I
    don't have the article in front of me now (it's home), but it
    was one of those planes that looks like the "human powered"
    planes and it flew across the English Channel.  It was solar
    powered (maybe had batteries too??) and used 2 Astro Cobalt 60
    motors for power.  (Gee, model airplane motors in a full scale
    plane...)  BTW, when you figure it out, these motors put out
    over 2 horsepower each!  (1200 watts)

    Not exactly a WW-II fighter, but maybe someday...  Anyway, I do
    understand your point of view, Al.  I guess I'll have to start
    working on a little noise generator circuit....  :-)  (Let's
    see... this switch makes it sound like a 2 stroke, this one like
    a 4 stroke and this switch makes it sound like a full scale
    plane...  :-)

    You're right - not having to clean up at the end of the day is
    GREAT!  In fact, that was one of the main reasons I got into
    electrics in the first place.

                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |            Happy Landings!
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|              - Dan Miner
     |_/      |___________|  |_________|  |
                      |       /           |     " The Earth needs more OZONE,
                      |      /                       not Caster Oil!! "    
                      |_____/

    Re: .-1, Dan,
    
    Yeah, the plane you refer to was one of Dr. Paul McReady's designs,
    a'la Gossamer Albatross, Gossamer Condor, etc.  I remember the
    experiment well as it was conducted in the desert near Tucson a
    few years ago to take advantage of the 300+ days of bright sunshine
    we have here, a necessary adjunct to the solar cells that supplied
    current to the electric motor(s).  As I recall, the craft was incapable
    of takeoff under its own power, requiring that the pilot "peddle"
    it aloft, whereafter the solar-cell powered electric motors could
    just barely maintain flight for a limited time.
    
    As you suggest, however, a model of this 5-10mph airplane would
    hardly be my cup-o-tea...sounds about as exciting as watching
    a can rust.  :B^)

      |  
      | |      00	 Adios,      Al
    |_|_|      ( >o
      |    Z__(O_\_	(The Desert Rat)

        The first iteration was a left over Gossamer Condor, retrofitted
        with batteries, solar pannels, and motor. The plane built for the
        third Kremer prize (eventually won by MIT) was the Bionic Bat. The
        pilot pumped energy into the plane (peadled to charge nicads)
        before takeoff, and then used that extra energy in flight. The MIT
        plane, Monarch, is hanging in the Boston Science museum. It was
        also a hybred human/electric design, without the solar pannels. 

    re: -.143,  Al-
    
    Funny you should talk about sound for electrics...
    
    I went to the WRAM show near Baltimore a couple of weeks ago,  one
    of the vendors was RAM.  They had _ALL KINDS_ of sound effects
    generators, strobes, and other assorted modules.  How about a sailplane
    with a multi-cylinder diesel engine, foghorn and euro-sirens :^)
    
    (NO, I didn't get that for my sailplane, it was a just-suppose!!)
    
                             |                      
   \	       	         ____|____                      /   Regards,
    \________________________O_________________________/    Frank.
    

>    	But what the heck, it's covered, and as soon as I finish the
>    motor break-in and installation it'll be ready for it's first flight.

What is the consequence of not breaking in your electric - bad idle?

Bye
Kay R. Fisher

    Electric motor brushes have to be seated correctly around the armature,
    else they erode very quickly and also erode the armature from the
    excessive amount of sparking.
    
    This sparking not only makes a lot of RFI, it also makes lots of
    ozone, which attacks the motor wire enamel.
    	
    Finally, a not-broken-in motor will not produce anywhere near as
    much torque as one that's correctly broken in.
    
    	-Bill

    Bill,
    
    Verry interesting...I must admit this is the first time I've ever
    heard of any such a thing.  Can you expand a little, i.e. just _how_
    does one break in an electric motor?  Also, could/should this break-
    in technique be appled to power-tools, e.g. drills, Dremel-tools,
    etc. to improve performance and extend life??    

      |
      | |      00	 Adios,      Al
    |_|_|      ( >o
      |    Z__(O_\_	(The Desert Rat)

>    heard of any such a thing.  Can you expand a little, i.e. just _how_
>    does one break in an electric motor?  Also, could/should this break-

    Al,
    
    I'm not Mr. Bill, but being an electric flyer, I can answer your
    questions.  As Bill stated, very suscinctly I might add, motor
    break-in is reccomended in order to "seat" the brushes on the
    commutator.

    Usually, brushes are manufactured with a square face. As the motor
    is run, the brush wears and "seats" against the round commutator,
    eventually aquiring a round, concave face which matches the
    curvature of the commutator.  This increases the contact area of
    the brush/commutator interface, and provides a number of benefits
    to the operation of the motor.  First, of course, is that the
    increased contact area allows more current to flow, with lower
    resistance.  Second is that, since the commutator is rarely
    completely round, the increased contact area reduces the amount of
    arcing that occurs as a result of the brush "floating" over the
    geometrical irregularities (this is why some motors claim to have
    diamond trued commutators, truing improves the commutator
    "roundness").  Thirdly, is that the reduced arcing both improves
    motor power and reduces pitting and wear of both the commutator
    and the brushes, thus extending motor life significantly.

    Astro flight motors come from the factory already run-in.  Motors
    from other manufacturers reccomend a few hours of unloaded running
    at about 1/4 to 1/2 the motors nominal running voltage.  Typical
    05 motors, like for the Goldberg Electra or the PT-Electric (no
    longer confused with a Cinder Block), need an hour at about 4
    volts (although I have seen recommendations of overnight at around
    2 volts).  The main purpose is to round out the brush, so it seats
    well agains the commutator, without using a voltage high enough to
    cause arcing.

    As to whether or not this is of any benefit in power tools, the
    answer is of course that it certainly can't hurt.  In an electric
    plane or car, you really have to worry about losing a few percent
    efficiency because of not breaking in your motor, it makes a
    difference.  With a Dremel or even a Table Saw, I doubt that you
    would notice.

    Most big-motor (that is, fractional-horsepower power tools, etc)
    come with brushes that are already pre-ground to match the contour
    of the commutator.  A few seconds of running-in is all that is
    necessary.  (DANGER- don't put the brushes into your moto-tool with
    the curved end facing the wrong way!  Instant broken commutator!)
    
    The standard RS-540 Tamiya motor sealed-can motor also has pre-ground
    brushes, and does not need break-in.
    
    The only motor I've used that explicitly required break-in was my
    Technipower tunable; the instructions stated that I should go out
    and buy a pair of flashlight batteries (3 volts), tape the cells
    together, tape one motor lead to each end, place where a good breeze
    is blowing, and allow to run 10 min.  Then remove one lead, wait
    ten min. Repeat this until the batteries are dead, Dead, DEAD.
    Breakin is then complete.  Repeat this if I replace the brushes.
                                                
    I don't know what would have happened if I didn't do this, but the
    motor sure runs nice.  
    
    -----
    
    The older BIG motors and generators (both AC and DC) had exposed
    commutators so that the commutators could be cleaned and the brushes
    changed WHILE IN OPERATION.  I had an old G.E. manual that told how to
    do this in relative safety! :-)  (Note: these motors were BIG- six feet
    in diameter, four feet thick, etc. ) 
    
                                                                     
		\__    		-Bill
	  {((___O===--0'         Yerazunis
    

    I need some opinions here...
    
    I have a Sureflight foam wing from a Cessna 150, about 54" wingspan.
    I also have Sorry Willie's pair of "540 Class" motors and I have
    picked up a pair of 7.2V, 1200mah packs and charger.  
    
    I'm thinking...  If I make a simple box-type fuse and mount the
    motors on the wings to a common battery in the fuse with an on-off
    servo/switch I should be able to fly this mess!
    
    I'm also thinking... Epoxy pods onto the wings to mount the motors
    and if I really plan it right, I won't even need landing gear (although
    I could put it on and still hand launch).  Should I (could I) use
    Ultracoat on the foam wings?
    
    Anyway, there's the rough idea...  I'm looking for suggestions,
    holes in the plan, etc.   THANKS in advance, folks...
    
                             |                      
   \	       	         ____|____                      /   Regards,
    \________________________O_________________________/    Frank.
    

RE: < Note 387.160 by MJOVAX::BENSON "__Frank Benson, DTN 348-2244__" >

    Frank,

    I haven't personally ran a twin electric (yet) but from what I've
    read, the way to wire it up is to put two battery packs in series
    with the motors wired in series like this:

                --------                           --------
                |     +|---------(switch)----------|+     |
                | Batt |                           | Motor|
                |     -|---                     ---|-     |
                --------  |                     |  --------
                          |                     |
                --------  |                     |  --------
                |     +|---                     ---|+     |
                | Batt |                           | Motor|
                |     -|---------------------------|-     |
                --------                           --------

    This way, if one of the motors draws a little more current than the
    other one, it doesn't matter.  (Both motors will still run out of
    power at the same time instead of one dying before the other.)

    I don't recommend using only one battery pack for two motors.  If
    you wire the motors in parallel, you will draw twice the current
    from the battery (and get 1/2 the run time) and the battery will
    heat up much more.  You may be able to get away with it with these
    motors because I don't _think_ that they draw more than 10 amps. 
    (You should check this if you decide to go this way.)  I'm not sure,
    but I would guess that the Kyosho DUET uses this method.  Anyone out
    there know for sure?  The obvious advantage here is that you have to
    deal with the weight of only one battery pack.

    On the other hand, if you wire the motors in series (as the drawing
    above) but with only one battery pack, you will get only 1/2 the
    voltage to each of the motors.  This will give you VERY poor
    performance - don't even think about it.

    Bottom line (in my opinion) is: IF YOU USE TWO MOTORS, USE TWO PACKS.

    I think it might be best to just go with one motor and keep the
    second one as a spare.  But, hey, a twin sounds like fun too!

    Other _possible_ (minor) problem areas I see are:
      - if you mount the motor pods to the foam wings, will the wings
        be strong enough to withstand the force of the motors and/or
        a hard landing?
      - building a fuselage big enough (and strong enough) to hold 2
        battery packs, Rx, and servos could be difficult.  (But, by no
        means impossible!)

    As far as using Ultracote on the wings, I think that it is too high
    of a temperature film for direct application to foam.  Black Baron
    film would be a better choice.  Just be aware that you will probably
    get colored adhesive goop on your iron.

    Don't bother to put on landing gear - they add too much weight and
    drag.  After you fly it for a few flights and find it has out of
    sight vertical performance, then add the landing gear.  :-)

    Although this message may sound a little negative, actually I think
    is sounds like a good idea.  Experimentation is what makes this
    hobby fun and exciting!     GO FOR IT!!!

                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |            Happy Landings!
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|              - Dan Miner
     |_/      |___________|  |_________|  |
                      |       /           |     " The Earth needs more OZONE,
                      |      /                       not Caster Oil!! "    
                      |_____/

    hey dan miner, i say to heck with the ozone, and pass the fantastik.
    
    on a heavier note, just this weekend i tried covering foam with
    ultracote.  i was scared of meltdown but it turned out to work
    real well.  i found a low temp that worked and kept it, so i dont
    know how much margin there is between "the ultracote wont stick"
    and "the foam melts".  but it works...
    
    kevin

>    read, the way to wire it up is to put two battery packs in series
>    with the motors wired in series like this:

>    On the other hand, if you wire the motors in series (as the drawing
>    above) but with only one battery pack, you will get only 1/2 the
>    voltage to each of the motors.  This will give you VERY poor
>    performance - don't even think about it.

    I beg to differ, wire the motors in series or in parallel, use
    only one pack.  The run time is certainly reduced by a factor of
    2, but the whole point of the twin is to get more flying power.
    Whats the point of twice the motor, if you just go ahead and
    double the weight ?

    I have seen a number of arguments about how to wire twins, but
    never a statement that one way is better than the other.  The book
    I have on electric flight (had, I lent it to someone...) said to
    try it both ways.  Things like prop size can make a difference to
    the setup, and different given configurations may require
    different setups.  Maybe Charlie Watt could give us his opinion
    here, since I am by no means an expert on electric motors.  I do
    specifically remember reading about the DUET, and suggestions by
    someone who had tried, that series/parallel made little difference
    to the planes performance.  Two packs in parallel, however, will
    probably damage your motors.  They are not designed to run at
    twice their nominal voltage, and I don't think that putting two
    motors in series yields a "virtual" voltage of 1/2.

    How about it Charlie ?  Set us straight !

               |  /
    Randy (:^D)==<
               |  \

        Re:< Note 387.163 by LEDS::COHEN >

                You don't  have  to  be a Charlie to aswer that question,
        high school maths gives you the answer:
        
                Two packs in  parallel gives you exactly the asme voltage
        as a single pack, but half the internal resistance.  Tho packs in
        series  gives  you twice the  voltage  with  twice  the  internal
        resistance.
        
                You can run two motors in  parallel on a single pack, but
        you will get half the run time.   With motors in parallel and two
        packs in parallel each motor gets the proper voltage and the same
        run time as a single motor on a single pack.  You get exactly the
        same effect with all the motors and packs in series.    Twice the
        voltage  from  the  packs  and twice the resistance in the motors
        gives you the same current as a single motor on a single pack.
        
                The bottom line is that you can either connect everything
        up in series or have the two packs in parallel and the two motors
        in parallel.
        
                Don't ever put the  packs  in  series  and  the motors in
        parallel, you end up feeding  the  motors  twice the voltage they
        are supposed to get - watch them fry.
        
                If you like sluggish flight wire  the  packs  in parallel
        and the motors in series.  They  will  get  half  the voltage and
        hardly move.
        
        Anker

    I may be wrong but I don't think that I would connect up nicads
    in parallel as the slightest difference in charge state between
    the two packs, or voltage, will cause one battery to attempt to
    charge the other pack and with thier mimimum internal resistance
    a lot of current could flow for a short period of time I think.
    
    Mike
    

    
    I disagree with all of the suggestions so far, although Mike's
    right about putting nicads in parallel - I wouldn't recommend it.
    Randy said an extra battery would double the weight - that means
    the plane, motor and servos weigh 0 lbs?
    
    I would connect each motor to its own battery with a speed controller
    and use a synchronizer to keep the RPMs matched.  If you want to
    go cheaply then put the speed controller on only one of the
    motors and use trim to match RPMs.
    
    Dan was worried about one motor quitting first, but I think that
    would be better than going completely deadstick.  The obvious solution
    is to time your flight so neither motor goes dead.
    
    Bill

    You can wire nicads in parallel as long as you do it when they're
    discharged, and you charge them together. A nicad of any size can
    be compared to a lot of smaller ones in parallel. I agree that
    connecting charged nicads in parallel is dangerous.
    
    						John.

    Good info so far...
    
    THANKS-
    
    BTW- I have been leaning to the motors in parallel with one battery
    scenario since prior to posting my initial note-  its better to
    deadstick than to come in one engine out.  (I doubt _that_ statement
    will pass unchallenged!)
    
                             |                      
   \	       	         ____|____                      /   Regards,
    \________________________O_________________________/    Frank.
    

    1) when your airframe weighs in at 7 Oz. and the power system
    weighs in at 20 Oz, adding another 20 Oz. for a second motor and
    battery might just as well be considered doubling the weight.

    2) a single large nicad is not the same as a bunch of smaller ones
    in parallel.  That is why nicads come in larger capacity sizes
    (current-wise, that is).  Connecting two packs in parallel will be
    bad for the one that discharges first.  Don't fool yourself into
    thinking that all nicads are created equal.  individual cells are
    as different as any other electronic device (like matched pairs of
    transistors, nicads also come in matched groups).  Computer
    matching of cells helps insure that all cells in a pack have the
    same charge/discharge characteristics, but it doesn't guarantee
    it.  When a pack is run, some cells discharge faster or slower
    than others.  Put two packs in parallel, and eventually, one pack
    is going to start to backcharge the other.  bad bad bad.

    Well, thats all I've got to say for the moment.


    Randy  (:^D)

    Also, having just reread the last few notes :

    1) RE .166, the whole point of twin electrics, aside from
    additional power, is that they don't require synchronization.  The
    motors run at nearly the same speed, provided they are attached to
    the same power source, and they are in similar operational
    condition. The beauty of the system is defeated if you use two
    separate power systems.  Don't do it. 

    2) RE .167, Nicads are NEVER discharged, they are only fully
    charged or less than fully charged.  Deep cycling packs (which is
    a good way to eliminate the "memory" nicad cells develop) is
    usually defined as the point when the cell voltage reaches 1 volt.
    This is considered a discharged cell, but it is far from "empty"
    at this point.  Full discharge of Nicads is not recommended, this
    is how Nicads develop internal shorts.

    The danger you ascribe to backcharging nicads is applicable when
    you connect the batteries in series. The matching of cells is done
    to insure that all batteries discharge evenly when connected in
    series. Many companies offer "matched cells" nicad packs. These
    cells are connected in series. Discharging unmatched cells too low
    can result in backcharging and resultant shorts ( matching is a
    matter of degree ).
    
    Wiring them in parallel introduces load balancing. If one runs out
    a little before the other, it will be slightly forward charged.
    Of course, energy is lost during charging/discharging, so you want
    to use batteries that have the same rating. You should also keep
    the brand and type of battery the same so that the energy/voltage
    curve is equal.
    
    In short, the tolerance for connecting nicads in series is alot
    tighter than connecting them in parallel. If you connect them in
    parallel, you are less likely to experience problems. No matter
    how you configure the batteries, parallel/series, always connect
    them when discharged, and charge them together as a single unit.
    
    Batteries are shipped in the discharged state, so if you're starting
    off with a new set ( recommended ), then is the perfect time to
    connect them together.
    
    							John.

    WOW!  This certainly has become a lively topic.  :-)  

    When analyzing multiple motor and/or battery combinations, think of
    the motors as simple resistors.  (Yes this is greatly simplified but
    it is totally sufficient for this analysis.)

    If you put two motors (or resistors) in parallel, they will draw
    twice the current (the resistance is 1/2) and the voltage will be
    the same as one motor (or resistor).

    If you put two motors (or resistors) in series, they will draw the
    same current and the voltage will be twice as much as one motor (or
    resistor).  This statement assumes you apply twice the voltage to
    the motors (or resistors).  If you apply the same voltage (only one
    pack), then the voltage across each motor will be 1/2.

    Based on my opinion (and the others in previous replies) here are
    the combinations that are safe and useful:  (ALWAYS USE A FUSE!!)
      
     1)     ----- - B + ----- - B + ----- + M - ----- + M - -----
            |                                                   |
            -------- (switch, fuse, and speed control) ----------

        Batteries and motors in series. Assuming both motors are the 
        same (ie, same "resistance"), then the voltage and current 
        across each motor is the same as in a 1 battery / 1 motor system.


     2)     ----- - B + ----------------- + M - -----------------
            |                                                   |
            ------------ (switch and speed control) -------------

            ----------------- - B + ----------------- + M - -----
            |                                                   |
            -------- (switch, fuse, and speed control) ----------

        Two totally separate 1 battery / 1 motor systems.


                                  --------------------
                                  |                  |
     3)     ----- - B + ----------------- + M - --   -- + M - -----
            |                                    |                |
            -- (switch, fuse, and speed control) ------------------

        One battery wired to two motors in parallel.  Both motors see
        exactly the same voltage. 

    #1 has the advantage that you can use all of the power from both
    batteries.  If one pack was not fully charged or has a slightly
    lower capacity (not all NiCads cells are identical), then the other
    pack can still supply 1/2 the voltage to both motors.  
    (This is the method I recommend.)  

    #2 has the advantage of simplicity.  However, if one pack is lower
    in capacity, that motor will die first and you will have an "engine
    out twin".  I am told that in a twin engined plane, having one
    engine out is a real pain.  Of course, you can shut off the other
    motor too and have a heavy glider.  #1 would still allow you to run
    at half speed on both motors until the second pack was also dead. 
    (Useful for a "go around" on landing.)  

    A way around this problem is to time your flight and land before the
    packs die.  Personally, I don't have the discipline to do this - I'm
    usually having so much fun I want to use up every electron I can
    get!  :-)

    #3 has the advantage of less weight due to only one battery pack and
    that both motors will run out of power at the same time. 
    Disadvantages are that the battery and speed controller must be able
    to handle TWICE THE CURRENT of either of the other systems and the
    battery will last only 1/2 as long.  If the current demands of the
    motors is greater than the battery or speed controller can handle,
    this will be an UNSAFE solution.  (Battery will get very hot and
    might explode.)


    And, here are the combinations that are NOT safe or useful:


     I)     ----- - B + ----------------- + M - ----- + M - -----
            |                                                   |
            -------- (switch, fuse, and speed control) ----------

        One battery connected to two motors in series.  This system is
        safe (electrically) but not too useful or safe from an
        aerodynamic point of view.  Each motor will see 1/2 of the
        voltage it wants to and thus - will be running at 1/2 speed. 
        All this will do is improve your glide ratio.  :-)


     II)    ----- - B + ----- - B + ----------------- + M - -----
            |                                                   |
            -------- (switch, fuse, and speed control) ----------

        Two batteries in series connected to one motor.  This could be
        fun if you are into fires and explosions - the motor isn't
        designed to handle this much voltage (two times normal).


                                  --------------------
                                  |                  |
     III)   ---- - B + --- - B + -------- + M - --   -- + M - -----
            |                                    |                |
            -- (switch, fuse, and speed control) ------------------

        Two batteries in series connected to two motors wired in
        parallel.  Even more "fun" than II) above.  Now you have twice
        the voltage AND twice the current.  Both the motors and the
        batteries will get very hot and may catch fire or explode.


            -------------------------------------------------------
     IV)    |    |                                          |     |
            +    +                                          +     +
            B    B                                          M     M
            -    -                                          -     -
            |    |                                          |     |
            -------- (switch, fuse, and speed control) ----------

        Two batteries in parallel connected to two motors in parallel.
        This is similar to safe solution #3 from above and overcomes the
        1/2 duration problem.  However, it adds the danger of connecting
        two packs in parallel.  (May be overcome by connecting the packs
        while they are discharged and then charging them.  Personally, I
        would not do this - Murphy's Law will catch up with you and
        someday, you will connect the packs when they are charged...)

    re .172:
    
    I thought I would clarify this: When either connecting two batteries
    in parallel or series, the best approach is to use brand new batteries,
    solder them together, and for all intents and purposes, treat them
    as though they were one pack, ie. never seperate them. For the best
    performance, use matched packs. Your pack is only as strong as your
    weakest cell.
    
    I also want to recommend that if you want to use two batteries,
    connecting them in parallel is preferable as long as you solder
    them together right out of the box.
    
    Motors are not simple resistors, and if you plan on turning the
    aircraft, you will have an unbalanced load. Most speed controllers
    can handle more then 100A, so if you connect them in parallel, you
    can get an off the shelf item.
    
    Keep the wires as short as possible, as wiring the batteries in
    parallel will increase the energy losses in your wiring.
    
    						John.

    re: .169 - weight
    
    lemme see if I understand this, Randy. I believe the equation is:
    
    20 + (20 + 7) = 2 * (20 + 7)
    
    20 + 27 = 2 * 27
    
    47 = 54
    
    Ok. Now I understand! I thought you were making a mistake there.
    Sorry! I never did very well in relativity.
    

    If all you engineers would practice what you preach, you'd never
    make it out to the flying field! Talk about over-engineered designs...
    
    You're worried about a little unbalanced loading of your nicads,
    how it might hurt their dainty little electrodes, then after each
    flight you jump back in your car with the discharged pack and
    zap the h*ll out of it quick charging it at 10 or 20 times the
    manufacturer's recommended charge rate, run back to the flight
    line and take it up again (same goes for you earth-bound two-
    dimensional types). Gimme a break!
    
    Makes me glad I converted to management!
    
    Dave

    re .175:
    
    Yeah, that's true . . . but . . . what's the fun of arguing when
    there's nothing to argue about? I mean, what we're looking for is
    performance, if all we cared about was reliability, we'd all give
    up this nasty hobby. Most of the fun, as far as I've seen thus far,
    is putting the thing back together when it dives into the ground.
    
    It's consuming . . . When you're not flying, you're buying this
    or that part, you're fixing this or that aircraft, you're breaking
    in this or that engine. Your workbench grows until your wife has
    to rope off a little of the house for herself.
    
    I'm convinced it's the danger. Not any kind of physical danger,
    but the kind of financial danger where there are no limits as to
    what you can spend if you tend to crack up planes.
    
    For years and years I've wanted to do this, but to tell you the
    truth, the thought of travelling out saturday mornings to crash
    planes kind of scared me. Considering the scale, it's amazing those
    things don't just takeoff with the wind and smash into anything
    and everything that happens to get in the wind's way.
    
    What changed my mind? Well, patience. The patience to wait for nice
    days. The patience to build the model carefully. The patience not
    to sink every cent I have into repairing my mutilated craft.
    
    In the meantime, I'll just have to argue over nicads.
    
    						John.

    I started to put something in a couple of days ago and I got
    sidetracked.  THis topic has been beat to death already, but I will
    just put 2 cents more in.  I would run a twin with two packs in
    series with the motors connected in series with one controller.
    This might be a problem if the controller couldn't handle the double
    voltage, but I bet there are some that can since some people use
    more than 10 cells in electric planes anyway.  By the way, the packs
    should be matched so that you don't reverse charge one of them.
    The more nicads you put in series, the more of a problem this can
    be.  Don't run the thing completely dead, but only until a big loss
    of power occurs.  This is when many of the cells are discharged,
    but the slightly higher capacity ones are still putting out.  If
    this continues, the lower capacity cells can be damaged by reverse
    charging.  If the motors are equal, they will produce the same torque
    during the flight.
    
    Charlie
    

    I agree that this topic has been beaten to death, but I never let
    that stop me . . .
    
    If you wire the motors in series, it is possible to have the motors
    running at different speeds. When they are wired in parallel, they
    will not be coupled to each other.
    
    A series coupled pair of moters will:
    
    1) Provide equal torque to each motor
    2) RPM's won't be equal
    3) Voltage across each motor won't be equal
    4) Could make the aircraft unstable under certain conditions
    
    Let's say you start a turn, the inside motor has more load. Apply
    torque, and the outside motor speeds up lowering the voltage on
    the inside motor. This slows down the inside motor, further decreasing
    the voltage across it.
    
    It would have the effect of a negative dihedral, and would require
    constant rudder correction.
    
    I *will* say it's more power efficient :-)
    
    							John.

    re -.1 - The voltage across a motor means nothing when they are
    in series.  You will get MUCH better matching with two electric
    motors in series than you could ever hope to get with gas engines.
    If the torque constants of the two motore are equal, they will always
    produce the same torque since they will have to pull the same current.
    If the load on one is different, it will turn at a different speed,
    but so what!
    
    CHarlie
    

    Wiring them in parallel is equivelent functionally of wiring them
    separately to separate batteries. Wiring them in series makes for
    an electronic differential, more power efficient, but less stable.
    
    						John.

RE:< Note 387.179 by LEDS::WATT >

    Is the following correct?

        - Torque is proportional to thrust from the prop
            (As opposed to: RPM is proportional to the thrust...)

        - Current is proportional to the torque from the motor

        - Therefore, Current (not voltage) across the motor is
            proportional to the thrust from the prop.

    So, when you put two identical motors in series they may have
    different voltages across their terminals and may be turning
    different RPM's, BUT - since they both MUST be drawing the same
    current, they will both provide the same thrust.  (Also assuming the
    obvious - both motors have the same size prop...)

    To me, the first statement (torque ~ thrust) is the hardest to
    understand intuitively.  Clearly, there is a relationship between
    thrust, torque and RPM similar to Ohm's Law for current, voltage,
    and resistance.  Or, is it more like: power, voltage, and current?

    I dunno... Does anyone out there have a formula that relates prop
    thrust, torque, and RPM????

                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |            Happy Landings!
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|              - Dan Miner
     |_/      |___________|  |_________|  |
                      |       /           |     " The Earth needs more OZONE,
                      |      /                       not Caster Oil!! "    
                      |_____/

    re .-1 & props: there is a notes on props earlier in this conference
    
    also there is an article on props in this month Model Aviation that
    gives an equation that relates the power absorption of the prop
    (expressed in HP)..
    
    
    md 
    

    The easiest way to picture it is through power.
    
    The thrust multiplied by the aircraft velocity is the power.
    The torque multiplied by the RPM's is the power of the motor.
    
    A motor has a fairly linear torque/RPM graph, which means that the
    power has an upside down parabolic curve for any given voltage.
    Peak power occurs somewhere between full torque and full speed.
    
    Wiring the motor in parallel simply maintains seperate power curves
    for each engine. In a sense, the motors are coupled by drag.
    
    Wiring the motors in series creates a singular curve for both engines.
    The power from each motor is added and traced along a parabolic
    power curve. The series coupling creates a differential ( not unlike
    a standard mechanical differential ), where the thrust is constant
    for each motor, but the power can vary. Series motor also have the
    same kind of common mode coupling as parallel motors, namely, drag.
    
    Common mode coupling tends to make the aircraft go straight.
    You'll notice that there aren't many, if any, single engine flying
    wings around.
    
    Differential mode coupling tends to make the aircraft turn. Mechanical
    differentials are designed so that there is no preference for turning
    or going straight, that is why they're so popular in automobiles.
    On the ground, it's a pretty linear system. In the air, however,
    I have my doubts about linearity. Even in a single engine aircraft,
    there is common mode coupling because the thrust on one side of
    the prop is the same as on the other.
    
    My guess is that if you want the increased efficiency, you can get
    away with wiring the motors in series, but you'll have to have plenty
    of rudder. Whether your aircraft is designed for this is another
    question. If you wire them in parallel, you're pretty safe, it will
    make the aircraft more stable than it was designed for ( or exactly
    as stable as it was designed for if it calls for seperately supplied
    motors ). If you wire them in series, it will be less stable than
    it was designed for, and you should add more rudder and/or dihedral
    to compensate.
    
    						John.

    Dan,
    
    Some of the genius-types out there may correct me but I think what
    yer' seeing is surface-charge, i.e. the pack'll charge somewhat
    higher than rated voltage but dissipate to normal in a short time.
    
    The difference you note when measuring at the charger as compared
    to at the pack is, no doubt, line-loss from the charger leads. 
    Nothing's free and the resistance of the charger leads _will_ create
    some slight voltage drop.  Nothing to be concerned about.    

      |
      | |      00	 Adios,      Al
    |_|_|      ( >o
      |    Z__(O_\_	(The Desert Rat)

>    yer' seeing is surface-charge, i.e. the pack'll charge somewhat
>    higher than rated voltage but dissipate to normal in a short time.

    absolutely right !
        
>    The difference you note when measuring at the charger as compared
>    to at the pack is, no doubt, line-loss from the charger leads. 

    Right again !

    I often track my Kyosho autocharger (which is a delta-peak charger
    with volt and amp meters) with an external DMM because I have two
    chargers of the same type, and the voltmeter readings differ when
    they are connected to the same source.  I have observed the same
    things as you when charging, the explanation is quite simple, the
    official name used to refer to the phenomenon is "Charge Voltage".
    During a charge, the cell voltage is often higher than its rated
    capacity, if I remeber, its typically 1.4 to 1.6 volts per cell
    (as you know, the nominal voltage is 1.2v) and once the charge
    source is removed, the cell stabilizes at its normal, or just
    slightly above normal, voltage quickly.

    just as an aside, futaba has announced a new radio system for
    electric flight.  it consists of a lightweight receiver, 2 s133
    servos, a built in MOSFET speed controller, and a special Battery
    Eliminator Circuit that shuts down the motor when battery voltage
    drops below a preset limit.  With the motor load removed from the
    battery, voltage and current remaining are supposed to be
    sufficient to fly for 15 to 30 minutes.  I don't remeber the
    specified weight of the system, but since it has no Rx battery, it
    ought to be pretty light.

    RE:  Note 655.58:  
>               I have reviewed the considerable discussion on electrics 
>    in the conference, but would appreciate some conclusory recommendations
>    from those who do electrics on which planes you might recommend
>    for a beginner (beginning flyer, not builder): ie, which are
>    most stable, forgiving, and easiest to land for both gliders and
>    planes.
>    Thanks in advance/Bob Ross
    
    I think that any of the following would make good beginner's
    electric planes:

        Astro Flight Challenger with Astro Cobalt 05 geared
 (new:) Astro Flight Mini-Challenger COMPLETE with Astro Flight 035 geared
        Carl Goldberg Electra  (with Astro Cobalt 05 geared)
        Great Planes PT-Electric (with Astro Cobalt 05 Direct drive or geared)

    A friend of mine has an Astro Challenger and it is VERY easy to fly. 
    It climbs well, flies slow (easier for the beginner to react to),
    and glides well.  This would be my recommended first choice for a
    beginner.  It also is a very competitive electric glider that does
    well in duration events.

    I have not (yet) seen the new Mini-Challenger but expect I will see
    one at the KRC Electric Fun Fly in Penn. on Sept. 17-18.  I'll let
    you know how well it flies if I see one.  I've included it in the
    list above based on how well the full sized Challenger flies.

    Note that I do _NOT_ recommend using the standard motors that come
    with the Electra or PT-Electric kits.  Although they are fine for
    marginal performance for experienced pilots they are NOT (in my
    opinion) suitable for beginners.  The standard motors (usually car
    motors) allow only a very slow climb that is very close to stall
    speed.  As a beginner, this is a very dangerous situation that
    usually leads to the dreaded "stall-crash" premature landing.

    I'm sure Dan Snow (who likes to save pennies where he can :-) will
    argue that his stock PT-Electric flies fine.  I have to agree, but
    will maintain that he's no longer a beginner and can (usually) spot
    when a stall is about to occur and then avoid it.

    I think that it is well worth it to pay the price to get a top
    quality motor when getting into electric flight.  Besides the 3
    Astro Cobalt motors I have, I also have a Leisure LT-05 motor and
    the performance is MUCH better on the Astro Cobalts.  I probably
    will not use the Leisure LT-50 for anything else unless I build a
    plane that I can't afford a Cobalt for.

    Anyway, take my comments for what they are - my opinions.  I'll bet
    others will chime in with theirs...

                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |            Happy Landings!
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|              - Dan Miner
     |_/      |___________|  |_________|  |
                      |       /           |     " The Earth needs more OZONE,
                      |      /                       not Caster Oil!! "    
                      |_____/

    Dan,
    
    As long as the Challenger came up in conversation, I got a few
    questions about it. First of all, can you use standard size servos
    in it? I'd like to swap the flight pack from one plane to this one.
    
    Also, does it have a reasonably strong/well designed tail section?
    The horiz. stab on my Riser has been a constant source of annoyance.
    It's not very rigidly attached to the fuse, and it's so low that
    even a perfectly good landing can catch a tuft of grass and yank
    it loose. 
    
    Finally, how big is the wing? Does it come in two pieces? I don't
    have a lot of space in my car.
    
    Dave Walter
    

>    Astro Cobalt motors I have, I also have a Leisure LT-05 motor and
>    the performance is MUCH better on the Astro Cobalts.  I probably
>    will not use the Leisure LT-50 for anything else unless I build a
>    plane that I can't afford a Cobalt for.

Did your finger slip here or are the LT-05 and LT-50 different.
Looks like the LT-05 is wonderful and the LT-50 is no good?

Bye          --+--
Kay R. Fisher  |
---------------O---------------
================================================================================

    Dan,
    
    I really enjoyed your response about Not using the standard motors
    that come with most electrics like the Electra.  I have test flow
    2 Electras for friends of mine and I was almost to the point of
    saying "You call this a beginner kit..."  the performance with the
    car-type motors is just so marginal, especialy at this Colo Spgs
    Altitude.  You go out to fly these hoping there is some wind that
    you can throw it into.
    
    I would like to fly a electra that has a geared motor on it to see
    how it does.  I can imagine the difference.
    
    I still have one argument about Electrics in general is that they
    just fly like a brick, at least those are my thumbs impressing with
    the electra.  They are too touchy when transitioning between power
    and glide (someone said that this can be remidy by some down thrust
    with the motor.  You know the plane climbs under power, dives when
    you shut it off.)
    
    I really dont think that this is a good way to get into the hobby.
     I think it is similar to trying to learn to fly with a CG Eaglet
    with a .15 motor, they are just too marginal in my mind.  If you
    want a power trainer, stay at least with a .40 + motor and 50" +
    wing.
    
    I was wondering if they are starting to come out with some better
    performing electics like the one that is advertised in MA that has
    a Eppler 205 wing on it.
    
    I would thing that the best way to learn to fly in anycase is go
    and get a gentle lady and a up-start and a 4 channel radio.  This
    way I think you have a minimum investment (No fuel, glow battery,
    etc at this point) and you have something that is easy to fly, fun
    to fly and is easy for anyone to learn on, Even if they plan on
    transistioning to power.  I believe that most new flyers could be
    out soloing in one day.  Where it seems to be with power that you
    find an instructor and plan on spending a couple of months together.
    Not to mention the hassels with getting engines to run, etc.
    
    
    Dan, let me know your thoughts on "Is there something better than
    the Electra types?".  Does the gear motors make that much difference
    than the directs?  Are there more efficient designs availabe.
    
    Dan, How come the electra flys so rough when you fly it as a glider?:
    You know it wants to tuck under on turns, etc.
    
 

>    I would like to fly a electra that has a geared motor on it to see
>    how it does.  I can imagine the difference.

    Geared motors make a significant difference when flying slow
    aircraft, the lower speed, larger props make much more effecient
    use of the power available (its like getting more torque, the
    plane flies slower, but climbs better).
    
>    I still have one argument about Electrics in general is that they
>    just fly like a brick, at least those are my thumbs impressing with
>    the electra.  They are too touchy when transitioning between power
>    and glide (someone said that this can be remidy by some down thrust
>    with the motor.  You know the plane climbs under power, dives when
>    you shut it off.)

    Slow, heavy planes are more sensitive to proper setup.  My E-Cub
    flew like SH*T until I added down thrust (even with an Astro 05).
    Now it flies just great.  But before the thrust was added, it flew
    nose high, almost stalling, under power, but glided just fine.
        
>    Dan, let me know your thoughts on "Is there something better than
>    the Electra types?".  Does the gear motors make that much difference
>    than the directs?  Are there more efficient designs availabe.

    An Electra is comparable to other, similarly sized electric
    powered gliders.  The E-Cub flies quite differently, but not at
    all unmanagably (?).
    
>    Dan, How come the electra flys so rough when you fly it as a glider?:
>    You know it wants to tuck under on turns, etc.

    It probably did not have sufficient washout in the wings.


    I am, of course, not Dan, but Randy.  I have owned and flown a
    Kyosho Etude, Kyosho Valencia, AstroSport, Electra, E-Cub, and an
    Electra that I modified to have a longer wing and V-Tail, so I
    thought I was qualified to answer your questions.  I'm sure that
    Dan will have some more to say on the subject.


    Randy.
    
 

RE: .188 - .191

    Sorry I didn't reply sooner - work's been too busy...  ("Yeah, yeah,
    we've all heard that before, Dan.")   First of all, I agree with all
    that Randy said in .191, but lets take the other replies in order:

RE: .188  (Dave Walter)

    Yes, you can use standard size servos in the Challenger.  In fact,
    my friend's uses the standard Airtronics servos (which I think are
    slightly smaller that the Futaba servos??).  However, I'm going to
    use a Futaba mini receiver and S-33 microservos in mine since I plan
    to enter contests with it and want to get every second of flight
    time I can.  Also (as an experiment) I'm going to try my new Astro
    Cobalt 15 geared with 12 cells and need the space for all of those
    batteries.

    Yes, I think the horizontal stab is reasonably well designed.  As
    far as I know, Hogan (my friend) has never had a problem with his.

    The wing is big and is one piece.  I'm not sure of the dimensions
    but would guess something in the 76 inch realm.  (Look in the Tower
    cat. for exact dimensions.)

RE: .189 (Kay Fisher)

    Oops!!  Yes, that is a typo.  That should read "LT-05" in all
    places.  As far as I know there is no such thing as an LT-50. Also,
    to clarify a possibly vague wording;  the Leisure LT-05 gives _LESS_
    performance that an Astro Cobalt 05 by a noticeable margin. 

RE: .190 (CSC32::M_ANTRY   Mike?)

    I will agree that most of the "Complete" kits that come with
    car-type motors fly like bricks.  However, if you are willing to
    invest the money to get a good motor (like a cobalt), they _DO_ fly
    well.  Although the Electrostreak is by _NO_ means a beginner's
    plane, see notes 387.136 and 387.137 for Bill Lewis and Charlie
    Watt's reactions to my electric.  (I think Dave Hughes also made
    some comments about electrics after the DECRCM Fun Fly in 655.?)

    Your comments about the .15 powered Eaglet are right on the money. 
    I'll re-iterate and state it a little differently:  If there is a
    "40 sized" trainer from XYZ that recommends a .20 to .40 engine and
    the beginner buys a .15 or .20 "to save a few bucks"; how is that
    going to be in the long run?  Is he going to be happy that he saved
    the money or is he going to be p*ssed off that his plane flies
    terribly and quit the hobby?  I doubt he'll be happy.  

    My point is this:  Using one of the car-type motors that comes with
    one of the "complete" kits is like powering a 40 sized plane with a
    .15 or .20.  It may fly in experienced hands, but is NOT a good
    beginner's plane.  Pay the price for a good cobalt (or .40 engine in
    my analogy) and be rewarded by a plane that even a beginner can fly.

    I also agree with your comments about a > 50 inch wingspan.  That's
    part of the reason why my "best" recommendation is a Challenger
    since it is a motor glider.

> I was wondering if they are starting to come out with some better
> performing electics like the one that is advertised in MA that has
> a Eppler 205 wing on it.
    
    I think you're talking about the Airtronics Eclipse.  I haven't seen
    one of these, but I think it's probably very similar to the CG
    Electra.  I think you'd probably need to put in a cobalt motor but
    since I haven't seen one, maybe they do fly OK.

    I agree (yet again) that probably the best way to learn is with a
    glider.  On the down side however, is the fact that the flights are
    usually very brief and doesn't give the beginner much time to fly
    around.  On the up side, on a typical day you can get in 20 flights
    and thus 20 landings.  I also hate hassling with a high start. 
    That's why I recommend a GOOD electric glider - no high start to
    deal with.  I also think a motor glider is better than a (pure)
    glider because the beginner can go-around if he/she messes up the
    landing approach and usually 7 to 10 minute flights are possible
    even in the hands of a beginner.

> Dan, let me know your thoughts on "Is there something better than
> the Electra types?".  Does the gear motors make that much difference
> than the directs?  Are there more efficient designs available.

    The answers should be apparent, but here goes:  Yes, an Astro
    Challenger (or Electra) with a geared Astro Cobalt 05 is _MUCH_
    better that a stock Electra.  For motor glider type applications,
    Yes, a geared motor does improve performance.  (See Randy's comments
    also.)

    The application you do not (generally) want a geared motor is where
    you are trying to get high speed such as my aerobatic Electrostreak.

> Dan, How come the electra flys so rough when you fly it as a glider?:
> You know it wants to tuck under on turns, etc.

    I'm not familiar with what you're talking about.  All motor gliders
    I've flown (only a few) or watched, seemed to glide very nicely. 
    Maybe Randy's comments are the answer.  (I really have no idea...)

                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |            Happy Landings!
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|              - Dan Miner
     |_/      |___________|  |_________|  |
                      |       /           |     " The Earth needs more OZONE,
                      |      /                       not Caster Oil!! "    
                      |_____/

    I've seen several Electras fly just fine. Fritz Bein, the president
    of the Charles River Club has one, and it glides very well. He
    routinely gets 15+ minute flights on one charge. I saw another guy
    in the same club flying one. He obviously had much less experience
    than Fritz, so in low lift conditions it came down faster than the
    un-motorized gliders. But it's flying behavior didn't seem any worse
    than the other planes. I wonder if your friend's glider isn't trimmed
    properly, or balanced right, or maybe the wing is warped.
    
    Dave
    

RE: < Note 387.194 by JACKAL::SNOW >

    Gee Dan, I was beginning to wonder if you were still reading this
    notes file!  :-)  I've been beating on your PT-Electric just to try
    to get some response.  :-)  :-)

    I agree that your PT-Electric flies much better than your Pilgrim 1
    (modified Piece O' Cake) but once again, the Pilgrim 1 was way under
    powered for it's weight since it was powered by a car-type motor.  I
    think it would have flown great with an Astro Cobalt.  The Pilgrim 1
    performed about the same as (or slightly worse than) a stock
    Electra.  An Astro Challenger with a cobalt 05 will perform much
    better than the Pilgrim 1 or the PT-E.  

    I have to concede that the PT-E probably is much easier to build
    than a Challenger, but the original note stated that they were not
    beginner builders.  If the person were a beginner builder, AND were
    on a tight budget, I would have to agree that the PT-E is the best
    flying, easy to build, STOCK electric kit that I've seen and would
    probably be my recommendation.  

    As far as aerobatics, goes, I think the Challenger and the PT-E are
    probably about the same.  Both will do loops and rolls (with some
    strong persuasion).  The Challenger is also very stable and flies
    similarly to the PT-E as far as hands off recovery goes.

    I agree that the PT-E will build quicker and costs less than the
    Challenger & cobalt 05 combination I'm recommending.  However, the
    Challenger will perform better and give the beginner a larger margin
    for error than the PT-E.  

    I will say the the PT-E is probably the only stock kit that I feel
    performs adequately for a beginner.  A probable exception to this
    statement is the new Astro Mini-Challenger kit complete with cobalt
    035 for about $85 (?) mail order.  I hope to see one this weekend at
    the KRC Electric Fun Fly in Penn.  Full report early next week...

    (Yes, the PT-E is powered by a car-type motor.  It seems Great
    Planes has hit a magic combination of wing area, weight, airfoil,
    prop size, etc. in achieving a decent car motor powered plane.)  

    Oops - I'm almost forgetting one of the kits that is recommended in
    the magazines; the Leisure Amplitique (sp?).  Bob Kopski (the
    electric columnist in Model Aviation) recommends this kit as one of
    the few that fly well on the motor supplied.  (Although I'm not sure
    if the Leisure motor is considered a car or plane motor.  I'm also
    not sure if they sell kit and motor as a combination.)
                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |            Happy Landings!
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|              - Dan Miner
     |_/      |___________|  |_________|  |
                      |       /           |     " The Earth needs more OZONE,
                      |      /                       not Caster Oil!! "    
                      |_____/

    WOW!  The Ninth Annual KRC Electric Fly was a blast!!  Since this is
    a long report, I'll give you a sampler/summary up front to wet your
    appetite.  The unfortunate aspect of this report is that I was so
    busy watching everything, I didn't take the time to write down a lot
    of notes.  Thus, this report will be full of vague phrases like
    "about", "I think", and "I guess".  I'll probably have a lot more
    details to give when I get my photos back (over 100).  (The photos
    will "jog" the old dusty memory...)

    There were over 100 pilots with probably 130 to 150 electric planes
    there.  About 30 of these were scale ships with about 10 of these
    being scale competition quality.  One famous modeler, Keith Shaw,
    had the most impressive display of scale ships.  I've forgotten how
    many he had but I think he had 8 to 10.  (When I get my photos back,
    I'll be able to tell y'all exactly.)  One of them was a very nice
    full-blown "40 sized" Spitfire with retracts.  Another was a black
    and white biplane with a smoke system.  The aerobatic show that he
    put on was VERY impressive.

    Also, there were many exotic planes there: 2 ELECTRIC DUCTED FANS, 5
    or 6 fiberglass pattern ships, a few flying wings, a canard, a few
    deltas, an electric Black Baron Peashooter, 2 electric helicopters
    and an electric Simitar (sp?) - the plane that looks like it's
    horizontal stab and elevator are missing.  One of the most
    surprising planes there ("Gee, does that really fly on electric?")
    was a plain old Sig Kadet SENIOR that flew just like one powered by
    a .45 glow engine.  (Only about a 15 foot take off roll on grass.) 
    Of course, there were also a few dozen electric gliders there for
    the famous "All up - Last down" event.

    I have to go now, full report coming soon to a terminal near you.

                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |            Happy Landings!
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|              - Dan Miner
     |_/      |___________|  |_________|  |
                      |       /           |     " The Earth needs more OZONE,
                      |      /                       not Caster Oil!! "    
                      |_____/

    For those of you that have been planning to build an Electrostreak,
    but have been reluctant to scratch build, I have been told that
    Great Planes is now making a kit for it!!  

    Rumor has it that the newest Tower Hobbies quarterly flier
    advertises it.  (I haven't gotten my flier yet.)  If the rumors are
    indeed true (and I believe they are), I'll be ordering one ASAP for
    one of my winter projects and let y'all know what I think of the kit
    (lightness of wood, etc.) vs. the one I scratch built.

                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |            Happy Landings!
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|              - Dan Miner
     |_/      |___________|  |_________|  |
                      |       /           |     " The Earth needs more OZONE,
                      |      /                       not Caster Oil!! "    
                      |_____/

    Dan,
    	I'm definately going to build a 'streak and I would prefer a
    kit even though I could scratch it.  I have been very satisfied
    with Great Planes kits.  I'll order one in a flash as soon as I
    see the new catalog.  If you see it first, can you give me the
    catalog #. 
    
    Charlie
    

    Dan Snow just told me that they're selling it with a motor setup
    similar to the PT-E.  I'll resist the temptation of going on and on
    about how I feel about this setup vs. the Astro Cobalt 05.  (New
    readers, see earlier replies to this topic.)  Suffice it to say,
    I'll order mine without the motor (if available that way) and put in
    an Astro Cobalt 05 (or maybe even an Astro Cobalt 15!!).

    Hey Dan Snow (or anyone that has gotten the newest Tower flier);
    please post the details here.  In other words, the blurb from the
    catalogue, the prices with and without the motor package and the
    order numbers.  Thanks.

    Charlie, I'd like to inspect one of the kits before I order one. 
    Could I take a look at yours when it comes in??

                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |            Happy Landings!
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|              - Dan Miner
     |_/      |___________|  |_________|  |
                      |       /           |     " The Earth needs more OZONE,
                      |      /                       not Caster Oil!! "    
                      |_____/

    Just so happens I have mine with me!
    
    I believe you wanted info on the Great Planes Electrostreak???!
    
    Well here is the info out of the latest Tower Hobbies Flier........
    
    	Stock# TZ6818   Electrostreak/7-cel Turbo Battery/Kyosho Multi-
    		        Charger Combo..............................$119.97
    
    	Stock# TL1072   Great Planes Electrostreak w/Motor.........$ 54.99
    
    			Wingspan: 44"
    			Length: 39-1/2"
    			Weight: 35-42 oz.
    			Motor: Great Planes Gold Fire 550
    
    	Kit includes a 7x6 nylon prop, prop adapter, hinges, parts for
        optional landing gear and an extra-high performance Goldstar 550
        motor.
    
    	Required for operation are a 4 channel radio with speed control
        and three micro servos, and a 7-cell, 1200 mAh Battery.
    
    Ken
    

    Dan,
    	I'll order a kit as soon as possible and I'll let you know when
    I get it.  Don't want the Motor though.  I haven't seen my catalog
    yet.  My postman must be reading it.
    
    Charlie
    

    I got my catalog last night.  As I feared, there is no "kit without
    motor" option listed.  Guess I'll have to call them and ask if it is
    available w/o motor.  

    If it only comes w/ motor, I'll probably buy one anyway and use the
    motor in a glider or fun sport plane.  No, actually, I'll probably
    put it in that boat I've been wanting to build...

                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |            Happy Landings!
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|              - Dan Miner
     |_/      |___________|  |_________|  |
                      |       /           |     " The Earth needs more OZONE,
                      |      /                       not Caster Oil!! "    
                      |_____/

RE: < Note 751.4 by SACMAN::ROSS >  (What size fuse to use??)

    What I do to determine the "correct" fuse is go the the department
    store's automotive section and buy one of those assortment packs of
    auto fuses and then experiment.  I think most airplane setups draw 8
    to 20 amps, so I start with the 10 amp fuse.  In my systems (Astro
    Cobalts), this goes "pop" immediately and I move up to the 15 amp
    fuse, etc.  Use the smallest value of fuse that doesn't blow.

    Generally, the larger diameter and pitch props will draw more
    current.  Going from a 7-6 to an 8-4, you're increasing diameter
    (more current) but decreasing pitch (less current).  Off hand, I
    don't know of any way to determine if this will be more or less
    current other than trying it.

    In my systems:
        Astro Cobalt 05 w/ 7 cells, 7-4 prop   20 amp fuse
        Astro Cobalt 05 FAI (6 turn) w/ 7 cells, 7-4 prop   25 amp fuse
        Astro Cobalt 15 geared w/ 12 cells, 13-7 prop   25 (30???) amp fuse

    When you have determined the correct value, go back to the store and
    buy a box of the correct value.  Or, you could just buy some boxes
    of 10, 15, 20, 25 Amp fuses to start with.  You can always use them
    in your car!

                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |            Happy Landings!
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|              - Dan Miner
     |_/      |___________|  |_________|  |
                      |       /           |     " The Earth needs more OZONE,
                      |      /                       not Caster Oil!! "    
                      |_____/

    Congratulations Dan, I found a quote from you in this
    month's Model Aviation magazine from the AMA on page 156.
    
    Something about "the earth needing more ozone, not castor oil!"
    That sounds familiar!  And they printed the entire paragraph
    from you.  Good stuff!
    
    Glenn

    Dan,
    	I called TOwer to order a 'Streak and just as I suspected, they're
    backordered.  Ususlly, they get new stuff in the catalog and they
    aren't really ready to ship.  I left my order in, but they don't
    even have an expected ship date for it.  I'll let you know when
    it comes.  Too bad you can't order it without the motor.  I hope
    I get it in time to fly it this winter.
    
    Charlie
    

    
>>What I do to determine the "correct" fuse is go the the department
>>store's automotive section and buy one of those assortment packs of
>>auto fuses and then experiment.  I think most airplane setups draw 8
>>to 20 amps, so I start with the 10 amp fuse.  In my systems (Astro
>>Cobalts), this goes "pop" immediately and I move up to the 15 amp
>>fuse, etc.  Use the smallest value of fuse that doesn't blow.
    
    Dan, I wouldn't recommend this procedure for choosing the fuse
    value.  You might end up with a fuse that is just barely handling
    the current and ready to blow with the slightest load change
    (Murphy's law says that this will be immediately after a hand
    launch while headed toward some trees).
    
    I would pick a fuse that is at least a few amps above the maximum
    current of a given motor - you may be getting that by luck, but
    why risk it?  Isn't the main idea of the fuse to prevent fire or
    motor damage in the event of a short or stalled motor?  A few amps
    won't make much difference in that case.
    
    I'll get a 'streak kit too.  Anything to reduce the amount of building
    work is worth it to me!  If anyone hears of the kit being offered
    without motor I'd also be interested.  Hope Tower gets them in soon.
    
    Bill
    

    For LOTS and LOTS of information on electric flying, see note 387.*.

    As far as radios go, a good choice for electric flight is the Futaba
    4 channel 4NL sold with 2 of the S-33 microservos and the micro
    receiver for about $132. from the mail order places.  A good second
    choice is the same radio but with 3 of the "normal" sized S-48
    servos and normal receiver for about $100.  If you plan on staying
    exclusively with electric flight, I recommend paying the extra $ up
    front and getting the S-33 microservos. 

    One of the most important aspects of succesful electric flight is
    keeping the plane LIGHT WEIGHT.  Dan Snow has a Great Planes
    PT-Electric with normal sized servos and it flies pretty well. 
    However, I'd bet it would fly even better with micro servos.

    RE: clubs near Derry, NH.  I don't live around there but there is
    mention of some clubs somewhere in this notes file.

    By the way, as you'll see in the notes file, I fly a lot of
    electrics too.

                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |            Happy Landings!
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|              - Dan Miner
     |_/      |___________|  |_________|  |
                      |       /           |     " The Earth needs more OZONE,
                      |      /                       not Caster Oil!! "    
                      |_____/

    Well, just to add my two cents...

    ALL I fly is electric (unlike either Mr. Snow and Mr. Miner (I
    wasa gonna say Dan and Dan, but...) ).  I think that the PT
    Electric is a fine beginners plane.  You should definitely
    purchase a radio with Micro sized servos, not Standard servos.
    The relationship between weight and power needed to fly is not
    linear, a few ounces can make a very significant difference in the
    flyability of a plane, Stnadard size servos weigh as much as 1.5
    ounces more than micro servos.  You should also buy a radio with a
    250MAH receiver battery, instead of the typical 500MAH pack.  The
    reduction in weight far offsets the reduced flight time (really, a
    250MAH pack is probably good for 1.5 to 2 hours of flying).
    Futaba recently introduced a radio that has two micro servos and a
    built in FET speed controller.  If you can find one, and the price
    is within your budget, buy it, its the best possible choice.
    Barring that, choose the Futaba 4NL with the Micro package.  You
    will need to buy another servo (for on/off) or a speed controller.
    Also, buy a few motor battery packs.  It is a real drag to fly for
    10 minteus and then wait for another 15-20 before you can fly
    again.  Three packs are optimal, allowing you to fly without
    waiting for about 30 minutes.

    I've flown RC over the last 15 years off and on (lately more off than
    on) and recently found an old Astro .25 electric engine. I was
    wondering if there was a good sport airplane that this would match
    well. I figure I'll have to get new batteries but I like the idea of
    charge 'n go (which is why I bought this maybe 10+ years ago) I'd like
    something of a trainer/glider mix that would be a nice gentle flyer
    with enough power to get some reasonable height (but not vertical ;^)
    and yet be a good trainer to get my son onto the controls. I've got a
    couple of same vintage Astro .05s that I always found to be too heavy
    to carry my standard servos/rx/battery pack but I'm open to suggestions
    there. 
    
    My plan is that I can buy/build a kit for the motor I already have
    without too much spouse complaints IF I can use my standard size Kraft
    radio and existing motor. Once built, gee, the battery pack seems to be
    no good, how much were those new ones...

    Any 100 Inch glider would suit your purposes.  There are a number
    of planes that would fly with the 25 (just pick anything for a 20
    to 30 gas engine and lighten it when you build it) but such a
    plane will not be a good gentle flyer (a 25 size electric is going
    to need 18 to 20 HEAVY batteries).  Astro sells a Porterfield
    Collegiate (sp?) that would be a suitable choice for a geared 25,
    and, if I recall correctly, it has a 6' plus wingspan so its
    flight characteristics would be what you want.  The major
    manufacterers of Electric kits are Astro and Davey.

>    I've flown RC over the last 15 years off and on (lately more off than
...
>    without too much spouse complaints IF I can use my standard size Kraft
>    radio and existing motor. Once built, gee, the battery pack seems to be
>    no good, how much were those new ones...

Pardon me if I make some wrong assumptions here but if you haven't read
the notes on radios you should do so.  Also there are lots of notes about
transmitter batteries hidden in this file.

Expect to spend 20-40 bucks for a new transmitter battery and another 15-30
for the receiver battery.  BUT... there is a real good chance your Kraft radio
is no longer legal.  A frequency change and tuning will cost another $40.
The servos are probably not trustworthy after years of inactivity also.

Think seriously about purchasing a new radio and it you want it to be 1991
legal then get an Airtronics for somewhere between $150 and $300.

Bye          --+--
Kay R. Fisher  |
---------------O---------------
================================================================================

    I'll have to go back and read the radio sections. I'm reasonably new to
    the conference and I'm sure I missed a lot by setting seen and then
    going back to keywords I was interested in. I solved the battery
    problem years ago when I replaced all my packs with Radio Shack battery
    holders. I then loaded up with stock GE nicads and away I go. I can
    then replace cells that go bad and after a reasonable number of flights
    I pass them over to my kids for their toys. This also lets me fly as
    long as I like by popping fresh batteries into the packs at the field.
    Seemed like the best solution after having one of my TX cells reverse
    polarity. I always start a flying season with a fresh set TX and RX.
    
    Since I have a Kraft, 2 Heathkit, a World Engines Blue Max and lots of
    spare servos and the like I'd be interested in knowing what is the best
    solution so that I don't end up writing off $1000 in radio equipment.

    
>>    going back to keywords I was interested in. I solved the battery
>>    problem years ago when I replaced all my packs with Radio Shack
>>    battery holders. I then loaded up with stock GE nicads and away I go.
     
    This probably belongs in one of the radio or battery topics, but...
    I'd be cautious about using a battery holder and single cells
    in the flight pack and/or transmitter.  All you need is for some
    slight buildup of dirt, oil or whatever between the contacts to
    lose the connection.  I put single nicads in my son's old Futaba
    transmitter (the kind that used to take dry cells) and occasionally
    have to open it up and clean up the contacts.  I'd never use it
    for airplanes.
    
    I first thought that the radio manufacturers went to solder tabs to
    make it harder to replace cells (so you would buy their flight packs)
    but now I am pretty sure the new flight packs are more reliable than
    the old ones that had single replaceable cells.  You claim to have
    used this method with no problems for years, so my concerns might
    be unfounded.  Just thought I'd bring it up.
    
>>    Since I have a Kraft, 2 Heathkit, a World Engines Blue Max and lots
>>    of spare servos and the like I'd be interested in knowing what
>>    is the best solution so that I don't end up writing off $1000 in radio
>>    equipment.
    
    I don't think age should be a major concern for the servos, as much
    as the amount of use.  What frequencies are your systems on?  If
    they are still legal, then it seems like your best bet is to use
    them until 1991 and then upgrade.  The new systems have much cleaner
    and (I think) more reliable designs, particularly in the receiver,
    which is another argument for buying new instead of converting your
    old stuff to 1991 (which would cost quite a bit anyways!).
    
    I suggest any more radio discussions be taken up in a more appropriate
    topic.
    
    Bill

    The following information is from Astro Flight, Inc and is
    reproduced here without permission.  
    (There is no copyright notice on the sheets, either.)

    It is rather long but should be very interesting reading for anyone
    even remotely interested in electric flight.  Questions answered
    are:
        How long will I be able to fly on one charge?
        What size glow engine is my electric motor equal to?
        What does gearing do?
        What combinations of motor and model work best?

    At the end are some VERY useful tables comparing different Astro
    Cobalt systems and a table of standard (off the shelf) kits for glow
    engines and the recommended Astro Cobalt motor for the kit.

    My own personal comments will be surrounded with "[      -DGM ]".

    Due to how long this is, it's probably easiest to print it out and
    read it from paper.
                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |            Happy Landings!
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|              - Dan Miner
     |_/      |___________|  |_________|  |
                      |       /           |     " The Earth needs more OZONE,
                      |      /                       not Caster Oil!! "    
                      |_____/

                  ANSWERS TO YOUR FAVORITE QUESTIONS

    Electric flight has been around for more than a decade.  In many
    parts of the country, electric flight is still new and therefore the
    beginner doesn't have an experienced DEALER to ask when he is not
    sure what to do.  I have prepared these answers to the most often
    asked questions and hope that they will be of some help to you. 


        Question 1.  How long will I be able to fly on one charge?

    The flight time will depend on the type of model flown and the type
    of flying done as well as the capacity of the nicad battery used. 
    For example, ELECTRIC POWERED FREE FLIGHT MODELS are allowed a 25
    second motor run in AMA contests, but usually have no problem
    getting a 3 minute max.  If the motor run were not limited the model
    would be lost since it would climb out of sight.

    R/C ELECTRIC POWERED SAILPLANES AND OLD TIMERS are allowed a 45
    second motor run in AMA contests, but usually have no problem going
    for 7 minutes.  There is enough energy stored in our 900 mAhr
    battery for three or four climbs on one charge so that a total
    flight time of 25 minutes or more is common.  Modelers can expect
    similar flight times.

    R/C ELECTRIC POWERED SPORT SCALE MODELS are usually flown with the
    motor running for the entire flight.  An electronic speed control is
    used to control motor power.  You can expect flight times from 6 to
    12 minutes depending on throttle setting.

    R/C ELECTRIC POWERED AEROBATIC MODELS fly at very high speed and
    therefore require more power.  A larger and higher pitch prop is
    used to make the motor work harder so that the battery is almost
    depleted at the end of the aerobatic sequence.  This gives the pilot
    the maximum possible power to work with.  Since the aerobatic
    sequence takes about 3.5 to 4.5 minutes, the motor is usually loaded
    to discharge the batteries in this time.  The aerobatic sequence
    usually requires maximum power so use of an electronic speed control
    adds little to the flight time.

    R/C ELECTRIC POWERED PYLON RACERS use specially wound racing motors
    designed to extract maximum power from the battery in about 1.5
    minutes, because a ten lap race lasts little more than one minute. 
    These racing motors are set up to draw about 40 amps on the bench,
    but in the air the motor will unload to about 35 amps.


        Question 2.  What size glow engine is my electric motor equal to?

    When we at Astro Flight invented electric flight in the early 70's
    (U.S. patent 3957230) we tried to make our first motor equal in
    power to the then popular OS MAX-10.  In those days a MAX-10 would
    swing a 7 x 4 at 12,000 RPM.  We designed an electrical equivalent
    and called it the Astro 10.  It also would swing a 7 x 4 at 12,000
    RPM.  We named our other motors in the same way, for instance, an
    Astro 40 turns the same propeller at the same speed as a sport glow
    40.  Over the years the larger glow engines have improved and so
    have our electric motors, so power equivalence has remained.  Small
    glow motors such as the 020 and 049 sizes have not changed much, but
    our Astro Cobalt motors have tripled in power in 15 years so that
    nowadays out 020 is more like a Cox black widow 049 and the Cobalt
    035 is like a Cox TD 049.

    However, in general the electric motor is equal in size and weight
    to the equivalent glow motor with muffler and tank.  The battery
    however is three to size times heavier than normal fuel carried. 
    Allowance must be made for the extra weight of the battery if the
    model is to fly successfully.  Usually this means a slightly larger
    wing area is needed to carry the extra weight.  This can be offset
    in new designs by taking advantage of having no vibration and no
    need for fuel proofing to lighten the structure.


        Question 3.  What does gearing do?

    Gearing in a model airplane has the same functions as gearing in
    your automobile, it lets you pull a heavier load or climb a steep
    hill but at reduced speed.  In an airplane the propeller is the
    transmission, it converts power into thrust.  [ I think this should
    say the motor's gear box is like the transmission - the prop is like
    your tires.  -DGM ]  Astro gear boxes allow the motor to turn a
    larger propeller and therefore produce about 1.5 times the thrust at
    2/3 times the speed.  The net effect is that A GEARED MOTOR ACTS
    LIKE A FOUR STROKE MOTOR THAT IS ABOUT 1.5 TIMES ITS SIZE.  For
    instance, an Astro Cobalt 40 geared acts like a four stroke 60 glow
    engine.  Gearing is usually used in sailplanes and old timers to
    increase climb rate, and in larger scale models to achieve
    scale-like speed.


        Question 4.  What combinations of motor and model work best?

    Over the years two basic rules have evolved to describe successful
    electric models.  These rules specify GROSS WEIGHT AND WING LOADING
    needed so that our models will have acceptable climb rate and
    maneuverability.  It is the weight and wing loading that are
    important, the aerodynamics of the model is secondary.

    RULE OF THUMB 1.  THE WEIGHT OF THE AIRFRAME AND RADIO WILL NOT
    EXCEED THE WEIGHT OF THE MOTOR AND BATTERY.  

    This weight will insure quick take-off and rapid climb rate.  If
    your model comes out a bit heavy and weighs 1.5 times the weight of
    motor and battery, then it will still fly reasonably well but it may
    be a bit underpowered by todays standards.  If your model comes out
    very heavy and weights 2 times as much as the motor and battery it
    will be a real dog.  Jump on it with both feet and save yourself the
    embarrassment of crashing in front of your friends. 

    [ NOTE: In this context, "battery" refers to the recommended
    battery.  Obviously if you take an Astro Cobalt 05 and hook it up to
    a car battery, this will NOT power a 20 pound plane!!  -DGM ]

    RULE OF THUMB 2.  THE WING LOADING MUST NOT EXCEED THE MAXIMUM
    ALLOWED FOR THE PURPOSE INTENDED.  

    For example, a sailplane or old timer needs to thermal, this usually
    means a wing loading of 8 to 12 ounces per square foot.  A small
    sport model has no landing gear and is hand launched so I don't
    recommend exceeding 18 ounces per square foot.  Larger scale and
    pattern models usually will have landing gear and take-off from
    runways so these models usually have wing loadings of 20 to 24
    ounces per square foot.  Electric models with geared motors are
    usually larger and fly more slowly than electric models with direct
    drive motors.  In order to perform aerobatics, a model should fly
    2.5 to 3 times its stall speed.  This speed will insure the ability
    to do crisp maneuvers.  For smaller 05 and 15 size geared motors I
    recommend a wing loading of 14 to 18 ounces per square foot.  These
    recommendations are summarized on the next page.


     RECOMMENDED MODEL SIZES FOR ASTRO COBALT DIRECT DRIVE MOTORS

  Motor                     020     035      05      15      25      40      60

  Battery        (cells)      4       5       7      12      14      18      28
  Battery          (mAh)    800     800     900     900    1200    1200    1200

  Propeller               6 x 4   6 x 4   7 x 4   7 x 4   9 x 5  10 x 5  13 x 8
  R.P.M.                 10,000  12,500  14,500  16,500  10,000  11,500   9,000
  Power              (W)     50      90     125     200     300     450    1200

  Motor Weight      (oz)    3.5     4.5     5.5     7.0      11      13      20
  Battery Weight    (oz)    5.1     5.4     9.8    17.5      26      33      52
  Wiring Weight     (oz)    0.4     0.4     0.7     0.5     1.0     1.0     2.0
  System Weight     (oz)    9.0      11      16      25      38      47      74

  Radio Weight      (oz)      5       5       5       6       8       8      10
  Airframe Weight   (oz)      6       6      10      19      30      39      64
  Total Weight      (oz)     20      22      32      50      76      94     148

  Min. Wing Area (sq in)    200     200     240     350     500     550     850
  Max. Wing Area (sq in)    300     500     600     700     800    1400      - 



           RECOMMENDED MODEL SIZES FOR ASTRO COBALT GEARED MOTORS

  Motor                                      05      15      25      40     
  Gear Ratio                               2.21    2.21    1.72    1.72

  Propeller                              12 x 8  12 x 8  13 x 7  13 x 7
  R.P.M.                                  5,500   6,500   6,000   7,000
  Power              (W)                    115     185     280     425

  Gear Box Weight   (oz)                    1.5     1.5     1.5     1.5
  System Weight     (oz)                     18      28      40      50

  Radio Weight      (oz)                      5       6       8       8
  Airframe Weight   (oz)                     13      22      32      42
  Total Weight      (oz)                     36      53      80     100

  Min. Wing Area (sq in)                    400     450     550     700
  Max. Wing Area (sq in)                    600     700     900    1200


     [ For size and weight of battery, see Direct Drive table.  -DGM ]

        RECOMMENDED MODEL AIRPLANE KITS for ASTRO COBALT MOTORS

    Ace Mach None                   Cobalt 035 
    Ace GLH                         Cobalt 035 
    Ace Wizzard                     Cobalt 035 
    Airtronics Q-TEE                Cobalt 035
    Airtronics Monarch              Cobalt  05
    Airtronics Oly 650              Cobalt  05
    Airtronics Oly II               Cobalt  15 G  [ = Geared ]
    Astro Sport                Cobalt 020, 035
    Astro Viking                    Cobalt  05 G
    Astro P-68 Victor               Cobalt  05
    Astro Challenger                Cobalt  05 G
    Astro Porterfield          Cobalt 15 G, 25 G
    Astro Mini Challenger           Cobalt 035
    Ben Buckle Quaker               Cobalt  25 G
    Ben Buckle Playboy              Cobalt  40 G
    Ben Buckle Dallaire             Cobalt  40 G
    Ben Buckle Fokker VIII          Cobalt  15 G
    Champion Powerhouse             Cobalt  40 G
    Champion Hammer 20              Cobalt  25
    Champion Piper Cub              Cobalt  40 G
    Champion Stampe                 Cobalt  40 G
    Craft-Air Piece o' Cake         Cobalt  05
    Craft-Air Butterfly             Cobalt  15 G
    Davey Systems Le Crate          Cobalt  05
    Davey Systems Heron             Cobalt  05 G
    Davey Systems Robin             Cobalt  05
    Davey Systems Lucifer           Cobalt  05 G
    Flyline Robin                   Cobalt 020
    Flyline Great Lakes             Cobalt  15 G
    Flyline Fairchild 22            Cobalt  05 G
    Flyline Stearman                Cobalt 035
    Goldberg Jr. Falcon             Cobalt 035
    Goldberg Eaglet                 Cobalt  15
    Goldberg Electra                Cobalt  05 G
    Goldberg Eagle                  Cobalt  40 G
    Great Planes Cub                Cobalt  05 G
    Great Planes Minimaster         Cobalt  15
    Great Planes Trainer            Cobalt  05
    Great Planes Big H-Ray          Cobalt  25 G
    Glen Spickler Quickie           Cobalt  40
    GM Precision Bumble V           Cobalt 035
    Hobby Lobby Sr. Telemaster      Cobalt  40 G
    Hobby Lobby Pronto              Cobalt  15
    Hobby Lobby Telemaster          Cobalt  25 G
    Hobby Lobby Silentius           Cobalt  05 G
    Kyosho Cardinal                 Cobalt 035
    Kyosho Valencia                 Cobalt  05
    Kyosho Etude                    Cobalt  05
    Kyosho Zero                     Cobalt  05
    Leisure Playboy                 Cobalt  05 G
    Leisure Amptique                Cobalt  05 G
    Leisure Lanzo                   Cobalt  05 G
    Leisure Wasp                    Cobalt  05
    Marks Wanderer                  Cobalt  05 G
    Marks Bushwacker                Cobalt  15
    Micro X Taylorcraft             Cobalt 035
    Micro X Stinson                 Cobalt 035
    Midway Gnome                    Cobalt 035
    Midway Fast Eddie               Cobalt  05
    Midway Powerhouse               Cobalt  25 G
    Midway Electra                  Cobalt  05 G
    Midway Playboy                  Cobalt  25 G
    Midway Playboy Sr.              Cobalt  25 G
    Peck Prarie Bird                Cobalt  05
    Pierce Gemini MTS               Cobalt  25 G
    Pierce Ridge Rat                Cobalt  05
    Pierce Paragon                  Cobalt  40 G
    Pilot Baby                 Cobalt 020, 035
    Pilot Spitfire                  Cobalt  15 G
    Pilot Piper PA-18               Cobalt  40 G
    Pilot J-3 Cub                   Cobalt  15 G
    Pilot QB-15H                    Cobalt  15
    Pilot Decathlon 40              Cobalt  40 G
    Pilot Tomahawk                  Cobalt  15
    Pilot Tiger Moth                Cobalt  25 G
    RPM Snark                       Cobalt  05
    Robbe SF-36                     Cobalt  40 G
    Robbe Piper PA-18               Cobalt  60
    Robbe Parat                     Cobalt  05
    Robbe Windy                     Cobalt  15 G
    Robbe Robin 2000                Cobalt  60
    Sig Riser                       Cobalt  05
    Sig 1/4 Scale Cub               Cobalt  60
    Sig Smith Miniplane             Cobalt  15 G
    Sig J-3 Cub                     Cobalt  25 G
    Sig Kadet Sr.                   Cobalt  40 G
    Sig Kadet Jr.                   Cobalt  15 G
    Top Flite Wristocrat            Cobalt 035
    Top Flite J-3 Cub               Cobalt  25 G
    Top Flite Elder                 Cobalt  15 G
    Top Flite Elder 40              Cobalt  40 G

    I attended my first electric fun fly yesterday.  I'm one impressed
    spectator!  An advantage of being a spectator is that could spend
    the whole day observing and soaking up information without being
    distracted by my own planes.  
    
    The mildest things flying were about eight CG Electras with ferrite
    motors, but even they did well despite strong winds.  They also
    had a .25 and a .40 size fun scale P51Ds, flying wings, twins,
    Electostreaks, and much more.  This was just a small meet, so
    I can't wait till the Quakertown, Pa. meet in September.
    
    Bob Kopski was there with a couple of his new Skyvolts in both 05 
    and 15 powered versions.  They flew well, but he did have some trouble
    keeping consecutive loops lined up neatly.  He's got somebody lined
    up to produce the kit, so one version had some minor changes to
    the profile of the fuselage and the tail wheel linkage to reduce 
    production costs.
    
    In talking to Bob and some of the other experienced flyers, the
    consensus in this area is that an Astro 15 is the place to start.
    They just use whatever number of cells are required to get acceptable 
    performance.  They say a 15 with eight cells is supposed to be 
    equivalent to the 05 with seven cells.  
    
    I'm so pumped up, I can't believe I let my planes gather dust for 
    fifteen years...  

RE: < Note 387.214 by NYJMIS::BOBA "Bob Aldea" >
>                            -< They really do fly! >-

>    I attended my first electric fun fly yesterday.  I'm one impressed
>    spectator!  An advantage of being a spectator is that could spend
>    the whole day observing and soaking up information without being
>    distracted by my own planes.  
    
    Ahh!  Yet another flyer converted (or at least convinced :-).  That
    was part of the problem I had at KRC last year.  I was busy flying
    my Electrostreak #1 and missed some important stuff...

    Which Fun Fly did you attend yesterday?  I went to the one in Salem,
    Conn. yesterday sponsered by the R/C Propbusters.  (Report to follow
    later in the "So how was your weekend?" note.)

>    I can't wait till the Quakertown, Pa. meet in September.
    
    I went to this last year and will be going again this year.  It is
    _the_ electric meet to go to in the northeast.  I hope to see you
    there.  (At the beginning of Sept., I'll try to clue you in to what
    I'll be flying, etc. so we can meet each other...)

                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |            Happy Landings!
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|              - Dan Miner
     |_/      |___________|  |_________|  |
                      |       /           |     " The Earth needs more OZONE,
                      |      /                       not Caster Oil!! "    
                      |_____/

>>>    Which Fun Fly did you attend yesterday?  
    
    This was the "first annual" for a Burlington County, N.J. RC club.
    There are only two electric flyers in the club, but they had a good
    turnout from the surrounding area/states.

>    I can't wait till the Quakertown, Pa. meet in September.
    
    I've heard that its a great meet to visit, whether just to watch,
    compete, or pick up on some bargins.  If I can resist, I'll still
    be getting an education rather than buying.  Since they offer space 
    to camp, I'll probably stay over, although I'm close enough to drive 
    back and forth.  
    
    I have a flyer on the meet with a reservation form to join the 
    "Social" and dinner.  Actually, the "Social" is free and open to all, 
    but you must pay to attend the dinner.  Anyone who wants a copy, send
    me mail at NYJOPS::BOBA  
    
    Bob Aldea

    Dan and Bob-
    
    I was unaware of the Quakertown meet.  As I live only about 1-1/2 to 2
    hours from Quakertown (Harrisburg, PA), as soon as you post the date,
    I'm going to get it on my calendar!  Hope to meet you there.
    
    PS- SCOTT COX- It's not so far away for you, either! (3 hrs??)
    
    PPS- Hopefully, it won't be around the 20-26th... I earned DECathalon
    and really gotta go to Australia, instead! (Poor me, right?)
    
                             |                      
   \	       	         ____|____                      /   Regards,
    \________________________O_________________________/    Frank.
    

    Frank,

    The dates are September 16th and 17th.  Bob Kopski is the CD.  

            Bob Kopski
            25 West End Drive
            Lansdale, PA  19446

    Just drop him a note and he'll send you a 4 page flyer about the
    event.  The flyer also includes a reservation form for the dinner on
    the night of the 16th in addition to hotel/motel and campground
    addresses and phone numbers.  (Or, you can get a copy of the flyer
    through DEC snail mail from Bob Aldea - see note 387.216.)

    This Quakertown meet is more widely known as the "KRC Electric Fun
    Fly" (or maybe "... Fly In").

    If you have _any_ interest in electrics, this is an event you can't
    miss.  I'm driving about 8 hours (each way) again this year to
    attend for the second time.  I'm sure it'll be worth a 1.5 to 2 hour
    drive!  We'll be camping at one of the nearby campgrounds.

    See you there!
                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |            Happy Landings!
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|              - Dan Miner
     |_/      |___________|  |_________|  |
                      |       /           |     " The Earth needs more OZONE,
                      |      /                       not Caster Oil!! "    
                      |_____/

    
     I purchased a Goldberg Eagle II kit recently. It has the option
    of building for electric flight, which I would like to do. 
    The section describing how to do it tells me I need a Cobalt
    .25 electric engine and "THREE (3)" 1200 MA battery packs. 
    Now all the electrics I've seen have had only one battery pack
    because of weight problems. I don't understand why I need 3 packs
    (at 3 times the expense). I'm also concerned I'll need many more
    packs than that, if I don't want to make just one flight a day
    never mind how the heck am I gonna recharge 3 packs in the field.
    
    SO is this kit worth building electric or should I stay with gas
    and buy a real electric kit???
    
    Keith

My Astro .25 I had in the 70's used 2 packs in series. Doesn't surprise me.
Most of the electrics you've seen have probably been in the .05 range. I'm
bothered by the "once a day/week" stuff to since its such a bear getting the
packs in/out of the plane (you don't want them loose to shift in flight)

How 'bout it Dan Miner?

BTW: I still have my antique .25 Is this a viable engine with new batteries?
What size plane should I look for? I'm looking for a fun ship not VTO 
capabilities.

RE: < Note 387.219 by HIGHFI::ALLEN >
>>                            -< 3 Battery Packs??? >-


    Keith,

    Well, according to the information I have from Astro Flite: 
        a Cobalt 25 requires 14 cells (2 packs of 7 cells each) and 
        a Cobalt 40 requires 18 cells (3 packs of 6 cells each).  
    So, that means that the plans are wrong in either the motor size or
    the number of packs required.

    I suggest you print out note 387.213 and study the tables at the
    end.  According to the tables, a Goldberg Eagle (is this the same as
    the Eagle II???) requires a Cobalt 40 GEARED motor.  If the Eagle II
    normally takes a .40 sized 2-stroke engine, then I'd recommend the
    Cobalt 40 GEARED with 18 cells.  However, if the Eagle II normally
    takes a .20-.25 glow engine, then I'd use the Cobalt 25 GEARED with
    14 cells.  (Make sure the motor you buy is the "geared" type.)

>>    Now all the electrics I've seen have had only one battery pack
>>    because of weight problems. I don't understand why I need 3 packs
>>    (at 3 times the expense). 

    Most electric models are designed to be used with an "05" size
    motor.  This is roughly the same preformance as a Cox .049 glow
    engine.  Since the motors don't generate a whole lot of power
    (compared to a .25 or .40 glow engine), the model will be sensitive
    to excess weight.  This is true of BOTH an 05 electric or a .049
    glow powered model.  Of course, the .049 model does not require a
    1200 mAh battery pack and will be lighter by this amount.  :-)

    However, when you start using the larger electric motors, you can
    power a larger model that will be less sensitive to weight. 

    Now, to answer the question of "Why 3 packs?"...  As the electric
    motors get larger in size, they require more voltage to deliver the
    power that they are designed to do.  The only way to acheive this is
    by increasing the number of NiCad cells in the battery pack.  So, if
    you were to try to fly a Cobalt 25 (or 40) on only ONE 7 cell pack,
    you probably wouldn't be able to even taxi on a paved runway, say
    nothing about take off or try to fly.  The voltage would be too low
    for the motor and it would not deliver the power it was designed to.
    ALWAYS use the correct number of cells for the specific motor you
    have.

>>                              I'm also concerned I'll need many more
>>    packs than that, if I don't want to make just one flight a day
>>    never mind how the heck am I gonna recharge 3 packs in the field.

    You are right.  You should have at least 2 sets of flight packs so
    you can recharge while you are flying.  However, it is possible to
    get by with just one set.  For 2 packs, you can recharge them with a
    cheap charger in about 40 minutes (20 min. each).  Add another 20
    minutes for getting ready and flying and you could fly about once an
    hour with only one set of batteries.  At some fields, (when there's
    a lot of other flyers), you can only get your frequency pin about
    once an hour anyway.

    Regarding "How to charge 3 packs"...  There are 2 ways to do this. 
    The first way I mentioned above: just use a standard 6/7 cell
    charger and charge each pack separately.  The other way is more
    costly.  You must by a DC/DC charger from Astro Flite or Jomar (or
    other places) that will allow you to charge up to 28 cells at once. 
    The chargers typically cost about $100.  The advantage here is that
    you can charge up to FOUR 6 or 7 cell packs at one time.  This way
    you could have your plane recharged in 20 minutes regardless of how
    many packs you're using.
    
>>    SO is this kit worth building electric or should I stay with gas
>>    and buy a real electric kit???
    
    Well, as usual, that depends on a lot of factors:  money, piloting
    skill, and your willingness to wipe glow glop off your plane after
    every flight.  :-)   In this case, the first 2 are most important. 

    1) Cost: A Cobalt 40 geared motor with 3 battery packs will cost
       between $150 and $200.  (I think - I don't have a mail order cat.
       here.)  A powerful charger will cost $100.  This is compared to a
       $70.(?) O.S. .40 FP glow engine.

    2) Piloting skill:  Despite the fact that I'm the most
       "Pro-electric" guy around here, I'll admit right up front that
       the electric plane will be heavier and by definition, harder to
       fly.  If you are a 100% beginner, use a glow engine.  Kits that
       are designed from the beginning to be electric are designed
       lighter and thus, can be good trainers.  (The Great Planes
       PT-Electric is such a plane if you get a Cobalt 05 for it.)

    3) Glow Glop:  I first got into electric because I used to fly a Cox
       .049 powered model.  If you're ever run one of these engines, you
       will realize they spray oil all over EVERYTHING.  I got disgusted
       and decided to try electric.  Today, I fly both electric and glow
       engines (.25 and .40 sized currently).

    In case you can't tell, I always like to talk about electrics.  If
    you have any further questions, feel free to write them here, send
    me mail, or talk to me at the field some day!!!

                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |            Happy Landings!
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|              - Dan Miner
     |_/      |___________|  |_________|  |
                      |       /           |     " The Earth needs more OZONE,
                      |      /                       not Caster Oil!! "    
                      |_____/

RE:< Note 387.220 by TEKTRM::REITH "Jim Reith DTN 235-8459 HANNAH::REITH" >

>>I'm bothered by the "once a day/week" stuff to since its such a bear getting 
>>the packs in/out of the plane (you don't want them loose to shift in flight)

    Just make sure you let the packs cool down before recharging.  The
    way I do this is to take them out of the plane and put them into an
    ice chest I take to the field with my lunch and soda inside.  I do
    not use ice however.  Instead I use those blue plastic things that
    have the gel inside.  That way there is no danger of the battery
    packs getting wet and shorting out.

    I also agree that the "once a day/week stuff" is nonsense.  I've
    recharged many times in the same day and have had no problems with
    my SCR type Sanyo (and S&R brand) cells.  I'll admit the SCE cells
    MAY be better off with only once per day due to cell chemistry but,
    I don't really know.

    My rules for good battery use:

    1) trickle charge the night before use to equalize the pack

    2) always make sure the packs are at "room" temperature before
       charging.

    3) after every flight, let the motor discharge the pack to the point
       where the motor has slowed down to about 1/2 speed. 

    4) at the end of the day, leave the packs in this "mostly"
       discharged state, but don't run them down to 0 volts.

>>BTW: I still have my antique .25 Is this a viable engine with new batteries?
>>What size plane should I look for? I'm looking for a fun ship not VTO 
>>capabilities.

    Well, I'm assuming you mean a ferrite 25 (not cobalt).  I would bet
    that this performs roughly like todays cobalt 15 (or maybe 05). 
    Personally, I'd sell it at a club auction and buy a new cobalt.  I
    think you'll find the difference amazing.  The ferrite 25 is
    probably still fine, it'll just be heavier then a modern motor with
    the same power.  Look at note 387.213 and pick a plane where a
    cobalt 15 is recommended.

                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |            Happy Landings!
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|              - Dan Miner
     |_/      |___________|  |_________|  |
                      |       /           |     " The Earth needs more OZONE,
                      |      /                       not Caster Oil!! "    
                      |_____/

    About making an electric Eagle II:  I wouldn't do it for a trainer
    under any circumstances.  It will be too expensive and too hard to fly.
    A trainer should be light wing loaded and have ample power to get you
    out of trouble.  Wait to dabble in electrics until you are an
    accomplished pilot and then do so only if you are willing to do
    everything right.  You need to minimize weight and use the best motor
    and batteries available.  This = $$$$.  Electric planes generally
    suffer serious damage on hard landings due to the mass of the battery
    pack (s).  They tend to come right through the bottom of the fuse
    fairly easily.  Once you can land gently all of the time, then you are
    ready to fly an electric.
    
    Charlie
    

    
    Well Dan (Miner), you'll be happy to hear I've taken the first step
    toward an electric plane!  On Charlie's advice I bought an Airtronics
    Eclipse kit and received it today.  Very nice kit, looks like it will
    build in no time, but I doubt if I will be starting it before I get
    some other stuff out of the way (three other projects in various stages
    of completion).  But, it looks so good you never know!  Ordered a few
    micro servos from Sheldon's, and will be keeping my eyes open for a
    speed controller, battery, etc.
    
    I was looking for something I could fly in the field behind my house
    without bothering my neighbors, and this will fit the bill perfectly.
    The kit is pretty complete with motor, gearbox, folding prop, and spinner.
    For around $70 (was under $60 when Charlie got it but I missed the
    boat) it looks like a pretty good deal.  I think Anker has one too,
    and seeing it fly got Charlie interested.  I know I'll get bored
    pretty quick with sailplane performance, but hey, it's a good change
    of pace!
    
    Bill

    Charlie, I beg to differ about your commets that there are no good
    electric trainers.  I'll admit it's probably "best" for someone to
    start with a glow powered 40 or 60 sized trainer.  However, I think
    that an electric motor glider (with a COBALT motor) or something
    like a Great Planes PT-Electric (with a COBALT motor) does make a
    good trainer.  Flying electric DOES cost more up front.  However,
    you never need to go buy fuel!  :-)  :-) 

    Bill:  Welcome to the "electric club".  :-)  I thought for sure
    you'd build an ElectroStreak by now...  I guess I'll have to let you
    fly my "SuperStreak" (ElectroStreak with cobalt 15) when I get it
    done.  That'll get you excited about aerobatic electrics again.  :-)

                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |            Happy Landings!
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|              - Dan Miner
     |_/      |___________|  |_________|  |
                      |       /           |     " The Earth needs more OZONE,
                      |      /                       not Caster Oil!! "    
                      |_____/

    Dan, I agree that there are some "acceptable" electric trainers but I
    do not think that there are any really ideal ones.  I'll agree that an
    electric glider like the Electra or Eclipse could make a reasonable
    trainer, but flight times will be short until skill is developed in
    making turns without stalling it.  It will still not have the climbout
    performance of a gas powered trainer.  As you know, I'm not
    anti-electric but I do feel that it's easier to learn on a gas powered
    trainer.  After having flying and building experience, electric is an
    option worth considering IF you are willing to go first class on motor
    and battery.  Also, you need to choose a good electric plane and build
    it LIGHT.  The reduced power to weight of the electric power plant
    requires that you do everything possible to optimize performance if it
    is to be acceptable.  The lower performance means that you must know
    what you're doing to prevent stalling on takeoff (usually hand launch)
    since the engine is not going to haul you up at a 45 degree angle.
    Even the Electrostreak which is one of the better performers has to be
    allowed to accelerate after launch before you try to climb too steeply
    or it'l snap in a flash.
    

    My first 3 take-offs were at ninety degrees to the runway, and had 45
    to 60 degree climb-outs, thanks to my being ham fisted. My T60 with the
    OS SF61 didn't sweat it one bit.
    
    There after, I did 10 to 15 degree climb-out take-offs on my T60
    [as well as once on Charlie's Cowboy] consistently. I would hate to 
    think what an electric (top-of the line or no) would have done under
    similar circumstances, and will use my $$ to buy mores horses under the
    cowl as cheap insurance against re-building.
    
    Sorry Dan, but I sez beginner electrics is a bad idea.
    
    ajai
    
    PS. Hope we can still be friends, Dan! :-) :-)
    
    

    
    I think electric trainers are fine if you are willing to take 2 to 3
    times longer to learn how to "fly" and don't want to learn how to take
    off (that's why I qualified "fly" with quotes). I guess at the 2 to 3
    times because I think that's how the stick time will compare.
    Soooo, it's a tradeoff each person has to make, and chances are that
    if he/she is never going to go gas-powered then an electric trainer might
    be the best choice.  Otherwise I'd say go with the glow glop!
    
    Bill

    
                          My 2 Mah worth.
    
       I learned on an Electra, and then transitioned to an Electricub
    (first with a stock motor, then with a Astro cobalt motor.) I found
    the Electra to be fairly easy to fly, and slow to react (almost too
    slow to corrolate input with response) and the gliding capability
    gave you time to think about the landing. The flip side was that
    you need to fly the glider until it quits flying which can be
    unforgiving close to the ground.
        The cub was fairly easy to fly (faster) but required lots of
    room to climb with the stock motor (with the cobalt its fine.)
    
        Plus's of learning on electrics.
    
             - teaches the value of building light during construction
               which is valuable for any aircraft.
             - teaches you to fly the "wing" instead of the motor
             - lots of dead stick practice.
             - no Glow glop (borrowed from Dan Minor)
             - no glo motor to fuss with
             - quieter
             - more landing practice (for x amount of flight time)
    
        Minuses
    
             - Lack of flight time per flight, by the time you get
               comfortable, its time to land. 
    
             - marginal or zero takeoff capability. I have not personally
               had any difficulty with hand launching, but I have seen
               others crash during a hand launch.
    
             - Most flight is fairly close to the ground compared to
               glo powered (fewer mistakes high), this prevents the
               instructor from being able to get the plane to a safe
               altitude and handing it over before the battery runs
               out.   
                                                
             - less climb performance ( although it can be more than acceptable
               with cobalt motor.)
                                  
             - Nicad maintenance can be a pain.
     
    Although it sounds like I am down on electrics, its all I fly. I
    enjoy the quiet and convienence, and have recieved many compliments
    on my cub and the way it flys. Even though I am sold on electrics,
    I do not believe they make great trainers (although they can, and
    do work satisfactorily for the role).
                                         
    
                                       More like 1700 Mah worth,
    
                                             Dan Weier
    

    
     Welp..... First of all thanks for all the advise. I've decided
    from your input that the best thing to do is to build the Eagle
    II gas powered and use it as a backup to my PT-40 (which I have
    built but have not flown yet). From the sounds of it it looks like
    making this kit into an electric is like putting a 400 engine into
    a VW bug,,,, Ya I can do it but...... Well anyway I will build it
    gas, no problem, building is half the fun anyway. 
     Oh yea I checked out the kit and it does say to use a Cobalt .25
    with 3 1200 Mah battery packs. 
    
     Now My next question whats a good first electric plane to build????
    Hopefully I'll be building this over the winter and maybe have some
    gas powered flying time in. I've also noticed that there are MANY
    more gas kits than electric kits???
    
    Thanks Everbody
    Keith (Still on the ground but in one peice)

I cut this from the unix network rc file.

Bye          --+--
Kay R. Fisher  |
---------------O---------------
================================================================================
From: [email protected] (Wayne Angevine)
Subject: Electric Planes
Date: 18 Aug 89 16:45:00 GMT
Sender: [email protected]
 
 
   (This is an article I have been planning to write for some time,
   and finally got done.  I'll post it now, and from now on, whenever
   someone asks about electrics, I'll mail it to them.  If anyone
   has comments, please mail or post them and I'll update the article.)
 
 
	             Introduction to Electric Power
 
 
   Electric power is quickly becoming popular for model airplanes,
   and for a lot of good reasons.  It's quiet, and there's no mess 
   or starting hassle.  Many of you have seen me flying my electrics
   and have asked questions.  Perhaps this article will encourage
   some of you to build electrics this winter.  I'll mostly talk
   about setups that would be good for a first electric airplane.
   If you're good enough to build a Cobalt 60 powered pattern ship,
   you don't need advice from me.
 
   Incidentally, the myth that electrics won't fly at high altitude
   is just that.  I've had at least a couple of hundred successful
   flights both in Boulder and in Colorado Springs, which is even
   higher.  It may be easier to get away with some things at sea
   level, but it is not a problem here.
 
   Up front, we have to recognize that there is a fundamental 
   difference between electric and "wet" (fuel) power.  The difference
   is that wet power provides virtually unlimited power and duration.
   Electric power is a challenge because it forces the builder to
   make tradeoffs.  The batteries provide only a fixed amount of
   energy per unit weight.  You can have more power for a shorter
   time, or less power for longer, or you can add more weight.  
   If you are primarily interested in making long flights at high
   power with an airplane which is designed and built without
   regard to weight, electric is not for you.
 
   That said, it is certainly possible to build high-performance
   airplanes with electric power.  Electric power is used today
   in pattern competition and pylon racing.  The climb rates of
   models designed for limited-engine-run events are phenomenal.
   There's a lot of fun to be had with electrics.
 
   There are four basic elements to an electric airplane; the 
   batteries, motor, controller, and airframe.  I'll talk about 
   them in that order.  Then I'll talk a bit about propellors
   and chargers.
 
   Batteries
   ---------
   The modern nickel-cadmium (NiCd) battery is the item that made
   the electric airplane practical.  The right NiCds can be charged
   at 10 amps, discharged at 30 amps or more, and will do it for
   hundreds of cycles.
 
   There are four sizes of cells in common use for electric power.
   The smallest is the 800 milliamp-hour (mAh), followed by 900,
   1200, and 1700 mAh sizes.  The 1200 mAh cells are used by R/C 
   cars.  Most electric fliers use Sanyo cells.  The 900 SCR and 
   1200 SCR cells provide the highest discharge rates and are most
   tolerant of fast charging.  I don't recommend use of the 800 mAh
   cells, since the 900s have a better power-to-weight ratio and
   weigh only slightly more.  The 1700 SCE cells can't tolerate
   high charge and discharge rates.  They will provide long duration
   in low-power setups.
 
   The battery pack is made up of four to 28 cells.  The most common
   size is six or seven cells.  Since this is the size used by R/C
   cars, packs and chargers are easily available.  Larger packs
   will fly larger airplanes, though, so don't rule out larger
   systems.
 
   Motors
   ------
   Motors fall into three basic categories; can, replaceable brush
   ferrite, and cobalt.  A can motor has the brushes inside.  They
   can't take much current, wear quickly, and are inexpensive.
   The Mabuchi 540 is the most common can motor.
 
   A replaceable brush ferrite motor is a step up.  Leisure, Yokomo,
   and Kyosho make them, among others.  In the 6-cell size, they 
   are often sold as upgrades for R/C cars.  They come in a variety
   of winds and with or without ball bearings.  Astro Flight makes
   ferrite motors in larger sizes.
 
   The term "cobalt" refers to the magnets in the motor.  Cobalt
   or other rare-earth magnets are more powerful for their weight
   than ferrite magnets, which makes for a lighter, more powerful
   motor.  Cobalt motors also have higher-quality construction,
   larger brushes, and larger price tags.
 
   Motor sizes are most often stated in terms of wet engine sizes,
   like 05 or 40.  An 05 motor puts out about the same power as
   an 049 wet engine, but 05 motors vary by a factor of two or more
   in their power handling capability, from 75 to 150 watts.  A 40 
   Cobalt motor can put out from 450 to 600 watts.  Since one 
   horsepower is 750 watts, a Cobalt 40 puts out about as much as
   a mild wet 40 engine.
 
   Controllers
   -----------
   The simplest way to control the motor is with a servo-operated
   switch.  I strongly recommend an electronic speed control for
   anything other than a glider.  An electronic control allows you 
   to throttle back to conserve battery power.  A good one is also 
   more efficient than a switch.
 
   Airframes
   ---------
   The key to a successful electric airplane is weight.  The less,
   the better.  This means that most ARFs are out (many of them are
   too heavy for wet power at this altitude).  Most kits will need
   some modification.  In general, a good airframe for electric
   power will have lots of wing area and lots of open structure.
   The style of construction used in gliders and old-timers produces
   incredibly strong, light airframes.
 
   To give some idea of the variety of electric possiblities, I have 
   flown a Hobby Horn Sensoar, a Kyosho Etude, an Astro Viking, and 
   a Royal 40T, all with electric power.  The Sensoar is a very 
   inexpensive and lightweight glider.  The Etude is an ARF with foam 
   fuselage and built-up wing, specially designed for electric power.  
   The Viking is an old-timer.  The 40T is a built-up ARF designed 
   as a trainer for 40 wet power.
 
   In the Etude, I used an upgraded motor (the Kyosho 360PT) and a
   Jomar speed control.  I could routinely fly six minutes with some
   aerobatics.
 
   All of these planes except the 40T were designed for six or seven
   cells and an 05 motor.  In the 40T, I use an Astro 40 Cobalt and
   the same Jomar controller.  I have two battery packs of 21 cells
   each, one of 1200 mAh cells and one of 900 mAh cells.  I get four
   to five minute flights while trying to save some power for a go-
   around.  The climb-out at full power is quite impressive, and the
   plane can do loops and rolls.  I could have built a similar plane
   as much as a pound lighter, but I wanted something quick.
 
   There are lots of good kits available for 05-size electrics.
   If you want a larger power plant, you'll probably have to modify
   a kit designed for wet power.
 
   Propellors
   ----------
   A larger propellor causes an electric motor to slow down and
   produce more power.  This is different than the behavior of a
   wet engine, which usually produces less power at lower RPM.  
   The choice of propellor size and style is critical to the
   performance of the electic airplane.  Too large a propellor
   will cause the motor brushes to wear out prematurely, and give
   short motor runs.  Too small a propellor will cause sluggish
   performance.  In general, electric motors seem to do best with
   props having thin, broad blades.
 
   Gear drives are also popular.  Since electric motors run smoothly,
   a simple, lightweight gear drive can be used.  This allows the
   use of a larger prop, which is more efficient since it has a
   larger disc area.  In general, a geared motor can fly a larger
   airplane with a lighter wing loading than the same power plant
   without the gear drive.
 
   Chargers
   --------
   Six or seven cell packs can be charged from a car battery by any
   of a large number of chargers available at any hobby shop.  Larger
   packs need a charger which contains circuitry to boost the voltage
   of the car battery.  These are more expensive.
 
   I have several packs, and I slow-charge them at home.  I don't
   have a field charger for my larger packs.  I just put up a couple
   of flights and then go home.  If I didn't live so close to the
   field, I'd probably get a charger.
 
   The technology of charging could be the subject of another entire
   article, and there are as many opinions as people doing it.
 
   Summary
   -------
   What you should get for a first electric depends on how much
   experience you have and how serious you are about electrics.
   If you're experienced and serious, get a 25 or 40 Cobalt and
   build whatever you want to fly.  If you're a beginning flier,
   I'd recommend a powered glider such as the Airtronics Eclipse
   or the Goldberg Electra, the Leisure Amptique or one of the 
   old-timers.  Most of the ARFs are not for beginners - they're 
   too heavy and fly too fast.  You don't need a cobalt motor to
   have fun with a lightly loaded plane.  One of the replaceable-
   brush ferrite motors would be a good choice.
    Wayne Angevine		Internet: [email protected]
    Daisy/Cadnetix Corp.	UUCP: cadnetix!waynea
    5775 Flatiron Pkwy.		      {uunet,boulder,nbires}!cadnetix!waynea
    Boulder, CO 80301

RE:  <<< Note 387.231 by HIGHFI::ALLEN >>>
>>                         -< Good First Electric Kit ? >-

    Also, see notes 387.187 to 387.195 for a discussion of what some of
    us think are good beginner's electric kits.  I would like to add one
    more to my list (if I didn't already in 387.195?): 

        The Leisure Amptique

>>     Oh yea I checked out the kit and it does say to use a Cobalt .25
>>    with 3 1200 Mah battery packs. 

    This looks wrong to me.  Astro Flite recommends 14 cells with the
    Cobalt 25.  That would be TWO packs of 7 cells each (not 3 packs).
    But than again, maybe the Eagle II instructions are thinking of
    using three packs of 6 cells ( = 18) which is 4 extra cells (and 4.8
    extra volts).  I'd still start with 14 cells.

    By the way - I think it's wise to make the Eagle II a glow powered
    plane.

                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |            Happy Landings!
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|              - Dan Miner
     |_/      |___________|  |_________|  |
                      |       /           |     " The Earth needs more OZONE,
                      |      /                       not Caster Oil!! "    
                      |_____/

>< Note 387.237 by TEKTRM::REITH "Jim Reith DTN 235-8459 HANNAH::REITH" >

>Most of the Electric plane engines draw 20 to 40 amps so the number of panels 

Jim - I've had this nagging question about electrics and since you
just reminded me of it I'll let all you EEs give me a hard time.

I'm about be become electrified and I can't figure out how in the world
you measure the current your motor draws.  Current I can measure but
nearly every meter I see only goes up to 10 Amps.  I just purchases
a new Radio Shack DVT (they are now on sale for $40 and have been $60
for years (cause their new portable top of the line can measure capacitance
and has a transistor tester built in Soooooo the next model down is on
sale)).

Anyway - how can I measure 20+ Amps?
Seems I must be missing something obvious cause you guys seem to
be doing this all the time.  I could try to calculate the Amps
given the voltage and the resistance of the motor but I'd think
the resistance of the motor would be different under load and also
would depend on how hot it was?

After you tell me how to measure current then I assume that
I should be able to charge a battery and run the motor and write down
the current. 

Then keep doing this till I see the current reading stabilize
and then I will know the motor is broken in - right?

Bye          --+--
Kay R. Fisher  |
---------------O---------------
================================================================================

    Kay,

    Current measurment is easy for me, I use a Clamp-on Ammeter.  It
    measures current by detecting the magnetic field generated by the
    current flow through the wire, which runs through what is essentially a
    toriodal trasnformer attached to the meter.  I think the range on my
    meter is .1 to 150 amps.

    If you don't have access to a clamp on, you could look for a Shunt.
    Another possibility is to go down to ADAP, and buy an inexpensive
    automotive ammeter (the kind you mount in a dashboard).  This ought to
    give you 25 to 30 amps on the scale, and more than satisfy your needs.

    A Cobalt .05 size motor, on 7 cells swinging an 8-4 prop will draw
    around 18-20 amps.  A ferrite motor under the same circumstances will
    draw 3 to 5 amps less. 

    If you're concerned about break in on your motor, all you have to do is
    run the motor, *WITH NO PROP*, at 1/2 its rated voltage, for about an
    hour.  This is rule-of-thumb, of course, but is pretty widely accepted
    as a most reliable means.  Typically, you can run an .05 size motor on
    2 D cell batteries until they're dead, and you're all set. 

    If you're using an Astroflite motor, don't bother with break in.  They
    come, already bench run for 1 hour, from the factory.

>    Current measurment is easy for me, I use a Clamp-on Ammeter.  It
>    measures current by detecting the magnetic field generated by the

I'll bet that puppy cost a couple of bucks.

Bye          --+--
Kay R. Fisher  |
---------------O---------------
================================================================================

    Kay brings up an important point!  It's not easy to measure the load
    current on an electric.  You can't afford to add any significant
    resistance to the circuit (ammeters have resistance) without affecting
    the measurement.  For example, a .1 ohm ammeter would drop 1 volt
    across it for each 10 amps of current.  If you only have 8.4 volts (7
    cells) to start with, one volt lost is a big difference.  This is why
    it's so important to use 14 guage wire and make GOOD connections.  The
    proper way to measure current in the multi amps range is with a
    calibrated current shunt.  THis is a resistor of known very small
    value.  Usually, it is made out of a hunk of wire.  You attach a
    voltmeter to the shunt and put current through it.  The voltmeter
    measures the voltage across the shunt and by using ohm's law (I=E/R),
    you can determine the current.  For example, if you have a .01 ohm
    resistor, you will read 10 mv per amp.  At 30 amps, you would have 300
    mv drop across the shunt.  This is about as much as you would want to
    lose in a low voltage DC circuit.  The shunt is inserted in series with
    the motor circuit and the voltmeter is attached across the shunt.
    If anyone wants to make and calibrate one of these, give me a call or
    send mail and I'll explain how to do it.
    
    Charlie
    

>    If anyone wants to make and calibrate one of these, give me a call or
>    send mail and I'll explain how to do it.
    
Charlie - consider this your mail.  Why don't you tell us all right
here how to create and calibrate a shunt.  This seems to be the
right note to put that type of info into.

I can't accurately measure less than one ohm I don't believe with my
present meter.

Bye          --+--
Kay R. Fisher  |
---------------O---------------
================================================================================
    

    Kay,
    	I'm off to a meeting, but so that I don't forget, I'll stick in a
    quick Shunt Cal method.  The problem with calibrating a shunt is that
    the resistance is very low.  (should be << .1 ohm)  You can figure
    what resistance you want by the range you want and how much voltage
    you're willing to drop across it.  I would go for about .25 volts drop
    maximum so as to not affect the circuit too much.  If you go for .25
    volts drop with 25 amps for example, the resistance wants to be
    
    
    .25/25 = .01 ohm.  That ain't much, is it!  Now go to a wire table for
    copper wire and find out the resistance per foot of various wire sizes.
    (I haven't done this yet for this example)  Pick a wire guage that
    gives about .01 ohm in a foot or less.  Solder your voltmeter leads
    to the ends and attach the connector that you will use to hook the
    shunt to the circuit.  Now, to calibrate, borrow a current meter that
    is good to at least 10 amps.  Put the meter in series with your shunt
    and hook up your voltmeter to the shunt.  With a power supply and a
    load (motor, resistor, etc) get the current in the circuit to be up
    toward 10 amps.  Read the current meter and the voltage on your
    voltmeter that is across the shunt.  You now want to divide the
    voltmeter reading in volts by the current meter reading in amps to get
    the shunt calibration constant (volts per amp)  Use a foot of wire so
    that is doesn't get hot and change in resistance.
    
    Have Fun!
    
    Charlie
    

>    for ease_of_operation.  Currently under consideration for my first
>    plane are the FLASH and the VALENCIA.  From my reading, I have managed

If you read all the notes in here you will get the distinct impression
that electric Kyosho products are NOT recommended.  We don't believe
you will be successful it you start with these products.  

>    to get the impression that the FLASH is the 'hotter' of the two.
>    Is that correct?  My heart is not set on either of these models

Yes - the FLASH may rise off the ground and crash whereas the Valencia 
will never leave the ground.  Since your now racing cars consider this.
The Kyosho electric planes are to electric planes as the Radio Shack
electric cars are to electric cars.

>    and I am totally open to suggestions as to make, model, and type,

The great planes electric CUB is probably a good start in electric but
be prepared to invest in an Astro Cobalt motor and throw away the one
that comes with the plane.  There is a note devoted to electric flight
which you should read.  Dan Weir and Dan Minor can both help you on
details of getting started in electric flight.  Dan Weir had success
with an electric Cub and San Minor is our resident electric expert.

>    but...I would really like something that is 'stunt capable' while
>    not offering to much resistance to the learning novice.  Am I asking
>    to much? :)

Yes - that is contradiction in terms.  The stunt capable electric plane
you want is a great planes electrostreak - but you will have to put a
summer on the cub before you can handle this.  Again - give Dan Minor
(our electrostreak expert) a ring.

It sounds like your hooked - check out the entries in this file devoted
to beginners and send in your AMA membership now.

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################
                                                 
    

RE: Note 1128.0 by MKFSA::GOULD 

    Fred,

    All of Kay's comments in .1 are good advice.  (Despite the fact that
    he spelled my name wrong... TWICE!)   :-)  :-)

    First and foremost - DON'T BUY ANYTHING FROM KYOSHO!!  I have NEVER
    heard anyone say that they have been pleased with the performance of
    a Kyosho plane.  Some of them just don't fly at all.

    Also, you do not want anything that claims to be aerobatic.  The
    most gentle trainers will still perform some simple aerobatics
    (loops & rolls) and will also be gentle enough to allow you to keep
    it in one piece for more than one flight.  Wait for your second or
    third plane to get that "all-out" aerobatic plane.

    Some planes that are good electric trainers are:
        Great Planes PT-Electric  (*NOT* the ElectroStreak - I've owned 3)
        Leisure Amptique
        Astro Flite Challenger (motor glider)

    As you will see when you read some of my notes, I am a very strong
    advocate of using cobalt motors in place of the cheap "car-type"
    motors that come with most kits.

    See note 387.192 and some of the notes before and after it for more
    discussion on beginner's electrics.

    Whatever you decide, make sure you join the AMA before you fly and
    BE SURE TO HAVE AN INSTRUCTOR!  No matter how hard you think flying
    will be, it's always at least 10 times more difficult than that...

    If you live somewhere near central Mass., I'd be happy to help you
    out on your first flights.

                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |            Happy Landings!
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|              - Dan Miner
     |_/      |___________|  |_________|  |
                      |       /           |     " The Earth needs more OZONE,
                      |      /                       not Caster Oil!! "    
                      |_____/

    Fred,
    	Sounds like you're just about hooked!  I have taught several guys
    to fly, and I can't say enough about how important it is to get the
    right trainer.  It can make the difference between success in a few
    short sessions or months of frustration.  First off, there are a couple
    of electrics that can be used as trainers, but I don't recommend an
    electric trainer for several reasons:
    
    1.  You get short flights.  The instructor uses up most of your battery
    climbing to altitude and you only get a minute or two of stick time
    before it's time to land.  Then you have to recharge (45 minutes if you
    let things cool down unless you have more than one battery) and wait
    for your instructor to free up again.  With a power plane, you can get
    15 minute flights at half throttle, no problem and the climbout can be
    very quick.
    
    2.  You don't have enough power.  I like to have extra power to get out
    of trouble, especially on bad takeoffs.  This is not good practice, but
    it sometimes saves an airplane.  A good .40 sized trainer can pull
    almost vertical without stall/snaping into the tarmac.
    
    3.  You can't learn to take off.  Most electrics will not take off
    except from a paved runway and some of the better ones don't even have
    wheels.  This means hand launching.  Hand launching is not easy for a
    beginner and the instructor can't do much if things go wrong.
    
    4.  Even a minor crash (no relation to Dan) usually does some damage to
    an electric because of the weight of the battery and the light weight
    construction.  I'm not saying a trainer should be crash proof, but most
    of the good gas jobs like the Eagle II, PT-40, and the FirstStep(Local
    favorite) can take a hard landing with minimal damage.  The battery
    usually acts like a battering ram and exits the bottom of the fuse on a
    dork landing.
    
    	I like electrics but I really feel that they are best suited for
    pilots with some experience under their belts.  As a second airplane,
    after you have mastered takeoffs and landings, they are great!  Then,
    you get the whole flight to yourself, you know how to land on the
    runway, gently (most of the time), and you don't haul the nose up at a
    45 degree angle and stall the sucker on launch.
    	Good electrics have to be very well designed, with the right motor,
    battery, and prop combination.  You start with a BIG power to weight
    disadvantage with a battery vs the stored chemical energy in your fuel.
    I would guess that the "Watts per oz" stored in your fuel tank is
    almost two orders of magnetude greater than those stored in your nicad
    pack.  I spent a year working on full size electric cars so I have
    first hand experience in battery "go power".  
    
    Enough Rambling - Hope you're still hooked!
    
    Charlie Volt-Ampere
    

    
    	Thought I'd add some info to this note....it's the least I can do
    for all the info I got out of RC notes.
    
    	I completed my PT Electric early this summer.  The completed weight
    was 40oz with a stock(came with the kit) 05 motor, dave brown lite
    wheels, monocoat covering and a Futaba 4 ch attack radio.  The radio
    receiver has a BEC circuit and integrated speed controller so I didn't
    need a seperate Rx battery.  The plane uses 2 S-133 servos.  
    	I followed an earlier suggestion about enlarging the battery 
    compartment and shifting the batteries to achieve a proper CG without 
    adding ballast...It worked great!    The batteries are velcroed in and
    they have never moved.  Another great "notes" idea.  
    	Another change to the plane came about as a result of a
    conversation with Dan Snow.  He suggested that I beef up the nose of the 
    a/c just behind the motor.  A few pieces of 1/8 x 1/4 spruce epoxied
    to the inside of the motor compartment worked out great.  I haven't
    damaged the nose yet although I have had a few "rough" landings.  
    	With the set-up described above, the a/c would ROG off the dirt
    runway of a softball diamond(between home and first base).  I will
    admit that the takeoffs were very close to marginal.  If any of you
    have ever seen the old WWII movies of B-25s launching from the deck of
    the carrier Hornet on their raid of Tokyo, then you know what marginal 
    is.
    	The a/c would do mild aerobatics and could be looped from a shallow
    dive.  With 1/2 in of washout, I never stalled the model and turns were 
    somewhat coordinated.
    	Then my birthday came and I ended up with an Astro Cobalt 05 direct
    system.  I just have to verify everything that has been said about
    those Astro motors.  The A/C loops from level flight, it will ROG of the 
    same baseball diamond in 2/3 the distance and weighs less to boot!  
    My only complaint is that I loose just a bit in the flying time due to
    the battery size....7 cell 900 ma vs 6 cell 1200 ma.  However, the 
    performance improvement is well worth it.
    	In general, I believe that the PT electric is an excellent kit.  It
    goes together easily and well, flies nicely and can benifit from the 
    minor improvements mentioned in this note.   If you add an Astro motor,
    well, then it's a real nice model.
    	When this a/c is retired, the Astro 05 motor will go into the Astro 
    Sport that's on the bench.  I figured that I'd try a model designed by
    Astro for one of their motors.  The Astro Sport is a 36 in high wing sport
    job.  This kit is not for a beginner!  Although the plane is very
    simple, the instruction(sic) leave a lot to be desired.   My plans are
    to build the 2 channel version and adding either floats or skis.....some 
    people just have to be different.
    
    
    						regards
    
    						Bob
    

>    job.  This kit is not for a beginner!  Although the plane is very
>    simple, the instruction(sic) leave a lot to be desired.   My plans are

    Characteristic of Astro kits.  I've built (and DEMOLISHED) the Astro
    Sport, and am in the process (reaaaalll slowwwww) of building the
    Partenavia P-68 twin.  With both kits, the plans S*CKED.  You've got to
    know what your doing to put these kits together right (I know what I'm
    doing, and I still had a few minor screwups).

    I'll have to agree about the quality of the instructions for Astro
    Flite kits.  They are less than ideal to say the least.  :-)

    It's *GREAT* to see so many new people getting into electric - keep
    it up.  (No pun intended - but you can imply one if you like...)

                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |            Happy Landings!
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|              - Dan Miner
     |_/      |___________|  |_________|  |
                      |       /           |     " The Earth needs more OZONE,
                      |      /                       not Caster Oil!! "    
                      |_____/

    Re : .247 bob (flying::) collins
    
    I would beware of using a bec rx & speed control driven from the drive
    battery if you don't have some low voltage drive shut off circuit.
    
    This type of usage is fine for land vehicles as you can see/hear when
    the motor is slowing down before you lose control. Not so easy when
    it's a speck in the air.
    
    Some controllers have these and yours may be one of them, or I think
    you can buy them seperately (or even make them yourself !! - 8211 ic
    ??).
    
    Mark
    

    The Futaba Attack w/ integrated speed control was SPECIFICALLY designed
    for their Professor and Chipmunk electrics.  As such, it includes a
    motor cutoff that leaves the Rx with enough juice for a few minutes
    additional air time.

    Although these controllers are great for a sport type plane, they're not
    recommended for anything that might glide for a while.

    
	Here's a reccomendation for an electric plane.

	I built a Davey Curtiss Robin with Astro 05 geared system swinging
	a 10/6 prop and the Futaba electric controls w/speed control.

	What a sweet plane to fly !  If you want slow, stable and quiet,
	I give the complete package an A.  I had the first and second 
	flights this AM.  A hand launch into a very gentle breeze and it
	was up and away with minor trim required.  After a long delay 
	(20 min) to recharge, I decided to see if it had enough pepper
	to lift off the grass.  Well, it sure did, in about 20 feet it
	was bouncing on the tops of the grass humps, a little up and
	it's off again !  

	Anyway, I'd be willing to say that anyone that could build this
	kit could fly it with just a little expert assistance.  It
	flies at a relaxed speed, has an easy to see shape, and even
	glides in pretty well.  You're not stuck with slow and flat
	either, I did loops, spins, stall turns and ALMOST a touch and
	go. 

	Guess you can tell I'm pleased.

				Roger

This last months Model Airplane News has 4 or 5 reviews of electric
planes and several articles about electric.  I usually don't get Model
Airplane News - but if your new into electric I recommend this last issue.

One article had a section I will quote from page 38:

================================================================================

Here are some basic guidelines for successful electric flying:

o  The motor and batteries should be the same weight as the airframe and the 
   radio.

o  Static current draw should be 30 Amps.

o  Use cobalt motor(s).

o  Use high-rate sub-C cells (SCRs), not the new, longer-running sub-C cells
   (SCEs).

o  The larger the airplane, the better the power-to-weight ratio and wing
   loading, and the better it will fly.

================================================================================

This are probably not without a little controversy.  What say you Dan Miner?

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

This weekend was "sort out the stuff" weekend in preparation for the winter 
building season. One of the things I found (again) was my OLD electrics. I
have an Astro .25 ferrite that is 15 years old and its two eight cell packs
(which seemed to charge up fine) What I want to know is how people charge
a 24 volt setup like this. I've taken to charging each 8 cell unit separately
but this takes twice as long (one charger). I also sorted out my plan bin and
found the plans to a .15 powered J-3 that shed its wing many years ago. I
therefore have a perfectly good wing and the opportunity to build an electric 
fuselage ;^) I'm thinking that this might be a nice combination once I get all 
the bugs out. I can scratch build the fuselage as I wait for things to dry on 
other projects.

I'm looking at this as an exersize in using what's on hand (I don't want to 
buy a cobalt motor when I have this one already) and getting a return on the
fact that I've kept/moved this stuff over so many years.

I currently have Radio Shack connectors on them since they originally came
with bare wires. I'm also interested in comments/suggestions on a mechanical
speed control for this that will handle 24 volts (or isn't that a problem?)

The J-3 looks like a nice size fuse for sticking all the associated electric 
packs in. I can flow the air in through the dummy cowl to get my ventilation.
Any other thoughts and suggestions?

    Well, I am STILL pokeing around various shops and magazines---I
    read that Electrics issue of MAN.  I am stuck betwwen the PT-electric
    and the Electrostreak.  The PT sounds like its the ticket for the
    novice, but on the other hand, I think the Electrostreak would give
    me more growing room...if it survives the first few flights, of
    course.
    
    Now...lets say, for purposes of discussion, that I am a fast learner.
    Wait!  I know.  OK, OK, you can stop laughing now.  Heard it all
    before, right?  Well, how about if I told you that I have DEFINITELY
    been seen by witnesses, I think I have thier names written down
    somewhere, to have once walked AND chewed bubblegum...and get this---
    AT THE SAME TIME!  Yes! Its true!  OK, OK, OK.  Well, how about
    it?  Do you think I should risk the Electrostreak?
    
    Fred 'Shiney side down'   <--I really did'nt earn this you know.
    
    :-)
    

    
    	Several people WITH EXPERIENCE flying R/C have reported 
    	Electrostreak crashes.  They can walk, chew gum and put
    	on their pants both legs at once.  Buy the PT, build,
    	have fun, you won't be (as) depressed.  Personally, if
    	I'd never flown before, I'd buy 2 PT's and correct my
    	mistakes on the second.
    
    					Roger
    					(RATS! I tripped on my gum ...)
    

>(which seemed to charge up fine) What I want to know is how people charge
>a 24 volt setup like this. I've taken to charging each 8 cell unit separately

    You gotstahave a charger with a built in DC-DC converter that'll step up
    the voltage.  NEVER NEVER NEVER charge NiCad packs in parallel!!

>The J-3 looks like a nice size fuse for sticking all the associated electric 
>packs in. I can flow the air in through the dummy cowl to get my ventilation.
>Any other thoughts and suggestions?

    You might just want to spend the 24 Bucks for an ElectriCub Std. kit,
    and use the Fuse from that.  The E-Cub is a 54 inch span plane, that's
    gotta be pretty close to your wing.

>>(which seemed to charge up fine) What I want to know is how people charge
>>a 24 volt setup like this. I've taken to charging each 8 cell unit separately

>    You gotstahave a charger with a built in DC-DC converter that'll step up
>    the voltage.  NEVER NEVER NEVER charge NiCad packs in parallel!!

No, I don't do that. I have two independent packs that I charge separately and 
then plug together with a jumpered plug block that puts them in series.


+----------+ engine
bat 1
- -|
   | <======== this is jumpered on the engine plug
+--|
bat 2
- -------- - engine

So I have a 4 pin connector which fits two two pin battery connectors and, when 
connected, the batteries are then jumpered in series. The only concern I ever
had was that one battery cools while the other is charging so the packs can be
at two different temperatures when in use

Re: Electic Cub

The point is that I can build the current fuselage out of my scrap drawer along 
with the bulk balsa I bought way back when. (It's amazing the things you can do
once you've justified 100 sheets of 1/8", 1/16th" from Sig ;^) 

I can get away with far more if I quietly build from my current stock and $24
buys an unbelievable amount of bulk balsa stock (I also own several sizes of
spruce sticks ;^) I've got plenty of plans squirreled away along with a few
kits that I'd have to justify getting a new kit against. The only thing I've
been able to justify recently is an Xmas Panic since I haven't shown interest in
anything else that she (my wife/money manager) knows how to get/order (which is
why I asked about scratch building a Panic also)

Jim (can you tell I programmed in Lisp for 5 years? ;^)

    
                     DON'T GET AN ELECTROSTREAK YET!
    
     Its ok to buy an electrostreak, just don't build it or even think about
    flying it until you get some experience under your belt. If you read
    the articles in MAN, they highly recommended the PT - electric as a
    good trainer. At the same time, they emphasized SEVERAL times the 
    Electrostreak is NOT a beginner's airplane (This warning also appears
    several times in the instruction manual).
     The "streak" does not have any dihedral to the wing, and ZERO self
    recovery capabilities. It goes exactly where its pointed, and as Dan
    Minor has emphasized, it is prone to stall/snap in unconvienient
    places (Mine bit me on takeoff.) It lands at a higher speed than the
    PT-E, and also flys faster.
     I went the self taught method myself, and crashed an electric glider
    several times before becoming competent, than had a few crashes with
    my Electricub before getting comfortable. I transitioned to an
    electrostreak sooner than I probably should have, and it was a handful
    for the first 10 flights (Flight #5 ending in a serious crash). ANd all
    of this even though I an experienced Full scale flight instructor and
    have a pretty good understanding of aerodynamics. If I had hand
    launched a streak on my frst flight, it would of lasted .008 seconds
    before crashing. I also don't think the "streak would be a good first
    plane even with an instructor. Electrics tend to be closer to the
    ground, and the "streak doesn't leave much time for an instructor to
    recover.
        Get the PT, and you will probably still enjoy it, even after
    transitioning to other planes. Granted, learning to fly LOOKS easy,
    but its amazing how fast onw can get into trouble.
    
                                        Just my Opinion,
    
                                             Dan Weier
    

    
    re: .11
    
    Definitely do not try to make the Electrostreak your first plane -
    even making it your second plane is pushing it.  You'll have to trust
    us on this one, but the PT electric is _by_far_ a better choice.
    
    Bill

    Why can one not charge packs in parallel ?
    
    I do it very often and never had any problems. I charge them directly
    (8 cells), in parallel on a car battery with a 30 minutes timer.
    
    The good thing about it is that at the end of the charge the current
    goes down by itself because the difference in voltage between the
    packs and the battery gets very low.
    
    We very often use this method here in Europe.
    
    Obviously the two packs should be at the same discharge level when
    you put them in parallel, but other than that, I see no reason. 
    
    Before I used regulators, I even used a parallel/serial switches module
    without any problems. 
            
    Regards
                                                                           

    At this point in time, if you buy the "Streak", you will be able
    to say that you can chew gum, walk, put on your pants, and CRASH
    all at the same time. Buy the PT.
    
    Steve

    Charging 8 cells with a 12 volt battery results in a taper charge
    which should be quite safe at 30 minutes.  If you can live with
    a 30 minute charge time and an 85% to 90% charge, its simple and
    convenient.  
    
    A few replys back, there was a request for a mechanical speed control.
    Why would anyone want to use one of those?  In a plane, where every
    mah counts, I'd think the only alternative to a good controller
    would be a simple on/off switch.  Its not much cheaper than a home
    made speed control (if you include the servo cost) but it is simpler,
    and marginally more efficient at full power.
    
    To expand on the cost of a home made speed control, I'm assembling
    three JOMAR SC-4 controllers.  The end results are optically isolated, 
    high frequency controllers for 6 to 28 cells which drop .007 volts/amp.
    Buying the PC boards from JOMAR, and all new components from various 
    sources, they will cost less than $30.00 each, plus connectors.
    Not bad for one of the more highly regarded airplane speed controls!
    

I requested the mechanical speed control 'cuz I was hoping to find a car buf
that had updated to a better one and would sell the mechanical for a song. In
the past I've flown with a BIG capacity switch and all or nothing and was 
interested in the finer aspects of speed. I was looking for a mechanical so I 
could use my existing gas R/C gear without the need to upgrade to battery
eliminator and electrical speed control. I'm trying to get this into the air 
with a minimum of additional purchases. I've used this engine with the two
packs and a (non-shorting) switch that allowed for series - disconnected - 
parallel so I got 24 - 0 - 12 volts. I felt more comfortable having a neutral
center position with a 30 amp draw. This worked fine and gave me climb -
glide (yeah right ;^) - cruise capability with a minimum of fuss

    
>>    The good thing about it is that at the end of the charge the current
>>    goes down by itself because the difference in voltage between the
>>    packs and the battery gets very low.
    
    I don't understand how charging two packs in parallel has anything to
    do with this.  Please explain your reasoning.
    
    I would think that one big problem with charging two packs in parallel
    is that you don't really know how much charge current is actually
    going into each pack, since their internal resistance can be
    different, so you can get different amounts of charge on each pack.
    
>>    Obviously the two packs should be at the same discharge level when
>>    you put them in parallel, but other than that, I see no reason. 
    
    The other problem is that each nicad cell does not go to _exactly_ 
    1.2 volts when charged... if one pack "wants" to go to 9.60 volts
    and the other "wants" to go to 9.65 volts after charge, they'll fight
    each other.
        
>>    Before I used regulators, I even used a parallel/serial switches module
>>    without any problems. 
    
    I don't understand what you mean here either... are you actually
    isolating the two packs from each other with regulators?  If so
    you aren't really charging them in parallel.  Maybe that's the
    confusion???
    
    Bill

    I have copies of two articles by Keith Shaw.  The first is "Designing 
    Electric Scale Aircraft".  It includes guidance on selecting the
    power plant, props, allowable weight, and examples of how he applied
    his approach to produce a fully aerobatic 61" span Spitfire (Geared 
    40), and an 88" span DeHavilland Comet DH88 (Twin Keller 25/12s).
    I've seen both planes, and they do fly well.  Also described is his
    future project, Duane Cole's clipped wing (49") Taylorcraft for a
    geared 05.  The second is an evaluation he did on various connectors 
    and wire suitable for electrics.  (Sermos and JOMAR 12ga. won)
    
    Anyone wishing copies, reply via mail @ NYJOPS::BOBA

    I've been corresponding with an avid electric modeler from Canada,
    who also shares my fondness for WWI biplanes.  He sent me copies
    of these articles which appeared in past issues of the Electric Model
    Flyer, a newsletter published by the Electric Model Flyers of Southern
    Ontario.  Despite the name, they include members throughout Canada
    and some from the U.S.  The newsletter is published five times per
    year, and includes product reports, technical considerations, design 
    parameters, charging practices, etc.  Subscriptions are available
    for $10.00 (U.S. dollars) from:
    
    		Doug Deller
		189 Mill St. S. Brampton
    		Ont. Canada  L6Y 1T9

RE:  Note 387.251 by K::FISHER "Stop and Smell the Balsa!" 

>> Here are some basic guidelines for successful electric flying:
>> o  The motor and batteries should be the same weight as the airframe and the 
>>    radio.
>> o  Static current draw should be 30 Amps.
>> o  Use cobalt motor(s).
>> o  Use high-rate sub-C cells (SCRs), not the new, longer-running sub-C cells
>>    (SCEs).
>> o  The larger the airplane, the better the power-to-weight ratio and wing
>>    loading, and the better it will fly.
>> This are probably not without a little controversy.  What say you Dan Miner?

    I agree with *ALL* of these points 110% !!!

                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |            Happy Landings!
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|              - Dan Miner
     |_/      |___________|  |_________|  |
                      |       /           |     " The Earth needs more OZONE,
                      |      /                       not Caster Oil!! "    
                      |_____/

    You know, SR Batteries sells a pack rated at 1250MAH that's made of 
    800MAH sized cells.  This is probably the best pack to own if you're
    into electric flying.  It rates out at about the same as an average
    grade 1200MAH Sub-C sized pack, but weighs (7 cell variety) almost 5
    ounces less.  I've ordered some of these for my Partenavia Twin,
    combined weight of two of these 1250 packs is just a little more than
    ONE 1200 pack, with about the same duration.  The 10 Oz or so savings
    means a SUBSTANTIAL increase in performance.

>    You know, SR Batteries sells a pack rated at 1250MAH that's made of 
>    800MAH sized cells.  This is probably the best pack to own if you're
>    into electric flying.  It rates out at about the same as an average

I called SR a month ago and said I wanted the best pack for a Astro Cobalt
05.  They recommended their 900mah (800mah sized) pack.  I asked about the
larger 1200 - 1250 packs and they (she) said that Cobalts draw too many
Amps for them?

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

>    You know, SR Batteries sells a pack rated at 1250MAH that's made of 
>    800MAH sized cells.  This is probably the best pack to own...

>>    I called SR a month ago ...  They recommended their 900mah 
>>    (800mah sized) pack.  I asked about the larger 1200 - 1250 packs 
>>    and they (she) said that Cobalts draw too many Amps for them?

    The SR catalog states that the Magnums can't put out as much as
    the regular cells, but you don't HAVE to milk every last watt.
    You can use a cobalt motor, but the prop and cell count have
    to result in amperage that the cells can tolerate.  They would be
    great to gain flying time  without adding weight in a light plane.
    That doesn't mean giving up the advantages (lighter weight, higher
    efficiency, durability) of a cobalt motor, just using it differently.

>< Note 387.263 by NYJOPS::BOBA "Bob Aldea @PCO" >
>                           -< Different strokes... >-
...
>    The SR catalog states that the Magnums can't put out as much as
>    the regular cells, but you don't HAVE to milk every last watt.
>    You can use a cobalt motor, but the prop and cell count have
>    to result in amperage that the cells can tolerate.  They would be
>    great to gain flying time  without adding weight in a light plane.
>    That doesn't mean giving up the advantages (lighter weight, higher
>    efficiency, durability) of a cobalt motor, just using it differently.

So are you saying that one should use less and less prop until the
battery does not over heat?

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

>> So are you saying that one should use less and less prop until the
>> battery does not over heat?

    Nope.  Just because they offer more energy per ounce doesn't have
    to equate to going faster.  I'm lazy, so I want long, slow flights  :^)
    
    The cell has only so much power, so if you want a long flight,
    (over five minutes) you must reduce the drain.  I know one guy who
    gets 17 minute motor runs on his Amptique with 1700 mah cells. 
    Obviously, he is just loafing around the sky.  When he wants to do
    aerobatics, he changes to a high drain 900 mah battery pack, and
    swaps the wing and the prop.  He has found combinations that meet
    his needs.  There are many optimal combinations, depending on the
    equipment and the pilot.
    
    If you want to fly longer, you must carry whatever weight is required 
    to maintain an acceptable power level.  SR lets you do it with less
    weight, as long as the drain is low.  A .15 on 10 cells will easily 
    put out the same or more power as an .05 on 7 cells, with less
    current.  It just weighs more... unless you compare SR Magnums to
    ordinary SR cells.

    I don't think anyone can specify an absolute limit.  Exceeding the 
    reccomended current by a small amount or for a short time, will 
    damage the cell a small amount.  The SR catalog gives a a maximum 
    current spec which they believe will result in happy customers.  If 
    you are willing to sacrifice the longevity of the pack, you can draw
    more.  

    Randy,

    You should talk to Charlie Watt and ask him how (UN)happy he's been
    with his SR 1250 Magnums...

                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |            Happy Landings!
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|              - Dan Miner
     |_/      |___________|  |_________|  |
                      |       /           |     " The Earth needs more OZONE,
                      |      /                       not Caster Oil!! "    
                      |_____/

Charlie Watt and I did a comparison of my 900ma battery with his 1200ma (?) SR
battery (help me here Charlie). Each was peak charged then flown in my
Challenger until the battery eliminator cut it out. Now, this is REAL 
subjective, but I felt that the 900ma battery climbed out better on the
fresh charge, and it also seemed to have more oomph toward the end of the run.
They both ran for about the same amount of time.

I actually did the run in two parts, gliding for several minutes in between to
help cool motor and batteries. Neither of the batteries were particularly hot
after the flight. As a result, when I get a second battery pack I plan to get
another 900ma.

Dave

    My experiences with SR 1250's and SCR 900's seem in line with others.
    
    Presently in 3 electric gliders I'm using 2 SR 1250 Magnums, 1 Sanyo
    SCR 1200, 1 Sanyo SCR 900, and 1 Varta 1600.
    
    The SCR 900 gives the best all around performance, hands down.
    Very noticeable "burst power" at the beginning of the run, superior
    to others listed. Weight with Sermos conn. & 3" leads= 305gms.
    
    SCR 1200: Not enough duration diff. to justify the greater size
    and weight. Wt= 375 gms.
    
    SR 1250: Significantly lower power at full throttle. Won't take
    a full charge from my peak detect charger as easily, must be coaxed.
    Wt. & size advantage only justification. 244gms.
    
    Varta 1600: Steady, moderate power. No bursts. Very good duration,
    more than the 25% larger size would indicate. Takes a full charge
    very easily. Within 2-3 mm in size compared to SCR 1200.  377gms.
    
    These observations are based on running in 3 airplanes ranging in
    size from 76"-41oz. to 125"-68oz. 3 different motors all non-cobalt,
    104 to 125 watts. Direct drive , 3:1 geared, & 3:1 belt drive.
    5 different props, Graupner(3), Freudenthaler, K&W.
    Sizes 7-3, 11-6, 12 1/2-6 1/2, 12-7, 14-6, 8 1/2- 4 1/2.
    All folders of course.
    
    All moter leads 1.5mm (approx. 14ga.)
    
    Concerning Sermos conn. I've always had excellent results, would'nt
    consider anything else. Do your own soldering, tin the conn. & wire
    beforehand. Make sure the curved portion of the contact is snapped
    down firmly in the slot at the mouth of the plastic housing. Use
    at least a 50 watt iron. Can't go wrong.
    
    
        Terry
    
    

    Several weeks ago several of our Albuquerque Soaring Assoc. club
    members ventured to Lake Havusu, Az. to watch the Schneider Cup
    Reenactment scale float fly and contest.
    
    From an electric standpoint, the most interesting entry was a quarter
    scale Savoia-Marchetti flying boat powered by two Astro cobalt 60s'
    mounted in-line on a common shaft, driving a 22" prop. Juice supplied
    by 72-count them-72 cells. 
    
    The motors, batteries, and wiring were enclosed in a copper sheilding
    (Faraday cage) to prevent the magnetic flux from swamping the radio,
    or sterilizing innocent bystanders. Unfortunately the pilot used
    up too much charge taxiing into take-off position (he estimated
    3 minutes of useful power, total) resulting in a stall, snap roll,
    and inverted dunking. He made no further attempts that weekend.
    
    An F3E class electric sailplane running a single cobalt 60 on 27
    cells can draw up to 60 amps at full power. Any one care to hazard
    a guess as to what current the S-M would see at full power?
    I don't know the size or type of cells he was using. Let's assume
    SCR 900.
    
    A lot of other interesting flying machines and activities going
    on during the weekend. I can pass on some observations if anyone
    is interested.
    
            Terry
    
    
    

>    From an electric standpoint, the most interesting entry was a quarter
>    scale Savoia-Marchetti flying boat powered by two Astro cobalt 60s'
>    mounted in-line on a common shaft, driving a 22" prop. Juice supplied
>    by 72-count them-72 cells. 
    
>    An F3E class electric sailplane running a single cobalt 60 on 27
>    cells can draw up to 60 amps at full power. Any one care to hazard
>    a guess as to what current the S-M would see at full power?
>    I don't know the size or type of cells he was using. Let's assume
>    SCR 900.


    That's not how it works.  A Sanyo type SCR cell can only supply about 25
    or 30 Amps sustained current without damage.  Larger motors get more
    energy not by drawing more current, but by using a higher voltage.  A
    Cobalt 05, 15, 25, 40, and 60 all draw about the same current, but each
    uses one more stick of cells than it's next lower powered motor.  An 05
    uses 6, a 15 uses 12, a 25 uses 18, a 40 uses 24, and a 60 uses 32
    (assuming a 6 cell pack.  If you use a 7 cell pack, one 60 would need 35
    cells, two 60's in series would need 70, if you add two more cells for
    good measure you end up with the 72 cells used in the S-M).  Two 60's
    connected in series require twice the voltage of one 60, but draw the
    same amount of current as one 60.  That's gotta be how the above
    mentioned model was connected (if not, the guy who did it was an idiot,
    the wire alone required to handle 60 amps would probably weigh as much
    as his entire airframe).

    An F3E sailplane can't possibly draw 60 amps on 27 cells (as far as I'm
    concerned).  Either you misread/heard something, or my understanding of
    electric power systems is really wrong.

    Maybe, just maybe, a stalled 60 would draw 60 amps, but the motor,
    wiring and batteries would probably VIOLENTLY, EXPLOSIVELY combust under
    these conditions.

>>    An F3E class electric sailplane running a single cobalt 60 on 27
>>    cells can draw up to 60 amps at full power.

>    An F3E sailplane can't possibly draw 60 amps on 27 cells (as far as I'm
>    concerned).  Either you misread/heard something, or my understanding of
>    electric power systems is really wrong.

    Actually, according to Keith Shaw (*THE* guru on electric flight),
    cobalt motors can withstand 40 to 60 amps for short durations (less
    than one minute).  In a F3E sailplane, I would think that the motor
    runs would be more like 30 seconds (or something...).

    I have no comments about the wiring and/or batteries required.  I
    would suspect that Sanyo SCR's and 12 guage wire would handle 60
    amps for short periods of time, but I don't know for sure.

    Bottom line: I believe that some cobalt systems do indeed draw as
    much as 60 amps.

                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |            Happy Landings!
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|              - Dan Miner
     |_/      |___________|  |_________|  |
                      |       /           |     " The Earth needs more OZONE,
                      |      /                       not Caster Oil!! "    
                      |_____/

>    I have no comments about the wiring and/or batteries required.  I
>    would suspect that Sanyo SCR's and 12 guage wire would handle 60
>    amps for short periods of time, but I don't know for sure.

According to a table I got in the mail today from Al Ryder:

12 guage wire fuses at 235 amps and 14 guage fuses at 166 amps.

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

    Ok, lemme retract some of what I said.

    SCR's can easily produce much more than 60 Amps (I checked my
    application guide).  They don't last long doing it, though.  My packs
    get pretty darn hot running an 05 @ 20 Amps or so.

    I'll just say that I don't think pulling 60 amps out of a pack is a very
    efficeint way of powering an electric, since losses go up with the
    square of current, and all that wire's gotta be heavy, and the batteries
    can't be capable of taking that kind of abuse for long, but I suppose
    it's possible.

    Last night, our local hobby shop had a demonstration of GRAUPNER/JR R/C
    systems (programmable mc-series). They had invited (along with some
    GRAUPNER people) Franz Weissgerber, who is currently holding (I think)
    at least four world records for electric planes. Most impressive are
    his new speed records of about 250 km/h (yes, 156 mph) with a plane
    with 2 m (78") span.
    
    He said that the motors he uses may in some cases draw between 60 and
    70 Amps. He never had to throw away one cell since he is into
    electrics (8 years) except for the pack he fried last spring when he
    fast charged it with a thermal cutoff and forgot to mount the sensor
    and went to sleep. When he got up in the morning, he remembered his
    flight pack, went into his workshop with horrible imaginations what it
    might look like and it was even worse...
    
    I'll enter a more detailed report as I find the time.
    
    Regards,
             Hartmut

    Sorry Al, but I got my Lake Havasu info second hand fromm several
    local club members who did attend.
    
    Max Mills took his Miss America old timer, and Frank Green had his
    quarter scale Fleet bipe, both on floats of course. Max got shot
    down while flying at sunrise sunday morning. He figures someone
    turned on an xmtr. in one of the hotel rooms. Not much damage but
    he did have to recover the whole aircraft. Monokote adhesive doesn't
    like dunkings appararently.
    
    Since you were there maybe you should be the one to pass on any
    thing interesting. How about that foam Spruce Goose that "bought
    the lake", or the Gee Bee R2 , or the problems with attaining true
    scale speed.
    
    Max rescued the remains of one of the Cup entries from a dumpster
    were it had been consigned by it's irate owner after he had kicked
    and pummeled it for a while. He brought it home but I haven't had
    a chance to attend a viewing yet.
    
    Incidentally, I'm making tentative plans to be in Phoenix on Mar.11
    to attend the Formula I auto race and will be in Tucson for at least
    a few days before and after that date. Maybe we could get together
    then, I'll try to bring a glider or something. In fact I have an
    old timer scheduled for construction during the 3rd quarter of fiscal
    '90 (have I been working for DEC too long or what?) but can't    
    guarantee that it will be ready by Mar.
    
    
           Terry
    
    
    guarantee that it will be ready by Mar.

    Terry,
    
    Yes, I remember seeing both planes though I don't recall seeing the
    Fleet fly.  I _did_ see the oldtimer go a time or two.  Sorry to hear
    of his misfortune.  I have to suspect whether frequency control was all
    it should've been.  Early Saturday AM, three Schneider racers went in
    within minutes of one another.  One case was definitely a shoot down as
    two Tx's on the same freq were issued out of impound at the same time.
    Gads!  I don't know how they could've let that happen.  Later that day,
    I was standing next to Red St. Aubin, renewing an acquaintance of
    nearly 20 years ago when he experienced a monumental radio hit while
    flying his float-equipped Bucker Jungmeister.  He landed immediately/ 
    safely but the source of the _obvious_ interference was not located. 
    Almost certainly, it was someone turning on but (luckily) realizing his
    mistake and turning off before any damage was done.
    
    I saw the Gee-Bee R-2 fly only once, Friday afternoon, and it was quite
    impressive.  Appearing a bit tricky on the water, it appeared to fly
    better _with_ the floats than I've seen others fly without them.  On
    landing, he made a nice touchdown then _slammed_ into a wave, tossing
    it back into the air.  He was able to taxi back but something had
    obviously been sprung outa' shape from the awkward way it sat. 
    Whatever it was, I guess he decided to forego anymore flying that
    weekend...too bad as it was fun to watch and flew very nicely.  BTW, I
    understand that the float idea isn't all that far-fetched; apparently,
    a feasibility study _was_ done for float-equipping the Gee-Bee for
    Schneider competition though no prototype was ever built.
    
    On the scale speed question; first I must clarify that I don't
    subscribe to the geometric, pure math of calculating what scale speed
    _should_ be.  Simply dividing the prototype's speed by the scale factor
    _does_not_ necessarily produce a true scale speed.  I subscribe to Kent
    Walters' theory of dynamically similar speed which takes in
    consideration a host of other factors...read one of Kent's articles on
    the subject as it's far too longand complex to describe here.
    
    That notwithstanding, the problems were predictable using geometric
    scale speed:  The slower aircraft couldn't fly slow enough (the
    Deperdussin needed to fly at 12-mph to be scale) and the faster ships
    had a tough time flying fast enough.  However, compared against each
    other, they _looked_ about right.
    
    March 11th, eh.  Too bad you'll miss our March 1/8 AF Spring Scale bash
    by less than 2-weeks.  By all means, let's try to get together for a
    flying session while yer' here, though.  
    
    *KAY FISHER TAKE NOTE OF PHX. GRAND PRIX DATE...MARCH 11TH.* 

      |
      | |      00	 Adios,      Al
    |_|_|      ( >o
      |    Z__(O_\_	(The Desert Rat)

    
    Hi,
    
    I'm a newcomer to electrics although I have flown R/C glow powered
    before. I'm looking for a trainer-type electric to buy as an
    *inexpensive* re-introduction to R/C after a lapse in
    the hobby.
    
    From your previous replies, I noticed that the Astro Flight
    Mini-Challenger was recommended as a beginner electric. It seems like
    a good buy at $90, including an Astro Cobalt 035 direct drive. Has
    anyone seen, flown, or owned one?
    
    If so, does anyone know if it is a quick builder? In the interest of
    saving some money, would it be possible to use standard sized Futaba
    servos and 6-cell 1200 Mah SCR battery packs (both of which I already
    have)? Would the weight increase due to the above reduce performance
    (due to excessive wing loading, etc) drastically?
    
    If I can get by on my old equipment, the only other thing I need is
    an electronic speed controller. Can anyone recommend a cheap one?
    Do I need "dynamic braking"? What IS that anyway? How much current
    handling capability would it need- surge and continuous ?
    
    Thanks for any advice.
    
    BTW, where do the diehard R/C'ers fly in Southern Nashua? I stopped by
    the Flying Eagles field in Merrimack on Saturday, but no-one was
    around...
    
    Jim
    

    Jim,
    
    One of our local club members has a Mini-Challenger and I have seen
    it fly many times. It is as fast a builder as any other similar
    kit on the market and is well engineered for electric power.
      My one reservation concerning your specifics, is room for
    installation of standard size servos, and the use of 1200mah cells.
    Futaba micro servos and 900mah scrs fit nicely and work well.
    You might want to do some careful measuring before committing to
    your present components. The Mini-Challenger is meant to be
    significantly hotter the a typical Goldberg Electra or Eclipse
    it flys faster and can be a handful if attention wanders.
    Wing loading with your equipment(if it fits) would over 12oz./sq.ft.
    I would guess, certainly over 11oz. This is perfectly feasible,
    just keep it moving. I'm presently flying a 76", 480sq. in. area,
    Thermic Traveler on 7 cells, 900SCR ,2 Fut. Micros, & speed cont.
    at 12.3 oz loading it doesn't love light air but nothing to complain
    about.
      There are no "cheap" speed controllers, I'm using a Novak and
    a Tekin. The Tekin was $58 from Hobby Lobby a year ago and they
    had a close out on them this past summer at $28, definitely worth
    it if they have any left. Any name brand 7 cell controller will
    meet your current/voltage requirements. You'll almost certainly
    be below 30 amps max even on 7 cells. 
    
      Don't even think of using a non-folding prop, and with a folder
    you need dynamic braking in order to positively stop motor rotation
    at power-off and allow the airstream to fold the prop along the
    fuselage side. Dynamic braking simply means the speed controller
    switches in a reverse coupled mosfet as an elctrical load on the
    motor when the throttle is closed, causing the motor to quickly
    brake to a stop. Most controllers meant for aircraft use have this
    feature. You need it. r/c car controllers usually don't have it.
    
    Good luck and let us know how things turn out.
    
    
         Terry
    

    
    Thanks for the info, Terry.
    
    I guess you're right. 900 SCRs should shave an ounce/sq ft off the wing
    loading and it wouldn't kill my budget. Where do you guys get them?
    I've looked through RCM and they seem to be uncommon, with 1200s and
    1700s all over the place.
    
    Terry, when you say that the Mini-Challenger is hot, are we talking
    aerobatic/sport hot? Or just a bit faster than your typical glider.
    I'm looking for a fairly easy to fly plane, since, in my previous
    experience with gas-guzzlers, I had not nailed down landings yet! I
    hope this plane is not more than I can handle..
    
    Re: servos. Does anyone have experience with the Royal Titan micro
    and mini servos?
    
    Thanks,
    
    Jim

You might refer to response .213 for general info on electrics. There were
also some comments a couple weeks back somewhere else in this conference
about the best ways to learn to fly (electrics weren't high on the list for
trainers).

If the Mini Challenger is presenting too many problems, consider building the
full size Challenger. I have one with the Cobalt 05 and Astro gearing turning
a 12-8 folding prop. It uses 7 of the 900mAhr cells supplied by Astro (I too 
would like to know where to get replacements. Is it same as Sanyo SCR?). On/off
control is by a Graupner Power Switch 20, which is a simple relay. I was able
to use normal size servos, Airtronics 831's.

The weight came in at 47 oz, and with a 600 sq.in. wing that comes to 11.3 oz/
sq.ft. Like Terry said in .282, it does fly fast (has to, more weight) and it
loses a lot of altitude when it stalls. Moreover, if you are prone to less than
perfect landings, remember that the battery pack will do its battering ram
imitation, so fortify the former ahead of the pack. 

I am very happy with mine, now that I've got used to flying it. I had many
long flights this summer, and it sure is nice not to worry about the high
start or cleaning up afterwards.

Dave

    Re: .281 to .283

    Jim,

    I have flown the larger version a lot and, as you've probably read,
    I think it would make a fine trainer.  I will state that you really
    need to have an instructor to help keep it in one piece for those
    first few landings.

    Although I haven't personally flown one, I've heard the the
    Mini-Challengers are great fliers just like their larger brother (or
    is that sister?).

    RE: Servos.  Based on how little room there is for servos in the
    full sized Challenger I'd say that it would be nearly impossible to
    use full sized servos in the Mini-Challenger.  You really need to
    use micro servos.  Sorry, I've never used the Royal Tital servos. 
    All of mine are Futaba.

    RE: Battery.  As Terry recommended, I think you would be MUCH better
    off with the 900 mAh SCR batteries instead of the 1200 mAh SCR
    packs.  Before you run out and buy some though, wait and see how
    many cells are recommended for the cobalt 035.  I think Astro Flite
    recommends 5 cells (not 6 or 7).  Packs of 900 mAh SCR batteries can
    be purchased directly from Astro Flite or can probably be purchased
    mail order for a discount.

    RE: Speed controller.  If the cobalt 035 does indeed use 5 cells,
    you need to purchase a speed controller that will run on 5 cells. 
    Many of the speed controllers on the market will work with 6 or 7
    cells ONLY.  They crap out with only 5 cells.  Check before you buy. 
    I do know that Jomar sells a speed controller that will work with
    less than 6 cells.  (See their ad in RCM and other mags. and give
    them a call.)  I can't remember the exact price, but I think they're
    in the $30 to $40 range (maybe more??).  Contrary to what Terry
    said, I don't feel that an electronic brake is necessary.

    RE: "Hot" flyer.  I'll let Terry answer for himself, but I would
    guess he's refering to the fact that ANY electric powered glider has
    a higher wing loading than a "pure" glider.  Thus, the electric
    powered glider will have a higher stall speed and needs to be flown
    faster ("hotter") to prevent it from stalling.  Also, the
    Mini-Challenger will climb better than the typical Goldberg Electra
    or Airtronics Eclipse (with their standard car-type ferrite motors).
    (Maybe this is what Terry meant by "hotter"??)

    RE: Props.  I agree with Terry.  Invest in a folding prop.  Oh wait
    a minute - I just remembered that the Mini-Challenger comes with a
    nice folding prop.  Already done...

                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |            Happy Landings!
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|              - Dan Miner
     |_/      |___________|  |_________|  |
                      |       /           |     " The Earth needs more OZONE,
                      |      /                       not Caster Oil!! "    
                      |_____/

    Jim,
     
      No, I'm not talking acrobatic/sport "hot", but I am talking about
    a little bird that builds up speed very quickly, and can spiral
    down under power a lot quicker than us old glider guiders feel
    comfortable with, knowing what we do(which isn't much) about wing
    spar strengths etc.
      If you don't have your landings "nailed down" yet you'll need
    to fly the M-C over a nice smooth grassy area with plenty of open
    area on the perimeter, as they are best landed with a long flat
    approach holding a fair amount of speed. It should be well within
    your experience, since you're not a rank beginner. Just don't expect
    it to be a lot easier than a typical glo-powered trainer.
      If you're serious about electrics you really need to send for
    a Hobby Lobby catalog. The newest is just out ,$2.00, see their
    ads in almost any mag, and they have 900 SCRs and well as the best
    single source selection of electric equipment in the U.S. The prices
    on the German stuff will cage your eyeballs.
      Hobby Horn in Calif. is another battery source. They advertise
    in "Model Builder", and possibly RCM.
    
      Terry
    

    Re: .285, Dan
    
    You mentioned something about 900 mah packs vs 1200.
    
    I too am puzzled about whether to use 1200 over 900, and
    why.  I'm building a Davey Flybaby and want to save as 
    much weight as possible.  I have a feeling that I'd rather
    use 900's, but can't verbalize a good reason why.  Shed 
    some more light on this if you can, or point me in a
    direction where I can find some more info.  
    
    Thanks, john

RE: Note 387.287 by RUTLND::JNATALONI

>    I too am puzzled about whether to use 1200 over 900, and
>    why.  I'm building a Davey Flybaby and want to save as 
>    much weight as possible.  I have a feeling that I'd rather
>    use 900's, but can't verbalize a good reason why. 

    John,

    It seems to me that you answered your own question.  The 900 mAh
    cells weigh less than the 1200 mAh cells.  In addition, I think the
    900 mAh cells have a slightly lower internal impedance (resistance)
    so they will deliver a little bit more power to the motor.  (But not
    much - this difference is negligible.  The big win is weight.)

    NOTE: when looking for Sanyo 900 mAh SCR cells, do not be confused
    by the 800 mAh cells.  The 900's look a lot like the 1200's - short
    and fat.  The 900's are simply shorter than the 1200's.  The 800's
    are tall and skinny - like a typical AA battery.

    If you buy SR brand batteries, they claim that their 800's will
    actually deliver 900 mAh.  I'm not sure if they sell a pack made up
    of the "real" 900's.  If they do, they probably call them 1050 mAh
    packs or something.  

    One other thing that's important to note is that you do *NOT* want
    the increased capacity SCE (or SR's "Magnum") type cells for most
    applications.  These cells ONLY work well if your system is drawing
    less than 20 amps on the ground.

                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |            Happy Landings!
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|              - Dan Miner
     |_/      |___________|  |_________|  |
                      |       /           |     " The Earth needs more OZONE,
                      |      /                       not Caster Oil!! "    
                      |_____/

    Many thanks Dan,  I really wasn't sure about the comparative
    weights and I think I,m going to be just as comfortable with
    the 900's.  As I build I'm doing a weight analysis.  I'm a
    little surprised at how much the "system" weighs!
    Every ounce counts, particularly since I'm not looking for
    blazing power or speed.  I just want to tool around the
    flight zone under "Middle age reflex" conditions.
    
    You also cleared up a question I had about SCE, and Magnum,
    and other high powered stuff.  It's all appreciated,  john.

    
    Thanks for all the input, guys. :-)
    
    Just one more question(?) What does the Astro Cobalt XX [Geared]
    "Systems" include? I was perusing the advertisements of a magazine
    when I came upon this term, and I can't figure out what it means.
    
    
    
    Thanks again,
    
    Jim

I can take a guess on the Astro Cobalt XX [Geared] "Systems". The XX is a place
holder for 035, 050, 40, etc. Size of motor. I got a "system" with my 
Challenger. It included the 05 motor, the gear (which is a heavy duty metal one,
not the plastic one that comes with the Eclipse), a 7 cell pack of 900 mAhr
batteries, a plastic mount for the motor which I didn't use, and a toggle
switch. And a few decals.

I snipped off all the supplied Tamaya connectors and replaced with Sermos, and
have had no problems yet.

Dave

    The difference between Astro "motors" and Astro "systems" is that
    the systems include a switch harnes and the proper number of cell
    battery pack.

    As Dave suggested, I recommend using Sermos connectors instead of
    the Tayma connectors.

                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |            Happy Landings!
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|              - Dan Miner
     |_/      |___________|  |_________|  |
                      |       /           |     " The Earth needs more OZONE,
                      |      /                       not Caster Oil!! "    
                      |_____/

    
      RE: Note 387.281
     
      (At the risk of enciting the rath of the moderator, I will try to
       briefly answer 2 questions asked in previous notes.
    
    
          Where do people fly in the Nashua area?
    
    
       The flying Eagles of Southern N.H. currently operate 3 fields.
      Merrimack, Bow, and Amhurst N.H. Merrimack is the smallest, and least
      used. >It is usually difficult to find other flyers ther unless it
      is pre-arranged. The amhurst field is for gliders and Electrics only.
      I believe the Amhurst site will only be available until April when
      the current lease expires. The main field is up in Bow. I have never
      been there, but I believe this is where most of the flying is done.
      (Unfortunatly, Bow is quite a distance from Nashua)
    
    RE: note 387.283
    
      I have 2 Titan mini (not Micro) in my Electra. They are just
    slightly smaller than the standard Futaba 128 servos, and weigh a
    little less (1.1oz vs 1.4 oz each.) Titan also makes a Micro servo
    which comes in at .9 oz, but I am not sure of the dimensions. The 
    difference in price is about $15 for the Mini, and $23 - 25 for the
    Micro. Comparitively, a Futaba Micro servo is .6 oz, costs about
    $30 through towers, and has smaller overall dimentions than the
    Titan Micro servo. ALl titan servos can be has with a range of
    connectors; Futaba G,J and Airtronics.
      So far, the 2 servos I have have worked fine, with no problems
    yet to report. As mentioned in a previous response, you may not
    have the room for anything other than a Futaba type micro servo,
    and these are currently as light as anything else on the market.
    
    
                                           Dan Weier
    

    In the Jan. 90 issue of Model Builder is an interesting article
    on some German modelers who are flying electric sailplanes with
    solar cell arrays on the wings that recharges the motor batteries
    in flight in between motor runs. Under good conditions they claim
    they can fly virtually all day on one battery charge. They're using
    a Telefunken solar cell in an array of 24 giving 12V @ 558mW into
    a standard 7 cell pack of 900mA scr's. If my basic idealized
    calculations are correct this is about 1 amp in, and would be
    definitely feasible even allowing for about 50% off for real world
    conditions. They use a $14 Graupner "can" motor and the gliders
    are lightly loaded floater types. They claim the solar cells aren't
    too expensive and are "now widely used on models", to quote the
    article.
    
    My question is this: Does anyone know of a good U.S solar cell source
    and what publications they advertize in. In the Edmunds Scientific
    catalog are a couple of cell types that appear to have the beans
    to do the job, but would cost over $300 for a 24 cell array. This
    does not qualify in my book as inexpensive and I'll bet that some
    where is the U.S. or Japanese equivalent of the Telefunken at, I
    hope, $2 or $3 per cell, or am I being hopelessy naive? At any rate
    I have the airframe 80% designed in my mind and will attempt to
    emulate the German effort if cost is not my undoing.
    
      
    
    Terry
    

That's a neat idea! But I bet those solar cells are fragile. Smooth landings
a must.

By the way, if it puts out 500mW at 12V, isn't that about 40 mA, not 1 A?
(I assume Power = V*I).

Dave

    Either way, Re. power output, you're gonna be dissapointed if you expect
    to find cheap cells.  Solar Cells are generally VERY inefficient.  The
    ones that provide decent capacity are EXPENSIVE.  I doubt you'll get
    away cheaply if you're looking for a system that will perform.

    You had me scared there for a minute Dave, but "Sufficiently advanced
    technology is indistinguishable from magic". 
    Your right, of course, that P=IV therefore I=P/V. Then plugging
    in the solar cell specs from the article we have for a single cell:
    .558mW/.5V = 1.116 amps. Multiplying the top and bottom of the left
    side by 24 (the total cells in the array) we have: 13.392W/12V =
    1.116 amps. Not being very familiar with solar cells myself, this
    was'nt intuitive obvious and I had to thrash thru the math too.
    
    These numbers are all ideal of course but they square with what
    the Germans are saying; that the solar cell array is supplying about
    1/10 of the current necessary to sustain flight. I interpret this
    to mean don't lose altitude and be able to cope with the occasional
    patches of sink. Given their motors and aircraft, 8-12 amps seems
    about right to sustain flight. Therefore 1 amp from the array checks
    out. One thing I know for sure, if they can do it with German sun
    intensities , I can sure as heck do it with New Mexico sun intensities!
    
    Concerning Walter Ryders' mail message, thanks for the offer of
    the literature Walt, but my command of German isn't good enough
    to allow me to order a glass of Schnappes, so I'm afraid I wouldn't
    get much out of a technical article.
    
    
    Terry
    

    Santa was very good to me, so I now have an Amptique, Astro 15G system, 
    and an Astro 112 charger.   All I have to buy is a few miscellaneous 
    items, and finish the two projects cluttering up my shop, so I can
    start building.  One fine spring day I may even fly!
    
    On examining my goodies, I discovered that the Amptique fuselage sides 
    are narrower than the plans, but both of the formers are full size.
    One or the other has to be replaced, but that's no crisis.  Nearly
    every part is cut, sanded, and bagged, so construction should go very 
    fast.  (assuming the rest of the parts fit)  The other minor 
    disappointments were a missing wing mounting dowel and the *VERY* 
    brief construction manual.  Compared to the Electricub manual, the 
    documentation that comes with the Astro and Leisure products is 
    practically non-existant.  Even the switch on the charger which 
    selects the number of cells being charged is unlabeled!  
    
    Since the plans show a Leisure motor with seven cells, I need to come 
    up with a mounting scheme that will work for the Astro 15 with twelve 
    cells.  There's room enough for the cells, but its slightly ahead
    of the CG, so I don't know how much it will affect the balance.  I 
    will probably have to finish the nose of the fuselage last, in case 
    the length needs adjustment to balance properly.
    
    The simplest method of mounting the motor appears to be using longer 
    screws to replace the gear box screws, and snug up the whole assembly 
    behind the firewall.  I was also considering the golden rod straps 
    that Kopski uses on his Skyvolt, but that requires access holes for 
    the screws, and fitting a cradle for the motor.  What methods do you 
    people prefer/use?

    More questions:  

    I noticed that the toggle switch supplied by Astro is rated for 
    something less than 10 amps.  Did any of you ever use one, and if 
    so, how did it hold up?  
    
    Does anyone know how Williams Brothers vintage wheels compare to 
    Sullivans or others for weight?

>    fast.  (assuming the rest of the parts fit)  The other minor 
>    disappointments were a missing wing mounting dowel and the *VERY* 
>    brief construction manual.  Compared to the Electricub manual, the 
>    documentation that comes with the Astro and Leisure products is 
>    practically non-existant.  Even the switch on the charger which 
>    selects the number of cells being charged is unlabeled!  

    Yeah, it's a problem with both their models and their electronics.  You
    should see the plans that came with my Astro Partenavia.  Sheeshe!
        
>    Since the plans show a Leisure motor with seven cells, I need to come 
>    up with a mounting scheme that will work for the Astro 15 with twelve 
>    cells.  There's room enough for the cells, but its slightly ahead
>    of the CG, so I don't know how much it will affect the balance.  I 
>    will probably have to finish the nose of the fuselage last, in case 
>    the length needs adjustment to balance properly.

    I made my Electra into a V-tail, and had to perform some extensive
    modifications to make room for the mechanical mixer, and still satisfy
    my desire to have the battery pack centered directly on the CG (so I
    could fly the plane without a pack, just as a glider).  I suggest that
    you decide where the batteries will fit best, and then work the radio in
    around it (you might need to forget about the balsa pushrods, and use
    gold'n rod like I did in my Electra.  The extra weight is minimal, and
    the additional options for routing make more of the inside of the fuse
    available for stuff like Radios, Servos, and batteries).

    The Astro 15 isn't all that much bigger than an 05, but it's gonna be
    heavier.  If the plans show a direct drive 05, you can "even it out" by
    mounting the 15, with some spacers, further back from the firewall
    (although the 15 isn't much longer than an 05, with the addition of a
    gearhead, it is, so you should be able to move it back substantially
    without affecting the position of the end of the shaft, as compared to
    the direct drive 05).
    
>    The simplest method of mounting the motor appears to be using longer 
>    screws to replace the gear box screws, and snug up the whole assembly 
>    behind the firewall.  I was also considering the golden rod straps 
>    that Kopski uses on his Skyvolt, but that requires access holes for 
>    the screws, and fitting a cradle for the motor.  What methods do you 
>    people prefer/use?

    Yes, go with longer screws, it's the best way.
    
>    I noticed that the toggle switch supplied by Astro is rated for 
>    something less than 10 amps.  Did any of you ever use one, and if 
>    so, how did it hold up?  

    Yeah, but thats 10 amps at 125 volts, not 14 volts.
        
>    Does anyone know how Williams Brothers vintage wheels compare to 
>    Sullivans or others for weight?

    use Dave Brown light flight wheels.  If you don't like the square look
    of the foam tire, just put the wheel on an electric drill and use some
    sandpaper to round off the corners of the foam.
    

>>  The Astro 15 isn't all that much bigger than an 05, but it's gonna ...
    
    The plans show a Leisure geared 05 with a gearbox mounted to the
    front of the firewall.  Since you can't mount an Astro 15G in the
    same way, the motor is about 3/4" farther back.  It actually may
    work out just about right to offset the batteries.  I'd rather not 
    push the servos any farther aft, so if I really have to, I'll 
    rearrange the battery packs, or modify the nose.
    
    There is obviously something I don't understand about switch contact
    ratings.  Are you saying that a switch rated for 6 amps at 125 v
    will tolerate 60 amps at 12 volts?
    
    I've got some Lite Flight wheels for the Amptique, but I wanted to 
    use Williams Brothers, or something similar, on a future project.
    So the question stands, has anyone ever weighed them?

>    There is obviously something I don't understand about switch contact
>    ratings.  Are you saying that a switch rated for 6 amps at 125 v
>    will tolerate 60 amps at 12 volts?

No, it doesn't work that way. When measuring power dissipation, you
multiply voltage by current. The switch ratings are independent
parameters - voltage is the maximum voltage that can safely be applied
across the switch when it's open, while the current rating is the
maximum current you can put through a switch when it's closed. You
don't have to know Einstein's law of relativity to  figure out that
these are independent parameters, just a little common sense.

Consider that the closed switch has a small resistance, say .01 ohm.
Using Ohm's law, if you put 10 amps through the switch, P=I^2 * R, or
1 watt will be dissipated in the switch. If you put 100 amps through
it, you'll be dissipating 100 watts in the switch. Of course, that's
likely to melt your switch pretty soon. 

For efficiency, you want a switch that has the lowest possible resistance
when closed, because the power dissipated in the switch is lost to heating
the switch, not turning your motor.

Although the Doctors of Electrical Engineering will probably jump in
now and talk about arcing, migration of contact material, spring
constants and force for moving the switch, etc, the simple application
of Ohm's law is all you need to figure this one out (you can have your
degrees, and I'll keep my common sense! 8-).

Dave

    I'm not going to argue with Dave because he's too big to argue with. 
    (Besides, I think he's right...  :-)

    So, although it seems that the 6A rating is too small, many people
    (including me) have used them succesfully as a saftey switch.  They
    do NOT hold up well if you use them as an On-Off "speed controller"
    because they arc and eventually fail.  

    Assuming that you will be using this switch with a "real" speed
    control, this switch will work just fine.  Just make sure your speed
    controller is turned all the way off before you flip the saftey
    switch to on.

                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |            Happy Landings!
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|              - Dan Miner
     |_/      |___________|  |_________|  |
                      |       /           |     " The Earth needs more OZONE,
                      |      /                       not Caster Oil!! "    
                      |_____/

    Thanks Dave and Dan, I was wondering if I'd forgotten more than
    I realized.  A mind is a terrible thing...

By the way, my comment explains what the ratings mean, not necessarily
what works! It's likely that using an underrated (current rating) switch
will work fine because the rating is for continuous load, for the lifetime
of the switch. In electric planes and cars the duty cycle is a few minutes
on at a time, which may not cause the switch to overheat and melt even if
it's very underrated.

Dave

Here is an interesting (to me anyway) tidbit from the latest Model Aviation
in the FF Old-Timers column by Bill Baker.

He was in the middle of plugging Hobby Horn who will send you their
catalogue for $2.00 from P.O. Box 2212, Westminster, CA 92684.

Anyway he said...
  
"As an aside, I would like to say that I have just test flown the Midway
kit Ultra Mk IV (an Electric RC Sailplane), and it is not only the best
Electric Sailplane I have flown, it is as good as any Sailplane I have flown
- and I have flown a bunch.  For your first Electric Sailplane, I recommend 
the Carl Goldberg Models' Electra, but the Mk IV is a fine kit and one
great flier."

Pretty bold statement!  I am going to call and order a prop adapter from
them this afternoon and get the catalogue.

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

>I am going to call and order a prop adapter from
>them this afternoon and get the catalogue.

Called Hobby Horn a while ago - they had Astro prop adapters in
stock for $3.96 plus $2.00 shipping.  I've had one on back order
from Sheldon's for months and tried to get one from Tower a few weeks
ago but they didn't have any in stock and wanted to substitute a
Dubro part that I'm sure wouldn't fit.  Anyway Sheldon's and Tower both
wanted $5.00 plus shipping and handling.  Plus the lady that took my
order sounded like she knew everything there was to know about prop
adapters.  Nice place.

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

    I've had bad luck with the Astro Prop Adapters.  If you over tighten the
    screw that holds the prop on, they break.  It's a flaw in the way they
    machine the part.  It leaves a thin cylindrical joint where the threaded
    prop mounting stud meets the back plate.  Overtighten the screw, and you
    actually pull the stud off the back plate.

                    Screw goes through prop and into
                        this stud
                            |
                            v
    
                            _
                           | |  <---Prop mounts on this stud
                           | |
                        ---------
                        |       |   <--- Back Plate
                        ---------


    I use Master Airscrew adaptors.  You gotta drill 'em out for Astro
    Cobalts (the motor shaft is larger diameter), but it's easy to do, and
    they're much more durable.

    For similar reasons I too have given up on any prop mounting system
    that only uses one screw. Earlier Graupner designs with the double
    allen head set screws are durable, as are the present Freudenthaler
    designs (same system), but the new Graupner "Scimitar" system
    with its split collet and large nut , installed with a regular
    "spin tight" wrench, are far and away the best for durability,
    simplicity and ease of installation/removal. The props themselves
    are more efficient too.
    
    Terry
    

    Yesterday one of our component engineers drifted by and started
    telling me all his troubles, at least the RC related ones.
    He's been flying an electric sailplane with a Leisure ferrite motor
    on 7 cells, using a Futaba Attack radio, the model with the rcvr.
    and motor controller built into the same module. I think it's called
    the MC4A or something like that. He had been flying for 4-5 months
    with that setup with ok results but recently got an Astro 05 cobalt
    motor to replace the Leisure. Last weekend he installed the cobalt
    and was going ti do static thrust tests, just holding the plane
    in his hand and running full power to see if he could notice a
    difference in thrust. 5 seconds after applying full throttle
    the rcvr. module goes up in smoke. The throttle function was dead,
    the rcvr. function still worked normally. The mosfets were visibly
    fried and one side of the case was partially melted.
    
    He called Futaba and the repair tech there said something like,
    "Yeah, we've got 4 or 5 of those units in here now that have had
    problems with cobalt motors." He didn't say what the problem was
    or what they were doing about it. So John went ahead and sent his
    in also. That was tuesday, so no word yet on anything.
    
    I've noticed that these units use only 3 mosfets. Most discrete
    7 cell controllers have 4 or 5. Also, Futaba rates them at 100 watts
    handling capability. This is less than a cobalt 05 is rated at,
    usually about 125 W, so I suppose they could deny responsibility
    on that point, but does it say in the supplied specs to avoid cobalt
    motors for this reason?
    
    Terry

I checked out the Futaba when I was looking for a motor controller. I decided
against it because it was clear from the specs that it couldn't handle the
current of the cobalt motor. I don't remember the spec, but I'm pretty sure it
was under 20A. 

Dave

    From what I've read, the motor controller has a thermal overload 
    circuit which is supposed to shut down the motor.  One of the
    columnists tried it with a really hot ferrite 05, and found that it 
    would shut down after a short run, and power on again after it cooled.  
    In one installation, additional cooling air to the receiver fixed a
    problem with the motor shutting down prematurely.
    
    It sounds like it doesn't always work if Futaba has a pile of them in
    for repair.  The controller has other weaknesses, but it is light and
    convenient for low power installations.
    
    Re: the number of MOSFETS, if I remember right, the JOMAR SC5 has only
    three and it can handle a cobalt 15 or FAI cobalt 05 with no problems. 
    The issue is not the component count, but the ratings of the devices
    and the heat sink or lack thereof.  Many of the controllers have little
    to no way to dissipate the heat, so the devices cannot be operated
    continuously at their maximum ratings.
    

    
    	I've got the Futaba radio with the same receiver and am running
    	an Astro Cobalt 05 (geared) and haven't had any of that sort
    	of trouble yet.  Does the gearing reduce the load thru the speed
    	control ?
    
    						Roger

    The current drain will vary directly with the size and pitch of the
    prop.  That is, a bigger prop will load the motor, slowing it down, and
    current will rise.  Likewise current heads for maximum in a stalled
    moter, which is why most flyers use a fuse in the line for protection
    in the event of a nose over or any other condition that blocks the prop
    from turning.  
    
    Since the static drain is higher than when the plane is flying, 
    anything that runs okay on the bench should have a safety margin in 
    the air.  In any case, the design is supposed to protect the 
    controller from overload, so unless you have a defective unit, the 
    worst that should happen is an interruption in power.

    
      I also had an MCR-4A REC/SPEED CONT in an Electricub. It worked fine
    with the kit supplied "can" motor, but could not handle an 05 cobalt
    for more than 2 minutes without shutting down. When it cooled down, it
    would re-set and work again for a while. I was able to duct air to the
    Heatsinks with a large diameter drinking straw. This band aid worked
    fine, and I didn't have any future problems when using a 6 or 7 cell,
    even with sustained high power. The same unit worked fine in my
    electrostreak (until it got demolished in a crash,$100 through towers,
    I didn't replace it, now I have an extra Transmitter). The
    Electrostreak has the Goldfire motor. Until I started reading about
    other people having difficulty with the unit shutting down, I had
    attributed the shutdowns to inadaquate airflow in the Cub. The "Streak"
    has a much better cooling design, although I never tried it with a
    cobalt motor.
      The unit was originally designed for Futaba's Professer and Chipmunk,
    so I don't think it was ever designed for the higher current
    applications, although Futaba doesn't discourage one from buying one in the
    first place by listing limitations etc.
    
                                          Dan W.
    
    
                                             

    
    One thing that may be being missed is that generated heat = wasted
    power to the motor. The heatsink also adds to the all up weight. 
    
    What are the operational advantages of full power response over on/off
    operation with a relay ?
    
    Just as a side I did some experiments a while back using BUZ11 fets.
    I found that a low gate voltage (say less than 8V) would result in
    poor efficiency (i.e. heat). Using a standard dc-dc converter (15V),
    or an oscillator/voltage doubler (13V) increased efficiency markedly.
    I got an efficiency of 99.79% with 4 fets (0.0068 ohms on resistance).
    Granted for flight use this would need to be bettered by adding more
    fets so that a heatsink was unnecessary at the higher currents.
    
    Mark  

    Mark is right about heat and losses being a real consideration.  This
    is a good reason for not overloading a motor beyond its normal
    capacity.  As the motor slows, current increases, and the losses due to 
    winding and brush resistance increase.  Just as a stalled motor gets
    hot without doing any work, running the motor with too much prop can do
    the same thing.
    
    As a rule of thumb, each ounce of flying machine requires about 3 to 4 
    watts to achieve sport flying aerobatics.  A speed control with a full 
    on resistance of .007 ohms and fifteen amps of current consumes about 
    1.5 watts due to resistance, and another 4.5 to 6 watts simply because 
    of its weight.  Adding a relay and servo control offers an advantage 
    only if the weight is kept low.  The power wasted in a fuse is just as
    sickening as paying for car insurance, but few people want to risk
    being without it.
    
    Another thing to remember, is that the wiring and connectors can add
    much more resistance than a good controller.  Top of the line 12 ga.
    wire is about .002 ohms per foot, and lampcord is up around .006 ohms
    per foot.  Connectors add anywhere from .0003 to .004 ohms per contact,
    so the total can easily exceed the losses in the speed control. 
    Depending on the current consumed, sometimes the larger/better (lower
    resistance) wire is not the best choice because of its weight consuming
    more power.  Low current, high voltage installations are less
    sensitive to losses caused by wiring and connectors.
    
    As for heat sinks, its again a trade off, but I don't know enough about
    heat transfer to calculate the minimum area and thickness for an
    application where airflow can vary dramatically.  The smart thing to
    do, is ensure adequate airflow to *all* of the electric installation.  
    Hot wire has a higher resistance, so losses are greater, so the wire 
    gets hotter, so the losses go up...
    
    If all else fails, duplicate an installation that worked well for
    someone else.  ;^)

    
                   Geared Or not???
    
    
       I looked for an answer to my question in the notes but, 
    
         I have made a victory of sorts over the weekend with my wife.
      She for the first time ever did not mind accompaniing me to the
      flight field, Only because it was an Smellless, noiseless, and
      otherwise unoffensive ELECTRIC!!!. I am sold on the ease, and
      quiet fun of electrics. After reading all these notes every day
      at lunch I still am wondering what the real difference between
      an electric "geared" motor or one that is straight. Is it speed?.
      or can a geared haul more weight?. Or is flight time?. Since it
      was my B'day last weekend, and the wife said go to your favorite
      hobby shop and get what you need ( she really wants me to check
      out electrics or get another elec sys) I feel I will do just that.
    
        I now have a problem. Geared or not?. I am looking for a sys
      in the 15 to 25 size, and I intend to buy maybe the "american
      eaglet". Any suggestions?.
    
     Thanks
    
     Kevin

    
                         My 2 cents worth.
    
      One of the factors that determine which type of motor to use is the
    type of aircraft. At one end of the spectrum are electric gliders such
    as an Astro Challenger and Electra, at the other end are pattern and
    pylon racer type aircraft such as an Electrostreak and Rat racer. The
    gliders need a motor and prop to support a light wing loading and
    relatively slow airspeed, hence the best combo is a geared motor with a
    large slow turning prop. If this type of combo were used on the quicker
    aircraft, they may get a good climb, but they would not be able to
    achieve the desired higher airspeeds. Using a direct drive motor on a
    glider works ok, but you lose efficiency since the smaller prop wants
    to go faster than the slow wing can support. Why not use a large prop
    on a direct drive? - not enough torque available without the gearing.
    This is at best very hard on the engine, at worst the engine cannot
    support it.
       If the plane you are considering is an in-between sport type model
    often you can go either way depending on personal preference. In my
    Electricub I chose a direct drive cobalt for a couple reasons: The size
    prop was more "scale in appearance, the direct drive was a cheaper
    motor to buy and I felt better adaptable to other installations, and
    it gave slightly higher flight speeds (although likely less climb
    performance than a geared system). I have also seen Electricub's with
    geared systems.
       As a reference, Astro cobalt puts out a list with recommended
    motor's for specific aircraft applications. I believe this list appears
    somewhere in this notes file.
    
                                   Hope this helped,
    
                                           Dan W.
                          

    A point to remember is that a gearbox can be removed and the motor used
    in direct drive applications as well.  The only problem is that when
    the gearbox is removed, the motor rotation must be reversed unless it
    is to be used in a pusher application.  Likewise, at a slight cost
    penalty, a gearbox can be added at a later date.
    
    The Astro 15 seems to work well in light planes intended for a .15 to
    .25 wet power.  I haven't seen too many Astro 25s in use, possibly
    because it weighs quite a bit more.  Seems like most folks jump up to
    the Astro 40.  

    Re .331
           Rotation reversed when gearbox removed ?
    
           Depends on the gearbox.  I'm using an RPB gearbox
           (got it from Ace) utilizing a planetary setup,
           rotation is the same either way.        john

    re .329
    
    Dan and Bob pretty well summed up the differences between geared
    and direct drive so I'll just point out that a kit review of the
    American Eaglet appears in the Apr. issue of RCM. That particular
    airplane is a good example of one that can used either geared or
    direct. With all the external struts and gear hanging out in the
    breeze, you know right off that there's no reason to expect high
    speeds. Therefore the stock setup with a 2.5:1 geared 11X7 prop
    is a logical choice and it will perform adequately. Substitute
    a cobalt 125W motor (05) and it would climb better but top speed
    wouldn't improve much. My choice would be a direct drive non-cobalt
    125 W motor such as the Graupner speed 500 turning a 8X4 prop.
    This would reduce weight and bulk and keep the wing loading
    down which is as important to consider in an electric as weight
    alone. If you're thinking of putting a cobalt 15 or 25 in the
    Eaglet, I'd advise, don't. The extra power will be out of place
    in that type of plane, but more important, the considerably greater
    battery pack weight will raise your wing loading to the point where
    you'll have a real handful on your hands, high landing speeds,
    overstresse structure, etc. Also I'd be surprised if you could
    shoehorn either of them into the available space, especially the
    25.
    
    Terry
    

    Gotta clean up some imperfect information I left in .332:
    
    The unit I'm referring to is made by Al-Tec Prods. Inc., 
    I got it via Ace catalog.  It is an RPB Gearbox (Ring/Pinion
    & Bearings), designed for most motors including Astro, Leisure,
    Robbe, Graupner, and Mabuchi.  It's a nice little unit, comes 
    with extra ring gears to allow ratios of 3:1, 2.5:1, 2:1.
    Versions to fit 1/8" and 5/32" shafts as well as a marine
    pusher.  Also comes with prop adapter collet.  All for $30
    and as I mentioned before, rotation is the same as ungeared.
    john

re: Note 387.334   RUTLND::JNATALONI                                 
    >>>    The unit I'm referring to is made by Al-Tec Prods. Inc., 
    
    An Astro geared motor is only about $20 more than the direct drive, and
    the gearbox itself sells for around $25, but the gear ratio is fixed at
    what Astro feels is appropriate.  
    
    Does the Al-Tec gearbox offer any other benefits such as slimmer
    profile, lighter weight, or more convenient mounting?  Is the shaft 
    in line with the motor shaft?

       
              !Every thing I need to know, right in front of me!
              
    
         Thanks to you all for the valuable info. I do believe I 
      understand what the difference between geared and not is now.
    
        I also just read the RCM review on the American eaglet, and
      yes I agree it wouuld probably be overpowered with a 15 or 25.
      besides I can use the 05 size on a glider too. I still am 
      excited about electrics. As a calibration tech for the last 16
      years I had my doubts, but seeing is believin.
    
     kevin

    I think you made a good decision with the 05. Regarding using it in a
    glider: The german manufacturer MULTIPLEX just brought out an electric
    version of their FIESTA (for details see FIESTA topic). The glider has
    a wingspan of 127.6 inches and a weight of about 70 oz. Guess what
    motor they propose: an ASTRO 05 geared (with a different, not ASTRO's
    gear, though) and a battery of 8 cells.
    
    MULTIPLEX is famous for their gliders, and I am convinced that this
    thing will fly pretty well. It will certainly not climb at a 45� angle,
    though. 
    
    If I only gould find the time to get my version with the Neodymium
    motor and 12 cells going...
    
    
    Regards,  
             Hartmut

    Re: .334 and .335
    
    A few more words about the Al-tec unit:
    
    First of all, let me back up a little bit and reveal my reasoning
    for getting into this unit in the first place.  I, and another fellow
    modeler, had invested in the Davey Kits, he with the Eindecker and me
    with the Fly Baby.  We got the deluxe versions which came with a
    "Ferrite" motor (rated equivalent to an 05 ?, but don't hold me to
    that), switch harness and fuse attached.  Now, the kits are quite nice
    but when we went through the numbers (weight analysis) we both agreed
    that performance was going to be marginal, so we both decided to use
    fuel engines in these models, and use the "motors" for something else.
    
    I happened to have an old scratch built Berkeley Buccaneer that was
    waiting around for the right kind of power assignment, and this motor
    seemed like it would fit in very nicely, considering that I wasn't 
    looking for blistering performance, and the "Old Timer" could certainly
    carry the weight with its high lift wing (and stab).  Of course, now a
    gearbox seemed logical so that I could use a 10 or 11" prop - and
    "Cruise easy".
    
    To answer your specific questions:  Shaft offset will amount to from
    3/32" to 1/8" depending on the gear ratio selected.  You will add 0.9oz
    to the weight of your motor (this includes the prop collet), and 1" to
    1-1/4" to its length.  All in all, it is a very slim and compact
    installation.
    
    The caveat is:  Assembly is required.  The most critical part of the
    assembly is the "Press fit" of the pinion gear to the motor shaft.  I
    used my vise for this, and it went on slick as can be.  I was cautious
    to exert the jaw forces on the motor shaft only, thus not stressing 
    the motor casing or bearings in any way.  I hate to think of what a 
    mess I might have made if I used my usual "Italian Speed Wrench"
    (Hammer).  The pinion gear is brass, other gears are plastic.
    
    All in all, a nice piece of machinery.  Good instructions, including
    a sketch, and spare housing parts to accommodate different size motors.
    
    I can't give you flight results yet, but it has been bench tested, and
    it runs smooth and easy !                                      john

    re .337
    Hartmut, I'll be interested to hear how that Neodymium motor works
    out. Is it the one made by Marx, which is available here, or one
    of the other bramds? I agree that big gliders with small motors
    can work well. I've got a 112", 68 oz. , with flaps, own design,
    Speed 600 motor on 7 cells and 3:1 belt drive, that is a soaring
    fool.
    
    re .338
    Everyone in here probably already knows this but... when using
    a gear box its life can be extended considerably by using a speed
    controller rather than just an on-off power switch. Suddenly
    dumping full power on the gears can wear them quickly or shear them
    off, especially the plastic types.
    
    Terry
    

    Re: Speed controller
    
    Terry, you're absolutely correct.  In fact, the instruction sheet
    that came with the Al-tec unit recommends just what you said.
    They prefer that you go easy with the On/Off cycles if you do use
    a switch, and also - avoid prolonged periods of full power.
    
    Actually, I made a slight mistake when I set up my power train.
    I bought a Graupner Power Switch (w/BEC), which is indeed a fine
    accessory, but I misunderstood the ad and thought it was also a
    propo throttle - which it is not.  In my case however, I don't
    expect a problem because my demands on the power train will be
    quite mild, and I will go easy on the number of power pulses.
                             (I hope)
    
    John

Hmmmm... I hadn't heard of the potential problems of using an on/off controller
with a gear unit. But it sort of makes sense. There must be a great deal of
stress on it when the motor is first turned on.

I think I'll take a look at the gears on my Challenger this weekend. I don't 
expect any trouble; it's a pretty rugged unit.

Dave

    re .341
    
    If you're using an Astro gearbox, then it is pretty rugged as they
    use metal gears. It also helps to keep the gears lubricated. The
    best stuff I've found is wheel bearing grease for disc brake equipped
    cars. It stickier when hot and won't fly off the teeth like regular
    bearing grease. It takes just a film of grease to do the job. Wipe
    off all excess to minimize drag. A small can will last you several
    lifetimes.
    
    Terry
    

    re.339
    
    Terry,
    
    certainly I'll keep you all posted on how the neodymium motor works
    out. But you will need some patience. I don't have much time to work on
    my planes, and I want to finish the RACE CAT before starting the FIESTA
    electric fuse. It will probably not be before fall that I can post any
    flying reports.
    
    The motor I have should be available in the USA as well (as long as
    it's available at all, supply is _very_ short. I waited for half a year
    until I found someone who knew Mr Keller and helped me out). It is a
    Keller 40/10, distributed by ROBBE. It has a slightly smaller diameter
    as a 540 series motor, but is about twice as long. You can look at the
    Robbe catalog (news/Neuheiten 1989) I left with DECRCM last month and
    find detailed specs and a picture.
    
    The motor has a 5 mm (.2") shaft - should be hard to bend _that_ one -
    but when I first tried to turn it by hand on the shaft, I had no
    chance... Then I tried a lab power supply to test run it. I turned the
    current control on, but the motor did not start running up to the max.
    current the PS was able to deliver: 5.0 Amps!!! With another PS, it
    started to run at 6 Amps (breakaway current), idle current was then 1.5
    Amps. With a 11 x 7 Graupner folding prop, it pulled 17 Amps @10 Volts.
    Compared with motor data published by Keller and gathered with a
    similar prop that used 17 A @ 10 V, too, it should draw about 35 A
    at 14 V (12 cell setup), about 500 W. I'm looking forward to see this
    thing working in the FIESTA... 
    
    Regards,
             Hartmut

    Re .342
    
    Terry,
          I wonder if that grease that you speak of would also
    be good for the Al-tec, which, as you recall, has a brass
    pinion driving plastic ?
    
    john

    re .344
     I don't see why not John. I'm using the grease in my Graupner
    gearboxes, which are also brass and plastic. They run quieter
    too. Be careful with the cleaning solvent that you use to clean
    off the old grease, which I do about once per season. Alcohol works
    ok but needs to be scrubbed with a toothbrush. Spray-on contact
    cleaner works too, but again, won't float the grease off without
    a little help.
    
    Terry
    

     
    
        Why not electric powered ducted fans?. I just read in the june
    issue of RCM that there may be an article or two on them. I think
    I would investigate this if the article is favorable. I bet the
    sound of an electric ducted fan (25,000 rpm and up maybe) would
    be different and might even be slightly realistic with a whine!.
    
       Well anyway from the advancements I have seen in DC motors AND
    batteries I bet Elec duc/fans are not that far off. (I can dream)
    
    kevin

    Interesting question, Kevin.
    
    In fact, I'm sure I read in one of the UK mags in the last few months
    that someone asked himself the same question and then decided there
    was no reason why not.
    
    I think he built himself an A10(?) -- I think it was this plane
    -- that's the one with twin fans high on either side of the fuse
    behind the wing?
    
    If you're interested let me know and I will try to dig out the article
    which made the mention -- it was a very brief piece though!
    
    Regards
    
    Brian
                            

    re: .346 electric powered ducted fans
    
    
    In a special edition of the German FMT magazine about electric flight
    they had an article last year about ducted fans (even some unducted
    fans!!!). So, yes, it has already been done, and yes, there are lot's
    of problems. 
    
    The problems I remember: With the high rpm's, there is no advantage of
    using rare-earth magnet motors (cobalt or neodymium). Since these
    material are conductors, the losses due to eddy current in the magnets
    eat up the advantage of the high-power magnets. This, btw, explains why
    rare-earth magnet motors didn't make their way into boats and cars yet.
    If you turn over 20,000 rpm, there is no significant difference or even
    a disadvantage compared to a cheap ferrite motor.
    
    So you have to stay with ferrite motors, and the ones the guy in the
    mag used where cheap and only lived for a few flights. Maybe this is
    becoming better with all the new motors, with ball bearings etc., but 
    demagnetization with heat and high load (high magnetic field from coil 
    = high current) is a common problem with ferrite magnets. Not sure if
    you can overcome this problem with a top of the $$$ ferrite motor.
    Maybe it is still the easiest solution to change the motor every once
    and a while.
    
    Second thing is, you have to build _VERY_ light. A ducted fan has a bad
    efficiency at low airspeeds, so starts are very critical. Maybe  some
    kind of hi-start rubber (catapult) would help. I seem to recall that
    the first gas powered ducted fan ships where started with this help,
    too.
    
    But the idea is neat, and I agree, they are not far off. If you would
    like a copy of the article (german text, though), send me mail.
    
    Regards,
                Hartmut

    
    
             German text! , I didnt do that well in school. Even
      my english has it problems. Seriously if I find someone who
      is capable I'll give you a holler. I am interested, and who knows
      maybe a few of these "problems" can be solved with experimentation
      and that is one reason I love this activity. (although some people
      might very well remove themselves from the flight line when an
      homemade experimentor shows up). 
    
    kevin

    I am considering building a Graupner Elektro-UHU.  Does anyone
    have any experience/opinions regarding this electric glider?
    
    Thanks,
    
    Jim

    re .350
    
    I've examined the Uhu kit closely, and have seen one fly, but haven't
    built or flown one myself. Also I'm using the same motor/prop on
    several other planes. Based on all that, my impressions are:
    
    Kit quality is typical Graupner ie excellent. Plastic fuselage is
    a big plus for durability.
    Wing loading is fairly high for this type of plane, by American
    kit standards, but routine for German kits. Don't recall the 
    exact number but it's around 11/12 oz.
    
    It flys fast compared to an Electra or even a Challenger, and isn't
    at it's best in light lift, but can cover a lot of area looking
    for lift.
    
    The stock Speed 600 motor with 7X3 prop gives good performance
    on 6 cells. I'm not sure there is room for a 7 cell pack (900mAh)
    It looks too tight to me. However, if there is room for 7 cells,
    then a Speed 500 motor and 8X4.5 prop will give a real boost in
    performance. The 500 on 6 cells and 7X3 will still give a boost
    over the 600, but not as dramatic.
    
    So if your looking for a fast, zippy sort of flyer that can thermal
    with a little extra effort on your part, then the Uhu is for you.
    
    Terry
    

>                      <<< Note 387.350 by USRCV1::BLUMJ >>>
>                         -< Graupner Elektro-UHU info >-
>
>    I am considering building a Graupner Elektro-UHU.  Does anyone
>    have any experience/opinions regarding this electric glider?
>    
>    Thanks,
>    
>    Jim

I have seen a couple and talked to at least 4 people who fly them
I personally was skeptical because to me the "high" tech plastic
fuselage seemed like it would break right away and in general ARF
types don't fly well.  I still think they look cheap but...

Everybody who has had one loves them.  They also can take a beating
and keep on flying.  The only negative thing I've heard owners
say is "They fly real fast"!

So while I personally would not get one (today!) I would advise
you to get one if you think you like them and are ready for a bit
of a fast glider.  By definition most electrics require faster
landing speeds because of the higher wing loading so that is no
big surprise.

Other opinions/observations?

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

    Thanks for the quick response on my UHU questions.  Maybe you guys can
    help me with a few other considerations.  I have never flown an
    electric, I am considering getting into it so I can fly at more sites.
    The high start has become cumbersome to use when other power flyers
    are at the field.  I am the the only glider flyer at a field with 35
    power-only flyers.  I am into my third year of RC gliding.  The hottest
    sailplanes I have flown are 2-meter sagitta and 2.5-meter Gemini.  I am
    open to suggestions of a good electric.  The ships that look
    interesting are: UHU, Graupner Pink or Silentius, Kyosho Stratus 2000.
    Any other suggestions would be welcomed.  Tom, could you expound on
    what you mean about the UHU thermalling if "you are willing to put in a 
    little extra effort".  Thanks again for the suggestions!
    
    Regards,
    
    Jim

    Jim,
    
    What I meant about "a little extra effort", is that the Uhu is not
    a slow, floater type sailplane that responds to the slightest lift.
    You have to agressively seek out the best lift in the area, and
    be willing to fly out further and faster from your launch point
    looking for it rather than moping around the immediate area hoping
    something will blow through. In other words, exactly the same technique
    you would use for any higher performance glider, electric or not.
    
    Any of the Graupner kits would be good choices. The Silentius is
    an older design with a balsa fuselage. I've seen the pure glider
    version of the Kyosho fly. It seemed okay but has a more "arf-ish"
    quality about it. Dollar for dollar it's hard to beat the Thermic
    Traveler converted to electric. It's an old Frank Zaic design
    from about 1940, with several aerodynamically old fashion features,
    but with an E-205 airfoil. It has plenty of room for all the electric
    stuff, easy to build, and is $31 from Hobby Horn in Calif.
    For some reason this thing flies like crazy, fast yet thermals well
    at 12.3 oz. wing loading, easy to build and distinctive looking.
    It's my favorite among my present electrics
    
    I can sympathize with your field conditions. Personally, I won't
    fly gliders at a power field. Nor are power planes allowed at our
    field, although for noise reasons not personal politics.
    
    Terry
    

        Jim,

        as stated in several places in this notesfile, I am a proud
        owner of an Elektro-UHU, and I just love it.

        As was said before, it is fast and therefore not a beginner's  
        plane. I built it to learn how to fly again (had laid off for  
        about 7 years), and it didn't give me any problems. It builds  
        very fast (simple wing design, less than 10 parts to complete  
        the fuse with fins). Repairability is not a problem, you get   
        the fine plans GRAUPNER is famous for, and you get english     
        instructions, too. The fuse is hard to break and easy to glue. 

        It is probably correct to say it's a glider, not a sailpane
        (as per the recent definitions from trivia).

        I fly mine with the stock motor (Speed 600, I think) and a
        6-cell SANYO 1200 SCR pack. Motor control is by the Robbe 
        control 7 electronic switch with BEC. 

        There is room for a 7-cell 1200 pack. You even have enough      
        place for standard size servos (was a criteria for me). With 7  
        cells it's certainly a lot hotter, but the runtime will be      
        shorter. Didn't try it yet. I have no experience with other     
        motors and props yet (although  I'm just considering to try it  
        with an ASTRO Cobalt 05 this  weekend). The bearings of my      
        stock motor are worn after a year of  flying a lot. A BB motor  
        might be a reasonable investment.                               

        The UHU is capable of basic aerobatics (loops, turns, even
        inverted flying if the pilot is able to do it with rudder
        only, I am not - yet). You can do some interesting flying 
        near the ground with a bit of practice, I enjoy that a lot.
        The behaviour of the plane is very predictable. Getting down
        from high altitudes (in case you caught a brick carrying thermal)
        is no problem, the plane is rigid and can take high speeds. No
        problem with gusty winds either, because of the high wing loading.

        The plastic fuse is good. It doesn't look as nice as epoxy fuses,
        you see the seam, and the surface is not too smooth, it likes to
        get (and look) dirty, but it is elastic (as long as the temperature 
        is high enough. I only broke it once by unfortunately landing in a 
        freshly ploughed = rough and frozen field. But I was able to glue it
        again.

        What I like most is that the Elektro-UHU is for me the best plane
        to go flying if you don't have much time. Since transport, assembly
        and starting is so easy, you can get four nice flights in only an 
        hour of time (with 2 batteries, that is). Normal flight time is about
        12 minutes (1/3 powered, 2/3 gliding). With acrobatics close to 
        earth this can come down to 5-6 minutes. My best thermal flight yet
        was about 35 minutes. Hope to improve that this weekend, weather
        permitting.

        There are two things that could be improved during construction:

        1.) I broke the elevator on the second hand launch. It is very soft 
            (light) balsa, and has a weakening slot in the middle for the
            rudder. If it gets hit (common on landings), it must break there.
            I built up a new one without the slot (cut the slot into the 
            udder fin) with reinforced it with thin ply. No problem since.

        2.) I like the mounting of the wing with Nylon bolts, but many
            people don't, especially beginners. You can easily change to 
            the conventional dowel and rubber job, if you like. In this
            case, don't forget to reinforce the wings.

        Graupner was so successful with this design, that they          
        use the same fuse with other wings for other purposes. If you   
        would like to do more aerobatics, have a look at the CHIP with  
        a slightly smaller wing (span 1.5 or 1.6 m, what you prefer,    
        UHU has 1.7 m). It's got a one-part aileron wing. And there is  
        the JUNIOR with a bigger wing (2.0 m, I think) which should     
        glide (soar?) better. If you have a chance, look at the         
        catalogues I donated to DECRCM (ask Dan Miner). I think there   
        was even another one in the News of this year (maybe not yet    
        published yet in the US, but probably not yet available even    
        in Germany).                                                    
                                                                        
        If I can help you any further, let me know.                     
                                                                        
        Regards,                                                        
                 Hartmut

    Boy, this decision is getting tougher and tougher, and since it is
    going to cost $300, I would like to make an intelligent choice.  I
    really like the look of the UHU and have read many good things, both
    in this notes file, and in magazines.  My reservations are as follows:
    (1) I have gotten 3-meter sailplanes up so high(not often mind you!)
        that I could barely see them, hence I am worried that the UHU
        with it's 450 sq. in., 66 in. wing would be very difficult to 
        see.
    (2) I get the impression the UHU is sort of hot-dogging fun glider/
        airplane rather than a serious thermalling machine.  I must admit
        this apeals to me, but if this ship falls quickly out of the air
        due to a high wing loading it might not be for me right now.
    (3) My past experience say's the bigger they are, the better they seem
        to fly/thermal.  Again the 66in. span worry's me.
    
    
    Tom, was it the Kyosho Melody or Stratus 2000 you saw fly?  The Stratus
    is 2-meter and employs the Selig 3021 airfoil.  My reservation with
    this ship is I have heard bad things about Kyosho's motors not having
    enough guts to give good performance.  I was impressed with the 3021
    on my Algebra.  With its bigger wing(78in. vs. 66in.) and the
    polyhedral Selig airfoil, do you guys think the Stratus 2000 would
    thermal better than the UHU?
    
    For some reason I guess I get the impression the 2-meter polyhedral
    ships (ie Stratus 2000, Pink, Silentius) would outthermal the UHU
    and probably be easier to fly because of lower wing loading and the 
    polyhedral wing.  I just get the impression that everone is saying
    "the UHU is great,but" with the but being it is fast and requires
    superior skill to keep it up when the motor is shut down.
    
    Additional comments/suggestions would be very much appreciated.
    
    Thanks,
    
    Jim

        Jim,

        I think about the Elektro-UHU you got the right impression. It
        is a perfect plane (no but) for what I wanted it for: resume
        flying after some absence and having fun with reasonable effort.

        If you're looking for planes that stay up after the motor is shut
        down, there are better choices than the UHU (it doesn't fall out
        of the sky, it glides at a reasonable angle). Even if you find
        a good thermal, it takes some effort (or practice) to keep it in there,
        and with the relatively high speed, you are forced to fly circles
        with bigger diameter (= lower uplift) than with ships designed for
        that.

        Just for comparison: GRAUPNER's MOSQUITO, a 100" span ship, was
        originally powered with half the power of the UHU. The design was
        more critical, didn't give much room for errors, but showed great
        performance in thermalling and had about twice the motor run time
        (again with a relation 1:2 powered flight/gliding time).

        You would want a plane in the 80 - 100" range, powered by max.
        7 cells (to keep the cost for the charger down) and a geared
        motor, as light as possible. This one would be a lot easier to 
        break with higher speeds (getting it out of a thermal) or rough 
        landings. I once had a 110" glider with a scratch built MOSQUITO 
        fuselage, driven by the JUMBO 550 G3, 10 cells and a three bladed 
        prop. Had lots of fun with it, caught several thermals, but managed 
        to fold the wings while trying to escape the best thermal it ever 
        had. Wings were built without electric power in mind, though.

        If you're looking for this kind of plane, I strongly suggest you
        consider some kind of 'airbreak' to keep the stress down while
        descending. A neat idea is to just reverse the motor current. The
        plane will go on it's nose and descend safely.

        Regards,
                 Hartmut

    1. No doubt that a small airplane is harder to see than a big one.
    High altitude speck'ed out thermalling is not the Uhus' forte. I
    don't think it was designed with that in mind. If you want to do
    that sort of flying most of the time, then it wouldn't be your best
    choice.
    
    2. Higher wing loading translate into higher flying speeds, not
    necessarily into greater sink rates. The Uhu can cover ground
    more quickly than the other planes you mention. If it encounters
    light lift while doing so, it may not react as noticebly as a 
    slower plane. This is about as much as you can generalize.
    
    I saw the Stratos fly. The owner had removed the motor, precisely
    because he was dissatisfied with its performance. The stock motors
    that come with the Electra, Eclipse , Stratos, etc. are all barely
    adequate. Your best bet is to buy the bare kit that comes without
    the motor, then get a Graupner Speed 600 or 500 with Graupner
    Scimitar prop. Total cost will be about the same, and performance
    will be much improved. Of course a cobalt 05 will work fine too,
    if you don't mind the 4-5X cost increase.
    
    The problem with polypropelene plastic fuselages, is that they are
    a b**ch to fix. They don't like most epoxies, etc. The German plastic
    fuselages are apparently some other type. I've had good luck repairing
    them with epoxy.
    
    If your looking for a large, thermalling type of electric your
    options are limited for <$300. The Aeronaut "Aerofly", in the
    Hobby Lobby catalog has a good reputation, at 100" and $120,
    it may be in your range.
    
    Terry
    

>    Boy, this decision is getting tougher and tougher, and since it is
>    going to cost $300, I would like to make an intelligent choice.  I
>    really like the look of the UHU and have read many good things, both
>    in this notes file, and in magazines.  My reservations are as follows:

You may not realize it yet but your mind is already made up.
Since you like the LOOK of the UHU then GO GET IT!

If you don't you will always be wishing that you did.

It isn't a large floater but it should be fun and you could place
your order TODAY!

When I was in the Navy I was trying to buy a new television.  I was looking
at the new (then) Motorola Quasar and the Heath kit.  I was reluctant to
get the Heath kit because I was a bit afraid that somehow I might not
build it right or...

Anyway this chief I worked for just bought a new motorcycle and he said
"Do you want the Heathkit?" Sure I said but... Then he said "Can you afford
the Heathkit?"  Sure I said but... Then he said "Well then go buy the
damn thing - I didn't need a motorcycle but I bought it - why - BECAUSE
I WANT IT!

I ordered my Heathkit that night.  Was it the RIGHT decision?  Hard to say,
but one thing is for sure - If I didn't get the Heathkit I always would
have thought I should have.

Besides most of that $300 is for parts that can be used on another model
another time - right?

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

    Well after thinking about everything contributed in this file, I have
    ordered the Elektro-Uhu.  The new Hobby Lobby Catalog came, and had 
    nothing newer or better(I had heard Graupner was going to  come out
    with a 2-meter version of the UHU, but they apparently didn't).  After
    reading three different reviews and hearing all your views, nobody
    really had anything but good things to say about it.  But like Kay
    said- This is what I really wanted anyway!  I spoke with a guy at
    Hobby Lobby and he said that they were getting 2min.20sec run time
    on their Uhu's.  This results in three climbs to 500ft. before
    recharge.  Sounds good to me.  I'll provide a construction and flight
    review hopefully in the near future.  By the way the total cost of this
    kit with the lowest priced quick field charger was $231.00.
    
    Regards,
    
    Jim

    My Elektro-Uhu kit arrived and it looks like a great kit.  I have
    always wondered what a Graupner kit was like since they are pricey
    compared to American manufactured kits of similar size.  This really
    is a quality kit, the die cutting was so good all the parts easily
    came out.  The wood is top quality with the stab and rudder being
    cut to shape.  The kit even came with glue and hinging tape.  For
    a person with limited building time I think it is worth the extra 
    money.
    
    Regards,
    
    Jim

    Jim,
    
    have you decided yet what motor/battery combo you are going to use on
    your UHU? This can make quite a difference, and you can adapt the plane
    a bit to what you want to do.
    
    The fuse has enough room for six or seven cell packs. With a bit of
    thinking, you can probably fit even bigger packs. I equipped mine with
    six cell packs because I wanted the lower weight/longer run time. I
    used the stock motor (SPEED 600) without extra ring. After a year with
    a lot of flying, the bearings are worn pretty much, and since I don't
    make much progress on building the RACE CAT, I recently mounted the
    RACE CAT motor into the UHU (SPEED 500 BB RACE). What a difference!!
    The plane is a lot quieter and faster! Because the UHU is not a speed
    plane, I installed an extra iron ring around the motor which reduces
    current and rpms, but increases torque. I only flew it one evening
    since, and I liked it a lot. Flight time is not increased too much,
    the better efficiency of the BB RACE motor is pretty much used up by
    the plane's aerodynamics, but it is fun.
    
    The SPEED 500 BB RACE is quite an expensive motor (about 60 $ in
    Germany), but if you want to go into this direction, a normal SPEED 500
    BB might be a good idea.
    
    If you are not interested in speed, but prefer max. flight times, you
    want to use a motor with lower rpms and higher torque and a bigger than
    the stock 7x3 prop. You might even consider a geared setup. I had an
    article about that, but I'm afraid I loaned it to someone and didn't
    get it back yet.
    
    My point is: The stock battery/motor/prop combo is a good and cheap
    point to start at, leaves room for some errors (plane will fly
    successfully even when it's not as light as possible etc.). But if you
    want to do more aerobatics or flights as long as possible, there are
    ways to improve the performance easily in either direction. Let me know
    if you need further inputs.
    
    Regards,
              Hartmut

    I've read more than once about the German motors using the iron rings,
    but for some reason I don't remember any mention of using them with 
    the more common motors in the U.S..  
    
    Seems to me that improved flux density should improve the overall
    efficiency of the motor, but how much do you gain after allowing for 
    the added weight?  Does anyone out there know enough about the 
    technology to tell us when the rings are most effective?  Does magnet 
    type significantly effect the result?  

    hartmut,
    
    i am still building my UHU.  I purchased the standard motor(speed 600
    i believe), but was talked into a seven cell 900mah battery by the
    folks at Hobby Lobby(US Graupner Distributor) rather than the standard
    six cell Sanyo show in the Hobby Lobby catalog.  I will let you know
    how this combination works out, hopefully in the near future.
    
    regards,
    
    jim

    re last few
    
    I'll agree 100% with Hartmuts' recommendations. I use the Speed
    500 plain bearing motor (about $15 from H.L.) with a 8 X 4.5 prop
    and overall climb performance is equal to a cobalt 05, while still
    giving good duration, compared to the stock 7 X 3. I havn't tried
    the stator ring on that combo, but on my Speed 600 setup with 3:1
    gearbox and 11 x 7 folder, I use the ring and can notice an increase
    in "pulling power". Ring weight is trivial. It's only 1-2 mm thick
    and seems to be made from steel not iron. I have the Graupner model
    sized to fit the 500 & 600 motors. I've found that the Sanyo 900mah
    SCR cells give the best all around performance/duration compromise,
    and always use 7 cells. 
    
    Terry
    

    This question rightly belongs in the glider notes(399 or 337) but they
    have been so inactive I will ask it here.  I am quite impressed with
    the Elektro-Uhu kit and wonder if anyone has built any other Graupner
    kits.  I have a Multiplex Fiesta about 80% complete and have found it
    much tougher to build than the Graupner kit, especially in terms of
    the prefabricated parts supplied.
    
    Regards,
    
    Jim

    I've built two Graupner Cirrus', long since out of production, and
    an ASW-22, currently available in both foam and built up wing versions.
    I did the built up wing and electrified it. Graupner kits are of
    consistently high quality and are comparatively easy to build, due
    to the well engineered fittings. The exploded drawings of the structure
    can be a life saver when trying to puzzle out some oddity in the
    English translation of the instructions. I'd build another one in
    a minute if I didn't have so much other stuff in the pipeline.
    
    BTW electrifying the ASW-22 is a real pain, getting everything to
    fit in the available space, is 75% of the work.
    
    Terry
    

I built a couple of Amigo IIs about 15 years ago and used a Cox .049 power pod 
out of a small field to fly them. The kit was beautiful and included all the
accessories and glue (dry in a packet to have water added ;^) I broke one wing
in a killer thermal (trying to get out) and it repaired easily and it sits 
waiting for a radio to come available. They're definately worth the money you 
pay for them.

        Rings are not only used on German motors, the only one I have
        (yet) is delivered by GRAUPNER for the SPEED and Mabuchi motors.
        I think, this one is even less than 1 mm thick, and it is made
        of (call it iron or steel) magnetically soft material. 

        How does a ring work?
        ---------------------
        If you make up a simple sensor out of two soft-magnetic bent 
        wires (paper clips for example), you can easily detect magnetic
        flux leakage around the motor housing.
                     ___________  ___________
                     |       \  \/  /       |      (clips hanging together)
                     |_______/__/\__\_______|

        The ring is a conductor for magnetic flux. With reinforcing the 
        housing, it increases the flux in the housing and therefore in the
        gap where the coil rotates, too. Since torque is directly 
        proportional to the magnetic flux, motor torque increases.

        The max rpm of the motor is where the voltage it induces (as a 
        generator) equals the voltage supplied. Since the induced voltage
        grows with higher magnetic flux, you reach the supplied voltage at
        lower rpms ----> the rpms decrease. And with lower rpms, the 
        current decreases, too.

        With appliance of rings, you can easily change motor characteristics.
        It is very cheap, too (my ring cost about 1 $). You can add even two
        or three rings and you will see an effect until you can detect no
        more flux leakage.

        But it is hard to calculate or consider how it will affect overall
        flight performance. What does increased torque/decreased rpm do
        to the efficiency of your battery/motor/ring/prop/plane combo? It
        depends very much on the kind of plane and your style of flying.
        Just try, make your experiences and let us know.

        My point in using the ring was that the RACE motor is developed for
        race planes (= high speed). Since the UHU is not a speed plane, I
        thought it might be a good idea to increase torque and reduce speed
        in order not to overload the motor and reduce it's efficiency.

        People have done lots of measurements with different props, different
        batteries, different numbers of rings. When you measure rpms, current
        and thrust, you certainly get a good picture, but you never really 
        know what happens in flight. ROBBE-KELLER supplied excellent data
        sheets with the 40/10 motor I have for my Multiplex Fiesta. With this 
        motor, the tradeoff seems to be reasonable to use a ring, at least
        in the motorized glider application. I will order one as soon as the
        plane gets into it's final stage, and I'll keep you posted.

        Regards,
                 Hartmut

        P.S.: BTW, Jim, my FIESTA glider had it's first hand launches last
              Wednesday. Since Kay would not consider this flights, I did
              not report them yet. I was very happy, though, and am looking
              forward to flying the ship from my new MAGNUM hi-start or on
              a slope. I'll certainly post experiences as soon as I have a 
              chance to fly it again.

              I think you can't compare ease-of-build of the UHU which is
              meant to be a beginner's plane and the FIESTA. Most of the
              FIESTA hassle for me was installing ailerons (with wing-mounted
              servos) and the spoilers. This is probably a lot of work in
              GRAUPNER kits, too. I was happy with both of the kits.

Are the rings themselves magnetic? We have flexible sheets of magnetic material 
that I could wrap into a layer around my motor. Is that the general idea of the 
rings or would I want to do it with a non-magnetic ferrous strip??

    Jim,
    
    no, the rings are not magnetic themselves. They are soft magnetic
    (ferromagnetic?) material, I assume mostly iron that is somehow
    protected against corrosion. With a magnetic layer you would probably
    add more problems (locate the poles correctly etc.). And you would load
    the housing of the motor with even more flux.
    
    What you want is a material that conducts magnetic flux. This increases
    your flux because the motor housing is usually saturated (that's why
    you see flux leakage outside). You reduce the magnetic resistance of
    the yoke and increase the flux (magnetic current if you want an
    analogon). If neither Hobby Lobby (nor any other shop) carries these
    rings, let me know for what diameter and (magnet) length you need it,
    and I'll try to dig one (or more) up for you.
    
    Regards,
             Hartmut

    Now that it has flown, I can comment (from a beginners perspective) on
    the Amptique.
    
    Construction is quite simple, being a polyhedral built up wing with 
    two 3/16" spars and no leading edge sheeting.  The fuselage is 1/16"
    sheet with 1/8" stringers, and the stabs are built up with 3/16"
    elevators and rudder.  Designed for a Leisure geared 05 motor, its
    quite light, and though not a real sailplane, will thermal happily, do
    consecutive loops, and is generally regarded as a good trainer, with
    characteristics similar to an old-timer.  The plans are very good, 
    though the four pages of intructions leave out a lot for a trainer.
    
    I made some modifications that were suggested by flyers who had
    experience with the plane.  The spars in inner wing panels were
    replaced with 3/16" spruce, a scoop was added for additional cooling,
    the landing gear was made both longer to clear a 12" prop, and
    removable, as is the tail wheel.  Downthrust was increased from three
    degrees to five.  
    
    Additionally, I had to rearrange the firewall and some of the cross
    pieces because I was using an Astro geared 15.  Although I planned to
    use only eight or ten cells, I allowed space and checked the balance
    with a twelve cell pack.  The nine inches under the wing are consumed
    by the motor battery, Futaba Attack receiver, 133 micro servos and a 
    250mah flight pack.  That leaves less than three inches behind the
    motor to stuff a speed control and all of the wiring.  I got nervous
    about the 3/16" balsa for pushrods, so I went and found a stiffer 
    piece at the local hobby shop.
    
    As it turned out, I went ahead and flew with the twelve cells
    installed.  No trim adjustments were required at all.  At full
    throttle, it climbs at a steadlily increasing angle, in excess of 40
    degrees, unless you apply some down elevator.  With the motor off, it 
    noses down into a gentle glide.  Even with the extra cells for ballast, 
    it will practically hover with a fifteen mph head wind, needing some 
    motor power to make forward progess.
    
    With four flights and two landings behind me, I'm delighted with the
    plane.  It flys slow, responds gently, and best of all, is still in one
    piece.  After I get more experience, I'll try less cells and see how it
    differs.
    
    The only problem encountered was some glitching in the SC5 motor
    control at 3/4 to full throttle.  It has chokes in the servo lead, but
    they are over seven inches long.  Next time out, I'll try adding some
    twist to the lead and see if it helps.  Whatever, I'll have an SC4
    ready to replace it as soon as I get some good monolithic capacitors 
    to replace the junkbox ceramics I tried using.  
    

    re: -several ago...
    
    I have seen Graupner in Hobby Lobby catalogs for several years and in
    person at several MARC shows (Timonium, MD).  This "Perfect
    Fertigrumpf" fuselage scares me.  I have visions of an unrepairable
    Kyosho Melody fuselage made of a semi-flexible plastic that was
    impossible to work with.
    
    My question is this:  Is there someone out there with experience with
    this stuff from Graupner?  Is it better than the Kyosho material?
    
    The MARC show is this weekend, and I'm sure to be real tempted!  Thanks
    in advance for any info.
    
                        __|__                              Regards-
 \________________________O________________________/       Frank.    

    

    Most of the NON-fiberglass, but not wood fuselages can be repair with a
    product called NIBCO's HOusehold Welder, it is similar to SHOE GOO, the
    stuff that you fix your NiKE's with.  I would not be that affraid of
    it.
    Besides you dont plan on crashing it do you???
    

    re .373
    
    I've had some experience with the later model Graupner fuselages.
    It's not the same type of plastic as the Kyosho stuff, as far as
    I can tell. It's thicker, less slick feeling, and can be repaired
    with epoxy, especially if you drill small holes along each side
    of the break and apply a fiberglass bandage over the area after
    applying epoxy to the break and forcing it into the holes.
    CA will dissolve it, the same as most plastics, but this can be
    useful in small breaks, as you can literally weld it back together.
    
    The old Graupner fuselages were made from ABS, which is better than
    the new stuff, but too expensive as it requires tooled, high pressure
    molds to make the parts. I've heard that Graupner spent ~$200K on
    the molds for the original Cirrus fuselages. The ABS kits came
    with UHU-Hart glue, solely for joining the fuse. seams. and ABS
    root ribs.
    
    Terry
    

    
    
    Although I consider the appearance of the fuse not perfect (in
    comparison to a fiberglass fuselage), I had no problems with gluing or
    repair. GRAUPNER recommends UHU-Hart for gluing the wood parts into the
    fuse, and this works pretty well.
    
    Flexibility of the fuse is very nice under summer flying conditions.
    The material is forgiving and able to withstand some abuse without
    breaking. But be aware that the material gets brittle at freezing
    temperatures. As I said somewhere else, I broke the tailfeathers off in
    a hard landing on a ploughed and frozen acre last winter. I repaired it
    with epoxy and had no problem since, even when I "landed" with wings
    vertical recently due to a bad gust during turn into final. The plastic
    screws popped off, the parts fell to the ground. Just the servo tray
    had separated a bit from the fuse, but that was a 15 minutes (charge
    time) field repair with UHU-Hart, and it flew again. No damage to the
    tail-feather joint.
    
    I have no experience with Kyosho material, but there is no reason to
    stay away away from GRAUPNER Perfect-Fertigrumpf because of
    repairability. Just avoid flying below 0� C when you're not sure enough
    you can grease the landings but still want to keep the plane in one
    piece.
    
    Regards,
             Hartmut

    I discovered a few weeks ago, thanks to a blurb in RCSD, that there
    will be electric glider events at the NATS. No mention is made of
    this in the Nats schedule sent out to entrants, or in any of the
    publicity in the mags, etc.
    
    Three events will be held; An F3E type limited to 7 cells, the Calif.
    flyers have this event nailed down so no point in entering.
    
    A 7 cell duration event- 3 rounds, 8 minute duration with circle
    landing only in order for the duration time to qualify- ie, no spot
    landing. I've decided to enter this event. The Thermic Traveler
    is competitive, not so sure about the pilot.
    
    Unlimted ( max of 30 cells) duration, same as above. I don't
    have anything to fly in this event but should be interesting to
    watch.
    
    All electric events will be held at the same site as the pure glider
    events, Lincoln High School in Vincennes, Ind. on tuesday, July
    17 after the HLG events are concluded. Should be fun, the CD is
    expecting 150+ entrants.
    
    The usual grumbling is arising from the glider guys concerning
    the flying site, concerns about insufficient space as well as the
    usual gripes about AMA slighting the glider entrants who make up
    the largest single class by far, at the Nats, and some talk
    about splitting off and having a separate Soar-Nats next year as
    has been done a few times in the past.
    
    In the meantime I've got all my bureaucratic details in order,
    red streamer and channel # on my antenna, properly sized and located
    AMA #'s on my wings, chartered club officer badge sewn on my cap,
    and am ready to plunge into the political maelstrom. Is this a fun
    hobby or what?
    
    Terry
    

    Just discovered that an Airtronics 6 chan. FM rcvr. will fit in
    a Thermic Traveler and still leave room for a 180 mah pack.
    Whether my old Futaba AM system would get through the AMA freq.
    inspection at the NAts was a concern, and the 4 chan. micro rcvr.
    ability to withstand the freq. congestion is questionable, but 
    now I don't have to worry. Have already swapped servo plugs and
    switch and stripped the duct tape off the bottom of the fuselage.
    I understand they have something called *grass* to land on back
    there. Weird.
    
    Terry
    

    Ever since I started flying my electric, I've had a problem with motor 
    noise interfering with the speed control and the servos.  At first it 
    was an occasional burp, but it got worse over time, and nothing I 
    tried would cure the problem.  With the motor off, a range check of 
    over a hundred feet was no problem.  With the motor on, at ten to 
    thirty feet the speed control and servos would begin to hunt.

    This weekend I went to a local fun fly and talked the problem over with
    Bob Kopski.  He remembered my radio, and had installed chokes in the 
    leads of the original speed control to solve a noise problem prior to 
    including the plane in the KRC Electric Fun Fly raffle.

    After examining my installation and listening to a history of my 
    problem, he was confident that the receiver was at fault.  I was 
    leaning toward that diagnosis myself, but needed some confirmation 
    before ordering another radio and shipping this one off to Futaba for 
    repair.  After all, there are lots of electric flyers with cheap AM 
    radios who have no problem whatsoever.

    While discussing the problem, he mentioned that he and Keith Shaw have
    both found that perhaps half of the Futaba radios are overly sensitive
    to motor noise.  Some bottom of the line ATTACKs run fine, and others 
    won't work at all, or need chokes and extra motor capacitors.  At this 
    point, he has not heard of Futaba admitting to the problem, or any 
    specific diagnosis.

    We'll see what Futaba has to say when I send in my radio.

    
    
       Bob,
    
              I'll be waiting for an update, as I have experienced
       what I think is the same problem. My radio is a futaba 7FGK am
       and for the first 2 doz flights with an electric motor on my
       glider there was no problem. Then I started crashing, range
       checks were good. I checked with the motor running but it's
       hard to tell from a hundred feet is there was glitching.
    
           I'm waiting for october to send it in for the upgrade as
       I just can't see storin my favorite radio. (even if its AM).
       I am busy building new planes so I can chop wood in the winter.
    
     kevin p

    If you're not sure that you have a problem, you probably don't.  Or
    better put, it doesn't sound bad enough to cause crashes, and you can 
    solve it with less than heroic measures.  Since you are about to 
    replace your receiver, you've got at least a fifty percent chance of 
    coming out clean.
    
    The range tests on my plane were done with the transmitter sitting on
    the ground with the antenna collapsed, and the motor running at very low
    RPM.  As I walked away from the transmitter, the speed control (JOMAR
    SC4) would start to burp.  A few feet farther, and it would abruptly
    swing from full on to very low speed, and the servos would twitch,
    hunt, and sometimes run all the way to full throw.  Shut off the motor
    with the safety switch and everything would settle down.  Turn on the
    motor switch and everything would go nuts again.  Tests with a switch
    in place of the speed control, would produce results that are
    essentially the same.  The maximum distance before the problem appeared
    varied with the location and other sources of noise, but were usually 
    fifteen to thirty feet.  With someone flying on the adjacent even
    numbered channel, I got all of about seven feet with the motor running,
    and ninety or a hundred with it shut off.
    
    If your commutator and brushes are still in good shape, and you see 
    an occasional glitch, try adding chokes in the leads to your speed 
    control, increasing the size of the capacitor(s) on the motor, and keep 
    all of the motor wiring away from the receiver antenna.

						 __
				|      |        / |\	   	       
      	         \|/		|______|__(o/--/  | \	   	       
      | |        00	       <|  ~~~  ____ 04 ---- | --------------------
    |_|_|        (O>o		|\)____/___|\_____|_/	   Adios amigos, Al
      |     \__(O_\_	        |	  |___/	 o	   (The Desert Rat)

    A GREASY, NOISY, FOSSIL FUEL CONSUMING RELIC OF DAYS GONE BY?
    
    Nah, I'd rather lug Sears biggest deep cycle.  I haven't even been able
    to maintain the motivation to fire up my Fox .35s from the fifties. 
    Since I haven't built or bought a muffler yet, my neighbors are going
    to love it when I do.  Should be even better than when we wore a circle
    in the backyard testing the dirt bikes.  ;^)
    
    Besides, my problems are minor compared to all of those nice scale
    planes I watched go lean on the first turn over the trees at Rhinebeck!

    
    
        Greasy old gas engine?. pew pew !! 8-)> 
    
    
     Al,
           Really I do have a collection of em, and I will fly 
     with them again. Just a matter of time.
    
    kevin p

    Well I flew the Graupner Elektro-Uhu this weekend.  Overall I was very
    impressed.  I need to work on my power on climbing technique, however.
    I have a question on charging the battery pack.  I purchased an Aristo-
    Craft AC/DC charger and it did not come with any instructions.  It has
    an ammeter and current adjust potentiometer.  When charging from AC,
    adjusting the potentiometer to deliver full current results in initial
    current draw of approx. 2.5 amps which decreases to less than 2 amps
    during the half hour charge cycle.  When charging from my car's battery
    the initial current draw is less than 2 amps.  The run time of the
    motor is substantially less when charged from the car battery.  The
    battery pack in question is 7 cell 900SCR.  Can anyone tell me the
    right way to charge this battery and why the run time is much less
    when using the DC charging feature of the Aristo-Craft Charger.
    
    Thanks,
    
    Jim

>    I have a question on charging the battery pack.  I purchased an Aristo-
>    Craft AC/DC charger and it did not come with any instructions.  It has
>    an ammeter and current adjust potentiometer.  When charging from AC,
>    adjusting the potentiometer to deliver full current results in initial
>    current draw of approx. 2.5 amps which decreases to less than 2 amps
>    during the half hour charge cycle.  When charging from my car's battery
>    the initial current draw is less than 2 amps.  The run time of the
>    motor is substantially less when charged from the car battery.  The
>    battery pack in question is 7 cell 900SCR.  Can anyone tell me the
>    right way to charge this battery and why the run time is much less
>    when using the DC charging feature of the Aristo-Craft Charger.

Jim - I'm in the same boat.  I have a cheap ($75) Pro-Tech charger
and when I charge the charging current drops (doesn't remain constant)
and although I can start at 4 amps on my car battery after about 3 minutes
I can't get that much out even with the current adjust all the way up.

In my case AC is worse.

The bottom line is these 7 cell packs present a problem to chargers
unless they are (1) very efficient or (2) convert form DC to AC and 
back to DC again such that their source voltage is higher.

Sooooooo - you can basically charge for 15 minutes at 4 amps
or 30 minutes at 2 amps.

Actually what you need to do is monitor the voltage and stop the
charge when it drops off by about .02 volts.  (Peak charging).
Strictly going by time you can over charge your battery (and possibly
do some permanent harm) or under charge.  Alto I have found the packs
to be modestly forgiving.  The bottom line is if the pack is getting
hot during a charge - you are hurting it.  It will naturally get real
hot during your flight (putting out about 20 amps for 4 minutes).

If we both throw our junk chargers in the garbage and purchase some
ACE or Astro equipment then we can watch a constant 4 amps flow into
even 7 cell packs.  There are several good notes in this file that
talk about good chargers.

The perfect charger for 4 cells (receiver packs) wasn't the same as the 
perfect charger for 24 cells.  It may be NOW with a fancy new one.

Dan Miner would know!

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

    Jim,
    
    A 900SCR pack will take quite a bit more than 2-2 1/2 amps over
    a half hour charge time. I don't know anything about the Aristo-Craft
    charger, but my TRC Engineering peak detect charger puts out 4 amps
    when run from the car battery, and the 900SCRs like it just fine.
    The R/C car guys routinely charge SCRs at 8 amps.
    Basically it sounds like you're just not putting in enough juice
    over the half hour. Can you lengthen the charge time ?
    
    Terry
    

    Terry,
    
         My aristo-craft charger has an adjustable 0-30 minute timer. 
    When the timer expires it switches to trickle charge.  I can extend
    the charge time by simply twisting the timer knob to whatever
    additional time I desire after the initial half hour charge.  But
    how will I know if I am going to far?  I could sit there and monitor
    it with a voltmeter and stop when I notice a voltage drop, but this
    would be rather tedious.  Also when this charger switches to trickle
    is it safe to leave the battery trickling overnight?  Dop you think
    this charger would work better with a 6 cell battery?  It sounds
    like Kay Fisher is having the same problem, which he thinks is a
    poor charger.
    
    Thanks,
    
    Jim

    As Kay said, monitoring the voltage drop is the best/most efficient
    way, but as you say, the most tedious. Thats why peak detect charges
    were invented, I guess. In your situation I'd try lengthening the
    charge time 5 minutes or so at a time until the battery feels
    noticeably warm at the end of the elapsed time, NOT hot. A good
    peak detect charger will get the battery warm, it won't hurt
    an SCR.
    I really like my TRC Engineering unit, high quality construction,
    computer grade components, DC-AC-DC conversion. Charges up to 10
    cells. It cost $78 two years ago. I can get you the address if you'd
    like. He only sells by mail. Used to have a small ad in MB, haven't
    seen it lately.
    Oh yes, trickle charge won't hurt the battery if the rate is set
    properly.
    
    Terry
    

>    how will I know if I am going to far?  I could sit there and monitor
>    it with a voltmeter and stop when I notice a voltage drop, but this
>    would be rather tedious.

Only one time.  Then record (in your mind how long it took and as long as
you consistently run your battery down completely you can run it for
30 minutes then reset it for another 5 or 10 (what ever you measured
the first time).

>    Also when this charger switches to trickle
>    is it safe to leave the battery trickling overnight?

Yes

>    Do you think
>    this charger would work better with a 6 cell battery?

Yes

But since you have 7 cell pack(s) that won't do you any good.

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

    Interesting comments pertaining to Electric from REC.MODELS.RC off of
    USENET...


    Headers deleted


    
Hi folks. Just a short description of the heli event at our club field
this past weekend. 17 helicopters and 13 pilots in attendance (I was
just a spectator, being a fixed-wing pilot). Usual assortment of 30-60
size birds.
 
A visiting pilot had one of the new Kalt Whisper electric helicopters.
It flew really great, and was quite aerobatic. I had always thought
electrics were klunkers, but this was the hit of the show. All the pilots
I heard comments from were quite impressed. Flight time
was about 4:30, which is pretty good for 8 900mAh cells running an 05
type motor. Unfortunately it was destroyed when the pilot tried to
hover inverted at the top of a loop, and the improperly-secured
antenna fell into the rotor blades and got wrapped up, followed
immediately by a tail-boom strike. Not a pretty sight as the flailing
bird fell about 80 feet.
 
Also, one of our pilots did a great autorotation with his GMP-Legend
(flybarless) when his engine quit suddenly, but unfortunately landed on
uneven ground and tipped over. Not too good for the blades, but it could
have been worse. The helicopter was flying again in a few minutes with 
minor adjustments.
 
The crash of the day, though, was a 60-size machine that went in due to
low receiver batteries. It hit in kind of a side-ways dive at full
throttle, narrowly missing another pilot, and the engine just kept
screaming until they could get to it and shut it off.  Helicopters
often seem to die undignified deaths.
 
Not being a helicopter pilot, it was a refreshing change to just watch
others for a while. Something I might definitely get into in a few
years.
 
Max
 
(P.S. There are two pilots out there who will never again leave their 
      antenna unsecured, or show up at the field with batteries that
      aren't freshly charged.)
-- 
Max Feil                 Usenet: [email protected]  or uunet!bnrgate!bnr-rsc!max
Bell-Northern Research   Internet: [email protected]
P.O Box 3511 Station C,
Ottawa, Ontario, Canada K1Y 4H7.  (613) 763-3093
 

    I wanted to fly an Electric aircraft; all the normal reasons:
    fascinated by the things, kinda handy having little or no noise in the
    UK, 'ease' of use, etc. So,this year I asked santa for some electric
    stuff. From my folks in the US, I got an Astra and an engine; the
    engine is stuck on some boat somewhere in the Atlantic.
    
    What I really wanted was a vintage aircraft, I had asked for Leisure's
    Playboy, but the local model shop must have been out when my folks
    when to get my pressie. This mean't my choice of pressie from santa in
    the UK was easy: a vintage aircraft. After a talk with 'santa' (my
    wife) I chose Black Magic, by Flair. Black Magic is a great looking
    vintage aircraft (sort of like a Cub, but with a deeper cowl chin and
    no underwing braces; also the wing tips are beautifully curved much like a
    Spitfire) and was designed for IC engines, .15 to .29 if memory
    serves me correctly.
    
    Thus, I will have to 'convert' this ship to electric. This should be no
    problem, for the following reasons. The engine 'mount' is a horizontal 
    piece of ply into which I have to cut a slot. Similarly, the cowl
    pieces have to drilled out to accommodate the electric motor. I will
    probably modify the design a little (i.e. make an engine plated to be
    bolted to the aircrafts engine mount, which is actually a structural
    component of the fuselage) so that I can swap out engines.
    
    As you can see from the above, the Black Magic is a sticks and cover
    job, and the manufacturers have tried to remain faithful, even in the
    method of construction, to the original 1946 design. This means that
    this is not an easy kit to build and the, sometimes, unclear
    instructions aren't much help. However, I am having a thouroughly
    enjoyable time building the thing.
    
    So far I have constructed the wing, tailplane and fin. The rather
    complex fuselage is next. I have yet to select a motor (hoping the post
    office will deliver my late christmas package anyday now), but will
    probably go for a geared 540 or 550, as I am not that much of an
    enthusiast as to break the bank for a motor.
    
    Apart from liking some vintage aircraft, there are two major reasons
    why I went this route.
    
    First, from what I can gather, most electric kits (well, only the ones
    I have looked at and read about) seem to be tight on space for radio
    and batteries and the like. I have no such problems with the black
    magic. Although its only got a 60" span, its got tons of room in the
    fuselage. In fact, I think I can put the electric motor cells right in
    the nose of the aircraft i.e. in the cowl, thereby minimising crash
    damage, the cowl has a large intake through which the cells can pass.
    
    Second reason, is the shere stability of the aircraft. In fact, the guy
    in the shop said 'for most pilots, the Black magic flies best when they
    leave the sticks alone'. So, slow graceful flying speed, bags of
    stability, all great for me.
    
    I would appreciate advice from anyone who has done a similar conversion
    or who could give pointers to motor gearing and props.
    
    I'll keep you posted on developments when time permits; this here job
    sure has gotton busy lately.
    
    Angus 
        

    Angus,
    
    The Black Magic sounds like a pretty airplane, er, aeroplane.
    
    If you use a 550 size motor the Graupner Speed 500 is cost effective
    (~$15 over here) but would need the 3:1 gearbox added which bolts
    right up to the front of the motor. The gearbox alone is ~$12-15,
    and there is a Speed 600 which comes with the gearbox already
    installed. The 500 is a 125 watt motor, the 600 is 104 watts.
    
    On a ship such as the B.M. a geared prop would give better performance
    in keeping with the character of the plane, ie, slower but with
    good climb.
    
    A 60" wing isn't any too large but I assume it has a fairly broad
    chord so with a 7 cell pack (don't even consider a 6 cell)
    all up weight shouldn't be a problem.
    
    If you could come up with a wing area figure and a flying weight
    guesstimate, flying characteristics could be estimated.
    
    If the B.M. was originally designed for glow power there may be
    areas where you can safely lighten the structure. Try to avoid plywood
    unless the design requires it for strength.
    
    Shoot for a wing loading of <15 oz./sq. ft. 
    
    I've seen several Leisure Playboys fly. Not terribly impressive
    but acceptable.
    
    Terry
    

    
       Another thing to think about is the placement of the cells. They
    are usually placed around the C.G. The cells are the heaviest part of
    the plane, and if they are too far away from the c.g. ("in the nose of
    the airplane")', you won't be able to balance the weight. Doesn't sound
    like finding space will be a problem. I would also recommend micro, or
    at least mini servos. Every oz. counts! Unfortunatly, the difference
    between a great flying electric vs a marginal electric is usually
    a matter of the money invested. Paying attention to weight when 
    building also helps.
    
              Total weight should be (roughly) between 35 and 45 oz.
    
                              Seven cell 1200 mah pack  -  14.0 oz
                              Two Futaba Micro servos   -   1.2 oz
                              speed control             -   1.5 oz      
                              motor (550)               -  10.0 oz +/-
                              Reciever                  -   1.5 oz  
                              Reciever nicad (250 mah)  -   2.0 oz    
    
                              Total                       30.2 oz
    
      
           This leaves 5 - 15 oz for the weight of the structure, covering
           wheels, push rods, prop to come it at 35 - 45 ozs.
    
           note: The weight of the reciever nicad can be eliminated
                 if  BEC (Battery eliminator circut) is used
    
                 Using a 900 mah battery pack will save several oz, and
                 result in slightly shorter flights.
    
                 A cobalt engine will also save a few ounces compared to a
                 regular "canned" motor, and will also be more powerful,
                 and last longer.
                        

    Thanks for the feedback guys, much appreciated, keep it coming.
    
    I went back home last night and did some calculations and weighing. This
    is going to be an interesting challange.
    
    The normal all up flying weight of the Black Magic is 4 lb. Suggested  
    engine sizes are .19 to .25 2 stroke, or .30 4 stroke.
    
    I weighed the uncompleted aircraft, last night, to see what I was heading
    for. In addition to all the aircraft bits (balsa, u/c wire, bowden
    cables, etc) I weighed in the radio gear, nicads, very large tube of
    PVA glue, covering material (I only had a very large roll of tracing
    paper), a pair of 8" heavy duty engineer's pliers to simulate the
    electric motor, plus a couple of extra bits for margin.
    
    The entire weight came to 3lbs 14 oz. Coupled with wing area of roughly
    3.2 sq ft, this gives a wing loading of just under 20 oz!! Yipes.
    
    Possible areas where weight can be saved:
    
    Replace S148 Futaba servos with S133 mini servos (or equivalent): 3 oz
    Replace 500 mAh reciever cells with 250 mAh cells               : 2 oz
    Trim tailplan, fin, and wings (as yet unfinished)               : 1 oz
    Surplus scrap balsa/ply when fuselage completed                 : 2 oz
    
    Total so far  8 oz.  This will get me within 6 oz of the desired 3lb
    flying weight, for a wing loading of roughly 17 oz/sq ft. However, I
    can't yet afford the mini servos, so I wont gain any saving there and
    the airframe weight may increase slightly due to heavier covering
    material. Though, if I fit a 900 mAh battery pack (as suggested) I
    might lose 6 oz or so; thus getting me within about 3-4 oz of desired
    weight.
    
    Still, one good piece of news is that I have tracked down my parcel
    from the states. It landed two months ago, but the stupid post office
    delivered it to the wrong address! I will collect it on saturday and I
    am hoping it is a geared Astro 05, or better.
    
    Angus
    PS. The glider I got is the Astro Challanger.

    A rider to my previous note, as you loonies are bound to spot it and
    give a hard time about it.
    
    The tracing paper I refered to in my previous note was to simulate the
    weight of the covering material. I didn't propose to cover the airframe
    with it. Though, when very young (about 10) I did cover the wings of a
    free flight glider with tracing paper, and it flew quite well.
    
    Angus
    Can I ever live his down.

    There was great excitement for number one child of the McDonald
    household, this past saturday. We went and retrieved the missing parcel
    containing all our christmas presents.
    
    I eagerly ripped open christmas wrapping paper to reveal my long
    awaited motor. Total confusion and panic ensued. What had I got? What
    had they sent me? Was it any good for the old Black Magic? Only one way
    out, ask the RC noters.
    
    I would appreciate it if anyone can tell me anything about the
    following motor:
    
    A Reedy competition Stock motor
    
    R.O.A.R. Legal - 1/12 & 1/10 scale. No. 6502
    
    Associated Electrics,
    Team Associated,
    3585 Cadillac,
    Cresta Mesa,
    CA 92626.
                                          
    Angus

    
    
       I hope this won't burst your bubble. From what I know, motors
     specifically designed for cars ( especially the high performance
    motors) don't work well for planes. It has something to do with the 
    number of "turns" of the motor. For instance the Astro cobalt 05 turbo
    has 5 - 7 turns, as apposed to the fight motors which have a higher
    number. The lower the turns, the higher the RPM capability of the
    motor is. 
       I'm not saying it won't work, but you would likely have decreased
    performance. As always, its a matter of matching the power source
    to the application.
    
                                          Hope this helped
    
    
    

    Dan is right.Don't even think about using the Reedy motor in your
    plane. The torque characteristics are all wrong. If you were flying
    a light, low drag, fast design, with direct drive and a low pitch
    prop, you might pull it off.
    
    After seeing your weight specs and wing loading, I'd be inclined
    to say don't use anything smaller than an Astro cobalt 15, or something
    with at least 200 watt output.
    This loony caught the tracing paper bit, but I deduced what you
    were doing with it. Eliminating ply and metal parts is your best
    bet for weight reduction.
    
    Terry
    

    Dan, Terry,
    
    Thanks for the advice, I had a feeling this might be the case. What I
    can't work out is why the thing is so expensive: $28.
    
    I'll nip down to the local hobby shop and see what they've got.
    
    On the actual aircraft itself, I decided to do something about its
    under carriage. The one supplied with the kit consists of two huge
    piece of metal rods; at 1/8" (3 mm) diameter, its difficult to call
    them wires. The weight of these things, without wheels, is some 2 1/2
    ounces (75 g). I figured I could do better and I have.
    
    My design weighs 1/2 oz (15 g). I reckon its just as strong as the wire
    job. Its also prettier as the thing is 'sheeted'. With careful
    selection, or construction, of the wheels, I reckon I can keep the all up
    weight of the undercart to 1 oz (30 g), This compares with the 8 oz of
    the aluminimum frame and rubber wheels of a trainer I have which has a
    similar sized u/c.
    
    Angus

    Angus,

    I haven't commented yet, but I'm pretty "heavy" into electrics, and I
    figure nows as good a time as any to toss in some comments...

    Get yourself some Dave Brown Lite-Flight wheels, they're the lightest
    I've seen, and will stand up better than anything you could probably
    make.

    A key thing to remember about electrics is that they stress the airframe
    a lot less than a gas powered version, primarily becuase they don't
    vibrate nearly as much.  Anyplace on the fuse that there's Ply, except
    the firewall and landing gear mount, the ply can be eliminated.  I often
    drill the p*ss outta the firewall after I mount up the motor, too. It
    lets more air flow through the fuse to cool the battery and speed
    control, and it also takes some additional weight off the plane.

    Also, when you build the model, position the battery so that it will be
    centered directly under the CG.  If you do it that way, you can test
    glide the plane without the extra 12-13 ounces of battery weight (it'll
    make it much more survivable if it turns out there's problems with your
    setup).

    NEVER EVER add weight to trim it out.  Rip it down and move the radio
    gear if you have to, but never add weight.

    I think the rule of thumb I've seen in a number of articles is that, to
    fly well, the airframe should weigh no more than twice the power system.

    If an 05 and battery weigh in at around 16-17 ounces, the airframe
    shouldn't come in heavier than 32-34, and that'll give you an all up
    weight of around 48 ounces.


    Randy

    In the new Hobby Lobby catalog they list a Simprop 2000 motor
    as a poosible replacement for the stock Elektro-Uhu motor.  It
    is over $100, so I would be looking for a substantial performance
    increase.  Can anyone tell me anything about this motor or other
    higher performance options for the UHU.
    
                                                   Thanks,
    
                                                   Jim

    It appears this conference is long since dead, but I will try a 
    reply here just to see if anyone out there shares my interest in 
    electrics.   I just received a plan from MAN for a sport scale
    version of the German RFB FANTRAINER.  It is a pusher design with
    the prop enclosed in a shroud for COX .049 TD.  The wingspan is
    36" with an area of 195 sq. inches.  The projected weight for the
    gas version is 23 oz.  I am thinking about trying to electrify this
    model with Astro 035 on 5 cells.  I am shooting for an all-up weight
    of 35 oz. which corresponds to a 25.8 oz./sq. ft. wing loading.  Does
    this sound reasonable?
    
                                              Regards,
    
    
                                              Jim

    Off the top of my head, that wing loading seems too high to be
    successful. You are probably aware that as a general rule, the power
    pack ( battery, motor, etc) should weigh no more than 50 percent of
    the total planes weight. It sounds like you might be ok there, but
    the small wings will still cause you problems.
       As a reference point, my Electrostreak weighed 39 oz, and had a 
    wing loading of about 17 oz/sq ft. Because electrics tend to be
    marginally powered, the take offs with that wing loading tended to be
    somewhat tricky, although the plane flew great once it had accelerated.
    It could have easily benefited from more wing area, especially during
    launch. My guess is unless you launched the Fantrainer from a hi-start
    or something, you wouldn't be able to get the aceleration needed on
    takeoff to have a successful launch. It would also require a very high
    approach speed to keep the wings generating enough lift during landing.
    
         My advice is to either increase wing area, or abandon the
    conversion idea.
    
                               Just my (rusty) electric opinion,
    
                                                          Dan W.

Re: Jim,

I remember seeing a photograph in MAN showing an electricfied version of the
fan trainer. I believe it was in the "Pilot Projects" section, but am not 
positive. If it wasn't there, it had to be in an article covering the KRC
event from last year. Anyway, I'll look thru some of my back issues tonight
and report back tomorrow. 

-Lamar

    Hey maybe this conference is not dead after all!  Do you guys have
    any idea how the power of the COX .049 TD compares with the ASTRO
    035?  The plan calls for a Cox 6-4 pusher prop cut down to 4 1/4".
    The Astro literature claims the 035 can spin a 6-4 prop at 10,500
    rpm.
    
                                             Regards,
    
                                             Jim

    
    
       My guess is the 35 cobalt would be pretty close to the 049
    powerwise. When the astro series was originally developed, they
    designed the 05 motors to match the power of an 049. Since then there
    have been inprovements ( ie cobalt magnets) that have bumped those
    figures higher. Based on this, I would say the 35 cobalt should be
    close to the 049.
    
                                                   

    Depends on the .049...
    
    My stock TDs turned 17k+ rpms with 6-4s. Competition ones are in the
    mid 20s.
    
    You're going to need the rpms for a fan unit while electrics usually
    shine in high torque applications (geared and/or big props)
    
    This might be an application where a high rpm car type motor is a
    better application. Do they give an rpm range for the fan unit?

    Well I took a long look at the Fantrainer plan last night, and still
    have not totally ruled out giving it a try.  The obvious drawback to
    this design for electric is it has a large fuselage, fan shroud, and
    low wing area which adds up to high wing loading.  It sure would be a
    neat plane if I could get it to work.  Astro recommends an all up
    weight of 20 oz. for their 035 with 6-4 prop.  The gas prototype
    version of this plane was 23 oz., so I guess it does look bleak for
    reasonable electric performance.  The biggest reason I think is the
    relatively low wing area, which brings me to another electric project
    I have been dreaming about- the electrification of the Klingberg, or
    other suitable flying wing.  The inherent low weight of a flying wing
    invites electric power, plus I now have a computer radio that would
    allow me to get the servos out in the wings, freeing up the main
    cavity for the batteries, speed controller, etc.  I would prefer a
    "pusher" arrangement with some type of shroud to streamline the motor
    rather than just having it mounted on a platform, for looks and drag
    reduction.  I think I read somewhere that the Klingberg wing weighs
    around 20 oz. in sailplane form and has 78" wingspan with about 600
    square inches of wing.  Assuming the additional weight of an Astro
    05 electric system would bring the toatal weight up to 40 oz., this
    would result in a wing laoding of about 14.5 oz. per sq. ft.  Comments
    on this project would be appreciated.
    
                                                     Regards,
    
                                                     Jim
    

    Jim,
    
    Your numbers look feasible, but based on what I've seen of several
    Klingberg wings flying locally, unpowered, I'd say this would be
    a real handful to get working properly.
    
    There are better airframes to use, if you what to experiment with
    electric wings.
    Dave ? at Western Plan Service, Torrance, Ca., advertises in RCSD,
    has a bunch of flying wing plans, and several have good reputations
    for electric conversion. Of course you'd have to scratch build,
    but you're not far from doing that with the Klingberg, except that
    the Klingberg is much harder than most scratch build projects.
    
    Terry

    Terry,
    
         Please elaborate on how the unpowered Klingberg wing flies.
    I certainly do not want to take on a project that is doomed to
    fail.
    
                                                   Thanks,
    
                                                   Jim

    The one I've seen fly sucessfully, ie, more than two flights in
    a row without breaking something,
     would dart off in random directions on launch, flies fast with
    rather poor L/D, must be landed fast to prevent random tip stall,
    and in general didn't appear to be an enjoyable experience.
    
    The builder/pilot has 30+ years of experience. He said it was the
    hardest kit he's ever built. He finally scraped the kit jig method
    and devised his own.
    It was a beautiful plane with fine craftsman ship, as are all his
    projects. 
    I think it would be an acceptable slope plane.
    
    The other local Klingberg was built by a scale enthusiast to resemble
    the Northrup N-?, twin pusher.
    
    It had mock-up props, shafts, and a bubble canopy.
    He flew it once, got it down with repairable damage, fixed it, hung
    it up in his shop, where it resides to this day.
    
    Terry

    For no good reason I am intrigued by flying wings and think an electric
    one would be neat.  Does anyone know of a good flying wing kit/plan,
    I know Bob Sealy offered one a couple years ago.  Any observations
    or experience appreciated.  I saw a plan for a scale electric 75"
    Span Northrup flying wing in an old Model Builder.  Not sure I want
    to attempt an electric twin yet, particularly due to the cost.
    
                                              Thanks,
    
                                              Jim

    I too love flying wings.....something simple and elegant about them.
    Last year a friend of mine(Jim, a non-Deccie) built the Klingberg flying 
    wing.  I've seen Jims wing fly and have flown it myself.  It's not in
    the same class as a Chuperosa but does fly very nicely.  The high start
    launch is more of a sling shot launch.  You launch the glider about 10
    degrees above horizontal when you high start it.  Also, because it's a 
    flying wing, you us a "Y" shaped bridle that attaches to two tow hooks.
    If the bridle isn't correct, launches are interesting.
    	Jims Klingberg didn't have any tip stall tendencies.  What did
    happen though is that in a high banked turn, the glider would "slip"
    into the center of the turn.  Jims Klingberg was one of the first kits
    made and Roland Klingberg has made several modifications to the kit
    including optional tip plates to help eliminate yawing on high start
    launches and the sliping in a tight turn.  Jim's model was fairly
    rugged and has survived several groundloops and near vertical landings.
    	A suggesting from Jim is to use Kelvar on the spars and leading
    edge and a computer radio.  The Kit comes with a mechanical mixer but
    room in the model is tight for the mixer.
    
    	I seem to recall to just about a year ago there was a two part
    article in one of the mags, M.A.N. I think, about building an electric
    Klingberg.  There's a picture of the model on the cover.  I believe
    that the electric conversion was a stable but fast flyer using and
    ASTRO 05 w/folding prop and 7-800mah cells.
    
    						regards
    
    						Bob
    
    	
    

    After nearly crashing the Kormoran last Friday due to a broken antenna
    cable right at the connector (you have to use a connector in this plane
    because the antenna has to run in the wing with the short fuse and the
    pusher prop), I finally test flew the Elektro-UHU on Saturday with the
    nwe SPEED 600 FG3 (geared 3:1) and a big carbon prop (thanks again, Ed
    Siegmann!). The current is reduced by 20 percent (16 Amps instead of
    20), and the climb angle is steeper! You can't really hang it onto prop
    because the airfoil needs some speed, but it climbs out very well and
    the flight time seems to be significantly longer without any thermals
    available. I don't have any real time measurements yet, but will keep
    you posted. So far, I am happy since the results were about what I
    hoped them to be. The plane is not good for hot-dogging anymore, but
    the Kormoran is better at that, anyhow. On Saturday, I had a friend
    visiting and started to instruct him a little on the UHU. That worked
    very well.
    
    Getting this motor in was - as I was warned - a hard piece of work.
    Since the shaft is not in line with the motor shaft anymore due to the
    gearbox, and since the fuse is pretty slim up front, I had to put the
    motor about 2 inches back into the fuse and work with an extended
    shaft. This one needed another (ball) bearing in the front spar, and
    the alignment of motor and front bearing is still not great. Once I get
    that really straightened out (pun intended), it might be even better.
    maybe I'll try some more props of the variety I got in the meantime
    just to get some experience of what optimization of an electric means.
    
    I'm happy! Got four planes flyable now when I had none in spring!
    Hoping for a golden fall!
    
    Best regards,
                  Hartmut

    This weekend I had the pleasure of attending my first KRC electric
    funfly( this annual event is held each year in Quakertown, PA.).
    
The display of planes and piloting skills was AWESOME!  I will summarize 
    what I thought were the highlights of the weekend:
    
    1)Keith Shaw - everything he brought to this show was tremendous.  He
    had a scale Spitfire with retracts, a GEEBEE, a 1930's vintage twin
    engine racer, his Hyperon pylon racer, a scale biplane, and of course
    a his famous 4 engine - 10ft. flying wing.  Keith proves that anything
    can be done with today's electric power plants, your imagination and
    building skills are the only limits(not to mention $).
    
    2)Steve Neu - I was hoping to see an F3E style electric so I could get
    some ideas how they are setup.  I happened to notice a fuselage that 
    looked like an F3E type ship, so I went over to look at it.  While I
    was looking at it the owner came over and started up a very friendly
    conversation with me.  When I noticed his name tag, I just about
    fainted.  Here I was talking to one of the top 10 F3E flyers in the
    world, and he was telling me everything about his ship.  Steve is about
    the nicest guy you could ever meet, he explained to me exactly how to
    build an f3E fuselage and walked me through all the nuances of his
    the ship he flew at last years world F3E championships.  The ship was
    made of kevlar and fiberglass, one piece 85" wing, RG12A airfoil, stock
    ASTRO 60 FAI(the only mod he says is that he removes some of the metal
    casing to lighten it up), 27 900mah cells, he makes his own speed
    controller, Becker metal geared servos(1 in each wing, 1 in the tail),
    custom aluminum spinner and his own home made carbon fiber 12 x 6
    folding prop.  When Steve flew this ship every person on the field
    was instantly drawn to it.  For starters, the sound was incredible,
    the ship climbed vertically nearly out of site with a motor run of less
    than 10 seconds(I was counting).  The climbing ability of this ship has
    to be seen to be believed, its L/D is also unbelievable.  You really
    have to see a world class F3E ship fly - words do not do justice to the
    experience.  
    
    3) Klingberg wing powered by Astro 035(pusher config) on 5 cells.  The
    motor was totally within the wing, an extension shaft was used with a
    7x3 graupner folder mounted backwards.  The speed of this model was
    tremendous, nobody could believe it was using a stock cobalt 035.  The
    pilot put on quite a show with loops and rolls.  To any doubters, the
    Klingberg wing DOES fly.
    
    4)  Robbe DO228(?) powered by twin Keller 05 sized motors - Awesome!
    
    5) Tony Fiore's Mustang with retracts.
    
    6) At least half a dozen electric helicopters - all flew well
    
    7) BD5, Ligetti Stratos, 4 engine B17, twin engine Heinkel.
    
    Summary - there really was too much to comment about without spending
    hours at the keyboard.  Everything from magestic, slow flying old
    timers to Steve Neu F3e brute, helicopters, ducted fans, multis, flying
    wings, etc., it was just overwhelming!  If anyone has any specific
    questions about a certain ship, I would be glad to provide additional
    information.  I highly recommend this meet to any model fan, it
    certainly is the best I have been to.  Unlike most of the power meets I
    have been to, where they make spectators sit far away in bleachers, you
    were able to get close and really see the ships at KRC.
    
                                                       Regards,
    
                                                       Jim
    

	I would love to see this F3E ship that specs out in 10 seconds. 
	Sounds more like a rocket to me! So where does he fly it in 
	contests?

    Re: -1
    
    Steve Neu was on this year's US F3E team, he is from California(San
    Diego, I believe).  Unfortunately F3E is almost exclusively done in
    California.  The same 8 guys vie for the 3 spots on the US team every
    year.  These are the names I remember - Jerry Bridgeman, Jason Perrin,
    Steve Neu, Bob Sliff, Felix Vivas, Brian Chan.  F3E planes use
    construction techniques very similar to F3B, but then the cost of the
    motor, batteries, and speed controller must be added(about $600
    additional).  The high cost of unlimited class F3E plus the skills
    required to pilot a ship that cruises effortlessly at 60mph, has
    probably limited the number of people involved.  In the hands of
    skilled pilots these are awesome brutes, capable of much longer flight
    times than one would expect from a ship with a 24 oz.per sq. ft. wing
    loading.  Some additional information about Steve Neu's ship - the
    current draw is 62 amps, and the sealing is so good that low speed
    passes at speed I would estimate at about 100mph resulted in absolutely
    no noise!  The ability of these ships to translate speed into vertical
    maneuvers is really something.  After a dive the ship could be pulled
    up at a steep angle and climb back up with minimun altitiude loss. 
    These ships are certaily very low drag.  The motor-prop combination
    of the US F3E ships is rumored to yield around 10 lbs. of thrust, which
    is less than many ducted fans or glo powered planes.  It is the low
    drag of the ships that let's hem perform so well.  Steve's ship weighs
    5.71 lbs and if the motor/prop can provide 10 lbs. of thrust you truly
    have a rocket on your hands.  As any glo pilot can tell you, in a dive
    there is a point where the drag of the spinning prop actually limits
    the speed that can be attained, the folding prop and sleek profile
    allow F3E planes to achieve tremendous speed in a dive.  They are truly
    an engineering feat.
    
                                                   regards,
    
                                                   Jim

    Another thought inspired by KRC, is how well electric multi-engine
    ships fly.  Although I have not seen that many wet multi's fly, the
    ones I have seen seemed to require an awful lot of messing around to
    get the engines running together reliably.  From what I have read
    losing an engine can cause a lot of problems many times resulting in
    a crash.  The electric twins I saw fly at KRC were simply charged 
    and flown - and all flew very well.  So while electrics may not have
    the power/weight ratio of a wet ship, it appears that the simplicity
    of engine synchronization and reliable operation make electric power
    the best choice for many multi-engine projects.  BTW the performance of
    these electric multis was inspiring!  I wish I had the power plane
    experience to fly one.
    
                                                    Regards,
    
                                                    Jim

I would loved to have gone to the KRC meet Jim. Sounds like you had a good time!
I've always wanted to build an OV-10 Bronco, but have shied away from building
it because of the problems associated with "wet" multi-engine planes. I bought
some plans for a 24" ws rubber version(from Carsten plans) a year ago. I was 
going to try scale up the plans for electric power, but have never gotten around
to doing it. A couple months ago however, I saw an ad for an electric powered 
OV-10A Bronco in the back of RCM( or MAN??)  Don't know which route I'll go
yet, but I'd like to make the Bronco one of my winter projects this year. 

-Lamar  

    re: -1
    
    Lamar,
    
         You may want to review the Jan. 1991 issue of Model Aviation,
    where Don Srull provides plans and a construction primer for a small
    twin electric called the Hi-LINER.  The plane uses twin HI-line
    elf motors, speed control, rudder, elevator, & aileron.  The all up
    weight of the ship is 24 oz. The nice part of this ship is the complete
    power system(motors & batteries) only cost $70. It sounds like this
    power system would be ideal for your Bronco project, Mr. Srull provides
    all the details in the article and the price is right!  Good luck on
    the project.
    
                                                    Regards,
    
                                                    Jim

Thanks for the pointer Jim. I remember reading the article and thinking the same
thing. I'll have to re-read it again tonight. It would make a great "proof of
concept" size for my Bronco project. I'd  *really* love to build a electric
powered scale version someday. For now, I'll start with the smaller size. I'll
keep you posted on my progress(once I start :^}.)

-Lamar

    One thing you should be aware of for multi-engine electrics is that you
    might need a different controller. I'm no expert on electronics, and
    especially not on EMI problems, but I once talked to Mr Danzer (who
    built one of my controllers). He offers a special controller for
    multi-engine use. He said that the two (or more) motors can interfere
    somehow (if in one circuit, be it in line or parallel) and reduce the
    radio range significantly (if not worse...). He builds controllers that
    have two PCBs, the controller part and the power amp. You can connect
    several power amps (one for each motor, mounted close to the motor) to
    a single controller board. Other controller vendors have special
    controllers with additional big capacitors for multi-engine use. Maybe
    some of the electronic/EMI experts here can shed some light on the
    reasoning, I just want you to be aware of this issue and not destroying
    the Bronco you dreamed of for so long due to motor/motor interference.
    
    Best regards,
                   Hartmut

    Not knowing enough about twin engine electric power control systems
    or having the personal experience to ask the right questions, I cannot
    say that the issue Hartmut mentions came up in any conversations I had
    with multi flyers at KRC.  One issue that was brought up by a flyer of
    a twin Heinkel(don't remember his name, but the plane has appeared in
    several magazines, and he is from Canada) happened to mention that he
    would not be flying the Heinkel because one of the Leisure motors had
    died while testing at the motel, the night before.  He mentioned that
    this is a fairly common problem with electric twins, saying that Keith
    Shaw had also experienced the problem especially on his flying wing
    that used 4 Leisure 05 motors.  This fellow thought that the problem
    was not specific to Leisure motors but rather had to do with how multi
    engine electrics draw power.  He got rather vague and admitted to not
    really understanding why this appears to happen with electric multis
    with much greater frequency than single engine aircraft.  I did not
    get a chance to talk with Keith Shaw about it, I have a feeling he
    would know exactly what was happening.  As I mentioned, all the multis
    flew flawlessly at KRC - no engine problems other than above.
    
    Hartmut had entered a note some time ago about the Robbe DO-228.  The
    one I saw fly at KRC was very impressive.  It ROG'D from grass in a
    very short distance and flew with good speed(real good speed!)
    performing rolls and low high speed passes.  The sound of twin Keller
    25's was neat.  I really liked this plane.
    
    
                                                  Regards,
    
                                                  Jim

    After hitting phone wires with my UHU, the Astro 05 FAI direct drive
    shaft appeared to be slightly bent.  I mailed it to Astro Flight
    and received it back 3 weeks later the charges were as follows:
    
    Armature - $45
    2 new bearings - $10
    Labor - $15
    Shipping(2nd day air) - $6
    
    Since the total cost of the repair $45 + $10 + $15 = $70, exceeded 50%
    of the suggested retail price($130), I was charged $65 + $6(shipping)=
    $71.  I like Astro Flights policy of not charging more than 50% of the
    retail cost of the motor for repair.  It sure beats trashing a $100
    motor. 
    
                                                       Regards,
    
                                                       Jim

    As with most retail prices, 50% probably represents their cost to
    distributers/dealers. If they pop a brand new engine into your box and
    ship it back for 50%, they're probably covered.

    Well since this file has really gone "inactive" I will bring up a
    project my father is attempting, to see if we can get some con-
    versation going.  My father has blown up a rubber band powered
    plan of a WWII Meschershmitt(sp?) design to about a 50" wingspan.
    The plane is a twin with push-pull power, and no stab, hence it
    is essentially a flying wing with a fuselage.  He plans to use
    twin 30watt Hi LINE ELF motors on 6 800 MAH cells.  The power
    considerations were drawn from Don Srull's electric twin, presented
    in the Jan. '91 issue of Model Aviation.  As Don states in this
    article, the flying weight must be kept below 25 oz. for this power
    combination to work.  To keep the weight low, the fuselage is being
    built in halves over a foam plug using overlapping, crisscrossed
    1/16" and 1/20" balsa doped with chifon covering.  The resulting
    balsa monocoque halves are then glued together and formers may be
    added where necessary.  This is a labor intensive method, but
    results in a very light, hopefully very strong structure.  The
    wings are built with twist in the tips and the elevons will be
    controlled using a Christy mixer.  I will give updates as this
    project progresses.  With the new lightweight electric power
    systems and micro radio equipment, many rubber kits/plans make
    interesting potential electric projects.
    
                                                     Thanks,
    
                                                     Jim

    What is the best way to connect motor nicad batteries in series?
    I have been attempting to make up a 10 cell pack of 900 mah batteries
    which I purchased loose, with solder tabs.  I was connecting the
    batteries + to - using 3/16" copper solder wick.  When I would test
    run the pack with my Astro 015 FAI, at least one of the tabs on a
    nicad would glow cherry red, melting the plastic covering on the cell
    itself and anything else touching it(like the wires which run to the
    speed controller).  Why is this happening?  Last night I tried
    connecting the cells tab to tab, with no solder wick and put the pack
    on a 100 mah slow charge.  I will try it tonight.  Also is it ok for
    the nicads to touch side to side?
    
                                                               Thanks,
    
                                                                Jim

     Here is my limited experience building nicad packs, hope it helps.
     
    
    1.  I have built a couple of nicad packs. I purchased a roll of braided
      flat wire (silver colored) from the local RC car shop. They said that
      is what they use for making their packs. It works fine, and has never
      heated up, etc. 
      
    2.  Yes, nicads can touch side to side. I have taped several together
      and have not had any problems

    Remove the flemsy solder tabs and try using either Dan's Gold Bars or
    Trinity's silver bars.  Both were designed to handle high currents from
    battery race packs.  The cells should not touch each other unless they
    are insulated.  Touching uninsulated cells=instant short/damaged cells.
    
    Robert

    At the KRC funfly, Larry Sribnick of SR batteries fame, made a strong
    case against soldering directly to the battery case.  He felt that
    this practice could cause the batteries to vent.  I know my motor is
    drawing less than 30 amps because it is not blowing the fuse.  I would
    like to get this figured out because ruining batteries at $5.50 each
    is really getting me down.
    
                                                          Thanks,
    
                                                          Jim

    I have to agree. DO NOT pull off the solder tabs. I have never made a
    good solder joint directly on a cell. It either is a cold joint or over
    heats the cell. Also I have seen small holes, almost to small to see,
    on the weld spots from pulling them off. This is why they put solder
    tabs on. I know when you buy a pack they spend a lot of effort to match
    the cells. Doing the long C/10 charge might help balance it. Can you
    arrange the pack so that it's solder tab to solder tab (no wire). Also
    a call to astro-flight or SR might help.

    Use a file to scratch the surface of the cells before soldering.  I've
    never had a problem, nor anybody else that I've know of, with removing
    the tabs.  Most of the cheaper battery packs come with the welded tabs
    and I have seen a few of the tabs melt during the running of cars with
    modified motors.  I usually buy cells in lots of 100 and match them
    myself on a Turbomatcher and sell off the weaker cells.  Usually tend
    to stay away from cells with tabs as those are usually the least
    productive.  Like everything else, everyone has their own opinion as to
    what works and what doesn't.
    
    Robert

    RE: -1
    
    Last night I ran the pack on my test stand  with the cells connected
    tab to tab.  After about 10 seconds, one of the solder tabs 
    glowed cherry red, melting the top of the battery. I am confident that
    the solder joints are good.  It appears that selected tabs are
    incapable of handling the current that is flowing.  Is it possible that
    the solder tabs are incapable of handling the current?  I have not
    blown the 30 amp fuse, I am using a 9x5 Freudenthaler prop.  Short of
    buying a commercial pack and disecting it to see how the connections
    are made, my last alternative will be to add solder wick connections
    in conjunction with the solder tabs to provide a parallel path and
    hopefully reduce the current across the solder tabs to an acceptable
    level.   Could bad or grossly mismatched cells be somehow contributing
    to this problem?
    
                                                    Thanks,
    
                                                    Jim
     

    re -1
    
    Most of the tabs I've encountered are not capable of handling the
    current most batteries produced.  Most commercial 'stick' packs are
    soldered together using a high heating process.  Some packs do use tabs
    that are welded on and then bent and the cells are pushed together to
    form a pack.  You can usually see the tab between the cells.  I've seen
    too many of those type packs short out after the tab has overheated and
    melted through the cells' insulation.  Improperly matched cells will
    not normally cause this problem unless there is a large gap between the
    voltage/current ratings of the cells or one of the cells is dead or
    acting like a short.  On average, a pack is only as good as it's
    weakest cell.
    
    Robert 

    Last night I soldered directly over the welded solder tab to the
    battery itself.  This appears to have cured my problem.  My setup
    is drawing > 25amps,< 30 amps.  As far as I can see solder tabs
    will not work in high current applications, as stated in the previous
    note it is necessary to solder directly to the battery itself.
    
                                               Regards,
    
                                               Jim

    Good soldering practice applies to soldering batteries as well:
    
    - Use an iron that's powerful enough and has a good wide tip
    
    - Prep the end of the battery
    	- file the smooth surface a little
    		- to remove any coating
    		- to get some teeth on the smooth surface
    		- to get good connectivity to the raw metal
    
    - Pre-tin the end of the battery!
    	(get a small smooth dab of solder on the can before you
    	  try to apply the tab or wire)
    
    The trick to soldering up a battery with out damaging or venting it,
    is going to be like handling any delicate electronic component.
    
    Have the surface prepped and ready to make the solder joint quickly
    so that only enough heat to do the job is applied.
    
    FWIW:
    	Dave.

    To anyone interested in electric twin engine RC aircraft, the latest
    issue of Model Airplane News has an article by Keith Shaw, divulging
    much useful information regarding design, weight, and power
    considerations.  Keith is a real expert, the article is worth
    reading.  After seeing his Dehavilland Comet 88 fly at KRC this year
    I really aspire to building an electric twin someday.  This ship
    had retracts, weighed 7.5 lbs, and was powered by two Keller 25
    motors.  Keith claims full power flights of 6 minutes using Sanyo
    1200 mah batteries and says he has had flights as long as 15 minutes
    at low power.  Keith feels electric is the way to go for twins, his
    planes certainly make a strong case for this.  BTW he says the Comet
    has over 300 flights since 1985- proof of the incredible reliablity
    of electric twins.
    
                                                        Regards,
    
                                                        Jim

I've read the article Jim mentioned in the last reply and it's excellent! I've
started doing my homework for my OV-10A Bronco project. While reading the 
article, I never saw anything mentioned about prop rotation(both props spinning
in the same directions vs each prop spinning in the opposite direction.) I am
leaning towards the props spinning in opposite direction to counteract the
torque. Any thoughts on this?

-Lamar

    
       Lamar,
    
          If possible, It is advantagous to have counter rotating props on
    a twin. With an electric is is fairly easy, as you just have to wire
    one engine in reverse. One thing to take into accouunt it that you
    would want to "break in" the motor in the reverse direction to minimize
    brush wear, increase effectiveness, etc.
       
         The advantages of counter rotating is that the torque, and P
    factor are cancelled out making it easier to taxi, climb out etc. The
    other big advantage is that in case of an engine loss during flight. By
    having both props turn into the middle, it takes away the factor of
    having a "critical" engine ( not to lose ) on a twin with both props
    going in the same direction.
    
         The irony is that with electrics, it is much easier to set up
    counter rotating props, but they also seldom have a single engine 
    failure, so the "insurance" advantage of counter rotating props is
    seldom, if ever needed. They do still offer the other advantages with
    Torque and P-factor though. 

    
    
         One other factor to consider with counter rotating engines is
    that you are more limited in your prop options, since one engine needs
    a pusher prop. Master screw-up, and Zinger are 2 sources, but you are
    limited to a few sizes.
    
                                                            DW2

Funny you should mention that, Kay said the same thing while we were flying
at Acton today. I'll have to check what pusher props are available for an 05
sized engine. 

I want to get the plane sketched out next week (since I'll be on vaction) and 
order the wood for it. I'll be using a plan for a 30" wing span rubber powered 
Bronco as a reference. I'll probably go with a Clark Y airfoil(recomended in the
MAN article) that has a 10" cord and 60" wingspan. If I can keep the weight to 
under 5 lbs, I'll end up with a wing loading around 18 ozs/sq foot.

-Lamar

p.s. - HAPPY HOLIDAYS EVERYONE!!!!  

    In Keith Shaw's article in MAN he does address the issue of counter
    rotating props towards the end of the article.  He states that he has
    used both counter and non-counter rotating props and did not see any
    significant advantage to counter rotating props, indeed he states that
    he no longer bothers.  Don Srull drew the same conclusion in his
    article on his electric twin in the Jan. 1991 MA magazine.  
    
    Like LLamar I have been intrigued by Keith's article and have been
    running his formulas by a number of plans/kits.  My problem is I
    have no power plane experience(ie ROG!), so I know I should build a
    docile trainer like the Amptique with landing gear and work on
    perfecting my power plane skills.  But I really aspire to building
    an electric twin.  Shaw's construction and design methods are amazing.
    His DH Comet 88 with 900 square inches of wing, retracts, twin Keller
    25/12 motors and 24 1200 mah Sanyo's weighs only 7.5 lbs, which
    translates to a wing loading of only 19.2 oz./sq. ft.  Anyone who
    has seen this plane fly will tell you its no dog!  I think part of the
    reason I am interested in electric power planes, is it has all been
    done with wet power- ducted fans, helicopters, multis, WWII, etc.
    If you show up at the field with a scale type electric, it is really
    something different.  I am convinced that electric is the way to go
    for twins and with the proper building techniques provides all the
    excitement of gas power.  I know some people feel that the lack of
    noise takes something away from the experience, but I have never felt
    that there is anything "scale" sounding about a 2 cycle glow engine.
    Electric twins sound neat and are much easier to fly if built properly
    than their gas engine equivalents.  Keith Shaw's planes prove that it
    can be done electrically, provide one has the building and flying
    skills.  
    
                                                        Regards,
    
                                                        Jim
                                                      

    
    
      Lamar / Jim,
    
         Go for it, I can't wait to see an electric twin fly ( in person )
    
                                                           Dan 
    
                                   

RE .451 Jim,

Try a Goldberg Mirage 550 instead. George Mills and I have been flying ours
in Acton and they've been excellent perfromers. George has flown his off floats
and snow skis(at lunch today.) The Mirage will ROG in about 30'(using 2 3/4"
tires) from the soccer field we fly at. I have a direct drive astro 05 cobalt
in mine and George has a geared 05 cobalt in his.  I think it'd be a great
choice for you.

I agree that with your comment about the lack of noise. Since when does the
the sound of high pitched screaming two stroke remind you of the rumble of a 
Merlin! Don't get me wrong, I do like to fly wet powered planes as well. Heck,
I love flying any RC plane no matter how it's powered(or not!) 

-Lamar  

I workin on it! :^) I can't wait for a certain wet powered twin to fly!! Wish
you were going to be here next week. I hope to head up to Gardner a few times
while I'm home next week. Don't freeze your as* off up in Minnesota next week!
Keep those fingers warm too! You'll need 'um for the maiden flight of the
Grem-Twin!!!!

-Lamar

    Ordered a 5-cell 1200mah battery pack for my father for a Christmas 
    gift from Hobby Lobby.   The battery pack that came was built from
    1400 mah Sanyo SCR cells.  The invoice had the correct part number,
    and the catalog shows no packs made from 1400mah cells.  Maybe the
    1200 mah cells are discontinued and the 1400 mah cells are being sub-
    stituted?  Sure hope they don,t discontinue the 900 mah SCRs.
    
                                                 Regards,
    
                                                  Jim

    
    A lot of cells (even sanyo cells) are binned. I ordered 900mah and got
    1000mah (binned by sanyo). You really have to specify cell size exactly
    and ask what mah they have or you want. For example if you ask for 1000
    you may get a good (old 900) or a bad (old 1200). If your lucky you
    have the weight of old 1200 binned to 1400. We better get used to
    calling them C,SUBC etc. buy I myself don't know the names of the cell
    cases either.
    

    Sanyo has stopped making 1200 SCRs.  The standard Sanyo SCR is now
    1400, so Hobby Lobby is probably using the new cells without changing
    the part number.
    
    The 1400 SCR does not totally dominate the old 1200 SCR for those of
    us who race cars:  1400s have higher internal resistance and don't
    tolerate abuse as well (no more charging at 9 amps!)  This means that
    stock racers, who need high voltage, are snapping up the last of the
    1200s.
    
        --mark
    

    re -1
    
    Thanks for the info on the batteries.  I weighed the 5 cell 1400 mah
    pack I gave my father on his postal scale and it came out at 10 oz.
    The 5 cell 1200 pack was advertised at 9.6 oz. I believe.  This pack
    will be used with a geared Astro 035 swinging a 10-6 prop to power
    a Guillow Aeronca.  At the estimated 10 amp current draw, 10 minute
    flights should be routine with speed controller.
    
                                                          Regards,
    
                                                          Jim

    Sorry if this has been discussed and al pointers welcome. Has anyone
    seen the electric RC planes in the toy stores that come ready to fly, I
    think they are called "Ready To Fly" as a matter of fact. There are
    four different models all about $129.00. 
    
    Is this a good way to get introduced to the RC hobby, ie learn to problems
    and challenges without too much invested? I'm sort of thinking that my
    seven yearold and  myself could try it together. We need a hobby and an
    adventure. I used to fly line control as a kid.
    
    Dave.

    Dave,
    
        I don't know the particular model you are referring to, but
    my guess is it probably would not fly well, if at all.  Models
    costing twice this much(KYOSHO) have a reputation for not flying.
    Typically they are overweight and underpowered.  Models designed
    to fly with electric power must be carefully designed and built.
    Most of the ready-to-fly variety do not meet this criteria.I would
    not recommend purchasing it.
    
                                                 Regards,
    
                                                 Jim 

    One of the guards here asked me the same question yesterday. I said
    about the same thing with the additional comment that the All Wood
    Almost Ready to Fly (AWARF) stuff is looking pretty good. This
    generally gives you a more repairable plane with a better initial
    weight. I'm not aware of any electric AWARFs currently and agree that
    the foam ones are a challenge for even an experienced instructor/pilot
    to fly. Building a simple kit together is the best way to go and gives
    you some quality time together.

    
    I suspect what he saw is the COX series that include the 2 channel
    radios. Or the KYOSHO series without radios. Both are junk.
    I learned with electric and some help by an experienced pilot.
    Buy a good 4 channel FM "1991 approved" radio (New $109-$139 Used
    $50-$80). You could start with a glider. In fact the spirit is an
    excellent glider. And when your ready for electric you can switch
    over to electric (SPECTRA) which is a spirit with a motor. The Spirits
    only cost around 34.00. To fly a decent electric you really need to
    spend around $400.00
    
    Good flying Electric 
    
    Good motor (ASTRO FLIGHT 05) $80.00
    2 light weight servos $60.00
    1 plane $50 (SPECTRA or TRAINER)
    1 good battery pack $40.00
    1 charger $50.00-$150.00
    1 motor control $30-$150.00

    Saturday I ordered an Easybuilt Hurricane kit from CS Supply.  The 
    kit is supposed to be designed for electric power:
    
    50" wingspan
    404 sq.in. wing area
    05-15 geared astro motor recommended
    Kit cost - $44 + $5 shipping
    
    The model is a "sport scale" version of the WWII fighter.  The
    construction is similar to rubber powered planes(bulkheads and
    stringers).  Charlie Sylvia of CS claims these kits are optimized
    for electric power and will ROG.  I am considering building mine
    without landing gear and probably would use a folding prop(something
    about landing gear hanging down on a WWII ship that doesn't look
    right).  Not knowing what the weight of airframe will be, I am not
    sure what the final weight and power system will be.  For Maximum
    flexibilty I will probably buy a geared, 015 then I can use 7-12
    cells.  I will run Keith Shaw's formulas when I get an idea of what
    the airframe will weigh, then I will decide on # of cells, prop size,
    etc.  The outside limit of this ship I figure would be about 60 oz.
    which yields a wingloading of 21.4 oz/sq ft.(better have nice greased
    in landings at this weight!).  I will provide a kit review when it
    comes.
    
                                                       Regards,
    
                                                       Jim  

    The Easybuilt Hurricane arrived last night and I am pleased with the
    kit. The instructions are not very good, however, so some previous
    building experience is necessary.  The instructions specify a flying
    weight of 40 oz. and a max wing loading of 16 oz./sq.ft. which = an
    all up weight of 45 oz.  I will shoot for the following configuration:
    
    Geared Astro 015 - 9.0 oz.     Proposed airframe weight - 15 oz.
    10 900 mah SCR -  16.0         Wing loading @48 0z. - 17.1 oz/sq ft.
    250 mah rx bat -   2.5         Full power run @20 amps - 2.7 minutes
    4 channel recvr -  1.0         Watts/lb. = 66.7
    Jomar SM-4      -  1.5
    3 servos        -  3.0
                     ---------
   total              33.0 oz
    
    
   The cell count and prop can be adjusted to get the best possible
    combination of weight, performance and run time.  For instance if
    I drop to 8 cells and prop for 18 amps, the wingloading would be
    16 oz/sq ft, with 51.2 watts/lb and a full power run time of 3 minutes.
    
    I am really looking forward to this project.
    
                                                  Regards,
    
                                                  Jim   

RE .464 Jim,

What other warbird kits does CS Supply offer? What better way to "dust off"
some of the fellow A.S.S. flyers down in Acton. Better watch your "6" guys! :^)

-Lamar

    Re. -1 
    
    The other "warbird" kits offered by Easybuilt through CS supply
    that I remember(don't have the catalog here) are a Spitfire
    and a PBY-Catalina for twin 035's.  The SPitfire is listed as
    having 288 sq. in. wing area, so this would definitely be an
    05 powered ship.  The Hurricane with 404 sq. inches allows
    for more flexibilty in building.  Remember the servos, rx battery,
    speed control, and receiver are fixed weight items which really
    do not vary between 05 powered planes and 40 powered planes.  When
    you have learned and perfected the light and strong building
    techniques(which any free flighter knows) you can electrify any
    warbird by obtaining a 3-view diagram and applying "electric"
    building techniques.  The ease and benefits of using electric power
    for twins has already been discussed.
    
    The Easybuilt kits are reasonably priced(<$50) and will provide a
    primer on building light.  Having attended KRC funfly this year,
    I asure you electric warbirds do fly-some spectacularly.  
    
                                                    Regards,
    
                                                    Jim 

I'm building a spectra (motorized spirit) with a geared astro 05.
I've been mainly flying gliders the past couple of years and this
is my first 'electric' glider.

My question is... How do I mount the geared Astro ?  There is plenty
of room for it to fit but I am unsure of how to mount it securely.

The instructions say that on a non-geared version there are two 
screw to mount through the block to the engine.  But unfortunately
in the geared version, these two screws are used to hold the
'gear plate' and the instructions state not to use these for mounting
purposes.

Any suggestions or ideas ?

Todd
    

    An automotive hose clamp, the metal kind with the screw adjustment,
    is about the simplest way to mount a motor.
    
    The bottom of the clamp can be screwed to a spruce block, and the block
    epoxied to the bottom of the fuselage. Position the adjustment screw
    so that it can be accessed with a screw driver.
    
    I'm using that method with my Astro 05 direct drive in the Weston
    570.
     Take the motor with you to the hardware store and buy the smallest
    size that fits over the motor case and still allows tightening
    down a few threads past the screw.
    
    Down/side thrust can be adjusted by placing shims between the clamp and
    motor.
    
    Terry

    Terry,
    
    That's a great idea!  Thanks for the suggestion.  Having never built
    an 'electric' before I never came across this problem.
    
    The hose clamp will also allow the engine to stay cool.
    
    Thanks again... Todd

    Ok but tie-wraps and shims are much lighter. Remember 1/2 oz or so is a
    measurable proportion of the overall power/weight ratio.
    
    Buon Volante!
    
    Ciao, Ed

    
    
    I agree, the tie-wraps work great I use them all the time. Put one
    on each end about 3/8 in from the end. Holds the motor without a hitch.
    I used this method on my Mirage before I put a .15 in it. oops, I
    almost forgot this is the electric note.....
    
    
    Bruce

    I had a terrible time with this on my spectra. When I put the geared 05
    everything went out of balance. I'm using 7 900mah (bined 1000mah) and
    s133 servos. To balance it without adding weight to the tail. I had to
    have the gear box face about a 1/2 back from the front of the plane.
    And the batteries are so far back that they hit the servos which are
    also mounted as far back as I can. I also mounted the rx and
    powerswitch above the battery pack to get the weight rearward. Mounting
    the rx and power switch out of the "crash path" of the batteries is a
    good idea also (very tight sqeeze).
    
    To mount the motor I thickened the wall of the nose of the plane about
    a 1/2 inch. Then I removed the bolts that hold the gearbox on and
    replaced them with studs. Then used threaded "stand-offs" (thick nuts)
    to hold the gear box on. Then drilled holes the diam. of the standoff
    in the new think wall nose. The standoff sits inside the wall. Then you
    screw the gearbox from the front into the standoff similar to
    directdrive.
    
    All-in-all it looks good, it's easy to remove motor and I did not have
    to add wieght on tail to balance. The thing I don't like about it is
    that it is tricky to get the cells in and out. I had to cut most of the
    former between under cockpit and underwing) out. Also the thick wall
    tends to crompress and thereby loosen the screws. But it flys
    wonderfull.
    

    After building the center panel of the Hurricane wing, I have decided
    to rebuild it using Blue foam covered with 3 oz. glass on the bottom
    and 1.5 oz glass on the top.  Since I will not be using landing gear
    on this ship, I didn't think the built up center section would hold
    up.  Hopefully the weight will not be excessive.  This first iteration
    is going to be a learning experience on how much things weigh.
    
                                                      Regards,
    
                                                      Jim

    	I would like any comments, good or bad about the use of a Master
    Airscrew, geared 05, as a replacement for the OEM "05 Goldfire" motor in
    an Electra.   Actually its a liitle late to be asking this cuz, Ive
    already bought the engine and I'm now figuring out how to mount it!!
    
    	My thoughts were that this geared motor w/ its large folding prop
    will get the Electra altitude a lot faster than the anemic "Goldfire"'
    I must admit that my 1st choice was an Astro geared 05, but the
    scotsman in me took over, since I bought the new motor at $39, I now
    see them in Tower for $25, seems I cant win!!
    

    re: -1
    
    I think gearing is the way to go for ships like the Electra.  The
    direct drive motors don't seem to work too well with relatively
    high drag airplanes.  Astro motors are high quality and probably
    worth the investment after your flying skills are established.
    Being able to buy four geared "can" motors for the price of a
    single ASTRO is an issue.  
    
                                                      Regards,
    
                                                      Jim

Electric glider - CG question...

I've got the motor mounted wedging it inbetween three blocks of hard-wood
with a tie-wrap threaded through each block.  This setup works great..
thanks for the suggestions...(.470)

Next question.... Since I am using the Astro-cobalt geared motor I
am very nose heavy.  To get the center-of-G per plan I have to put
the 7-cell battery rear-ward in the fuse.   The plans show to put the
battery directly under wing but with the nose being so heavy I have
to put the battery starting at the Trailing edge of the wing leading
back toward the tail

Usually my planes come out tail heavy so I have never put that much
weight behind the TE of a wing.  

So for the question.... Is there any problems with putting so much
weight behind the TE of a wing to get the CG per plan????
    

    That does sound kind of extreme. Was this electric originally designed
    as a straight glider, no power? Most of the electrics have shortened
    noses to compensate for the heavy motor up front. 
    
    But, if that's what you have to do to get the CG right, I guess you do
    it. Unless you want to go through the exercise of shortening the nose
    moment. Doesn't sound like fun. One caution: The former under the wing
    trailing edge might have to be beefed up to withstand the "battering
    ram" effect of the battery pack in abrupt, nose in landings. 
    
    Dave
    

    This is a spectra that is designed as a 'electric' but for a non-geared
    motor which I assume is lighter.  I assume the geared portion of the
    motor adds extra weight to make it alot more nose heavy.  Also the
    cobalt motor is heavier than the 'gold-fire' more that came with 
    the kit.
    
    I don't have any problems with wire length from the
    battery-switch-to-engine but it does seem extrem that the battery
    has to be placed so far back to get the CG right.

    This is exactly what I told you would happen in .472 In order to help
    the problem I mounted the motor (face of gear an inch behind front of
    nose), radio (above battery on shelf), BEC (above battery on shelf) as
    far back as I could so I could bring the battery forward. The battery
    is touching the two s133 servos (which are also mounted as far back as
    possible). I go to the field with 4 charged packs. I don't charge while
    in the plane. So swapping packs was an issue with me and I can swap
    packs fairly easy (still through the canopy). It does fly great though.

    Nose heaviness is a common problem with sailplane designs converted to
    eletric (which the Spectra is).
    
    The first time this happened to me (with a Graupner ASW-22 kit)
    the best solution was to convert the battery pack into an in-line
    shape, all seven cells lined up end to end. This threw enough weight
    to the rear so that it wasn't necessary to change the motor or
    radio positions.
    
    Terry

    The battery pack is an in-line shape with all seven cells lined up
    end to end.
    
    Actually having the battery pack towards the tail of the plane makes
    it easier to install and remove.  The only concern is... will it fly?
    
    Having that much weight behind the TE of the wing to balance to plane
    concerns me.  I have never put that much weight behind a trailing
    edge of a wing before (but of course this is my first electric too).
    
    So... will it fly?? or do I need to reposition the battery directly
    under the wing and move the engine rearward??
    
    Todd

    As long as the plane is balanced correctly, at the point specified
    on the plans, then it will fly. It makes no difference where the
    weight is located, as long as structural strength is adequate to
    support it, as Dave W. pointed out in an earlier note.
    
    In your case, having the battery at or partially behind the t.e.
    means that some greater than normal load will be placed on the fuselage
    floor and on the whole fuselage structure in the t.e. area,
    particularly in the event of a hard landing/sudden deceleration/etc.
    
    You may want to reinforce the fuselage sides along the t.e. area.
    I'm not familiar with the Spectra construction, in detail, but I'd
    guess that the fuselage is plenty strong enough to withstand any
    normal flight loads caused by battery weight near the t.e.
    
    Terry

    Having the cells all side by side would bring more weight forward in
    the spectra. This is because the fuse IS designed for a wide battery
    pack (6 cell 1500mah). And my short and wide battery pack is already as
    back as far as it can go (hits servos). Making it narrow and long would
    bring some cells closer to the nose.
    
    As .-* has said CG is CG. It does not matter were the weight is as long
    as it balances is regards to being able to fly. What you should be
    concerned about is how the structure of the tail can handle the weight
    on a bumpy landing. The real battery area is beefed up with plywood
    for this reason.
    
    Are you still in front of the servos? Or are you talking about
    way back (behind servos).

`"CG is CG" it doesn't matter where the weight is located'...

That's what I was looking for!

re: 482... Yes the battery is located behind (well behind) the servos but it 
doesn't interfer with their operation.  In fact, it makes it easier to
install/remove the batteries because there is more room and you don't
have to remove anything else to get the batteries out (and worry about
the rats-nest of wires which are in front of the servos)

I'm using the micro servos with a small receiver battery & electronic
on/off switch. The rx battery, rx,  and controller are all positioned just in
front of the servos.

.481... What was I thinking re: the batteries being end-to-end.  Actually
they are positioned side by side seven cells long (i.e. one row of 7 cells side
by side, e.g.  [] [] [] [] [] [] []   )

The fuse should be able to handle the weight being farther back.  I will add
some extra reinforcements to the bottom and sides of the fuse behind the
wing where the batteries are located (not an easy job since the fuse
is already built and I do not want to cut it apart....)

Thanks for the help... it is GREATLY appreciated
    
    
    
Todd


    

    Well my father finished his first electric power plane style ship.
    It was built from a design we saw at KRC - 450 sq. in. high wing,
    rudder/elevator/speed control, powered by a geared Astro 35 and 5
    1400mah Sanyos.  The static runtime of this setup with a 10x5 REV-UP
    prop at settings vary between half and full throttle was 10 minutes.
    The all up weight is 42 oz.  I will report how it flies if we ever
    lose the snow here(got 22" last week).
    
                                                      Regards,
    
                                                      Jim

About those master airscrew gear reduction units.
I landed the cub today and the prop touched the ground and the 
cowl fell off.

Hmmmmmmm - I said from about 20 feet away - how could that be?

The gear reduction unit had broken in half and it and the prop and
the cowl all left the front of the plane in one chunk.

Now I'm going to order an Astro gear reduction unit.

P.S.  The prop did not break!

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

	Has Anyone used the new Sanyo KR-1200-AE cells ? 
	I would think that they would be much lighter than the SC cells

					Larry

	When I destroy the nose of my electrics I use a standard
fiberglass glow moter mount bolted to the NEW firewall. I hold the 
electric motor to it with elastic bands so if the prop hit the ground
the elastics give way not the motor shaft.

				Larry

    Re: -2
    
    I am not familiar with Sanyo KR cells.  The lighter Sanyo 1700 SCE
    cells have higher internal resistance than the SCR cells.  They
    heat up much quicker and do not work well with current draw over
    10 amps. They must also be charged at a much lower amperage.
    
    
                                                        Regards,
    
                                                        Jim

    Although activity in this note is basically dead, I will editorialize
    to see if some interest can be "stirred up".
    
    I think one of the biggest reasons electric flight has not really
    caught on in this country is the manner in which it has been applied.
    I have drawn this conclusion based on my experiences with my Robbe
    ARCUS this summer.  I have become much more active this year -
    attending funflys, joining a power club, etc.  I am a mediocre
    flyer and the ARCUS is basically a relatively inexpensive, ARFish,
    medium performance electric glider.
    
    Just showing up with this plane, I now feel like a celebrity!  People
    who have seen it fly are telling other people at the field to "watch
    this one" and "are you going to fly the rocket".  It is really quite
    embarassing because I know what a really high performance electric
    in the hands of a competent flyer is capable of.  The Arcus piloted by
    me certainly is not the pinnacle of electric flight, hence I am uncom-
    fortable with the attention.
    
    Anyway my point is most people have not seen a well designed electric
    fly(in the USA anyway).  The electric columns in the popular magzines
    (especially RCM, MA, and FM) are particularly boring and in my opinion
    actually discourage interest in electric flight.  Case in point - I am
    so sick of reading about wet trainers(ie Sig Seniorita's etc) and other
    "sport"(4 STAR 40's, etc) being converted to electric in Bob Kopski's
    column in Model AViation magazine.  Taking a big, high drag, wet design
    and installing an electric system(higher weight, less power than glow
    engines) only confirms the view that electrics are "dogs".
    
    The USA manufacturers only compound the problem by offering "wet"
    designs in electric versions, powered by cheap direct drive can
    motors(PT 20 electric, Electric Cub, etc.)  The Japnese(ie Kyosho)
    are worse!  
    
    I can see no good reason to power a draggy "wet" design with an electric
    motor unless noise is really an issue or you just want to do it because
    you like electrics.  It's performance will inevitably be less than the
    glow version.
    
    Electrics really show their stuff in low drag designs where the ability
    to use folding props, on/off controllers in conjunction with
    powerful motors results in high performance electric sport
    planes/gliders.  Electric motors are preferable for multi engine
    designs where their inherent reliabilty and sychronization "tame
    the multi-engine tiger".  Electric power with folding prop and 
    speed control also allows WWII ships to be handlaunched and flown
    w/o landing gear.  
    
    Until the American manufacturers and writers stop trying to use
    electric in the wrong places, people will continue to be amazed
    be ships like the ARCUS which represent an appropriate airframe
    for electric power.
    
    COMMENTS ???
    
                                                    Regards,
    
                                                    Jim
                                                   

Keep going to the field and it will improve. I'm in basically the same boat 
with my Alcyone. I'm a glider pilot in a power club. They start power later
on sunday so I head out early and have the field to myself. It's gotten to 
the point where a lot of power guy come out and get set up early and watch.
Now I'm starting to get some of the power guys out there with gliders that
have been in closets and we probably have 6-8 people that admit to flying 
gliders too 8^)

If you show that it's possible and are willing to give help, it will catch on
slowly. Especially with the types of comments your hearing.

    Jim B.,
    
    I'll do my very best to support you! My box with the electric FIESTA,
    RACE CAT and Kormoran was picked up today to be shipped (flown, really)
    to Shrewsbury. Although I consider myself to be a medium flyer (just
    don't spend enough time to become expert) and it happens that I'm not
    at the field for weeks, I assume to get some attention with the planes
    I'm bringing. I only hope they survive the trip...
    
    In Germany, things might be a little different, but not completely.
    There is a bunch of electric flyersthat frequently meet for funflys and
    show and tell. The magazines report amazing things (latest Aufwind has
    a standoff scale Gee Bee, powered by a geared SPEED 400 and 8 cells!),
    but you don't see much of that on the average flying field. But it is
    coming, slowly, but steadily. Just keep your fun, and people will get
    attracted by the ease of electric flight (no more fiddling the engine),
    low noise and last, not least and improving: performance. Pattern ships
    are being experimented with more and more here! They need 30 cells, but
    they can do the complete F3A program.
    
    Think about getting together despite the distance between Rochester and
    Shrewsbury. I'll bring all my Aufwind mags (a magazine that specializes
    in gliders, electrics and experimentals) and some more. 
    
    Best regards,
                  Hartmut
    
    P.S.: I don't have info on the prop for the 70/4 and the New Match yet,
    but will get it within this week. New Match is on hold, first samples
    built from kits without glass reinforcing were torn apart in the air.
    That's not what GRAUPNER will deliver. I'll keep you posted.

    Jim,

    It's funny you should "stir up the electrons" again...

    I think I beat Jim Cavanaugh's record with his "Virgin Cadet".  I
    finished my third ElectroStreak in September of 1990 and it flew for
    the first time yesterday!  When I finished it, all I had was 2 AM
    radios and I was still flinching from loosing 'streak #2 due to
    radio interference caused by brush noise.  Now I have 2 FM radios
    and didn't have a problem w/ the radio.

    In between then and now, I have also done a lot of glow-glop flying
    and have gotten used to the power to weight and duration benefits of
    glow powered engines.  My main plane right now is a Great Planes Big
    Stik 20 (for .20 to .25 engines) but is powered with a Magnum PRO
    .45 ABC w/ ball bearings.  When the engine is running "just right"
    (not very often) it will go vertical as far as you want.  Even with
    the engine a little rich, it will climb at an 80 degree angle.  It
    will do this for over 8 minutes.  (almost 10 minutes)

    My ElectroStreak is powered with an Astro Flight cobalt 15 on ten
    900 mAh Sanyo SCR cells and weighs 46 ounces.  Note that the
    ElectroStreak is considered an "05" size airplane.  The performance
    is pretty good but only lasts 2 minutes and definately isn't up to
    vertical performance.   
    Some disclaimers: I think the motor needs new brushes and should be
    re-timed.  Thus, the motor may not be performing up to its
    capabilities.  I will send it to Astro Flight for a rebuild this
    fall if not sooner.  I was also using an 8x5 prop instead of the
    recommended 7x6.  I will experiment with other props.

    Summary: If I want to be happy flying electrics, I have to:

     A) fly motor gliders.  (I bought a finished Spectra from
        George Mills, but I haven't installed motor and radio yet.)

     B) buy an Astro Flight 15 FAI and one of the "poor man's F3E" type
        planes for aerobatic flight.  Maybe one of the Weston Aerodesign
        "Electro Booger" or 10 cell glider kits is just the thing. 
        However, I'm still afraid the duration will be dissapointing...

    So, have I given up on electrics?  No, but I think it's time for me
    to go to the Penn. KRC meet in September again and see what's
    available now.  If there is an electric capable of near vertical
    performance for 5 minutes or more, I'm interested.  Otherwise, just
    give me a glider with a built-in winch (electric motor).

    Hartmut and Bernd: Will you still be here on September 19 & 20?
    Maybe we could plan a trip to the KRC meet?

                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |            Happy Landings!
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|              - Dan Miner
     |_/      |___________|  |_________|  |
                      |       /           |     " The Earth needs more OZONE,
                      |      /                       not Castor Oil!! "    
                      |_____/

RE .489

	I purchased 7 KR-1200-AE's they are the size of AA size batteries maybe a touch
larger I wired them into a flat pak in series and with the wire and connectors the pak
weighed in at just slightly less than half the weight of an SCR 7 pack. I flew it
in my PT electric and it worked wonderful.  I am thinking of buying a second pak and wire
it in parrellel with the first. This should double my flight time with only a slight
increase in weight.



RE .490

	You are right the magazines don't give us enough press. Event at the NATS there
were virtualy no Electric events. But, I don't let that stop me, I enjoy the challenge
of preparing a plane to fly electric and then I experiment to try and make it run better.
 
	I recently crashed MY PTE and bent the motor shaft so I purchased a ROAR 24
car motor. This worked pretty good except that the Futaba receiver/speed control that
I used would shut down due to over heating. I remidied this by adding two spoon halves
mounted as airscoops and ran straws from the scoops to the speed control portion of the 
receiver.   This worked very well.

						Larry

    Re: Last 2 replies
    
    Thanks for the words of encouragement guys!  I really am not looking
    to "convert" people to electric flight.  I am a firm believer in doing
    what one is most comfortable with.  Having spent the last 5 years
    flying "lowly gliders" I no longer try to move people where they
    don't want to go.
    
    My editorial is really in response to Bob Kopski's complaint that
    electric flight is not getting it's due(at the NATS etc).  I don't
    blame most people, once the novelty of flying an electric Seniorita
    is over its boring as hell(not that the glow version Seniorita is not
    also boring!).  I am very lucky because I enjoy all types of flight.
    The last two weekends most of the power flyers were grounded due to
    high winds, I was enjoying the best slope soaring of my life with 
    my Fiesta!
    
    Someday I will get into wet power I am sure.  What has kept me out
    up until now is a dislike of ugly inefficient airplanes.  I love
    scale designs but realize that I don't yet possess some of the
    flying skills(ie ROG).
    
    I will be building a 50" span Hawker Hurricane which will have electric
    power, folding prop, and be handlaunched.  While some glow engine
    purists might find this unacceptable, I prefer it to flying a fixed
    gear, constant wing chord, boxy trainer.  
    
    A misconception that needs to be addressed is that high performance
    gliders- either electric or non-electric are not necessarilly being
    flown by "beginners" aspiring to fly glow engine ships.  The skills 
    required to fly these low drag "gliders" are different, but no less
    challenging than their glow engine counterparts.  I let a competent
    pattern flyer try the ARCUS on Sunday, and while he was able to roll
    it, he felt that it "was a handful".  It definitely is more difficult 
    to land than his Bridi XLT!  This is why I think I will be able to
    fly the Hurricane- it is much draggier than the ARCUS and will have
    a lower wingloading, plus it will be handlaunched.  So my first entry
    into "power style ships" will be with a standoff scale Hurricane.
    If I am succesful I think it will prove that glider pilots can fly
    power planes.
    
    Anyway, I seek no converts to gliders or electrics only to clear up
    some misconceptions, some of which are well deserved.  Silent flight
    does not deserve the boring reputation that has dogged it in this
    country.
    
                                                     Regards,
    
                                                     Jim
    
    

Re: electrics at the Nats.

The electric guys DID get the shaft at the Nats. They only scheduled one day 
on site and the off-site location that they agreed to after the complaints
got closed down due to chopper practice blowing it for everyone. A quick 
shuffle and the site got moved to Hadley but not many people caught the change 
and several classes had one contestant.

Tom T.,

Did your club regain use of the sod farm or did you guys loose you field 
because you volunteered it for a Nats practice field? (that s*cks if that's 
the case)

    Dan,
    
       Welcome back to the electric note, it's good to see your logo
    again!  To reply to some of you comments which are well founded,
    as you have flown both electric and gas- unlimited vertical per-
    formance is available only in f3e style electric ships which have
     about 1 minute of motor run available.  Since they climb at better
    than 6000 ft. per minute, a 10 second run usually puts these ships
    at the limit of one's eyesight.  So as we all know the power to weight
    ratio of glow engines is better than electric will probably ever
    be.
    
    Regarding duration, low performance electric flight can extend over
    10 minutes.  High performance (20-30 amp draw) is good for maybe
    5 minutes.  So of course glow engine wins here again.  But for my
    flying tastes, 5 minutes is good enough.  I prefer 5 minutes of
    exciting flight to 15 minutes of boring flight.  Since after 5 
    minutes of concentration I am ready to land(relax), the 5 minute
    limit is acceptable.  I recently attended a funfly where a beautiful
    90" P-38 was flown(twin HP 61's).  The pilot puts on a very scale,
    exciting performance which lasts about 5 minutes.  All activity ceases
    as people crowd to the fences to watch this awesome show, which always
    ends in great applause.  Now before and after his flights hot dogging
    galore goes on for 10-15 minutes at a time(Ultimate bipes, Lasers, etc)
    but nobody really pays any attention after the first minute or two!
    
    I think electric is the best choice for multi-engine flight.  I would
    like to know your view on this.
    
    Electric is much more expensive than glow.
    
    I must admit I really enjoy passing power planes while diving the
    ARCUS.
    
    The Bridi XLT with piped Rossi .61 I saw fly on Sunday was really 
    impressive and very quiet.  I could really get into that kind of 
    performance!
    
    Please share any additional experiences you have with glow and
    electric, I find it very interesting.
    
    
                                               Regards,
    
                                               Jim
    
    

	I recently crashed my ELECTRIC STICK and almost totally destroyed my Futaba
receiver/speed control. I can see that a transistor has a crack in it. I have the skill
 to replace this transistor but do not know what it is. Does anyone have a schematic
for this radio ?


	In a releated matter, DOes anyone know if it is possible to jumper over the
speed control function of this reciever to use another higher ratted speed control
in its place ?



					Larry

Larry, use this opportunity to walk away from this receiver.
It is one of the (only two) receivers in the AMA's 1991 list
that are not safe.  That is it is not capable if safe reception
during 2-IM conditions.

Today only two types of receivers can resist this (now common)
reception problem.  Dual Conversion receivers and JR ABC&W receivers.

When ever two members at your flying site are 23 channels apart
you are in danger.  Worse yet when ever anyone is flying and a paging
system comes on line that is 22 channels away you are in danger.

Additionally this receiver couldn't supply 20 amps without tripping
itself off line because of overheating.

Disclaimer - this is only my opinion.  I could be wrong.  Feel free
to call the vendor and ask if they will guarantee reception when
two transmitters are 23 channels apart.  Your club may have frequency
control that does not allow transmitters 23 channels apart and they
may have regular testing of the airwaves to insure no paging systems
are within range.  Feel free to call me at DTN 293-5695 if you wanna
talk about this.

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

    RE: .493
    
    
    Dan,
    
    yes, I'll be there Sept 19/20. And I'd love to see the KRC meeting.
    Where does it take place? How long would the trip be? With all the RC
    events coming up, I need to plan careful. After all, I have the family
    with me and will leave them alone during the week enough. 
    
    I'll mark my calender. Let's make plans once we are there.
    
    Best regards,
                    Hartmut

	RE .499

	
	What Is 2-IM ? Is it a specification ?

			
				Larry

I'm not an EE but I'll give you a layman's (physicist's) answer.

(There's a big discussion of this in this file in the 1991 radio topics and 
there's an radio_interference keyword)


2-IM stands for second order inter modulation. This is a problem with wave 
functions where the peaks and valleys of the waves line up and you get 
constructive interference (the amplitude adds together). When you have two
frequencies that are different, this happens the difference period number of 
times. If you have something going 10 times per second and another going 12 
times per second then twice per second they'll be in sync and produce a stronger 
signal. Another way to think of it is race cars lapping each other. You get
a peak each time the "cars" pass/lap each other. This secondary signal is
at the frequency of the "lapping" or difference in the frequencies. A 10 lap 
per timeperiod car and a 12 lap per timeperiod car will pass each other twice
per timeperiod giving a "beat" frequency of 2 per timeperiod.

Using this and the fact that our channels are 20kHz apart, RC channels 23
apart will produce a beat frequency of 460kHz. The Futaba single conversion
AM recievers use a reference or intermediate frequency of 455kHz. These two
frequencies are within the 10kHz narrow band 1991 frequency range and therefore
interfere with each other and the Futaba Rx can't get a clear signal. This 
problem is caused by any two RC transmitters 23 channels apart OR RC ch20 and 
the audio portion of TV4. This is why many clubs have banned ch20 in areas with 
a tv channel 4. The frequency of the Futaba system is unimportant since it 
interferes in the reference circuit of the reciever. The Futaba AM Attack radios 
are the ones that this is seen in. (R114H and the 4 channel with built in speed 
control) This is attempted to be controlled at several club fields by putting 
channels 23 apart on the same frequency pins. This is ok where we're the only 
signals but the reason why our recievers are narrow banded to a 10kHz signal 
but 20kHz apart is because there is a pager channel between each pair of RC 
channels. If there's a pager 22.5 channels away from an RC transmitter you'll 
get a beat frequency at 450kHz which is still in the 10kHz narrow band range.
The pagers are the primary users of this band and pop up without warning. They 
don't put frequency clips on out frequency boards so the safest thing is to try 
to phase out the single conversion AM recievers. It's well worth spending the 
extra $20 and getting the 4ch FM dual conversion system.

Of course Futaba has refused to admit that this is a problem. It's a safety 
issue since it can take a plane out of the sky for no apparent reason when a 
pager comes on for a 10-15 second signal at the wrong moment. The radio will 
test out fine when the pager or other transmitter is turned off.

I have a fun-fly plane named 2-IM because it looks like it's being interfered 
with when it flys.

RE: Note 387.501 by BLARRY::Bonnette
>>	What Is 2-IM ? Is it a specification ?

    "2-IM" is short for "second order intermodulation" and the short
    story is that a receiver that is a typical single conversion type
    (as the lowend Futaba AM ones are), then it will be interfered with
    (shot down) by ANY 2 other channels that are 23 channels apart.

    Example:

    - Your Futaba AM single conversion receiver is on channel xx, 
      (Pick any channel - it doesn't matter what channel you're on )
      and you're happly flying by yourself.

    - two other guys show up at the field.  One in on channel 15, the
      other is on 38.  (NOTE: 38 - 15 = 23.)  When both of these guys
      turn on their transmitters, your Futaba AM single conversion
      receiver will be interfered with (shot down).
      
    Note that this happens to ANY channel single conversion recieiver
    and also with any 2 other channels that are 23 channels apart.

    Other things that will generate 2-IM:

     - If there is a TV channel 4 in your area anyone flying RC
       channels 20 or 21 will shoot down ALL channels of single
       conversion receivers.

     - If there is a pager in your area, anyone that is 22 channels
       away from the pager(s) will shoot down ALL channels of single
       conversion receivers when the pager transmits.

    This is why so many DEC R/C modelers are really upset with Futaba. 
    Personally, I will never buy another piece of Futaba equipment
    again.  (I used to have 100% Futaba equipment.)  They are *STILL*
    selling systems that they claim are "1991-Ready" but they WILL be
    shot down by a 2-IM situation.  Futaba is the _ONLY_ major R/C radio
    manufacturer that is selling single conversion recievers.

    [ Note: Technically, JR brand "ABC&W" receivers are single
      conversion, but they are different than the typical reciever 
      and are NOT bothered with 2-IM.  So for the sake of the 2-IM
      argument, the JR receivers "count" as dual conversion. ]

    If you want a _TRUELY_ 1991-Ready receiver, make sure it says "Dual
    Conversion" or "JR ABC&W" on the outside of it.  (Note: As far as I
    know, all Futaba FM receivers are dual conversion.)

    With Futaba AM, "caveat emptor"!

                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |            Happy Landings!
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|              - Dan Miner
     |_/      |___________|  |_________|  |
                      |       /           |     " The Earth needs more OZONE,
                      |      /                       not Castor Oil!! "    
                      |_____/

Well said guys.

>    This is why so many DEC R/C modelers are really upset with Futaba. 

However, Futaba is not alone in the sales of single conversion receivers. 
The ACE AM single conversion receiver is also not 1991 safe.
They also sell a dual conversion AM receiver I believe which is safe.
Also I believe the COX systems may be AM single conversion.

Now if you wanna complain - send mail to the AMA frequency committee.
They wrote the spec that is tested for to get on the AMA 1991 list and
it didn't include any tests for this type of interference.  That was
an oversight - but they have known it was an oversight for YEARS now and
they don't have the guts to change the spec and re-test.

Also playing with the mathematics a bit more.  If two paging systems
are on line 23 channels apart and you are the only one flying you can 
get hit.  Paging systems put out up to 500 watts and your RC Transmitter
puts out .75 watts.  If you fly high then...

Now you might think the probability of two paging systems coming on line
at the same time and 23 channels apart is pretty rare.  Not so.  Many paging
systems keep their carrier up all the time and only modulate when actually
paging someone.  This means that in the right part of the country (or any
part in the future) the single conversion 2-IM susceptible receiver will
NEVER work!  Well - except when you stand real close.   Also it is a documented
fact that many paging systems are operating illegally.  That is they
are putting out more watts than they are licensed for.  The reason - they
can increase their circle of coverage and save the expense of another
tower and make more money.  You get the FCC license then you get a bigger
amp they you make more money.

When the plane hits the ground any good lawyer would be in seventh heaven.
There is negligence abound and all in the principles have deep pockets - 
AMA - radio vendors - paging system owners - FCC.  The little guy fiddling the 
sticks is just the cheese that attracts the rats.

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

	Thanks Dan and Kay for the 2-IM explaination.

	I purchased another set of 7 KR-1200-AE batteries 
and am going to built a second flat pak. I read in this 
note that you should "NEVER NEVER wire Nicads in parallel".
I don't understand why.  Can someone help ?


				Larry

    
    Nicad cells vary in the cell voltage a bit. You'll never find two packs
    with identical voltages. And because their internal resistance is very
    small (milli ohms) the cell with the lower voltage will always
    discharge the one with the higher voltage. That means you'll never get
    the capacity of both packs. 
    
    Bernd

re .-1

	Yes but, if this were a problem wouldn't placing 
cells in series exibit the same problem? We purchase
paks with cells in series in the form of flat paks.


				Larry

    Result of this may be too pretty hot packs (hopefully the vents work
    and keep them from exploding). So, better stay away from that unless
    you want to power your plane with real fire. If you need more capacity,
    wait for the 1800 mAh sub-C Cutoff cells which are anounced (at least
    for Germany) for fall. Evaluation units are already around, and test
    results show capacity slightly higher than the 1700 SCE with voltage
    like or above 1400 SCR or even 1200 SCR.
    
    BTW, regarding the fire: Did you ever hear about the two birdies that
    saw an F16 with afterburner fly by? One says:"Whoah! How fast!" Says
    the other:"Iwonder how fast you'd fly with your b*** burning!"
    
    Best regards,
                     Hartmut

    Re. -2
    
    No, placing them in series is okay since you add up all the individual
    voltages (and resistances). A cell with a little lower voltage adds a
    little less, that's only important for competition purposes.
    
    I f you have them parallel, voltage differences will cause current
    flow. Because of the low resistance of the cells, the current is high,
    the voltage will not drop much. The energy goes from strong pack to
    weak pack and will make them heat up, but you will not necessarily
    increase your motor run time. If you're very luck and the cells very
    much the same, it might work out. But again, the risk is high, and even
    if the packs should be equal today, they might not be after a few
    charging/discharging cycles.
    
    Hope this helps (and is sufficiently correct).
    
    Best regards,
                  Hartmut
    
    
    P.S.: Bernd, wo steckst Du? Geh mal an Deinen Platz und arbeite, ja?
    Da� ich Dich anrufen kann.

    Sometime ago I promised a "real world comparision" of my Astro
    Flight 015 FAI and the Graupner Ultra 900 which replaced it.
    
    The test bed is a Robbe Arcus with 10 900 mah SCR cells and a 
    Graupner On/off switch.  The all-up weight with either motor
    is about 64 oz.  The Astro motor actually weighs about 1 oz.
    less than the Ultra.
    
    The Astro motor cost $99 and seemed to work best with an Aeronaut
    9x5 prop.  It drew about 28 AMPS.  The climb rate was good.
    The 4mm shaft bends easily.  Replacement parts are readily available
    as is factory service.
    
    The Ultra motor cost $227 and works very well with a Graupner 10x6
    prop.  It draws around 40 AMPS.  The climb rate is noticeably better
    than with ASTRO power.  I cannot comment on replacement parts which
    are available from Hobby Lobby.
    
    In the final analysis the Ultra 900 will spin a 10x6 prop with authority
    and the ASTRO won't.  This ability does not come cheaply!  You will be
    satisfied with the ASTRO and amazed with the ULTRA(albeit poorer)!
    The ability to spin the bigger prop is probably most useful for 
    pulling large gliders up to altitude quickly.
    
    Hopefully I will soon be able to report how a Keller 70/4 works
    in a Robbe Calibra Glider.  Frank Weston of Weston Aerodesign told
    me his tests with this motor were disappointing.  Test results from
    European sources say otherwise.  I will report my findings.
    
    Again I ask all contributors to report about equipment they have
    owned- this stuff is too expensive to make mistakes!
    
    On that note let me tell about the bad decisions I have made in
    purchasing chargers.  I started with a cheap AC/DC Aristocraft($60)
    that would only handle 7 cells and could not hold a constant current
    above 2 amps.  I then purchased an Astro 110($85) which was a peak
    detecting charger that would handle up to 12 cells.  This works great
    and is very convenient but now I need to charge more than 12 cells.
    
    So I am looking at buying an Astro 112(currently $75 from Tower) that
    will do up to 28 cells and hold a constant current.  So I will have
    3 chargers and only one is a peak detector for an outlay of over
    $220!  If you think you are going to go with electric do yourself the
    favor of buying a charger that can handle a lot of cells of front.
    
                         
                                                  Regards,
    
                                                  Jim

    Ciao Jim,
    Re. the 70/4: I have some experience with this on 10 cells and less
    than 2 kg (~64 oz) weight F3E with RG15 foil. A lot depends on the prop
    used: all props are NOT created equal. What you need for this is a 11/6
    or 12/6 THIN profile and thin cross section blade folder. Much work has
    been done in this area of F3E: much like transmissions for an auto. I
    have terrible results with the Graupner 11/6 but fantastic results with
    a home made cf/epoxy copy of of the one used by the intl champion
    (whose name I have forgotten...Hartmut must know..). I don't know how
    this motor would work in a larger and heavier plane: it draws a good
    amount of current and needs a slim airfoil to work properly. I have had
    good luck with the 80/6 with 18-20 cells in a 3 mtr 3 kg plane but that
    is different...
    
    So experiment with props; roll your own or modify available ones and
    see the difference. Cheaper than buying motors...
    
    Ciao< Ed

    I called Astro Flight today to inquire if their Mode 112 dc/dc charger
    was capable of slow charging as well as fast charging.  They informed 
    me that it was.
    
    This charger is listed in the new Tower Hobbies flyer for $75, which
    really is a great price(Hobby Lobby wants $104.95).  Nicad packs should
    frequently be slow charged at the c/10 rate to "equalize" the cells.
    I have been using an ACE unit to do this, but it only  will do up to
    10 cells @ 100mah.
    
    Even though the Astro 112 does not have peak detection(you will need to
    us a voltmeter and monitor during the charge) it represents the best
    value on the market.  You will be able to charge up to 28 cells which
    is all you will ever need to do, plus it offers trickle charging for
    pack equalizing.  The only commercially available units that I know
    of that can charge this many cells plus do trickle charging of up to
    28 cells cost $300 and up(SR, Graupner, Robbe).
    
                                                   Regards,
    
                                                   Jim
                       

RE: .510/Chargers

Jim,

I just found myself in the same boat as you. When I picked up R/C again
3 years ago and decided to go electric, I got me a Digital Challenger charger.
I'm not sure whether this (far-east) product is known in the US. It's a very
good peak detection charger that can handle 1 (!) to 7 cells and charge with
up to 10 A. It is very reliable regarding peak detection, has fixed currents of
3.3 A and 5 A and a variable output for 1 to 10 A. It has an LCD display and
can display either voltage, current, or - and that's a nice feature - capacity
charged. This can give you hints on a dying pack. I decided to buy this charger
because the GRAUPNER Ultra Lader was not available by that time and a lot more
expensive. I paid DM 325.- for the Challenger (about $ 220). It still works 
nice ly for all my 6 cell packs, but...

... in the FIESTA, I use 12 cells. Since I don't want to hurt them with 10 A
(although they claim that using 10 A in pulse charging does not hurt at least
the cutoff cells, and car racers do it all the time), charging one pack after
the other takes a lot of time and is simply inconvenient. WIth the advance of
chargers during recent years, I probably can't sell the Challenger for a
reasonable price. I bit the bullet last week and got me the new Graupner Ultra
Duo plus. This one will do all I will ever need. It already knows how to
charge the coming 1800 mAh cutoff sub-C cells. It is idiot proof. Nothing to
adjust. Just plug the battery in, it measures the resistance, decides what
current to use, adjusts current when reaching peak voltage, switch off reliably,
go to trickle (not quite sure about this) and display voltage, current and time
simultaneously during charge and capacity charged when it's done. It can handle
a second 4-cell (receiver) battery as well, and - if you want to - can be 
adjusted to a desired current. It can cycle your batteries as well. It's heart
is a �-processor programmed in high-level language (C), and all error messages
are displayed in clear (German) text. It can charge with up to 4 A, and up to
28 cells (with reduced current for more than 20 cells). I sure hope this is the
last charger I bought in this century.

I got the previous model (Ultra-Duo) last year for Ed Siegmann, and played a
little with it. Since it is limited to 3 A and will reduce the current for more
than 16 cells, I was afraid it would be too small some day again. It probably
wouldn't, but I was so scared to sink another 300 DM into a charger that would 
soon turn out to be too small. And I'd never risk my good packs with a charger
that does not stop charging when the batteries are full. We can discuss whether
peak detection or temperature rise is the best way, but if you have to pay
attention, it will fail one day. And you can never charge a second pack while
you're flying.

Rambled enough... I'll give you a report on the new charger onece I tested it.
I got it last Sunday and shipped it with all the stuff on Monday...

Best regards,
                Hartmut

P.S.: For the red cutoff cells, they don't necessarily recommend trickle 
      charging any more. The manufacturers do, but they recommend 2 A charge
      current maximum as well. The experts I heard talking about this use packs
      that never saw a trickle charge! They quick charge the new packs right 
      away!

    Re: .511
    
    Ed,
    
    with the props from the intl champion you're probably talking about
    Freudenthaler? The ones that are available through aeronaut (and
    robbe)? In colors white or black as glas or carbon reinforced or 'do
    you want the expensive or the very expensive?' Although I assume with a
    motor like the 70/4 you should not try and save 5 bucks by using a
    cheaper prop...
    
    Best regards,
                  Hartmut

	I was talking with a friend of mine about
cleaning motors. He told me he read somewhere that
you should connect the motor to a battery and let it
run while dunking it in a pail of water. While this
may work I have this funny feeling about it. I was 
always taught to stay away from water with electrical
devices. Has anyone else herd of this cleaning technique ?

				Larry

    This idea scares me. I'm not really an expert on electric motors - in
    the sense that I have many and have them running a few hours per week.
    But I know quite a lot of rare-earth magnets (samarium-cobalt and
    neodymium-boron-iron). When we went to buy these magnets for our
    products - granted, disk drives are more sensitive than airplanes, but
    still - we talked about 5 % of the time about the magnet and 95 % of
    the time about coating and corrosion protection. These magnets -
    especially neodymium - corrode incredibly fast when unprotected. And
    I'd never treat them with water if there is any chance to avoid it.
    
    Now if you talk cheap ferrite motors - the magnets are probably all
    that will not be damaged by corrosion. I once had a motor in my UHU
    that frequently got buried in snow for just one day. You know, you land
    it that wonderful powder, and it gets pressed into the fuse through the
    cooling openings. I didn't worry since I expected that the hot motor
    would get rid of the snow/water quickly. WRONG! I damaged the motor
    completely (FAA said there was a piece of ice in the collector), and the
    amount of rust it developed was impressive.
    
    If you ask me, I wouldn't try it (although I read about it, too). Try
    air, brushes, whatever, but not water.
    
    Just mho.
    
    Best regards,
                     Hartmut

    This is a standard way of breaking in a new motor. Not sure how
    good a cleaning job it does. I always used a rubber eraser to 
    clean the comutator.
    
    I believe you just connect the motor to a single D cell and drop it
    into a bowl (or whatever) of water. Leave it submerged and let it
    run out the battery. Sounds crazy, but it works.
    
    Steve

    re: -1
    
    I have heard of this method being used with ferrite motors by
    the RC car guys.  I personally would not try this technique
    with an expensive rare earth magnet motor(KEller,Ultra, AStro, etc).
    
    This might be a good place to discuss the differences between ferrite
    and cobalt motors.  The ferrite or "can" motors as they are commonly
    known work ok in low current draw applications.  They suffer when
    the heat increases which can be caused by high current draw and/or
    long motor runs.  Since RC cars typically draw less than 20 amps,
    these motors work well in that application.
    
    Cobalt motors work best in airplanes where high current draw and
    long motor runs are the norm.  The ferrite magnets tend to demagnetize
    at much lower temperatures than the cobalt magnets.
    
    It is my feeling that ferrite motors used without gearing have
    contributed to electric flight's relatively poor reputation. This
    is not entirely true in multi engine applications where the inherent
    efficiency of multi engines allows them to function better.
    
    
                                           Regards,
    
                                           Jim
    
    
                                                

    I'll go on with neodymium...
    
    Neodymium is at least as critical regarding heat as ferrite. A neodymium 
    magnet will suffer permanent losses above 100�C (212�F). Give or take a 
    bit with different alloys, but that's a valid rule of thumb. This means 
    don't use high currents FOR AN EXTENDED PERIOD OF TIME on a neodymium motor.
    Either keep the current low, or the time (see the motor run times of
    F3E planes: 20 seconds or less).
    
    But you will never ever create a magnet field with the motor coils that
    demagnetizes the magnet. The required field strength to
    magnetize/demagnetize a neodymium magnet are very strong. Even the
    pulses of a motor driven by a switch/relais won't cause magnetic
    losses. Although a controller is still recommended to take care of
    bearings and folding prop.
    
    Neodymium is the highest energy magnet material currently available
    (for production). It is significantly cheaper than cobalt. Although
    it's counted under rare-earth magnet material, it's not really rare.
    Most of the magnet is iron (which explains it's tendency to corrode).
    The price is artificially high through the marketing guys since they
    want to keep selling their cobalt stuff. The main advantage of cobalt
    magnets is that you can use them up to 300�C (600�F) + without getting
    permanent losses.
    
    Best regards,
                   Hartmut

    Re. .514
    
    Ciao Hartmut,
    
    Yes thats the guy: Freudenthaler. The club took up a collection and we
    bought 2 directly ( I believe ther were each in the $75. range ) with
    the stated intent of making copies and improving. He did not mind at
    all so the pattern was made and many props turned out. Quite an
    impressive process with carbon moulds, slow epoxy, carbon fiber and 
    cf mat, kevlar, heat and time. The results are, however, simply great.
    And many people have a good time modifying further by trimming etc but
    the basic ones are great. Also make various sizes and pitches for
    particular motors and even for 6 cell competition. They really do make
    a difference. The home made one I sent you is 'crude' in comparison to
    the new ones.
    
    Ciao e buon volante!
    
    Ed

	In RCM some months back there was an article that had 
a table with various motors with the thrust, current, and prop
size listed for each motor. Does anyone still have this article ?
and would you be willing to reproduce the tables in this note ?
I beleive that there was information on expensive and inexpensive
motors ( I.E. car motors ).

			Larry

    I can provide a thrust chart from Graupner showing the thrust of
    their 11x7, 10x6, 8x5, 7x3, and 6x6 at up to 11,000 RPM.
    
    I am suspicious of these charts because they seem to vary tremendously
    with "charts" you see from other people(ie Hobby Lobby).  
    
    This is why I keep harping on people to share their experience - very
    little "real" data is available for electric motors and props.
    
    Knowledgeable people know how important the correct prop is for good
    performance.  In fact I have read that just using the best prop
    can result in a 20% thrust increase over the wrong one.
    
    I have been told that the larger the diameter, the better the climb,
    and the greater the pitch, the greater the speed.  
    
    For ungeared "can" style motors I think 8x5 is the biggest prop you 
    can possibly use.  A geared Astro 05 spins an 11X7 prop nicely.
    
    A lot of prop and motor selection has to do with what type of aircraft
    it will be used in.  Geared motors tend to work best on draggy designs
    or scale designs where scale speed is desired.  Direct drive works
    best on low drag pylon racers, f3e type gliders, and other "sport"
    type aircraft.
    
    Gearing allows an electric motor to spin a larger prop at lower
    current draw at less rpm.  However since larger props are much more
    efficient than smaller props, often this setup is desirable.
    
    Without rambling much more, I will say that the large electric
    motors seem to work more efficiently than the smaller motors because
    of their ability to swing larger props at higher RPM.  My ARCUS on
    10 cells(64 oz.) with 10x6 prop climbs better than my Uhu on 7 cells
    (45 oz.) with 8x5 prop ever did.
    
    
                                              Regards,
    
                                              Jim

    This weekend while flying the Arcus, a problem with the design
    surfaced.  I noticed the elevator was not returning to the same spot
    each time and also the rudder frequently needed to be "recentered"
    
    The problem is the thin wire rod running in a plastic tube down the
    fuselage is connected only at the ends.  There is no way to "tack"
    it easily to the fuselsge wall.  So the cable inevitably flexes 
    causing centering problems.
    
    I really wish these cables could be preinstalled before the fuselage
    is joined.
    
    
                                                       Regards,
    
                                                       Jim

    Well, 
    
    I guess I should have listened to you guys on the subject of putting
    nicads in parallel. I did it anyway and at first I started blowing my 
    20 amp fuse, SO, I replaced it with a 30 amp. This seemed to work so 
    I flew my PT-electric with the 2 KR-1200 paks in parallel. The flight
    time increased incrediby. I ended up with a 11 minute motor run which
    gave me a 13 min flight. I was very pleased. I opened my battery box 
    on the plane and the paks were VERY hot. I left them in parallel over
    night and the next day I recharged them in parallel. put them in my
    flight box and the next day I went to fly again but the battry paks
    were dead. Well to make a long story short, I found two battery's 
    shorted. since this never happened to me before I can only attribute
    this to them being connected in parallel. So, I'm back to single 7
    cell paks. At least the KR-1200's are lighter.
    
    					Larry

    re: -1
    
    I doubt the KR series batteries can handle 20 + amps efficiently.
    This is why the Sanyo 1700 SCE batteries are not often used, owing 
    to high internal resistance.  I think SCR batteries are best for
    high amperage use.
    
                              
                                                Regards,
    
                                                Jim

    I am going to contradict somewhat the theory that you should not put
    Nicads in parallel.
    
    I have been flying for years a "Diamant" Electric Glider from Robbe.
    
    It is a 3.3 meters glider with a quite powerfull geared motor.
    
    It uses two 8 cells packs. 
    
    Before I had an electronic controller, I had a switch assembly with
    four positions.
    
    Full speed forward -> Two packs in serie
    Half speed forward -> Two packs in parallel
    Off-> Motor shorted/disconnected, the two packs in parallel
    Half speed backward -> Two packs in parallel
    (This last position was the most efficient air brake I have ever had)
    
    As you can see the packs where parallel most of the time, also when the
    glider was grounded. I was (and still am) charging the packs in
    parallel, directly on a car battery in about 35 minutes.
    
    I remember that I made some experiments by loading the packs
    differently, to have about 0.3 Volts difference, and then connect them
    parallel through an Ampmeter to chech the current. It was very low
    certainly much lower than the current that they had to sustain at the
    beginning of the charge cycle, where the difference between the Nicad
    and the car battery is close to 3 Volts.
    
    The current flow also dropped rapidly and reached zero after some time.
    
    Yes there is some loss due to the transfer of energy from one pack
    to the other, but this is marginal. It might even be lower than the
    loss you get through an electronic controller.
    
    NOTE: comment on the previous note about KR packs. When the packs are
    in parallel, each of them only provides half the current, so each pack
    was only delivering between 10-15 amps. If the motor time was about 11
    minutes I would say that it was probably closer to 10 amps each.
    
    I would believe that the shorting of cells in your pack might be
    unrelated to the fact that you did connect them in parallel.
    
    Obvioulsy all of this is only based on my own experience, but the
    switching system, at that time was what Robbe recommended.
    
    Regards
    
    Jean-Paul
     
    
    

    
    I agree partially with what -1. said. The point is if you use two
    very different packs the total capacity will be significantly less than 
    x2, but still more than x1. If you would superposition the two capacity
    curves in relation to the corresponding voltage you could determine
    what your real capacity is. By putting Nicads in parallel your total
    capacity will always be 1 < tot.cap.< 2 times your single capacity.
    
    When putting two fully charged Nicads in parallel and assume they are
    quite different, lets say 200mV, further assume the inner resistance
    of those packs is 0.1 ohm each (probably lower) there would be a
    current of 1 Amp till the nicad with the higher voltage is discharged so 
    much to the corresponding voltage/capacity.
    
    If you now add an amp.meter inbetween you might add significant
    resistance dependent what range you choose. Assume your smallest range
    of your meter is 100mV (quite common), and your pack would differ
    100mv. In this case you could choose whatever amprange you want, your
    reading would in each range be differnt. You could switch to the finest
    range and say 'current is 10 ma (whatever)'. My point here is if you
    want to measure this case you need to be very careful of the
    interpretation.  
    
    I put two single cells in parallel to heat the plugs, works perfect.
    Almost twice the capacity than a single one.
    
    
    Bernd
    
    
    
    

    I would not ever recommend running Nicads in parallel.  The ONLY way it
    will work is if the packs are WELL matched in capacity, age, etc.  Get
    larger capacity cells if you want more capacity.
    
    Charlie
    

    Oh yes, in my statments about putting things in parallel, I had made
    the assumption that we where only talking about very similar packs.
    
    Age, type, number of cells, number of cycles, charge level, etc.......
    
    I also perfectly agree that every measurment in terms of current
    will more or less influence the procees, up to the point where 
    it can become meaningless.
    
    Regards
    
    JP
      

    
    Charging in series help to increase the trouble.....
    If you run Nicads in parallel I'd recomment charging them in parallel,
    too. In this way you enshure best, that both are charged to the same 
    voltage (not capacity).
    
    Bernd

    I received the new Hobby Lobby catalog the other day, and I must
    say I am disappointed.  Kits I was hoping would appear(ie Graupner
    New Match and Aeronaut Surprise 2) were noticeably absent.
    
    The addition of Hectoplatt motors is nice though.  I wish they would
    offer more high performance gliders and electrics from some of the
    other German manufacturers- Bauer, Krause, Multiplex, etc.
    
                                      
                                                       Regards,
    
                                                       Jim

>                      <<< Note 387.532 by UNYEM::BLUMJ >>>
>                         -< Hobby Lobby Catralog #20 >-
>
>    I received the new Hobby Lobby catalog the other day, and I must
>    say I am disappointed.  Kits I was hoping would appear(ie Graupner

But Jim, did you read that description of the aero(aqua)batic submarine.
Claims it can do rolls and reach out of the water 20 inches!

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

    Can anyone of You Guru explain the exact definition of a 
    
         "WET" magnet  ???
    
    WHat material are they made of ?
    
    How compares their magentic flux to standard magnets or rare earth
    magnets ?
    
    best reg. 
    
    Gottfried
    

    re: -1
    
    "Wet" magnets are made of ferrite and epoxy.  In the end they still
    have the same characteristics as any ferrite motor.  Which means
    they work well as long as the heat(current) is kept low.  It is
    my understanding 20 amps is about the limit for ferrite motors.
    The reason for limiting the current is the ferrite magnets can
    demagnetize at high temperatures.  This is why cobalt motors are
    used in high current draw/duration applications.  
    
    
                                             regards,
    
                                             Jim

    I'm glad someone else asked about the wet magnets :^)
    My question is on the timming. My kid is bugging me about a rc truck.
    Alot of the motors I see have certian degrees of timming or they are
    adjustable. Can someone enlighten me.
    Thanks
    Walt

    Timing in an electric motor is where the commutator switches the
    current to a different set of windings.  Rotating the brush housing
    changes the timing with respect to the magnetic field.  Some 
    motors are not adjustable and some are.  Adjusting the timing will
    change the current draw and torque produced.  The main reason for
    changing timing is if you want to run the motor in the other direction. 
    The best timing setting is probably for minimum no load current.  You
    apply a battery voltage to the motor no load and monitor the current. 
    Rotate the housing until you get minimum current.
    
    Charlie
    

    Greetings,
    
     I know this subject has been discussed, but i am hoping there may
    be some new product development:
    
     I am looking to buy a on/off switch with bec. My initial intent is
    to power an astro mini challenger or graupner speed 400 with mini
    olimpus, and therefor think that the Jomar or even Kyosho will suffice,
    but I want to leave the option open to built a 2 meter that uses a 
    Astro 15 FAI motor. This draws 300 amps and i believe that these
    controllers cannot handle this draw. 
    
     Without sacrificing low weight, is there any on/off switch that
    will support both applications, or should i plan on buying a 
    switch for both applications.
    
    
     Thanks in advance for any  input.
    
    mike

RE: Note 387.538 by RANGER::PITONIAK
>>     Astro 15 FAI motor. This draws 300 amps and i believe that these

    There's a typo here.  The motor draws around 30 (not 300) amps.
    At 300 amps, it would look like a flash bulb!!!  :-)

                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |            Happy Landings!
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|              - Dan Miner
     |_/      |___________|  |_________|  |
                      |       /           |     " The Earth needs more OZONE,
                      |      /                       not Castor Oil!! "    
                      |_____/

I've got Lamar's Hobby Lobby catalog in my car from the contest this weekend.
You should get one or borrow it. They have a lot of stuff in there that seems
to fit the bill pretty nicely. Their prices seem to have come down since I 
looked at it last in 1988. They're selling stuff for under list finally.

    Right Dan,
    
     I meant 300 watts! 300 amps would give a hell of a climb rate :-).
    
    thanks
    
    mike

>> 300 amps would give a hell of a climb rate :-).

Yeah, and the battery pack might be a tad on the hot side after a run. Put's a
whole new meaning to "glow gloop!" :-)

-Lamar

>                                              <<< Note 387.538 by RANGER::PITONIAK >>>
>                                                      -< BEC/Swith question >-
>     I am looking to buy a on/off switch with bec. My initial intent is
>    to power an astro mini challenger or graupner speed 400 with mini

Here in lies the rub.

The Astro Mini-challenger uses a 5 cell pack.
Most (maybe all) speed controllers (or on/off devices) with BEC
won't work on only 5 cells.

So the active question now is...

Does anybody know of an on/off switch with BEC that works with a
5 cell pack?

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

>> Does anybody know of an on/off switch with BEC that works with a
>> 5 cell pack?

    Not for sure, but Jomar might have one???

                                - Dan

    If there is one, be sure to know how it works before you trust it. The
    main thing with a BEC (controller or switch) is that it needs to make
    sure the motor will be switched off in time to give you a few minutes
    of juice for the receiver to do a controlled landing...
    
    Since there is at least a .7V drop over the regulator of the BEC
    circuit, the battery has to supply 4.8V (receiver) + .7 (regulator).
    This corresponds to a battery voltage of 5.5 V or 1.1V/cell. With a
    load like an electric motor, you will probably have that seconds after
    takeoff if not before.
    
    One of my BEC controllers had to be modified by the manufacturer to
    make it work with 6 cells, so I doubt you'd get anything that claims to
    work with five. And again, if it does, better make sure you understand
    how.
    
    Just mho.
    
    Best regards,
                   Hartmut
    

    On page 35 of the new Hobby Lobby catalog a Hitec speed controller
    for use with 5-7 cells is offered.  It has BEC and sells for $57.
    
                                             Regards,
    
                                             Jim
    
    By the way, the Astro mini challenger is designed to use the
    Astro 035 direct drive motor which runs well with 6 cells.
    Just be sure there is enough room for the 6th cell.

    I was thumbing through the new Model Builder Magazine yesterday
    and was reading about the annual Astro Flight electric contest
    held in California.  
    
    I noticed Steve Neu's entry in the unlimited class was an
    original design powered by A Keller 70/4 on 10 cells.  The
    all-up weight of this 64" wingspan ship is 55 oz.  Steve is
    a member of the US f3E team and I am wondering if this ship
    is the one he will use at the world championships.  I have
    read about a small faction of f3e flyers in Europe trying
    smaller lighter designs.  Since I am now the proud owner of
    a Keller 70/4(thanks to Hartmut) I am impressed that a 
    world class flyer is using one.
    
                                          
                                           Regards,
    
                                           Jim

    I received my new RCSD magazine and lo and behold, the long awaited
    Flite Lite Composites(Mark Allen, Falcon 880 etc) electric sailplane
    is finally available.
    
    The full page add shows a photo of the tips-up soarer with the
    following specs:
    
    Fuselage - Kevlar reinforced fiberglass
    Wingspan - 80" Obechi covered white 1.5 foam(pre-covered available)
    Airfoil - E387
    Weight with Astro 05 and 7 cells - 38 oz.
    Weight with Astro 015 and 10 cells - 43 oz.
    
    The add proclaims this to be the highest performance 7 cell duration
    kit available.  It also claims to be easy to build - "You don't need
    a degree in composite engineering to build this one" the add states.
    Battery change without removing wings is also listed as a feature.
    These remarks are obviously directed at Mr. Weston's electric
    offerings which feature all kevlar construction.
    
    Several things interest me about this ship.  First and foremost,
    Mark Allen has a great track record for winning designs(F3b eagle,
    Falcon 880, Swift 800, etc).  Secondly the venerable E387 airfoil
    again shows up on a new offering.  Brian Agnew's HLG Vertigo and
    new 2-meter Banshee also use this foil.  The Hobby Lobby Sunfly
    and Freudenthaler's own unlimited f3e ship also use a "modified"
    E387.  Interestingly enough Dodgson dropped the E387 for the S7037
    on his Pivot.  Anyway the E387 is certainly showing up on a wide
    variety of ships.  Up until now it seems Mark Allen has favored the
    Selig airfoils.
    
    The kit without presheeted wings is $150, the kit with presheeted
    wing is $240.  Weston offers his electrics at $99 for the unbagged
    version and $229 for pre-bagged wings and empennage on the 10-550.
    
    I think these two manufacturers are probably offering the best
    American made electric sailplanes.  I may be able to report on
    the Waco 550-10 in the future, the prebagged version makes it
    attractive to the non-bagging literate community(me).
    
    
                                                 Regards,
    
                                                 Jim

RE .548 

Jim,

Do these ships use geared or direct drive motors? Since I've been flying the 
Pulsar, I too prefer fiberglass fuselages to built up. As I stated elsewhere
in the notesfile, I'd like to build a "poor man's" 7 cell F3E type ship. 
Actually, I don't know if I call it an F3E ship. The ship in my mind will be a
flat wing aileron(and maybe flaps or flaperons) bird. I was thinking of a two
meter sized plane, but have decided to go with a standard class(100" wing span)
sized ship. Do you think an Cobalt 05 will be sufficent for a plane of this
size?

-Lamar

    Lamar,
    
    forget the sizes you're talking if you really want to get something
    that reminds of F3E like performance and speed out of 7 cells. The
    first kit I've seen advertised for a 7 cell hotliner is the new
    Graupner New Match. It's not in the latest Hobby Lobby Catalog, and
    it's not yet out in Germany. It's got around 60" wingspan, and the
    reason it's not out yet is because it's built so light and gets so fast
    that prototypes were ripped apart in the air.
    
    Competitive F3E planes (poor man's, used to be rich men before they
    started this hobby) have 27 cells and a wingspan of about 80". All up
    weight is about twice the battery (5 lbs).
    
    I am convinced you can get a 100" ship up on 7 cells with an ASTRO 05
    (probably better a geared one). But this is going to be a floater kind
    of plane with a moderate climb rate. Nothing like F3E, but more flying
    for the money.
    
    Just mho.
    
    Best regards,
                   Hartmut

Thanks Harmut! I guess I've been sniffing too much epoxy lately(right Jim R!)
I guess I'm looking for a semi-floater type. I hate dragging out the high start
during winter and wanted something a little more "spirited" than the standard
electric gliders(Spectra, Electra, and Eclispe) that are out there. I bought a
used Uhu and will fly that for a while, but the fuse is in rough shape. The
Hobby Lobby stuff is nice, but most of the ships are out of my price range. 

I guess I should go back to a two meter sized fuse as the basis of my "design."
I want to stick with the 7 cell/cobalt 05 setup since that's what I have. The
two meter fiberglass fuse(Pluto) from Quality Fiberglass should have plenty of
room for the batteries.

-Lamar

    re: -1
    
    A geared Astro 05 motor on 7 cells takes my father's 112" built
    up Mirage sailplane with a flying weight of 54 oz. up at a 
    steady, unspectacular rate.  In calm conditions, a climb to
    winch altitude takes 45 - 60 seconds.  As a point of reference my
    Arcus climbs to the same altitude in about 15 seconds.
    
    To answer you question, I think a Pulsar with an 05 motor would
    have awfully anemic climb.  It would work well with a Keller
    40/10 motor on 10 cells or a geared Astro 015 on 12 cells.
    
    The biggest problem with turning conventional sailplanes into
    electrics is weight.  Todays high performance sailplanes have
    strong heavy spar structures to accomodate 12 volt winch launches
    without folding the wings.  Electric flight does not put this 
    kind of stress on the wing, hence much lighter wings can be used.
    As an example, the weight of the Legend's spar is greater than the
    entire airframe of a Flite Lite or Weston Aerodesign electric!
    
    Floater type sailplanes(Gentle Lady, etc.) seem to work well with
    geared 05 motors.  It takes a powerful motor and a low drag
    design if the starting point is sailplane with a 10 oz. wing
    loading. 
    
                                          Regards,
    
                                          Jim
    

    Well this weekend I managed to rip the left wing off my ARCUS.
    It was totally my fault, I have been getting carried away with
    high speed runs, and it finally caught up with me.  The ARCUS
    is really a high performance *GLIDER* and I have been flying
    it like a pylon racer.
    
    I learned several things from the accident.  I was not using
    low rates on the elevator when the incident occured.  I put
    a little too much up elevator in when pulling from the vertical
    dive which overstressed the wing ripping it clean off!
    The wing did not break at the fiberglass bandage which joins the
    two wing halves together.  I also now have total faith in the
    two smallish nylon wing holdown bolts.  The wing will break
    before these bolts fail.  Indeed they were still both intact after
    the crash.  
    
    The wing is the old style "Siros"(balsa covered urethane foam).
    I have a new set of wings which are the Rhonefugel(sp?) using
    expanded bead white foam covered with obechi.  I think they will
    be stronger.
    
    The Arcus will fly again with the new wings, however I now intend to
    fly it in a more civilized fashion for which it was intended.
    I will be more careful with the Calibra which I hope to have flying
    within two weeks.
    
    I am now strongly fighting the urge to order A Waco 550-10.
    
    
                                                      Regards,
    
                                                      Jim
    

    In perusing the "new" motor tables in the latest Hobby Lobby
    catalog, an interesting situation exists.  First let me say that
    these tables are probably somewhat optimistic, but I appreciate
    the data(prop,rpm,current, voltage) rather than just saying a
    certain motor is 400 watts.
    
    The case is the Graupner Ultra 1600 motor which is tested with
    14 cells and 16 cells.  The specs are as follows:
    
    14 cells***12x7 prop***35 AMPS***8400 RPM = 75 oz. thrust
    
    16 cells***12x6 prop***46 AMPS***8900 RPM = 80 oz. thrust
    
    
    Two things really stand out here.  First the net gain in thrust is
    only 2 oz. (assuming use of 1000mah cells @1.5oz each) because the
    added weight of the 2 extra cells deducts 3 oz. from the 80
    oz.(80-3=77oz.)  Now for a lousy 2 oz increase in effective thrust,
    the Ultra 1600 draws 11 more AMPS!
    
    This reduces the run time(using 1000mah cells) from 103 seconds(14
    cells) to 78 seconds(16 cells).  Hence, three 30 second motor runs
    with a 13 second botched approach burst are possible using the 
    Ultra 1600 on 14 cells.  The same motor on 16 cells would only
    allow two 30 second climbouts with an 18 second reserve.  In essence
    you lose one climbout per charge cycle = 33% less flying.
    
    If the Hobby Lobby data is accurate, we must conclude that the Ultra
    1600 is a 14 cell motor.  The efficiency drops dramatically with
    the addition of the two extra cells.  The two additional cells provides
    a 14.3% increase in voltage which results in a 31% increase in current
    consumption with only a 2.6% increase in effective thrust gained.
    A poor trade off indeed, as the 33% decrease in runtime verifies.
    
    I am planning to try my Keller 70/4 on 14 cells with a 10.5X6
    Freudenthaler prop.  Although the Keller is designed for 10 cells,
    the literature states that it can be used with more cells if a
    sufficiently smaller prop is fitted(a 12.5x6 was recommended for 10
    cells).
    
    This example really shows the importance of matching input voltage
    and propeller to the individual motor to achieve the best performance.
    
    
                                                  Regards,
    
                                                  Jim
    
    
    
    
    
    
    
    This dramatic example shows how essential it is to   
    

    Last night I finally received some literature from FLite Lite
    Composites.  It looks like the sale of the company to Ron Vann
    will result in better service and quicker product delivery.
    The literature says allow 1-2 weeks for delivery, under Mark Allen's
    ownership, I have heard of people waiting 6 mos. to receive a
    Falcon 880!
    
    Anyway, they list a 60" electric for 7-10 cells utilizing SD8000
    airfoil with a T-tail and 400 sq. inches of wing.  The flying
    weight is listed as 36 oz with 7 cell and 39 oz with 10 cell.
    The kit is available in presheeted version only(obechi over
    white foam with carbon reinforced trailing edge) for $175.
    
    Sounds like a nice sport electric and a great "poor man's
    f3e ship".  Should go vertical with 10 cells and Astro 015FAI!
    
    It's nice to see these new electrics available.
    
    
                                           Regards,
    
                                           Jim

    Well I broke my promise that the Robbe Calibra would be my last
    plane this year.  I ordered a Waco-550 with pre-bagged wings and 
    empennage($229).  I really want to see what an all composite ship
    is really like in terms of durability, strength, and finish.
    
    As a point of reference, the finished calibra wings including two
    JR 341 servos weighs 22 oz.(80" 535 sq inches, obechi over white foam).
    Frank Weston claims the Waco airframe(fuse and wings, no servos)
    weighs 15 oz.  The ship is entirely built of Kevlar.
    
    I had a long talk with Frank Weston about the ability of this ship
    to sustain high wing stress(like when flying under the Limbo bar
    in F3E), and he thinks its plenty strong.  We'll see.
    
    I mentioned to him that competitive 10 cell f3e ships in Europe
    typically weigh about 60 oz.  He claims that his ship flys best
    with AStro 015 FAI which results in a flying weight of about
    45 oz. which gives a wing loading of a little over 11 oz/sq. ft.
    I am concerned that it won't have the necessary speed at this
    "sailplane" wingloading.  That lead to a discussion of all the
    compromises in designing an F3E ship.
    
    Anyway I will report on the "kit" when it arrives.
    
                                                Regards,
    
                                                Jim

    Jim,
    
    it was probably obvious to anyone following this string that it
    wouldn't take long until you'd ordered the WACO. Poor guy. If you
    weren't poor from the Calibra and the Ke70/4, you might be now. If I
    can ever help you out with a few slices of bread and some water, let me
    know. We can make a deal for just a little sticktime :-) :-)...
    
    Now wouldn't the WACO be the right plane for the Ke70/4 on 10 cells?
    Since it's exactly designed as a 10-cell F3E ship from what I
    understand - as is the motor - it should be a pretty good combination.
    
    What other motors are recommended in the Calibra instructions? Is the
    70/4 with 12 to 14 cells one of them?
    
    Another curious guy sticking it's nose into hotline electrics...

    re: -1
    
    I am truly done with kits for the rest of the year!  I really
    wanted to check out an all composite ship, and the WACO is the only
    one that fits the bill.  My goal is to get into cutting cores,
    bagging wings, and molding my own fuselages.  These skills will
    come slowly since their is no local activity to learn from/help
    with.  Ultimately I would like to design and build my own ships,
    but I need a flying stable to keep up the learning curve.
    
    Last night I hooked the Keller 70/4 up to 10 cells and ran it for 
    the first time.  It is incredibly smooth!  I used a Graupner 10x6
    prop and measured the current across a calibrated(supposedly) shunt.
    My reading of 25 Amps is much different than the 37.1 amp draw
    reported Stephen Mettam(British national F3E team member) with an
    identical setup.  Either my shunt is no good or I am really going
    to be in good shape with the Keller.  I will test again tonight
    by recharging the battery and timing the discharge to calculate
    the approximate current draw.  I plan to prop for draw between
    40 and 50 amps.
    
    I attempted to place as many 1000 mah cells as possible in the Calibra
    last night as would fit.  The max is 16.  So I will run 14 with
    the Keller.  I probably will put my Ultra 900 into the WACO and
    my ASTRO 015 into the ARCUS with new wing.  I should be able to
    fly continuosly with these three ships - one flying, one cooling,
    one charging.  I have really gotten hooked on the speed possible with
    high performance electrics, but it is expensive.  I now own most of
    the basics - programmable radio, chargers to do up to 28 cells, and
    about 10 micro micro servos.  Hopefully the future expenses will be
    less.  
    
                                               Regards,
    
                                               Jim 
    

    RE: -.1       -< Guilty-Yes!!!!! >-
    
    
    Five exclamation marks make me wonder whether there is a chance for
    recovery. Probably not...
    
    How do you drive the motor? Controller or switch? If you use a
    controller, make sure that it doesn't limit the current. The
    controllers I know are designed to limit the current to prevent
    overheat or damage when the motor is blocked (crashed). To be honest, I
    tried to run your motor when I first got it. I ran it with a Carbon
    prop from Ed Siegmann and had it hooked up to a controller and my
    calibrated shunt (this one is good, I got it checked in KBOs
    calibration lab). It showed only 35 A on 12 cells, and I had expected a
    lot more. I did not investigate further (after all, it was not my motor
    to play with). Later on, it dawned on me that it probably didn't get
    14.4 V, but a lot less since the controller is rated for 30 A and is
    proven to reduce power when the current is exceeded.
    
    If you plan to go out with all 3 models - will you use 3 radios, too?
    If not, I'm afraid it's the situation where you will - sooner or later
    - forget to switch model memories. A help here would be to to equip one
    plane with a PPM, the other with a PCM receiver. But the third? And you
    will want to use different setups and really take advantage of your
    computer radio, won't you?
    
    I just had to ask, I know Murphy...
    
    Best regards,
                   Hartmut
     

    Hartmut,
    
           I am using an Astro 205 speed controller rated for use
    with 7-28 cells at currents up to 100 amps. It has soft start
    and a brake, it was designed for unlimited f3e ships, it is a
    very robust unit and much cheaper than the Sommerauer's.
    
    All ships fly using the JR X-347 Radio which has 4 model
    memory.
    
    Your data on the current draw of the Keller certainly seems 
    commesurate with mine.  If this is true, I hope to draw less
    than 40 amps with a Freudenthaler 10.5x6 prop, which should give
    me good runtime.
    
    The Calibra will probably weigh about 77-80 oz. and it has a lower
    drag wing HQ1.5/9 than the Arcus which only weighed 64 oz.  The
    extra weight and lower drag should increase the speed.  I must
    be careful not to rip the wings off this one!
    
    Ed Siegmann sent me a note telling of one of his club members
    ripping the wings off his Arianne while diving for the limbo gate.
    So I am not the only one with fat thumbs!
    
    The reason I have become so hooked on f3e is it offers the best of
    power flying and gliding.  High speed, aerobatic planes with no
    noise.  The design considerations and tradeoffs offer a lot of
    room to experiment and innovate.
    
    The current trend in the heavy duty US f3e circles is planes with
    a wingspan of about 64" and 475 sq inches, utilizing 27 cells
    with AStro 60 FAI or equivalent.  Wing loading is over 26 oz./sq. ft.
    
    Have you any access to the German magazine Elektroflug(spelling may
    be incorrect).  I would love to see that magazine.
    
                                                  Regards,
    
                                                  Jim 

    Jim,
    
    > All ships fly using the JR X-347 Radio which has 4 model
    > memory.

    Yeah, sure, but how will you remember to switch memories EVERY FLIGHT!
    
    > Your data on the current draw of the Keller certainly seems 
    > commesurate with mine.  If this is true, I hope to draw less
    > than 40 amps with a Freudenthaler 10.5x6 prop, which should give
    > me good runtime.
    
    Maybe I wasn't quite clear, but I don't really trust my measurement
    since I had the controller in between that possibly limited the current.
    Unfortunately, I didn't check the motor voltage. That would have indicated
    whether the controller had started to shut the motor down. That is what
    I suspect, so the current of 35 A with a prop of unknown dimensions doesn't
    really say much.

    > The reason I have become so hooked on f3e is it offers the best of
    > power flying and gliding.  High speed, aerobatic planes with no
    > noise.  The design considerations and tradeoffs offer a lot of
    > room to experiment and innovate.
    
    I think it's hard to see an F3E plane fly and not get hooked. I will 
    never forget the Ariane they flew in the break of the Ducted Fan Contest
    in Bad Woerishofen. What a nice way to show to DF people what speed is.
    many jets looked pale compared to the Ariane.

    > Have you any access to the German magazine Elektroflug(spelling may
    > be incorrect).  I would love to see that magazine.
    
    If you mean the special editions of FMT (flug und modelltechnik) that
    appear once a year and only cover Elektroflug (and are named that way),
    yes, I have them all, and I even have them with me. I also receive the
    Aufwind, a german magazine covering only gliders, electrics and 
    experimentals. I really like that. It appears every other month, and I 
    have all mags here. It covers all F3B/E/J and HLG events of Europe.

    I can send you the Elektroflug's tomorrow if you give me your mailstop 
    (through mail). What about your German? I might even get you in contact
    with a college friend of mine who works with Kodak and went to Rochester
    yesterday...

    Let me know what you need.

    Best regards,
                   Hartmut

    Ciao Jim and Hartmut,
    
    Nice to hear you guys are having fun with 'beginners electrics'...;-)
    Perhaps should move to F3E or some such so as not to scare away the
    begineers... Don't forget that current draw does not necessarily
    translate linearly into thrust. In particular the prop I sent Hartmut
    was optimized for minimum current and maximum thrust by using profile
    and thickness parameters and incremental pitch change towards the
    extremity. In fact this model has been improved upon somewhat and there
    is s big difference when unloaded in flight: static tests don't really
    tell the whole story, especially as you push the envelope. 
    
    Note also that 'they' now cut slots immediately in front of the two
    brushes (4 for the Astro 60..) and form a little duct to direct the air
    onto the brushes. Likewise they make a cut out aft the wing to draw out
    the hot air past the brushes and out the back. This does no appear to
    affect the speed appreciably as the cutouts do not extend beyond the
    profile of the fuse but are indented slightly to provide the duct
    effect.
    
    The biggest expense and greatest art is the wing: profile, accuracy and
    robustness. For the airframe lightness and ability to remain stiff
    during the manuevers is the key. Profile is more or less round to the
    wing mounting then a vertical ellipse aft to the tail. Use of the
    Kyosho micro in the fin, running the control internally to the center
    of the elevator thereby eliminating more drag and slop. Internal
    aileron controls (not exposed) are tricky to make strong and one-piece
    wing using top surface covering for the integral hinge also used to
    good advantage. Make the servos work harder but who cares for 8 min
    flying...S133 in wing as Kyosho not as strong or fast in this
    arrangement. 
    
    Enjoy e buon volante! Ciao< Ed

    Greetings Ed,
    
                Always good to hear from you!  Thanks for the quick
    reply to my inquiry the other day.  I agree 100% with everything
    you are saying about props.  I have read and I believe it -
    you can increase your thrust by as much as 20% by using the
    optimal prop for your airfoil, motor, battery setup.  This writer
    says do not go to another motor without first finding the best
    prop for your current setup, you might be amazed at the difference
    the right prop can make.
    
    Current draw alone certainly does not guarantee better performance.
    It seems there are very few motors/batteries that can deal with more
    than around 50 amps efficiently.  The heat losses are just too great.
    
    I ran the Keller 70/4 last night at the field using a club members
    hand held tach.  The results were identical to what I had read
    from Stephan Mettam:
    
                       Prop - GRaupner 10x6
                       Current - 37.1 Amps
                       RPM- 10,100 for about first 10 seconds then
                            then slowly drops in linear fashion
                            with the applied voltage.
    
    
    The difference was this time I charged the 900 SCR's at 3 amps.  The
    night before I had slow charged at 1 amp.  As I have suspected, my
    peak detecting charger does not work correctly at chharging rates below
    about 2 amps.  So my Shunt works, my voltmeter works and all is on
    par.  I will report the results with 14 cells when available.
    
    I agree with Ed, "the wing is the thing".  Thank goodness for the
    pre-sheeted/bagged products now coming on the market.  Although
    none are competitive in F3E, they give us beginners a chance to
    experience a "sportsmans" version of what things can be.
    
    It has been really interesting to see the evolution of f3e from
    the late 1980's till now.  Wingspans and weight have gone down,
    rudders eliminated, and power increased. The FAI's adoption of
    a minimum surface area of 550 sq inches for 10 cell f3e is an
    attempt to tame the tiger and encourage more activity in f3e
    by having a class with slower speeds and lighter wing loadings.
    
    I am not optomistic about F3E growing in America due to the
    general distaste for gliders, electric power, and organization
    required to practice/run any f3*(f3b,f3e,f3f, etc) event.
    
    I have maybe 20-25 flights on my Robbe Arcus, I have specked it
    out in thermals, done a bunch of mindless high speed passes,
    learned to do rolls and inverted flight.  I am now bored of 
    punching holes in the sky and ready to apply the ship and my
    skills to a task.  This is why skiers race, golfers start
    keeping score, (ditto tennis palyers), bowlers join a league
    etc.
    
    I used to go hit tennis balls with people, shoot baskets, etc.
    and found this very relaxing.  No scores, no anxiety no measure
    of how you did at the end of the session.  This is like taking
    my Paragon up on a slope sitting in a lawn chair and enjoying
    the day- great therapy, I really love doing this.
    
    However for some unknown reason, I get psyched up when I read about
    high performance ships.  I don't know why.  My father does not.
    So I buy one and fly it casually for a while.  Now I want to
    see what it and I can do and have the fun of trying to improve
    both.  This is the essential difference between a sport flyer 
    and an F3* flyer.  Neither is superior- just a difference of
    outlook.
    
    Enough philosophy.
    
                                               Regards,
    
                                               Jim 

    The annual KRC electric funfly is behing held over the weekend of
    Sept. 19-20 in Quakertown, PA. at the Buc-Le Aero sportsman field.
    I am hoping to attend and was wondering if any other Deccies were
    planning on attending.
    
    This is the premier electric event in  this country and possibly the
    largest in the world.  You see all types at KRC- vintage to ducted
    fan.  It is the best funfly I have ever been to.
    
    If you come away from KRC and are not enthused about electric flight,
    you never will be!  I think a lot of people believe this meet might
    be a bunch of boring electrics.  It is a great show even if you
    have no interest in electric power.  The diversity of planes and
    flying skills is tremendous.  At most funlfly's you don't see to
    many flying wings(much less 4 engines, with retracts) or multiengine
    aircraft.  You will at KRC.  At most meets of this scope, spectators
    can't freely mingle with the pilots on the flightline.  You can at
    KRC.  In short it is a great event.  Hope to meet some of you there.
    
                                                    Regards,
    
                                                    Jim

    When I got home last night there was a large box in my foyer.  It
    was my WACO 550!  It was supposed to take 2-3 weeks to get here,
    but it came in 4 days!  I was surprised.
    
    I have talked about this ship much in previous notes, so I figure
    I owe a kit review.  The first thing that struck me is the lack
    of parts.  I bought the pre-bagged version which came with
    a one piece wing, a fuselage pod, a fuselage boom, 2 stabs(V-tail)
    a ply motor mount, a ply wing mounting plate, 2 ply control horns,
    a length of servo wire, a couple Dean's connectors, 2 pushrods w/
    clevis, and 2 small pushrods for V-tail control.
    
    The instructions are sparse, photocopied on 8.5x11 paper with a
    few diagrams.  This is not a beginners kit!  
    
    This ship in the Weston philosophy is purpose built(read not overbuilt)
    for the task at hand.  Getting 10 cells and all the associated 
    hardware(motor,BEC,RX) into the fuselage is going to be a real
    chore.  There is no room to spare.
    
    I am impressed with the wing which is incredibly smooth and thin
    with sharp trailing edges.  I am not sure how to clean up the
    kevlar flashing- I am going to experiment with heating a #11
    X-ACTO with a propane torch to cut and then simultaneously
    cauterize the Kevlar.  When you sand it, it tends to fray
    terribly.  Running the servo wires out to the cavitites(in the wing)
    which I must cut, looks like it will be tricky.
    
    Mounting the servos in the V-tail also looks like it won't be
    much fun.
    
    In summary, this is a no nonsense competition ship.  It is not
    for the beginner, and probably will not tolerate beginners mistakes
    in building or flying.  When you open up a kit from Robbe or
    Graupner you say "wow what quality".  When I opened up my Weston
    kit, I wasn't sure what to think.  There is no glitz, pretty
    pictures, decals etc.  In the end, a competitive 10 cell F3E
    ship will need 550 sq inches of surface area, be very light and
    strong, and have a low drag airframe.  The Waco 10-550 fulfills
    all these requirements.  It particularly shines in the area of
    strength and light weight.  This ship is probably the only
    commercially available f3e design.  Until now, you would have
    to scratch build this caliber ship.
    
    I will report on the flying performance in the future.
    
                                                Regards,
      
                                                Jim
    

    Last night I ran the Keller 70/4 on my bench with the 14 cell
    1000 mah pack that I had made up.  The pack was brand new and
    trickle charged @ 100mah for 12 hours.  A  Graupner 10x6 prop
    was used with AStro 205 speed controller.
    
    I could not believe the blast of power that occurred when I switched
    the motor on!  The initial current draw was 54 Amps.  When I charge
    at 3 amps, I suspect the current draw will rise to about 60 amps
    or so.  The motor, batteries, and speed controller remained very
    cool during 20 second power bursts, of course they were laying
    on the bench and the prop wash was strong enough to blow the 270
    mah receiver pack right of the bench!
    
    I think this will be a potent combination for the Calibra.  Level
    flight speed should be greater than 60 mph with motor on.
    My thanks to Hartmut for securing this fine motor at a great price.
    
                                  
                                                  Regards,
    
                                                  Jim

    You're very welcome, Jim! I'm happy you like the motor. After all, I
    think it was a little risky for you to order a motor you never saw
    before through a person you never saw before, either.
    
    But this might change! I talked to my college-buddy last night, and
    we'll probably stay overnight in his apartment next weekend when we go
    to Guelph via Rochester. I'll send mail regarding our latest plans.
    
    See you soon,
    
    Hartmut

	I think I found an inexpensive power plant for the PT Electric.
I purchased:

		1 Kyosho Lemans 360 motor      $17.00
		1 Master Air screw 2.5:1 gear  $13.00
		1 10X7 prop                    $ 1.30
					     ----------
					       $31.30

	This combination provided me with a 13 min flight with plenty of 
power to fly even with a 10-15 MPH wind. The Battery packs I used were
7 cell KR-1200 packs. The motor at full throttle drew Approx. 18 amps. 
I flew it most of the flights with less than Half throttle. I don't know
what the currnet draw was at half throttle.


					Larry

	One other thing, During my last flight I lost my prop. 
I don't mind loosing the prop but the prop adapter is strange.
it connects to a 3/16" shaft. I cannot find another adapter
of this type. does anyone know where to get this type adapter ?
Or, Has anyone in the Killingly CT. area seen my prop ? :-)

					Larry

    re: -1
    
    Larry,
    
         Hobby Lobby has all types of propshaft adapters for 3.2mm
    can motors.  Their phone # is (615)373-1444.
    
    
    I spent quite a bit of time over the weekend building the WACO
    10-550 and doing a lot more headscratching than building.  I
    have come to the conclusion that I will not be able to fly this
    plane with 10 cells.  The only way to use 10 cells would be to
    remove the batteries, the BEC on/off switch, and the receiver
    everytime I charge.  While this is standard procedure for many
    f3e designs, the fit is just to tight.  I also do not like the
    servos in the V-tail arrangement.  I will run the ship on 7 cells
    with my Astro 05 FAI.  I will mount a single servo in the fuselage
    to run both ruddervators, so it will function as elevator only.
    
    Sanding the Kevlar away to the Spectra leading edge on the wing has
    been a tedious job.
    
    The all up weight will be 42 oz. which will give an 11 oz/sq ft
    wingloading.  
    
    At this point I could only recommend this ship to a person who was
    serious about competing in 10 cell F3E events.  It is just too
    much of a hassle "squeezing" all the equipment into the tiny
    fuselage for anything other than a competition environment.
    
                                               Regards,
    
                                               Jim

Jim,

Why not set up the ship for onboard charging and only remove everything at 
home for maintainance? I would think that you could wire in another Sermos 
connector to be accessable for charging through the hatch without removal. 
The only thing this negates is the swapping of batteries to provide constant 
flying on a single model. I'll admit that the KS-10 servos in the tail 
bothers me too. I've got a pair and I wouldn't trust them at the speed 
you've been talking about with this.

Now stop whining and get that F3E ship built like you expected before you 
recieved the kit. Remember, the entire notesfile is watching 8^)

    re: -1
    
    Hatch? What hatch? There is no hatch!  The only opening to the fuse
    -lage is under the wing saddle.  The fuselage is tiny it weighs
    only 2.5 oz.  To use 10 cells in this ship, I would have to buy
    600 mah cells, a Bec on/off switch, canon or kyosho servos are
    recommended for the V-tail.  There is no margin for shifting
    the batteries around to get the CG right.  If it doesn't come
    out right, I don't know what you would do.  Running it on 7
    cells leaves a much bigger margin for adjustment. 
    
    All is not lost, I plan to use the wing on my modified Elektro
    Uhu with 20 cells and an Astro 40 FAI.
    
                                                   Regards,
    
                                                   Jim
    

Well, replace hatch with wing and you get the idea. You wouldn't have to 
remove everything in order to charge. I just thought you might need an 
inspirational nudge after talking the poor man's F3E up so much.

Just out of curiousity, how thick is the tail where you'd embed the servos?

    RE: -1
    
    A Futaba S33 will fit between the Kevlar tail skins at the widest
    point on the stab.
    
    If the fuselage was 1/2" wider, it would make all the difference in
    the world.
    
    I now see why Flite Lite's adds talk up the advantage of having a 
    hatch on their electric designs.
    
    When I saw Steve Neu fly his F3E ship at KRC last year, he had to 
    remove all the equipment(reciever included) and charge all the
    batteries outside the fuselage, then stuff everything back in.
    
    I am sure you could get 90-95% of the performance with 100% less
    hassle, but just increasing the fuselage width ever so slightly.
    World class F3E flyers go to extreme lengths to lighten their
    ships and reduce drag.  Weston has followed suit.  
    
                                                   Regards,
    
                                                   Jim
                           

    Weston's logic for using V-tails is somewhat sound.  When I was 
    unable to get crow and ailerons to function on my ARCUS(result of
    going to a 5 channel radio)simultaneously, the landings were pretty
    hot.  This resulted in the T-tail stab breaking off several times.
    
    The V-tail is less subject to damage because the mass of the stabs
    is close to the boom.  To make room for the gear in an f3e ship
    it is almost mandatory to put the elevator servo in the tail.
    This is why the T-tail without rudder control is so popular, the
    servo can be buried in the fin quite easily.
    
    To reduce stab damage on a T-tail, the boom must be very stiff,
    the stab must be constructed very strong and light and be as small
    as possible in surface area.  In fact the tiny stabs is the first
    thing one notices about an f3e ship.  This is the design used by
    all serious competitors.
    
    One needs to land an extremely low drag 25 oz/sq ft ship which has
    a wing prone to stalling at relatively high speeds without the
    benefit of flaps to really appreciate the design considerations
    and flying skills.
    
    If nothing else, my exploration of high speed electrics has built my
    confidence for flying(landing) anything out there.  Even a WWII model
    with a higher wingloading, but much more drag can't be much harder to
    land.  
    
                                                 Regards,
    
                                                 Jim

    Jim, Jim, Jim,,,
    
    It is not impossible; only extremely difficult. Try various
    combinations of battery pack config (eg. 2 rows of 4 and two on top,
    two rows of 5, 2 sets of 5 interconected, vertical vs horiz etc) before
    you give up. Any bury the rcvr as far aft in the tail as you can force
    it; push it on top of the rcvr battery (you are using 100mA battery
    right?). Make a cut and bury the S133 or KS10 towards the rear, make a
    temporary hatch to install with silicone and use for elevator-only. Use
    ZAP to close the hatch and finish smooth. Then to remove motor batt you
    only have to remove the switch and replace pack. I want through all
    these gyrations with the home made fuse here and, after deciding 10
    was impossible finally figured out a 14 cell 'turbo'
    arrangement...fooled the folks for a bit until they discovered the
    extra batteries.
    
    Yes, flying one of these slippery and fast ships has made me confident
    of flying most anything except the no take-off skills catch me whenever
    I revert to the Panic. Landings can be exciting without and computer
    radio but not impossible. The RG15 slows down pretty well if you keep
    the leading edge nicely rounded and are not tempted to make it sharp to
    make it fast... The problem then is to judge just how far these things
    will glide; always far longer then predicted so I always land too hot
    and sometimes then repair the tail or replace the wing bolts.
    
    Best of luck 'tinkering'
    and ciao, Ed

    Thanks for the encouragement Jim R. and Ed.  As past noter
    Terry Tombaugh would say - "It's a real character builder."
    
    Nothing I do to make this a 7-cell ship will prevent me from
    attempting to add the extra cells later, with the posiible
    exception of not burying the servos in the stab.  I am not
    comfortable with servos in the V-tail using the method
    suggested by Weston.  However if I were to compromise and
    allow the servo arm to protrude through the stab with an
    external control horn on the elevator?  You guys got me 
    thinking now.
    
    Question - How can one connect(solder) nicads end to end
    capable of handling 40 amps current draw?  I know the
    premade packs use heat shrink with welded tabs, but can
    these handle the high current draw?
    
                                              Regards,
    
                                              Jim
    
    
    

    Jim,
    
    I'd also like to encourage you to try and get the WACO done as the 10
    cell competitive ship it was meant to be. There must be ways to do it.
    
    One of the Elektroflug magazines has a nice article on soldering
    NiCads. I'll have it with me when I see you. I'm not able to describe
    it accurately enough in written English. I can see that custom tailored
    batteries might be the answer to your problem. The main tool you need
    is a STRONG soldering iron (not these wimpy ones for electronics).
    
    Best regards,
                    Hartmut

    Ciao Jim,
    
    Ok, so now we got ya' hooked.... Batteries are easy. As our German
    friend mentioned bet a good soldering iron; at least 60W.  If it comes
    with a pointy end take a hammer to it and flatten it out a bit. Then
    tin each end of each cell with (after taking some med sandpaper to the
    ends to get the copper to show a little and make tiny marks to hold the
    solder. Then cut some copper braid (like ground strap, about 1/4 in
    wide long enough to connect the cells side by side. Then solder + to -
    (of course) and then 'double bend' the connection so that the + and -
    ends of the cells touch. You now have 2 cells in line. Repeat as
    necessary. When you get what you need for config get some of the large
    shrink tube and cover your pack, heat with hair drier and you have a
    good battery pack, quick as Bobs your uncle...
    
    
    Buona fortuna (good luck)!
    
    Ciao, Ed

    RE: -1
    
    I will try this method.  If you get a cell too hot when soldering,
    and it "vents", will one know this has happened?   Is the cell 
    performance degraded?
    
    As Jim mentioned in an earlier note I certainly have talked up
    "poor man's F3E" an awful lot over the last year.  Two thousand +
    dollars into my "experiment", "poor man's F3E" is certainly an
    oxymoron.  Here is where the money was spent, and what I have
    learned:
                                                        
    Graupner Elektro Uhu(the original sin!)----------$90
    Astro 05/fai-------------------------------------$100
    Graupner Power switch 20-------------------------$55
    Aristo-craft charger-----------------------------$60
    7 cell 900 scr-----------------------------------$40
    Misc props and hardware--------------------------$20
                                                    ******
                                                    $365
    
    Robbe Arcus--------------------------------------$169
    Astro 015FAI-------------------------------------$120
    Graupner Power switch 40-------------------------$65
    10 cell 900 mah scr------------------------------$50
    2 Futaba S33 servos------------------------------$60
    Astro 110A peak detecting charger----------------$85
    Misc props and hardware--------------------------$50
    Graupner Ultra 900-------------------------------$227
                                                     *****
                                                     $826
                                            
    Robbe Calibra------------------------------------$149
    Keller 70/4--------------------------------------$190(Thanks Hartmut!)
    2 Jr 341's micro servos--------------------------$90
    RCD Micro 5 Channel RX---------------------------$80
    Astro 205 Speed controller-----------------------$135
    14 100 mah scr-----------------------------------$65
    Astro 112 charger--------------------------------$75
                                                    ******
                                                     $784
    
    WACO 10-550--------------------------------------$229
    
    
    Obviously the radio, servos, and receiver are not exclusive to
    f3e type aircraft, so they don't really count.
    
    What I have learned is:
    
    - If you can make composite fuselages, cut and bag wings, the cost
    of a high performance electric glider is cut by about 1/3.
    
    -You need to buy the infrastructure items- battery charger, micro
    servos, speed controller or on/off switch  and a computer radio is
    nice.  Do not scrimp on these items.
    
    -Astro FAI motors are half the cost of Keller and Graupner motors.
    They also are lower performance and the shafts of the 05 and 015
    bend ridiculously easy.
    
    -Robbe makes great kits, Weston's electrics are for the very
    serious only.
    
    -F3e type ships are a lot of fun, offering tremendous ability
    to grow in design, building, and flying -nothing boring here.
    
    
    I would start with a 10 cell ship, the performance is much higher
    than 7 cell with little additional cost.  The Robbe Calibra is an
    excellent kit offering a very flexible layout that can accomodate
    a large range of motors and battery combinations.  The Arcus may offer
    better thermal performance in a less flexible package.
    
    High performance glider experience is almost a prerequisite.  If you
    don't have this experience, the Graupner Elektro Uhu is a good
    starting place. 
    
    These ships offer in my view the best of both power flying(speed,
    erobatics,convenience) and gliding(quiet,elegant,beautiful designs,
    thermalling).
    
    I highly recommend it!
    
                                                     Regards,
    
                                                     Jim
    
    
    
    

    Jim,
    
    the method Ed described is basically what is explained in the
    Elektroflug mag. Now you might want to ask, why add the copper, it just
    adds weight and length if you are to solder + of cell 1 directly to -
    of cell 2.
    
    Well, if I remember the article correctly, you can omit the copper if
    you're very experienced in soldering and have the right tools. I tried
    that with a bunch of cells O put into the seattube of my bicycle for
    light in the winter (remaining 5 cells of a dying TX pack). I have to
    admit, I wouldn't want to hang a plane on that pack. My soldering iron
    (Weller pistol) was not hot enough to do the trick :-(
    
    I'll bring the article and you can check it out. Very good photos.
    
    You might want to try that with old cells. If the iron is really hot
    and has some heat capacity, the risk of overheating the cell is
    minimal. The temperatures they achieve during F3E type of flying are of
    different nature :-)
    
    And if you need to be creative regarding location, think about the
    paper rolls Multiplex offers to put in wings like the Fiesta for lead
    ballast. Maybe you can even put your cells into the wings? Or are they
    too thin for this?
    
    Reminds me of Ralf Decker: In his ten year old (but still fairly
    competitive) F3B plane NoName, he places round ballast (looking a lot
    like cells, but is in fact brass) behind the spoilers. He doesn't have
    to disassemble anything to ballast his ship.
    
    Best regards,
                  Hartmut
    

Jim - I notice you already have a 10 cell 900 mah pack.
If it isn't a SR battery pack - don't write off the 10 cells
in your new plane so quick.  The SR 900 mah cells are significantly
smaller in diameter that the SANYO cells.  The first time
I saw George Mills 900 mah pack I was shocked at the size.
My SR pack was significantly smaller and to my observation
much more powerful.

Anyway - just figure out what fits and call up Larry at SR and
give him the dimensions and he will ship you the best pack that
can be made - all welded together.  It will cost 30-50 percent
more but you will be glad you went SR.

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

    re: -1
    
    Kay,
    
       I hadn't thought about SR cells(as if I haven't spent enough
    already!).  At KRC last year, Larry gave his traditional 1 hr.
    talk about Nicad construction, care, and maintenance.
    
    He strongly advised against soldering nicads together, due to the
    likely possibilty of overheating the cells and causing them to 
    "vent".  His cells are constructed by six spot welded(instead of the
    usual 4 on Sanyo cells) tabs which are used for the interconnection.
    
    What I noticed was all the "pro's" of electric flight(Keith Shaw,
    Steve Neu, etc.) used Sanyo cells with solder braid connectors.
    
    When I assembled my first 10 cell pack from Sanyo cells with solder 
    tabs, the tabs burned off when I ran it with my Astro 015 FAI.
    This has not happened with solder wick connectors.
    
    I will look at the dimensions of the SR cells, they might due the
    trick.  
    
                                                    Thanks,
    
                                                    Jim

    I recently received a letter from Dave Durnford, editor of the British
    Electric Flight Association's quarterly newsletter. Among other things,
    he stated the following- "Germany has really gone 'big' on electrics,
    it has been reported that Graupner does not plan on making any more
    IC powered plane kits, intending to concentrate solely on electrics.
    Imagine Sig or Goldberg making that statement and you'll understand
    just how serious the Europeans are about electric flight and it's
    future."
    
    It will be interesting to see how "good" electric flight can get
    if major manufacturers shift their efforts in this direction.
    
                                                 Regards,
    
                                                 Jim

    I haven't heard that news before regarding Graupner, but it doesn't
    really surprise me. Please note that Graupner is by far the biggest R/C
    stuff manufacturer in Germany and probably Europe! This is really an
    important change. And other major suppliers go the same way. If you
    look at the really exciting news from Graupner, Multiplex, Simprop and
    Robbe, most of them are electric, some even solar (every one of them
    offers solar planes now) for at least 2 or 3 years in a row now. Sure,
    some nice gliders came out, too, but only very few IC planes. If you
    don't count the electrics you can convert to IC.... :-)
    
    I figure it's not the manufacturers pushing in that direction, they
    just do what the market demands. And the market is lots and lots of
    clubs losing their fields due to noise problems. In Germany, a field to
    be certified must be a mile away from any house or airport (1.5 km to
    be precise). Everything that is that far away is 'nature preservation
    area'. The only way to get a power field certified is to break the 1.5
    km rule and pay with noise restrictions even harder than the general
    ones. At our club field near my parents home, there is no power flying
    at all allowed all sunday afternoon (holidays as well). No restriction
    for gliders and electrics.
    
    Enjoy your power planes as long as you can...
    
    Best regards,
                  Hartmut

    Last night I reinstalled the Ultra 900 in the WACO fuselage.
    At the prodding of several noters, I will again try to see
    if I can get 10 cells into this thing.  It is looking promising
    by creating a very "customized" battery.  The servos will have
    to go in the stabs.
    
    Hartmut will be looking at the ship tomorrow night, so it will
    be nice to get a second opinion.
    
    I am getting excited about the WACO again, with the Ultra 900
    it should be impressive.  The WACO will weigh 15 oz. less than
    the ARCUS with the same motor/battery arrangement.  It should 
    have unlimited vertical!  We'll see.
    
                                             Regards,
    
                                             Jim

    Jim,
    
    last night I packed the stuff I want to show you. I found one item to
    get you hooked even more. At the CRRC glider contest, I found a $10
    gift certificate from SR batteries in my grab bag. If you want to get
    a customized SR battery, you can have it.
    
    I'm getting excited, too, that you're trying again to get it going as a
    10 cell ship. Have you considered using the Keller motor? Since it's
    THE 10 cell F3E motor, I'd assume it would be the perfect match to get
    you addicted to F3E forever :-)
    
    See you tomorrow,
                      Hartmut

    RE: -1
    
    Hartmut,
    
           I will let you judge the possibilities for yourself, as I will
    bring the motors, Bec/on/switch, receiver, batteries, etc.
    
    Frank Weston told me they had tested the ship once with a Keller 70/4
    and 14 cells.  When you see the ship, if you can figure out how they 
    got 14 cells in there- we'll both know.
    
    I am praying my prop shaft adapter comes today so I can try the Calibra
    over this 3 day weekend.  I have a feeling it won't though!
    
    What makes the installation of the equipment in the WACO tricky is
    getting the CG right.  Tonight I plan on inserting all the equipment
    where it will fit, taping the stabs on the boom and seeing where the
    CG falls.  This should tell me alot.
    
                                                     Regards,
    
                                                     Jim

    Just got off the phone wih Flite Lite Composites to get some questions
    answered about their 7-10 cell 60" SD8000 T-tail electric.
    The plane uses elevator only control with the servo mounted in the
    fin(of course the aileron servos are mounted in the wings).  The wing
    has a carbon fiber capped balsa spar.  The kit comes with the 
    aileron servo cavitities precut and the ailerons prerouted.  The
    plane has a canopy and is said to easily hold ten cells.  Wings
    are presheeted obechi. Cost- $175.  Sound like a great sport plane.
    Now I can't buy another plane this year because the Calibra was
    going to be my last!(maybe)
    
                                           Regards,
    
                                           Jim

Sounds like something to put on Santa's list 8^)

    I flew the Robbe Calibra over the weekend.  It was exciting, to
    say the least.  The Keller 70/4 on 14 cells with Freudenthaler
    10.5x6 prop provides excellent climb, especially considering the
    all up weight is 82 oz.  I am very happy with the motor, I can
    get three climbouts per charge.
    
    Now to the flying.  I have four flights on the ship in conditions
    that kept all but the most intrepid power flyers on the ground(windy).
    After my first climbout, I shut the motor off and the ship entered
    a relatively steep dive, which required a lot of up trim to correct.
    The ailerons were way too sensitive, even at 50%.  The first landing
    I applied spoilerons(both ailerons up) and was coming in ok until
    a gust caused a tip to drop, my aileron correction had little or no
    effect.  Result was a hard landing damaging the ever vulnerable T-
    tail mount.
    
    I have now set the radio up to provide 100% aileron in position 1
    and 35% in position 0 and most importantly added exponential aileron
    control at 100%(rather than linear).  Now when I am on final approach,
    I switch the dual rate aileron switch to position 1(100%), this allows
    meaningful aileron correction when using spoilerons.  Should have
    thought of this before!
    
    With the new programming the ship is much better to fly, the pitching
    problem still needs to be sorted out on a calm day so I can see what
    is really happening without the wind buffeting the ship around.
    
    Overall I am very pleased with the Calibra.  It is extremely fast
    and good looking.  The wing loading is 22 oz./sq. ft.  Landing this
    heavy, slippery ship without flaps is going to be a challenge
    that I must master.  It is currently 1 step ahead of me, if I can
    get enough flights in without a serious crash, my skills set will
    definitely improve.
    
                                                      Regards,
    
                                                      Jim  

    I flew the Calibra for the 5th time last night in calm conditions
    to try and sort out the trim which was difficult to do in the windy
    conditions last weekend.
    
    The dual rate/exponential setup is working well, the plane still 
    goes into a rather steep dive with elevator trim set neutral.
    
    The bad news is I broke the stab and elevator in half on the landing,
    which was not really to hard.  I am fabricating a new stab made from
    laminations of 1/16 balsa and 1.7 oz. kevlar.
    
    This ship needs to really be greased in on the landings to prevent
    damage to the T-Tail.
    
    The best solution would be a vacuum bagged foam stab, which I think
    would be light enough to negate the force which is breaking the balsa.
    
    
                                                              Regards,
    
                                                              Jim   

    Since ASTRO motors have a reputation of eating brushes (especially when
    used with high currents), I'd like to maybe get some spare brushes for
    my 2 ASTRO 05s.
    
    What would be a good place to look for them? Is Tower good on spare
    parts? Or is another mailorder/hobby shop better equipped to serve the
    small group of electric fans in this country? Or would you recommend to
    order with Astro directly? What kind of cost would you expect? I heard
    some bad experience from Ed Siegmann regarding spare parts from Astro
    directly. I'd prefer Tower because I'll probably have an order with
    them anyway. But if they'd put it on backorder, it doesn't help me
    since I'll be going home. What would you recommend?
    
    Best regards,
                  Hartmut
    
    

    Hartmut,
    	Tower is pretty good on spare parts.  I've never ordered spare
    brushes for Astro motors, but I have gotten engine parts with good
    success.  You could go directly to Astro as well.
    
    Charlie
    

    I doubt that Tower carries brushes (but it's a free 800 number to
    call and find out...).

    I bought some from Astro about 3-4 years ago for $8.00 per pair.
    (Price may be higher now??)

                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |            Happy Landings!
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|              - Dan Miner
     |_/      |___________|  |_________|  |
                      |       /           |     " The Earth needs more OZONE,
                      |      /                       not Castor Oil!! "    
                      |_____/

	I tried an experiment yesterday. I purchased a throw-away
camera and using elastic bands I fastened it to my PT-Electric
between the rear landing gear. I then fastened a micro servo 
to the landing gear (using elastics) so that the actuating arm
would press the button. Since the PT is a 3 channel I used the extra
channel to run the servo. This seemed to work pretty good and I can't 
wait till I get the pictures back. The use of elastics made it nice
since I didn't have to modify the structure of the plane. The only
problem was I had to land it each time I needed to wind the camera
for the next shot. I am using the motor setup I discribed earlier
in this note and it had plenty of power for the added weight of the
camera ( which weighed 1/4 pound ) and the extra servo. 


					Larry

    The annual KRC electric funfly was held Sept. 19-20 in Quakertown, Pa.
    The weather was good and the attendance was excellent.  Below is a
    summary of the highlights(I was only able to attend Saturday):
    
    -Keith Shaw flew his twin Astro 05, ducted fan, standoff scale
     Horten flying wing.  It was a spectacular performer, very fast
     good roll rate, good vertical performance.  A real crowd pleaser.
    
    -Steve Neu(finished 7th in this year's world F3E championship held in
     Holland) flew his f3e ship.  This ship was quite different
     than the one he used last year.  It was completely molded using
     rohacell, carbon, kevlar, and fiberglass.  Wingspan of 64" using
     a modified SD7003 airfoil.  The fuselage weighed 100 grams.  Power
     was an Astro 60 FAI on 27 1000 mah Sanyo SCR cells. Climb, speed,
     and glide ratio were unbelievable. 
    
    -Tony Fiore flew a 1/4 scale Mustang complete with 1/4 scale Robart
     retracts using the new prototype ASTR0 90 motor on 40 cells.  The
     ship flew very well, easily taking off from the grass and performing
     loops and rolls.  It was rumored to weigh 24 lbs!
    
    -Joe Beshar flew his electric converted Royal B-17.  He flew it much
     better this year.
    
    -Joe Utasi was finally able to ROG his Ligetti Stratos which flew very
     well once it was up.
    
    -Many very fast aerobatic pattern style electrics flew.
    
    -A factory sponsored pilot from Switzerland flew a Robbe Calibra "pro"
     using the new Robbe Keller 735/6 motor on 20 cells.  Very impressive.
     He also flew a RObbe Arcus using a Keller 35/6 on 10 cells.  This guy
     is a very experienced slope soarer who was able to fly very smooth,
     high speed inverted passes inches from the ground for 1/2 the length
     of the field ending with an inverted climbout!  He put on a great show
     of smooth, polished flying.  All the Arcus's Robbe had in their tent
     quickly sold after seeing what they could do in capable hands.
    
    -Many scale WWII designs with retracts and great finishes all flew
     very well.
    
    -More high speed aerobatic flying wings and pylon racers.
    
    -More ducted fans-all flew well.
    
    -Aeronaut Sunfly, Freudenthaler Surprise II, Flite lite 550, Waco 550
     Aeronaut Sinus high performance gliders all flew.  I was disappointed
     with the Waco 550 using the Astro 015 on 10 cells.
    
    **In summary, KRC is too overwhelming to do in one day.  I only flew 
      my Calibra once and still did not see everything else.  The size and
      performance of electrics just keeps getting better each year.  Larger
      motors and 20+ cells were very prevalent.  It is clear after
      attending this year's meet that it all can be done very well with
      electric power.
    
    
                                                         Regards,
    
                                                         Jim  

    In light of the American team's gold medal at the World F3E
    championships held in Holland this August, I thought I would
    provide some details of the ships flown by the U.S. team.
    
    I have this information as a result of examining the ship Steve
    Neu flew in the World Championship and speaking with him at the
    KRC funfly this year.
    
    The ships flown by Neu, Perrin, and Bridgeman(U.S. F3E team) were
    the same.  The wing is all molded using Rohacell, carbon fiber,
    carbon tow, and fiberglass.  The span dropped to 64 inches this year 
    with 475 sq. inches of area using a modified SD70003 airfoil.  Steve
    Neu made the wing mold.
    
    The fuselage also was molded using rohacell which resulted in a very
    stiff structure(no more "oilcanning") that weighed 100 grams.
    
    Steve said the SD7003 was not the fastest airfoil but turned very
    well.  Last year he was using the RG12A.  The team's strategy
    was to build a lighter plane this year which would climb better
    and turn better.  "The race is won in the turns not the staightaways"
    was Steve's comment.  The increased rate of climb offsets the
    greater sink rate of the smaller wing and higher wingloading.
    
    This ship flown by Jerry Bridgeman finished only 4 points off the
    world's best again, Rudolph Freudenthaler.
    
    With Joe Wurts and Daryl Perkins taking the 1st two places in this
    year's F3B Championship flying US designed and built planes and
    our gold medal win in F3E, it is evident that the USA is a true
    power in the world of high performance gliding.
    
    Congratulations to the team!
    
                                               Regards,
    
                                               Jim

    Congratulations from me as well! Interesting to hear that the USA is
    up there now. This triggers some real competition - I remember the
    times when European teams didn't take the US contestants into account.
    They didn't feel threatened at all. Maybe your guys took them by surprise
    this time. Great job!
    
    Now will this trigger some interest in the average US modeller to get
    into F3E/B type of flying? As Boris Becker triggered interest for
    Tennis and Bernhard Langer for Golf in Germany? I sure do hope to read
    more and more about hi-performance electric developments from USA (the
    land of cheap R/C equipment :-)).
    
    Best regards,
                      Hartmut

    I'd love to see one of these babies fly. At 64 inch span and 475 sq.
    inch area, this plane is not much bigger than a handlaunch. Is this the
    same one that runs a 27 cell pack? Whoa. Sounds like a challenging ship
    to fly.
    
    Dave
    

    RE: -1
    
    Dave,
    
        Most of these ships do use 27 cells.  The Hectoplatt motor
    from Switzerland is the acknowledged favorite.  The US team uses
    modified Astro 60 FAI motors.  With a thrust ratio as high as 2:1
    the climb is unbelievable(over 6000 ft. per minute).
    
    A single round of F3E includes a 3 minute distance event, immediately
    followed by a 5 minute duration event, so these planes must stay
    aloft for at least 8 minutes.  The typical F3E ship can climb to
    1000 ft. 6-7 times on 1000mah batteries.  The average speed in the
    distance event including 26 turns and 5-6 climbouts is 70 mph.
    
    The ships can fly inverted and roll continuously even during vertical
    climb.  I have been to the ducted fan meet held in Rome, NY and did
    not see anything that could touch the f3e ships in terms of efficiency.
    
    With wing loadings around 26 oz/sq ft. they are tricky to land.  The
    pros make it look easy, however.  I witnessed Steve Neu's ship
    actually thermalling this year at KRC.
    
    If you ever see one fly you will be amazed!!!!
    
                                          Regards,
    
                                          Jim

    I'm sure I would be amazed if I saw an electric grab sky at 6000 ft per
    minute! My only comparison is my Astro Challenger, which has 7- 900mA
    cells driving a geared cobalt 05. It's good for maybe 3 climbs to 500
    feet. Sounds down right anemic compared to the F3E designs.
    
    You mentioned you weren't very impressed with the performance of the
    WACO at the KRC fly. Is that the same model that you bought?
    
    Dave
    

    Re; -1
    
    Yes, unfortunately I was not very impressed with the WACO 550 I saw
    fly at KRC with an Astro 015 FAI on 10 cells.
    
    I am quite convinced the Astro 015 FAI is quite a bit less powerful
    than the equivalent 10 cell motors from Graupner(Ultra) and Keller.
    However, it is also half the cost of these motors in the USA.
    
    What I am learning as I remain active in this hobby is everyone(me
    included) has certain prejudices.  I think Frank Weston's hot button
    is light weight which is why I think he likes Astro motors so much(
    they are very light weight).  I own a Keller 70/4, An Ultra 900, and
    an Astro 015 FAI.  The Astro is certainly the least powerful motor,
    even when it's light weight is taken into account.  The WACO 550 I
    saw did not go vertical as his advertisement states.  It probably
    would with the Ultra and most certainly with the Keller.  In repeated
    conversations with Weston he has stated the superiority of the Astro
    motors over the Keller and the Graupner.
    
    Getting 10 cells into the Waco fuselage with the Keller motor would
    be an impressive challenge!  The Waco fuselage is ridiculously
    small.  I think Frank Weston has put too much emphasis on light weight
    and thermalling ability for his 10 cell f3e offering.  I don't care for
    the servos in the V-tail concept either.
    
    The Waco 550 was quite a floater for an F3e ship, but the fuselage 
    isn't big enough to weigh it down with a powerful motor and big
    1400 mah batteries which would improve the speed.
    
    Since there is no 10 cell F3E in America it seems unlikely that we
    can expect any competitve commercial offerings.  I give Weston credit
    for trying, but could not recommend the ship based on what I've seen
    and heard about it.
    
                                                Regards,
    
                                                Jim

After reading Jim Blum's reply last week about the lack of interest in 
electric, I felt kind of guilty(no offense Jim!!!)  You see, I bought a used
(and slightly abused!) Uhu several months ago. It needed some repairs, but 
they were done a couple of weeks after I bought it. I was supposed to go flying
(glow powered) at the CMRCM field yesterday, but plans changed I only with a
couple of hours to go flying. I looked at the Uhu and thought what the heck,  
why not go out and fly it. I needed to install another servo and the RX, so I
did that as the pack was charging. I ended up charging both of my packs(1200mA
and 900mA) before I left the house which took 45 minutes in total(leaving me
with a little over an hour to go flying.) I quickly packed up and headed down
to the Lancaster House(owned by DEC) which has a LARGE vacant building site
next to it. 

This was the first flight of the Uhu, so I didn't know what to expect for a
climb rate would be with my setup(Astro 05 cobalt and Graupner Powerswitch 20
and 7 cell 1200mA battery pack.) While not spectacular, I was still pleasantly 
surprised with the climb rate. With the power on, the nose of the Uhu was 
pointing up about 15 degrees and climbing. I let it climb until I could see the
plane start to stall and then feed some down in to pick up speed again. This
technique(???) seem to work well. I didn't time the climb, but in no time at 
all, I was at or above high start altitude.

I manage to get about a 20 minute flight with 2 and a half good climbs. This 
was with a battery pack that had been sitting around for some time( I 
discharged and charged it before I left the house.) I didn't even try to peak
charge it. I was psyched and had a blast on that flight! I caught a couple of 
small thermals and had some fun with loops, rolls, and inverted flight.

The next flight was almost the same, but only lasted about 12 minutes and had
two climb out runs(using 900mA pack.) I decided to pack it in after this 
flight, even though I could probably have squeezed in another. I went home with
a big smile on my face and won't hesitate to fly the Uhu again!

Now for some question about the Uhu. The fuse has had quite a bit of damage to
the wing hold down area. I've made repairs to it using some epoxy, ply, and
spruce spar stock(yeah I know WEIGHT!) It seems to be hold okay(didn't shed
the wings doing loops or pull outs from speed runs,) but it's an area of 
concern. Has anybody made repairs to these (plastic?) fuselages and have them
hold up? I was thinking of calling Hobby Lobby and see if they sold a 
replacement fuse for the Uhu. I also plan to build a smaller aileron equipped
wing(ala Graupner Chip.)  

-Lamar

    I'm not shure about the UHU fuse, my ASW24 fuse is kinda ABS. They
    strongly recommend using "Stabilit Expess", a kinda 2-components glue
    stuff that holds particular well on plastics. It's yellow and ugly, and
    a white hardener powder. Don't know if you can get this in US.
    
    Maybe epoxy works (it seems what you told it would). 
    
    H A R T M U T  ,do you hear this ?
    
    
    Bernd

Thanks for the advise Bernd on Stabilit Express. The stuff is sold by Hobby 
Lobby($9 - 1 ozs and $17.50 for 3 ozs.) I also found something called "UHU-Hart"
glue in the Hobby Lobby catalog. The catalog says this stuff is the "best 
selling model glue in Germany." The catalog states that "It slightly melts ABS
plasctics so it makes both a good glue bond and a "weld" on ABS parts..." This
stuff is $3.40 for a 1 ounce tube and $7.50 for a 4 ounce tube. Have either you
(Bernd) or Hartmut used this stuff?

I plan to do a lot of flying with the Uhu of the winter, so I should pick up a
tube of either UHU-Hart or Stabilit Express. Not that I'll need it mind you,
but just in case! :-) 

-Lamar

    
    Lamar,
    
    I used UHU Hart - long ago. The statement they make is true : it melts
    the stuff and bonds good. ABS to ABS is Okay. As I remember the stuff
    is not flexible at all. It's not two components. It shrinks when drying
    like white glue and smells like Acetone (it might contain that). Usually 
    you have to glue different materials and  therefore I'd recomment the 
    Stabilit Express. But $ 17.50 for 3 ounce sound very expensive.
    
    (Best selling model glue - I don't use it and don't know anybody using
     it anymore....Hmmmmmmm - yeah, 20 years ago, right !)
    
    
    Bernd
    

>    H A R T M U T  ,do you hear this ?

    No Ho, I'm reading! Do you have a terminal that does the reading for
    you? Sorry, it's one of these days...
    
    Lamar,
    
    yes I've been using different kinds of glue on my UHU. I just had a
    hard time to remember them all. That's why I didn't answer yet.
    
    I know both UHU-hart and Stabilit Express. As Bernd said before,
    Stabilit is a 2 component (I think Polyester, but am not quite sure).
    It's nice to work with since it gives you 20 minutes as opposed to 5
    minute epoxy and seems less critical regarding the mixture.
    
    UHU-hart is a single component and does not hold up comparably, but it
    does melt the plastic as advertised. I used it for the whole fuselage
    attachments (especially servo/battery board) without problem. It needs
    some area, though, to hold up well. The canopy hold-down piece fell off
    a few times, but can easily be reglued.
    
    Since I changed to a geared motor, I had to cut the canopy holddown
    plate in two pieces and make room for the motor in the middle. I'm not
    sure what I glued the two pieces with (small area/high load), but
    possibly Stabilit. It held up very well so far. These two are probably
    your best bets (Stabilit only when it comes to superior structural
    strength). Not sure about epoxy, maybe 30 minute stuff is fine. I'd
    stay away from the 5 minute stuff on the UHU plastic fuse.
    
    Where do you live, Lamar? Is Shrewsbury MA out of reach? I have both
    glues with me in my flight box. You could give them a try, and you
    might even be able to persuade me to leave them with you. Will we have
    the DECRCM meeting next week? Are you going?
    
    Another hint: Be careful with the UHU in the winter! I've been flying
    it a lot in the winter, and it's a very enjoyable plane, especially in
    that season. You can warm your hands on the batteries:-) :-). But the
    fuselage becomes brittle at freezing temperatures. I once broke the
    tail off cleanly by landing on a frozen acre (glide was better than
    expected, landed on icey meadow, jumped back up in the air (no
    deceleration on icey grass) and finally landed on a freshly ploughed
    hard frozen acre. Oh well... Also, last winter, I ruined a motor by
    landing on freshly fallen snow. The snow got into the air openings in
    the front of the fuse until it was full. I didn't care since I figured
    the motor was hot and would steam it off, anyway. After the motor
    sucked some ice into the collector, it had an idle current (no prop) of
    about 55 A... Both events are reported with more detail elsewhere in
    this file.
    
    If you take some care, it's a great plane for the winter. Have fun, and
    let me know regarding the glue.
    
    Best regards,
                   Hartmut

    My experience with gluing Uhu fuselages is:
    
    1) PFM(Innovative Model Products) works very well for bonding ply
       parts(bulkheads, motormounts, tailplanes, etc) to the Uhu fuselage.
       It is somewhate flexible, hence it does not break loose on hard 
       landings.
    
    2) Stabilit Express works well and cures to a very hard finish.  I
       use it to glue strips of carbon fiber to the inside of the fuselage
       to repair cracks/breaks.  I would recommend PFM over Stabilit for
       gluing empennage and empennage mounts to the fuselage.  
    
    3) Epoxy- does not work adhere well.
    
    4) CA- does not adhere well
    
    5) UHU Hart- not as good as PFM or Stabilit Express.
    
    AS a side comment, the UHU was what got me excited about electrics.
    It's performance is far below a Robbe Arcus which occassionally sells
    for as low as $99.  The Arcus has much better energy retention(cleaner)
    and thermals better.  I would highly recommend it as a 10 cell
    electric.
    
                                                    Regards,
    
                                                    Jim
    
    
                                                    

Jim and Hartmut,

Thanks for the replies. I have a tube of PFM and love the stuff. I've used it
to mount the servos in several of my hand launch gliders and on a Gremlin(ya
know one of them greasy noisy things! :-)  ) and it's worked great. Since most 
of the previous damage to this fuse is around the wing hold down area, I think 
the Stabilt Express glue would be the best choice(maybe I will take you up on
the offer Hartmut!) The nice thing about electric flying(for me at least) is 
that I can bring my family along and not have my youngest daughter(who's almost 
3) scared to death because of the engine noise. Loud noise really bothers her
quite a bit. It's also nice to keep her away from high starts because she loves 
to chase the chute down( which she then tries to strech it out ---OUCH!)

Regarding the Arcus, who carries it in the US? Just something to keep in mind
when it comes time to retire the Uhu. I was really impressed(and several others
were as well) when I saw Hartmut fly the Fesita at Al Ryder's contest at the
begining of October. A guy(Art Fariah -sp?) that work's at Tom's Hobby would 
love to have one of these after seeing Hartmut's fly.  

-Lamar

    Lamar,
    	Try Hobby Lobby. They often advertise Robbe products.
    
    (615) 373-1444
    
    
    
    
    Dan

    Hobby Lobby does not sell Robbe products, at least they do not show
    any in their catalogs.  I have purchased all three of my Robbe Kits
    directly from Robbe International in New Jersey.  I can provide the
    phone # tomorrow.  I have seen some of their power plane kits in
    a local Hobby Shop, but never any of their glider kits.
    
    The Arcus would work with an Astro 05 on 7 cells, but the climb would
    be anemic.  I would recommend an Astro 015 FAI on 10 cells.  This
    really is the minimum config which would do the design justice.
    
    In fact, I really do not know of any commercially available glider
    designs that offer "exciting" performance on 7 cells.  The UHU
    comes close.  I think the flying weight would have to be in the
    mid 30 oz. range to get impressive climb with Astro 05 on 7 cells.
    If one used the Graupner "New Match" design as a model, it might be
    possible to get a really high performance 7 cell glider.  A skinny,
    light, composite fuselage with a 7% 60" inch wing, might do the trick
    (ala the New Match).  Using the latest high tech composites it should
    be possible to produce this ship.
    
                                                 Regards,
    
                                                 Jim

I remeber seeing a Robbe ad in an issue of Model Airplane News and can look
it up if the need arises. I'm stuck with the 05/7cell setup(unless I see an
15 at the CRRC auction tonight!) for budget reasons. If I went with more than
a 7 cell pack, I'd need to get a new charger(I have an Astro 115.) 

Maybe I should try and scracth build a fuse. I've got a foam wing cutter and a 
vacuum bagging setup and can do my own wings. I've also got access to all my 
brother-in-law wood working tools(he's a finish carpenter.) Geez! I keep saying
that I'll try making my own fuse for glider, but always come up with an excuse
not to. Maybe it's time to push my building limits some more and just do it!

-Lamar

    Lamar,
    
         I am afraid you will have to scratch build if you want
    a hot 7 cell glider.  Good luck if you attempt the project!
    
                                                 Regards,
    
                                                 Jim

    ...or wait for the New Match. Maybe they are out when I get home. I'll
    let you know.
    
    Best regards,
                  Hartmut

    Re: -1
    
    I talked with Hobby Lobby this summer, and they said the New Match
    could be special ordered for $200.  I think the Flite Lite Composites
    Falcon 400 which I have spoken of in the past, offers better value for
    $175, and is readily available. 
    
    
                                                  Regards,
    
                                                  Jim

    Recently I sent Ed Siegmann the lastest Astro prices offered by
    Hobby Barn(see latest RCM).  They offer the 25 and 40 for a little over
    $100(add about $20 for a gear box).  
    
    What I want to bring up is the "trend" in electrics is rapidly moving
    away from the 05, 7 cell format which has dominated for years and 
    given electric a bad name I might add(direct drive 7 cell ferrites
    on .40 size trainer planes).
    
    This shift was obvious at this year's KRC, where 05 size planes were
    nearing the minority.  The reduced prices and better performance
    available from the larger motors has rapidly redefined electric flight.
    
    The Jomar SM-4 speed controller can handle up to 24 cells and is a
    bargain at $100.
    
    A question I pose to the electric critics- How many non-05 sized
    electrics have you seen fly?
    
                                               Regards,
    
                                               Jim 

An the Tekin high Voltage 828 I just bought from Tower was $90. As the name 
implies, it handles 8 to 28 cells.

I hope to see a non 05 fly in the next week 8^)

    Last week at my club field, one of the older members informed me
    he was building a SKYVOLT(MA electric columnist Bob Kopski's design).
    He is going to us a geared Astro 015 on 12 cells with a 3 speed(low-
    med-high) controller.  
    
    This guy is a bad flyer(downwind takeoffs followed by steep, hang it
    on the prop climbouts) and a bad lander(frequently downwind, often
    noses over and cartwheels).  The Skyvolt uses a symmetrical wing
    (NACA2412) and is built light and adequately strong.  
    
    He told me he thinks he will get vertical climb with this setup.
    He is also a very heavy builder.  His Goldberg Extra 300 required
    3 lbs of ballast in the nose to balance!
    
    I am predicting a tip stall on the initial(probably downwind) takeoff.
    If this ominous prediction does not occur, I am sure the SKYVOLT will
    not withstand the bad landings.
    
    This man has flown RC for 20 years and I certainly will not insult
    him by recommending a flight plan and "checking" his plane(especially)
    for weight.  
    
    I am expecting the inevitable conclusion- "Electrics don't fly worth
    SHI*".  He will claim - "I have been flying RC for twenty years and
    have never seen a plane snap like that".  
    
    This identical scenario(different ARF electric plane) occured at the
    previous club I belonged to.
    
    This fellow's overpowered planes and robust(and heavy) construction
    have allowed him to develop very sloppy flying(particularly takeoff
    and landing) skills.  
    
    I'll be interested to see what actually transpires.
    
    
                                              Regards,
    
                                              Jim

        Re:                      <<< Note 387.619 by UNYEM::BLUMJ >>>

                I didn't know he was a member of your club too!
        
        :-)
        
        Anker

I went flying at lunch today with Jim, Dave Walter, and Dick Bissen up at a
small field in Westford and flew my (beat up) Uhu. I wanted to give Jim some
more incentive on his electric project. Nothing spectacular with the Uhu
flying, but show him I was with him on his electric adventure. I only got a 
couple of flights in, but was happy with the motor run times. I had several 
climb outs with the 1200mA pack, but only did a couple with the 900mA pack. The
reason for "only a couple" on the 900mA pack was that I ejected the canopy in
mid flight(right as I got into a boomer thermal.) Even without the canopy(and
all that drag!), I was till going up!!! Sooo, I stayed with the thermal for a
while before I brought the Uhu. When I landed, I still had about a minutes worth
of motor run left on the pack(maybe one more climb out???) 

Luckily Jim was standing beside me when the canopy flew off and tracked it down 
for me(Thanks!!) Flying was nice way to get out and enjoy a beautiful Autumn
day in New England!

-Lamar  

Yep, a little more incentive. I'm hoping to try out the 25 in SOMETHING next 
week. I've got a full plate of things to do on saturday but sunday should be 
all mine in the shop. Got to give that charger a good workout to see if it's 
what I want to get 8^)

After considering my options I ended up sticking to the original plan and put 
the gear into the H-Ray. Considering the effort it took, I think it was a 
reasonable decision. I learned a lot about 10 pounds of "stuff" in a 5 pound 
bag. How small is that Waco?

I got it all together and it weighs more than I wanted (didn't do a final 
weighing yet) Seems about 5 pounds (maybe it's just the bag).

I ran it some and the speed controller is real nice. I get about 3.5 minutes 
of flat out thrust before it starts to drop off appreciably and then it 
continues to turn to about the 6 minute point. The battery in my tach was 
dead so I don't know what the speeds were but it should pull it along quite 
well. With the big trainer wing I should be able to extend the flight some 
while unpowered and it should be a reasonable combination for the time being
(until I get the Ninja fuselage built)

Well, today was the day. I went out with the H-Ray to give it a try. We've had 
high winds all week so I threatened to go slope soaring and they calmed right 
down. Lamar and others came down to see it and I asked Lamar to do the initial 
launch honors. We ran a range check and tried it with the engine on (a beater 
plane with an Attack radio) and found no problems. We parked at the upwind end 
of the field so we ended up walking the entire length to have plenty of room
(and avoid the guys fertilizing). Lamar gave it a good heave (you don't "toss" 
a 5 pound plane) and it flew out and then started to climb. All it needed was
a single click of rudder trim and it flew fine. The climb wasn't dramatic but 
it went right up and managed to fly through the sun twice. I tried a power off 
loop but didn't dive enough first so I had to blip on the power to bring it over 
the top. I did another with the power on and... let's just not claim that this 
is an aerobatic ship 8^) I did a few fly-bys and the plane glides like the brick 
hiding inside (two pounds of old 1400maH batteries from 15 years ago) but I 
managed three decent climbs and had power at the end to do a "maintaining" go
around. I let the plane sink on landing and flaired low but the belly slide
caused it to turn sideways and it caught the prop and "bent" a tip. Pretty 
typical for a no gear Gremlin style landing with an APC prop.

Final thoughts:

I didn't expect a lot from this combination and was pleasantly surprised.I will
build the Ninja fuselage next and should be able to get the weight down to about
4 pounds. I actually think that an electric Gremlin is attainable... 

Now where'd Jimmy hide his R/C car battery packs 8^)

I started to go through the different keyword directories on props but none of 
the electric entries are keyworded for "props" I then did a dir/title=prop 
387.* and found .362, .522, and .554. I remember Jim Blum doing a study of 
various prop combinations and thrust but couldn't find it (one of the notes 
listed talks about the Hobby Lobby table)

I'd like to figure out what is a reasonable prop to run on my Astro 25 in the 
Ninja I'm about to build. I'd rather do it without buying lots of similar props 
and having a "fly-off". Is there a good way to calculate what prop (and style) 
to use to maximize performance? My DVM only goes to 10 amps so I really can't 
monitor "draw". I'm also wondering if the Scimitar style APC props I use/enjoy 
on my gas planes are a good choice for my electric. My entire decision process 
was that the manual for the old Astro 25 stated 9k RPM with a 9-7 prop so I 
went out and bought 2 APC 9-7s. I broke one at lunch, what should I try next?

I went out again today since the weatherman was wrong about the rain and got 
in two more flights with the Electric H-Ray. Lamar came out with his UHU and 
we flew together. The UHU outclimbed the H-Ray without any problem. Last night 
I heard/noticed some bearing noise in the engine and my feeling is that I saw 
the effects of it today. The climb was best described as lumbering (there was 
no wind today while there was some yesterday) and the engine seemed to get
hotter than expected. I did get in two flights during the session and managed 
to belly land without any damage to the plane/prop but I'm really feeling I 
need to get something lighter built. I've been told to make myself scarce 
tomorrow night while my kids have a halloween party so I'll head down to the 
shop (which is right below the party room) and listen and build.

Can you get replacement bearings easily or does it usually require sending 
the motor back to Astro? I probably have a machinist friend that can do the 
bearings but if Astro sells them I'd lean towards them. This engine has never 
been run for very long and I never did the 1 hour on a motorcycle battery 
run in. Could these be the symptoms that would cause?

As Jim mentioned in the previous note, I went out with the Uhu today. I charged
one of my packs(1200mA) pack with Hartmut charger and got a full volt more in
voltage capacity(10.5 using my Astro 115 vs 11.5 using ULTRA Duo.) I was able
to get 4 good climb outs, before I ran out of juice for the motor.  The more
I fly this Uhu, the more I like it. Now, if I can find someway to get a cobalt
15.......:-) Yup, I'm hooked!

-Lamar

It's going to be an electric winter 8^) I forgot to mention that on the 
second flight (after Lamar had to leave) I managed a pretty decent rudder 
roll with an appropriate amount of down elevator fed in inverted and was 
surprised that the plane did it so well.

Lamar's not the only one hooked 8^)

Seems the noise I heard yesterday was due to one of the permanent magnets 
coming loose. I broke a brush in disassembling the motor last night. I'll 
be attempting repairs over the weekend but I don't expect the motor to be 
the same in the future. I'll be reattaching the magnets (they all came loose 
while disassembling the engine) with a high temperature epoxy. There are
enough traces to be able to determine where the magnets go so I can get 
things back approximately. I've resigned myself to pricing a new motor in 
case of the worst. The good news is that the new motor will be better than 
the old one which got me rehooked (I'm looking at the Cobalt 25 and 40)

    Wow!!!
    
    I've been out since Monday noon and am surprised how many electric
    entries I find today. Look, Jim Blum, it's working, IT'S WORKING!!!
    
    Jim (Reith), just one point to make you aware of when you try to reglue
    the magnets, maybe you are aware of it: The effectivity of an electric
    motor very much depends on having the airgap of the magnetic circuit as
    small as possible.This means, you have to allow for manufacturing
    tolerances, but the designer will try to keep the magnet as close to
    the rotor as possible. If there are parts of the magnets remaining on
    the stator, make sure you remove all loose particles and place the 
    magnet correctly and exactly where it belongs. If you have some magnetic 
    dust where it doesn't belong, it might lead to the magnet interfering 
    with the rotor. Then, you only have a piece of junk... 
    
    From my experience (with our disk drive magnets), the only way to clean
    a ferromagnetic surface from magnetic particles is strong adhesive
    tape. Apply it without bubbles and peel it off again and hope the
    magnetic dust is on the tape. I'd recommend to do this even if the
    surfaces of steel stator and magnet look clean.
    
    BTW, I'm not sure whether I said that before, but that's the main point
    with the new robbe pro motors: Since magnets can't get much stronger,
    they've reduced tolerances. They are using an extremely small airgap
    (Keller was already famous for a small airgap). One way to achieve this
    is using round magnet shells instead of rectangular magnet strips. They
    also machine (grind) the magnets to thickness tolerances that are not
    achievable otherwise. This way, they reduced the resistance in their
    magnetic circuit and improved the motor.
    
    Best regards,
                  Hartmut

Well, the Astro 25 will be taking a break from flying for a while. Friday night
I managed to glue the magnets back in place and replace the brushes with a set 
I got at Hobby USA. Reinstalling the brushes was a 2 hour ordeal due to the way
they keep the tension. The bearings are bad/going bad and have moved down the
shaft and need to be "pulled". My machinist friend will do that for me but it 
will be a couple of weeks before I get everything back together right. I did
run the engine with the brushes on the edge of the commutator (the problem the 
bearing shift causes) and I was able to get 6500 rpm out of it. This will 
improve with the new bearings and better brush contact (and wear in)

The good news is that Tower has the Astro cobalt 40 for $120 in stock 8^)

    Just got back from a week's vacation, if you could call it that -
    mostly wallpapering and painting!  I did manage to get a few nice
    Calibra flights, however.  In fact I so enjoy flying this ship that
    I will not be building the hurricane and twin Pucara I was planning
    for this winter!  The efficiency, speed, awesome climb, and tremendous
    L/D makes the power ships seem so boring.  Yesterday I was flying in
    15 mph wind, I flew my routine downwind base leg waaaaaaay downwind
    and turned back into the wind at an altitude of maybe 15-20 feet.
    Two club members comment- "Jim come back, you'll never make the field"
    As usual, my landing was long, approaching the end of the field.  You
    have top experience the penetration and L/D of one of these ships to
    believe it!
    
    Jim Reith - I have read the old Astro Ferrite motors are far inferior
    to the new cobalt's.  A new 25 or 40 can be had from Hobby Barn for
    about $107.  You need to really decide what type of flying you want
    to do, this will determine the best motor for your needs.  I would
    recommend a geared motor if you want to put it into a trainer type
    plane(ie airfoil of 12% or more).  If you are going ahead with the
    Ninja a direct drive 015 FAI would probably be a good choice(approx
    $85 from Hobby Barn).  Getting 10 cells into the Ninja should be
    much easier than 16 - consider the layout of the equipment and CG.
    Two things to beware of however- Astro 05 and 015 shafts bend very
    easily and built up fuselages w/o landing gear can be easily damaged
    on hard landings.
    
    I think the biggest decision you need to make is whether you want
    a hot electric glider or a plane which has the motor running
    constantly.  The motor and prop will depend on your decision.  
    
    Let us know what you decide!
    
                                              Regards,
    
                                              Jim
    

    Welcome back, Jim. I was wondering where you'd been.
    
    The cobalt 40 will be for a larger aerobatic plane. I'll probably put
    the 25 into a modified Ninja fuselage one it gets repaired. I intend to
    get into performance electrics in the future. I'm not sure a cobalt 15
    is on my purchase list currently. I'll probably stay with the larger
    engines for now. I'll give Hobby Barn a call for a current quote.
    
    Thanks for the info and incentive

    RE: -1
    
    Jim,
    
       Electric Aerobatics(F3?) is flown as an ancillary event at the
    world F3E championships.  The ships are typically 20-30 cells with
    very powerful motors, light, clean, folding props, no landing gear.
    
    These ships must be low drag to get the duration and vertical needed
    for impressive aerobatics.  The one's I have seen pictures of are
    composite construction.
    
    To pull this off successfully will require some planning and maybe
    a somewhat different flying style.  The IC pattern style ships I have
    seen tend to have thick airfoils, big empennage, and motors with 
    enough power to "hang it on the prop".  The high drag of these designs
    will reduce the run-time of an electric and limit it's slow vertical
    performance.  
    
    An impressive electric pattern ship will probably need a thinner
    airfoil and fly at a higher speed than it's IC counterpart. A number
    of commercial ships are manufactured in Germany.  The few American
    attempts(Douglas Electric Breeze, Electric Hots, Elektro Streak)
    are 7 cell adaptions of gliders or other IC designs.
    
    As with most other high performance electric projects - "roll your
    own" seems to be the way to go, unless you have a lot of money for
    the German offerings.
    
    I highly recommend composite construction and NO LANDING GEAR.  An
    SD6060 airfoil of about 50-60" span might be a good starting point.
    I would use an Astro 40 FAI and prop for about 28 amps which would
    yield 3 minutes of strong flight with 1400 mah cells(probably a
    9x7 folding prop).  
    
    I can send you pictures of successful German designs from a magazine
    if you like.  If Hartmut is still in town he has a tremendous 
    collection of magzines which would probably have some examples.
    
    The project will be challenging to build and fly, but done right
    should prove highly satisfactory.  The sound of a high performance
    electric motor in a high speed dive has got to be heard, it's really
    neat!
    
    Keep us posted.
    
                                               Regards,
    
                                               Jim
    

Thanks for the tips. Yes, Hartmut is still in town and I expect to see him 
sometime this week. The plane is for having fun with and just going out and 
putting in a good flight. I'll leave the competing for the gliders. My 
point was that I really want something a little more out of the ordinary. I 
don't want a lumbering electric glider, I'm not really interested in a trainer
and I don't really want a plane which spits cells out of the breach like spent 
bullet casings (short run time). I'd like a plane similar to the Electrostreaks
I've seen but with the added stability of a bigger plane. I'm open to 
suggestions and a scratch built plane is likely/preferred. Thin strong wings are 
easy from my glider experience with core cutting and bagging so the design is 
more the issue.

On the other hand, an electric Gremlin is quite likely

I should(as long as it's not backordered!) be able to provide a report on
the Douglas Aircraft Electric Breeze kit in the nrar future. I'll be ordering 
one from Tower this week. From the review article(in Model Airplane News) on
the Electric Breeze, it sounds like it will be a fun ship to fly! I can hardly
wait!!

-Lamar

Thanks for the pointer to the Hobby Barn ad. They're $15 cheaper than Tower.

Now, if what I want is reasonable power for a reasonable amount of time rather 
than a flat out screaming climb for 60 seconds, do I want the non-FAI or FAI 
version? I'm looking for an engine that will have good power but will be 
efficient at 2/3rds throttle to tool around the sky. Tower didn't offer me this
decision 8^)

    Re: -1
    
    Jim,
    
       My suggestions are based on observations of approximately
    400 different electrics fly(2 years of KRC) and reading everything
    readily available about electric flight(most of which is in foreign
    publications).
    
    The design criteria I am suggesting will probably not result in a
    "world class airplane", but will provide a very respectable electric
    powered airplane, that will surprise most people with it's performance.
    
    The trend in electrics is moving away from the 05 powered 7 cell 
    configuration that has dominated for at least a decade.  Few IC
    builders would place an .049-.10 engine on a plane with a 50" wingspan
    and expect much performance, so I don't know why people keep trying
    to power planes of this size or larger on 7 cells.  The fact that
    planes like the Elektro Streak and Electric Breeze fly as well as they
    do is a tribute to their efficient design.
    
    I was assuming you were looking for better performance than the 
    Elektro Streak, electric hots, etc.  With your core cutting and
    vacuum bagging skills this should be relatively easy to do.
    
    The most important observation I have made(and experienced) with 
    hot electrics - YOU HAVE TO KNOW HOW TO LAND!!!!!!!!!!!!!!!!!!!!!
    The high wing loading and low drag requires better than average
    skills to "grease it in".
    
    I think the FAI wind motor would be the way to go if you want IC
    style vertical and 100mph capability.  If this is not your desire,
    I think the geared motors would work better.  You MUST match the
    motor to the airframe for optimal results.  This is why electric
    has such a bad name- direct drive motors in draggy airframes!!!
    
    This project has great potential particularly with 25-40 size
    motors(16-20 cells).  The important thing is to decide what
    you really want out of the plane and design it that way.
    
    
                                                   Regards,
    
                                                   Jim   

Well, the vertical and 100MPH sound real good but I guess I'm just reluctant 
to only "do it" for 3 minutes per charge. I'm still not sure what the 
difference is between the FAI and stock windings. Does FAI run better flat 
out or can it be tempered with a speed controller to extend a flight a bit?
Does FAI have to be propped to high amperage to run efficiently?

I haven't done the research that I know you have which is why I'm asking in 
this forum. What are the design criteria to achieve this unbelievable electric 
performance with say a FAI cobalt 40 on 20 cells?

    Re: -2
    
    In my rambling in the last note I neglected to fully address your
    question- "to FAI or not to FAI".  
    
    The FAI motor simply has less turns on the armature and hence draws
    more current.  This alone does not determine final current draw.
    The prop, input voltage, and drag of the airframe also must be
    considered.  All things being equal the FAI motor will draw more
    current and spin an equivalent prop faster than the sport wind,
    hence run time is decreased.  By optimizing the prop for the intended
    purpose of the plane and using the speed controller, acceptably
    long flights can be achieved.
    
    The "standard" in electric flight circles is 5 minutes.  Some high
    performance or large elctrics fail to achieve this.  The chart below
    was published by Keith Shaw who is highly knowledgeable and very
    experienced in all phases of electric flight:
    
    Watts/lb.        Application
    *********        ***********
      100            F3A style aerobatics, impressive vertical, high speed
      
     50-60           realistic WWII fighter performance, good aerobatics
    
     40              mild aerobatics, usually need to dive to complete a
                     loop, realistic WWII bomber performance  
    
    
     So if you prop an FAI 40 for 28 amps with 20 volts at the motor
    terminals - 28 x 20 = 560 watts.  
    
    The motor, prop, spinner, batteries, servos, rx etc should weigh
    no more than 60 oz.  So if you can build a 30 oz airframe you
    would get a power loading of 100 watts/lb.  If this airframe were
    low drag, this would be a high performance machine.
    
    Now is where we get sober- if this airframe has 500 sq. inches
    of wing we are talking about a wing loading of approx. 26 oz/ft.
    While this number would not daunt the average flyer of a high
    drag IC ship, it will be a hot lander in electric dress because
    I am assuming we're using a thin airfoil and folding prop with
    no landing gear(this is where your "crow" capabilities help).
    
    Dropping to 25 FAI on 16 cells drops the wing loading to 23 oz./ft
    and the power loading goes to 90watts/lb.
    
    Just food for thought- heck this is fun maybe I'll build one!
    
    
                                               Regards,
    
                                               Jim

    Boy I'm full of Advice/shi* today.  I want to recount an interesting
    event I witnessed Sunday at my club.
    
    One of the better flyers of a Zimpro(I think) Dalotel powered by
    a Super Tigre 90 had his first dead stick that I have witnessed.
    The glide angle or lack there of was nothing short of astonishing!
    This plane glided like a 2x4, I mean it was incedible how quickly
    it dropped.  This landing did not result in any damage.
    
    The next flight the engine died again and the Dalo did it's glide
    like a rock thing resulting in  the landing gear being totally
    ripped from the plane!
    
    This guy has flown this plane rather impressively at the field for the
    last 2 years.  My assessment is the Super Tigre is a very high
    performance engine, because this plane on its own can't fly worth
    a darn.  I think the glide ratio is about 4 to 1, maybe.
    
    As a measure of airframe efficiency I would like to see a plane like
    this come across the field in steep dive and cut the engine to idle
    and pull out to see how it carries the speed.  I bet after a full
    power dive it would struggle to gain 75 feet!
    
    
                                                 Regards,
    
                                                 Jim

I like the numbers so far and I agree that those weights are achievable. I 
assume we're talking an airfoil like the RG15 or SD6060 so we can maximize 
penetration. What are we talking for aspect ratio? High wing, low wing, 
mid-wing? Why can't you imbed a single wheel in the fuselage ala 1/2A pylon 
or glider?

Crow... are we talking something that you can put enough servos into so you 
can do this or is it a wasted effort?

From your chart, Can I assume a plane that meets the 100 watts per pound 
would fit into the "good" aerobatics at 3/4 throttle?

I'm confused on batteries. What is the size cell used in these applications?
Where's the breakeven point between weight and capacity? Should I be looking 
at 900, 1200, or 1700 cells at the WRAMS show?

Landing hot will be a challenge but it doesn't have to be a gating factor.

    You touched a nerve here John!! (Note the smiley face please! :-)
    
    I campaigned a Zimpro Dalotel as a pattern plane this past year. I had
    a YS120 for power, and guesstimate that the plane weighed in at around
    8 pounds. I had flaps fitted, and found that in no wind conditions I
    needed them to get the plane slowed down and on the runway at our club
    field, otherwise it would float on and on. In fact I have lost the
    engine when the plane was out at dust spec range with perhaps 100' of
    altitude and made it back to the field with no problem. 
    
    Mine was the Dalotel 850, 69" span, 850 sq/in wing area. Can you supply
    more info on the other Dalotel?  :-)

    Jim,
    
       The RG15 would not make a good aerobatic airfoil, the undercamber
    which gives it the excellent L/D would fight you in axial rolls.
    T-tails are also a definite no-no for an aerobatic plane.  A low
    wing is desirable just as in IC design for a quick roll rate, but
    many German designs I have seen use a mid wing config.
    
    The SD6060 would be a better choice if aerobatics is what you are
    primarily interested in.  The new 1700 SCR's are supposed to be
    the same size and weight as the 1400 mah(1.8 oz).  The only place
    I have seen them advertised is Weston Aerodesign and they are
    twice as expensive as the 1400 mah Sanyos.  The price will be coming
    down I'm sure.  The 1400 mah Sanyos at $3.50 apiece seem the best
    value at the moment.  The 900mah and 1200 mah Sanyos are no longer
    available.
    
    
    Re: -1
    
    
    First off the Dalotel I mentioned weighs 12 lbs. which may account
    for its rapid rate of descent.  Secondly, under power it is a very
    nice flying pattern ship.  I find it hard to believe it would have
    great L/D because of the large fuselage, fat wing, muffler, prop,
    landing gear, large empennage, large control horns, exposed linkages,
    large cowl, low aspect ratio wing, etc.  The ship certainly is not
    designed for great L/D and as such one would not expect it to glide
    that well.  It is designed for fast rolls, straight tracking, good
    inverted flight, knife edge capability, etc.  It appears to do these
    things very well.  My Calibra electric glider rolls like crap(slow
    and barrels badly), flys inverted with much up elevator, and is 
    generally a real lousy pattern ship when compared with the
    thoroughbreds.  This should surprise no one as it has been designed
    with different performance criteria in mind.
    
    It was not my intention to insult the abilities of the Dalotel as a
    power plane, only as a glider.  This is only fair as the performance of
    my gliders and electrics is constantly being compared to power ships.
    
    My ships glide well and perform relatively poor aerobatics, I suspect
    your ships perform good aerobatics and glide relatively poorly.  
    All design criteria would point to this conclusion.
    
    
                                                     Regards,
    
                                                     Jim
    
    
    

Thanks, Jim. Guess I'm having a hard time getting away from the glider stuff.

Gotta run tonight but tomorrow night I'll be seeing Hartmut with a long look 
into his magazines.

Thanks again,

Jim

P.S. Dan's Dalo is about 8.5 pounds and he had to add flaps because he kept 
overshooting the field. It's amazing to see it float right on past. It's a 
very clean ship. Hard to imagine that we're talking the same ship. Guess it 
has to do with carrying 4 pounds of ballast in the one at your field.

    Jim B,
    
    In the past you have supported the position that electric ships, when
    properly designed, can compete with IC planes. But the electric pattern
    ship that you propose here has no landing gear. That pretty much
    eliminates it from serious contention in any IC pattern contest. Does
    this mean that electrics will always have their own version of pattern
    competition because of their inherent limitations?
    
    Dave
    

    Jim,
    
    	I have to agree with Dan. I've seen 2 Dalotel's fly regularly and
    the major problem with each is getting them DOWN. One of them even
    weighs in at about 10 pounds yet it just floats and floats and floats.
    Some of the major pattern planes in use today have what's basically
    a Dalotel wing.
    
    	I'd have to guess there's something else wrong here. Although the
    Zimpro Dalotel is basically an ARF, there's still alot of mistakes
    that can be hidden while under power. That warp in the wing can be
    over come with aileron trim. The wing incidence that's way too much
    or way to little can be over come with up or down elevator trim. A
    way too forward CG can be over come with elevator trim and up thrust
    but take away the power and the thing will nose over and head for
    the ground with very mushy and very LIMITED elevator response.
    
    Na, the Dalotel is a great flying airplane. There's something wrong
    with the one you describe.
    
    Steve
    
    

    Jim,
    
    	One other thought. If this person is using a S. T. 90 for power,
    he probably has the same Dalotel as Dan Snow. If his weighs 12
    pounds, it's about 4 pounds OVERWEIGHT. That probably gives it a
    wing loading equal to a 747. In this case, what you say makes
    sense. Under power, there is enough lift created for the plane to
    fly normally. Once dead stick however,  there is no more lift being
    generated by the power plant. With what I suspect is an excessive
    wing loading, the plane has no choice but to fall out of the sky.
    
    If it is a 12 pound Dalotel, my guess is it's WAY over weight and
    doesn't stand a chance without power.
    
    Steve 

    Rereading my original note recounting the Dalotel dead stick
    incident, I see my unintentional tone is combatitive.  Let me
    clear a couple things up.  I saw the Dalo owner at our club
    meeting last night and asked him about the ship.  I was mistaken,
    he has a Zimpro EXTRA 230, the Dalotel was scratch built from
    plans, with built up wing. 
    
    I do not believe an electric powered ship will ever pose any
    serious threat(with or without landing gear) to an IC powered
    F3A style ship.  The electric motors simply do not have the
    power to move an F3A airframe in fashion, not to mention the
    weight of the batteries.  Electric aerobatics is a separate
    event flown every other year the week of the F3E world championship.
    I'm sure Chip Hyde won't be putting an Astro 60 in the Jekyll anytime
    soon, and would most likely finish last in every contest if he did!
    
    In a sense I feel stupid for drawing comparisons between gliders
    and pattern ships.  Obviously what makes one fly well, would have
    the opposite effect on the other.  The pattern ships designs are 
    optimized to do pattern things well at the expense of other things,
    same for gliders.  To illustrate this point can you imagine entering
    a pattern contest with .61 IC engine mounted on a glider or launching
    a pattern ship with a high start?  
    
    Part of this "comparing" comes because many of my fellow club members
    refer to my Arcus and Calibra as "pattern gliders".  This is given
    as a compliment because they are avid pattern enthusiasts.  They
    have never seen a glider roll, fly inverted, fly 100mph, and climb
    under electric power at a rate equal to IC ships.  While these gliders
    are capable of some simple aerobatics, they simply cannot compete with
    the thoroubred pattern ships.  So refering to them as "pattern gliders"
    is a way of saying they are high performance because at my club the
    pattern designs are the highest performance ships(speed, climb, roll
    rate, etc).
    
    Let's face it the two designs are at opposite ends of the spectrum
    and fly entirely differently.  My off-base comment did have one 
    positive effect however, Eric actually entered a reply in this
    conference!
    
    I will refrain from further inappropriate IC-electric comparisons
    in the future.
    
                                                         Regards,
    
                                                         Jim  

    
    Jim,
    	Who took your tone as combative? I sure didn't, note the reference
    I put in about smiley faces! :-)  I enjoy reading your notes, even
    though electric "ain't my thing right now", and my intent was to poke a
    bit of fun your way.
    
    I grant you Steve was being rather analytical about it, but in any case
    you have nothing to apologize for! You made a statement based on your
    information, nothing wrong with that!
    
    
    Dan
    
    (BTW-When did Eric reply? I missed it!)   :-)

Eric replied to John 8^) 8^) 8^)

Back to designing this "pattern glider"...

So, if I stick to the 100 watts per pound rule and have a 30 oz ship to play 
with, what's the problem? A 5-6' wingspan with a 7" average chord should be 
light enough and then a fuselage to fit the batteries and such into should be 
quite doable. Looks like a largish slope style ship is probably the mental 
image I'm seeing. Your airfoil suggestions simply allow me to picture it 
flying either side up 8^)

     I just realized that my reply, 287.643, was addressed to "John" Blum.
    
    Sorry about that Jim! :-)

    Dan,
    
    Wether it's an Extra 230 or Dalotel, I was not aware that being
    analytical and theorizing why this guys plane might be flying like
    a garbage can when the engine quits was the same as being combative
    or why it would cause anyone to feel they might need to appologize
    for anything.
    
    Could you possibly explain what you meant by that????????