Conference vmszoo::rc

    I just love the OS 1.08. It does not need any conversion to pull a
    Telemaster. The engine is VERY reliable and will pull any model glider
    that I have seen.
    
    Regards,
    
    E - who put one in a Panic!, True I have witnesss. It out pulled my
    Enya 120R and idled like a watch.

    RE: -1
    
    Robin Lehman's other towplane is a Senior Telemaster with an O.S. 1.08
    which we will be using this weekend(weather permitting), so I will get
    a chance to see how it works.
    
    Will the 1.08 spin a 16" prop?
    
    Any opinions on diesels?
    
    Why do people use chainsaw motors when they appear to be twice as heavy
    and develop less hp than glow engines?
    
    Thanks,
    
    Jim

>    Why do people use chainsaw motors when they appear to be twice as heavy
>    and develop less hp than glow engines?

They run on gasoline and have spark plugs.

Sooooooooooo

They run on gasoline and have spark plugs.

But Sooooooooo

They run on gasoline and have spark plugs.
They run and run and run and run.

NEVER a dead stick,
NEVER lose an engine on take off,
NEVER burn out a glow plug,
NEVER...

I don't have one but those who have switched to
gas never seem to come back.

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

    the one and only reason that I have not got a petrol/gas engine is that
    the fuel is dangerous.
    
    Glow fuel is relatively inert on a hot day in a very hot car interior.
    Gasoline is much more volatile and ignites with the slightest spark.
    Plus it stinks, or more politely put, "The fuel management issues do not
    lend themselves to comfortable odour managment".
    
    E.

    ANother big reason.  Gas is cheap.  The chain saw gang flies for one 
    tenth the money us alcies spend.
    
    But I'm with Eric.  Gasoline is much more dangerous, so I've avoided
    using it so far.
    
    -Joe

    O.K. two points have been made:
    
    (+) - gas engines are cheaper to operate
    
    (-) - gasoline is more dangerous than glow fuel
    
    
    Perusing the Tower catalog I find(for example):
    
                         ST .90           O.S. 1.08        Zenoah G-23/38  
    
                         ******           *********        **************
    
    PRICE                $200              $290             $250/$268
    WEIGHT(oz)           20.3              26.5             41/70 
    Power(oz)            2.4               3.0              1.6/2.2
    
    
    
    It appears that the gas engines are about twice as heavy and half
    as powerful as mid size glo engines.
    
    Unless you like the sound of the gas engine, why are they being
    purchased?
    
    Kay has mentioned that they are more reliable.
    
    Are there any other reasons?
    
    Charlie - why did you opt for a G-38 on you Hots?
    
    There has to be something I am missing here.
    
    Is it possible that the gas engines have a lot more low end torque than
    the glo engine(spin a bigger prop)?
    
    Thanks,
    
    Jim  
    
    

    If memory serves, Eric had a somewhat lengthy conversation with the
    guy from Davis Diesel at the Willmington show. Most of the conversion
    revolved around the conversion of an OS1.08 engine to diesel operation.
    It was a cheap conversion (somewhere around $60 bucks) and the
    performance was rather impressive if you believe the guys video.
    
    Maybe Eric can elaborate more, but I would suggest calling Davis Diesel
    and asking about it. Just be prepared for a long phone call because
    you'll never get the guy to shutup. 8^)

    What about Super Tiger 2500 or 3000. I think the size is 1.5 and 1.8.
    They are 2 cycle, lots of power and less expensive than other models.
    Just a thought....
    
    Dennis
    

    RE: -1
    
    I have considered these.  I was hoping for a little more input from
    experienced engine users.
    
    
    Thanks,
    
    Jim
    

    They're both pretty good engines. (BTW there is a 2000 and 2500). I
    have played with and run several of them. Solid and reliable.
    
    It is a personal choice issue but you can go with Webra 120, OS120 and
    1.08, ST2000-3500 and not really go wrong.
    
    On the Gas side I know a lot less.
    
    E.

Yeah, on the GAS side, you need to follow Charlie to the WRAMS show 8^)

    OH! they woke up in the cheap seats I see!

    I must concur with Eric, the O.S. 1.08 is a real nice runing and
    powerful motor.  I was impressed with the slow idle ability and
    reasonable noise level.  It is a little pricey compared with the 
    Super Tigre engines.
    
    The ST 3000 claims the same power(3.0 hp) as the O.S. 1.08 but
    weighs 25 oz. more (20.6 vs. 45.2 oz.) an is $30 cheaper.
    
    Which engine would be the best for the Senior Telemaster tow
    plane?  RELIABILITY and easy starting are paramount - I'm no 
    engine wizard!
    
    
    Thanks,
    
    Jim

    Gas engines are heavier and less powerful than glow.  It's the fuel and
    the intended design of the engines.  The chainsaw engines have heavy
    flywheels and big heavy bearings.  They are reliable and very cheap to
    run.  You save at least $20 every time you burn a gallon of gas because
    you would have burned more than two gallons of glow fuel in the same
    amount of flight time.  My G-38 runs over 20 minutes on 16 oz of gas. 
    Since the engine is heavier, you do need to beef up a Telemaster type
    plane to use it.  It will come out very nose heavy if you don't shorten
    the nose.  The other problem is the size of the firewall required to
    hold the beast.  Rubber isolation mounts will cure the vibration
    problem.
    
    Charlie
    

    Jim, it looks like you have reached the point were you have all the
    data and now its a matter of personal choice. Picking one engine over
    another at this point for how it starts may depend on the user. Myself
    I find that OS engines seems to start a little easier than Super
    Tigers. That may be just my way of starting the engine that makes it
    appear so. Just one note, I was told that the ST 3000 has a new carb
    from the ST 2500 and works better. My son just got the ST 3000 for that
    reason. Good luck with what ever you decide.
    
    Dennis
    

    Dennis,
    
          I actually remained very confused about the engine possibilities
    for this project.  All the engines I have mentioned will probably work,
    but I would like to get the best one for the job.
    
    The manufacturers specifications, other than weight, do not seem to
    be particularly useful for predicting performance.  We have towed
    the same gliders the past two weeks with the same tow plane(Senior
    Telemaster).  The only difference is one towplane has an O.S. 160
    with a 16x7 prop, and the other towplane has an O.S. 1.08 with a
    15x8 prop.  The 1.08 weighs 20 oz and is rated 3 hp while the
    160 weighs 39 oz and is rated at 2hp.
    
    I would expect the performance of 1.08 to be better because it is
    1/3 less weight and 1/3 more power.  However, I observered the opposite
    to be true - the OS160 got the off the ground with the glider in
    1/2 the distance of the 1.08 and climbed quicker.
    
    Does this make sense?
    
    It appears there is more to engine performance than hp.
    
    Wish someone could shed some light on these issues.
    
    
    Regards,
    
    Jim

    RE.16
    
    Now its getting interesting. If you could perform the same test again
    using the same size props on both engines then you might have a better
    comparison. Too many varibles here. Keeps use updated if you can. I
    would like to know.
    
    Dennis
    

    Dennis,
    
          I just read note 1302 and all the replies and learned a lot.
    It is nice to read about some actual experiences with these big
    engines, plus see some RPM/Prop combination numbers.
    
    I think the best thing for me to do is to pick an engine that one
    of the local club experts is familiar with, that way I can get
    some help if I have problems(however, not many guys are flying
    big engines .60 two stroke - 1.2 four stroke being the norm).
    
    After reading 1302, I realize that we have really lost some valuable
    resources from this conference.  It is a shame.
    
    
    Regards,
    
    Jim

    Jim,
    
    What wingspan is the Telemaster??  If it's the 12 foot one I would put
    a Zenoah G-38 on it.  I have a Zenoah G-38 on an 87" Cunningham Triple
    Play and it is delightful to run and operate.
    
    Its cheaper to buy, cheaper to run, plenty powerful and easy to start. 
    I have an O.S. 3500 BGX that I'm converting to gas because after I
    bought it I learned that it would burn a gallon of glo fuel in about 30
    minutes of flying!  Expensive!!
    
    I would also strongly recommend rubber mounting the engine regardless
    of what you install.  The punishment you spare the airframe results in
    less maintenance and more flying.
    
    For what its worth I've never met a person more sold on Davis Diesel
    conversions than the owner.  I suppose thats logical but if you talk to
    the guy you'll find his opinions border on overbearing.
    
    Let us know what you decide.
    
    Will

    Will,
    
        The Senior Telemaster I am building will have a 95" wingspan.
    The primary consideration is not how it will fly in "standalone"
    configuration, but how it will fly with up to 10 lbs. of glider
    strapped to its wing or in tow.
    
    Re: fuel consumption
    
    I was amazed that kevin ladd reported in 1302 that his Webra Bully 
    used 3 oz. fuel per minute!  That would work out to be about 6-10
    oz. fuel per glider tow.
    
    Does the G-38 vibrate quite badly?
    
    What prop are you using with it?
    
    Thanks,
    
    Jim
    

    I have been running a G-38 for three years and it is great.  Vibration
    is more than small 2-strokes but no more than a 120 4-stroke.  It is
    easy to start and I haven't touched the needle in two years.  Weight is
    the major disadvantage of this engine.  I agree that rubber mounting is
    a good idea no matter what engine you choose to use.
    
    Charlie
    

                       -< NEWS items from rec.models.rc >-

After reading about some of the engine woes posted by readers of this
newsgroup lately, I thought it apt to post something that could prove very
useful.

This is taken (without permission) directly from the May 1994 issue of
_Hanger Talk_, the newsletter of the Cholla Choppers Model Airplane Club,
of Tucson, Arizona:

	The Gobbenflecker Files

	by Dr. Herman (Ace) Gobbenflecker III


		The Combustion Process

   Here at the Gobbenflecker Institute for Advanced Miniature Engine
   Studies, we have just completed the most extensive study of the
   combustion process in the Internal Combustion Engine. Although the
   science of combustion is one of the most complicated, and intricate
   subjects in mechanics, we have endeavored to present the subject to
   you, the general modeling public, in a form understandable to laymen.
   The subject has been covered for large internal combustion engines many
   times over, but very little has been done on the small model engine,
   and we therefore have filled this gap.

   The process begins with the compression of the fuel mixture in the
   cylinder, which condenses the air/fuel molecules at the rate of vapor
   exchange ratio, causing in effect, a Plotilla zone splatter. I know
   what you are thinking: a Plotilla zone splatter? Yes, the very same
   effect we find in the Spineherd plasma field, during osteration. This
   surprised us also, and caused us to rethink the combustion process over
   again. What we discovered was that the menseration of the Alcohol-Nitro
   molecules was directly related to the faceration of the flame front,
   from which the zone splatter is a by product.

   After compression of the gases, the ignition occurs giving rise to an
   increase in the temperature inversion, which in itself creates a
   thermo-bellium flux which depletes the molecule count to approximately
   .09592 MIPS per centimeter. I am sure that you see the importance of
   this, as far as scavaging of the exhaust residue during collation is
   concerned!!  For those of you not familiar with the collation process,
   let me explain its process. As the exhaust residue is beneated to
   sub-normal flow, due to thermo-bellium flux, it turbulates to a state
   of collaxial bentination, sometimes called, curvation. This process -
   collation, helps in the process of scavaging during the exhaust cycle.

   Toward the end of the ignition cycle, and just before the opening of
   the exhaust port, the combustion process has declined to a stratoforic
   state, that is; almost total quentitle retention of the central force
   vector, which we all know is vital to the output of the engine. More
   races have been lost because of the loss of the above force, than any
   other factor, including losing the propellor because of inadequate
   tightening of the prop nut!! Amazing I know, but very true!!

   Speaking of the central force vector, let me clear up a couple of
   misconceptions concerning this little understood phenomena. First of
   all, it is not true that the interdelusion process has anything to do
   with stratoforic states, let alone the quentile retention of the
   central force vector. You see, as the combustion process takes place,
   the vector itself is totally masked by the flame front interaction with
   the Ternally wave movement, and is neutralized, in effect. In
   conclusion, let me state that the central force vector is not, and
   never has been a terrorist group within the AMA. Where this rumor came
   from, I cannot comprehend even remotely!!!

So, there it is! And it explains a lot, doesn't it? Including precisely
WHY those engines have been flaming out and lagging in power so
unexpectedly.

Hope this helps!

L.
_____________________________________________________________________________
                                    | Larry E. Cunningham          |   
             ____                   | %Physical Science Laboratory |  _~~_
   |        | ___\          /~~~|   | New Mexico State University  | (O)(-)
  _:_______|/'(..)`\_______/  | |   | Las Cruces, NM USA 88003     |  /..\
 <_|``````  \__~~__/  USAF ___|_|   | [email protected]           |   ==
   :\_____(=========,(*),--\__|_/   |----------------------------------------
   |       \       /---'            |"Yeh, Buddy..                   
            | (*) /  Mustangs       | I've got your COMPUTER!        
            |____/   Forever        | Right HERE!!"           (computer THIS!)
____________________________________|________________________________________
Opinions expressed here are CORRECT, and all mine, not PSLs and not NMSUs..
Do NOT use the term FAT around me. I'm NOT fat. I'm gravitationally challenged.



++++++++++++++++++++++ The full NEWS header follows +++++++++++++++++++++++++++
News Article 27499
Path: nntpd.lkg.dec.com!jac.zko.dec.com!crl.dec.com!crl.dec.com!decwrl!ames!elroy.jpl.nasa.gov!sdd.hp.com!news.cs.indiana.edu!lynx.unm.edu!dns1.NMSU.Edu!opus!larry
From: [email protected] (Evil Engineer Doin' It The Cowboy Way)
Newsgroups: rec.models.rc
Subject: Understanding engine problems..
Date: 19 May 94 11:09:36
Organization: New Mexico State University, MetaPhysical Science Laboratory
Lines: 86
Distribution: world
Message-ID: <[email protected]>
NNTP-Posting-Host: summit.nmsu.edu

    I use an 18/6-10 prop.  I could tow a glider with mine with no problem.
    
    The vibration presents no problem but I do use rubber mounts to reduce
    airframe and radio wear and tear.
    
    24 ounces of fuel will last 30 minutes at full throttle, 45 minutes
    taking it easy.
    
    Regards,
    
    Will

    Just to update those who have provided advice in this topic, I have
    spoken with more local gas flyers and have come to a decision.
    
    Throwing out the question at my field resulted in quite a bit of
    heated discussion and disagreement about a number of things
    regarding the power, care, maintenance and feeding of gas engines,
    4-stroke glow and 2-stroke glow.
    
    The bottom line - no one I have spoken to has anything but good things
    to say about the O.S. 1.08.  All agreed that you cannot go wrong with 
    this engine.   Some felt gas engines were good for the job but did
    mention things like RX interference and starting difficulties.
    Others felt a 1.2 fourstroke was the way to go , but then the relative
    complexity vs. a 2-stroke came up.
    
    In the end the O.S. 1.08 seemed like the best compromise of power,
    weight, easy starting, repairability and local knowledge.
    
    Purchase is pending TSFO announcements.
    
    Thanks to all for your inputs.
    
    BTW - the ST 2500 owned by a club member spins an 18-8 prop @ 7000 RPM.
    The owner said if he had it to do over he would go with the O.S. 1.08.
    
    
    Regards,
    
    Jim
    

    Well as I wait to see if I get TSFO'D I can still mull over engine
    possibilities for my future towplane.
    
    At this point the O.S. 1.08 is the one to beat, however a couple of
    advertisements have recently caught my eye and I am hoping to get a
    little more info.
    
    Specifically the Irvine 1.20 2 cycle ABC looks interesting.  The
    advertising claims it runs very well on no or low nitro.  Will
    spin a large prop and is quiet.
    
    Any opinions on Irvine?
    
    What are the advantges/disadvantages of ringed(O.S.) versus
    ABC(Irvine)?
    
    Is the use of nitro adviseable for my application(glider towing)?
    
    Again the published specs seem to favor the O.S. in terms of
    rated horsepower and weight.
    
    Any help appreciated.
    
    
    Thanks,
    
    Jim

    I don't have any experience with Irvine but a ringed engine is more
    forgiving to carb tuning than an ABC motor.  One lean run on an ABC motor
    can ruin the piston/cylinder clearance.  I think O.S is the standard by
    which all others are measured.  They cost a bit more but the
    convenience of a trouble free motor is more than worth it over the life
    of the plane.
    
    Will

    I'd go with the OS 1.08 from my experience.  You don't need much nitro
    in larger engines.  You could run 5 or 10%.  In cold weather, some
    nitro is useful to aid starting and idle.  I do not own a 1.08 but I've
    seen them run and they are very well behaved.
    
    Charlie
    

    To further this discussion...
    
    On the subject of potential interference I read that the Rx and Bat
    should be kept 12" or more away from the engine. 
    
    Why would the battery have to so located ? I have a currecnt
    installation where I have to put the battery just behind the firewall.
    The plane came out a little tail heavy.
    
    I presume that the placement of servos near the engine is not a problem
    or am I incorrect here ?
    
    I will probably shield the cable to the plug. Another question... OK
    the shield is connected to the engine casing, if one has a closed loop
    system is it worth or proper to earth these to the engine also ? Will
    it reduce any potential interference ?
    
    As you can see I am a little lost with petrol or in American gas !
    
    But just bringing a plane and Tx beats glo requirements.
    
    Regards,
    
    Alt-E.

    This is not a problem unless you're talking an ignition engine.  With a
    glow engine, I have often put the nicad right against the firewall with
    the RX right behind it.  
    	With ignition, you want to keep the radio as far as possible from
    the engine and ignition module.  The best setup is NO METAL comes
    through the firewall.  I use a nylon throttle cable on my G-38.  If you
    use a kill switch, put it in front of the firewall and keep the wires
    as short as possible.  I have seen plenty of problems with ignition
    engines interfering with the radio.  Most are caused by long leads to
    the kill switch.  
    	Most engines use a plastic throttle arm - which is a good thing to
    keep any metal-metal vibration from affecting the radio.  I had a plane
    that used to act up when I put the ni-starter on the plug - just when I
    made contact.  Make sure that a metal throttle cable does not vibrate
    against any metal engine parts.  The throttle cable can act like an
    antenna.
    	With an ignition engine, I would not put the servos near the engine
    because the servo wiring can pick up ignition noise and transfer it to
    the receiver.
    	Again, the Kill switch is quite often a source of problems,
    especially with a magnito ignition.  The voltage spikes at the kill
    switch are up in the hundred volt range when the engine is running. 
    This is less of a problem with an electronic ignition.
    
    Charlie
    

    Thanks Charlie. My kill switch may need to be reworked as it is a bit
    back, maybe 4 inches from the back of the engine mount.  The engine is
    a Zenoah 45. 
    
    I don't have much choice in locating the throttle and rudder
    servo, they are probably 4-6" behind the engine. Whereas the battery is
    at the firewall. The rx is well back.
    
    Apart from improving the kill switch location what can I do to improve
    or reduce any potential interference ? Is shielding enough ?
    
    Regards,
    
    Eric.

    Can you go with a nylon throttle linkage?  I used weed trimmer line for
    mine and it works great.  (I don't use a kill switch)  I don't have a
    kill switch on my other engines so I don't feel I need it.  I have my
    throttle servo set up to kill the engine.  I realize that some people
    would insist on a kill switch on a spark ignition engine, but you have
    to turn the engine over with authority to get a spark with the magnito
    on a G-38.  I have a spring starter because it's almost impossible to
    spin it fast enough by hand propping.  Therefor, you can turn the prop
    slowly to prime it without the plug firing.
    
    I'm not saying a kill switch isn't a good idea, but I would rather have
    ultimate radio reliability than risk bringing the ignition signals back
    past the firewall with a kill switch wire.  My radio range checks just
    as well with the engine running as when it's stopped.  That's the check
    for ignition noise.
    
    Charlie
    

    Well I moved the kill switch forward to reside just beside the engine.
    I originally did not want another hole in the cowl but I placed it so
    it is accessable via one of the holes cut for allowing the air to cool
    the engine.
    
    I am going to shield the plug lead just as a safety precaution. 
    
    My carb cable is the inner of a golden rod, with a thin piece of brass
    tube inside it to prevent flexing. And yes it is insulated from any
    metal to metal contact with the clevis. Hopefully the heat will not
    have an adverse effect on it, we will find out. 
    
    Another question that I have is on the carb on the Z 45, it would
    appear to make no difference in rotating it 180 degrees, making it
    easier to get at the throttle linkage. Can this be done without having
    any effect etc ?
    
    All I have to do now is to put some lead in the nose and make a
    tailwheel bracket and the basic airplane is finished. I was annoyed as
    the plane came out tail heavy. I had pushed the engine back by using a
    prop extension. I had thought that it would have been nose heavy which
    is easier to deal with. Anyway I have to put about 6+ oz of lead as far
    forward as possible. I will cast the lead and mount it on brackets just
    above the inverted engine. 
    
    Regards,
    
    Eric.

    Teacher, I have a question, ....
    
    Seriously. Does one have to cut a hole in a cowl to allow air to the
    carb ? I have heard rumblings on the air intake noise, air-flow and I am
    wondering should I cut a hole or leave it as it is. With no hole the
    air will flow in the front of the cowl etc. 
    
    While I have my hand up... 
    
    On smoke systems. On a Zenoah 45 std silencer where is the best place
    to tap and pump in the smoke fuel ? I am ignorant of what is inside the
    silencer. I have seen photographs of a y piece (one-way value) placed
    in the crankcase line which pressurises the smoke fuel tank and hence
    pumps the fuel. 
    
    Eric.

    Well I started up the Z45 yesterday. My right arm is about to fall off,
    what an effort ! We eventually got it running and the power is unreal
    to say the least. It could all be in the technique of swinging the prop
    correctly or else the low & high needles are not correctly set. We are
    going to have another try tonight.
    
    Alt-E. 

    Well you guys must be having a great 4th of july ! It is quiet in here.
    
    So I discovered that the carb on the 45 can't be rotated 180 degrees
    last night (This is because of the pressure feed to the carb). Although
    the engine will start it is very difficult. So I rotated it back and
    made up a throttle linkage, and when I have enough strength I will try
    to start it again. I am zapped of energy trying to start it. In fact I
    have either fractured my left index finger or sprained it badly. Being
    a little over energetic my hand continued from the swing into the ground
    and gave my index finger a good old bend in the wrond direction ! It
    has swollen up and is about twice the size it normally is. Left hand is
    out and my right arm aches so drinking and lifting pints is difficult
    8-). The lads said I would be swiping pints of the bar table ! So it's
    back to the drawing board and we will have another go on thursday
    evening. As one can appreciate this is not the kind of engine one would
    start on ones own. 
    
    Oh 'ye will have to forgive the typo's if there are any - this ain't
    easy 8-).
    
    E.
    
    Regards,
    
    Eric.
    
    

    My 4th of July was pretty good but my 5th is suffering from Newcastle
    Brown Ale. Made a mistake in going to an ex-pat viewing of the USA vs
    Brazil game. He had an endless supply of my long lost friend, more
    affectionately known as Neu-wky - short for the atom splitting version.
    :-)
    
    Flew Sunday and Monday though. :-) :-) The YS91 is now beginning to
    sing. I am getting 10k with and APC 13 x 11. The vertical is very
    acceptable and the noise is around 93 db.
    
    
    Regards,
    
    Eric-over-here.
    
                                             

    There is a spring for the Z45 that makes starting one a two or three
    flip, spring powered affair.  The Z38's will hand start without a
    problem but I'm told the Z23 and Z45 are a real bear to hand start.
    
    Will

    OR... for a mere $249 you could get the FEMA onboard engine starter
    and start the motor with the flip of a switch from your transmitter!

    I have seen the Mick Reeves, geared, starter attachment in action. It
    handles these gas jobbies with ease. It uses a regular 12v model
    airplane starter motor and might be worth a look.
    
    Also gas engines love to be primed. Lighter-fuel etc. makes them fire up
    first time.
    
    I use 120's, and now the YS91. Under NO circumstances will I hand flip
    these motors. They hurt even when they don't fire.
    
    Regards,
    
    E.
                                                         

    I seem to have had better luck starting the engine. I was told how to
    start it by hitting the prop while it is in the 12 noon position (the
    prop being mounted at 10 o'clock, with piston at TDC). Still takes a
    bit of time and one definitely needs very well insulated gloves, to
    cushion your hand/fingers when hitting the prop. I might go for the
    starter attachment, so I can get maintain the guarantee on my hand 8-).
    
    The plane had its maiden flight on Sunday morning. A little un-eventful
    as is the norm with a first flight of a new plane. The Z45 had no problem
    hauling the 15 lb plane around. Of note the engine dropped off power in
    a vertical climb. Am I correct in saying that this may be due to the
    change in air pressure to the carb ? I heard that a trumpet attachment
    is used to reduce this, and also a pipe soldered to the hole in the top
    plate of the carb. On landing the plane tipped over and the prop
    suffered, being split. Can one use non-wooden props on the beasts ?
    After all appart from the high torque, they are running at fairly low
    rpm, in the 5000-7000+ range.
    
    Eric.

    Eric,
    	I have the spring starter on my G-28 and I highly recommend it.  It
    is very difficult to spin the prop fast enough to get a spark out of
    the standard magnito.  Check the gap on yours (to the flywheel) and
    make the gap as small as possible.  This improves the spark and makes
    it fire at a lower RPM.  I have heard of problems with a cowled in carb
    on these engines.  Mixture can vary due to air pressure fluctuations
    inside the cowl.  Seems to me that you can cure it by adding an
    extension tube to the air pressure sensor hole on the carb. (walbro)
    
    Charlie
    

    As the building of my towplane progresses, I have continued to research
    engine possibilities.
    
    I have decided to go with a 2 stroke glow engine.  I will probably use
    an O.S. 1.08, A Webra 1.2, a Moki 1.5 or a ST 2500.
    
    All these engines come highly recommended it seems by folks "in the
    know".  They all cost within $50 of one another.
    
    I have decided to let weight be the gating factor of my final choice.
    I will complete the airframe with servos/battery and place the 24 oz.
    fuel tank over the CG.  I will then proceed to add weight to the engine
    mount until the proper CG is achieved.
    
    The engine that is closest to the firewall weight will be the one I
    purchase.  The OS represents the low end at 26 oz. with the ST at
    the high end at 42 oz.  This will prevent adding large amounts of
    nose/tailweight to achieve proper balance.
    
    Is this backward logic(stupid?) or a good way to choose an engine?
    

    When I was completing my CAP 231 with the Zenoah 45 I had to put about
    16 oz of lead at the nose. I hate adding lead but when I discovered the
    power from the engine my fears were gone. Power is an understatement.
    After flying it I feel that I could reduce it quite a bit, having
    thought the CG was a bit too forward. Now I can experiment. 
    
    Regards,
    
    Eric, who-is-on-vacation-for-the-next-few-days.

    Jim,
    	I would not go about it that way.  I like to have the engine first
    and then arrange the "stuff" to achieve correct balance.  The Nicad is
    usually enough weight to affect the balance greatly by moving it's
    position.  I have some planes with the nicad right at the firewall and
    some with it 8 inches behind the trailing edge.  If you build a good
    design and use the recommended engine, it will usually come out close
    enough at balance to adjust it with the Nicad.  If you add much more
    engine weight, shorten the nose a little to compensate.  I shortened
    the nose on my Ultra-Hots to improve the balance with a G-38.  I pretty
    much just guessed at how much to shorten it, but you could do a simple
    balance calculation based on the recommended and desired motor weight.
    Pick the engine size for your application and choose brands based on
    reliability.  An engine failure can cost you a plane (or two) so
    reliability is important.  I'd go with the OS 1.08 from that
    perspective.  They run great and are reliable as they come.
    
    Charlie
    

    Re: -1
    
    Well the O.S. 1.08 is still the favorite, however I must admit to
    being favorably impressed with Clarence Lee's remarks about the 
    Webra 1.20, stating that it is 1000 rpm's stronger than any normally
    aspirated 1.20 and very well built. Plus it's $50 cheaper than the O.S.
    Hmmm....
    
    O.S. is like Microsoft - it just seems that everyone agrees they are
    the best.  It makes you wonder why anyone else can't do as well.
    I don't know, I guess I'll learn one way or the other after I get
    the engine.  At this point I am a little sorry that I did not buy the
    Saito150S for myself.  It only weighs 30 oz. and the $100 selling price
    really was too good to pass up!  Oh well, I won't be so nice next time
    ;>).
     
    BTW... shortening the nose on this towplane would be difficult because
    is is fiberglass with a moulded cowl.  I am planning on installing the
    rudder and elevator at the rear of the fuselage, to make room for the
    large gas tank and releaseable towhook bulkhead/assembly.
     

    I used to be indecisive, but now I'm not so sure! :-)
    
    EVL-1

    Jim,
    	It is always a good idea to install the RUDDER and ELEVATOR at the
    rear.  They work much better back there. :-)      (I know what you
    meant!)
    
    Charlie
    

    re: -2
    
    Indecisive- sure! But shopping is half the fun!  Sheldon's Hobbies is
    listing the Saito FA-150S at $454 with the following specs:
    
    RPM: 2.2k - 10k
    weight - 30.5 oz
    hp - 2.5
    prop - 14x10 - 18x4
    
    I really should have kept this motor!  I think it would have been
    perfect for my plane and much lighter on the wallet.  Hopefully
    the guy I sold(gave is a better description-$100!) will get it on
    his Telemaster and get into towing once in awhile.
    
    Whatever engine I end up with is going to be fun!  I like these big
    motors and the way the planes they are on fly.  None of this screaming
    .40 limping along on an extended takeoff because the grass wasn't mowed
    today stuff!  Hopefully this towplane/engine will haul up a 10 lb
    glider with authority.

    My "dream" towplane which may become a reality if I can talk my
    R/C philanthropist friend Robin into it is a 1/3 scale Piper Cub
    powered by a Zenoah G-62 with FEMA onboard starter!
    
    This plane towing up 1/3 scale gliders(16-20 ft wingspans) would
    really be cool and would be a lot of fun at the scale meets.
    
    Is this allowed at scale meets?  I know sailplanes do compete in
    scale competitions in Australia.
    
    I am anxious to see the towplane Robin has coming from Germany -
    fully moulded 1/4 scale Jodel!  It will probably be powered by
    an O.S. 300 twin.
    
    O.K time to wake up - got to get my relatively clunky "Major" done
    before entertaining anymore 1/3 scale Cub fantasies!
    
    Dreaming about future projects keeps my excited about R/C.

>    My "dream" towplane which may become a reality if I can talk my
>    R/C philanthropist friend Robin into it is a 1/3 scale Piper Cub
>    powered by a Zenoah G-62 with FEMA onboard starter!
>    
>    This plane towing up 1/3 scale gliders(16-20 ft wingspans) would
>    really be cool and would be a lot of fun at the scale meets.
>    
>    Is this allowed at scale meets?  I know sailplanes do compete in
>    scale competitions in Australia.

Meets - sure.
Competition - not really.

My interpretation of the rules would be that the Tow Tug could pull
up a glider as part of its take off maneuver and as such you could
enter the tug.  But the glider would not be competing aside from
earning "Realism" points for the tug.  Now the problem is the number
of pilots.  Unless you could prove that you could control both safely
then I wouldn't classify the tug take off as an unassisted ROG.

But like all things they are subject to the CD's rule and if approached
correctly you might be able to do it.  I think we have no concept of box
so you could specify a "glider release" as a maneuver and a "tow line
drop over the runway" as a maneuver and...

I've often thought of how a vertical take off and landing would
fit into the rules.

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

Regarding towing a glider in a scale contest...

Back when Al Casey, Bob Frey, and Dan Parson came up to Colorado Springs for 
a Scale Master's Qualifier I was there and saw someone enter a tug and glider.
Maybe John Tavares remember the details or can find out who it was. The routine
I remeber was the tug towed the glider up to release altitude, cut it free, and
then flew the rest of it's manuvers before landing. The glider did a couple of 
loops and came down fairly quickly.

    I believe in Australia Scale gliders compete with the power planes, at
    least in Static competition.
    

Those dudes were from Denver. 

    Thanks to all who provided input into my purchase decision for my first
    IC motor.
    
    And the winner is - THE O.S. 1.08!
    
    I tried hard to purchase some other engines but in the end, absolutely
    no one had anything but praise for this product.
    
    I hope it works as well as everyone says, I certainly did a lot of
    research on this purchase.
    
    
    Thanks again,
    
    Jim                       

    I finally got my 3�" spinner for my CAP231. It was a little rough in
    that it was spun  and not cut from a block as I think the Tru-Turn are.
    So on Saturday I drilled and tapped the prop bolt for a long m6 bolt,
    fine no problem. Then I cut out the spinner for a two blade prop setup,
    similar to how the Tru-Turn cut the spinner, and then the hole in the
    nose of the spinner. Finally I got to try it all, tightening up the
    retaining bolt for the spinner. I gave it a little twist and pop goes
    the aluminium behind the bolt. Great 8-(. So now it looks like I have
    to make up a small insert to put in the spinner to retain it. I knew it
    was going to happen but wished it hadn't. The aluminium was quite thin
    at the nose and I guess it would have happened sooner or later.
    Thanking that it didn't happen while it was running.
    
    I also got one of those hand starters where you wind the cord around
    and pull. Haven't managed to use it yet but it seems well made. Again
    one needs two people to start the engine, I guess with the 45 one would
    always want two from a safety point of view.
    
    Eric.

    In the new MAN the Webra 1.20 was reviewed.  I read this with great
    interest, as I almost purchased this engine last week, but opted for
    the O.S. 1.08 instead.
    
    A large part of the review centered around speculation of large
    2-stroke engines being used in pattern planes when the rules
    change in 1996.  It appears at this time that the .61 2-strokes
    can't make the power of the 1.20 4-strokes.
    
    Anyway the test was condcuted with several different mufflers and
    two different tuned pipes.  The range of props that could be used by
    varying the pipe length was amazing.  
    
    By varying the geometry of the pipe, the 2-stroke motor can be "tuned"
    to make best power at a certain RPM.  With one pipe the Webra turned
    a 20x10 pipe at 4700 RPM and with another it turned a 15x8 at 10,100.
    
    Although I am not a pattern flyer, I think the rule change is a good
    one that will open up the field to allow many more manufacturers
    engines to be competitive.
    
    It will be interesting to what prop/motor/pipe combinations arise
    in the pattern world in 1996.

    Personally, I DON'T think eliminating engine displacement limits is a
    good idea. All their doing is "trying" to correct the original
    mistake of allowing 120 4 strokes in the first place. Unfortunately,
    two wrongs don't make a right.
    
    The idea of allowing 120's was that 4 strokes didn't produce as much
    power as two strokes. To bad the people making this decision were about
    5 years BEHIND the times.
    
    If this rule change becomes reality, I can see me dropping out of
    pattern flying is a couple of years unless I happen to hit the lottery
    in the mean time. I can see this happening to alot of other people as
    well. I think pattern flying is well on it's way to being a "rich mans"
    sport and unless your rich (new planes will be needed to hold 4 strokes
    or the large 2 strokes...not to mention buying the engines themselves)
    or your sponsored in some way, you won't be able to afford it.
    
    They screwed up in the first place, but let it go so long, that they
    can't take it back now because of all the money people have spent on
    120's and 120 size airplanes.

    
       I agree with Steve, in fact, I think all pattern planes should be
     limited to old version YS.61's with leaking regulators, that way
     everyone will be equal! (with me :)
     

    Re: -1
    
    Steve,
    
         Since large displacement 2-strokes seem to sell for much less
    than the competitive 4-strokes(Y.S., O.S.), it would seem that the
    rule change would actually lower the price of a competitve pattern
    setup.  For instance the Webra 1.20 with a pipe would sell for
    around $350.  Isn't this at least $150 cheaper than the Y.S. 1.20
    4-strokes?  
    
    
    Regards,
    
    Jim
    
    

    Jim,
    
    	YS 120 (non air chamber) engines sell in the mid to high 300's.
    
    The problem is not just the engine. There's no way your going to fit
    an OS 1.08 in a 60 size plane. So, you need to build/buy a new plane.
    
    If you figure you can buy and build a competative pattern ship for $400
    dollars and then add on $375 or so for a motor, your looking at aprox.
    $800 to become competative.
    
    Unless something really unique happens within the next couple of years,
    I don't have $800 available to continue to fly pattern.

Re: Steve
        
   > Unless something really unique happens within the next couple of years,
   > I don't have $800 available to continue to fly pattern.
    
     But Colleen probably does!    8-)

    I've been thinking about this one for awhile and I really don't think
    that eliminating the displacement limit would change things much. 
    Sure, some folks would experiment with big 2-strokes but they'd just
    put them in planes designed for the YS120.  Noone would have their
    present equipment become obsolete or non competitive.  The YS120 planes
    already dominate the upper classes but the 60 2-strokers are
    competitive.  At Glen, FAI was won by a 2-stroke (a guy from Canada).
    His plane was so light that he could do a near vertical takeoff like a
    funfly plane.   The 5Kg weight limit which is already in effect would
    prevent any major increase in engine size and would keep the gas
    engines from being considered. (all of the TOC planes are over the
    weight limit)  
    	The YS120 is a very expensive engine to buy and maintain.  The
    larger 2-strokes would keep the simplicity and still develop the power
    that the YS120 develops.  I like the 4-stroke performance and I am now
    flying a Boxer 120 but I don't think that it is necessarily improving
    my competiveness.  I think that I could fly the routines just fine with
    the Conquest or the Graphik if I practiced with them as much as I have
    with the Boxer.  How the plane behaves is much more important than raw
    performance.
    
    Charlie
    

    What happens to a glo engine if you are running too large a prop?  Does
    is overheat, if so why?
    
    Thanks,
    
    Jim