Conference vmszoo::rc

    
    Radio Control Modeler (RCM) magazine has a complete book on the
    subject. It's an everything you wanted to ask but were afraid to 
    ask in this note file type of book. 
    It's called "Foam Wings". About 4.95. It's one of their Anthology
    Book series.
    
    						Tom

        You can find similar info in some of the homebuilt aircraft
        books. I have one by Rutan that shows how to build one to cut
        4' cores.
        
        A car battery charger makes a good power supply for smaller
        foam cutters.

================================================================================
Note 216.0                     Foam Wing Cutter                        6 replies
SPKALI::THOMAS                                       10 lines  30-OCT-1986 08:55
--------------------------------------------------------------------------------

    
    
    
    			Needed, one power supply for cutting
    	foam cores. 12v. max. 10 amp. Variable amperage desirable.
    	If you have something aroung that you want to part with 
    	let me know. Nothing complicated needed. 
                    
    
                                                 Tom
================================================================================
Note 216.1                     Foam Wing Cutter                           1 of 6
BPOV09::ERICKSON                                      9 lines   3-NOV-1986 12:17
                           -< Do You Need 10 Amps?? >-
--------------------------------------------------------------------------------

    Radio Shack sells a 120V (primary)/ 9V @ 2A (secondary) transformer,
    which I and a lot of others have used to source the switchers they
    sell (sold?) for TI 99A computers. Make a bow-type fixture and string
    some nichrome wire; connect either end of the wire to the two secondary
    wires. Consider a light dimmer for varying the current.
    
    --From the "Off The Top Of My Head" department
    
    John
================================================================================
Note 216.2                     Foam Wing Cutter                           2 of 6
SPKALI::THOMAS                                        9 lines   3-NOV-1986 13:28
--------------------------------------------------------------------------------

    
    
    		We have everything except the P/S.  We have tried a
    	12v 3 A. P/S and although it warmer the wire it wasn't
    	sufficient to cut. I figure that a 12v 10a variable supply
    	would be more than sufficient and allow some flexibility.
    
    
    						Tom
================================================================================
Note 216.3                     Foam Wing Cutter                           3 of 6
RIPPER::CHADD "Go Fast; Turn Left"                   16 lines   3-NOV-1986 17:12
                           -< Domestic light dimmer >-
--------------------------------------------------------------------------------

   Tom
   
    I use a 240v to 36v TXFMR and a light dimmer on the primary, the sort
    you use in domestic lights to give the sexy romantic atmosphere to your
    dinner party. 

    A lot will depend on the resistance of the Nicrome wire as to the
    optimum secondary voltage. I have successfully used part of a 2KW wire
    wound heating element. If you live in that continent north east of
    Australia where they use 120v you may find you have to use a heavy duty
    dimmer due to the higher current required. Use the thickest wire
    possible as it gives a straighter cut and local cooling of the wire is
    reduced. 

    John. 
    
================================================================================
Note 216.4                     Foam Wing Cutter                           4 of 6
BPOV09::ERICKSON                                     19 lines   6-NOV-1986 12:08
                           -< How About This One... >-
--------------------------------------------------------------------------------

    The new (1987) Jameco catalog shows an interesting prospect---it's
    called a "Coleco Linear Power Supply" (Jameco No. PS72C, page 69)
    for $39.95. Specs are provided below:
    
    	Input:	115 VAC 60 Hz
    
    	Output:	+5VDC  @ 6 amps, "10 amps max."
    		+12VDC @ 6 amps, "10 amps max."
    		-5VDC  @ 0.5 amp, "1 amp max."
    
    It comes in a nice ventilated case; it looks like a bench supply.
    
    Jameco is a major electronics mail order outlet that does world-wide
    business, and has superb turn-around time.
    
    		Jameco Electronics
    		1355 Shoreway Road
    		Belmont, CA  94002
    		(415) 592-8097
================================================================================
Note 216.5                     Foam Wing Cutter                           5 of 6
SPKALI::THOMAS                                        5 lines   6-NOV-1986 12:12
--------------------------------------------------------------------------------

    Thank's for the input. We have come up with a 13v. 8 a. supply.
    Were either going to make a wire wound resistor or use a light
    dimmer switch to vary the voltage. I said it was crude.
    
    					Tom
================================================================================
Note 216.6                     Foam Wing Cutter                           6 of 6
CRVAX1::KAPLOW "There is no 'N' in TURNKEY"          20 lines   8-NOV-1986 23:32
                         -< Try a car battery charger >-
--------------------------------------------------------------------------------

        A handy source for a 12v 10A supply, that you might already have
        laying around is a car battery charger. Also, a car battery itself
        will do a fine job, and can provide much more than 10A for some
        time. Even the book I got by Burt Rutan on full size home built
        aircraft suggests these for cutting small sections. They do
        recommend 24v (2 car batteries in series) when cutting large (4')
        cores. 
        
        A cheap temperature control can be made by using a second length
        of cutting wire, with a clip that can be slid along its length.
        The variable resistance will allow you to control the cutting
        temperature as necessary. The Rutan kit includes 1/32 stainless
        steel wire for cutting the foam and controling the temperature. I
        haven't tried it yet, but it seems simple enough. 
        
        One word of caution. DO NOT ATTEMPT TO HOT WIRE URETHANE FOAM. IT
        WILL EMIT TOXIC GASSES WHEN MELTED. Urethane foam is usually
        greenish or yellowish, and crumbles to dust when rubbed. The foam
        that you should be using is either blue or white, and doesn't
        crumble when rubbed. 

I used to cut cores but found that the foam blank quality was never as good as 
I hoped. Really isn't hard. If you want instructions I'd be willing to write a 
list of important do's and don'ts and some hints my friend and I used to work
around them. If people feel a general technique discussion would be good I'll
start and we can discuss how's and why's

Jim

Through Email I've been asked for instructions so I'll post them for all.

Building a bow for cutting foam:

Start with a piece of 1"x2" wood a foot longer than the loangest core you are
going to cut (the wood can be replaced for future uses, cut it to approximate
size for each use). Get 2 18" pieces of music wire (1/8th or 5/32nds") and
several wheel collars for each. Drill a hole the size of the music wire into
the end section of the wood at a 45 degree angle pointed out. Drill all the way
through. I drill into the 1" face so that the 2" side adds stiffness to the
final bow. Insert the music wire into the holes so that it sticks up about 2"
beyond the wood and put a collar on the lower side to keep it in place. Put 
another collar about 2" from the end of the long extention. A crude drawing is 
below:



              ====/==============================\====} 2" board
                 /                                \ <----collar
                /                                  \
               /                                    \ <----collar

You will need a variable source of DC power in the 6-24 volt range. We used an
electric train transformer. You need the high voltage as the cutting begins. We
used Nichrome wire bought from Sig to string the bow. To set it to length, crimp
one end of the wire in the fashion of a control line leadout. For power we used
16 gauge zip (extention type) cord with alligator clips on the end. The cord 
should be long enough to give free movement of the bow around the block of foam
with an alligator clip on each piece of music wire. To fit the nichrome to the 
bow, place the already finished end over the music wire and clip one power lead
to the music wire at this end. Stretch the wire towards the other end and clip
the alligator clip to the nichrome. Apply power until the wire turns red and
mark the glowing wire where the unused music wire passes into the wood. The wire
can be marked with a scrap (haven't used any??) of foam touched to it. Make sure
the wire is taut but don't bend the attached music wire. Shut off the power and
finish the second end where it is marked. Bend the music wire inward and slip 
the second end on. The music wire will now keep the nichrome taut when heated.
You want to keep the wire glowing red (pretty close at least) while it passes 
through the foam. You now have a functioning bow.

Core preparation:

Cut the foam blank to the finish length of the wing/stab being cut. Cut the root
and tip templates out of 1/8" plywood and mark the leading, trailing and thickest
chord points on each. These points are VERY important as you want to arrive at
the EXACT same time as your partner. Core cutting is a partnership and you have 
to work closely together. subdivide the sections between these points several 
times and Number the points (in the same direction on each). Remember that these
templates get glued on the end and that you want the numbering to cause you both 
to go in the same direction. Where the contour changes rapidly you want more 
points but you want the same number on both the root and tip templates. Glue the
templates to the ends of the core blocks with contact cement centered on the axis 
of the wing.

The actual cutting:

Steady progress is to be strived for. The more consistant the effort the better 
the final results. Go through a few dry (unpowered) runs and verify that you are
both going the same direction. Pick a location where you have unimpeded view of 
the end of the core block. Select a number near the top highest point of the
block and start the power. As you lower the wire into the block to the number, 
adjust the power to keep the wire cutting without dragging. you don't want to be
pulling a parentheses through the foam. As you cut keep your partner aware of 
the number location and your progress towards it (coming up on 4, at number 4, 
halfway to 5, coming up to 5, at 5...). Cut straight back from the trailing edge
and then go back after and plunge down to make a square edge. Keep the pieces 
you remove so you can stack on them when you turn it over to cut the bottom half.
Be VERY careful cutting leading edges since this is where most "Cupped out" 
damage occurs. If you try to cut too fast you'll drag the wire and the center
of the bow will dig in more. Don't press too hard on the templates as it will
cause the block to bend and the cutting to be untrue. 

This is the best I can think of at one sitting, ask questions and comment and
I can help refine it into something useful. Experience is the best teacher!

Good luck.

More on cutting for spars and servos/linkage/landing gear Monday

    You could call Wing Mfg at 815-459-0417.  If you send them a set
    of your root and tip templates they will probably have a set of
    cores in stock, if not they can custom cut cores for you.  Unless
    you are going to do a lot of cores, you'd probably spend less just
    buying a set.  There is a certain art to it no doubt and the parctice
    makes perfect part can get expensive.
    
    Will

    Having demolished the wing of my Ziroli Eindecker Sunday, I now have
    an excuse to practice the foam cutting techniques demonstrated by
    Eric Henderson at the last DECRCM meeting.  This wing is simple, 
    without ailerons, and of reasonable size; it would seem to be a
    natural candidate to try foam as a replacement for the original
    built-up balsa.  But I have questions.
    
    Given that:
    
        The plane (with skis) is rather over-powered with an OS 40 SF, and 
    
        The wing span is 55 inches, 
                 chord 11 inches,  
                 thickness is 1 3/8 inches,  and
    
        The weight with floats is 6 lbs, 6.5 oz. (before the crash),  and
       
        I would like to simply use Ultracoat over Friedrichs's foam,
    
    Questions:
    
        Should I put in a wooden leading edge or use just foam?
        
        Should I put in a wood spar?  Two?  Trailing edge?
        
    The plane is a shoulder wing with the original model having the
    top-center of the fuse built as a part of the wing.  That part was
    undamaged, so I'm thinking of cutting off this fuse section with the
    glassed center section of the wing upper surface and using that
    assembly as a wing hold-down, but not glued to the new wing.  I would
    use dowels vertically penetrating the wing from this hold-down to align
    the wing in yaw.  The glassed balsa should protect the foam from the
    rubber bands.  
    
    I'm an inept pilot, not skilled enough to go to 1/4-20 bolts.  But
    I have some Nylon bolts in smaller diameters.
    
    	Should I use small Nylon wing bolts instead of dowels?  Plus rubber?
    	Or only use these Nylon bolts to attach the wing to the hold-down?
    
    	Should I glass the center section of the foam wing?
    
    Alton, with so little time, so little knowledge, so many questions.

    
    --- ---------\ cockpit                                       
    |  \\         -------------- ------------------- fuse top surface
    |   \\  ___________________| |                                
    |    \\/ ----------------_   |                   wing upper surface
    |     \ /_____(wing)______-- |                                
    |       ---------------------                    tail ---->
    | view from left side                                      
    ------------------------------------------------ fuse belly

    Al, the last power plane that I had before giving them up to Gliders
    was a 80" 1/4 scale plane manufactured by a freind of mine in Salt Lake
    City, Lance Wise of Lance Engineering.  The Plane was called the Lancer
    Special and had a 2.3 Zenoah on it swinging a 18" prop and weighed
    about 11 pounds.  Lance started with his RV-3 that was all foam (with
    expanded bead) then covered with a fancy silkscreened lexan.  The Wing
    had a verticle aluminum spar in it for strength.  The lexan proved to
    be too heavy, especialy for those using the 2.3 Zenoah for power.  He
    then produced roughly the same model except the wing was a little
    shorter and the fuse looked alot like a round tapered tube. This one
    was pure foam.  The fuse had some balsa sheeting wrapped around the
    forward section and just some balsa cap strips leading to the tail. 
    The wings had some 1/16" ply installed as a spar, again just inserted
    into slots verticly into the wing.  The whole plane was then covered
    with Monokote, being careful to not heat the foam.  It was a great
    plane.  Again no problems.  Part of the reason the plain foam planes
    are covered with CHROMCOAT (cardboard) is to help with finishing, but
    it does add strength also.
    
    I would give it a try.
    
    If you are interested, We could cut some cores if you would like.  They
    are done hands off and produce quite nice cores.

>    its intended use. I once flew a Sig Scamp, (miserable little plane)
>    the wing was one piece molded foam with two strips of packing tape
>    on the bottom, no covering at all. Flew fine, including loops, rolls,
>    etc. The trick is to make sure the cardboard is stuck down "ALL

    My buddy had one of these Scamps.  What a beater.  We'de climb it for
    altitude, nose it over into a power dive, and then pull up at the last
    moment.  The stress would bend that foam wing into an elliptical shape
    with what must have been the equivalent of over 30 degrees of dihedral,
    then we'de kick it just a touch of rudder and *BANG*, some of the
    fastest, tightest rolls I've ever seen from a plane without ailerons.

    Alas, one day we didn't pull out of the dive quite in time and *BANG*
    some of the deepest, tightest furrows in the grass I've ever seen from a
    plane without airlerons.

re Note 56.11 by CSC32::M_ANTRY     "some 1/16" ply installed as a spar"
    
    Dan had suggested 1/8 spruce installed in a kerf.  How deep were these
    1/16 spars?  The stiffness goes up by the cube of the depth, linearly
    by thickness.  I'll be using 1/8 anyway because that's the width of my
    saw blade, and my airplane won't be nearly as heavy as the first one
    you described, but knowing the depth of the 1/16th stuff gives me
    something to relate to.
    
    Thanks for the offer to cut cores --- that would ensure good quality
    compared to what I'm about to do, but part of the interest here is to
    gain experience in something I've never done.  Note the "personal name"
    above. 
    
Alton

    re .13
    
    The tell you the truth I am not sure about how thick they were on the
    plane I had the wing was approx 2" thick and the kerf's were about 3/4" 
    One way to put the kerfs in would be to cut the wing in two and install
    the kerf and put it back together (the kerf would be the complete
    thickness of the wing).

I built my first one and have been using it since. What I did was drill two 
holes in the end of a 4 foot piece of 1"x2" wood through the 2 inch part at 
a 45 degree angle. I them put a wheel collar about 6 inches from the end of 
an 18 inch piece of 1/8" music wire and pushed it through the hole (do it
for each end). I then put another collar on each wire some distance from the 
longer end. This acts as a stop for the nichrome "hot" wire. You bend the 
wires inward and the springiness of the music wire keeps the tension (as the 
wire will stretch when heated). For power I used a model train transformer
attached to the short wire ends with alligator clips.

The important thing for success is to keep the wire tight so it doesn't drag
behind and scoop out in the center as you come over the leading edge.

Two people and templates with numbered marks on them to keep both ends in 
step also help. There are several people in the notesfile cutting cores so 
there should be no lack of information from those with more experience than me.

There's a lot of pride in flying a foam wing that you've cut yourself (and a
lot of unfounded worries too ;^)

To reply to a note that asked for a source for nichrome wire:
its very simple really.  I used this problem as an excuse for not
cutting foam wings for quite a while.  Then one day I was at
Phlyin' Phil's and behold: there was a 5 foot coil of nichrome
wire in a $1 package on the SIG rack.  No more excuses.  

I was going to enter a note on my foam cutting experiences,
but honestly, the previous notes cover the subject very well.
Half the problem with the process is in not believing its so
simple, but it is.  I use a old battery charger, but I've
bypassed the rectifier and am using the charger's 6V ac
output to drive the wire.  I've calculated the best charging
current at about 1.8 amps for the SIG wire.

Something I may be able to contribute to this discussion is that
I'm experimenting with covering a wing with light cardboard
(surprise!).  The cores are cut, using the E197 airfoil I
generated from George Schrader's postscript program (my version).
The cores are not perfect, and I've spent an inordinate amount of
time trying to fix the problems, but I should be ready to cover
the wing next week.  

Judging from Randy Oswald's built-up wing using this airfoil, it
should be well worth the trouble.  Randy: you ought to enter some
comment on that wing in the airfoils note, its quite different.

    I'm looking for somewhere to by nicrome wire to cut foam
    

Check with Sig or an authorized Sig dealer. They used to sell 5' rolls just
for this purpose.

    Another source of wire is your local Hermans' or equivalent sporting
    goods store that carries fishing tackle.  Stainless steel fishing
    leaders are available in 25' packages in a variety of sizes.  
    
    I think what I'm using is about .025" diameter.  A twelve volt battery
    with the charger attached and running, is drawing three amps on close to
    forty eight inches of wire.  It cuts blue foam very slowly but should
    be about right for the white stuff.  At twenty four volts it needs
    some additional wire to drop the temperature.
    
    Some articles I've read reccomended a slightly larger wire and a 
    twenty four volt supply.  You will have to run your own tests to 
    establish the ideal length and diameter for your power supply.  Its 
    cheap enough to experiment to your hearts content.

Try an electrical store for a replace bar heater element. You can unwind the 
wire and it will straighten under tension.

John

re Note 815.4 by GIDDAY::CHADD            Try an electrical store

A neat idea, John,  I hadn't thought of the laundry dryer heater element
that I have available.  But that raises  a concern for safety.  As the
resistance per foot increases because of alloy or diameter, so must the
voltage per foot increase (in proportion to the square root of the
resistance).  Plus the voltage in total must increase in proportion to the
length.  In the case of the dryer element we have 220 volts for bright red
heat and something less but still high for the dark heat that Eric
suggests.  Such voltages get my attention.  I could limit the power with a
wimpy isolation transformer, but that might not be enough.  I could also
limit the length used --- I don't know the stretched length of the entire
dryer wire.  Evidently your bar heater wire is safe.  What is a bar heater?

The five foot SIG Nichrome wire (SIG part number SH-135 @ $1) cuts foam at
30 volts, a comfortable number.  I'll use the SIG wire, not the dryer wire.

Caveat: The 30 volts at 1.7 Amps cuts a test slice, but it may not be the
correct heat for a clean, production quality cut.  I haven't yet rigged a
bow set-up; my measurements were a workbench jury-rig with a bench power
supply that won't go much beyond 30 volts.  I estimate the correct power to
be about one Watt per inch.

Re: <<< Note 815.5 by 9667::ARYDER >>>

> What is a bar heater?

A bar heater!!! Hm!! well it is cheap inefficient heater that is not used too 
often today. It consists of a core oF heat resistant material with Nicrome wire 
wraped around it along it's length.

Try using a light dimmer to control the voltage into your TXFMR. You will find 
it an advantage to slightly adjust the heat of the wire.

John

John Chadd: Interesting about 1.7A @30V cutting temp.  As I said
in the foam note, I'm running about 1.8A at about 6Vac.  Is your
30V ac or dc? I ask this since I've noted that dc seems to
require more voltage, and 30V could be about right -- the ac
worked for me so I didn't investigate further.

On the cutting temperature.  I ran the wire slightly hotter, at
about 1.9A and got some length-wise grooves that the local
experts said were from cutting at too high a temp (I'm using
white beaded foam).  This is why I reduced the current.   As you
said, its probably needed with this blue foam that
doesn't exist, at least in the Northern Hemisphere.  Anybody have
experience with both types and can compare the cutting
temperature?

BTW -- last nite I covered the cores with .015 thick white art
paper.  That is fantastic stuff.  The resultant cores are too
stiff to twist or flex spanwise.  I'll post some more definite
info in the foam note when I've thoroughly tested them.  Right
now I cannot for the life of me understand why anyone would
consider any other material for sheeting.  It ain't weight, since
the cores are at about the same weight as my balsa ones.  For a
28 inch span by 8 1/4 inch chord its 5 1/2 ounces -- and this is
with a totally unnecessary leading edge balsa cap.  I simply
wrapped the piece of cardboard from the bottom around to the top,
making a one-piece unit.  No need for the leading edge strip.

Re: <<< Note 815.9 by CTD024::TAVARES "Stay Low, Keep Moving" >>>

> John Chadd: Interesting about 1.7A @30V cutting temp.  As I said
> in the foam note, I'm running about 1.8A at about 6Vac.  Is your
> 30V ac or dc? I ask this since I've noted that dc seems to
> require more voltage, and 30V could be about right -- the ac
> worked for me so I didn't investigate further.

John, I would not have any idea what temperature my wire is. I don't really know
what voltage I use on the wire. I run a light dimmer into a 240-60v Txfmr. and
adjust the input voltage for the best cutting result, I would guess I run at
about the 20-30vac but I do use a heavy gauge wire. 

John

    John Tavares, I'm the one who measured the 30 volts DC.  To address
    your queries: 
    
    AC or DC it shouldn't matter.  At these currents and these power line
    frequencies we are not dealing with radiation, electromechanical
    effects, skin effect, or transmission line issues --- just heat.  If
    the RMS AC voltage (what a typical meter will read) is the same as the
    steady DC voltage, the heat will be the same for the same wire. 
    
    What can count is the length of the wire.  For a given wire the heat
    will be directly related to the current, no matter how long the wire,
    but the voltage needed to attain that current will be proportional to
    the length of the wire.  My 30 volt measurement was on nearly the
    entire length of a package of SIG wire.  If the wire were heated for
    only a foot of its length, then 6 volts would have done the trick. 
    
    The thickness of the wire will also affect the required voltage.
    The SIG wire is 0.0153 inches in diameter.  If it were much more
    thick and/or shorter, the required voltage would be much less.

    When you measured six volts, what was the set-up?
    
    Alton

Ok Al, we sure make it tough for the moderators, don't we -- its
both a virtue and setback for notes that its so easy to
participate in a discussion.

My cutting wire is just about 30 inches long.  I'm running it off
the 6Vac transformer output from an old battery charger.  I
calculated the ac current by taking the resistance of the wire
and dividing it into the rms voltage of the transformer.  I have
a giant resistor that I stuffed into the charger box that I use
to set the current.

If I use the dc output of the charger, I have to use the 12V
charger setting.  This is about 14Vdc.  At that voltage, I just
barely get a cutting temperature with the resistor cranked out.
This is why I concluded that you need less ac voltage than dc --
though your argument seems valid.

The ac seems also the maintain a steadier cutting temperature
across the wire -- with the dc I found the wire had cold spots,
though this is probably because it was not up to temp.

I made another cutting bow that is longer, but I haven't used it
yet, this will be my next project.

    >> I'm running it off the 6Vac transformer output ...
    >> If I use the dc output of the charger, I have to use the 12V
    >> charger setting.  This is about 14Vdc.  At that voltage, I just
    >> barely get a cutting temperature with the resistor cranked out...
    >> I calculated the ac current by taking the resistance of the wire
    >> and dividing it into the rms voltage of the transformer. 
    
    Remember, the resistance decreases as the wire cools, and since you 
    are bypassing the rectifiers, you're getting more voltage than you
    might expect at the 6vdc output.  Did you actually measure the output
    voltages under load?  There may also be some current limiting taking 
    place when you use the 12V outputs if the charger is a low amperage 
    model.
    
    In any case, if you want to keep the voltages low, you'll need bigger
    wire, and a source that can supply the amps needed to heat the bigger
    wire.  A real quick and dirty way to regulate temperature, is to start
    with extra wire in the system, and an alligator clip on the power lead 
    to adjust the wire length that is actually carrying the current.  
    
    If I had an appropriate transformer, I'd go with the light dimmer on
    the input as was suggested earlier.  As it happens, I have two deep 
    cycle batteries and two chargers so that is what I'll use. 

Be careful about using "light dimmers" here. Light dimmers are designed
for resistive loads - incandescant lights. A transformer is an inductive
load. Depending on the design of the dimmer, it probably won't be able
to handle the rated power with an inductive load. You'd be better off
using a ceiling fan speed control, which is designed for an inductive
load (motor).

Another safety warning - be sure to use some kind of isolation from
the power mains, ie.  a transformer. Use of a variac (autotransformer)
or a light/motor control without a transformer to step down the
voltage is dangerous because it doesn't provide isolation. You could
end up with your 6V foam cutter sitting at 120V or 240V above ground
potential. Touch the wire, you get burned AND shocked! Worse yet, turn
the power control all the way down without unplugging it - now your
wire would be cold but still at 120/240V. That could put you in the
hospital or worse.

Dave

Ok!  Thanks for the discussion, I didn't consider that the wire
changes resistance when hot.  Next time I fire the cutter up,
I'll re-measure everything just for kicks.  I can say that I'm
getting a good hot wire with the settings I'm using, so I have
little motivation to change the setup.  I'm going to re-try the
dc output of the charger because since I last cut cores I got a
positively decadent power panel, starter motor, and fuel pump.
I've enlisted the charger for the field box battery and have
restored the original connections.

We all have a spare handy 12 volt battery (in our flight box).
We all (most) have a 12 volt battery charger (for cars).

Now I think you guys are saying $1.00 to SIG and we're in business.
OK - How do I vary the DC current when I have my battery in series
with my charger?

On the subject of this note - does anybody know any hobby
shops in Mass that carry the SIG nichrome wire or do we have
to place a mail order for $1.00 plus $5.00 shipping?

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

    I guess its time to put my .02 in here.  I dont see why everyone is
    using batteries and battery chargers.  I made my power supply as a copy
    from the supply that NORAY sells in the RCM mags. (Least I think thats
    the one I copied)
    
    Here I go with the scematic, it may not be pretty:
             on/off
            switch   ______________    _________________     2A fuse
    ----------/ -----|light dimmer|----| Radio Shack   |-----~~~~~~~------
      120VAC         | $3 variety |    | 120V 25.2V 2A |              Bow
                     --------------    | CT transformer|------------------
    -----------------------------------|_______________|
    
    This has worked just fine for several people in our glider club.  The
    light dimmer is just the $3 variety from any hardware store.  The
    transformer is the $10 one from Radio Shack that is 120 primary and
    25.2 secondary, it is center tapped but just clip the center tap.  I
    believe on the secondary (the one with 3 wires) there are 2 black wires
    and 1 yellow one.  The yellow is the center tap and that is the one you
    clip.  The switch is one from Radio Shack and has a pilot light in the
    top so you can see if it is on.  
    
    Any other questions, let it roll.  I have been using .020 stainless
    fishing leader for wire.  The nicrome is a little brittle at times.  I
    am having some trouble with the wire/power supply.  The bow we are
    using to cut our glider cores is about 64" wide and I have trouble
    getting the wire hot enough.  I think next time I will move the
    aligator clips onto the wire vs the screws that serve as the attachment
    point on the bow spreaders.
    
    OK before anyone asks.  The Bow we use is made out of 2" x 3/8" Popular
    or BASS.  Take a 1"x2" and rip it in half so you end up with (2)
    3/8"x2" pieces.  I then make the bow like a big "I" and put the cutting
    wire on one end and the tension wire on the other end.
    
               Stainless cutting wire
         I-----------------------------------------I
         I                                         I
         I                                         I
         I=========================================I
         I fixed                             pivot I
         I                                         I
         I                                         I
         I                                         I
         I---------------XXXXX---------------------I
            tension wire with turnbuckle to 
             control tension
    
    The ends where the spreader arms meet the middle brace, one is fixed
    and the other pivots so that when you tighten the turnbuckle it
    tightens the cutting wire.  The ends there have two pieces that are
    glued on top of the middle brace so that they cradle the speader arms
    
           V----------spreader arm goes in hear
        II   II
        II   II
        IIIIIII
        IIIIIII
        IIIIIII
          III
          III
          III
    
    
    I know this wasnt the best but catch me off line by phone if you need
    more instructions:
    
    Work DTN 592-4751   Home (719)260-0673
    
    Mark Antry
    

Just wanted to thank Eric for the excellent foam wing cutting
demo on the DECRCM December tape.  It was the best info on foam
I've ever seen, and it pointed out several mistakes I've been
making due to lack of info.

Thanks Eric, and to anybody who's interested in foam, especially
if you've hesitated for lack of good information: this is IT!

    How can I get to see the tape on foam cutting???
    
    
    John
    

See note 1115.11 (which tells people in New Hampshire to send MAIL to Dan Snow
at THOTH::SNOW)  Be sure to include your full mailstop, DTN, etc.
    
This reply will be deleted in a few days.

>>>    I dont see why everyone is using batteries and battery chargers.  
    
    Some of us already have batteries and chargers.  They work, its just
    less convenient to vary the temperature.
    
>>> The bow we are using to cut our glider cores is about 64" wide and I 
    have trouble getting the wire hot enough.  
    
    I'd guess that your transformer is the problem.  It should have
    plenty of voltage for your application, but its current capacity is 
    too low.  I use forty eight inches of similar wire, and draw around 
    three amps at twelve volts.  If I choose to use larger wire to reduce
    wire lag on a larger bow, a battery can easily supply the greater
    current required by the larger wire. 

    
    What is the preferred method for cutting the channel for your 
    aileron (or other) control cables in your foam wing??
    
    I think a piece of brass tubing will do well for the straight
    shots, but along the way, you need to make a gradual 90 degree
    turn. 
    
    Or does everyone just use servos in the wings??
    
    thanks,
    jeff
    

I've used a few:

Old soldering iron to melt a channel. This will get the job done from one side 
but you need to fill the channel so I tried to first cut a wedge along the 
channel and then use the iron to open up the bottom. This gives you a piece of 
foam to slip back into the channel before sheeting/covering. I always use 90 
degree bellcranks on wings where I have outboard ailerons but then again I only 
use cables on the throttle (unless you're talking about pull-pull ailerons?)

I also mount my aileron servo on it's side with the wheel towards the leading 
edge in these cases to avoid having to come up out of the plane of the wing to 
connect up. This helps avoid binding and Futaba has a nice single servo mount
with ears to mount this way.

Free advice, and worth every penny ;^)

        Re:     <<< Note 56.39 by 39463::REITH "Jim Reith DTN 291-0072 - PDM1-1/J9" >>>

                I hate  bellcranks!   I'm about to cut a set of new wings
        for my glider and will use the new nyrods that aren't nyrods.  My
        plan is to mount  both  the  aileron and flap servos right at the
        wing root and make a channel with a soldering iron.  The trick is
        to fill the channel.  My plan is to use instant spackle compound,
        which is used to fill cracks and  voids in drywalls.  It's light,
        easy to apply and sands extremely easily.   Once the controls are
        in place the wing will be vacum bagged.
        
        Anker

I'd be willing to leave out the bellcranks in a pull-pull set up (has anyone 
done one?) for ailerons but I feel that between pushing a cable and bending 
the run there is either too much binding or too much slop. Maybe Eric Cullen
could comment with his recent experience.

Spackle sounds like an interesting idea.

Hi Jim,


I did the old 'soldering iron groove trick and put. as I mentioned in the 
Weekend note, the Bowden cable in to same. Its tight where it bends to meet 
the aileron.

This prompted me to strip a few strands off the cable. I suggest that you 
try it and see if you get any lesser slop - as I think that my connection 
to the ail. horn could have been better and the bend was fairly tight.

My flying buddy used the cable also and appears to be happy with his connections.
He didn't strip any strands off. I haven't seen his in action ie if there is 
a strain on the servo. 	

I have reverted back to full cables but haven't completly finished the job.

Regards,

Eric();

    Bite the bullet, get out the wallet and spend the money to put servos
    in the wing.  That way you have a straight shot from control horn to
    servo wheel using a short straight rod.  I just pulled my 2m slope
    plane wings out of the bags last night and will put 2 JR3001 servos in
    the wing for aileron control.

Re: .43

Mark,

  Do you see any problems with the added weight of a second aileron servo and 
the mass moving out onto the wing panels near the ailerons? You must see some
rotational dampening from the rotational inertia. Do you get any electrical 
noise from the long servo feed wires?

Enquiring minds want to know...

    re. 44
    
    I've never been able to notice any effect caused by rotational damping
    from outbd. servo weight. Of course on a glider, roll rates are
    fairly irrelevant but even on F3B ships which do need fast roll
    response, the roll rates are right up there with many power planes.
    
    The long servo leads can cause glitching/interference especially
    if they pass over or near the flap servo leads. I think I was having
    that problem on my last original design but crashed the silly thing
    in high wind before I could pinpoint the problem.
    
    I agree with Mark, using as many servos as you have control surfaces
    and mounting them as close as possible to the control surface, is
    the only way to go, cost aside. And speaking of mounting servos
    in foam wings, on my newest wings, nearly finished, with flaperons
    and spoilers, I mounted the servos with "Super Stick Tape" from
    Radio Shack. This is NOT velcro. It's what I call "knob and stalk"
    and really holds the servo in place with no screws or mounting strips,
    etc. No play or rocking as long as you have a smooth epoxy surface
    laid down in the cavity for the adhesive backing to grab.
    
    Terry
    

 >   The long servo leads can cause glitching/interference especially
 >   if they pass over or near the flap servo leads. I think I was having
 >   that problem on my last original design but crashed the silly thing
 >   in high wind before I could pinpoint the problem.
 
   I came across an article on Active Leads for those planes that are using
   long extensions. If I remember it placed a quad CMOS inverter somewhere along
   the lead. He included circuits and diagrams of results of signal cleanup.
    I could dig up the article if anyone is interested.


	Eric();

If I ever get around to the P-38 project I'll be using a distributed radio/servo 
planform and will probably need to look into this. This might not be the topic 
for it but please post it if you find it.

Jim

    Yes, dig up the article and post it if possible.
    
    On Long servo leads, my current F3b plane has all wing wires wrapped
    around torrid rings right were they enter the fuse.  We have other
    planes that dont use any torrid cores and they are just fine.  Remember
    other than the radio itself there is no other electical noise (like a
    engine) and no vibration to speak of.  I dont plan on doing anything on
    my current wings unless it needs it.  I know Terry ran into some
    trouble when the radio(TX) was close to the servo wires, it would
    overload it.
    
    Also on putting my servos in the wing.  I did that last night and just
    laid the servo down on the wing over the top of where I coiled up the
    servo wired and traced around it.  I then put a piece of tape around my
    dremel tool bit for a depth indicator and carved it out.  I had to make
    a slot back under the wing for the wire and deans connector but the
    whole thing turned out just great.  The servo fits down in there nice
    and tight and takes two pair of needle nose pliers to get it out.  On
    our team's F3b planes the ICON we have acutally made a mail servo plug. 
    We will then carve the hole out a little big and then fill it about 1/2
    way with epoxy and microballons grease up the plug and push it in. 
    Wait overnight, pull the plug out and presto, instant modeled servo
    hole.
    
    The slope plane is coming along just fine.  Last night, I did the
    servos in the wings, dressed up the stabs, drilled the holes in the
    stabs for the brass tubes, installed the bellcrank and pushrods in the
    fuse, installed the brass tubes in the stabs and got them on the plane,
    put some expando foam at a couple of spots in the fuse to hold the flex
    cables in, put in the recv wire tube, installed the rudder/elevator
    servos in the fuse.  I would like to test fly on Sat but doubt if I
    make it.  As long as it is ready by April 6th, I am going to San Diego
    on Business and plan on taking it and going to Torrey Pines to test it
    out.

    What is the best material to use for templates if you plan on re-using
    them a number of times???
    
    The only material mentioned here so far is 1/8" ply.  When Al and I
    were playing arund, we found that it was possible to burn a notch in
    the template, thus rendering it useless...
    
    They used some other material on the foam cutting video tape...  Can
    anyone tell me what it is??  
    
    Thanks,
    jeff
    

The best stuff that I found that works is phenolic board, you know the stuff
that they make PC boards out of.  But it is a little thicker than 1/8th.  Also
most of the templates that I am using are made out of Formica board, its a 
little hard to cut but tough and temperature resistant.  Also if you are burning
your templates you are running the wire way to hot or leaving it in one place.
If you are using the hands off cutter  that CHANNEL 1 productions describes 
the wire should be on the template with tension pulling against it before the 
wire is turned on and then the wire will pass through the foam only after it
heats to sufficient temp to melt the foam. Again you want to cut as cold as 
possible.  The templates that we use for our club ICON F3b project are laser
cut out of 3/8" ply with a teflon tape on the template where the wire goes, for
smoothness and heat resistance.

>                       <<< Note 56.50 by NEURON::ANTRY >>>
>                          -< FOAM CUTTING TEMPLATES >-
...
>possible.  The templates that we use for our club ICON F3b project are laser
>cut out of 3/8" ply with a teflon tape on the template where the wire goes, for
>smoothness and heat resistance.

OK Mark - now you've got to tell us all about the "laser cut"!

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

    OK, well I dont have the info but I do have the templates.  There is a
    guy somewhere here in the US that has access to a laser mill machine or
    something of the like.  He took a piece of 3/8" Aircraft type ply and
    burned 4 templates out of them for us (top and bottom root and top and
    bottom tip) the laser is so precise that he even burns in 3 nail holes
    on the bottom that are less that 1/16th" in diameter and leave two
    little tits on each end that holds the template in the piece of wood
    until you press them out.  He then furnished us with some adhesive
    backed teflon tape that we affixed to the cutting surface on the
    template to help with heat dispersion and with friction of the wire.  I
    would not rave about the templates for 1 because you could clearly see
    that the laser was stepped from point to point and did not have any
    curve fitting algorithums applied to it.  All in all, if you just got
    to have those templates down to the nats eyelash they are the way to
    go.  He charges $25.00 per template which consists of two pieces. A
    negative image bottom piece and a positive image top piece, with
    leadouts and leadins for the wire to rest on.

I use Aluminium for templates and attach them to the foam with double sided 
tape. To cut them accurately I use the sheet metal technique of center popping 
the line and shaping so half the center pop is removed. 

 eg: --o---o---o---o---o---o---o---o
                                        
As already stated it most important to have a smooth surface for the wire to 
rest on to obtain the best results on the finished product.

John

    Thank you Jeff for the core cutter plans, received yesterday.
    
    I must admit that at first glance they do not make too much sense, but
    will spend some more time this weekend going over them.
    
    
    	George Frost

    No, they don't make a whole lot of sense alone...  It would be really 
    good if you could see the video that goes along with it...
    
    Perhaps someone that has built/used it can fill in the fuzzy areas..
    Mark??
    
    jeff
    

It goes together pretty well.  A couple of pointers, for the 4 pulley wheels
go to your local Hardware store and buy sliding glass door replacement wheels.
They are about 1" in Diameter and have a sealed bearing to roll on plus some
bolts to screw them into.  As far as drilling all the holes in the 1x1 piece 
that sits on the back of the table, dont.  Put two holes in the back one above
the 100% mark on the lever arm and one about the 70-80% range, you dont need any
more than that.  I have made up two tables one is 62" wide for wings and one is
20" wide for stabs and again, I only have two holes in the top of the 1x1 piece
way out on the ends.  The only difference this makes is that unless the foam
block is sitting at the same place as the string the precentages for figuring
the taper to apply that figure onto the lever arm is different.  But you are 
going to have to fiddle with the placement on the lever arm so that the strings/
bow exit the foam at the same time.  For the Clamps to hold the sting onto the
Lever arm, get some of the big spring loaded clamps at the HW store, dont get
the big ones, I think they have a 1" opening capability.

Lets see......I used some of the shelving brakets to hold my table on the wall.
You know the ones that have the slots in the verticle bars and then the brackets
slip in thos holes and you set the shelf on it.  Works fine plus you can put
up three brackets and use the narrow one for the stab table.  

OK your turn....questions?

    
    
         A quick question on the automatic foam cutter.
      I have completed building this table and now I've better
      put it to use or explain to my wife why I built this thing
      in her potting station area of the basement.
    
      I viewed the video on the automatic cutter a while ago (2-3months)
      and I am now confused as to how the templates are made. Am I
      supposed to make the templates as a "cut out" and not the actual
      core shape itself?.  I am probably not clear. What I am trying to
      say is the template the piece of "material" that you cut out of
      the the raw stock or is it the  hole thats left over?. I also have
      found a supply of NiChrome wire that was quite reasonable. It comes
      from a scrap  of "K" type thermocouple wire.  The yellow covered wire
      not the red is NiChrome wire, I found some in .020 size and it works
      great. 
    
      Thanks for any help
    
    
      kevin p

>      and I am now confused as to how the templates are made. Am I
>      supposed to make the templates as a "cut out" and not the actual
>      core shape itself?.  I am probably not clear. What I am trying to
>      say is the template the piece of "material" that you cut out of
>      the the raw stock or is it the  hole thats left over?. I also have

The templates are the shape of the airfoil - not holes.
Though I must admit the template part of the video was amazingly confusing.
If you would like me to put you back on the video list so you can see it
"one more time" send mail.

>      found a supply of NiChrome wire that was quite reasonable. It comes
>      from a scrap  of "K" type thermocouple wire.  The yellow covered wire
>      not the red is NiChrome wire, I found some in .020 size and it works
>      great. 

Is this a large supply?  Convenient for the rest of us noters?  Price?

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

To use the automatic foam cutter you use two templates the one that cuts the top
of the wing(airfoil) is what I would call a positive template in that the wire
rides on top of the airfoil and the template looks like the top surface of the
airfoil.

          /-----
--------/        ------------
|                            |
------------------------------

Boy is that crude......

The other template is a negative template and is used for cutting the bottom 
surface of the airfoil and its template is void of the airfoil shape.


--------              ---------
|        \ _________ /        |
-------------------------------

In other words take two pieces of 2" wide by say 12" long material, I use 
formica scraps.  Now make a line dividing those two pieces in half length
wise.  Make sure these are the same because you will use them to position your
templates.  Then take an airfoil drawing and draw a line if one is not provided
from the center of the tip to the center of the tail lengthwise.  Now cut the
template on this line.  You are now left with two pieces of template, the top
half and the bottom half.  Now take the two halfs and position them on the
template right on the line that you have drawn.  Also they need to be positioned
starting at the same places.  I genraly place the tip (le) 1/4 - 1/2 inch in
from the right.  Now comes the fun part.  Cut the templates out.  YOu will go
in on the line that divides the template material in half and when you get
to the template on the top one you will cut on the outside of the template, 
leaving the template attached and on the bottom you will cut inside the template
removing the template.  now if you hold these two pieces together and provided
the bottom template is in front of the top template you will see a 
representation of your airfoil.  Now clean them up with some sandpaper and then
holding them together so they form a perfect airfoil dril 2-4 holes in both
templates (stack drill) so that you can put small nails through there to hold
the templates to the foam and also serve as indexing.

Questions, fire away....

    Mark,
    
    Seems to me like you mixed up the aerofoil tracing with the templates
    that need to be cut out! Makes it hard to figure wha'cher talkin'
    'bout.
                                                    
 >>   template on this line.  You are now left with two pieces of template
 >>   the top half and the bottom half.  Now take the two halfs and position 
 >>   them on the template right on the line that you have drawn. 
    
ajai
    

    I'll give it a try. I watched the foam cutting video last night. Neat 
    system. It's a must for this winter ;^)
    
    The cutter that the templates are for hangs below the cutting table
    thus there is always downward pressure on the wire. The bottom of each
    template is rectangular to match the end of the block for alignment.
    So, the bottom template is the shape of the bottom "waste" and the top
    template is the shape of the airfoil. In the video they show the two
    templates being held together and holes drilled through them to be used 
    for the nails that push into the foam block to hold them in place. This
    way you can line them up by using the same holes when you put on the
    other template. The cutter is used on one surface at a time. I liked
    the idea of the bottom surface being cut first and the block settling 
    down before the top surface was cut.
    
    The one thing that the Video didn't cover was how to tell when the wire
    is the right temperature for the "cold" and "hot" cutting. You can't tell
    from the video what the color of the wire actually is (cherry or dull red)
    From the speed of the cut it should be easy to figure out but hopefully 
    it won't take too many blocks to get it right.
    
    I'll be building one of the automatic cutters over the thanksgiving 
    weekend ;^)

Yes, AJAI is right, when I refer to cutting the template in two, I am refering
to the airfoil tracing.  Thanks for making that clear.

How hot is the wire?

You want the wire as cold as possible, so try just passing some scrap blocks
of foam over the wire while adjusting the temp.  Also one of the biggest 
misteaks you can make is to let the wire get hot before it enters the foam.
The procedure is wire on the template, remove bolt from weighted arm let arm
take tension up on the bow pulling it into the foam, turn on power supply.  When
you look at the foam core that has been cut there should be wispy pieces of foam
on the cut, refered to in the video I believe as angel hair.  Again adjust the
temp as the wire is moving through the foam and cut as slow as possible.
You will see if it is too hot if you can see where the foam has been melted
and burned by the wire.  

I cut my first cores last week and I think I'm sold on foam. I'd like to take a
look at and possibly build the hands-off cutter. How do I get a copy of the
plans and tape?

Randy

    Assuming you signed into DECRCM, you send mail to Kay requesting to be
    put on the V-12 distribution list. I've got the tape now and will be
    forwarding it along to the next viewer tomorrow. There will be several
    copies of the plans in with the tape. Kay said it had several
    originally but there were nonwe with it when I got it. I've yet to cut
    a set of cores because I need to make templates but that will happen in
    the next couple of days. I'll enter more in here as to the changes I
    made and what I did differently in case others wanted to try them.
    
    I hope it's as easy to use as it was to build. The video makes it look 
    so easy.

    Dan,
    
    I'm using the Sig nichrome wire available in 5' lengths. I've seen it
    at Ray's in Worcester and Tom's in Chelmsford. It does stretch when
    heated and you need to adjust the spring as tight as possible to avoid
    sagging. If you really get stuck, I've got a second package at home
    that I could sell you (but I'm keeping it a a backup for when the wire 
    breaks and I'm halfway through a set of cores ;^)
    
    My pivot arm moves almost a foot and I used one of the long door springs 
    to take up the slack.

    Cutter update as I promised.
    
    One of the things I found was that the table is a b*tch to keep from
    sagging. I ended up putting a piece of angle iron on the front and back
    edges screwed down every 3-4 inches the whole width. I still don't have
    a perfectly level table so I cut a flat bottom on the block before I
    remove it since the cores and beds are level to this while weighted to
    the table. Otherwise the bed might bow upwards in the middle once the
    weight is taken off (or weighted down on a truely flat surface) The
    table isn't that much off but neither is the washout in most of the wings 
    I plan to build.
    
    Another thing that I did was make up a bunch (10) of sharpened finish
    nails with dowel heads glued on for holding the templates onto the
    foam. (just like the video shows at one point) I looked at them and
    figured they'd never be around when I really needed them so I drilled a
    series of holes down the 2" wide side piece of the arm unit and pushed
    the nails in there. If I'm good about putting them back, they'll always 
    be handy when I need them. I'm going to do a bunch of wings this weekend 
    after I get some more foam from Jeff F. tomorrow.
    
    The last thing was to get a pair of "L" shaped brackets instead of the 
    shelf brackets they suggest. The biggest shelf brackets I could find
    were 12" (they suggest 16") but I got 14" Ls. With wooden extensions
    bolted on (they have bolt holes built in), these work out fine. No where 
    as wiggley as the shelf brackets.
    

    Oops - I deleted 56.65 just as you entered .66.

    I went back and re-read all of 56.* and realized that fishing leader
    is stainless steel 0.020 wire.  Mary Antry mentioned this in 56.??.

    So - It's off to Spag's to get some fishing leader (and other stuff)
    and then my new foam cutter should be ready to go (as soon as I get
    an acceptable power supply...)

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

    I cut a set of wings on saturday with my automatic foam cutter. I think
    it will end up looking like the video after I get done with the
    "tuning" but the first one took a few tries to get it working. The
    "angel hair" wasn't too hard to achieve but that stuff gets onto
    everything. My biggest problem was the weight of my bow. I had oak in my
    workshop and planed it down to 1/2" thick but it was still too heavy to
    allow the bow to be pulled back with the 1lb. arm weight. I put two hooks 
    into the underside of my shelf and used a chain of #64 rubber bands to 
    offset some of the weight (you want SOME but not too much). I'll be
    cutting more wings as the winter goes on. I'm also going to try some
    foam foundation insulation that I have hanging around. It seems about
    the right density and it comes in 2'x8'x3" slabs from the local lumber 
    yard (I don't remember it as being expensive)

Idealy you need the bow to way in the 1 lb range.  That is where I have mine
after much trial and error.  When I first started out my bow weighed 3 lbs and 
we had all kinds of trouble with the wire stuttering accross the templates, etc.
we counter-weighted the bow and hav since licked that problem.  Also the weight
on the arm should only be about 1 lb also, if the bow is not too heavy then 
the arm doesnt need to be weighted heavy either.  The way I weighted my bow was
to to put 2 small pulleys at the ceiling and ran a string through them with a 
1lb weight on each, then the other end of the string was attacted on the end of
the bow, on each end.  Presto, 3lb bow, now weighs 1lb.  Position the pulleys
so they are right over the ends of the bow and about the half way point on the
the table (front to back) so they are not pulling the bow in a funny direction.
Also now that the bow is light you may have trouble with the bow not wanting to
follow the template when cutting the bottom surface.  What will happen is as
the bow starts into the foam and encounters the LE where it should drop down
it will want to continue straight because it is not heavy enough to follow a
quick dive, the secret is at the beginning of the cut just hold a little down
presure on the middle of the bow's cross piece, hence making the bow heavier.

Works great.

I am not sure what you did with the rubber bands but I sure dont use them and
I have cut I am sure well over 100 panels with my cutter.  Again, 1lb bow, 1lb
arm is all you need.

    RE: .69 & .70

    Gee, isn't it funny how everyone tries to re-invent the wheel over and
    over again.  My bow weighs too much also and I've had the same
    problems.  When I was at the lumber yard and I asked for 1/2"x2"
    stock, the guy asked me if 1"x2" would be good enough.  I said "sure"
    thinking that it would just be stronger.  What I forgot is that it
    would also be heavier...  Not only that, but I made it longer too.  My
    bow is 62" on the inside dimension - allowing me to cut up to 5' (60")
    cores.  Why?  Ummm... because I thought it would be a good idea?  I
    also plan on making a bow that's only 40" to 48" long.  Not only will
    it be lighter but it will be easier to handle too.

    The way I solved it on my first 2 test cores was to hold the bow up a
    little bit by hand.  Of course, this gives totally unacceptable
    results.  Once, the bow went up off the template on one side of the
    top of the wing and another time I experienced what Mark referred to -
    the lower surface had an extra notch cut out of the leading edge.

    I'm so glad this notes file exists.  I'll go home tonight and weigh my
    bow then counter balance until it weighs 1 lb.

    Another problem I had was that my first shelf was much longer (54")
    than the cores I was cutting (35").  Thus, when my heavy bow pulled
    down on the ends of the wire between the template and the edge of the
    shelf, the wire dragged on the shelf, causing the wire to stick and
    skip.  I solved this by making a shorter shelf.

    The other problem I've got temporarily is that I don't have a good
    variable power supply.  I've been using a car battery.  Soon I will
    have a 0V to 48V adjustable DC power supply that will put out 5 amps. 

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

    Thanks for the tips Mark.
    
    If you picture your set up, your pulleys on the ceiling are my hooks
    under the shelf and the rubber bands are the lines that connect to the
    bow. Mine are centered and attached to the bow cross member. The wire
    is free to travel and probably ended up with about 1lb weight on it. I
    was happy with the final results but it took a core to sort it out. I
    clipped a misaligned nail on the first one and that didn't help the
    core any. I ended up using the Sig nichrome and found about 17 VDC from 
    a model train transformer to be about right for "angel hair" on the 36"
    cores I was cutting. It looks like fun and I'll be putting in more time
    with it after the holidays. (time to convert back to a wood shop for a 
    few quick Xmas gifts ;^)

OK Jim I get the picture on the rubber band idea.  My only concern would be that
it counterwieghed the bow evenly.  So I hope you have them as close
to the ends of the bow as possible.  The other nice thing about hanging it
from the ceiling is that that after a cut I take the bow and put it under the
table and there it hangs (it stops when the weights hit the pulleys) so it is
both out of the way and also handy.

My bow was built out of 1/2" x 2" basswood as recomended in the article but
still not stiff enough for a 60" bow.  


Lots of fun isnt it!!!!!!

    Yeah, they're out near the edges of the 52" shelf. My shelf is mounted
    about chin level so I just lean the bow against the wall when I'm done.
    The other thing that I didn't take into account was the power leads and
    I had one hang up initially. I also had the bow bump into something while 
    cutting so I had to be more aware of what was on the adjoining walls and 
    floor.
    
    Next month (if Santa was paying attention), the joys of vacuum bagging

    I've been scanning this foam note for a friend (Elliott, the sailplane
    builder I've talked about).  It seems as though all the pieces are
    here, but he just can't seem to get his hands around it.  The above
    boils down to this:
    
    Is anyone willing to put a reply here that would guide someone from the
    making of the cutting tool through the actual fabrication of a foam
    wing?  	(All inclusive in one narrative.)
    
    My thanks if anyone wishes to undertake this-
                           __|__                              Regards-
    \________________________O________________________/       Frank.    

    

    Frank,
    
    Beg or borrow the video on cutting foam cores.  You could have Kay ship
    you the DECRCM tape and then charge him a buck as you both watch it, or
    perhaps a local hobby shop has a copy you could borrow or rent.
    
    One video is worth a thousand replies...  Watching the video really
    gave me a much better understanding than listening to people and
    trying to figure out what they were saying...
    
    cheers,
    jeff
    

    More on the automatic foam cutter.
    
    I cut a couple of sets of wings for Jeff Friedrichs this weekend and
    had problems with my "pulleys" hanging up the line. I got the cores cut
    and when talking to Jeff about them I mentioned the problem and he came
    up with a perfect solution. Instead of using the pulleys I have, use
    sewing machine bobbins. The metal ones with the central shaft for the
    axel screw. These have wide sides and will make great pulleys (line
    guides really). Great idea since most of my problems were due to the
    line being pulled up over the edge of the rear mounted pulleys due to
    the height of the template on the foam. I'll be trying this out on the
    next core cutting session.

    What do people do for wingtip of sheeted cores??
    
    On my C-45, I used 1/8" ply with balsa block.  This was cut and sanded
    down to shape.
    
    I'm not sure what I am going to do for the Eindecker wings...  We have
    talked about using the above method, or the above with foam rather than
    balsa.  Or we could use solid balsa blocks.  Or we could use built up
    tips, but I would be concerned about the strength.
    
    How does everyone else do it??
    
    thanks,
    jeff
    

    If your only concern is durability, simplicity and ease of building
    then there is one tip construction method that is far superior to
    all others, for foam sheeted wings:
    
    Sand a ~ 45 degree bevel in the underside of the tip and face it
    with 1/64 " ply, balsa is okay too but has less dent resistance.
    
    Of course this method limits your choice of wing tip shapes and
    wouldn't be suitable for most scale projects, but for sheer
    functionality it can't be beat. I've dropped 80+ oz. sailplanes
    straight in on the wing tip without damage.
    
    Terry
    

From the usenet.

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

Article         3892
From: [email protected] (Henry Pasternack)
Newsgroups: rec.models.rc
Subject: Description of the foam core cutter.
Date: 6 Feb 91 01:47:06 GMT
Sender: [email protected]
Organization: SRI International
 
 
   I've received enough replies asking for information on my foam
core cutter that I have decided to post a description of the device
on the bulletin board.  It is somewhat complicated to describe
without pictures, so I will try to be as wordy and descriptive as
I can -- bear with me.
 
   The design was intended to offer exceptional versatility for
cutting a wide variety of cores.  With this goal in mind, I started
out building a very flat, sturdy, two-foot by five-foot workbench
about 28 inches tall.  The top is made from 3/4" Baltic marine birch
plywood framed underneath with very straight, milled clear pine.
A gusseted framework of 2x2 fir makes up the legs and base of the
workbench.
 
   The benchtop has been drilled with 100 3/8" holes, drilled on
one-inch centers and arranged in two rows of 50.  The rows are drilled
parallel to the long axis of the benchtop and are separated by a 
distance of 12 inches.  There is a ten-inch gap in the hole pattern
at the midline of the table, so that the arrangement really consists
of four rows of 25, like this:
 
 
  --------------------------------------------------------------
 |                                                              |
 | .........................          ......................... |
 |                                                              |
 |                                                              |
 |                                                              |
 | .........................          ......................... |
 |                                                              |
  --------------------------------------------------------------
 
   Each hole has a 5/16" blind nut in the bottom.  The result is a very
flat working surface to which all sorts of jigs can be bolted.  With
the appropriate fixtures, this table might form the base of an excellent
wing or fuselage jig.
 
   In order to secure the foam to the table, I have built a 14x45x1"
"bed of nails"  with eight holes along the edges so that it may be
bolted to the tabletop.  There are 25 nails sticking up 1/4" above
the top surface of the board.  Once it is pressed down onto the nails,
the foam blank has no tendency to slide and only requires a little
weight to hold it in place.  I am currently cutting 48" cores, but
when I switch to a different size, I will either make a new bed of
nails, or cut this one into sections and just use enough pieces to
fill up the required distance.
 
   The system uses two templates at each end of the core.  One pair
of templates is for the bottom surface and one is for the top surface.
This way, the wire always presses down on the template.  Another
advantage is that the template can be extended past the edge of the
core.  This is important at the trailing edge because wire drag
causes the center of the wire to come out of the core later than the
edges.  I extend the trailing edges of the templates straight out for
an inch or two to make sure the dragging wire comes out in the right
direction.
 
   The templates are screwed to a pair of 1x1x14" square aluminum
tubes which are bolted to the table at either end of the bed of
nails.  Because the bed of nails is the same height as the template
holders, the ends of the foam extend off the bed and rest on the
holders.  The templates are mounted on the outside edges of the 
aluminum tubes so that they can be changed between cuts without
disturbing the foam.
 
   The cutting bow is made from 1/2" steel water pipe.  It is 60" long
and has nine-inch cross-members pivoting in machined PVC fittings at
the ends.  Insulated screw-eyes hold .033 piano wire on one side, and
a strong spring with a turnbuckle and cable to draw up slack tensions
the other side.  The bow is drawn through the foam by a pair of heavy,
braided fishing lines which attach to the cutting wire adjacent to the
templates.  I fashioned small hooks out of steel wire which I wrapped
around the cutting wire to hold the line (this is not ideal because
the bow is shorted out in the vicinity of the hook and develops a cold
spot.  I am working on devising an insulated solution).  The draw
lines are guided straight away from the bow, parallel to the tabletop
and pull the bow from leading edge to trailing edge.  They pass over
pulleys and continue down toward the floor.
 
 
              spring        turnbuckle
       
     =[~~]o-o///////o-------o[|||||]o---------o[~~]=
       ||                                       ||
       ||                                       ||
 pivot <>!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!<> pivot
       ||                                       ||
       ||                                       ||
     =[__]o--o-----------------------------o--o[__]=
            /        cutting wire         /
           o                             o
          / draw line                   /  draw line
         /                             /
        /                             /
       ()  pulley                    ()  pulley
       |                             |
       |                             |
       V                             V
 
   The bow is suspended from the ceiling by thin rope so that the wire
rests on the templates and most of the weight is taken up to reduce
the sliding friction.  I tried using a weighted pulley arrangement to
hold the bow, but found the solid mounting to be better.
 
   Now the description gets trickier.
 
   Each template holder has a three foot length of 3/4" steel tubing
passing through it.  The tubes are flush with the leading edge ends of
the template holders, so that they stick out 22" at the trailing edge
and extend a foot and a half beyond the tabletop.  The tubes are
riveted in place so they can't move in the holders.  I have machined a
pair of aluminum donuts about three inches in diameter which have a
setscrew in them so that they can be positioned at any point along the
protruding steel tubes.  Opposite from the each setscrew I have
machined a flat surface on which is mounted a ball-bearing v-groove
pulley.  The bow draw lines pass over these pulleys and bend ninety
degrees so that they point toward the ground.
 
   I have tried to illustrate this in the following side view.  I
left out the horizontal extent of the draw line because the graphics
stink.
 
    pulley                                  wire   template
                                       |\____o________-------/| 
     ###                            ---|                      |---
    |(*)||||||||||||||||||||||||||||   |+    +    +    +    + |   |
     ###     steel tube             ---========================---
     |                                    template holder
     |
     |                                    leading edge --->
     | draw line
     |
 <-  |  ->
   ==o=========================0  hinge
  |        drop leaf           |
   ============================
 
     |
     V
   motion
 
   O.K.  Now, all we need is a way to pull the draw lines proportionally
so that the taper works out properly.  For this I use a "drop leaf"
mounted on the front of the bench legs, about a foot below the table top.
The drop leaf is five feet long and eighteen inches wide.  It is actually
made of a one-foot board and a fir framework to save weight.  The draw
lines attach to the top of the drop leaf.  The force of gravity pulls it
down against the tension in the draw lines.  By moving the attachment
point of the draw line closer or farther from the hinge point, the total
travel can be varied.  This is how tapers are set up.
 
   In reality, the drop leaf has a pair of five-foot, one-inch square
aluminum angles screwed to its surface.  One is close to the hinge, and
the other is near the outer edge.  The angles have holes drilled in
them to match the holes in the tabletop.  Half-inch stainless steel
rods with threaded holes in their ends can be positioned at any point
between these angles.  The rods are parallel to the drop leaf surface,
and perpendicular to the hinge line.  Aluminum sliders move in and out
on the rods and are secured with screweyes acting as setscrews.  The
draw lines attach to the setscrews, and the pivot distance is set by
moving the sliders to the correct locations.
 
                             hinges
         ##                    ##                    ##
     ----oo--------------------oo--------------------oo-----
    | ===================================================== |
    | ---||-----------------angle---------------------||--- |
    |    || rod                                       ||    |
    |    ||                                           ||    |
    |    ||                                           ||    |
    |    ||                                           []    |
    |    [] slider                                    ||    |
    | ---||-----------------angle---------------------||--- |
    | ===================================================== |
     -------------------------------------------------------
   
                      drop leaf, top view
 
   Operation:
 
   First, four templates are needed.  I have written a program which
plots airfoils and skin thicknesses on a laser printer.  I make the
templates out of double-sided epoxy board and drill five holes on
2.5" centers to fit the template holders.  The foam blanks are then
cut to size using some crude "T" shaped pieces of metal which I tape
to the sides of the block to use as a guide.  The bottom templates are
screwed to the template holders and the various pulleys and sliders
are set up and tested until the bow travel is proper at both ends.
Then the foam is aligned on the bed of nails and pressed down.  A
piece of particle board weighs the foam down.
 
   The bow is placed into position at the leading edge of the core
and tension is applied.  When the power is applied (supplied by a
variac driving a 24VCT, 12A filament transformer), the bow begins
to move automatically.  The templates have tabs at the trailing edges
to stop the bow when it finishes the first cut.  The upper templates
are installed, the core is pressed down to take up the space just
created, and the second cut is performed.  That's it.
 
   The matching panel is cut the same way, except that the positions
of the templates are reversed to make a mirror-image core.  Leading
and trailing edges are perfectly straight, there is no rippling of
the core surface, and the process is highly accurate and repeatable.
 
   On the down side, the machine as configured is terribly complicated
and took a tremendous amount of time to design and build.  However,
the same ideas could be used to build a simpler machine that would work
just as well, but be a bit more difficult to set up.
 
-Henry

Holly Macro and I thought ours (Channel One Productions) was complicated.

I am surprised the guy didnt use more 1 1/2 " Angle Iron and 16 penny nails...
geez.....


I dont see anything that he did that is better than the ones we are using but
Thanks Kay it is still interesting to see what other people are doing.  


I thought about making it possible to index the templates to the table so that
you dont have to put the templates onto the foam every time but if the templates
are not on the foam but away from it say 1", this is OK if you are cutting a
constant cord core but if it is a tapered core then the angle throws things off
and the template would not be the right size, it would have to be bigger on the
big end and smaller on the small end than the actual core.

    I was worried about doing it, but it worked out great.
    
    This weekend I cut my first tapered wings on the automatic cutter. No
    big deal! I've finally gotten it tuned and all eight cores I cut came
    out smooth. One thing that I've found that wasn't mentioned in the tape
    is that you really want the bottom of the template to be resting on the
    table while cutting With some previous wings I found that the weight of
    the bow was dragging the template down and thinning the wings but this
    set with the template in contact with the table for support worked
    great. The metal sewing bobbins for pulleys are perfect since the wide
    rims hold onto the line even when it goes slack while you're setting up
    for the next cut. 8 cores in 3.5 hours complete from the 2'x8' block of
    foam. That included lunch and no rushing and totally single handed
    operation. Now if I could just get covering them down to the same
    simple operation, I'll be all set. Next step is vacuum bagging...

           
    
       Last week I made a foam cutter based on the article that appeared in
    this months Model Aviation. I had hesitated in the past due to confusion
    regarding a power supply, and what to contruct the bow out of. This    
    design seemed fairly easy and inexpensive so I gave it a shot.
       I basically followed the construction article with the following
    changes:
    
        I cut the piece of 1 by 3" pine to a length of 44" instead of 40".
    The article claims the 40" length will cut up to a 36" core, but I
    found even by lengthening the pine by 4", I can only get about 34"
    of useful cutting area. 
        I used tie wraps between the spring and cutting wire, and between
    the other end of the wire and the shelf bracket arm. This provided both
    insulation from the wire, and some adjustability in getting the wire
    taught.
        I purchased a 2/6 amp battery charger from Sears instead of the
    one recommended ( 2/6/50? ) They claimed the 2/6/50 cost about $40, but
    it was more like $57. The one I purchased was $35. In the article, they
    claim to mostly use the 2 amp setting, so I figured the smaller one 
    would be fine.
    
        Results:
           
            The cutter was easy to construct, and the construction article
     was very good with the exeptions listed above. The hardest thing to
    find was a spring. I finally located a whole wall of them at the local
    hardware store.
            I was hoping to be able to cut up to a 36" core, but am
     currently restricted to 34" by the cutters length. This would be an
     easy fix, just use a longer piece of wood. I am limited to about
     a 30" core by the power supply ( set at 6 amps ). It will cut a 35"
     length, but it is pretty slow. It would seem a 10 amp setting would be
     about right for 36" cores.
        
         Total cost:     Battery charger       $ 35.00
                         2 shelf brackets      $  3.00
                         1 by 3 by 8' pine     $   .88
                         spring                $  1.00
                         Nichrome wire         $  1.75
                         Nuts, bolts, tie wrap $   .50
                         2 alligator clips     $  2.00
                         1 roll electrical tape$   .75
    
                                   Total       $ 44.88
    
       As you can see, anyone with an appropriate battery charger hanging
    around can make the cutter for about 10 bucks.
       I had a lot of fun making the cutter, and have experimented with
    scraps of foam. Now to locate some foam, make some templates, and
    cut some cores. 
    
           Next step: Vaccuum bagging
    
                                
     

    For people in eastern Massachusetts, I have located a place that
    sells lots of types of foam.  (Actually Harvey Tomasian (sp?) told
    me about this place.)

            Sterling Insulation, Waltham, MA  617-894-7050

    The expanded bead "white" foam is available in sizes up to 
    24"x48"x96"  (2ft x 4ft x 8ft)  for $192.00.  Smaller sizes are
    proportionally less - they will cut to order.  
        Ex: 2"x24"x48" = $4.  (approx.)

    They also carry "DOW flotation billet" (one form of "blue" foam)
    largest size 10"x20"x96" for $52.  1.8 lb./cu.ft.  Again, they will
    cut smaller to whatever size you specify and the price will be
    proportionally smaller.  (You can compute an estimated price based
    on cost per cubic inch.)

    Typical "blue foam" is 1.8 lb/cu.ft. - max size 4"x24"x96" for
    $19.20.  Custom smaller sizes are also available...

    They also carry "DOW greyboard" which is what Weston Aerodesign says
    is the best for making wings.  (I forgot to get specifics...)

    When I called, I spoke with Carol and she was helpful and
    knowledgeable.  She knew the densities of the various foams, etc.
    and spent quite some time with me and all my questions.

    Next week, Kevin Ladd and I are planning a long lunch trek to them
    with his truck to buy a bunch of foam... 

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

    Re: .83
    
    What you want to try for is the coolest wire you can get to pass
    through the foam. You know you've got the temperature right when you
    have "angel hair" on the core afterwards. You really need a variable
    transformer (model train style is what I use) to get to this level.
    this also save you if the wire doesn't pull totally smooth along the
    template.
    
    Re: .84
    
    Is there a quantity discount or doesn't it matter in the truckload
    range? I'd be interested in trying some of the grey foam. Let me know
    when you're heading down.

RE: .85
    Jim - they didn't mention quantity discounts.  I suspect there
    are no quantity discounts.

                                - Dan

    The August 1991 issue of Flying Models has an article on building foam
    cored wings.  The article is worth the price of the whole magazine.
    It covers:

    	honeycombing (and the facilitating tools),

    	wing rod socket construction,

    	knife-edge carbon spars,

    	gear and servo boxes, and

    	control surface issues.

    The writing is terse, but I think I learned a few things.

    Alton

    I cut a bunch of wings this weekend on my automatic cutter. Since they
    were all the same, I built a jig with the templates screwed to the end 
    and just kept popping foam into it and did a bunch all at once. These 
    wings also call for a fuselage cutout and some center section spars. I 
    made a little 18" bow and it worked wonderfully. I've also had trouble 
    with stretching of nichrome and stainless steel leader so I tried some 
    .016" braided steel cable (C/L flying wire) which I've been using for
    pull-pull cables. It worked great. Once things were set up, production
    was quick and easy.

    I'm still in foam cutting mode and came up with an interesting, foam
    saving method. I've got a double taper (leading and training edge
    taper) wing core to cut that I want a through the wing spar on (my
    P-38). When I cut single taper wings I always cut the blanks so they
    interleave to make a rectangle (with a diagonal line across the middle
    to make twin blanks). If you consider the spar as the perpendicular
    straight edge, you can cut a leading edge blank and a trailing edge
    blank and then butt the straight edges together. A couple of pieces of
    Masking tape on the top and bottom of the blocks and away it goes with
    a nice straight spar seam for free. Don't forget to remove the spar
    thickness from the templates at that point to compensate for the spar
    you'll add in later.
    
    Another challenge that I've had is getting >2" cores cut out of the
    foam available locally. I can get custom sizes at the local insulation
    supplier but I thought this might work and actually add to the
    strength. Cut double the number of blanks you need and stack two high
    and cut the core with the seam through the center. When you go to build
    with them, put a piece of fiberglass cloth in the joint with epoxy and
    you have a wing strengthener built in. I haven't tried this yet but I'm
    going to in the future. Can anyone see any problems with this?

    Hey Jim, how about a picture??  I read through that a number of times
    and I still can't figure out what you did...
    
    

    Sure, how about a picture... There's one on my desk blotter, does that
    help 8^)
    
    
     / leading  \ / trailing edge \
    +------------------------------+
    |  \         |           /     |                                 
    |   \        |          /      |                                 
    |    \       |         /       |                                 
    | 1   \   2  |   3    /   4    |                                 
    |      \     |       /         |                                 
    |       \    |      /          |                                 
    +------------------------------+
              \ actual /
                 wing
    
    The spar goes between the leading and trailing edge pieces, full height
    and full span. Blank 2 & 3 define the actual wing and 1 & 4 will make
    an identical block.
    
    Second idea:
    
    +-----------------------------------------------------+
    |          ..__---------_________............         |
    |   .___---                                  ------   | <- Block 1
    |___|______________________________________________|__|
    |   |                                              |  |
    |   ---..___                     _________.....----   | <- Block 2
    |           ---..._______...-----                     |
    +-----------------------------------------------------+
    
    Cut it out like you have a 4" block and glue block 1 to block 2 with
    epoxy and a swatch of fiberglass cloth the size of the core blank. You
    might even be able to do this as a preparation step to the blanks and
    then you truely WOULD have a 4" high blank.
    
    

>    <<< Note 56.91 by ZENDIA::REITH "Jim Reith DTN 226-6102 - LTN2-1/F02" >>>
>                        -< 2 pictures worth about $.02 >-
>
>    Sure, how about a picture... There's one on my desk blotter, does that
>    help 8^)
...    
Didn't help me.

I think Tom T and Jim R both went to the same school.

The last time Jim did this to me I had to show up at Acton with
some pieces of paper and tape.

OK - I only care about the first problem - the saving of foam with the double
taper.

I assumed that was an end view of the foam block but I couldn't make
since of that with the "actual wing" part underneath.

Perhaps a black and white photo scanned in and digitized and converted
to post script?

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

    Kay,
    
    That's a top view of the piece (blank) layout on the slab of foam.
    Blocks 1 and 2 are the section forward of the spar and before cutting,
    make a rectangle on the block. Blocks 3 and 4 are trailing edge pieces.
    Block 2 and 3 define the wing layout when viewed from above. The
    straight outside edges of 1 and 4 define the spar position of the other
    panel. The diagonal between blocks 1 and 2 is the leading edge and the
    diagonal between 3 and 4 are the trailing edges. The top of blocks 2
    and 3 is the root rib position and the bottom (where it says actual
    wing) is the tip rib. Otherwise, bring paper to Acton on wednesday 8^)

    I think I know what Jim was trying to say so I'll attempt to
    translate from Reith-ese to English.  :-)

    Imagine a normal foam core.  Now make two vertical cuts where the
    spar goes.  This "foam spar" rectangle is the piece that is normally
    thrown away and replaced with a spruce/balsa/glass/kevlar spar
    structure.  The front and rear portions of the foam core get glued
    to the spar before sheeting and/or vacuum bagging.

    What Jim is saying is, instead of cutting out the spar section to
    throw away, why not cut the front and rear portions seperately. 
    This way you save the amount of foam where the spar goes.

    Stated more accurately: Cut a foam blank that has the correct top
    view from the leading edge to the front of the spar and another foam
    blank that has the correct top view from the rear of the spar to the
    trailing edge.  Then, tape these two core pieces together by placing
    tape along the top and bottom.  The areas where the spar will go are
    now touching each other.  When you make your airfoil templates,
    remove the section in the middle where the spars will go so they are
    the correct length.  Now, cut the cores as you normally would.

    OK, now who will translate from Miner-ese to English.  :-)

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

    Is that paper I hear rustling down there in BXB?? 8^)
    
    My other reason for doing this is that I have a hard time cutting the
    spar joint accurately after the core is cut but can manage pretty well
    on the blanks.

    Slight progress...
    
    I've been collecting materials for the last few days and really not
    making much progress. I started making templates for cutting the second
    planes wing cores last night and did verify that the wings are a 10"
    SD7032 root, 7" SD7037 at the wing/tiplet joint, and a 4" SD7037 at the
    tip. I managed to get the root top and bottom templates made. I did
    something a little different with these. Someone at a local hobby store
    got talking with me about core cutting. We got off on templates and he
    stated that he made 1/8" ply templates with a very thin piece of music
    wire as the top surface. I used the music wire method on these (.032 I
    think) and I'm very pleased with the results. I'll finish the other two
    template pairs and cut some cores this weekend. I'll report back on
    monday.

>       <<< Note 1404.7 by RANGER::REITH "Jim (RANGER::) Reith - LJO2" >>>
>                            -< Wing core templates >-
...
>    stated that he made 1/8" ply templates with a very thin piece of music
>    wire as the top surface. I used the music wire method on these (.032 I
>    think) and I'm very pleased with the results. I'll finish the other two

Did you just glue the wire to the plywood edges?  Did you cut a groove?
Did you have to allow for the wire thickness?

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

    Ok, here goes...
    
    You don't have to allow for wire thickness with the type of cutter I
    use since down always remains down and the wire is on the top of both
    the top and bottom surface templates. All the wire effectively does is
    raise the cut (by the wire thickness) in the blank (both top and
    bottom).
    
    You can groove the template but with the thin wire I used, it would
    disappear into the template pretty quickly. Last night I just glued it
    onto the template.
    
    I did find that I needed to gently bend the wire to the approximate
    shape and then I put 90 degree bends at the ends (beyond the useful
    airfoil). I use a pressed laminate material that's about 1/8" thick so
    I drilled holes at each end (slightly farther apart than the wire) and
    clipped the 90 degree bends into the holes. This held the wire onto the
    top of the template and I then glued it onto the center of the width
    with CA (and skin). I scraped the top surface with my xacto to clean it
    up and it gave me a nice smooth surface for the cutting wire to travel
    on.
    
    I've heard of others using teflon tape on the cutting surface but this
    seems to be a pretty good method for my low-tech means. The wire also
    matched the kit cores quite well so I'm pretty happy with the outcome.
    I'll let you know how they worked out on monday.

    Ok,  how do you guys do it. I'm  cutting a set of FF wings for a guy
    out of blue foam and the damn stuff is really a banana  in  disguise.
    If I don't  cut the wing centered in the blank, the stresses from
    extruding give it a great curve. Might be a great way to simulate an
    elliptical  wing but that isn't the intent here. Am I doing something 
    wrong here or is that the nature of Dow blue?

    
    
    Jim,
    	Here's a trick Eric and I used when we were cutting wings with the
    white foam that may work with the blue. When we cam across an
    elliptical core such as you describe, we would bend the core in the
    opposite direction and using our hand, gently stroke the core spanwise.
    
    Straightened the sucker oout every time!

    He told you that was a core? 8^)
    
    Actually, cutting them centered out of the blank work fine but I was
    hoping to get both halves out of each blank by cutting closer to the
    edge. That's when I went/got bananas.
    
    They could be flattened when bagged (I knew a girl who...) but these
    are for someone a little less hitech who intends to sheet them with F77
    and I'm not sure you can hold, bend, sheet, smooth a banana core with
    just two hands.

    
    Jim,
    	Once you straighten the core using the method I described, it stays
    straight. You don't have to do anything special to keep it that way.
    
    :-) (Boy it's rough keeping a "Straight" face on this one!)
    
    

    I know what you mean 8^)
    
    The problem with the extruded foam is that it's actually expanding once
    the outer surface is removed due to the internal pressure. The core is
    bending due to the foam being allowed to fully expand. The only other
    thing I could think of doing would be to cut the outer surfaces off the
    blank and let it "relax" before doing the actual cut. It just seems
    wasteful to cut a 1/2" core out of the middle of a 2" block. Never had
    to do it with the white since the entire log is extruded and the the
    block are sliced out.

    I would like to start cutting stabs from foam.  Does anyone know
    a good source for an appropriate power supply?  What is a good way
    to make a bow to string the Nichrome wire with correct tension.
    
                                              Thanks,
    
                                              Jim

Hi Jim.

There's a lot of good info in 56.*

Best thing to do is to send mail to microw::phillips and request the Channel 1
foam cutting video from the DECRCM library. Cost you a buck to borrow. With it
comes a set of plans for their cutter. That's what I've been using to crank out
cores.

Lamar (microw::Phillips) can also give you the info on the power supply he's 
using from Radio Shack. Stock, off the shelf stuff.

The Channel 1 bow is a hardwood H with the wire across the top arms and a screen
door spring stretched across the bottom arms. I have one end of the spring hooked
to the arm and the other end attached to a small chain. I have a nail on the 
other arm and stretch the spring and then drop the appropriate link over the nail.

Some people like stainless fishing leader, I've used Sig's nichrome but most 
recently I've been using old C/L flying wire that I've had hanging around the 
shop. This is in the .015-.017" range and has worked real well. It's braided so 
it doesn't stretch like the others did and I've been cutting so serious numbers 
of cores recently.

For stabs you don't really need a bow. A nail and a single template will do. This 
is demonstrated on the video.

    
    
    This is a little out of the ordinary but... I'm building an ultralight
    called the Mitchell U-2 Superwing. From the main spar forward is foam
    ribs and from the main spar back it is wood. What I have to do is hot
    wire these foam ribs. The only problem is I need to cut a length of
    93" which is almost 8 feet. I have read most of this note and
    everything is about 5 feet, and a battery, AC transformer, or a battery
    charger has been used. I am looking for some advice/help to cut 93"
    of ribs not a solid block. I am going to get the steel leader and use
    that, the bow Ideas all look doable it's just the juice I need help
    with. Thanks and yes...I am still an RC Pilot. I bought this still in
    Kit form with engine, wheels, prop, even the covering everything for
    1,000. I couldn't resist.
    
    Bruce

Bruce, I don't think you can do it accurately. Wire sag is going to be the 
biggest problem. Why does it HAVE to be all cut as a single piece of foam? 
If you break it down into 3 or 4 pieces, it will be much more managable. If
its because you don't have the intermediate templates, cut a 2' piece and 
the slice it into thirds or quarters and use the cut faces to make intermediate
templates. That's what I had to do with the 4' Alcyone cores when I found I 
couldn't accurately cut them as one piece. Wire tension to reduce sag is going 
to stretch the wire and cause breaks.

    
    The leading edge is tappered and I only have templates for each end.
    
    Bruce
     

    Somewhere in here, there is a discussion of building an AC transformer
    for about $25 from Radio Shack.  I built one and it works great.  I
    also use a Dremel moto-tool variable speed box (the one that plugs
    in-line with the AC power) to adjust the output.  Seeing that I am only
    using about 1/2 power for 4+ feet, I think the whole system will give 
    you enough to cut 8'.
    
    Does anyone have the formula for the amount of power that would be 
    needed for 8' of wire??
    
    My biggest worry would be getting enough tension on the wire..  As it
    heats, it will expand and if the excess is not taken up by the bow, you
    will have a serious drag problem.  This would result in a different
    airfoil in the center of the foam versus the tips.
    
    What do you mean by "I am looking for some advice/help to cut 93"
    of ribs not a solid block"??  You always start out with a block of
    foam.  Do you mean that once the airfoil is cut, you will slice the
    results chordwise to obtain individual ribs??  If you need individual
    ribs cut from the foam, then you don't need to cut 8', you can cut
    twice at 4' or whatever other increments you want.
    
    What is the final wingspan of the ultralight??
    
    Hope this helps..
    jeff
    

    (Notes collision, jim!!  At least we were consistent!)
    
    Not to put a damper on this intriguing discussion, but what do the
    instructions say??  Or the kit manufacturer??
    
    jeff
    

Ok. Take the two templates you have and cut a section that is only about 2 
feet long out of scrap foam. Cut this core in half chordwise (at the 1 foot 
mark) and then these halves in half again. You now have 4 sections of wing 
with the seams representing the missing templates (to be traced around as 
needed) The smaller the scrap section (within reasonable limits) the more 
accurate the intermediate templates will be. If you can cut 4 foot cores 
accurately, you only need to cut it in half. I'd recommend going to quarters 
and taking your time.

    
    
    Maybe this will help, If yu take an RC wing with bulsa ribs looking
    at the ribs foward of the main spar, the rib area where we would sheet
    with bulsa. (the wings have not been joined together yet) Both outside
    ribs are plywood and all the middle ribs are foam and the wing is
    tappered. I have to use the two outside ribs as templates to get the 
    proper cut.
                           foam  ribs--->|   |<---plywood ribs both ends
                                 |   |   |   |
                         |   |   |   |   |   | One of four sections.
                     |___|___|___|___|___|___|
                Both rib ends are plwood all ribs in the middle are foam
    I have four sections to do and the total wingspan is 34 Feet.
    
    Bruce                                                               
    

    If the ribs are spaced, most of the space is air and the sag might be
    manageable.  I'd try cutting, but do it slowly.  Make a BIG bow and get
    an experienced helper on the other end.
    
    Charlie
    

    
    Charlie, what would work best a battery charger at 14v or a 120AC 
    transformer at 25.2V 2A refering to note no. 56.35?
    
    Thanks
    Bruce
    

    I'm not sure what you're asking, but if you double the wire length, you
    need to double the supply voltage to get the same wire tempature. 
    Another way to put it is you need about the same current no matter how long
    the wire is.  If you use a fixed supply, you need some way to vary the
    voltage with a light dimmer or a variac.  It is important to get the
    right wire temperature for the cutting you are doing.  I would suggest
    that you try to get some experienced foam cutting help to avoid having
    to make several junk sets before getting it right.
    
    Charlie
    

    
    
    Thanks Guys That was a big help, I'm going with the .025 stainless wire
    the light dimmer and 120VAC 22.5 DC 2A transformer from Radio Shack
    with a 2 amp Fuse (ref. .35).   I've seen the tape that Eric and I
    think Jim or was it Dan did so I guess I'm all set!
    
    Thanks again
    Bruce

I've been trying to come up with a reasonable way to do this but haven't been 
able to really see a good way. The sag issue is going to be a big factor. To 
Minimize the effect of sag, extend the line of your TE of the templates so 
that when the ends pull out first, the wire will pull out straight near the 
center and you won't lop off a section in the center. The only idea that I've 
come up with is to use a set of handles at the end of the wire and eliminate 
the bow entirely. Just two guys pulling on the handles to stretch the wire 
while it follows the templates. A couple of 1" dowels would make reasonable
handles and as long as you clip the power onto the wire inboard the handles, 
you won't get burnt. If you look back near the beginning of this topic there's 
a discussion of dividing the templates into "stations" which are percentages 
of the overall templates. You call out the stations as you're cutting to keep 
both of you in sync while cutting. Sounds like a challenging project.

    
    Hey Jim!! that is an exellent idea I'm glad you thought of that. That
    is alot easier that a bow. 
    
    Once I get the transformer and the other material and do the job I'll
    get back and let you all know how it went.
    
    Thanks again,
    Bruce
     

Bruce,

One other suggestion that might be obvious but I didn't want to leave it to 
chance. When you cut the cores, start at the leading edge and cut back towards 
the trailing edge. Wire sag and drag will be at it's minimum when you first 
start to cut and at it's maximum when you finish. If you start with the leading 
edge you'll be most accurate at the tightest curve and then if you extend the 
templates in a straight line beyond the trailing edge, you'll pull the wire out 
and the middle which is dragging behind will come out in the same direction. If
you stop the template at the trailing edge, your bow/wire will tend to drop and 
the center section will scoop out and ruin that part of the wing.

Better to state what might be obvious than to make you discover it through 
experience.

    
    
    Called Radio Shack last night and they only have a 120VAC 12.5 DC 1A 
    for 10.95 Does anyone have a part no. I could use to order from? If not
    I'll have to by two and run them in series (sp).
    
    Bruce

The 25.2v CT 2A transformer is part number 273-1512 and is $9.99. This is the
one I used to build my power supply for my foam cutter.

-Lamar

The wire won't sag if you stand it on end.

You need a 96" ceiling (garage) and would have to fiddle
to make the rig - but no sag.



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

    I disagree.  Wire sag doesn't always go "down" due to gravity.  I
    think it should be called wire drag.  Sometimes it goes down,
    sometimes it goes up but primarily the center is lagging behind the
    ends.

    I think that high tension on the wire and cutting fairly slowly is
    the best bet.  (But don't cut so slowly that you end up with gouges
    where the wire stops.)

    Maybe Jim Reith (who's cut LOTS more cores than me) has some input
    here... ? 

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

Wire drag is how I'd describe it. The only place you have to worry about wire 
sag due to gravity is before you enter the foam. If gravity sag is an issue, 
your bow isn't tensioned. Always tension your bow when warm since your wire 
will expand when warm. Wire drag is due to the foam pulling back on the wire 
as the ends get moved forward. You need to cut with a pretty cool wire to get 
good results and this means that there's more wire drag.

My recommendations are earlier. The bowless twin handle method should work as
well as a manual bow. Sag/drag might be less of an issue with the space between 
the ribs when you're cutting. I've had trouble with sag/tension when trying to 
cut 48" cores. Practice/test your technique on cutting a 1/16" slice off the
top of the rib blanks several times with a couple of straight edge templates.
This is the practice recommended in the NSP catalog section on cutting foam.

I talked to Mr. Feathercut at the Nats and saw his system. It's a nice system 
if you want to buy one off the shelf. Seems like a lot of money for the guy that
just wants to cut a few cores for personal use. Seems like it would be a better 
purchase for a small group/club since the setup is pretty quick and it's 
portable.

    
    
      I have all the material for cutting my wing ribs on my ultralight.
    Can someone talk about why the need for cool wire vs. hot? If you have
    wire drag with cool wire wouldn't it be better to have a warmer or
    hotter wire? Also what happens when you stop in the middle of your
    cutting Will this create goughes in the foam?  Please someone educate
    me.
    
    Thanks
    
    Bruce
      

You need an even draw through the foam to get a good cut. Too cool and too 
hot are both problems. You can't stop part way through a cut since it will 
cause a ridge/gouge when the wire reheats in place.

Set up the wire so you get a reasonable cut on a piece of scrap and then give 
it a try. If you are getting "angel hair" on the surface, your temp is about 
right.

    I'd do plenty of practicing on scrap foam before starting for real. 
    Get a feel for it or you will get bad ridges due to changes in cutting
    speed.  It does take practice to get it right.
    
    Charlie
    

    
    
    Does anyone have any suggestions around blowing fuses?? I blew about 4
    fuses last night they are 2A fuses SB. Everything is wired according to
    note no.35, And yes I am turning the dimmer up slowly. 3A or 5A fuses??
    
    Thanks for the help
    
    Bruce
    

I just built a new supply and it differs a bit from .35

Same transformer but I substituted the 3 amp circuit breaker they sell for the 
fuse. I also found that the output dropped to 19 volts when the dimmer was put 
into the  circuit so I have a DPDT switch which swaps out the dimmer for a 
direct 120v ac in in cases where I need the extra boost. I can heat my 5' bow 
to cutting temps with the 25.2 volt output. I have yet to pop the circuit 
breaker so you might want to try a 3 amp slo-blow fuse next. You really just 
want it in there so you don't melt down the transformer with a direct short 
across the outputs.

Here's how I set up the bypass DPDT switch

			3=======4	Jumpered for bypass

     from transformer --2	5-- to hot output

    input from dimmer --1	6-- output from dimmer

The other side of the transformer goes directly to the other output. In the up
position you have direct contact to the transformer. In the down position you 
go through the dimmer. Make sure you get a DPDT switch that is rated 3 amps at 
120vac (the one I got is rated 6) If your bow is longer than 5 feet, you'll 
need more voltage. With GREAT care, you might be able to run it direct off the 
dimmer but I'd be REAL careful doing this.

           
    
    Will a 4A circuit breaker be to much??
    Dan, did you say you are using a 6A C.B.?
    
    and again Thanks
    
    Bruce
    

I doubt if 4 amps will be too much. It really depends on the length of your 
feed wires to the bow (I use 16 gauge zip cord) and the resistance of the 
cutting wire. You want to use heavy enough gauge feed wire so that it's the 
cutting wire that gets hot.

    
    
    1....1....2....2....3.hold it..3....4.ok...5  It went very well!!
    it surprised me. There were a couple of things that I would change like 
    putting in a templete to cover the leading edge stringer notch and then
    do the notch last. but over all not to bad. A little sanding/trimming
    and it's ready for the 1mm plywood. I thank you all for your HELPFULL
    advise. I don't know what or how with out your help. One last question
    how often do you change wire? We made about seven cuts and the seventh
    one was very slow...we changed the wire and the rest went easy. Do you 
    clean it ?? What?  Also the 4amp cicuit breaker tripped about 3 times
    Should I go with a 5 or 6 amp? The transformer was warm not hot.
    
    Thanks again guys
    Bruce 

Great news! I'm glad to hear that you were successful. I don't change my wire 
until it breaks but I due warm it up and run a wad of paper towel along it. 
If all you're getting is foam melted onto it, it shouldn't really need to be 
changed.

You could try a higher amperage breaker or put in a 10 amp fuse. Like I said 
before, it's really just to protect in case of a direct short

Since I didn't want to spend $20 on a sheet of Formica and couldn't find any 
"scraps", I broke down and started using model plywood for my latest batch of 
templates. I am using 3/32" thick which gives me the added stiffness without 
having too much thickness to drag the wire along. I glued the laserprinter 
output templates to the wood with Titebond and after they were dry I cut them 
out on my Dremel scroll saw. A quick touchup with a sanding block to fit the 
template lines and then a bevel of the back to reduce the top thickness and I 
was ready to go. These templates worked well and I'm very pleased with the 
overall production. I cut the 12"x48" sheet up into strips 2.75" wide (I use 
a 3/4" base and 2" foam so this guarentees my cut will be in the block) and 
was very pleased with the overall procedure. I'd recommend this for anyone 
not able to find Formica for your templates (you've probably already got the 
plywood in your shop)

    Jim,
    
    I used ply templates just as you are doing...with the exception that I
    would rub a yellow carpenters crayon over the edges of the templates.
    
    We are talking SLICK.  Never had any problems hanging or burning the
    temps.  They seem to get "broken-in" after a few cuttings.
    
    Have a good day (or else),
    
    Chris
    
    PS Yes, Dan Miner, there is a fungus among us   :-)

Ran off a half dozen SD7037 Chup wings last night using the templates. No 
problem. The templates were quicker to make since it took longer to smooth 
the other material I was using. Yellow carpenters crayon? Sounds a lot 
simpler than digging out the butchers wax. Thanks for the tip.

While we're talking tips...

I tend to make a small V slot in front of the useful portion of the template.
This holds the wire in place while you align the foam blank in the jig (my
templates screw onto a solid base and rest against the backstop of my table 
and don't get pinned to the foam block). I then use a 3'-4' length of 2"x10" 
as a weight on top of the block to keep it in place. This is heavy enough to 
be used all by itself so it's a single motion to take the weight off when 
switching blocks. Once everything is set, I lift the wire out of the groove 
and allow it to ride up the template to the block. I then just have to hit 
the switch on the power supply and away it goes. Reloading becomes... turn 
off supply, remove weight, remove block, reset wire into grooves, load fresh 
block, replace weight, reset wire against foam, switch supply on. I only use 
the pin on the weighted arm when I'm setting the taper or swapping templates.

I've always had problems with the pull strings for my cutter. Originally I
used kevlar line and wrapped/tied/glued it to small screw hooks. Being 
usually in a rush when things went wrong, I'd typically just retie the pull
strings if they broke. Over the past few cutting sessions I noticed a few 
recurring ridges regardless of the templates I used. I noticed that they 
occured when the knots went through the pulleys. Last night I solved all 
these problems and a few others. I replaced the Kevlar line with some 
extra braided fishing line (50 pound test) that I had left over from an
upstart I made. I also came up with the perfect attachment for the string 
to the cutting wire. C/L leadout clips. These clips open and close (the 
screw hooks could fall off the wire when you weren't looking) and you can
easily attach the string with a simple Lark's head knot. Take a loop near
the end of the line and pass it through the eye of the clip far enough so 
you can put the clip through the loop and then pull it tight. The loop 
lines will tighten on the outside of the two ends and hold them under 
tension but if you push on it you can still loosen it to adjust length or 
replace the string. Makes it simpler than just tying a knot in the broken 
string so there won't be anymore lumps passing through the pulleys.

    I successfully cut my first foam cores this past weekend(finally).
    Now that I am thinking about sheeting the cores, I am wondering
    how to do the leading edge(I was planning on using fiberglass
    sheeting).
    
    The article I have read from Silent Flight addresses the issue as 
    follows- "The leading edge should be a sharp point, so cut it off
    3mm back from the true leading edge marked on the foam, to allow
    for fitting later."
    
    It then goes on to say- "Fill the 'v-gap'-formed by the chopped off
    leading edge of the foam core  and the bottom skin extending beyond
    it- with carbon fiber tows.  It isn't easy to estimate the amount
    required, but any excess will tend to squeeze out when the top skin
    is added and the wing pressed."
    
    Does this method sound viable?  Does anyone know any other methods
    of sheeting over the leading edge?  What diameter tow should be 
    used for spar caps and leading edges?
    
                                                         Thanks,
    
                                                         Jim
    

As far as I can tell you're off in uncharted waters on this one. Have you 
prepared the sheeting yet? Did you use a vacuum over plate glass to get it 
uniform? How was the weight? Is a CF leading edge necessary for what 
you're building? Is this for the Waco? The leading edge isn't going to 
provide a lot of extra strength over what the wings spars should. Plus a
stiff leading edge and not as stiff trailing edge (due to thinness) might
cause some interesting flex/twist problems. I would think that a small 
hardwood dowel and a little CF would be a simpler way to go (I guess I 
need more project background)

Does the leading edge get blunted or left sharp?

    Welcome back, Jim!
    
    Let me try to clarify the situation.  The commercial kits I have built
    have been sheeted with Obechi or Balsa.  The balsa or obechi leading
    edge is glued on.  I then use a sanding t-bar to fare the wing sheeting
    and leading edge into a smooth contour duplicating the airfoil.
    
    I think adding a wooden leading edge to a wing sheeted with fiberglass
    would be hard to finish. It does work fine if you sheet with balsa or
    obechi, however.
    
    The wing I am working on is not the Weston wing, which came presheeted
    with kevlar.  Weston wraps a piece of spectra cloth around the leading
    edge and then vacuum bags the wing with kevlar.  The resulting leading
    edge is not too impressive(just ask Anker)!  To establish the leading
    edge, you must cut away the kevlar flashing and then wrap the leading
    edge with plastic tape.  It's not very pretty and doesn't seem to
    precise.
    
    The wing I am building(RG15) I had hoped to sheet with fiberglass
    cloth using a method outlined in a 4 part article written by a 
    British F3B flyer(Steve Macken) in the magazine Silent Flight.
    They prepare the wing sheeting cloth as follows- "The skins are to
    be first layed up with epoxy on flexible plastic release sheets,
    typically between .5 and 1mm thick with a good surface finish,
    then these laid on each side of the core and pressed.  The plastic
    sheets are treated with a non-silicon based release agent and sprayed
    with acrylic paint to minimize pin holing."
    
    Jim-it appears to me that they are using a "wet" layup method versus
    laying the cloth up on a glass plate first then applying the "stiff"
    dry skins to the cores.
    
    I would like to forward you a copy of this article for your perusal/
    criticism of the method.  If you are agreeable send me your address
    and I will mail you a photocopy of the article.  It is interesting
    reading and appears a viable alternative to vacuum bagging.
    
    
                                                       Regards,
    
                                                       Jim 

Looks like what you've got is a "press" version of the Mylar vacuum bagging
method. Substitute drafting mylar for your flexible plastic and there you 
have it. Mark Antry covered this method pretty extensively in, I believe, the 
vacuum bagging topic about a year ago. You paint the Mylar and then set up the
glass on it and the paint comes off with the glass. Your finish is as smooth 
as the mylar and everything (covering/painting) is done at once. Most articles
recommend the use of 14mil mylar for the vacuum bagging method. Most of this 
is done over grey/blue foam to avoid the orange peel look of the bead foam. 
This might not be necessary in the press method since you'd be applying more 
even pressure from the outside only.

Drafting mylar (especially the heavy 14mil stuff) doesn't wrap around the 
leading edge too well. That is the biggest drawback to this method. Many people
use an inch of cloth and wet it out and then place it over the leading edge 
before wrapping the regular fiberglass over the mail panel. Unfortunately you 
end up with a point out front which needs to be sanded to the airfoil Phillips
Entry profile. Sanding removes the paint so you need to refinish the LE or
go the quick and dirty route and apply tape over the edge. I don't like the 
tape method because the tape edge creates a trip where you probably don't want 
it.

I saw a local Magic that was Weston built and I was very surprised at his "good
enough" approach. The leading edges were taped (I'll admit the fiberglassing 
of the wing was perfect) and the aileron/flap hinge edges were unfaced (raw 
foam) and just tape hinged (I know this is typical but I still don't like it).

    Is anyone currently vacuum bagging wings, and if so how are you
    doing your leading edges?  I am ready to start sheeting my wings
    and would like to know the best way to do this.
    
                                                        Thanks,
    
                                                        Jim

    
    When I was in CXO two years ago we bagged a pair of ICON wings. We layed 
    a 2" wide pice of cloth soacked with epoxy around the leading edge - 
    tight. We then put the sheeting around the cores and put it into the bag. 
    When you take it out (remember to wait 2 days to let it harden
    completely - at least we had to do) just sand it to shape. The better
    you sand and probably fill the better the leading edge.
    Of corse the leading edge on the core needs to be shaped first. I've
    seen real good results this way.
    
    
    Bernd
    

    Currently I am concentrating on cutting and sheeting stabs for my
    electric stable(ARCUS, CALIBRA, WACO-550).  
    
    I am using the NACA009 profile, as it appears to be the most popular
    stab airfoil for high performance gliders.
    
    I use "female" templates and have had some problems cutting and
    sanding them to an accurate profile.  The stabs are 4" at the center
    tapering to 3" or 3.5" at the tip.  So we are dealing with a small
    template.  Not having a scroll saw makes it harder also.  One thing
    I can say, is old Q-bus grant cards make unbelievably smooth and
    burn resistant templates.
    
    I now see why so many sailplane designs use an all flying stab.  It
    is much easier to construct to profile than a 1 piece with separate
    elevator.  The biggest problem is "burying" a ply hold down plate
    in the foam while maintaining profile.  I have solved this problem
    but it is labor intensive.
    
    The kits tend to come with a solid balsa stab which you sand to
    a symmetrical shape as best you can.  Ships like the Legend use
    a built-up stab for ultimate lightness.  Who knows what profile
    you end up with using these methods.  Hence my move to foam
    construction.
    
    The profile drag of the stab is probably insignificant at thermalling
    speeds but becomes more important at F3B/F3E speeds, where reductions
    of up to 10% may be possible according to Martin Simmons.
    
    I think it is a combination of a bunch of little "nuisance" things
    (wing fairings, accurate profile, sealed hinges, etc), which allow
    a sailplane to go fast without self destructing.  
    
    
                                                        Regards,
    
                                                        Jim

Stabs are tough since they're so small. I'd be interested in hearing your
stories about "pressing" as you go on. Stabs are one area where I think
pressing can work quite well for production. There's simply too much effort 
involved in "bagging" individual stabs. Making up an entire batch and 
pressing them all at once looks like the way I'd try to go. Then you can 
sort them out based on weight. My press would probably revert to a couple 
of flat plates and some books for now

    Jim,
    
       I have been experimenting with sheeting methods.  Currently I
    am applying 1.7 oz kevlar or 3.0 oz glass directly to blue foam
    stabs using Bob Smith thin CA.
    
    The preliminary results look promising, the adhesion is better than
    the vacuum bagged stabs I received from Weston.  The drawback
    is the grain of the cloth must be filled.  I am experimenting
    using red devil spackle and water-based polyurethane.
    
    I will let you know how it comes out.  I may also try 1/32 balsa
    over white foam using a press.  The leading edge would then be
    glued on separately and probably finished with polyurethane.
    
    My needs are difficult to meet- accurate profile, very light and
    strong structures.  The technology and methodology exists to
    accomplish this, mastering it is the problem.
    
    I think there is a lot of room for further experimentation using
    different methods/materials. 
    
    
                                                      Regards,
    
                                                      Jim
    
    

Might want to play with some 1/64" ply as skin too. Doesn't need to be 
filled...

>    I will let you know how it comes out.  I may also try 1/32 balsa
>    over white foam using a press.  The leading edge would then be
>    glued on separately and probably finished with polyurethane.

I did that on one of the pair of wings I bagged for the Lawn Dart.
I'll never use 1/32 balsa sheeting again without a covering over it.

The darn stuff gets holes from landing in anything other than fresh
mowed golf course greens.  Little stubble pokes its way right thru it.

It is the lightest of 3 pairs of wings I have for the Lawn Dart but
I almost never use them because I don't like filling all the holes.

Did you get the NACA stab airfoil out of the postscript airfoil program
we all have?

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

    re: -1
    
    Kay,
    
       The template for the NACA0009 did come from our postscript
    program.  I guess obechi could be substituted for the 1/32
    balsa or the the balsa could be covered as you say.  
    
    Just out of curiousity has anyone built a glider using a
    profiled stab?
    
                                                     Regards,
    
                                                     Jim

re -1 Jim B.

I used an SD8020 for the stab of the Pulsar. I sheeted it woth 1/16 balsa
and also cut some lightening holes(~1" dia.) The reason for the lightening
holes, was to try and cut down of the Pulsar's tail heavyness.

On another note, I had great success vacuum bagging the Electric Breeze's
wing yesterday. The pump only ran for a total of 45 seconds all night!! This
is the best I've ever done(leakage/pump run wise.)  I've got the other wing
in the bag now(went in the bag at 10:00 am) and the pump has only run for 15
seconds. I'll enter more in the vacuum baggung topic later, time to go enjoy
bringing in the New Year!!!!

HAPPY NEW YEARS EVERYONE!!!

-Lamar 

    In thinking about wing construction and finishing, I am wondering
    about making an all molded wing.
    
    I will present my idea, which seems deceptively simple:
    
    1) Cut a core from 2" blue foam, remove male wing core.
    
    2) Spray the 2 remaining female foam blocks with 3M-77 adhesive.
    
    3) Lay a layer of 6 oz. glass in the female foam blocks, followed
       by a layer of 3 oz. glass, followed by a layer of .75 oz. glass,
       wetting out each layer with laminating resin.
    
    4) Take a piece of 14 mil mylar coated with Carnauba wax on one side
       and lay the waxed side face down to the resin coated glass in the
       foam blocks.
    
    5) Place the foam core between the two dry sides of the mylar and
       put in a mechanical press for 24 hours.
    
    6) Remove "mold" from press, removing the core and mylar hopefully
       reveals two ultra smooth wing mold halves.
    
    * This completes the construction of the female mold.
    
    The wing is now molded as follows:
    
    1) After filling any imperfections in the mold halves, coat 1 mold
       half with mold release.
    
    2) First layer in the mold is paint/gelcoat.
    
    3) Two layers of 1.5 oz. glass are now layed in the mold at 45 degrees
       to each other and wetted out with resin.
    
    4) Rohacell foam is next layed in the mold half.
    
    5) Two layers of 1.5 oz. glass at 45 degrees are wet out and layed in
       the mold half.
    
    6) A piece of waxed mylar is now placed waxed side down in the the
       mold half.
    
    7) The male core is now placed in the mold next to the dry mylar
       and the other female half is set on the core.  It is now
       put in the mechanical press for 24 hours.
    
    8) Steps 1-7 are repeated for the other half of the wing.
    
    9) The two wing halves are now joined with a rohacell and
       carbon fiber spar placed between the two halves and again
       placed in the press.
    
    Am I missing something or is this the way to mold a wing?
    
    Comments/criticisms requested.
    
    
                                                  Regards,
    
                                                  Jim
    
    
    5) Two layers of 1.5 oz. glass at 45 degrees are now layed in and
       wetted out.
    
    6) 
    
      

One of the recent soaring columns (Mike Lachowski in MAN) had an article on 
this. They did what you described with a second piece of Mylar in place of 
the female mold preparation step. Basically you prepare a Rohacell and 
fiberglass sandwich between two pieces of mylar and then press it between the 
cores and beds to get the final shape. Some amount of trimming and sanding 
are required to join the halves.

Another method is to build up a layer on the male core and then continue until 
you have a rigid mold and remove the foam (melt it out). This is basically your 
method with a stronger mold. This can take a lot of preparation of the mold 
surface.

I have also heard of building a wing as normal and then dissolving the foam out 
of the center once cured.

    The latest issue of RCSD had a couple of articles about finishing
    vacuum bagged/pressed skin wings.  Finally the issues of leading
    edge and tip finishing are at least being addressed/acknowledged!
    
    From my own experimentation and inspection of a commercially available
    (WESTON AERODESIGN) vacuum bagged wing, I have come to the conclusion
    that many of the benefits of bagging/pressing skins are negated by
    the crude leading edge which results.  The articles I have read
    sidestep the issue.
    
    Over the past 2 months I have done a lot of experimentation with
    foam and covering techniques.  I have learned a lot, by making
    mistakes.  I need to see the leading edges and tips of some other
    composite covered foam wings and see how they finish.
    
    Fairing an epoxy leading edge into a glassed foam core seems very
    difficult to do without destroying the wing surfaces with the sanding
    block.  Since glider wings tend to taper from root to tip in thickness,
    a sanding template seems impossible to use.
    
    Does anyone know if any of the videos covering bagging go into detail
    on finishing leading edges?  
    
    
                                                             Regards,
    
                                                             Jim

    I just called a local art supply house to inquire if they had
    14 mil Dupont mylar.
    
    They checked an said they had a roll of 15 mil 40"x25' for $9.00.
    It was not Dupont.
    
    Weston charges $5.95/ft. for 47" 14 mil Dupont mylar.
    
    CST charges $13.00 for a 24"x72" piece of 14 mil Dupont mylar.
    
    Are Weston and CST charging exorbitant prices or is Dupont mylar
    that much better?
    
                                                   Thanks,
    
                                                   Jim

The drafting supply place I went to had a 100' roll for $210. They wouldn't cut it 
up. They still have it. The price you were quoted is excellent. I hope the Cashier 
agrees with the clerk 8^)

Acetate is much cheaper and has a good surface for doing this. It curls a lot more
when initially taken off the roll. I haven't gotten the heavy mylar yet so I can't
tell you the difference.

    In Weston's catalog he says to accept no Generic substitutes for
    Dupont 14 mil mylar.
    
    He has a lot of superlatives in his literature, it is hard to know
    who to believe.
    
    This is why it is hard to be doing this stuff alone.  You have to
    make all the mistakes and waste the money.
    
    I think I'll try the Art store mylar because it is priced so good.
    
    I'll post my experience.
    
    
                                               Thanks,
    
                                               Jim
    
    BTW- Good luck with your core cutting business, I'll be looking for
    your ads!  Are you using 1 part male or two part female templates?
    Just curious.

I'm using two part templates with the wire always riding on the upper 
surface. I guess that would make it female on the lower and male on the 
upper surface. (the bow is suspended by the wire riding on the templates)
I cut the bottom surface first and this lets the foam settle into the
bed for the second cut. This gives you better control on the thickness.

I'm about to try the freehand stab cutting using one template and Leroy 
Satterley's flip up template method. You have two templates as described 
above but they are connected beyond the trailing edge. When you finish 
the bottom template you pull back the wire, flip down the new template,
and cut the next surface. The stab method uses a single template and you 
tie the end of the cutting wire down where the leading and trailing edges 
cross (obviously only works for tapered stabs). This has the added 
advantage of only requiring one template to be made, half the initial 
work, and the higher taper sections don't cause the bow to gyrate too 
much on the normal two template cutter.

Thanks for the wish of luck. It only takes time. I hope to purchase some 
"spare" time at the WRAMS show so I can get my own building done 8^)

There is a 1"x1 column ad in 3/93 RCM (for the Gremlins) and a 1/4 page 
in the 3/93 RCSD for glider wing kits. I'm also investigating Quickee 500 
wings. Dodgeson was right in his article in the 1992 NSP catalog. It does 
take something out of the "hobby" aspect of it 8^(

    Jim,
    
       On a separate topic, did you see the new Golberg Finesse pattern
    ships designed by Dave Patrick in the new MA?
    
    The general use of composites is on the horizon for IC ships.  I
    think the Finesse is only the beginning.  Foam wings and fiberglass
    fuselages will be common soon, I think.
     
                                                      Regards,
    
                                                      Jim

I spent about an hour last night talking to Scott Justice (associate VP, 
District 6) and he told me about a new Quickee 500 ship that is all 
composite including hollow composite wings similar to what we're seeing 
in gliders these days. Seems the demand has brought out some technology 
in these arenas.


BTW: Fiberglass fuselages and foam wings are commonplace in Pattern. 
It's sport fliers that haven't caught up. Composite wings are new.

I have some of the 14mil Dupont mylar from Weston.  I didn't buy very much 
(4-5 feet as I recall) and I haven't used it yet.  It's difficult to cut into 
something that expensive when you know that a slip of the knife (or sissors)
will make it scrap.

Besides, I haven't had much time for building in a year or so anyway.
When I get some more time and motivation (yeah right!), I'll let you 
know how it works.  In the mean time, if any of you around here want to
see it, come on over to my house...  (Central Mass.)

				- Dan

    I remember reading in a note a long time ago, the venerable Al Casey
    stating that scratch building offers no savings over building a kit.
    
    I now sure know what he was talking about!  
    
    Over the last few months, I have purchased lots of materials(Kevlar,
    Fiberglass, carbon fiber, foam, epoxy, CA, filler, microballoons,
    paint, urethane, mylar) but I still don't have a composite wing.
    
    I have learned a lot and cut some decent cores, but no wings ready
    to go yet!
    
    I am beginning to see how difficult it is to produce a quality 
    ARF sailplane.
    
    
                                                           Regards,
    
                                                           Jim

The real benefit to scratch building is that you can go back and remake 
any piece a second time. You can always replace with as good as original. 
I've started to take patterns from my kits I'm building for exactly that 
reason. I want to be able to replace a crumpled bulkhead with a new one 
without having to first reconstruct it from the splinters left behind. 
I can alkso replace a piece that has become too heavy through multiple 
repairs.

One nice thing about kits is that there isn't too much guessing about 
fit and assembly order. Most quality kits have this worked out for you.

Yep, the start up costs of getting into composite scratch building are
high. The good part about it is that you can get it a bit at a time and 
spread the cost out. Rather hard to do if you're looking at a $300-400 
kit.

I think once you get "bootstrapped", the cost and time will decrease.

Now where'd I put that motivation? 8^)

    Since Mr. Miner decided to make an appearance in the file maybe he
    can expound on some experimenting he did a year or so ago with plain
    old glass cloth over foam. He did some mockups completely hollowed out,
    some with foam ribs left in and I believe some other variations. Some
    of the results looked pretty usable to me.

    Does anyone know how much 5mm(.020") obechi weighs per sq. ft.
    or cubic ft.  I want to compare it to balsa.
    
                                                      Thanks,
    
                                                      Jim

Probably easiest to just call Dave at (509) 548-5201 and ask the 
source. Most people seem to be getting it from him

    In my endeavors to build light strong structures(wings,empennage),
    I have decided that I will use balsa or obechi sheeting instead of the
    "wet layup", using composites, at least for the time being.
    
    When I go to the Mid-Columbia Slope race this year I hope to get
    some answers about doing all composite wings.  Tips and leading 
    edges remain the biggest questions.
    
    A 550 sq in composite Waco wing with 2 servos weighs approx. 13 oz.
    The 535 sq in Robbe Calibra wing(obechi over white foam) weighs about
    24 oz.  I am hoping to build a wing that splits the difference
    (approx 18 oz) between the two.
    
     The materials for a 75", 550 sq in wing are as follows:
    
    1) 1/16" 8 lb./cu ft. balsa sheeting - 5.2 oz.
    2) Blue foam core---------------------3.1 oz.
    3) Balsa leading edge----------------- .5 oz.
    4) Epoxy to bond skins to core---------?????
    5) Spar--------------------------------?????
    6) Finish covering---------------------?????
    7) Servos, wiring, servo covers--------1.5 oz
    
    The question is - can a sufficient spar, epoxy, and finish come in
    at about 8 oz.?
    
    I'll be curious to see.
    
                                                           Regards,
    
                                                           Jim
    

    With my wife's help I cut a new set of blue foam SD8020 stabs, last
    night.
    
    The templates were cut to allow 1/16" balsa sheeting.  The cores
    are mighty thin.  
    
    We'll see how the final product comes out this weekend.
    
    
                                                     Regards,
    
                                                    
                                                     Jim

    RE -1
    Jim,
    	I've made up several recently.. (foam and 0.062 balsa) 
    Strange though I've always seen them as quite chunky compared to older 
    style tail-planes.
    
    Trevor.

Yep, they can be mighty thin. I've made some 4" chord stabs with 7% 
thickness -> .28" minus .125" for two layers of 1/16" balsa... I'd 
call that "mighty thin" 8^)

most of the stabs I've seen recently are sheeted with 1/32". 1/64" 
ply might work well also and it doesn't have the grain filling 
problems.


I'm about to cut a couple myself. Tolerances are pretty tight in 
those thicknesses.

Did you use the single template with a fixed end on the wire or did 
you do it with a bow and two templates? I found that the two template 
method caused me fits on the cutter so I'm about to try the one 
template method this weekend.

    re: -1
    
    I am cutting the cores using 2 female templates. The taper from
    root to tip is 4" - 3".  I will glue on a balsa leading edge
    and tips.
    
    The use of 1/16" balsa for skinning the blue foam cores, reduces
    the core thickness substantially.  The finished stab however,
    profiles the SD8020.
    
    I would prefer to use the standard 5mm obechi sheeting, but do not
    have any on hand.  
    
    1/64" 3 ply birch appears to weigh at least twice as much as the
    1/16" inch balsa.  I think it would work well, however.  I will
    make up a stab using this and compare the finished weights.
    
    
                                                       Regards,
    
                                                       Jim 

    Re:-.167
    
    Trevor,
    
          I think most flat plate stabs constructed from a solid piece of
    balsa sanded to shape are thinner than a stab constructed to a
    symmetrical profile(SD8020, NACA0009, etc).
    
    Supposedly at high speeds the profiled stab results in less drag
    than the flat plate stab, despite the fact that it is often
    thicker.  This is what the experts tell us anyway.
    
    
                                                       Regards,
    
                                                       Jim
    
    

One other thing that I've done is I've thinned the section I'm using 
so the profile height is the same as that of the stab it's replacing. 
This has caused me to go with a 65% thick SD8020 stab for the Alcyone.
Time will tell on how it performs.

I finally got around to cutting a set of stabs with a single template and a 
pivoting wire. It worked great. Getting the templates smooth is important but 
having to just do one template made it real fast. The other benefit is that 
you don't have to sweat the alignment of the two templates. You always get a 
perfectly flat stab.


I used a piece of board and screwed the templates to the end. I then drew 
lines along the front and back edges of the blank down the board until they
crossed. I then put a drywall screw into the board at this point and that was 
the fixed end of my wire. I used a 1" dowel at the other end as a handle and 
some alligator clips to attach power. Zip, zip, zip and I was done. Far simpler 
than setting up the cutter and I only had to cut a single template. I'm going 
to try this on a set of tip panels for the standard class cores also.

    re: -1
    
    Jim,
    
       Was the stab you cut constant chord or tapered?  I am not familiar
    with the method you have described.  I am confused about how to cut
    a core using a single template.
    
    
    My SD8020 core sheeted with 1/16" balsa came out ok except that the
    profile is distorted towards the trailing edge due to the balsa being
    too thick in relation to the core.  My conclusion is 1/16" balsa is
    too thick to accurately sheet small stabs.  I will make one up this
    week using 1/64" ply.
    
    
    I mentioned last year that I had broken the original Arcus wing.
    I ripped it apart to investigate the spar structure.  This was the
    old style Arcus "SIROS" wing which uses a soft urethane type foam
    sheeted with balsa(the new wing uses bead foam and obechi sheeting).
    The spar was a 3/8" x 3/8" piece of balsa capped top and bottom
    with wood(probably pine or spruce).  The spar ran nearly the full
    length of the wing.  This is why the Robbe wings are so strong,
    I believe Graupner use a similar spar structure in their wings.
    
    I think by using a composite spar structure, the weight of similar
    sized and sheeted wings could be reduced.  This is what I hope to
    do when I build the wings for my unlimited F3E ship.  I am seeking
    a compromise in weight between my Weston wing and the Robbe wings.
    
    The Freudenthaler Surprise III wing with servos and wiring weighs
    12 oz.(as reported in the new RCSD).  Weston's WACO 10-550 wing
    (which has more surface area) weighs about 13 oz. with servos and
    wiring.  I am shooting for 18 oz. with a blue foam wing using a
    composite spar, sheeted with basla or obechi and covered with .6
    oz glass and CA.  While 6 oz. is a tremendous weight increase for
    a competiton electric glider, the complexity of a nicely finished
    bagged or molded wing will take time for me to sort out.
    
    
                                                 Regards,
    
                                                 Jim

This is discussed somewhere in here. I saw it on the Channel One video back 
when I built my cutter. The stab MUST be tapered for this method to be used. 
The leading and trailing edge lines must converge somewhere within a reasonable 
distance. You draw a line along the trailing edge and along the leading edge 
until they cross out beyond the tip. You use a root template and attact the 
tip end of the wire to something at the line crossing. When the wire is pulled 
tight and drawn along the root template, the core is automatically tapered the 
proper amount due to the pivoting wire.

It's far more difficult to explain that to actually do 8^)

If you were cutting with a circular template, this method would generate a cone.
Since your core doesn't actually end in a single point, you only load a blank 
long enough to do the core. In the circular case you would generate a cone with 
the point/top missing.

    I have cut wings this way. The only thing to be carefull of is keeping
    the swing ling taught. A Gremlin wing will need a swing line about eight
    to ten feet long???.
    
    Regards,
    
    Eric.

    Jim,
    
    please keep in mind that a composite spar - at least with carbon fibre
    - does not necessarily increase the wing strength. Carbon is a lot
    stiffer than wood or fibreglass. This means that if you put just a
    couple of carbon fibres onto the spar, they will be so stiff that they
    pick up all the load and the wood will carry virtually nothing. And
    because carbon usually fails suddenly, you might end up with a breaking
    carbon fibre, and the wing is not able to carry the sudden load and
    will break with less load than it would have without the carbon fibre.
    
    Please understand that this is just what I read, I haven't experienced
    that myself, but it does make sense. Therefore, if you consier using a
    composite spar, dimension it such that it will carry all the load and
    build the rest of the wing as light as possible (keep torsional
    stiffness in mind, though). This means (for example) to use balsa
    sheeting instead of obechi.
    
    Just my 2 cents.
    
    Best regards,
                     Hartmut

    re: -1
    
    Hartmut,
    
           I always value your .02 cents!  Tell me more about torsional
    differences between balsa and obechi.  I have not read or heard
    anything which compares the two materials.
    
    I had read an article by Bob Dodgson(Windsong fame) of the dangers
    of indescriminately laminating carbon fiber to wooden spar structures.
    He sighted exactly what you have said.  Apparently people were 
    gluing carbon fiber caps onto the Windsong spar which caused it to
    fail because the two materials flex at such different rates.
    
    It is my feeling that the less a wing flexes, the greater energy
    retention the plane will have.  Do you feel this is true?  
    
    The spar structure I was considering for a two meter RG15 wing would
    be made of two layers of carbon fiber cloth laid up at 45 degrees(web)
    with the caps being 12k carbon fiber tow laid into channels on the
    top and bottom of the wing, contacting both the web and the outer
    balsa sheeting.
    
    What do you think?
    
                                          
                                                         Regards,
    
                                                         Jim
    
                                            

    Jim,

    > Tell me more about torsional
    > differences between balsa and obechi.  I have not read or heard
    > anything which compares the two materials.
    
    well, as I said before, I have never designed or built my own foam wing,
    nor do I intend to do so in the foreseeable future, therefore all I know 
    is from what I read or learned in classes... I'll give it my best shot, 
    anyway.

    There is no other issue regarding torsional strength of obechi versus 
    balsa than the general strength to weight relation. And if you calculate
    torsional stiffness of any structure, you have basically 3 parameters
    that influence it: height (depth), material thickness and material 
    strength. Now the problem is that you want to use a thin airfoil, so the
    possibility of increasing the first is limited.

    My point was only that just for bending, you wouldn't need to go with the
    (heavier) obechi as sheeting if you use a composite spar. On the other
    hand I know that the spar alone doesn't help much for torsional stiffness,
    and at least on my Kormoran I have a torsional flutter problem with the
    balso sheeted wing.

>    It is my feeling that the less a wing flexes, the greater energy
>    retention the plane will have.  Do you feel this is true?  
 
    Yes, definately. If you only ask for my feeling... Well, a simple 
    reasoning is that any flexing will eat up energy that the plane doesn't
    have for other purposes any more. The question is at what point you 
    will not be able to measure any more performance improvement with a
    a stiffer plane. I also assume that other points as sealed hinge gaps,
    hidden linkages etc. will get you a lot more payback than the ultimately
    stiff wing.

>    The spar structure I was considering for a two meter RG15 wing would
>    be made of two layers of carbon fiber cloth laid up at 45 degrees(web)
>    with the caps being 12k carbon fiber tow laid into channels on the
>    top and bottom of the wing, contacting both the web and the outer
>    balsa sheeting.
    
>    What do you think?

    Sorry, no idea here since I don't have any experience on this. I would
    guess there is some literature around on this. What about your great 
    F3B team or Weston? Don't you think there are publications about composite
    plane design?


    Best regards,
                    Hartmut

    RE: -1
    
    I have not seen any articles dealing with spar construction for an
    F3E airplane.  The pro's of course use rohacell and carbon in an
    all moulded skin.
    
    The larger span and higher aspect ratio F3B wings are much heavier than
    the 2 meter wing I am considering.  I think the spar structure would
    be overkill for a plane not subjected to the winch load of an F3B
    launch.
    
    Mr. Weston's 2 meter wing does not really have a spar, but rather a
    spruce "cap" which is let into a channel on the top wing surface only.
    The wing is then covered with a layer 1.7 oz. kevlar and .6 oz
    fiberglass.  The plane is designed to fly with an all-up weight of
    approx. 45 oz.
    
    Maybe the only way to know about construction methods is through
    empirical testing.  You know as Ed Siegmann said - "you test them by
    trying to rip the wings off."
    
    With an electric, the batteries, motor, etc weight is pretty much fixed.
    The wing offers about the only opportunity for weight reduction, since
    the fuselage I am using only weighs about 100 grams.
    
    
                                                 Regards,
    
                                                 Jim
    
    

    Has anyone made templates for the RG15 airfoil?  It looks like
    using a 2 piece template will be difficult with this airfoil
    because of the slight "hook" at the bottom side trailing edge.
    
    I am afraid this will come out flat instead of undercambered.
    
    Any suggestions?
    
    
                                                  Thanks,
    
                                                  Jim

bagging/sheeting will be where the problem shows up. The sheeting will 
probably straighten the foam "hook"

Mark Allen does RG15 wings for his customers. He's usually willing to 
talk on the phone (from what I've heard)

    I finally have a usable stab!  I used 1/32" balsa to sheet blue
    foam SD8020 cores.  This combination works well.  The 1/32" balsa
    is thin enough to work well on small, thin chords.
    
    I also slapped together some RG15 templates out of plywood
    and cut my first RG15 wing core.  It came out nearly perfect.
    Cutting wing panels is much easier than stabs.  The RG15
    templates are tricky to make, however.
    
                                                   Regards,
    
                                                   Jim

    I have finished the ARCUS wing using water based polyurethane(Minwax)
    tinted with analine dye.  I am satisfied with the results and can
    offer the following suggestions:
    
    1) Obechi is tough to fill.  Use white spackle(red devil, model magic)
       mixed with the analine dye and a little water.  Fill the grain by
       squeeging at a 45 degree angle(this is important!).
    
    2) Sand wing smooth using 220-400-600 grit paper.
    
    3) In a separate jar mix some of the polyurethane with water and some
       of the analine dye powder.  Pour through a paint strainer into a
       container.
    
    4) Add straight polyurethane to the diluted, dyed  mixture.
    
    5) Apply several thin coats to wing, light sanding with 600 grit
       between coats.
    
    Done- no more loose film covering to mess around with.  I think it is
    also lighter than film.
    
                                                      Regards,
    
                                                      Jim

Glad to hear this method worked out. Do you think it would work over balsa 
sheeting? Is this analine dye something other than the Rit brand dye used 
for tinting canopies? Where's you get it? Time to try this out on a set of 
HLG wings (cheap, disposable without too much cost)

If you're loking for that ultimate gloss, rub it with some 0000 steel wool.

Jim B.,

Thanks for posting your results with the polyurethane. I'll be using this method
on my Falcon wings. I have one question though regarding the squeeging, is the
45 degree angle the relation of the scraper to the wood, or in the application 
of the filler in relationship to the grain of the obechi. I'll be using two 
colors(red bottom, white top) for the Falcon wings. 

-Lamar

    RE: LAST TWO REPLIES
    
    I don't know if analine dye is different than RIT brand dye.  It
    is available from woodworking shops and mail order from Woodcraft.
    Make sure you get the water soluble version, if you go for it.
    I paid $5.00 for mine, it goes a long way.
    
    I think it would work well over balsa, you might want to use sanding
    sealer first however.
    
    The finish is translucent(ie you can see the grain through it).  I
    think the dye makes the wings more visible, particlularly if there
    are several clear finished ships in the air.  It's not real pretty,
    but it is visible, light and maintenance free!
    
    Lamar, the spackling is squeeged on at 45 degrees to the grain of the
    wood.
    
    Finishing the wing in two different colors will be kind of difficult.
    I brushed the polyurethane on with a disposable foam brush.  It is a
    little difficult to control around the leading and trailing edges.
    If you are looking for a real slick ship, I would go with iron on
    film.  
    
    The latest issue of MAN has Mike Lachowski's comments on this method.
    He basically uses the same methods I have stated.
    
    
                                                     Regards,
    
                                                     Jim

    Does anyone know if the one piece bolt on wings of 100" - 120"
    are bagged in one piece?  In other words can you pull sufficient 
    vacuum on a bag that is 10 ft long?
    
                                                       Thanks,
    
                                                       Jim

You should be able to pull enough vacuum but I'd go with a tap near the 
middle of the bag in a case like this. That way you're only drawing through 
1/2 the lingth of "air wick" to get to the tips. Remember that you also 
need to transport the wing 8^)

    As I am getting into the details of the RG15 wing I am making for
    the TRABI fuselage, a few problems have come to mind.  The wing will
    be a 2 meter bolt-on design.  I am debating over a flat center section
    (32") with 21" tip panels having 3 degrees of dihedral.  The other
    choice is a V-dihedral wing.
    
    I have considered the merits and difficulties of vacuum bagging.
    "Bagging" a one piece 2-meter wing with dihedral sounds kind of
    tough.  Frank Weston claims you can "bag" a wing which has 5 degrees
    or less of dihedral.  Indeed his Waco 550-10 is bagged in one piece.
    This just seems difficult.
    
    I guess I will be sheeting with balsa and joining the panels with
    a fiberglass bandage.  Spackle will then be used to fair the bandage
    into the balsa sheeting.  The whole wing will then be covered with
    .6 oz glass and painted.
    
    At this point the spar assembly is going to be constructed totally
    of carbon fiber.  I would like to do the flat center section, but
    the thought of two bandages instead of one in the center bothers
    me.
    
    What is the longest core anyone has cut?  How much amperage did
    it take?  My current setup can only deliver about 2.5 amps.
    I have easily cut a 21" tip, but my bow will only do up to 32".
    
    
                                                     Regards,
    
    
                                                     Jim

hi jim,

reading your note, i remember a friend who is also
using a RG15 on his models. he told me once, that he
NEVER cuts pieces more than 0.5m wide. he claims that
his method will increase the quality of the core,
because he is eliminating almost all errors due to
wire sagging.
in his words, this is worth the effort of glueing the
pieces together.


joe t.
the_weird_who_is_considering_building_a_fully_automatic_ 
computer_controlled_cutter

Jim,

I've cut a couple of 36" long blanks, but my bow will handle a 48" length blank.
I use a transformer I picked up from Radio Shack(25.2V CT 2.0A) as my power 
supply and have had good luck with it. I'll be cutting some spare 7037 cores for
the Falcon I'm building(maybe this weekend.) The cores are around 40+" long for
the mamin panels. I'll let you know how it goes, if I get a chance to get them
cut this weekend.

-Lamar

    Re: -1
    
    Joe,
    
       I am a confused over what you said about not cutting a core
    more than .5mm thick.  Could you further explain this?
    
    
    
                                                      Thanks,
    
                                                      Jim

    re: - 56.191
    
    Lamar,
    
         Are you using nichrome or stainless sreel wire?
    
                                       
                                                Thanks,
    
                                                Jim

    RE: -.2
    
    Jim,
    
    Joe did refer to a core not more than .5 m (Meter) WIDE (which is 500 mm or
    roughly 20 inches), he did not say anything about THICKNESS or .5 mm.
    
    Best regards,
                   Hartmut

    Thanks, Hartmut this makes sense.  I was assuming width meant
    chord.
    
    
                                                       Regards,
    
                                                       Jim

    Jim,
    
    now that we are talking some metric dimensions, you talked about some 5
    mm obechi sheeting recently. I take it you mean .5 mm, right? I don't
    think you'll consider .2" sheeting on F3E type elevators. 
    
    Debating metric units is a favourite of mine on days like these,
    sorry...
    
            Best regards,
                           Hartmut

    Your right Hartmut, my metric conversions are frequently wrong
    by a decimal place or two.  Bear with me, I am slowly getting
    fluent.  Unfortunately, I can't say the same for my impromptu
    attempt to read technical German(Aufwind).  Even my German born
    brother-in-law stumbles with many of the articles.  He often
    must ask his father who is an engineer and has spent much of his
    life in Germany.
    
    On another note I had a very interesting conversation with Dave
    Jones(editor of the British publication Silent Flight) about
    the ARIANE series of planes.  According to him, Franz Weissgerber
    is involved with selling composite materials for a living and has
    put a great deal of his knowledge and effort into the ARIANE
    development.  He went on to say that he is training others in his
    construction and molding methods.  Having never seen an ARIANE
    (except in magazine photographs) I can only say that it looks to
    be constructed to very high standards.  I have personally examined
    the USA F3E effort and can attest that it is in F3E pilot Steve
    Neu's words- "A little crude, but very functional, like a Russian
    fighter plane."  This proves that pilot skill is more important
    than the equipment, because two Americans finished higher in this
    year's F3E world championship than Weissgerber.  Jones said he
    believes the new ARIANE wing molds are CNC machined from a solid
    composite block.  The accuracy is supposed to be tremendous.
    Interesting stuff, I wish we had more access to this information.
    
    
                                             Regards,
    
                                             Jim
    

Jim,

I have been using nichrome wire on my bow, but I plan to replace it with some
"special" foam cutting wire I purchased from CST. The wire is T370 and is 
packaged by TEKOA(the Feather Cut and Shadow folks.) All the package says is
T370 Hot Wire. I assume the wire is stainless steel. Anyway, I got 8 feet of it
for $3 dollars. 

I should be done with the Alcyone tonight and will be moving on to the Falcon
construction this weekend. I want to make up two sets of wings(S3021 from the
kit and S7037 that I will cut) for the Falcon, so I'll be cutting the cores with
the new wire. I'll report back my results(hopefully!) on Monday.

-Lamar 

    Re: .197

    Hi Jim,

>    Your right Hartmut, my metric conversions are frequently wrong
>    by a decimal place or two.  Bear with me, I am slowly getting
>    fluent.  

    Sure, no problem! We'll do our best to help you guys getting fluent
    with international dimensions... :-) :-) ;-)

>    Unfortunately, I can't say the same for my impromptu
>    attempt to read technical German(Aufwind).  Even my German born
>    brother-in-law stumbles with many of the articles.  He often
>    must ask his father who is an engineer and has spent much of his
>    life in Germany.
 
    With some of the AUFWIND articles I recently read, I had to think
    of you. Sometimes, the expressions used are not really 'standard
    German'. You probably have the same on your side. There is a special
    language developing in any very special area. And Aufwind covers
    very special areas of a special hobby. There are expressions that
    I don't understand, but feel free to ask, anyway.

>    On another note I had a very interesting conversation with Dave
>    Jones(editor of the British publication Silent Flight) about
>    the ARIANE series of planes.  According to him, Franz Weissgerber
>    is involved with selling composite materials for a living and has
>    put a great deal of his knowledge and effort into the ARIANE
>    development.  He went on to say that he is training others in his
>    construction and molding methods.  Having never seen an ARIANE
>    (except in magazine photographs) I can only say that it looks to
>    be constructed to very high standards.  I have personally examined
>    the USA F3E effort and can attest that it is in F3E pilot Steve
>    Neu's words- "A little crude, but very functional, like a Russian
>    fighter plane."  This proves that pilot skill is more important
>    than the equipment, because two Americans finished higher in this
>    year's F3E world championship than Weissgerber.  Jones said he
>    believes the new ARIANE wing molds are CNC machined from a solid
>    composite block.  The accuracy is supposed to be tremendous.
>    Interesting stuff, I wish we had more access to this information.
 
    Yes, regarding Weissgerber's profession, you are nearly right. As
    far as I know, he is a teacher for apprentices. He doesn't have
    anything to do with selling composite stuff, solar cells or anything
    like that. That business is owned by his wife ;-) His business gives
    him access to the CNC machinery for the molds and stuff.

    From what I gather, it seems he is not at the top edge right now. 
    I'm not sure whether his business keeps him too busy, but there
    are always others slightly better (Freudenthaler, US-team). Also,
    a team tried to break his speed record last year. Unfortunately,
    they didn't manage to because they flew over 300 km/h (186 mph), and
    over 300 km/h FAI requires the use of an automatic system, no more
    hand stopwatches.

    So, although it's not an approved record, technology is there to
    exceed Weissgerber's record and it doesn't seem he is attempting to.

    Maybe he is just putting too much effort into technology and too
    little into practice? This is all my speculation.

    The info you'd like to have (techniques and such) is not widely
    published here, either. I talked to Joerg Hermann (Joe T.) recently, 
    and he had visited MCM in Munich, the club of Ralph Decker. Joe was
    impressed by the youth groups building full composite ships as
    naturally as HTAs build Gremlins. You need to be in the circles, 
    contests and all to get that information. There are some seminars 
    out here, but I assume there is also still a lot of trial and error
    involved, and you need to be trying the tricks to ask the real questions.
    For me, it would take over more of my life than I'm willing to invest 
    in this hobby.

    Maybe you'll be moving to California some day...:-)

    Best regards,
                  Hartmut

    Thanks for the info. Hartmut.  186 MPH with an electric is certainly
    impressive!  Do you know any details of the model(airfoil, span, motor,
    # cells, etc)?
    
    I have found cutting foam wings to be fairly easy and inexpensive.
    My set-up is composed of a bow made from 3/4" dowels and a 7-cell
    battery charger. I use blue foam insulation from the hardware store
    for the cores.  If I had been able to work with an experienced person,
    the learning curve would have been dramatically shortened.  The most
    difficult part of the process is getting my wife to help me cut the
    cores!
    
    I have opted to "press" my wing skins on the cores mechanically with
    a simple press constructed of 3/4" ply and stiffened with 2" maple.
    I use 8" carriage bolts to apply even pressure to the core being
    pressed, with wooden spacer blocks spread about the core to prevent
    crushing.  Again this stuff is all available at the hardware store.
    The complex vacuum bagging equipment and associated experimentation
    has kept me out of this method, at least for now.  I would like to
    explore it with at least one other interested person to help with
    the costs.  I do not have the time or ambition to build my own
    vacuum switches and holding tanks.  The commercially available units
    cost about $200.
    
    The modern HQ, Selig, RG, etc. airfoils are difficult to construct
    accurately using built-up construction, which is why I am using foam.
    The use of a two man(woman-my wife) cutting bow and mechanical press
    has provided a low cost, "medium tech" method of producing the strong,
    accurate wings prevalent with the modern designs.  I am fortunate to
    have a basement which can accomodate all this junk!
    
    It will be very hard to improve upon the quality/price/accuracy of
    the sport electric offerings from Robbe(Arcus,Calibra).  They are
    a bit heavy, however, which is where I hope to improve.  I enjoy
    the challenge of producing/designing light, strong, accurate models.
    The arrival of child(planned in near future) will probably derail
    this effort substantially.  This will most likely be my last season
    of "obsessive" model thinking, building, spending.  The change in my
    life/time/income will certainly result in some reprioritizing.  It
    has been fun being able to pursue this interesting hobby.
    
                                                     
                                                         Regards,
    
                                                         Jim

    Jim,
    
    no, I have no more data around that 186 mph electric. It was reported
    as part of a longer report on a record weekend some time last year. I
    guess they didn't want to disclose details on the model before they
    succeed in breaking the record and getting FAI approval.
    
    Maybe your obsession for the RC hobby will go down with the
    reprioritizing, but from my point of view, there _ARE_ more important
    things in life! (Hey! Will you guys put the stones down!?!) Don't
    become depressed. Now that we have 2 kids, there's 75% of the family
    interested in planes where it used to be only 50% when we were a
    couple. Yes, you will probably have to reduce the amount of time and
    money you are spending for RC, but it can remain an active and very
    rewarding hobby. 
    
    Looking forward to reading the announcement of your copilot (or is that
    flight engineer?),
    
    Hartmut

I've been out since tuesday with the flu. This is the worst flu I've had in
years. (read: I wasn't able to feel good enough to get into the shop at all)

Core length:

Wire sag is a function of tension and length the longer the wire the more the 
center will sag behind. This affects the core quality. If you overtension the 
solid wires (nichrome and stainless steel) they stretch and deform and finally 
break. I'm using braided steel C/L flying wire and can tension it up 
significantly more.

I have successfully cut 38" cores with this method but I generally opt for 
multiple panels glued together. I'm using the Radio Shack (home built) supply
similar to Lamar's. I have two. One with a dimmer and one without. The dimmer 
drops the voltage from 25.2 to about 19 vac.

Bagging with Dihedral:

I would think that setting up all the incidences correctly would be too 
difficult for this to work. How about a hinged "press"?

If you put on fiberglass on the outside to reinforce the dihedral joints, try 
HobbyPoxy Smooth and Easy. This sands real nice.

    On page 52 of the new Model Aviation there is an advertisement for
    a foam core cutting business called "The Corehouse".  They advertise
    "superb precision CNC cutting".  I know CNC is an acronym for computer
    numeric control.  In fact I have seen some CNC machines that milled
    metal parts.
    
   Any ideas how a CNC controlled machine cuts foam core wings?  As I
     have mentioned in the past Robbe advertises "machine cut wings".
    
    
    
                                                         Regards,
    
                                                         Jim
    
    

    Accurately! :-)

Saw one of their catalogs at Ray's in Worcester. They quote prices based 
on foam "area". The prices seemed quite reasonable. I assume that they 
have a templateless method to program the airfoil datapoints into the 
CNC machine which drags the wire through in a controlled manner. Lots 
of equipment for a reasonably simple task.

    Re: -1
    
    I have no interest in getting into CNC methods(not that I could!).
    I am just curious how the heck its done!  The ad mentions "setup
    fee" as low as $15.
    
    If the process is like the CNC operations I have seen, once it's
    set up, you can run of tons of cores with no effort other than
    feeding the foam blanks into the machine.
    
    I am still wondering if they use a hot wire(they must, right?) and
    what the positioning hardware is if templates are not used.
    
    Intruiging stuff, love to see how it's done.
    
                                                  Regards,
    
                                                  Jim

Probably worth writing them a letter asking for more information on the 
process. The way I expect it works is a wire strung between two CNC arms 
and guided through the foam through stepper motors. Setup would be 
pretty simple if you didn't have to do templates each time. You could
program the wire to cut the blank initially and then do the core. This 
is probably how the single pass cores (continuous around the LE) are
done.

I've considered putting a small motor on my cutter to draw the arm down
at a preset speed. This would replace the gravity method now used. I keep 
telling myself to K.I.S.S.

    Jim,
    
       I really use the KISS method for foam cutting, by using a bow.
    I don't even have a hands off cutter!  I am curious what the CNC
    machine we are guessing about would have been used for, before it
    was adapted to cutting foam cores.  I am trying to picture the "CNC
    arms" controlled by stepper motors and what other use they could 
    have originally been used for?
    
    Dave Jones from Modellhaus in England told me that the ARIANE wing molds
    of German F3E team member Franz Weissgerber were CNC machined from a
    solid composite block!  Would love to see that operation!  Certainly
    gives new meaning to the phrase "high tech" construction.
    
    The Czech built Pekris gel-coated fuselage I bought makes Frank
    Weston's stuff look archaic.  Apparently gel-coating kevlar is
    tricky.  This fuselage even has a symetrical shape molded into
    the T-tail mount!  The Pekris logo is molded into the fin!
    Not bad for $50.  I wish I could see these operations.
    
                                                       Regards,
    
                                                       Jim
    
    

    
    I've seen building articles on CNC machines that use 3 stepper motors
    on the three axis' and a fast spinning motor (grinder ? same you use 
    for metal - don't know the name). The computer they use is a ....C64 !
    (These suckers are still around, aren't they ?)
    This technique they used in France and all over the world (I guess) to
    shape custom made surf boards 10 years ago. Boy, you should see these
    machines working !  The what_ever_it's_called thing runs with full
    speed into the foam making a mess all over. Back and forth and back and
    forth .......Just until it's finished you would not believe how super
    the surface will be finally.
    Of course the self built stuff won't run THAT fast. 
    
    A two axis controlled wire dragging machine is imaginable, should work
    the same way except you would need two steppers on each side and a well
    defined tension on the wire.....
    
    
    Bernd
    

    
    Hey Jim, my reply was not referring to your entry, we both edited at 
    the same time.
    
    Bernd

Actually, I think the two arm machine might be a little bit wrong. The 
two arms are probably a bow held by the machine head

Figure a single head moving in three axis and gripped in the chuck is a 
foam cutting bow. The movement is controlled in the normal method and 
the chuck rotates slightly to allow for the taper in the wing core. The 
real beauty of this method is that you don't have to reset the templates 
for left and right wings. Just "mirror" the CNC motions.

    There are foam cutting machines readily available on the market here in
    Germany, and they work as described before: Two axis stepper motors on
    each side guiding a heated wire. You need the computer to drive it and
    can do almost anything: different foils on both sides etc. etc.
    
    The company offers machine cut cores per your specification or the
    machine itself (for clubs probably). Or you can set up a machine
    yourself. I know that Ralph Decker's club in Munich built one (ask Hans
    EICMFG::KARNITSCHNIK for details). Joe T. (FRUST::HERMANN) has seen it,
    too.
    
    Jim, you just need such a machine and will build an F3B/E club around
    it - or is it the other way round???
    
    Best regards,
                  Hartmut

    Hartmut,
    
           I wish I could say it was only the availablity/non-availability
    of equipment that has kept folks here out of F3B/F3E.  In reality
    there is just no interest.  Even if F3B planes and winches were
    provided at no charge, completely built and ready to fly, I do not
    think there would be any takers at my club!  I do not even think
    the glider pilots I know would want to fly them.
    
                                                       Regards,
    
                                                       Jim 
    
    
    

>Figure a single head moving in three axis and gripped in the chuck is a 
>foam cutting bow. The movement is controlled in the normal method and 
>the chuck rotates slightly to allow for the taper in the wing core. The 

    Mostly, CNC milling machines have a 3 axis table, the milling head is
    fixed in position (though some can automatically change tools and
    provide the ability to operate as a drill press.  Z axis movement tends
    to be pretty slow).

    I was reading an old RCSD(May '92) article about a Torrey Pines 
    slope race which had an interesting wing mentioned.
    
    To quote the article:
    
    "Mark came in second winning four of five races flying his incredibly
    fast, scratch built "RIPPER" with wingeron, elevator and rudder
    controls and unique formica skinned wings sporting an SD7003 airfoil."
    
    I had never heard of using formica for wing skinning.  It just goes to
    show that different things can work.  Talk about resistance to
    "hangar rash".
    
                                                        Regards,
    
                                                        Jim

I think somebody forgot the wax paper and glued the ship to the 
building board 8^)

Formica would work well but weight is an issue (but not in a 24.5
oz/sq ft wingloading ship)

Again, it's just a matter of how you use the material. Similar 
things have been done with fiberglass sheets that were cast onto 
plate glass and then put on foam cores. Mark Antry had some notes 
about that in one of the glider threads.

    I took my scales to the local specialty wood shop to weigh the 
    hardwood veneers to see if any were suitable for skinning foam
    wing cores.
    
    This idea was prompted by favorable reviews of the Polish "Grifter"
    sailplane, which was reported to have maple skinned wings.
    
    The birch and maple veneers had very tight grain which would make them
    excellent for wing skins(closed grain is easy to fill).
    
    The weights were as follows:
    
                               Maple - approx. 1.75 oz./sq. ft.
    
                               Birch - approx. 1.33 oz./sq. ft.
    
    Unfortunately, these are a little high, for example a wing area of 900
    inches(6.25 sq. ft.) sheeted with birch veneer would weigh 16.6 oz for
    the veneer only.  
    
    On the other hand, a hardwood veneer lends itself to finishing with 
    clear lacquer which is lighter than heat shrink film covering.  It is
    also stronger than balsa sheeting and closed grain as opposed to the
    open grain of obechi.
    
    A 2' x 8' piece of the veneer is about $32.
    
    I think it may potentially be a good choice for some sailplane designs.
    The resistance to denting is also a good .
    
                                                    Regards,
    
                                                    Jim 

    My father received his obechi from Kennedy composites.  It is 1/42"
    thick.  The weight works out to be .005 oz./sq. in.
    
    Wing sheeting materials:
    
    Obechi(1/42") - .005 oz/sq in
    
    Birch(3 ply-1/64") - .0087 oz/sq in
    
    Balsa( 6 lb-1/16") - .0035 oz/sq in
    
    1/32" 6 lb balsa +  1.7 oz/sq yd kevlar -.0030 oz/sq in
    
    3 oz/sq yd glass + 1.4 oz/sq yd - .0034 oz/sq in
    
    
    *All these materials will need adhesive(epoxy or contact cement) to
    adhere to the cores.  Leading edges and wing tips will need to be 
    added(fabricated).
    
    
                                                        Regards,
    
                                                        Jim

Was your father happy with the quality of the obechi from Kennedy?

(I may be buying some in bulk)

    Jim,
    
       I looked at the obechi real quick yesterday(Mother's Day) and it
    looked fine to me.  It's very thin(1/42") and shipped rolled up in
    a box.  I have heard obechi can be tough to work with.  It's
    reputed to be very brittle(cracks easily) and difficult to sand.
    
    I'll let you know how it works.
    
                                                       Regards,
    
                                                       Jim

Lamar is using it on his Falcon wings and I've had a few people ask for it. 
He wants bulk orders for 24 sheets if you're going to be a supplier so I 
wanted to make sure before I shelled out that much sight unseen.

Thanks,

Jim

    Jim,
    
       At this point, obechi must be considered a "proven" material
    for glider wings.  The number of different manufacturers that use it
    is large.
    
    If one desired a clear lacqured finish, I might try the 1/64" birch
    ply.
    
    
                                                       Regards,
    
                                                       Jim

I agree with Jim B.'s comment about obechi being brittle. It will split on you
in a heart beat, if you aren't careful with it. I haven't found any problems
sanding the obechi(yet!) that came with the Falcon kit. I did find that using
masking tape on the cross grain edges solved all spliting problems. I was able
to square the root and tip of the main panels on the table saw without any 
damage(and had a nice clean edge!) From my little experience with it , I like the
obechi sheeting a lot!
 
I was hoping to use the poly-acrylic on the obechi this weekend, but I didn't 
get the root ribs attached to the panels. Like Jim Reith told me earlier, "my
priorities are all screwed up!" :-) Time to get moving on the Falcon...

-Lamar

Thanks guys.

Re: .222

I wasn't questioning the material, but the quality of this particular 
supplier

    
    I now (eventually) have the obechi veneered foam cores for my 1/4 scale
    Pirat, it's taken a long time to get them, but I am pleased with the
    quality.
    Now as I am not working from a plan here, the originals on the plan are
    built up wings, I have a few questions, 
    
    1) How much spar strength will I need?
    
    2) Should I cut the wing in two root to tip, insert spars and fit back
    together, or should I leave the wing intact and cut out grooves top and
    bottom for spars then slot down behind that for sheer-webbing?
    I am reluctant to cut the wing root to tip but that is what the
    supplier (RAM-AIR) recommended (then fit a ply/carbon/ply lamination
    back in)
    
    3) The wing is approx 12 feet (just over 3.5 metres) with a 6 foot
    centre panel and 3 foot plug-in tips, with ailerons on the tip panels,
    will I need spars in the tip panels? how about a foot of 1mm ply cut
    into the panel or just a top spar part way do I need anything and if I
    do would that suffice?

My suggestion would be to follow the supplier's recommendations. 
If you're going to have to slot it to put the spars in, I'd 
suggest using the type they suggest. Unless you're going with 
vertical grain shear webbing between the sparsputting tyhem top 
and bottom with nothing between them will be useless. Cutting in 
to allow the shear webs to back the spar isn't going to go easily. 
It makes the most sense to rip the wing and get a straight edge 
and then sandwich in the spar they suggest and glue it up with 
sufficient glue. If you're unsure, follow their suggestions. It 
sounds as through it will do the job you need. Remember, the wing 
has to be strong enough to support the weight/force of the plane 
while manuevering

    I didn't pay attention what type of model the Pirat is. If it's a
    sailplane (thin airfoil), you need a spar. If it's a motor plane (thick
    airfoil) you don't. 
    
    
    Bernd
    

    
    Thanks for the advice, yes a Pirat is a late 60's sailplane it (in 1/4
    scale form) has about 12 feet of wing with a root chord of almost 11
    inches, it's a flat bottom section and is about 1.5 inches thick, it
    has 3 feet tip panels with 4 degree's of dihedral and the tips taper
    from 11 inches to about 7 inches.
    
    Richard

    I am in the process of getting a quote for laser cut templates for
    use in hot wiring foam.
    
    The contractor can cut in metal or wood.  I would think metal is 
    the way to go.  Can anybody think of any reason not to use metal?
    
    Also, if the price is right is anybody interested in getting any
    templates.  I am led to believe that once the program is loaded
    many templates can be quickly made.
    
    I have found that fabricating ACCURATE(and I stress accurate) templates
    is a very time consuming process, especially for a triple taper wing!
    
    
                                                    Regards,
    
                                                    Jim

I'd be interested in what the quote is for the templates. I have found 
that I can produce a "good enough" set of templates using a piece of 3/32" 
ply with a postscript airfoil glued on, cut out on a Dremel motoshop saw 
and then block sanded to the line by hand. I then seal the surface with 
thin CA and resand. I can do a set of templates in about 15 minutes this 
way and get a very nice finished surface. The only thing I'd worry about 
with the metal templates would be that the metal acts as a heatsink and 
cools the outer edge of the wire.

I think I'll probably try some of that Teflon tape from Soaring Stuff on 
some 1/4" ply templates in the future. How much time and effort you put 
into the "ultimate" template needs to be offset in the number of uses it 
will see and the amount of available time. Personally, I don't think I 
could wait for the turnaround on a set of templates cut by someone else.

    Re: -1
    
    Jim,
    
       Are you using one or two piece templates?
    
                                      
    
                                               Regards,
    
                                               Jim
    
     

Two piece, both supporting the wire from the top. I cut the bottom 
template first, let the core settle into the bed and then cut the top 
template.

I'd like to try the template method Leroy Satterly discussed in one of 
his columns a while back with the pivot in the back but I haven't been 
able to get it to give me good consistant alignment yet. I feel that the 
alignment of the templates for the cut is where I spend the most time
and energy.

    I have cut many stab cores over the last two weeks, hoping to
    perfect my technique before moving to the wing cores for my new
    ship.
    
    I have gotten quite good at using the bow by myself, having grown
    tired of cajoling my wife into helping.  I push the wire through
    the foam rather than pull because I can "see" better this way.
    I think entering trailing edge first works best, particularly
    since I cut off the leading edge of the foam to accomodate a
    spruce leading edge.
    
    As usual I am learning things the hard way.  If I need a stab
    with a 4" root, I am finding I cannot use a 4" template because
    the thin trailing edge will come up short due to the thickness
    of the cutting wire.  I am experimenting using a larger template, for
    instance, if a need a 4" root, I will use a 4.25" template.
    
    The modern Selig, Quabeck, and Girsberger foils with their long, thin,
    slightly undercambered trailing edges are proving difficult to
    reproduce accurately.  If relatively thick sheeting material(say 1/16"
    balsa) is used, a large portion of the trailing edge is distorted.
    1/64" ply is nice but heavy.  Vacuum bagging cloth produces nice
    trailing edges but the leading edges require a lot of work.
    
    Mr. Selig claims that small deviations can make significant
    differences.  The difficult chore for the builder/manufacturer
    is to reproduce these airfoils accurately.
    
                                                    Regards,
    
                                                    Jim

    I cut the wing cores for my Trabi fuse this weekend out of pink
    foam.
    
    The foam blanks layed perfectly flat befor they were cut.  After
    the cores were cut both sides of the bed and even the cores are 
    warped.  The beds immediately developed significant warp.
    
    Anybody know what causes this?  I was under the impression that
    foam did not have a "grain" as such and could be cut in any
    direction.
    
    The 74" RG15 core thinned to accomodate 1/32" sheeting weighed 3 oz.
    The root is 8.3" and the tip is 6".
    
    On another front, I saw an article in an old MAN or RCM about
    removing foam from a core to reduce weight.  THis was done in
    a criss-cross pattern.  The wing was from a pattern ship and the
    article claimed a pound of foam was removed(must have been a big
    wing!).  I am really surprised the glider fanatics have not jumped
    on this.  I am thnking either the foil shape is compromised are
    the torsional stiffness is lessened.  Anybody else see the article
    of have any opinions on doing this?
    
    
                                                          Regards,
    
                                                          Jim

The extruded foams can be stressed due to too much pressure being used in the 
process. I've found this to be the case with blue foam but the gray has been 
much better. Try to pick foam that doesn't have a shiney skin to it and you'll 
avoid it. Back in this note a ways (56.99) you will find a note on this where 
I refer to them as "banana cores". Seems to be a frequent problem 8^(

    RE: -1
    
    Jim,
    
       Thanks for the reply.  I have been unable to find any local
    sources for the gray foam.  Nobody even knows what I am talking
    about.  The stabs do not show this characteristic, so it seems
    ok for short lengths.
    
                                                            Thanks,
    
                                                            Jim

I'm having trouble finding the gray foam as well. The foam place I deal with 
wants me to take an entire log if I order it through them(96 2'x8' sheets 8^).
They did call Dow for me and found out that it's carried by lumber yards that 
deal with Georgia Pacific (they won't sell direct to an end user). I've found 
one place locally but they stock 4' wide which won't fit in my car.

    
    Jim,
    
    I've seen an article about "honeycombing" foam wings to save weight
    too, this guy said that the major weight saving is in the adhesive he
    was using to attach sheeting to the wing, since he had a much smaller
    area to cover.
    
    Nigel.
    

        Re:   <<< Note 56.238 by BAHTAT::EATON_N "Nigel Eaton - Effing the Ineffible" >>>

        Nigel,
        
                Terry Luchenbach  (maker  of the Probe glider) has a hand
        launch plane where  the  blue  foam cores are honeycombed and the
        wing is sheeted with a kevlar sheet that was saturated with epoxy
        on a glass plate to  create  a composite sheet.  It is incredibly
        pretty.    I  have  purchased a  glass  plate  to  try  the  same
        technique.
        
                The theory that it saves adhesive is difficult to believe
        because the adhesive needs to be applied to  the  sheeting before
        pressing or bagging, applying it to the foam is  bad  because the
        foam acts as a sponge.
        
        Anker

    
    Ah-hah!
    
    OK, in the article I was talking about I think the guy was using wood
    (obechi?) to sheet the wing. This relies on my notoriously dodgy memory
    for accuracy! He was definitely applying adhesive to the foam, how he
    got round the "sponge" problem I have no idea (twice as much glue? 8^)
    
    So, irrelevant contribution from ol' "low tech" Eaton again folks!
    
    Cheers
    
    Nigel.
    

I've read a couple of articles about using fiberglass/kevlar sheets layed up 
on a piece of glass. They seem to work well and you use the glass side as the 
final surface so you get a smooth finish. Application is the same as with wood 
sheeting. You could probably paint the glass and do the paint transfer trick 
like with the mylar bagging method.

>He was definitely applying adhesive to the foam, how he
>got round the "sponge" problem I have no idea (twice as much glue? 8^)

He might have been using spray adhesive (yuck IMHO) or he might have applied it 
with a sponge! I have read about one person using foam safe thick CA to do this.
It was slow enough to allow you to apply the glue and then the sheeting but like 
the contact cement method, you better get it right the first time. The cost is
high buit you do have a wing ready to cover in as long as it takes to get set up 
and apply the skins. I have heard of people sheeting built up wings byt spraying 
the sheeting with kicker and then using thick CA on the ribs. The CA kicks when 
the two are brought in contact.

The problem I see is the likelyhood of delamination. 1/2 the surface area for 
glue contact. He might have prepared the foam surface in some manner before 
applying the glue. I have read about a few methods for presealing the foam. Most 
common is the application of a "spackle" type filler. 

Your sheeting needs to have more strength to avoid the "lightening holes" to show 
through like the rib bays in a monocoated wing.

    I also am just about to layup 1.8 kevlar/.72oz glass on a glass
    pane.  I will be trying the paint transfer method.  I just received
    20 sheets of 1/32" balsa and the variability in weight/hardness is
    incredible.
    
    This is what is nice about composites, the weight/density is uniform.
    
    To those(Anker,Jim,anybody else) trying this method, please let us
    know how it goes.  I think this method is simpler than vacuum bagging
    with wet layup and may offer us a great new way to build.
    
    The method I read about is as follows:
    
    1) Coat glass pane with release agent(Partall, Freekote, etc)
    
    2) Cut glass, kevlar, etc, slightly larger than the glass pane
    
    3) lay fiberglass/kevlar on the glass pane
    
    4) saturate the fabric with laminating epoxy, squeege of excess
    
    5) bevel the ends of a small 1/2" diameter wooden dowel 
    
    6) place plastic cut from a garbage bag over the saturated glass/kevlar
    
    7) roll the dowel over the plastic bag which forces the excess resin
       off the edge of the glass pane
    
    8) leave the plastic over the entire mess and let cure for 24 hours
    
    9) the side facing the glass pane should be glass smooth, and the side
       you rolled with the dowel will be slightly textured, providing
       better adhesion to the foam cores.
    
    10) cut the finished sheet to your wing planform and press or bag
        to your cores
    
    
    *By substituting carnauba wax for the release agent, and painting with
     Krylon, color transfer may work!
    
    
    Let's here how it goes, I should be able to report next week as I am
    expecting glass and kevlar from Composite Structure Technologies this
    week.
    
    
                                                            Regards,
    
    
                                                            Jim
    

I've recently dealt with Kennedy Composites for some obechi. I got a call last 
night and was told about some new kevlar he's carrying. It's a crow's foot weave 
and is supposed to have some nice capabilities for contoured layup. He's also 
carrying some unidirectional CF which I was very pleased with and some kevlar 
tow which I've used in a couple of places. He's also got a satin weave glass 
which is great for outer surfaces in layup. He's very talkative and helpful on 
the phone and has called me several times recently to let me know about new 
products (and sent some samples).

Probably worth giving him a call and getting his latest price sheet for 
comparisons.

Hi folx,

Regarding reply .242: my local epoxy guru explained me a very similar method.
He does it the way as Jim's explains it, with some changes and enhancements:

Because he was using this method for getting sheeting material for stabs,
the glass pane is only partially covered with glass.
He then vacuum-bags the glass pane. Because there is only one connection
point for the vacuum, there is a possibility that the vacuum will
seal itself off at a point nearby the entry point into the bag,
leaving part of the bag under no-vacuum. Therefore he lies a strip of
mull/gauze bandage lengthwise over the material or besides it, running to
the connection point, giving kind of a channel for the air to escape.

Of course you have to work with the minimum amount of epoxy that is possible.
Normally you have the weight of your epoxy equal to the weight of the glass,
that is 50:50. Industry-made materials reach epoxy/glass relations of 30:70.

Painting is no problem, he uses an airbrush and spray's over the wax, lets
dry some six hours (depending on the lacquer) and the proceeds.
He is using normal 2 component car lacquer. This is important, because
normal, spray-can lacquers could contain solvents that solve the wax.
You surely will not be able to get the epoxy/glass off the glass pane then!
At this point he said: What you are doing with the wax/lacquer/epoxy is pure
chemistry, so some combinations work, others won't. If you have a working
combination (or can benefit by someone else know how), then stick to this
combination! This applies to molds as well!

There is another advantage with this method: The resulting sheet is so
flexible, you can use it as hinge also. Just sheet the stab, carefully
cut out the slot from the underside and presto!

Cheers
Joe T.

    I have a question about laying the fiberglass on the glass pane etc.
    Can the result be formed around the leading edge without cracking etc ?
    
    Regards,
    
    Eric

    re: -1
    
    I suspect you might experience some problems, especially if you use
    stiff materials like carbon or kevlar.
    
    A possible way to deal with this situation is to slice off about 1/8"
    of the leading edge, use the hot wire with the core between the beds.
    
    When you place the fiberglass/kevlar sheets between the beds, they
    should now hang out over the front by 1/8".  Wet out 12K carbon fiber
    tows and stuff them into the gap between the foam and the upper and
    lower skins.
    
    After the epoxy has cured the carbon can be contoured with a sanding 
    block to match the airfoil(wear a mask).
    
    
                                                     Regards,
    
                                                     Jim
    
    
    
    
                        
                        

    Where can I get virgin white expanded bead foam?  The stuff I am
    getting at the lumber yard must be regrind, because it is full of
    hard little lumps when you cut it with a hot wire.  
    
    I know that CST sells it but it is awful expensive plus an
    oversize UPS shipping charge.
    
    Has anyone had any luck finding local sources?
    
                                                           Thanks,
    
                                                           Jim

Look in the yellow pages under insulation. Check in the yellow pages in the 
nearest large city and you'll probably find someone. Give them a call and 
ask about regrind. There's a place in Worcester but they have regrind so I 
have to travel out to Waltham to get the right stuff (and hour drive versus 
1/2 an hour)

HQ carries Georgia Pacific stuff so I hope to get my Dow Gray there in the 
near future.

    Re: -1
    
    Jim,
    
       Thanks for the tip.  I called the local Georgia Pacific warehouse
    and for the first time in my life someone knew what I was talking
    about when I asked about grey foam!
    
    The drawback is they do not sell retail, however they gave me the
    name of a local supplier who would handle the transaction through
    them.  I must buy a minimum of eight 2'x 8' sheets for $8.90 per
    sheet.
    
    Does this seem like a good price?
    
    
                                                        Thanks,
    
                                                        Jim

                I pickup  up  my glass pane and have been playing with it
        every evening.   In  spite  of  not  using  the  dowel method for
        eliminating excess resin it  has  worked  out  well.   As release
        agent I have used butcher's  wax bought at a hardware store.  You
        can buff it so it looks like there's none left, but there must be
        a very thin layer because the sheet  releases  very well.  I have
        used laminating resin.  The sheets come out  beautiful  with  the
        glass pane side absolutely smooth.  I'm going to  get  some  1 oz
        glass and sheet a set of Chuperosa wings with this  method  as  a
        starter.    If that works well I'll go nuts and build  a  set  of
        unlimited wings!
        
        Anker

Re: .249

Yeah, that's a reasonable price. I think I paid $8 a sheet the last time I 
found it. HQ is a retailer that deals with Georgia Pacific here in Mass. 
I'll have to get in there sometime soon.

Chances are the GP guy could point you at a retailer with virgin white as 
well.

    Re: -2
    
    Anker,
    
         Glad to hear of your success with the glass pane method.  Have
    you tried painting the waxed glass with Krylon paint?  I am going to
    experiment this weekend to see how the color transfer works out.
    
    When I was buying the Krylon, I noticed Varathane brand water based
    polyurethane in colors(red, green).  This should be ideal for finishing
    obechi.  I have read that 3 coats only adds 1.25 oz. to a 600 square 
    inch wing.  One can $14 should do a lifetime of wings.  No more film
    sags sounds good to me!
    
                                                      Regards,
    
                                                      Jim

    I tried the paint transfer method this weekend and it worked just
    great.  I sprayed a 6" x 28" glass pane with yellow Krylon paint
    which had been waxed with KIT car wax.  
    
    I used 1.7 oz. kevlar with a layer of .7 oz glass.  When I took it
    to the field everyone thought it was monokote!
    
    There really was only one problem and that was a few spots the paint
    stuck to the glass and did not transfer.  The reason was obviously
    that there was not enough wax on that part of the pane. 
    
    The KIT car wax I think is a little to soft(ie it rubs off too easily
    when you buff it).
    
    What is paste wax?  This is what I think works the best. I think it
    is harder and will not rub off too easily.
    
    The finished painted panel weighs less than an equivalent piece of
    1/32" unfinished balsa!
    
    
                                                     Regards,
    
    
                                                     Jim

I managed a few things this weekend as well.

I've been asked to press some wings so I went to the lumber yard and got some 
3/4" signboard to make my press panels out of. I intend to use two pieces of 
signboard (this has one perfect, paper covered side) with 1x2" as a frame 
between it. I also got some 36" 1/4-20 threaded rod to use as tensioners. 
I'm sizing the press to be 16"x48" with 8 tensioners running down the two 
sides. I hope to have it working this weekend and try some Chup panels (I 
still hope to get a slope Chup in the air this year)

Jim, I'm really pleased to hear of your success. I'm hoping to try the same 
style in this new press. I assume you used the light glass as the outer 
surface with the kevlar as the inside? How big a panel do you think this 
will be able to do (strengthwise)?

For wax you want to try a Carnuba (sp?) wax. This is supposed to be a very 
hard wax and should part pretty well. I think Anker said he was using 
Butcher's wax. I've used that as well but you need a couple of coats. How 
was the cutting of the panel after it cured? I'd like to do larger rectangles 
in advance and then cut to size/shape when I need it (since I expect I'll 
need to do the sheeting one piece at a time and wait for it to cure) Did you 
just use 1/8" glass or did you go for 1/4" (read expensive) plate?

    RE: -1
    
    
    Jim,
    
       I used 1/8" cheap glass, the 6"x28" pane cost me 85 cents.
    
    The KIT car wax advertised pure Carnauba wax, but as I said it 
    was very soft(rubbed off easily) which it touted as a benefit.
    
    What is butcher's wax?
    
    You are right, the kevlar .7 oz. glass received the paint from
    the glass.
    
    The finished panels cut very easily with a #11 razor blade, which is
    somewhat amazing considering how difficult kevlar is to cut before
    it is impregnated with resin.
    
     
                                                   Regards,
    
                                                   Jim

    In the last couple of months I have come to realize what a great
    value quality kits are!
    
    You really don't save too much $ scratchbuilding and the time investment
    is staggering.  
    
    Gluing together sheets of 4" 1/32" balsa last night only reinforced
    my feeling that it seems impossible to have house, family, job,
    and still do scratchbuilding, much less time for flying!  OK so I
    won't use balsa sheeting again too soon, but I had to buy the stuff
    and try it to learn this lesson.
    
    Yeah, laying out $300 for a kit with presheeted wing and glass fuselage
    is tough to do.  Try collecting all the items you need to accomplish
    this yourself - cutting bow, powersupply, the right foam, carbon fiber,
    kevlar, mould release, template material, tools to use forementioned,
    etc.  Add up all the $5 shipping charges and the time finding ordering
    and learning to use this stuff!  Whew- you could have bought a
    beautiful ARF with change back and been flying, instead of wiping
    epoxy goo from your fingers.
    
    Like anything else working in foam and glass has a learning curve, and
    if you master it, you can make some great planes at lower cost than
    the commesurate kits.  But the "IF" can really slow things down and run
    up the cost.
    
    
    Regards,
    
    Jim(who now wishes he just bought a RFM Surprise II and could fly
    tonight!)
    
    

You spend that money to buy "spare time" 8^)

Try taping the 1/32" sheets together with mailing tape without gluing them 
and then bagging/pressing. This will come out just as good with less hassles 
aligning the edges (the pressing does it for you) and enough glue will seep 
in to glue them anyway.

    Re: -1
    
    Jim,
    
       I thought about doing that, except that the thickness of the
    sheets was quite variable.  So I figured it would be easier to
    sand them so a uniform thickness laying flat on the bench.  But
    this probably still could have been accomplished  with the tape.
    I'll remember that next time.
    
    
                                                        Thanks,
    
                                                        Jim

    I went a little crazy and paid $300 extra for my Conquest-6. What I got
    for the extra money was a finished pair of wings and stabs and rudder.
    
    When I say finished I mean that they were pre-sheeted with the lightest
    of balsa. The, hollow, tips were already added. There was CF installed in
    the TE's. The retract plates were embedded and the gear excavation
    completed and balsa lined all ready to accept Supra retracts.
    
    All I had to do was bore the holes for the servos and cut holes for
    the servos before joining the halves. The manufacturer said that he could 
    not guess where I would want to fit the servos so I would have to do
    that myself.
    
    All of the control surfaces were cut out, edged and chamfered ready for 
    hinging.
    
    I took a lot of ribbing over the extra money spent but I saved an
    enormous amount of workshop time and also finished up with a plane that
    is 1/2 lb lighter. I also did not have to find the balsa sheeting or do
    all of cutting out of the control surfaces. This has to be done so
    accurately and always cause me to "Sweat" a little. "IF" work I think
    it was called?.
    
    Sometimes it is worth the extra expense - just as long as you do not
    tell your wife!.
    
    E. 
      

Jim,

You can still sand, just put them tape side down on the bench and sand what 
will become the inside surface. Block sand the inner surface and it doesn't
matter if you leave a few "scratches" since it will just help the glue grip.
I use 2" tape and it holds fine.

yeah, it saves me time to do it this way.

Eric,

Yup, that's the extra time they don't build into the wings. 8^) Didn't know 
we were living in such "heavy" times 8^) Of course it only gets you into the 
air faster if you open the box sooner 8^)

    RE: -2
    
    What I am finding out about the better ARF's is you cannot do as
    good a job even if you wanted to!
    
    Some of these manufacturers have built jigs and such and are able to
    reproduce a consistent, accurate, light product.  They earn their
    money.  Layup your own fuselage just once and then see if a guy
    getting $80 is overpaid!
    
    Eric, it sounds like the Conquest-6 was actually a good value.  That
    amount of prefabrication, especially on the fussy items is great.
    The Freudenthaler Surprise II I am considering costs $400 and does not
    have the control surfaces cut out!  
    
                                           
    Regarding crashing a model, I am not sure which is worse:
    
    1) A model you have 200 hours invested and $80.
    
    2) A model you have 50 hours invested and $300.
    
    
                                                       Regards,
    
                                                       Jim

    
    Jim,
    
    A chap at my club has the theory that if you can fly a plane for more
    hours than it took you to build it, then you win. This theory (if true)
    suggests that the more money / less time route is preferable when
    you're choosing which planes to crash! 8^) Maybe we should take into
    account how many hours you have to work to earn the money to spend on
    the plane?
    
    Cheers    
    
    Nigel

    Good theory...
    
    I used to be very outspoken about ARF's however...................
    
    I love to build but this year it has been especiially hard to get the
    time. ARF's are great for stuff like trainers. When I say ARF I mean
    pre-covered etc. ARTB's, where the B = build, are great because you can
    custom finish them. The jig built fuse is a plus.
    
    I like the aformentioned rule:
    
    		Value = Flying time must be > Building time. 
    
    By my calculations the only plane that did not really make that rule
    was a Gremlin that got X-on whiped out in its first flight. I also need
    to do some more flying with my Conquest-6.
    
    E.
    
                

    
     By that definition, the only plane I've had the DID make it was also
    a Gremlin. 
    
          Building time = 20 hours
    
          Flying time = 250 flights @ 8 minutes (average) = 2000 minutes or
                        33.3 hours
                        
    
       Interesting, at this rate, your average trainer (kit) that takes 40
    hours to build would need to survive about 500 flights! I wonder how 
    many have made it? :) 
    
    
       Note: Having a scale Masters plane meet this criteria would surely
             be a feat!             
    
         

    Eric's Conquest wing did come finished very nicely.  I'd say it was
    worth the $$ but I'd still opt to build my own.  
    
    	I have many planes that have given me more flying hours than I
    spent building but I guarantee that the average plane never comes
    close.  I also have lots of flights to make on my Conquest to get to
    that point.  I currently have about 35 flights at about 8 minutes each
    for 4.7 hours!  It took me that long to prepare and sheet the wings.
    I didn't keep track of time but I must have put 60+ hours into the
    Conquest.  That means I need to get 450 flights on it to break even!
    
    Charlie
    

    Alternate building plan.........
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
  			  AUCTIONS! :-0
    
    
    E.

    If you don't mind my asking, how much do the Conquest-6 kits
    cost in their various stages of completion?
    
    I am curious how they compare witht the glider kits.
    
    I just purchsed a Surprise II electric with a presheeted one piece wing
    and molded stab.  Cost=$400(ouch).
    
    
                                                        Thanks,
    
                                                        Jim

    Not a problem. The C-6 is $225 for the base kit and $525 for the
    pre-finished wings stab and rudder kit. I have also heard that they have
    all gone up by $50.                         
    
    regards,
    
    E.

    Re: -1
    
    Thanks, Eric.  After my experience this weekend pressing balsa/glass
    onto cores I cut and prepared myself, I have changed my thoughts about
    kits.
    
    I think many of the better kits offering prepared wings/fuselages 
    are good value.  The amount of time and $ I have spent collecting
    the hardware necessary to cut cores and press them is incredible.
    Not to mention the learning curve.
    
    There is a price to pay for a finely crafted airplane - time or $.
    With my current building skills and equipment inventory, I could not
    profitably build a plane which sold for $500.  The experience and
    tooling  that goes into producing one of these ships is incredible.
    
       
                                                         Regards,
    
                                                         Jim 

    I agree.  I don't think anyone could make a reasonable living building
    planes because noone could afford to pay what they're worth.  I hate to
    sell any of my old planes because I still remember the hours I invested
    in building them.  I have several that I haven't flown in years but
    they still hang in my workshop.
    
    Charlie
    

With the dramatic taper of most tiplets and stabs today, it's hard to cut them 
on a 48" wide cutter (9" tips tapered from 7" to 4" for example)

One method that is used is to tie the end of the cutting wire to a pivot and
the other end to a "handle" and pull the wire along the template. 

I find that pulling the wire and maintaining even tension is difficult. I've 
got enough going on getting the wire to track smoothly without having to pull 
on it. I have a small hand bow that has a button on the handle to turn it 
on/off and it keeps the wire tensioned. I use this to cut foam sheets into 
blanks. This weekend I came up with a neat way to cut stabs using it. First, 
you set up as you would with the pivot method. This usually means bolting the 
template to the end of a board and drawing lines parallel to the leading and 
trailing edges to where they cross (this would be where you place your pivot)
For a pivot I use a block screwed to the base board with a piece of plywood 
screwed and/or glued to it extending over the "pivot" point. I measured up to 
the centerline of the root stab/tip template and then cut a slot down into the 
plywood over the pivot until the bottom of the slot is the same height off the 
board. Now I lay the wire of my cutting bow into this slot, hold the bow 
horizontal and cut the cores. Worked like a dream and the wire was always 
properly tensioned and I had a lot better control without having to worry 
about the "pivot" end "wandering". I did all the stabs and tiplets I pressed 
this weekend using this method and they all came out great for hand cut foam.

This weekend I did some more cutting and was pleased to remember how 
great gray foam cuts. I got some nice cores done (including Anker's) 
and while doing Anker's tips I found that the pivot block method 
mentioned in the previous note works well with the automatic cutter as 
well. It had too gentle a taper for my hand bow (42") so I put it into 
the machine and had it pull only one side of the bow through the work. 
This worked extremely well and only required the root end template 
(which saves time since I hand craft each template).

I got some questions offline on what .271 meant so I'll try a simpler 
explanation.

Picture a wing tiplet or stab. If you extend the leading and trailing 
edges out from the tip, they cross (unless it's constant chord) creating 
a triangle with the tiplet root edge as the base. If this crossing is 
close enough, you can hold the wire stationary at this point and pull 
the other end (the root of the tiplet and base of this triangle) along a 
template and get a perfect core using only one template.

    Now that the Surprise II is flying, I am ready to resume cutting
    cores for my pylon ship and F3E ship.
    
    I would like to "demystify" the foams that are available.
    
    I have been using pink foam purchased from a local 84 Lumber store.
    I pay $11 for a 24" x 96" sheet.  It cuts beautifully, but when
    used for cores longer than about 2 ft. the beds have a very
    pronounced warp which makes joining/pressing difficult.
    
    I checked prices with suppliers serving the model/airplane builder
    as follows:
    
    Composite Structures Technology -  White beadboard 2"x12"x48"  - $5.35
                                       Blue Square Edge"        "  - $11.25
                                       Blue PRB        "        "  - $15.25
    
    
    Wick's Aircraft Supply(1992 Prices)- Blue Dow 2# 2"x24"x96" - $19.65
    
    Aircraft Spruce & Specialty - Blue 2# Styrofoam 2"x24"x96" - $25.68
    
    
    Since these prices are at least double what I pay at 84 Lumber, I
    assumed there must be some differences.  I talked with Gail Gawain
    at CST yesterday to inquire about shipping costs.  She said that
    their blue foam is the same stuff you buy at the lumber yard, in fact
    this is where they purchase theirs!  I really appreciated her candor.
    The shipping costs for foam is high because it goes UPS oversize.
    
    Anyway I was assuming/hoping that this expensive foam would not curl
    when hot wired.  Apparently this is not the case.
    
    My question is - Are there any suitable foams for wing construction
    that do not warp/curl?  
    
    
                                                         Thanks,
    
                                                         Jim      

    Jim, 
    
    I have used the blue foam from Aircraft Spruce & Speciality Co.
    and it does not warp.  In fact, it cuts very true using the hot wire 
    method.  
     
    I used this foam in building the VariEZ homebuilt airplane.  This blue
    foam is used for the entire airplane (wings, rudders, and canard).
    
    If you get a copy of their catalog, it describes the different kinds of
    foam and the purpose for each kind.  
    
    Hope this helps.
    
    Ollie
    

I've had very good results with the 2# Dow Grayboard recently. While 
it does curl slightly, it's nowhere near as bad as the Blue foam I used. 
The cores lay flat when pressed with a pound or more weight and the 
finish is wonderful.

Yes, UPS oversized is charged for a minimum of 25 pounds weight as a 
starting point. You have to look into one of the commercial carriers to
ship any reasonable quantity.

I was able to find the Dow Gray for $11.33 per 2x8 sheet. Sig sells
foam as well but you'll pay premium prices. I'll bet most of them are 
going to the same commercial outlets we are and then tacking on an 
additional charge for handling it and shipping it out.

    
    There has been a discussion in the internet about foam cutters..  
    (not much useful information until the following..)
    
    
Article: 18851
Path: e2big.mko.dec.com!pa.dec.com!decwrl!elroy.jpl.nasa.gov!usc!hacgate!hscw031!lew
From: [email protected] (Lyman Lew)
Newsgroups: rec.models.rc
Subject: Re: foam wings
Message-ID: <[email protected]>
Date: 29 Sep 93 19:33:15 GMT
References: <[email protected]>
Sender: [email protected]
Reply-To: [email protected] (Lyman Lew)
Organization: Hughes Aircraft Co., El Segundo, CA
Lines: 28
 
In article <[email protected]> [email protected] writes:
>
>	Thanks for all the replys to my questions about the foam wing
>cutting equipment and supplies.   even though the overwhelming majority 
>reccomended the feather cut system i think i will build the shade tree 
>version first.  If i stay interested in it then i can invest in the other.
>
>	Thanks again and remember beware the plane eating pine trees.
>
>later, Steven
>
>[email protected]
 
 
I saw the demo given by the mfg. of the Feather Cut at a seminar. Looks
very easy to use and is extremely portable. When he was all done with
it, he could store the whole unit in a mail tube. The unit is pretty
expensive and I didn't see any other benefit over my Hands-Off unit for
what I was doing. He did offer a wealth of information on foam.
Probably the most important is the phone number to Dow Chemicals which
is: 1-800-232-3436 ext. 1275 and ext. 1268.
 
These numbers are info lines to Dow on foam info and the nearest
distributor in your neighborhood.
 
 
Lyman Lew, [email protected]
 

Doesn't mean he has any in stock and he might be reluctant to order an 
entire bundle (96 pieces) but it does provide several leads.

I have been on a quest recently to find someone to take my foam scraps. 
Today I dropped off all my scraps at a place in Framingham. They accept 
white foam with no surcharge. Contact me if you want to bulk together a 
trip down the next time I go (couple of months probably)

I filled 3 of their 8'x8' bins!

    re:-1
    
    Jim,
    
       Glad to hear you are recycling.  I need to find a place to take
    my foam scraps.  They sure pile up fast.
    
    I finished up a pink foam stab sheeted with 1/32" balsa this weekend.
    The results were very satisfactory, with the weight being on par with
    the molded stab that came with the Surprise II.
    
    I received my 550 watt auto-transformer from Wick's Aircraft on Friday.
    This provides 5 AMPS and should allow cutting much larger wing cores.
    The downside is the price went up from $60.25 to $88.00(ouch!).
    Anyway, I am in this foam cutting for real at this point.  I will be
    attempting to cut 36" RG15 cores very soon.  Next will be cores for
    the Cad Cat.  Sheeting will probably be obechi.  I will continue to
    experiment with pressing kevlar sheets that were laid up on a glass
    pane.  With the flying season winding down, I will have more time.
    
    
                                                       Regards,
    
                                                       Jim

Yeah, the amount of foam was pretty impressive from a year's worth 
of cutting. We managed to wedge it into the full sized van and 
filled 3 8'x8'x6' boxes at the plant. They didn't pack the boxes 
quite a tightly as I managed the van.

This allowed me to put all my foam stock in order and reclaim a part 
of my shop from the scraps.

I've gotten the kevlar but haven't laid it out yet. I need to get 
some stuff going for the cape in 2 weeks plus I've got some car 
work to do next weekend.

You wouldn't want to sell some of that spare time, would you? 8^)

    You should see the van that Jim has. In the UK we would call it a
    "Passion Wagon". Out here it would pass as a "Pimp-mobile". Still you
    can haul about 5.62587966 cubic yards of foam in it or take it to a
    drive in movie!. :-)
    
    E.

And the foam is lighter than a water bed and doesn't give you 
rug burns!

    And you don't get seasick.
    
    

    I got a chance to try out my new 550 watt autotransformer last night.
    
    It really worked great!  I was able to cut a 36" core without any
    problems.
    
                                                            Regards,
    
                                                            Jim

Good show! The true test of your procedures is when you start getting 
to the longer cores. I still find that 48" cores take some baby 
sitting but having enough wire heat helps smooth the jaggies. It's a 
fine line between too much heat and too little and it takes some 
testing. It varies from foam batch to foam batch (density issues) 
and even more between white and gray.

I tend to cut everything with a fixed setting for a given bow length 
and then vary the template separation. I also find that C/L leadout 
clips work very well for attaching the pull strings to the cutting 
wire.

    Jim,
    
       The power supply is a Cal Rad.  It is AC with variable output
    0-130vac @5 amps.  I purchased it from Wick's Aircraft Supply
    for $88.25.  I am still using an old fashioned bow, but if I
    am nice my wife helps me.  The 36" RG15 core I cut last night
    weighs approx 1.5 oz with a chord of 8.3" tapering to 6.0" using
    pink foam.  I would like to use white foam but can't find any
    virgin.
    
                                                       Regards,
    
                                                       Jim
    
    

    I had a chance to make up some hot wire airfoil templates from
    the material sold through CST.   This is the same stuff used
    by TEKOA(Shadow sailplane, Feathercutter).  It appears to be
    some type of treated formica which is supposed to be burn
    resistant.
    
    It shapes very nicely with a file and sands baby bottom smooth!
    
    two 12"x12" sheets are $10.
    
    
                                                             Regards,
    
    
                                                             Jim
      

    Well this weekend yielded some hard but valuable lessons in
    pressed wing skin construction.  After laying in carbon tow
    spars, aileron wiring and kevlar reinforcement, I placed the
    whole thing in the press.  My basement was quite cold even
    with the heat set to 70 degrees upstairs.  Hence I thought
    it a good idea to place the press in close proximity to a couple
    of those shrouded troublelights with 100 watt bulbs. 
    
    The next morning I anxiously went to check the wing only to find-
    THE HEAT FROM THE LAMPS HAD MELTED SOME OF THE PINK FOAM!!!!!!!!!
    Distortion was minor but irritating enough thast I will redo the
    panel.
    
    So Sunday was spent building an insulated box to set over the press.
    I should now be able to layup epoxy and go to bed with the heat in
    the house turned down as we normally do.
    
     
                                                        Regards,
    
    
                                                        Jim

Yes, it's a hard lesson to learn but you've made the right decision. 
I have a 2'x4'x16' wood kiln I used to dry some rough sawn oak years 
ago. I have this set up as a 2'x2'x8' box that I put my stuff in 
during the winter months. It's built out of the foil faced foam panels 
and I can run it with a 1500 watt heater in there on a thermostat and 
it runs very little once up to temperature. I have it set at 75-80 
degrees and it worked great last winter.

The same thing can happen if you try to use high temperature film over 
the sheeted wing. I've seen some examples of delamination that was 
actually foam damage from covering.

    I pressed the first Cad Cat wing panel last night, placing my
    1" blue foam insulation box over the press with a single 60 watt
    light bulb.
    
    This morning the temperature in the box was 82 degrees.  Seems like I
    have just the right amount of leaks!  A 100 watt bulb was too much,
    raising the temperature to 90 degrees within 20 minutes.
    
    I was talking to my father last night and he had just received some
    balsa from an outfit in Springfield, Mass.  They had sent a flyer
    with the order, and he said they were offering 1/32" balsa in 12"
    width.  This sounds interesting, depending upon the price, for wing
    sheeting material.  Gluing this stuff up edge wise is a pain!
    
    Another thing I really think is a big help is to purchase rolls
    of fiberglass with the edges bound.  I use this to strengthen
    trailing edges, but the fraying of non bound fiberglass strips is 
    annoying.
    
    To prevent the obechi from splitting, I CA a narrow strip of light
    fibreglass at the root and tip of each wing skin.
    
    My press is proving not to be stiff enough longitudinally.  It should
    have had 2"x2" stock running down both sides of the 3/4" plywood.
    
    
                                                          Regards,
    
                                                          Jim
    
    
    

My Press has worked out well. I used 2 pieces of 3/4" MDO with 1x2 
in between and glued together with Titebond. Very stable.

    I have recently experimented with a variation on the "pressed glass
    pane" method articulated earlier in this note.
    
    Previously, I was using Kevlar (1.8 oz.) and .6 oz. fiberglass.  With
    the new method, I am subsitituting sheet balsa or obechi.
    
    The method is:
    
    1) Wax and buff a glass pane with pure Carnuba Car wax.
    2) Spray paint the pane with the Krylon paint color of your choice.
       Let dry for 15 minutes.
    3) Lay the .6 oz fiberglass on the painted pane.
    4) Spread laminating resin(I use West w/ slow hardener) over the glass
       cloth.  Remove excess with credit card.
    5) Lay a sheet of plastic over the pane(old monokote backing works
       well)
    6) Use a 1/2" dowel 4-5" long, beveled on both ends, to roll over the
       plastic(this forces out excess resin and pushes epoxy through the
       glass cloth, contacting the painted glass pane.  It is best to
       have the whole mess setting on newspaper, so the excess epoxy does
       not end up on your work surface.
    7) Remove the plastic.  Be careful not to pull the glass cloth up from
       the glass pane.
    8) Position the sheets of balsa or obechi on the glass pane and cover
       with a piece of clean plastic.
    9) Position a second glass pane on top of the plastic.  Place several
       books on this glass pane to press down.
    10) Wait 24 hours @ 70 degrees.
    
    The balsa/obechi sheets resulting is light in weight and completely
    finished.  This eliminates the labourous job of filling the weave
    and sanding.  
    
    The sheets may now be pressed onto your foam cores.  Leading edges
    and tips must be added and carefully faired into shape.  They are then
    coated with a thin coat of epoxy to fill the grain and painted.
    
    The advantage to using balsa/obechi over straight composites, is 
    improved sandability of the trailing edge, ease of adding carbon
    fiber reinforcement to the trailing edge, better adhesion to the
    foam core, and the balsa tends to smooth out(ie ride over) any minor
    imperfections(ridges) in the foam core.
    
    Advantages over monokote are the increased torsional rigidity resulting
    from the fiberglass, the elimination of overlapping seams at the
    leading edge, ease of repairing dings, and no more sagging film.
       
    

    For what it's worth I was using the MIG welder and had to from steel
    wire to stainless wire 309L .030 thickness wouldn't this be a good 
    wire to use for cutting foam?? 
    
    Dr. Rieth with your foam cutting buisness wouldn't this work?? You can
    buy megga ft for pennies.
    
    I Thought it might work!!
    
    Bruce

I'd have to try it out to see. The stainless fishing leader didn't work 
for me but some people swear by it. I'm very pleased with the braided 
cable since it doesn't stretch and lose tension.

Stretching and retensioning kept breaking the fishing leader.

Jim

    
    Jim,
    What is this braided wire, tell me more about it size and where can
    I get it, and cost. I like the don't stretch part.
    
    Bruce  who's still working on his ultralight!!!!

The braided wire I use is .017" diameter Control line flying wire. It 
comes in 70' rolls at hobby stores that cater to C/L fliers.

I had a reasonable supply in my basement left over from my C/L days

>     <<< Note 56.298 by GAUSS::REITH "Jim 3D::Reith MLO1-2/c37 223-2021" >>>
>                        -< Control line flying cables >-
>
>The braided wire I use is .017" diameter Control line flying wire. It 
>comes in 70' rolls at hobby stores that cater to C/L fliers.
>
>I had a reasonable supply in my basement left over from my C/L days

It also holds the muffler on his Volvo!

When I was a kid growing up in Minnesota we always thought that
bailing wire was a genuine Ford product :-)

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

With significant help from Charlie Watt and Ron Ginger, I have been able 
to assemble all the parts for my automatic cutter project. Over the next 
week I hope to get things aligned and cutting.

Ron did all the mechanical work for me and helped with some design issues
and Charlie came to my rescue when the MIT Robotics board proved to have 
insufficient power for the motors I was using. Ron finished the mechanics 
before Christmas and then we discovered the driver problem. Wednesday 
night I picked up the new driver board from Charlie and yesterday I tested 
things out.

Of course Tekoa just announced a commercial one for $3k and a place called 
Wings announced that they built one but there's something about doing it 
yourself. I wrote the software to use the .foil files from the airfoil 
program. I'm in the proocess of writing software to take scanner input 
and convert the airfoil scanned into a .foil file for cutting/printing. 
At least if I find a software bug I don't have to wait for the next 
release!

Design parameters:

The X axis uses 14TPI leadscrew and a 72 step/rev motor in half step mode 
giving a motion of 2016 steps/inch or less than .0005" per step.

The Y axis uses 14TPI leadscrew as well and a 200 step/rev motor in half
step mode giving a motion of 5600 steps/inch or less than .0002" per step.

The system is set up so I could do gang cutting but the initial mode will 
be with a single wire. The cutting area is 52" wide (this can be expanded 
if I see a need) with an X motion of 27.5" and a Y motion of 7.5". The 
cutting speed I have chosen is .25" per second since this seems to give 
the best results (angel hair - from my gravity feed cutter trials).

Alignment and first cut should happen over the next week.

    Fascinating stuff. Can't wait for the video????
    
    
    Regards,
    
    E.

Speaking of which... I don't own a camera so I'm going to need someone
to shot it for me. I'm probably a couple of weeks from that.

    Jim,
    
       Very impressive!  What are your plans for this machine - commercial
    production?
    
    I perceive a mental block among many flyers that foam wings are
    "too heavy".  If these guys would try foam and get over this
    misconception, I think the demand would really boom.  Sounds
    like you're poised to take advantage if this ever happens.
    
    If you put together a flyer, I'd be happy to distribute it among
    my local club members.
    
    
                                                    Regards,
    
                                                    Jim

Hi Jim,

Thanks for the offer on the note to you local club. I'll forward you 
something as soon as things straighten out. I'm going to put a press 
release together and send it around to the magazines.

The intent is commercial but the benefit is "spare time". The cutting
speed isn't any different than the Channel One cutter I built but the
lack of having to make templates and align them for setup will cut an 
hour and a half job to about 15 minutes. The one-of-a-kind guys are
an untapped market and I've been addressing it pretty well but I've 
been flat out doing it. This will make it as easy as the production 
cores that have stationary jigs. I will be able to cut multiple cores
with it by stacking foam and putting two stacks on the cutting area.
This will allow me to stack foam and start the cut and then do other 
things (like inspection and packaging) while the cutting proceeds. 
Currently a single wing takes about 30 seconds per surface so you have 
to stand there and load/unload foam. The second market is 1/4 scale.
None of the machines I've seen have the throat of the machine I've
got. A glider wing optimized cutter has trouble when the chord starts 
getting 20"+

I've gotten involved with a couple manufacturers that want 100+ cores 
per order so I need to automate as much as possible.

    One of the guys in my club, Dick Parshall, visited the Sig
    plant in Iowa and described their foam wing cutting operation
    as follows - "Two old ladies on either side of a bow cutting
    cores while calling out stations and talking about their kids."
    
    Gee- SIG and Jim Blum's basement use the same method, except
    instead of two old ladies it's me trying to keep my wife 
    interested in helping me!
    
    One more thought on foam.  I think pressing remains the only
    commercially viable method of skinning foam wings.  It appears
    vacuum bagging is too difficult. I am only aware of two companies
    that have offered a "bagged" wing kit - Weston and Levoe(Super V).
    I think the quality is much more consistent with a pressed wing.
    
    The all-molded wings are very difficult to repair and cost a
    lot.  This is why I have stayed away.  This is one case where
    the easiest method- pressing vs. bagging works very well.
    
    
                                                  Regards,
    
                                                  Jim  
    
     

    
    Jim,
    	Foam wings are very popular for pattern.  I'd say that almost all
    pattern ships are sheeted foam wing.  The really weight conscious guys
    honeycomb their wings and add carbon fiber "spars".  I haven't tried
    that yet but I plan to do one set that way in the near future.  Jim R's
    cutter is a very nice set of mechanics.  He should get nice cuts out of
    it once the bugs are out.
    
    Charlie
    

The report I got on Weston was that he's got retirees doing a good 
portion of his work so it sounds like another room of old people 
talking, cutting, laying up fuselages and wings...

I'm doing all pressing now and one manufacturer wants contact adhesive
on his Quickee 500 wings. This makes it go much faster. I just ordered 
a trial gallon of water based contact adhesive from 3M. One nice thing 
about it is that it's tinted so it will show up when applied to white 
foam. I tested one of the wings I did with Sig Core Bond and was amazed 
at the strength. At hobby store prices of $8 for 8oz, I had to find 
another way. The 3M stuff is $31 a gallon and cheaper by the 5 gallon 
bucket.

    Re: -1
    
    While "hi-performance" models of all types(jets,F3A,F3B, etc) have 
    been using foam wings for some time, I think the beginners should be
    building foam wings.
    
    The average beginner in my club spends 6 months putting together
    his first trainer(Seniorita, Telemaster, PT40, whatever).  This is
    his only plane, if he crashes it he may be out of action for a long
    time(job,kids,home chores,etc).  Wisely, he hooks up with one of
    our instructors.  I think the learning period is often drawn out too
    long because the instructor and the student are very afraid of the
    student crashing the plane, often breaking the training cycle for
    weeks or months while repairs are made.
    
    Since I already have the templates made, I can cut a constant chord
    12" CLARKY wing(2, 32" panels) in about 1 hr.  With a couple pieces
    of 3/4" plywood and some cinder blocks the builder can have both
    wing halves sheeted in short time.  The thickness of the wing and the
    use of polystyrene foam will not require a spar for the intended
    application.  The wings halves are epoxied together with a center
    fiberglass bandage that also acts to prevent chafing by the wing
    hold down rubberbands.  My point here is a foam wing can be built
    much quicker than a traditionally built wing.  I also think they 
    are less prone to damage on bad landings.
    
    With much less time spent building this first plane, and the ease
    of rebuilding, I think the student will not be handing the transmitter
    to the instructor as often.  This usually occurs on days that are only
    slightly windy and often the 1 plane beginners won't fly unless it
    is dead calm!  
    
    These wings mated to a "stick type" fuselage gets the beginner
    in the air with his ugly bird instead of "pride and joy" ship.
    After he has soloed the "ugly bird", the time is right to build
    a nicer, more visually appealing ship using whatever materials the
    pilot chooses.
    
    
                                                         Regards,
    
                                                         Jim
    

I agree with the concept but the average beginner doesn't have these 
options presented to him by the majority of the modelling community. 
The other benefit is that it gets the novice into the air while building 
the pride and joy and once you move to the pride and joy, it can still 
be used as a backup when there's downtime.

    Re: -1
    
    I totally agree with you, Jim.  I have actually offered to cut cores
    for a couple club members for free.  All have declined siting foam
    wings as "too heavy".  Interesting since none of them have ever had 
    a foam wing ship!  This information is being fed to them by some
    of the older club members who have never worked with foam.  I
    guess if people do things differently it is threatening to some
    personalities.
    
    I do think foam will catch on as more and more ships become available
    using it.  For better or worse, Tower Hobbies is the bible of the
    beginners in my area.  They do not feature too many foam wing designs
    (particularly trainers), so many are wary of it.
    
    Anyone who has worked with foam knows that you can build truer, faster,
    and if done properly not much heavier than rib and spar.
    
    
    

    The first thing I do when a trainer busts its wing is to build a foam
    replacement. (Span that last comment over 17 years). They are easier
    to fix, tougher and quieter. Yes quieter!. The built up wing is a drum
    just waiting to resonate.     
    
    What usually puts people off of foam wings is the lack of knowledge
    around skinning and maintenance of a foam wing. 
    
    E.

    Are not most or all ARF trainer wings made of sheeted foam wings?
    
    Ollie

and the weight problem comes from the uninformed skinning the wing 
incorrectly, typically. You'll get someone that spreads the epoxy 
on the wing (or even the sheeting) and doesn't remove enough before 
applying it. He!!, I was guilty of it with my first Panic wings 8^)

this is a problem that the beginner is going to run across and he 
too is going to come back with "yeah, mine turned out heavy too".

There are all wood ARFs (AWARFs) out there. Many of the arf's are being 
sheeted with a plastic/foam board which is difficult to repair nicely.

    
    Interesting!
    
    I would say (at a guess) that 75% of the trainers on the UK market are
    foam wing. I'm basing this guesstimate on the hassle I had buying one
    with a built up wing. I went this way because I love building, and I
    was prepared to take the risk of busting a wing that would take a long
    time to repair.
    
    Is this another example of the differences either side of the pond?
    
    Nigel
    

    Foam wings probably got a bad rap with the Dura-stuff.  These planes
    are advertised as "trainers" that can crash without damage.  Problem
    is, they barely fly at all.  They are too heavy for the wing area and
    they fly too fast for a beginner to handle.  Anyone who has flown one
    of these things knows what I'm talking about.
    
    Charlie
    

Well, I cranked on this all weekend and managed to cut some cores using 
it which I'll bring to tonight's CMRCM meeting. The quality is good but 
there's still some things I need to fix in the software. I've got a size 
problem at the moment due to my datapoints needing to fit into 16kb. I've 
got a compressed format I'm going to try next.

    Jim,
    	On the Soaring front in the UK... Our club membership (MVSA) is split 
    about 200 slope and 50 flat. I would say foam represents about 80% on the
    slope and 50% on the flat. There is a growing trend for moulded mainly
    in the F3F but also in F3J, and for those who can't afford the high
    costs they are going for epoxy bagged so the overall look is similar.
    
    I think there is a market in the UK, given our weather conditions most
    competitive soarers are not bothered about wing loadings below 10
    ozs/sq ft. I also think it has great appeal for those own designers who
    would appretiate something cut from the coordinates rather than a
    template..
    
    Keep us informed.
    
    Trevor 
    
     

    I'll second the idea that foam wings would be better for trainers.
    
    I've been very geltle on wings.  That's why I had to buy second wing kits 
    for my first two planes ;-)
    
    My first exposure to foam sheeted wings was on our club Eindecker kit. 
    Sure, it might be a little heavier than a built-up wing, but rugged? 
    This wing has been through more crashes and dorked landings/takeoffs
    than any wing I have, and it has clearly been abused beyond all
    reasonable measure.  In most cases, it comes thru with insignificant
    damage and is flyable without repair.  When it does suffer enough
    damage to warrant repair, it is much easier to repair then a built-up.
    
    I think all trainers should have a foam sheeted wing.  But then
    Goldberg, SIG and the other kit manufacturers would loose their
    aftermarket wing kit sales, so they're not likely to buy into it.
    
    -Joe  

Last night burnt some more midnight oil and I have found a compression 
method which maximizes the available space and has limited effect on 
accuracy. I calculate a MAXIMUM possible deviation from the airfoil in 
the vertical direction of .001" for a 15" chord. The deviation is due to 
a forced smoothing algorithm I'm using and is proportional to the chord.
Obechi is 24 times thicker than this!

The compression method gives me reasonably constant dataset sizes with
a proportional loss of accuracy. .002" doesn't seem too bad for a 30" 
chord 8^)

If it keeps snowing, I should be doing production cutting with it 
tomorrow!

Might even find some "spare time" under the cutting table once running 8^)

Jim (outta control)

    I was reading an old Silent Flight magazine last night where wing
    construction methods were being discussed.
    
    The author felt that many foam wings cut with bow and template were
    actually not very accurate.  He stated that the increasing presence
    of computer controlled foam cutting machines should eliminate the
    inaccuracies.
    
    While some may question this degree of accuracy, consider that 1/32"
    balsa(.03125") is almost 10 times thicker than the 3.5 oz./sq. yd.
    unidirectional carbon fiber cloth that is commonly used to lay up
    F3B wings.  
    
    The 1/32" balsa is simply too thick to accurately reproduce the
    undercambered trailing edge of an 8% RG,HQ,SD airfoil.  Wet layup
    over foam is the only viable method for the home builder to attempt
    to get this accuracy.  Accurate cores free of ridges/valleys are
    really a neccesity before epoxying $80-$100 worth of carbon to them.
    You definitely want to perfect your cutting/bagging/pressing skills
    with fiberglass before the carbon spars and skins are used!
    
    Accurate, strong, light,multi-taper glider wings present a formidible
    building challenge.  Computer cut cores are one more step toward
    simplifying this process.
     

    I came across an interesting way to make a very light, strong
    tail boom:
    
    1) Buy a hardwood tapered table leg from the hardware store($5).
    
    2) Flow coat the table leg with thin laminating resin.  Wet sand to
       a smooth finish after epoxy has cured.
    
    3) Wax the leg with several coats of mold release wax and buff.
       Spray with mold release(Freekote,Partall, etc).
    
    4) Wet out Kevlar cloth with laminating resin.
    
    5) Spirally wrap the cloth around the table leg.
    
    6) Slip an appropriately sized piece of heat shrink tubing over 
       the whole mess and shrink with Monokote heat gun(poor man's
       vacuum bagging)
    
    7) After epoxy has fully cured, cut off heat shrink tubing
       and pull the Kevlar boom off of the plug.
    
    *I have a Weston fuselage which uses a spirally wrapped kevlar
     boom and it is one stiff, light, crease resistant component.
    
    **I personally have not tried this method but it sounds like
      it might work pretty well.  I like the idea of the heat shrink
      tubing acting as a vacuum bag! 

I spent this weekend working on/with the cutter. I've gotten significantly 
behind so I needed to crank out some production. I was probably at 50% 
cutting and 50% writing new helper routines this weekend. I made so
great progress and had some of my first expected problems. One of the 
problems that came up was a broken wire. This proved to be less hassle 
than expected and I was able to get back to cutting in short order.

I managed to cut some 48" cores for an Alcyone customer and was very 
pleased to see them come out ridge free. In the past I have seen ridges 
in the middle that I always thought were due to the friction of the wire 
on the templates. This must be true because this new cutter did a beautiful 
job.

There are some interesting software issues. You can hear the resonance of
the interrupts (left vs right motors) when cutting tapered cores. Since 
the steps are the same on both sides, the tip clocks slower than the root 
but sometimes they get close enough that one interrupt has to wait for the 
other one to finish being serviced and so it gets out of rhythm. Since the 
interrupts are scheduled based on when it should have happened then the 
next one will happen closer than optimal so you get a llaaagggg-step-step
which you can hear but not see on the core.

I am finding that I'm generating more waste at the moment but that will 
get better as time goes on as well. I went through this with the gravity 
fed cutter initially.

I was able to set up a series of cores in the cutter and go upstairs and 
eat dinner last night and go back down and reload. This will work great 
on those couch potato night when I never used to get ANYTHING done. I can 
set up standard products and watch TV or whatever knowing I'm still 
getting SOMETHING done. Just pop down and switch things on commercial 
breaks. (OR I can work on my OWN planes! Something I've been unable to do 
with the babysitting of the old cutter)

Another bit of trivia that might not be important to anyone else...

Gray foam cuts at ~60% the speed of white 8^)

I was able to pack boxes this morning while the cutter cut the last 
of an order I needed to get out.

    
    Jim,
    
    Sounds like a great job!
    
    "Call 1-800-CUT-FOAM for your wing *now*"
    
    Nigel
    

    
      Your foam cutter sounds VERY impressive! Can it do rotor blades? :)

What airfoil and length you want? I don't see any reason it couldn't. 
I'd recommend gray foam.

    
    680 mm length, 60 mm width, symetrical double reflex 14% airfoil,
    double swept tips, carbon fiber sheeted. Now we just have to figure how
    to reinforce the blade roots!
    
                                      Call me when they're ready!  :)

Probably be best to lay them up in a mold made from a foam core. At 
$199.99 a set, I'd be tempted...


BTW: cutting a set wouldn't be a problem at 2+" wide.

    
    $199.99 a set!!!!!    
    
    As Emily Latella used to say:  NEVER MIND! :)
    
    
    It does say something that it is even doable though! 

No, I ment that that was what I thought you mentioned paying for those Ninja 
blades you bought.

I'd be willing to play around with it with/for you if you seriously wanted 
to try.

    
    Top of the line .60 blades run 130 - 170 dollars. The .30 ninja blades I
    bought were QUITE a bit less ($40.)
    
     You $199 is not totally out of the ball park, but $100 - $130 would
   be more in line. 
    
     At THIS point I am not serious ( am I ever? :), but NEVER say NEVER!
    :) Just giving you something to think about now that you have ALL that
    spare time! :) :)
                                                           DW2

I've got non-RC people asking me to do 3D cutting for casting metal. 
There's plenty of things to be done but I'd like to salvage some of 
the building season first 8^)

Anyway, the foam cutting would be noise level. It would be the layup 
involved and the balancing that would get time consuming. I've got 
plenty of narrow scrap that would fit your dimentions.

I can run off some cores if you'd like to investigate going into the 
business 8^)

    re: -1&-2
    
    Look at the bright side, your carbon cloth and rohacell bills would
    be tiny compared to stationary wings.  Blade molds sound challenging to
    make.

    
    Re: Blade molds sound challenging to make.
    
    Thats EXACTLY why I suggested it! I figured Jim might be getting bored
    and needed a REAL challenge! :)  ANYBODY (except me :) can cut/sheet
    airplane wings! :)
    
         

    
    Further to the dicussion on foam vs. wood wings on trainers, there is
    an interesting table in this month's RCM&E in the UK, listing
    recommended trainers (power and glider), which reveals the following:
    
    Power:
    
    Total Models	-	54
    Wooden Wings	-	17
    Foam Wings		-	26
    Both (Choice)	-	 1
    ARTF		-	10
    
    If we assume that the ARTF models are foam wing (reasonable?) then
    66.6% of the models are foam wing (my guess was 75%)
    
    For glider trainers the figures are:
    
    Total Models	-	23
    Wooden Wings	-	12
    Foam Wings		-	11
    
    So, 50% give or take. This doesn't show the percentages *built* of
    course, but I thought it might be of interest.
    
    Cheers
    
    Nigel
    
    

    re: -1
    
    I am really surprised that the percentage of foam wings was
    that high.  I would guess that only 1 model in 10 has foam
    wings at the typical club in my area.

    I saw a test  wing panel my father made this weekend.  He pressed
    60 lb. brown paper onto pink foam cores using posterboard and
    monokote backing in lieu of mylar.
    
    I was skeptical when he expressed the interest in trying this method
    after reading about it in MAN.  The MAN author used mylar and bagged
    the wing, I believe.
    
    The accuracy and finish of the panel really was quite spectacular -
    razor sharp/straight trailing edge, sufficiently stiff, with a nice
    hard surface!  The core had a 1/16" balsa false leading edge glued on
    and 1/16" balsa root and tip profile glued on the ends of the core
    before the paper was pressed on.  I think this contributed to the
    impressive stiffness of the panel.
    
    By pre-painting waxed mylar, colors should be possible. 

    A glider using the latest high tech construction material is now
    available.  A Polish manufacturer has successfully molded NOMEX
    fuselages.  Nomex is a honeycomb material that has great strength
    to weight ratio.  I believe it is used for the tail feathers of
    the F-16.  I also remember reading that Boeing knocked 800 lbs of
    weight out of the 747 by substituting nomex for end grain balsa
    used for the main cabin floor.  The stuff apparently is difficult
    to mold.  The fuselage of the 3-meter sailplane was reported to be
    "substantially lighter" than tradionally molded fiberglass fuselages.
    

	I finally got to see Jim Reith's world famous automated foam wing
	cutter in action. Jim needed a short video of the cutter in action
	to play at the hobby shows, so I borrowed my brother's 8mm camera
	and did the pilgrimmage to Southbridge, Mass. 

	The cutter is VERY impressive; made the one at the WRAM show look
	like it was designed by Rube Goldberg. It cuts wings cores like a
	piece of precision machinery. Jim says he has had several inquiries
	into buying the cutter itself, but it's not in the stage of development
	to make it a consumer product. I don't know too many people who could
	jump right into the code the way Jim does to change an occasional
	parameter! 

	As a result of his prodigious foam cutting capabilities, his side
	business has virtually taken over his house. You really can't turn
	anywhere without seeing foam, boxes, stacks of curing Quickie 500
	wings, gremlin pieces, and invoices. Jim, you need a second house!

	The video came out fairly well, considering my utter lack of experience
	shooting video (I'm a 35mm man). He says a friend of his will be 
	able to edit the tape, cut out the bad focus shots, and do a voice
	over that will mask the side comments ("Oops, that isn't right... 
	just what IS it doing??").

	Nice job, Jim. But I'm still amazed that your son asked you if you
	built it yourself. Don't they know what you DO down in the basement?

	Dave

    

Thanks Dave, for the help and kind words. Generally, everyone leaves 
me alone when I'm in the basement, I growl 8^)

The tape will get mixdown session on the 9th along with any new footage w
e feel is needed. I'll do a storyboard between now and then.

    I will have to get over and see it cut sometime soon.  I ran it a bunch
    in my shop but it was not doing anything useful then.  I too saw the
    cutter at the show and Jim's is much nicer mechanically.  Ron G. did a
    very nice job on it.  Jim's programming skills would be indespensable
    for a project like this.  Being able to quickly program new "templates"
    is the key to cost effective custom cutting.
    
    Good Job, Jim
    
    
    
    Charlie - who had a small part of this project
    
    

Don't sell yourself short, Charlie. Getting that driver board designed 
and fabricated was a critical "small" part 8^) The system was unusable 
without it. It was the help I needed at a time when I had run out of my 
own capabilities.

Dave gave me a hard time about the user interface. What's wrong with 
running an assembler as part of the procedure? 8^) The program that 
determines the steps and such generates an assembler data file that 
gets compiled into code to be downloaded to the cutter. I may at some 
point generate the object code directly but I really can't afford many 
calculations further down stream so those things get done on the PC.
I'd rather be twiddling bits than cutting templates, any day!

    I'll bet that many who have tried to do what you have done with an
    automated cutter have failed.  It requires a host of engineering and
    programming skills that are not easy to come by.  It would cost a
    bundle to develop a marketable system.  Your setup is cost effective
    and I'll bet it will be reliable.  It is much more robust than the one
    I saw at the Wram show.
    
    Charlie
    

Well, I'd be hard pressed to go back to the old system again. This 
is just so much easier. I've kept the old cutters (yes, I had two 
set up) in place just in case but I'll probably mothball them in 
the summer to make more room.

    The Reith/Watt/Ron? designed foam cutter is the most amazing home-brew
    R/C tool I have heard about with the possible exception of Franz
    Weissgerber's CNC mold cutting machine, which probably does not
    qualify as "homebuilt".
    
    I was impressed when it really worked!  Having spent hours
    filing/sanding formica templates, I understand the value of this
    machine for accuracy and production work.
    
    
    

I was a little unhappy with Wings beating me to the punch with their 
RCSD announcement but the cutter has paid for itself in not having to 
do templates alone. It's funny, I look at the cost of the Tekoa machine 
and wonder who's going to buy it. $3k is a bit steep for the average 
modeler, Clubs buying it have the problem of who gets to "house" it
once bought, and manufacturers need faster speeds than it seems capable 
of (from what I've heard). I had a conversation with Sal from NSP lat 
fall and talked about the cutter. He seemed to feel there was a market 
for 10-20 machines in that price range. I sort of see his hand in the 
Tekoa venture. I'll have to talk to them at a show some time and try to 
confirm that. I toyed with the idea of commercializing the cutter we 
built but I keep thinking of the core customers I have that pick nits 
constantly and think that my luck would be a guy that has no capability 
of doing any of the stuff for himself and running the thing commercially 
so he'd want on call debugging/support. I'd rather look at it as an 
advantage that I can enjoy and exploit it myself. Anytime I see a feature 
I think would help, I code it and use it. If I run into a problem, I work 
through it and solve it. The last thing in the world I'd want is to be 
told a bug I found in the software was fixed in the next release 8^) Sure 
it might not have the glitzy user interface Dave was hoping for but then, 
I'm more comfortable with debugging statements scrolling by to let me know 
things are working 8^)

    Lemmesee. $3000 divided by $30 a set of wings plus the cost of the
    foam.... It should take about 120 sets of wings before a person would 
    start saving money by making their own foam cores.
    
    Any one in here built a 120 wings yet???
    
    Good decision Jim. Commercializing the cutter would not be a good idea.
    
    Regards,
    
    E.

Mr Watt is pretty far along with his...

    Yes, good humor and a good spot on the typo, I meant 120 wing sets.
    
    My finger pads are very sore today after another leak in the plumbing 
    last night. (I know I should expect that at my age@). You should wait a  
    little while before you pick up a valve that you have just sweated away 
    from a copper coupling. :-(
    
    At 12.30AM you make these judgement errors.
    
    E.

BTW: Just as a point of interest...

I believe I've already cut/shipped 120 wings since bringing it up online. 
I know I've just recieved one order for 125 sets that I'll be doing next 
week. These are situations that I wouldn't have dreamed possible back in 
1990 when I built the original cutter.

Besides, you didn't figure in the value of the "spare time" 8^) I've 
actually worked on my own planes for the first time in 6 months!

    I also agree that a commercial version is not practical - even at #3K.
    The market is far too small to be worth the effort.  Jim can run with
    the software he has but noone else could.  An idiot proof software
    package would take plenty of time to develop.  The labor savings should
    give Jim an edge in the core cutting business and I doubt that anyone
    will come along with a cutter that does much better.  The casual
    builder is better off doing manual cutting or buying the cores from
    Jim!  
    
    Charlie
    

    >>> Any one in here built a 120 wings yet???
    
    No, but Jim C. is on his way......8^)

    Jim's building a wimpy 61 version. :-)
    

    So which panel are you building Jimbo?. :-)
    
    
    See, 1/2 a 120 is a 60 so only one panel would equal a.....Oh!  forget it! 
    
    Reduced to typing with my knuckles to day due to steam burns on finger
    pads. I wonder if they would take a lodger at my old house?.
    
    E.

    I was reading an interesting article about spar design in an old
    Model Builder.  The author(Francis Reynolds) is a power flyer, so
    some of the information is not applicable to glider wing designs.
    The general information presented was well written and extremely
    helpful in understanding the forces which affect a wing.
    
    Francis felt that a built up wing with D-tube was superior in 
    strength-to-weight ratio than a foam wing.  I agree with this.
    Building an accurate, stiff, 9% wing is much easier in foam,
    however.  An astute observation he made was that covering
    foam with balsa/veneer/glass of uniform thickness sufficient 
    to give adequate strength at the high point of airfoil would
    be much too thick near the trailing edge, resulting in a lot
    of excess weight without strength due to the proximity of the
    upper and lower sheeting.
    
    The lesson to be learned from this is that with foam construction,
    the sheeting should be as thin(read light) as possible with 
    other materials(ie carbon) used over the high point of the wing
    to provide strength.  In other words the "build strong where needed
    and light everwhere else" philosophy.
    
    One place that I might be able to employ this is for the trailing
    edge reinforcement of obechi covered wings.  I have been using
    fiberglass tape of around 2 oz./sq yd weight.  I have noticed that
    CST sells .5 oz/sq. yd. carbon fiber mat which I am think of using
    as a suitable replacement.  Has anyone used this stuff?  Would it
    be suitable for trailind edge reinforcement?  I am hoping it will
    require a lot less epoxy to "wet out", reducing the weight yet
    providing equal stiffness to the 2 oz. glass.
    
    
                                                   Thanks,
    
                                                   Jim

    Jim,
    	I've seen a couple of reinforcing methods for foam trailing edges.
    
    	They both sandwich additional material between the vener at the
    trailing edge for about the last 0.5".    0.5 ozs glass or mirror ply
    is used and after the vener is fitted the trailing edge profile can be
    sanded back to a sharp edge.. and then cover with whatever you prefer
    (including glassing of course)
    
    Trev 

I have a "low cost/high tech" wing cutting article in the latest RCSD.

I would appreciate any comments people might have. I would also appreciate 
any further ideas for follow on articles. I hesitate to publish a 
description of the new method I'm using since, 1) it isn't something people 
are going to run out and do, and 2) I'm not sure I want to discuss how I've 
solved all the little gotchas I've run across for the benefit of my 
competitors.

    Mags. love items that just simply impress people. Readers love items
    that stretch their imagination.
    
    My 2 c's
    
    Eric.

I talked to Judy at RCSD last night about some prizes for the glider
contest I'm CDing and asked her about this article at the time. She 
felt it was a good idea as well. Watch for it in an upcoming issue.

Now, any suggestions about the type of things you'd like to hear about?

    RCSD ?.
    

Sorry... R/C Soaring Digest, where the Low Cost high Tech foam cutting 
article I wrote was published. I've had three articles in here so far. 
It's a good publication for us glider types. I'll have some back issues 
to give away at the Wilmington show and CMRCM sanctioned glider contest 
if you'd care to browse through one.

    You may have noticed that I have not committed to either the Willminton
    or The Mall show. Obviously I am a reluctant to do so with all of the
    committments at home. As I wade through the challenges I see some light
    at the end of the task list.
    
    I keep asking for dates and times just in case I can adjust my
    schedules and take a break from home chores. I hope you "event" guys
    understand.
    
    I will resurface soon. 
       
    
    Regards,
    
    Eric.

I'm sure moving and setting up a different house presents a long 
list of "Honey do's" to deal with. I can't do booth duty at the 
Mall show due to getting set up for the Wilmington show this weekend. 
hopefully you can stop by and see us sometime during the weekend. 
You'll be welcome at the booth anytime.

    In the course of talking with an outfit called "Leroy Enterprises",
    who are advertising a 1/3 scale ASW20 and a towplane in Model Aviation,
    they mentioned a new product they will be selling in the near future.
    
    It is a waterbased method of bonding obechi/balsa to foam cores.
    
    Apparently you spread the product on the sheeting and then "mist"
    with water from a spray bottle.  The skins are then pressed as
    you normally would with epoxy.
    
    They claim it is much lighter than epoxy, non-toxic, and not messy.
    
    Sounds good, look for there add in MA.

The 3M contact asdhesive I'm currently using is waterbased and the quickee wings
have been stressed to 50gs before delamination. The only problem is the
inclusion of CF spars. I used foam safe CA but that gave too shiney a surface
tfor good adhesion. How I put the CF onto the sheeting with Titebond without
fully saturating it andf then roll on the adhesive (it's also green for easy
coverage checking) and once dry, press them. They don't have to sit in the
presses so things go quickly.

    re: -1
    
    I am not sure if the stuff they were talking about was a contact or
    slow drying adhesive.
    
    I for one would be glad to get away from epoxy.  The toxicity and
    mess bother me.
    
    I am interested to see what this product will have to offer.

    Pressing with air dry adhesive would not work well because it would be
    difficult for moisture to get out of the center of the cores.  Contact
    cement is already dry when you press and Epoxy does not have to dry.  I
    don't mind sheeting with epoxy and I like the working time to get
    things lined up and straight before it cures.  I never thought of epoxy
    as that toxic since it has little or no solvent.  I use alcohol to thin
    it.  Now Epoxy paints are another story...
    
    Charlie
    

    RE: Health Hazards of Epoxy
    
    Quoted from Wick's '93-'94 Aircraft Supply Catalog:
    
    "We have just been informed of the possible health hazards of over
    exposure to Safety-Poxy hardner 2183/84.  Burt Rutan just recently 
    brought out attention to the recent OSHA ruling on the use of any
    material containing (MDA) 4,4 Methylene Dianiline.  MDA is contained
    in Safety Poxy 2183/84 harner in sufficient quantities to be toxic to
    the human liver as well as being a suspected carcinogen."
    
    To find out the health hazards of your epoxy you would need to get
    the information from the manufacturer.  They should be able to supply
    the OSHA required health hazard information.
    
    I know several people who have developed severe allergic reactions
    from working with epoxy.  It is my loose understanding that everyone
    is allergic to epoxy, but the amount of exposure the body can 
    tolerate before a reaction occurs differs by individual.  
    
    Best to wear rubber gloves and a respirator when working with epoxy.
    I currently don't but I know I should.
    
    
    Regards,
    
    Jim 

    I'm currently working on an article describing my journey into cutting
    foam wings commercially for RCSD. I will be describing my reasoning and
    methods at each major point along the way as well as describing the
    current machine. I will share a draft of the article when it comes
    available but I'm wondering what type of information people would be
    interested in. Are hard technical facts of interest? Hints on things
    I've learned? Stumbling blocks along the way? Humorous stories? I'd
    like to make the article of interest to both people interested in
    cutting wings and people interested in a behind the scenes look at a
    hobby business. You suggestions and comments are welcome both here and
    privately in email.
    

    Probably the best articles are a combination of all of the above.
    
    For example, in giving a helpful hint, you say make sure you do the
    following or "insert humerous story here".
    
    You probably wouldn't be able to get "too" technical without getting
    off on a tangent. There's probably enough info to have a complete
    technical article all by it's self.

hi jim,

i second the "have a bit of all" idea by steve.
maybe the real hard facts in a little box, kind of the executive summary
you find in some articles.
if you can pass along the crucial bits of knowledge, that would help
to improve the quality of home-cut cores for the real hobbyist, then you will
have helped them a lot.

i think the "how to become a foam wing supplier" shouldn't be stressed that
much, unless you want to have lots of them.....

cheers
joe t.

Well, when I originally talked to Judy she left it up to my disgression. She
said if it was too long, she'd cut it into installments. She felt that there was
readership for all those areas. And as for competition... let them! The one
thing I'll repeat is the fact that it takes the hobby out of it (Dodgeson was
right). I've been recently offered the rights to three of the Gremlin knockoffs
since the manufacturers wanted out. Watch the ads. Cutting services seem to last
about 3-6 months before disappearing.

Jim

    Re Gremlin knock off rights
    
    	LET EM DIE...................The SOB's ripped off the design in
    				     the first place. Serves em right.
    
    Steve

I really don't want a "Me too" product with no name recognition. The two I
recognized were the Bird of Prey and Raptor from Texas

    Jim,
    
       When I got into R/C gliding around 10 years ago almost all of the
    designs were of built up construction.  It seems the Dodgson Windsong
    got things moving in the direction of foam wings and it really
    avalanched with the Falcon 880.
    
    Today, nearly all the popular designs are using foam wings and
    fiberglass fuselages.  Indeed, you really have to look to find a built
    up ship with larger than a 2-meter wingspan.
    
    Dr.Selig's work has played a large role in convincing people that
    accurate wings work better than innaccurate wings.  All the contests
    today are won by gliders sporting foam wings.
    
    Before foam wings, it would have been very difficult to build the new
    generation of airfoils which are so thin with sharp trailing edges.
    So the hot wire as completely revolutionized modern sailplane design.
    
    I would emphasize this in your article - the reason for using foam is
    accuracy of profile.  The core can only be as good as the template.
    Your system provides the accuracy needed to reproduce the HQ, Selig,
    RG, etc. airfoils faithfully.  An RG15 core produced from an inaccurate
    set of templates is *not* an RG15 wing afterall.  Computer cut foam
    with temperature control is accurate and consistent.
    

Most of those points are intended to be covered. I'm probably going to tone down
tooting my own horn a bit but all the reasons you state are why I started
cutting foam in the first place. I just didn't intend to be cutting quite as
MUCH of it 8^)

I cut some cores for Selig's new S4083 HLG airfoil this weekend and they're very
interesting in shape. The airfoil is thin and the rear portion is significantly
undercambered. This is definately not a "changed one datapoint" airfoil. I need
to make a wing with it for my Preditor to compare it to the S7037 I'm currently
flying.

    Let me know how it flies. Maybe the next set I have ya cut for me
    will be S4083's.
    
    S.

Well, the cores I cut over the weekend were for a customer but I intend to make
a set for my Predator soon. I'll let you know (but I wanted to pass along that
it truely is recogniably different)

    I am just finishing my first endeavor at a one-off, fiberglass over
    foam fuselage. I read about this method several years ago in RCSD in
    Jerry Slates column.  One modification I added to Jerry's method was to
    cover the foam plug with plastic packing tape and then apply a thin
    coat of car wax to the tape.  This ensures that the inside of the
    fuselage is free of all foam when melted away with laquer thinner.
    
    The fuselage has the profile of a Senior Telemaster + 10% length.
    Last night I cut out the fiberglass area under the wing and cut out
    the pink foam by heating an old hacksaw blade with a propane torch.
    I will melt out the remainder of the foam in the boom this week with
    paint thinner.
    
    I am *very* pleased with this first attempt.  I believe it will be
    light and strong.  It has a full layer of kevlar on the sides and
    a layer of 6 oz., 4 oz., and 1.5 oz. fiberglass.
    
    The wing will be modified to 9' span with flat center section and 3
    degrees dihedral at each tip.  Functional struts will be used to reduce
    the spar structure.  At this point I am planning on building up the
    wing per the Telemaster plan.  The flat center section will allow it to
    be a 2 piece wing for easy transportation.
    
    Designs like the Telemaster readily lend themselves to this method of
    construction because they are essentially straight lines.  I simply
    used to 6' pieces of aluminum as straight edges and attached them to
    the foam block with drywall screws.  I then used my hot wire to cut out
    the fuselage form.  The edges are then rounded with a sanding block and
    you have your plug.
    
    I took it to my last club meeting and it really generated a lot of
    interest.
    
    
    
    

Congrats, Jim. Sounds like a neat project. I've heard of people doing it with
bulkheads sandwiched into the plug which are left behind when it's all done. you
might want to consider the S7055 flat bottomed airfoil that Selig just finished
testing. It's supposed to have great qualities in a trainer style environment.

    I'll have to wait till the foam is out of the boom to see if any
    bulkheads will be needed.  I do not have any bulkheads in my other
    towplane(Major) which came with a fiberglass fuz.  In fact the lack
    of bulkheads is what I like about FG fuselages, it allows you complete
    freedom in equipment positioning and greatly speeds up construction.
    
    The Telemaster uses a lifting stab which I think counteracts the large
    angle of attack that the wing is set at.  I really don't like the
    design but it appears to fly well for my purposes(towplane).
    
    I will be anxious to see hjow it flys with my mods to the wing.
    
    A Moki 1.8 turning a 20x6 or 20x8 prop is planned.

I've also seen control linkage tubes installed "along the wall" by letting them
into the plug. I'll be looking forward to hearing how it works out. I've only
tried that method once and didn't have the fiberglass technique to do it well so
I ended up trashing the end result. It's something to consider for the future. I
almost think I'd rather put the effort into a female mold if I was going to
spend as much time doing a plug but I haven't had a chance to do that either 8^(

    I've gotten good reports back on a new foam supplier out in Syracuse
    NY.
    
    Thermal Foam
    (315)  699-8734
    
    They manufacture the foam so my ability to get consistant quality and
    proper bead size should improve

I can't find a mention of this anywhere - but this conf. is so big...

I attended the recent model exhibition at Sandown (UK) and took a 
long look at the Robbe (I think) Dash. This is an all foam, 4 motor 
electric civil airliner of about 6-7' wingspan - all 
dimensions are guesses!! What struck me as interesting was the way 
the fuselage (molded foam) was ready at accept radio and electrics 
etc and it struck me that molding foam in this way is an excellent 
way of producing quick and light fuselages for bulky areoplanes (like 
the Dash). Just the musings of an (almost complete) armchair modeller 
- but does anyone know how such moldings are produced and can it be 
done "at home"?

Keith.

hi keith,

i do not think that it is possible to do foam molding at home.
you need the machinery which provides heat, pressure and so on.
the mold must withstand the pressure, so it must be something sturdy,
heavy = expensive.

otoh you can build fiberglass in molds at home. no problem.

have fun,
joe t.

    Joe,
    
    Thanks for the reply - wishful thinking on my part, I guess! The
    question came about from an article I read a long time ago that gave
    details of how to fill the bouyancy space in boat hulls with expanded
    polyurethane foam which was mixed from two liquids and then poured
    straight into the hull, whereupon it "foamed" and expanded to fill the
    available space. Actually, the article was all about how not to use too
    much and so prevent the hull being blown apart! Anyway, given a
    suitable mold, this seemed to offer a potential way of molding foam,
    but now I seem to remember warnings about using polyurethane as opposed
    to polystyrene...? Maybe best to stick with balsa ;-)
    
    Keith.