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Old Mar 30, 2007, 01:37 AM
highflyer
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Quote:
Originally Posted by peterangus

Excellent..really cool way to do it from balsa and ply.
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Old May 18, 2007, 07:38 PM
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Hello!

The fuel glow does not attack foam?

Please send-me more info about Formosa glow.

Tanks!



Quote:
Originally Posted by Heli4life


Please email for further pics or info.

Paul
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Old May 18, 2007, 10:48 PM
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Delta, BC, Canada
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Quote:
Originally Posted by Armando Bianchi
Hello!

The fuel glow does not attack foam?
...
That's correct, glow fuel does not attack bare Expanded Polystyrene (EPS) foam.

Lot's of 1/2A planes used EPS foam for just this reason. E.g. the old Cox/Kyosho planes were all EPS and ACE hobbies had a whole series of planes that used the ACE foam wings.

If you want to paint the foam, it can be tricky to find a paint that is both fuel-proof and compatible with the foam. However, even that's solvable if you know a little trick... first paint the wing with a mixture of White Glue (PVA) and water (and food colouring to see where it is.) Done right, once dried it forms a barrier that will allow you to use almost any fuel-proof paint without the risk of the solvents in the paint melting the foam.
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Old Jun 14, 2007, 09:22 PM
Oldie but goodie
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Both were originally Cox .049 powered (Reed Valve and TD). Have been in storage for the last 18 years and recently resurrected and electrified (sorry Guys).
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Last edited by Popsracer; Jun 15, 2007 at 08:40 PM. Reason: updated picture
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Old Jun 20, 2007, 11:40 PM
a.k.a. skcope
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Trumbull, CT
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Modified Bee-tween

Here are some pics of my modified Bee-tween, a Randy Randolph design. I call it the Pee-tween as I used a color scheme to resemble the P-26 peashooter from the 30's. I built the ribs up using the Fulton Hungerford sliced rib technique. This is the 3rd Bee-tween I have built and I highly recommend the design. Power is a Cox .049 Texaco w/6-4 prop.
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Old Jun 21, 2007, 11:37 AM
feel no remorse
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Skcope where did you get a wooden prop of that size? Can you point me to it?
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Old Jun 21, 2007, 12:05 PM
a.k.a. skcope
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The local hobby shop had it in stock. The brand is Zinger; Tower Hobbies has them in stock for $2.09 (http://www2.towerhobbies.com/cgi-bin...Q0803&C=QBAZIN) if you can't find it locally.
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Old Jun 21, 2007, 09:05 PM
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Quote:
Originally Posted by skcope
Here are some pics of my modified Bee-tween, a Randy Randolph design. I call it the Pee-tween as I used a color scheme to resemble the P-26 peashooter from the 30's. I built the ribs up using the Fulton Hungerford sliced rib technique. This is the 3rd Bee-tween I have built and I highly recommend the design. Power is a Cox .049 Texaco w/6-4 prop.
Great looking plane you have there!

Could you explain the "Fulton Hungerford sliced rib technique"? From looking at the pictures, I'm guessing that you use a template to make slices for the top and bottom of the airfoil, then build up the rib internals with sticks?

Also, I notice in the tail that you've opened up into a symmetrical airfoil. How did you do that? Again, just guessing did you build it all flat (being careful to not glue the top and bottom ribs together) and then insert the spacers once later? If so, how do you not get warping or top-bottom asymmetry during covering?
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Old Jun 21, 2007, 09:34 PM
a.k.a. skcope
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Sliced rib technique

Groundfx-
This technique is very simple. It was developed by Fulton Hungerford who produced some breathtaking rubber powered planes in the 70's and 80's using this technique. It produces light, strong, beautiful "built-up" ribs. The ribs are built from slabs of 1/16th balsa glued up into the shape of an airfoil. The grain orientation of all the balsa is kept parallel so that once the "slab" is complete, you simply use a flexible straight edge and slice off ribs with a razor or x-acto knife. The diagram I drew should give you a rough idea. The top picture shows the pieces of 1/16th w/o the top sheet added (I darkened the edges of the internal structure for clarity; I hope ) The main thing to remember is the grain orientation or you will have a bugger of a time trying to slice the ribs. The tail ribs were built the same way, with only one upright piece which creates that symmetrical cross-section. Try the slab and slice technique; it's a nice alternative to tracing templates and cutting out each individual rib.
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Old Jun 21, 2007, 09:55 PM
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skcope,

Thanks for the drawing. It's a totally different approach than I was expecting. It also explains why the tail is the way it is. I couldn't understand why you didn't just insert a continuous spar and instead had all those independent uprights.

I'm not sure I fully understand the details of the approach, so just a few more questions if you don't mind.

Did you wet and form the top and bottom planks over a form to get the wood to hold its curve or did you just build it up and hope for the best in terms of spring back?

The ribs on your Bee-tween look thicker than 1/16" inch on the top and bottom parts. Did you laminate to get greater thickness or did you use a thicker plank?

Any tricks regarding slicing and keeping the blade vertical? Is a bandsaw (and then a sanding block) a better way to go?

Thanks
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Old Jun 21, 2007, 10:27 PM
a.k.a. skcope
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Groundfx-
The balsa sheet should be glued first at the trailing edge and allowed bond thoroughly then gently bent over the top of the structure. No need to wet the wood if working with 1/16th. I just looked at the structure and the sheet used was definately 1/16th although the actual thickness of the ribs (width) is more like 1/8". A bandsaw may work well although the grain orientation would still be critical to avoid tearing (I don't have a bandsaw so I've never tried it that way). A razor saw would also work. I'll try to dig up a good picture of the technique to shed some light.
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Old Jun 22, 2007, 03:52 PM
a.k.a. skcope
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Here's a picture of the technique I printed off of the AMA website (from a 1980 issue of Model Aviation). It hopefully shows the technique with a bit more clarity.
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Old Jun 22, 2007, 07:16 PM
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Great, thanks for digging this up. I'll have to try this technique when I get into my Fall building season.
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Old Jun 24, 2007, 10:02 AM
a.k.a. skcope
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One final thought on the sliced rib technique- a jig is not absolutely necessary if you are using light balsa sheet, especially if the airfoil is flat bottomed. In fact, I have never used a jig.
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