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Building Tips and technical articles. => Building techniques => Topic started by: Jim Thomerson on May 02, 2009, 10:27:04 AM
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Article in latest Flying Models by Dee Rice on making stressed skin composit wings. Very interesting. Also a Pathfinder construction article and Allen Brickhaus talking about his electric Clown. Of course we are all subscribers, right? D>K
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Sorry, no. Some of us can't afford it! grrrrr
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Great article. Great wing design with lots of benefits:
* Easier wing templates since no cut outs for coring are needed
* 4 pound balsa is not really needed since there is weight saving with the removed foam
* Materials are not hard to find or expensive. Carbon tow is available on the bay at decent prices. Most already have it.
* The balsa shear web which has grain top to bottom can be made from sheeting cut-offs
* No balsa grain to fill. You will have fill the fiberglass.
It's one of those ideas that make you go "Why didn't I think of that?". I also wonder if there is a benefit to: replacing the balsa shear web with ply or using a molded Bob Hunt type leading edge?
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I cant get that magazin here in New Zealand - can anyone buy me a copy and post it over?
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I'll send you mine... just drop me your address to icerinkdad@aol.com
Bob Furr
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How about a photo just to show what your talking about ?
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I would like to see a copy of that article as well, very rarely see Flying Models in England these days! Is there a problem with copyright, that a scan of the article can't be put on here?
Cheers Neville
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Is there a problem with copyright, that a scan of the article can't be put on here?
You nailed it Neville.
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I was just hoping for a picture of a wing not the whole article...
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Perhaps Dee has pictures that weren't used in the article.
Basically he placed carbon fiber tow running from front to trailing edge, spaced about 2 inches. These strips of tow were about 1/4 inch wide. They were empregnated, with epoxy, the core and skin were also coated, then placed, covered with the outer sheaves. They were weighted, and allowed to cure over night.
The next step, was to use a hot wire, and remove the foam, right to the underside of the Carbon fiber tow. The tow acts in a way like ribs to stregnthen the skin.
He left a center foam beam running the lenght of the panel like a normal foam wing.
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Ok, that kinda explaines it. Just had no clue what kind of wing we talking about. Beside using carbon.
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One other point that Dee made was that he took great pains to find the proper epoxy resin, it needed to cure rigid unlike some of it that cures sort of rubbery. He also left a small section of foam at the trailing edge go stabilize that as well.
Of note is that the cores were not epoxied to the foam, but they were coated with glass and epoxy on the outside which then became the stressed skin. At least thats what I got out of it
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I've been told that this method was used in making wings for RC pylon racers back in the 1980's. One difference was that a solvent was used to dissolve out the foam rather than hotwireing it out.
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I've tried the dissolving foam with solvent way back when. WHAT A MESS! Coring with a hot wire has got to be much cleaner. The worst part was not being able to get all the sticky residue cleaned up.