Warbird Information Exchange

See my first reply above.
However, their Production Certificate, and any field approvals using 337s for the use of epoxy are issued on an individual basis, and are not considered "approved data" that would cover anybody else trying the same thing. You can use a 337 from a different district in an attempt to get one approved by your local feds, but they don't have to go along with it. Some will and some won't, which seems like inconsistency, but only if you're trying to apply logic to the FAA.......

As a footnote, any 337 field approvals that were approved before October 1, 1955 are considered approved data, and the repairs or mods can be replicated and approved by an IA without needing your local feds to get involved. Obviously not a part of the epoxy issue. I guess that the FAA thinks that their predecessors were smarter then than they are now...?


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http://www.biplanerides1.com/

When I built my Falco, I used Aerolite, the same glue that was used to build Mosquitos. It was then entirely moisture-sealed internally with a coating of epoxy varnish. I used West System epoxy for convenience in places where ultimate strength was not a consideration. Why? Because all epoxy glues weaken under heat. Had I built the airplane using even as excellent an epoxy as T-88,I would have had to paint it white; any dark, heat-absorbing paint would have been a risk. (What if I needed to park it on a ramp in Phoenix for a week during the summer?) So I was able to paint it gray and red, in an Italian military scheme.

This is true of all epoxy-resin based composite aircraft as well, which is why you'll never see a high-performance sailplane in anything but white.

There are a lot of aerobatic aircraft out there that have wooden wings built with epoxy, some painted dark colors, and I've never heard of one coming apart because of this. I think that one of the problems with composite aircraft is that the epoxy component is part of the surface of the aircraft, and subject to direct sunlight, rather than being internal structure.




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http://www.biplanerides1.com/

A good example of this would be the Slingsby T-67's the USAF bought a bunch of years ago. After some big engine problems, they discovered some structural problems that were temperature related. They ended up with a pre-launch structural temperature inspection requirement. If any of the inspection points had a surface temp of greater than 100F, the a/c had to go back into the shade ports until it was below that temp. Being that they were based in Hondo, you know how that went over.

Modern composite aircraft use epoxies that are well characterized (known mechanical properties). Generally, epoxies cured at 250F have a service temperature of 180F, while 350F cure epoxies have a service temperature of 250F.

Thermal issues usually occur with room temperature cured epoxies. An important property of epoxy resins is "glass transition temperature." Above this temperature epoxies can be substantially weaker. Fortunately, these things can be dealt with. More bonding surface area results in lower stress at the bond line, and of course wood isn't very strong to start with compared to metals so the wood generally fails before the bond line.

http://www.permabond.com/2015/09/01/tg- ... mperature/

If you feel your black-painted wooden wing can get up to 160F, go ahead and compare results from casein or resorcinol glue joints to your epoxy test joint heated to 160F and let us know which fails first. Do tests to failure in tension, peel and shear. You have to be better in all 3!