epoxy
 

Iv used both 5 and 30 min epoxy and there both very Strong but i have never done a stress test on either. On all my kits and ARFs i use 5 min epoxy on the less structural areas like the impenage and radio trays exc. but always used 30 on atleast joining the wings and firewall, but theres so much time diff, between 5 and 30 min that im just itching to use the 5 on all parts except maybe the firewall. Has anyone used 5 on Major structural areas befor if so did it stand up to any rigorous flight conditions? THANK YOU

RE: epoxy
 

Can anyone second this? Iv been modeling for some years now and used this method alot. I have never lost a model from lose or malfunction of flight controls and im a sport flyer that puts my planes through alot of torment.

RE: epoxy
 

Personally, I would NEVER use 5 minute epoxy for anything except fuel-proofing. 5 minute epoxy cures too quickly to soak into the wood grain, and often creates a "surface-strong" joint. It looks good, it feels good, but it may well pull loose under stress. Epoxy is also HEAVY!

I've used CA exclusively for all my models for about 15 years. It works well on everything from competition fun fly to pylon racers to a giant scale Stinger. If I were to use epoxy, it would be an overnight (12 hours or more) set type, and I'd drill penetration holes in the wood pieces.

Dr.1

RE: epoxy
 

I'm with DR1driver, I never use 5 minute epoxy for anything requiring structural strength. It is to easy to try to use it after the chemical reaction has progressed to far resulting in very poor performance or strength.

RE: epoxy
 

There was a study reported somewhere in the modeling media within the last few years doing strength tests on wood joints glued up with all the usual types of modeling products. The results confirmed my general suspicions, that the wood will fail before the glue joint fails, no matter what the wood or glue. Even crappy ARF hot-melt joints are hard to pull apart if they're joined well to begin with.

That said, I've had CA joints fail because of brittleness of CA relative to epoxy. If a joint is likely to be exposed to shock stress, use epoxy. Same thing with vibration stress, as in the firewall. Plus epoxy can be filleted with a popsicle stick or latex-gloved fingertip if you thicken it with colloidal silica, which is a marvelous additive (keeps the epoxy from running or sagging while curing).

Structural joints that will end up being covered over with film or glass are less critical in terms of joint strength than those that depend on glue strength alone. The monokote/ultracote skin is a wonderful stress distributor.

Hardworking joints like firewall, landing gear mounting plate, joining wing halves, wing-mount blocks--these get epoxied and cured overnight. Gluing in tailpieces, I've used both CA and epoxy, and yet to have a tail-joint of mine fail--BUT I have seen them come loose on other models, so you do need to be sure you get complete adhesion, fill all cracks and crannies. If a tailpiece needs bracing into alignment, obviously epoxy is the way to go, at least 12-minute cure to give you time to line everything up.

RE: epoxy
 

Hi!
I nearly never use the stuff! I glue everything with Flash Ca glue.

RE: epoxy
 

That said, I've had CA joints fail because of brittleness of CA relative to epoxy.
Gee, your planes must vibrate a lot. I've never experienced that type of failure of a CA joint.

Hardworking joints like firewall, landing gear mounting plate, joining wing halves, wing-mount blocks--these get epoxied and cured overnight.
Ah...no. About 15 years ago, I built a giant Stinger usnig CA exclusively. Through three owners it's still flying with no structural problems.

Structural joints that will end up being covered over with film or glass are less critical in terms of joint strength than those that depend on glue strength alone. The monokote/ultracote skin is a wonderful stress distributor.
It may be, but I don't rely on the covering to hold my framework together in the air.

All that being said, ANY joint should be as mechanically tight as possible BEFORE the glue is ever applied.

Dr.1

RE: epoxy
 

I have to believe that the glue is stronger than the wood;)

RE: epoxy
 

We had a guy from the makers of Elmer's glue do a demo at our club meeting15-20 years ago.....he glued two pieces of wood together with 5 min. 15 min epoxy and some new stuff from Satillite call 'thick CA'. Oh, he also glued the same sized pieces together with Elmer's White glue.....at the end of the meeting he tried breaking the pieces apare and the wood on all of them failed, even those glued with Elmers - although he admitted it wasn't quite dry yet :)

Yeah, the wood will fail....next time examine a wrecked plane in the garabage can at the flying field and do your own experiment!