>Epoxy dose not stick to GLASS. >Try gluing some epoxy to a mirror (reflective side - plz) and see how easily >the epoxy peels off the mirror, after cured. (Larry Capps) +++++++++++++++++++++++++++++++++++++++++++++++++++
If my "hard-shelled" foam had a mirror finish, even I wouldn't try glassing to it. Fact is that isn't the case. On my "hard-shelled" foam I saw plenty of surface irregularities for the epoxy to bond to and appearantly that was the case. (L.Flesner) ++++++++++++++++++++++++++++++++++++++++++++++++++ >As for testing which is stronger, were not talking about grabbing a handful >of glass cloth, epoxied to foam, and pulling to see which is stronger. Were >talking about the bond between the cured fiberglass top layer and the >hard-shell. The test I'm looking for would be to insert a balloon between >the Epoxy/GLASS (hard-shell) and the cured Epoxy/Fabric layer and inflate. >Isn't this what's going on during extreme temperature changes and differing >atmospheric pressures? (L.Capps) >+++++++++++++++++++++++++++++++++++++++++++++++++++++++ Isn't that basiclly a peel test? As I see it, for your concern to be valid, you would have to have pockets of trapped air between the "hard-shell" layer and the epoxy/fiber layer. I can't imagine doing a layup that poorly and then flying it. I don't see any factor to start a "failure mode" here. It seems to me our concern with the epoxy/fiber to foam or "hard-shell" bond is stresses in shear and peel. In either case, if the foam fails 100 PERCENT of the time before the bond fails, why do I care if the bond is only 1 percent stronger than the foam ,as your logic might suggest, or X to the power of 10 times stronger than the foam. When I recently pulled a 1 foot by 7 foot section of glass off the bottom of my left wing to get to the tank, it pulled 100 percent foam. There was absolutely no spots where the epoxy/fiber pulled from the "hard-shell". (L.Flesner) +++++++++++++++++++++++++++++++++++++++++++++++++++++ >Maybe someone could show me where it say's, the best way to get a secondary >bond on cured epoxy part is to do nothing, no sanding, no washing, no >wiping/vacuuming - once cured just add more epoxy and your good to go. I'd >luv to see that. (L.Capps) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ I had heard and read that you don't try to bond epoxy to epoxy without some prep. In my quest for knowledge I tried it. I took two pieces of whith pine and painted on enough FPL-16A epoxy on each piece to have it cure with a very shinny finish. After curing I painted on some more FPL-16A and clamped the two pieces of wood together. When cured I tried to separate the two pieces. The failure point was entirely in the wood. I'm not saying this is the strongest possible bond but it was stronger than the material being bonded and that's my point with the method I used for "hard-shelling". (L.Flesner) +++++++++++++++++++++++++++++++++++++++++++++++++++++++ > >Also, could someone be so kind as to show me where it says, Epoxy sticks to >GLASS - It would really put this whole, should I or shouldn't I hard-shell >to rest. >Larry A Capps ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ So what keeps the micro balloons in the filler from falling out all over the shop floor? :-) Larry Flesner ++++++++++++++++++++++++++++++++++++++++++++++++++++++ >"Good judgment comes from bad experience, and a lot of that comes from bad >judgment." >+++++++++++++++++++++++++++++++++++++++++++++++++++ So far I've had no bad experiences with my "hard-shelling". Does that mean I used good judgement? YOUR RESULTS MAY VARY. DO YOUR OWN TESTING. Larry Flesner
