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Hi Scott
Re your question on epoxies:
1. I don't think there should be any real problems with one epoxy vs. another but you should get their data sheets and select one with better elevated temperature properties. The Jeffco is 190 degrees F on the HDT (heat Distortion Temperature which is pretty good but there are a LOT better ones. If you want a higher HDT, I'd call Rich at Applied Poleramic in Benecia, California. They do small runs but have also fabricated high temp stuff for Boeing. And they actually are reasonably priced. Down side is most higher HDT resins need a post cure to get good performance but a carboard box and electric heater should suffice.
2. As to low temps, they all work if you keep them dry (i.e. the dew of of them) but they are abitch to work with. VERY slow to wet out. And they should get some high temp before use to make sure the cross linking is complete. Not ncissarily a lot but 70-80 degrees for a day of so at least should do the trick. More is better by the way.
3. E glass vs. carbon. If the part is stiffnes driven, as I believe it is, carbon has it all over glass. It would take three times the glass to equal the same stiffness as one layer of even the low performance "standard modulus" carbon. Are you intending it to be all carbon or will you core it?
Let me digress a bit here. You can add a LOT of stiffness with a little core. One product that I've used a fair amount for small areas that are too complex or high temp for foam or honeycob is called "Coremat". It is kind of heavy at between 30 - 45 pounds a cubic foot but still a lot lighter than solid laminate. It is basically a resin sponge with lots of fiber and filler. The amount of absorbed resin determines the density. But since stiffness is a function of the cube of the thickness, (actualy the distance from the neutral axis), a little thickness goes a long way. So I'd say the 4mm would do well and save a lot over a bunch of carbon. And it's cheap by the way,
4. You bring up a good point with electrolosis. I'm having to replace much of the deck hardware on my 37' racing sailboat due to electrolosis, (it's an all carbon boat). It lasted a long time but now I'm adding galvanic isolation mounts of glass. You can do the same. I'd recommend drilling out the mounting hole oversize, filling with glass and epoxy and then taping over that with some E glass tapes.
Good luck!
Dan Newland
ES #61
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