Folks,

After modeling for 40+ years I have come to the resolution that glow fuel used or unused will contaminate balsa and plywood over time. The best protection I have used to combat the fuel soaking into the wood is very thin 30 minute epoxy. The first coat is critical. You want the thined epoxy to be absorbe by the wood much the same way the wood absorbs the fuel. Once the thin coat is absorbed the fuel proofing is very effective. I have learned that thick coat material like finishing resin, non thinned epoxy, polyurethane, etc. don't work as well for a first coat over the long term. You can apply several thin coats of epoxy and hopefully you have reached all the vulnerable spots. The point is to not let the fuel penetrate, with a thick coat only, there always seems to be a point of failure, and the fuel finds it, and undermines the thick epoxy, etc. coating. Using the very thin coat first will get the protection beneath the surface of the wood ahead of any fuel seepage. Yes, thicker coats over the thin coat/s can't hurt. Try sticking a piece of balsa sheet into a pan of water. Watch how the balsa absorbs the water. The fuel does the same thing. So try sticking the balsa into a solution of very thin epoxy ( like water) it will absorb it also. When it dries, it will not absorb any more water if you place it into the water again. Protection at its best.

Sledge_78