I was reading some posts about the Ultra Stick .60 from Hangar 9. It was suggested to pour some thinned epoxy into the fuse around the firewall. This would be to reinforce it. How do you thin epoxy and would it help?

There are a couple of ways to thin it. I'm not familiar with the plane you're talking about so I don't know how you would accomplish pouring thinned epoxy and getting it to stay where you put it...but- I guess I'll let you handle that part.
The first way is to mix the two part epoxy thouroughly, as usual. Mix it in an unwaxed paper or plastic cup. Add a little denatured alcohol into the cup and stir thouroughly. Keep adding alcohol until the consistancy is where you want it. Do not try to add the two parts of the epoxy in the alcohol independently. It must be mixed first, then the alcohol is added last.
The second way is to heat the epoxy. Again, mix first then heat. You can use a heat gun or heat it very, very carefully in the microwave. Needless to say, you could ruin a microwave this way if you're not careful.
For both of these procedures, slow drying epoxy is superior to 5 minute epoxy. Also, thinning epoxy increases the drying time drastically but the strength is unaffected as far as I've been able to tell. Don't be alarmed if it stays tacky for several days. If you've mixed it properly, it will dry eventually.

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<hr>Originally posted by: G.F. Reid
The second way is to heat the epoxy. Again, mix first then heat. You can use a heat gun or heat it very, very carefully in the microwave. Needless to say, you could ruin a microwave this way if you're not careful.<hr></blockquote>

put a glass of water in the microwave together with the glue. This will absorb some of the energy & makes the process a bit more controlled.

Cheers,
Maarten

Just mix up some 2 hour epoxy. its almost like corn syrup mixed with water already... no need to thin it. Heating will thin it a bit, and will sped the cureing.

2 hour epoxy generally takes overnight (up to 2 days!) for the surface to quit being tacky. Don't worry about it.

I advise against thinning epoxy with alcohol. You can make the epoxy "spongey" It can feel almost like rubber and be porous enough that its worthless for fuelproofing. Its too easy to do it wrong. Use 2 hour epoxy instead.

To specifically answer your second question, "would it help?" though, yes. I'd advise that any R/C plane with an IC engine (whether it's glow, diesel, or gas) should have the fuel tank compartment fuel proofed. The design of a Stik resists frontal impact with compressive forces -- for which the additional epoxy won't help much, but if the joints aren't perfect, it will make the whole thing a bit stronger in some ways.

For another application option, some of the home improvement stores around here have taken to carrying sprat-on epoxy paints. They go on real easily and seem to fuel-proof things just fine.