I have not flown for several years and thought it a good idea to build a kit before flying again. This to remind me of the finer points of flying. One of the things I have forgotten is the use of epoxy to seal the firewall. I remember that in mixing the epoxy one could thin it to allow more work time and to allow it to be brushed smoothly onto the firewall. This all to fuel proof the engine compartment.

The question is "what do you use to thin the epoxy?" I appreciat your help.
Dave14

Alchohol. About 50 50 mix.

I use rubbing alchohol aka isopropyl alchohol. 50 50 mix is about what I use also. You may want to consider coating the fuel tank compartment also just in case the tank burst or a line comes out. I have a friend that failed to do this on a scratch built plane recently and the tank burst. The area under the plane deteriated in no time.

Welcome back to the hobby.

Welcome back Dave14,I'm as the others with alchohol,I thin it till it paints on easy,usually 15 min epoxy,gives me time to clean up mistakes.Also 50% alchohol has more water than 90% achohol,all, works takes 50% a little longer to set.If you want some color just add food coloring to the mix.

I've never had any luck at all thinning epoxy, and I've read articles by epoxy makers saying not to do it. I know lots of folks say its the way to go, but I'd much rather use material made for the task. Get a quart of epoxy finishing resin at Home Depot, and you'll be set for the next 20 planes you build.

I heat mine up and it runs nicely. Just remember to protect the t-bolts from getting in.

Bob aka Nuker

I use the alcohol too. makes it nice and thin so you can paint it on the firewall and coat the inside of the fuselage where the tank goes. It's also good to "epoxy paint" joints in the fuse/wing that you want to strengthen without adding a lot of wait.

And definately protect the threads of your t-nut from the epoxy. trick that works real well for me is to drip candle wax into the threads. this will keep the epoxy out, and you can either drive the wax out with your bolt or heat it and it will flow out.

My 2 pennies worth

All great input. Thanks much to all.

On trick I learn in making underwater enclosures to keep the epoxy out of the treads is to get a few extra screws and coat the screws with silicone grease or petrolium jelly and tread them into the T-nuts. When you are done the screw will come right out and leave the treads un-clogged. One thing to watch is not to let the epoxy build up around the screw. If this happens and before it sets off you can remove the excess easily with a cotton swab. Hope this helps.

Welcome back Dave14: It's almost as if you were never gone. As far as thinning epoxy I tend to agree with pinball, I save my glue for gluing, and use finishing resin for fuel proofing, and alcohol for epoxy clean up. I use Vaseline (there's some ammo. guys) in the threads of blind nuts, but I also coat the bolts entirely before I thread them in, then just rinse them off with warm water after fuel proofing. Most definitely do the fuel tank compartment as well, you won't regret it, even if there's no fire it will keep the wood from getting saturated, much easier to clean up. I also use Vaseline on hinges to keep them from locking up when you glue them in. Or if using easy hinges, (the ones that are made of a fibrous material, with no actual hinge to speak of,) use a wax pencil, and draw a line, across the center line at the hinge point on both sides, this will keep them from hardening at the hinge line. always glad to help if I can. Garry

You can buy a ready-made thin epoxy: Bob Smith Finish Cure. It is intended for fiberglassing and sealing wood. I always use it on the front side of my firewalls. It is necessary to reheat it with a heat gun a few times in the first two hours after applying to insure that it will cure properly. For the back side of the firewall and the fuel tank compartment I use two coats of Balsarite to seal the wood.

Dave Segal

Ya don't need any thinner.

A hair dryer on high or a heat gun on medium will thin that epoxy to a water like consistency without any thinning. Just work fast because the heat helps it set up quicker. 5 minute takes about 1 minute and 15 min speeds up to about 3 minutes. One hour stuff only slows down to about 50 minutes unless you keep the heat on it for quite a while.

And welcome back to building......