I am just getting ready to cover my 4*40 kit and was wondering if I should fuelproof the compartment that the fuel tank sits in. On the 4*, there is no hatch that the feul can leak through on the top. However, fuel may come through the hole in the firewall that my tank hoses go through. Any thoughts? Seeing the sheeting is all done, I'll have a "fun" time getting the compartment feulproofed, but it is doable. Also, when I fuelproof the firewall and front end of this thing, I think I'm going to just use epoxy. Is this satisfactory? My trainer (ARF) already had this done when I bought it, so this is my first time. Thanks for the help

Hi samsdad, i'd recommend fuelproofing the entire compartment where the fuel tank is located with epoxy watered down with a little denatured or rubbing alcohol (turns the epoxy watery and makes it easier to paint on). Although no fuel may get in from the engine exhaust or through the firewall if your fuel tank ever leaks you'll be glad you did it.

I agree. If you don't want to thin with another chemical, you can heat epoxy with heat gun or blow dryer (not a torch).

John 373786

I use Balsarite for fuelproofing and to help the covering stick better. Light weight, goes on easy, and dries quickly.

Sounds good guys Thanks for the replies

I use a couple of coats of water based Poly. Easier to use and fuel proof to boot.

I also like to fuel/oil proof some areas that will get hit by the exhaust. Prior to covering & assembly, I oil proof the right aileron where the torque rod is imbedded into the balsa. I also proof the area where the torque rod exits the trailing edge of the wing. I like to use Robart hinge points, so I proofed around those holes on all the flight surfaces. I also proof the fuselage around the local area where the leading edges of the vertical fin and horizontal come together. On my 4*40, these are all areas that are covered with oil after a day's flying. In a perfect world, covering and final assembly would seal these places against oil, but I've learned the hard way that it's hard to be perfect - oil residue only needs the tiniest of openings before is starts to soak your balsa.

Good luck, Gary