I have a Hangar9 Ultra Stick 40 that I am putting floats on for my first float fly in April.

Question : Should I coat the inside of my fuse to waterproof (water resistant). If so, with what?

Thanks everyone, love your board.

James

You really do not need to waterproof the inside of your fuselage or wings unless you plan on playing submarine with your aircraft.
Unless you have a major crash (hope not) you are not going to get enough water in the fuselage to worry about.
If you do want to add something to give yourself piece of mind, some dope or thinned polyurethane works great.

I wouldn't waste the time, but if you feel you need to, you can thin 30 minute epoxy with alcohol and paint it on too. Make it thin like water.

Don't bother on most airplanes. I have sprayed clear dope on 1/4 scale Cub airfames if it a dedicated float plane just to keep mildew out. A very light coat inside and out before covering, not really needed.