Hey guys I have a question it maybe stupid but here goes. I wish to paint my uncovered plane and was thinking of glassing it but I have never done this before. Is it possible to just paint on clear polyurethane, a couple thin coats then spray prime then sand smooth spray prime again sand smooth mask it off and paint without using the fiberglass ? Thanks for any ideas.

In THEORY, yes it is possible. In the real world, if you want the paint job to last, you need to paint on a stable surface.

Wood is not stable. Due to changes in the humidity and temperature the wood is going to expand and contract. After a period of time (typically about 12 - 18 months ) the paint begins to crack.

For a stable surface you either need to glass the plane or cover it with a stable surface such as silkspan or, depending on the plane, a fabric and apply the paint to that.

I have a friend that is an old time pilot from the UK and he covers his airplanes with brown paper using thinned yellow or whie glue. He paints all his airplanes and averages 1 or 2 designs written up in British R/C magzines. He has never had a problem with the paint job not lasting using this process.

Well, I'll have to disagree. I have a very old plane (Over 13 yrs) that I painted with thinned epoxy, sanded and then sprayed with white 21st Century paint from Black Baron.

The plane is beat to all heck, and a fair amount of wood grain shows through, but the paint never showed signs of cracking

I had a glider fuselage, Midwest 2x2 given by a friend. He and his brother painted the fuselage, but applied sanding sealer to it first to fill up the grain. The paint finish was very smooth and no cracks.

Jim