After two coats of primer on top of fiberglassed surfaces, I'm still getting some gaps that appear like grains in wood. I'm sure that more sanding early on would have helped, but at this stage, is there any technique for filling in these fine lines, or gaps, short of sanding down to the fiberglass cloth?

Thanks,
Paul

I may be doing it incorrectly, but I sand all of the coats down to the cloth except the last one or two. The primer will fill the pits and low spots and not build up making your plane heavy. Ron

Hi Ron,

Thanks for the info. I thought I'd have better results after sanding down the first coat, but maybe I need to sand again and hit it with another coat of primer.

Paul

Use the "filler" type primer to fill the weave in the glass.

FBD.

If you don't sand the first couple of primer coats down until you see "spots and lines", you're not actually filling the weave and valleys, you're just thickening the paintjob.

You really should sand until most of the primer is gone. You want to see primer in the weave as spots. You really should see mostly weave with no primer hiding it. It's important to have the first couple of coats of primer being more gone than present after sanding.

All good advice. Thanks guys.

Paul

Well Fellas,

I thought I'd post the fruits of your advice, and my labors. I sanded down to the cloth and can see the spots and lines as mentioned. It's a lot of work, but I'm sure I'll be happy in the end.

Thanks again,
Paul