If the epoxy was properly mixed (correct hardener ratio) and cured, and if you're careful to remove the amine blush (soap and water followed by 100 grit sandpaper), gelcoat will stick just fine to it.
Thanks. Once the epoxy hardens, it is likely to be flush with the gel coat, so I guess then the thing to do is sand it down to make room for the gel coat?
Today I went to West marine and they had an epoxy repair pack, or something with a similar name. It came with 4 plastic cups, stiring sticks, a brush, gloves, a syringe, 4 alcohol wipes, some matte, two different thickeners and some packets of resin and hardener, already measured out. This was about $35.00.
I grabbed one, and I also got a set of plastic putty knives for another $9.00. I decided to try on the holes that are on the under side of the cockpit and above the quarter birth. These holes allow water that somehow leaks through the cockpit to drip onto the quarter birth cushion. Since the cushions are only a few weeks old I wanted to fix this soon.
When I got to the boat, I realized that I forgot to get the white coloring agent they sell, but I decided to do the project anyhow, since no one can really see these holes unless they are lying on the bunk.
I carefully cleaned around the holes with soft scrub, then sanded them down. I then used a countersink bit, in reverse, figuring this would give the epoxy something to grab. Its not a 12:1 bevel, but creating that bevel with such small holes didn't seem feasible. Then I cleaned again to remove the dust and any loose material.
What the kit didn't come with were instructions. Fortunately I had just read the West epoxy users guide this morning. I mixed the resin and hardener in one of the plastic cups, for a solid minute until it was consistently clear. I then mixed in some thickener, and kept adding it until it was uniform and the epoxy was like peanut butter.
I used the stirring stick to apply it to the holes and a plastic putty knife to smooth it. I was able to get all the holes done before the pot time was exceeded, probably 15 minutes (it was cool today). This did result in a lot of epoxy smeared around the holes. I was trying to make it thin to minimize the sanding later.
Looking back, I wish I had gone back for the white coloring agent, so I could see how it would look when cured. Also, it occurs to me that I could use painters tape around the holes, to prevent the putty knife from smearing epoxy where I don't want it or need it.
I left after about 4 hours, and it was starting to rain. The epoxy seemed to have hardened, although I know it didn't cure fully by then. I'll go back tomorrow to sand it.
I don't need to gel coat this set of holes, but I might as a test. Last time I gel coated a vertical surface, I didn't thicken the gel coat and had a miserable time. Now I know better.
I am also going to look into the ear plug idea.