Hi, I’m a first time builder, sander, and painter. I’m working on a Tenderly Dinghy. I have a question about sanding my hull before painting.
(My current paint plan: marine primer (unless there are reasons this would be bad), anti-fouling paint below the waterline, and then light-colored marine topcoat above the waterline. I want her to look good not sloppy, but I don’t need it to look professional-level.)
Question: If I’m painting the hull, how important is it to have the same level of sanding perfection that is needed for good brightwork? Especially if I’m planning primer? Of course I do plan on re-epoxying any areas sanded-through to weave or raw wood, and re-sanding those areas, since doing this makes the boat more durable. The question: is it necessary to eradicate those small glossy pits, that seem to pop up everywhere?
These tiny pits seem more cosmetic, and I’d imagine that the primer would smooth those out well enough. Plus, trying to sand smooth those tiny pits is increasing my sand-throughs to fiberglass or raw wood… creating additional work that I’d like to avoid. Thanks.
Primer helped me suss out areas that needed attention that were sort of hidden before the primer. I’ve never fooled with anti-fouling paint, I would follow the directions on the can as closely as possible. I’ve heard some anti-fouling paints don’t like primer.
Primer is to fill in pinholes and to make the paint bond better to the epoxy. Epoxy-compatible paints don’t need a primer.
For the best paint job you want to use fairing compound. You can make your own from epoxy and phenolic microballoons or buy a pre-mixed compound. I prefer making my own because I can control the proportions as required by different parts of the boat. For example, a slightly thinner compound for the bottom of the boat so it’ll cure harder, a thicker compound for the sides so they won’t sag, etc. In any case, once the fairing compound cures, sand it with a manual fairing board for the best results. You’ll probably sand off most of the compound and leave only what is needed to fill in the valleys to match the hills. If you sand to #220 grit you’ll also be taking care of the pinholes and can skip the primer.
Finally, anti-fouling bottom paint. You only need it if you will be keeping the boat in the water for weeks at a time. For a Tenderly I’d recommend non-ablative paint because the boat is slow compared to motor boats and the paint (and growth) won’t be pulled off by the motion of the water. Since you’re going to have to scrub/pressure wash anyway, might as well use the more environmentally friendly paint.
Alternatively, pull the boat out once a week and scrub it and don’t worry about anti-fouling paint. Coat the bottom with McLube Hullkote and you expand that to 4 weeks (at least in Maryland waters).
Laszlo