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There are several areas on the boat that are covered with epoxy-only, no fiberglass cloth; e.g., rub rails, transom, and a few other very small areas. For some reason, even though I have re-coated with three or four layers of epoxy, I keep sanding through to bare wood. It's starting to drive me nuts. I re-coat the sanded-through areas with several coats, wait several days for the epoxy to cure, sand again (hand-sand only, very carefully) and inevitably in trying to get it smooth I end up sanding through some spots again! And the vicious cycle is repeated.

I finally decided that, if I am ever to get this boat on the water, I'm just going to have to let it go with the hope that paint or varnish will seal these small areas well enough. Thankfully, none of these sand-throughs are in places where water collects, but rather, it runs off right away (and there are no sanded-through areas below the water line). I'm not that concerned about wood rot in these areas. For example, I know that bare wood fences only lose about 1/4" per 100 years to wood rot as long as the water can run off quickly. My concern is that, because paint and varnish are somewhat porous, the wood can become slightly damp underneath, causing it to expand and contract, with the result that the paint cracks and has to be repaired every year or two. It takes more skill than I have to feather these areas sufficiently that they blend in completely. Again, if the water can run off right away this may not be a problem.

So as I said I'm not going to worry about it and go ahead with finishing the boat. Surely I am not the only one who has had this problem. If anyone cares to admit this happening to them , how did you handle it? Leave the epoxy repair slightly rough? Paint over the bare wood, as I did? Some other ingenious plan?

Don't do it! I made that mistake on my rub rails and every place that I didn't have covered with epoxy within 4 months the clear coat paint started to peel. Varnish on the spars too. Part of it may be the intensity of the florida sun but after I sanded and reapplied epoxy and paint they've held up ok.

I would for sure take care of it now because it's a much more work later. That has definitely been my experience. You can see what happened to my rub rails here: http://1.bp.blogspot.com/-XUsv2lLnIkk/VMas37Ng5eI/AAAAAAAAD-k/pF2TF_TEHYE/s1600/IMG_0935.jpg

I don't have a lot of experience with this, but I have noticed some things on my boat this year. Varnished wood that is left in the elements (sunlight, water even if it dries afterwards, etc) will peel away from the wood. Take a look at John's "What happens to epoxy boats when they get old" article on the CLC website to see this on the bowsprit of Pocketship #1 where the epoxy was sanded through during construction. Over time, water apparently gets through the varnish and causes it to "lift" off of the surface. I actually am dealing with this now with my own bowsprit. I had apparently sanded through the epoxy along the sharp edges of the chamfered bits, and they all turned dark where the varnish was lifting off.

Solution? I sanded down the entire spar to wood and re-epoxied everything. I think they key is to not sand so much. I was under the impression that the epoxy needed to be completely 100% smooth and grey. I don't think that's exactly true. I made sure it was all scuffed up so the varnish would adhere, but I really didn't sand very much. I can't tell any difference in smoothness or varnish appearance from "before" to "after", "super-sanding" to "carefully sanding". If you are over-sanding, try to do this light sanding method to see if it helps.

EDIT: Agree with Bill above. I started writing mine before his was posted.

Hey Guys:

I'm not as far along as you all; just glassing the hull interior now. But I recently called CLC to discuss epoxy/fiberglass/sanding to get some tips. The tech rep told me that one of the things he didn't like about MAS epoxy was that it cured a little 'lumpy'. He suggested blowing some warm air over the freshly laid epoxy with a hair dryer. This has the effect of flattening the epoxy and thus needing less sanding; reducing the chance of sanding thru to the bare wood. He felt strongly that, in any event, hardened epoxy should NOT be sanded to the point of having the entire surface turn a grayish color.

Leaned a lot from you guys; thanks.
Jimmy V
Victory II

Dang, I wish I'd asked about this before! I have always tried to get the epoxy to a uniform gray. That's the way Russell Brown says to do it in "Epoxy Basics," but he is talking about West System, not MAS. Well it is too late to do anything about the painted surfaces--we'll just have to see how they hold up. I have not varnished the bright-finish areas yet, so I will re-epoxy the bare spots, not try to get it quite so smooth, and try the hair-dryer method.

I'd rather put up with it being a little rough here and there than the alternative. This boat is not supposed to be a show piece, although I do want it to look as good as possible. The main thing I want to do, though, is use it! I'm hoping the painted areas will hold up a little better, and as I said there are very few sanded-through spots and they are all on areas where the water runs off immediately. All this has helped me make one decision I had been pondering. I'll definitely make the tabernacle removable so I can garage the boat over the winter.

BTW, I also built a Skerry and on it the rudder, rub rail, mast and spars are not epoxied, just varnished. I have had absolutely no problem with them. They get wet a lot when sailing, but they are not left out in the weather.

I am struggling with this same problem. I am working on the cabin roof. I tried very hard to get a smooth third coat of epoxy and it wasn’t too bad. But as I sand, I get down to small depressions and getting those sanded out will probably take me into the glass nearby (see picture). I have thought about a heat gun to level the epoxy after applying it; has anyone tried that ? I can see how it could work on a flat surface but worry it will run on the curved cabin.

So are some depressions ok? My experience is that any imperfections will Telegraph through the paint. What have you all done? I’m thinking of adding some epoxy to the low areas and re-sanding, ugh.

One option is to fill these holes with thickened epoxy and smooth out with a putty knife. Putty. Then sand that area flat. Before pouring, you still need to scratch the shiny surface a little to improve adhesion.

Yeah, that’s what I’ve been doing where I had air pockets in another area where I sanded the lifted fiberglass out and filled with thickened epoxy. I guess it’s not a lot of effort to ensure a smoother finish. This will not be a show boat, but I do want it to look decent. Just takes another day….

I'd recommend thickening the epoxy somewhat with microballons or anther easy sanding fairing filler. You can build up thickness and get the shape close with a putty knife of squeegee, and sand it down perfect with a fairing board. Compared to raw epoxy or epoxy thickened wood flour, that stuff is a dream to sand.

WEST's Microlight 410 is my current light weight, samdable filler of choice for this kind of non-structural epoxy work. https://www.fisheriessupply.com/west-sy ... ght-filler