gelcoat blisters

[Mark]

I am looking at a daysailer to purchase that has many blisters in the gelcoat below the waterline. There are no cracks. Is this a common problem? How bad does it get? Does anything need to be done or can it be bottom painted (never had bottom paint -- fresh water only).

[Roger]

That typically spells trouble. Blisters are typically a result of water ingress into poorly saturated (with epoxy) chopped strand mat (CSM). Osmosis causes expansion causing delamination, causing the telltale blisters. The fact that there are a lot of them does not bode well. This is usually poorly wetted out CSM during the manufacture, which means that even if you do repair these many blisters, the next season may show a new crop of them.

Repair involves grinding out the MANY blisters down to good fiberglass, then filling, and regelcoating each little crater that you created. Also a full gelcoat stripping can be done, (both labor intensive and expensive) then regelcoated.

This might be a boat you want to walk away from, unless you can get it for next to nothing, put nothing into it, and sail it as is for what its worth... or strip it of its harware and part it out, but it sounds like you want to sail it.

I'm sure this is not the news you want to hear, but better to know now than after you have thrown good money after bad.

[Felix Graham-Jones]

I disagree with Roger. Gel coat blisters are, as he says, the result of poorly wetted out fiberglass osmotically drawing in water and creating the little pimples you describe. In my boat's case, however, it was not that tough a job to open up all the blisters, fill them and fair them out and then rebuild a barrier coat that effectively resists any new infiltration of water. I had intended anyway to fair out several fair sized gouges the boat had acquired over the years so the slightly more extensive project didn't end up costing me a great deal more time. Another factor that may well have contributed to the positive outcome is that I've trailer-sailed the four seasons since doing the barrier coat, so the boat doesnt sit in the water for longer than four weeks at a time. I'm also now really careful to dry the boat out thoroughly, especially the bilges, before setting her away for the winter - the way the blisters were laid out in my hull and cockpit makes me think that being waterlogged and going through several freeze thaw cycles whilst being abused by a previous owner may well have been the real cause rather than poor original construction practices - just my theory.

[Mark]

Thanks for the responses. It has been a fresh water boat and my plan is to set it on a salt water mooring for the summer. I know this is a difficult question your having not seen the boat, but if there is substantial blistering, if I went ahead and bought it would you recommend that I have the bottom re-done professionally or I simply bottom paint and sail? I am not concerned about the cosmetics -- really the structural integrity.

[algonquin]

It is not uncommon to have these blisters and they are repairable. As Felix mentioned it is within the capability of a do it yourself person. A nice weekend, an orbit sander, a couple types of picks and pokes, some filler, assorted sandpaper, two quarts of "Rustoleum" paint, and the associated brushes and stuff and you could make your DS ship shape again.

If you do it yourself (maybe with a couple buddies added in for good measure) you would be into it for about $75-$125 not including the sander, snacks, and refreshments. That would make it a viable project at minimum investment.

The other alternative you addressed is to have it bottom painted and sail it. If the blisters aren't very large, say under a dime size, and they aren't open or soft to the poke of a pick you could most likely go through the next season with some fresh bottom paint.

If you have a shop do it you may be into the money to the point where you exceed the intended value of the boat. Then you would have to reassess the situation.

At any rate, good luck and let us know how it turns out. Brad