Don't sand thru the gelcoat if you don't have to, Chuck. Fiberglass isn't
waterproof without it. Patch the ground out blisters with Marine Tex or
other waterproofing filler.
JIMinFL
wrote in message
ups.com...


I had a batch of chine blisters that I dealt with two or three bottom
paint jobs ago. Just sanded them flat, let them dry for a few hours,
faired them out, and slapped on the bottom paint. Cost was less than
$100. I fully expect to see those same blisters back again some day
(but maybe not)........and if I do I'll spend another $100 to deal with
them. That's much better than spending $10,000 or $20,000 or maybe more
to deal with them and *still* having them reappear in the future.

I'll never do this cuz I have waaaaaaay too many other weird projects.
It came out of a scheme of mine to measure the fluid level in oil wells
using microwaves.
I have done a lot of looking into blister repair and even have done
some of it. What I find is that blister repair is mostly a scam that
fails about 80% of the time. As others have pointed out, blisters are
really only a cosmetic problem. I have NEVER heard of osmotic blisters
causing hull failure on a boat made from woven fiberglass. I HAVE
heard of severe problems in hulls made from short strand mats. If
anybody has ever heard of a hull failure or accident resulting from
Osmotic Blisters, i'd like to hear about it.

Thanks

David

JIMinFL wrote:
Don't sand thru the gelcoat if you don't have to, Chuck. Fiberglass isn't
waterproof without it. Patch the ground out blisters with Marine Tex or
other waterproofing filler.
JIMinFL

I don't know how you would fix a blister without removing the deformed
gelcoat.

Gelcoat ( essentially a layer of tinted resin) is somewhat porous. You
may be thinking of a barrier coat, not the gelcoat. When the term
"osmotic blister" is applied, the osmosis is the passage of water
through the gelcoat, not through the laminate. Plastic doesn't absorb
water, so if there are no voids in an FRP hull it isn't ever going to
become "waterlogged".

When I refer to "fairing", that's the same process you describe above
with the filler.

Happy New Year