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