My 1982 Pearson had blisters last fall at haulout. The yard suggested 'sand washing'. After much research and even more scotch, I had them do it - (it looks like it was sand blasted to me).
The blisters are now small holes through which i can see the fiberglass underneath. I presume that much of the gelcoat is gone too.
I was going to gently grind the blister holes and epoxy them, then apply a few coats of 2000/2001 or similar barrier coat follwed by bottom paint.
But an article from http://www.dockwalk.com/issues/2003/...listers2.shtml
suggests alkyd-urethane-silicon blend, or a two-part marine polyurethane paint works as well, or better, than barrier coat.
The barrier coat, they say, slows but doesn't prevent, water from entering the fiberglass. It will, however, prevent the mix of water and fiberglass resin from exiting resulting in new blisters.
The marine paint, on the other hand, allows water to move into the fiberglass faster than barrier coat but interacts with the resin in the fiberglass to slow resin mixing with water which creates the larger molecule that can't escape and causes the blisters. I'll get blisters sooner but not as badly (I guess).
If I use barrier coat andhave excessive blistering this fall, I'll be starting over. If i use marine paint (maybe Easypoxy by Petit) and get blisters, I'll kick myself for not using barrier coat.
What would you do?