Just spent the afternoon sanding! SeTherin has had an area of persistent blisters about four feet long and two feet wide outboard of the keel on the starboard turn of the bilge for twenty some years.
The years we had her in Pensacola (80 thru mid-85); she was in the water all year. In those five years, I had her out of the water two times for bottom paint and one another for polishing the paint for a smoother bottom after we started racing. Not knowing s**t from shineola about boats (and certainly nothing about osmotic blistering & barrier coats), I had the bottom work done by a couple local fellows at Brown's Shipyard. Other than the long periods in the water, I believe the ordeal may have begun with gelcoat damage during one or the other bottom jobs.
I first attacked the problem here in Connecticut over the summer of 1986, read up on the subject, then stripped her down to the gelcoat, and kept her out of the water all season working on the bottom. At that time there were blisters evenly distributed over the entire bottom. I used West System Fillers & epoxy, finished up by first sealing the bottom with West Epoxy, then with Interlux Interprotect. Over the next few years I believed the problem was rectified, yet there was a persistent problem with flaking of the bottom paint on the starboard side over the offseason; the side that sat in the shade over winter.
Over the winter of '03/04 I flipped her upside down, faired the bottom, coated with Interprotect 2000 and finished with Baltoplate. Later in the season I noticed numerous tiny BB sized blisters along the starboard turn of the bilge. Every spring since, I wasted a good bit of time repairing blisters to no avail.
Well, enough is enough! Three weeks of so ago, I dremeled out well over 100 blisters. A week ago in a spell of unusually warm weather I stripped the Baltoplate off. This time I used Franmar Soy-Strip which I was very pleased with compared with the previously used Peel-Away.
The problem area has now been sanded down to the fiberglass. I intend to let it dry out till April when I begin filling the blisters and so on.
Baltolate Removed 01-09-08
Boatyard 01-18-08
Blisters - down to the fiberglass 01-18-08