There are a number of ways to fix a blister. Many people apply an epoxy coating; we don’t do this because it’s expensive and requires using a different bottom-paint system. We make our repairs by first filling all the large voids with polyester resin and fiberglass mat and the smaller voids with vinylester filler.
For big blisters especially, preparation can pay big dividends. We have spent a day cutting disks of fiberglass mat in diameters that run from to 3 inches. When we are finished, we arrange the fiberglass disks in neat piles. Before applying our patches we first clean out the blister with acetone to remove any remaining surface moisture. Next, we fill the blister hole with the fiberglass disks that have been thoroughly wetted-out with polyester resin; the smallest circle goes in first, with the diameters increasing as the void is filled. We use a roller after applying each layer to make sure all the air bubbles have been pressed out from the glass and resin.
Once the resin has hardened, we use a rotary sander with an 80-grit disk to take care of any high spots. That leaves us with a pock-marked, but much healthier hull. If there are any depressions in the hull surface around a blister, we fill the pocket with vinylester filler. When it’s cured, we use an orbital sander and a 120-grit disk to fair the surface. We might go over the hull several times with the sander until the surface is smooth.
Before applying the new bottom paint, we carefully prime all the bare and repaired spots. When the bottom paint has been applied according the manufacturer’s instructions, we know the boat is ready to go back in the water, and we are ready to go sailing.
After sailing up the East Coast as far as Virginia, where they hauled out last fall, Rosie Burr and Simeon Hoggarth returned to the Caribbean for another year of cruising.