Preserve your fiberglass hull


By Bill Isenberg

For below-the-waterline maintenance, epoxy barrier coating is one of the best measures you can take to preserve a fiberglass hull. It prevents water from migrating into the fiberglass, thus adding weight to the boat and causing possible delamination or osmosis of the fiberglass.

A boat that remains in the water all summer can absorb many pounds of moisture. A properly applied epoxy barrier coat can prevent this, raise the waterline and increase the vessel’s top-end speed. Useful on both old and new boats, epoxy barrier coats prevent blisters in the fiberglass.

Applying epoxy barrier coats requires that the hull be blasted with sand, soda or media to remove any antifouling paint already applied. To prevent damage to the thin gelcoat and fiberglass, this extensive procedure requires a professional firm specializing in media blasting boats. A professional can remove the antifouling paint but not the gelcoat, which protects the fiberglass.

Once the antifouling paint has been removed, examine the hull for blisters, which can be repaired with a good quality epoxy such as West System. Next, dry the hull for two to three months so moisture doesn’t become trapped in the fiberglass and cause blisters to reappear. Check the hull below the waterline with a good quality moisture meter. I borrowed one from the marina. You may want to hire a marine surveyor to inspect the hull if there is extensive damage.

After the hull is dried, you can apply a good epoxy barrier coat such as Interlux Interprotect 2000 E. It’s critical to follow the manufacturer’s instructions on the can as well as any technical bulletins supplied. Check the manufacturers’ website for this and other information.

Key to a successful project, preparing the bare fiberglass involves sanding, cleaning and use of solvents. Again, follow the manufacturer’s step-by-step instructions. For sufficient hull protection, apply at least four or five epoxy barrier coats.

When applying the barrier coats, the manufacturer strongly recommends using personal protection including cartridge respirators, goggles, gloves and overalls. Epoxy barrier coats contain hazardous chemicals and should be used with adequate ventilation, preferably outdoors. I learned this the hard way with our previous boat. When applying the barrier coat, I was overcome by the fumes and taken by ambulance to Grand Haven Hospital Emergency Room. Next time I will use a good respirator and apply the coating outdoors. Lastly you can apply antifouling paint over the barrier coat.

United States Power Squadrons, America's Boating Club logo

The Ensign magazine is an official channel of United States Power Squadrons, America’s Boating Club, a volunteer organization whose members teach boating skills and best practices to help improve the safety of our nation’s waterways. Learn more.