Ask SAIL: Repainting Fiberglass

 I have a 1972 Cal 2-29. The interior fiberglass was evidently painted at the factory. Now, however, large pieces of paint are peeling off everywhere. I have found a solution for removing the old paint by first scraping and then using a combination of peel-and-strip paper with some orange citrus Home Depot paint remover.
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REPAINTING FIBERGLASS

Q: I have a 1972 Cal 2-29. The interior fiberglass was evidently painted at the factory. Now, however, large pieces of paint are peeling off everywhere. I have found a solution for removing the old paint by first scraping and then using a combination of peel-and-strip paper with some orange citrus Home Depot paint remover. To repaint the inside of the hatches I’m using some white-pigmented epoxy. However, for the main portion of the interior, I’m uncertain as to how to proceed. What would you recommend for cleaning the interior fiberglass? What would you use for a primer? What would you recommend for a top coat? I was considering some white bilge coat paint with a little Cab-o-Sil for texture. Whatever I use, I don’t want anyone in the future to have to deal with this kind of situation.

Russ Hammond, La Jolla, CA

DON CASEY REPLIES

Molded features were gelcoat finished in 1972, so if you have smooth interior surfaces that are peeling, a previous owner painted them. Cal may well have painted exposed interior surfaces of the hull and deck, so I am going to assume you are asking about painting the textured backside of molded fiberglass.

Don Casey has written many books and articles on marine maintenance and repairs

Don Casey has written many books and articles on marine maintenance and repairs

Always be circumspect about using conventional strippers on fiberglass, as most will dissolve polyester resin. Where you have already done the stripping, make sure you have removed all traces of the chemical stripper. Paint peeling in sheets typically signals poor surface preparation, and in the case of fiberglass, the contaminant is wax. Polyester resin will not cure in air, so the exposed surface is coated with wax at the time of layup. This wax does not go away with time, so it is essential to remove all traces for paint to adhere. If this paint really was applied 42 years ago, surface prep was stellar, but you should not make that assumption.

Preparation essentials are to wash the bare fiberglass with a TSP solution and use a brush to remove dirt and oils, followed by a vigorous scrubbing with xylene or acetone (safer in enclosed spaces) to de-wax the surface. A soft wire wheel in a drill motor is the better tool for giving the clean surface tooth prior to painting, followed by a final solvent wipe to pick up dust.

For rough interior surfaces I tend to apply a good grade of alkyd enamel—usually a low-luster exterior house paint. On an uneven surface, this type of paint looks as good and lasts as long as anything and has the additional advantages of being relatively inexpensive, self-priming and available in any color imaginable. This paint is equally suitable for smooth interior surfaces unless you are looking for a mirror finish. On smooth fiberglass, I usually apply an epoxy primer first to improve adhesion.

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