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I’ve got what looks like fine cracks on a small portion on the foredeck of my boat, right near one of the bow rail stanchions. What is this, and how can I get it repaired? H.K., via e-mail
It sounds like you have stress cracks, the specific cause of which could be any one of a number of things. Generally, stress cracks occur because the gelcoat becomes brittle and flexes differently than the substrate. Some gelcoat stress cracks are normal, especially in older boats, and usually are not structural in nature. You needn’t worry about them unless they’re wide enough for you to fit your fingernail into or unless they go deep enough that they allow water into the underlying laminates.

If the cracks are structural or if you just can’t stand the sight of them, WEST SYSTEM® has a fiberglass-repair manual that explains how to deal with the problem. The area must be first ground down, then filled with an epoxy filler, then sanded with ever-finer grits of sandpaper. Finally it is regelcoated. If the cracks are in your nonskid, the repair is trickier. Regardless of where it is, note that’s it’s always difficult to match new gelcoat color exactly to the original, particularly on older boats that have faded. I recommend calling in a professional.

Here’s what to expect. The area will be ground out, then wiped with an appropriate solvent (one recommended by the manufacturer of the paint system being used). It will now have a shallow crater-like look that will be more evident to the touch than to the eye. The contractor will use epoxy resin and cloth to build the area back up. He’ll cut the cloth into circles that get bigger as the repair advances from the center of the crater. Each layer will be wetted out with resin, and once each of these layers cures, he will do some minor filling and fairing. Once the entire area is evenly covered and the final layer is cured, filled, and faired, he will prime and paint the area.

If your foredeck is gelcoated, color matching can be done by using polyester or vinylester resins and fillers instead of epoxy, due to the fact that gelcoat doesn’t cure properly over epoxy. If the deck is painted, you can use the epoxy for the repair and then repaint, since epoxies are stronger and will usually last longer than polyester or vinylester.

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