When someone drops a winch handle, spinnaker pole or outboard shaft on a fiberglass deck, it will sometimes produce a minor ding in the gelcoat and fiberglass. Fortunately, most of these dings are relatively easy to fix. Here’s how.
Hole in one
To repair a minor ding or hairline crack, first use a Dremel tool to smooth the gelcoat surfaces down to the fiberglass. Remove any loose gelcoat or antiskid material, then use acetone and a clean rag to clean the area and remove any mold-release wax that may still be on the surface.
Next, mix a batch of epoxy and add a small amount of colloidal silica and fairing compound until it has the consistency of peanut butter. Use this epoxy paste to fill the damaged area and when the epoxy has cured, sand the area smooth.
Deeper holes need more than just filler, because over time the filler will crack and fall out. Use a combination of 1/2 oz. fiberglass mat and 6 oz. cloth to make these bigger repairs. First measure the depth of the hole, then draw a circle around its center with a radius eight times the depth. Use a Dremel tool to evenly feather the depression up to the outer edge of the circle.
Next cut out a circle of mat and a circle of cloth. Give these circles the same radius as the circle you have drawn on the deck. Continue cutting mat and fiberglass circles making the diameters of the succeeding circles 1/2 inch smaller than the previous pair. Keep cutting circles until you have enough material to fill the hole. Then cut one more circle from the glass cloth with the same radius as the first. Use a straightedge to determine when all the mat and cloth layers are flush with the surrounding deck surface.