No matter how careful you are, it's likely that at some point you will have to make repairs to your fiberglass boat. Although fiberglass is a very tough material, it isn't impervious to damages, which can occur from sharp rocks or other objects hidden under the surface of the water. Repairs can be done by a professional, or you can carry them out yourself by following the steps below.
Step 1 - Clear Damaged Area
Locate the area of the hull that has been damaged. Ideally, you want to be able to access it from both inside and outside the boat, so it may be necessary to clear the area of any equipment to give yourself space to work. Wear the dust mask at all times when you are cutting or sanding the fiberglass, as breathing in the particles can be hazardous to your health.
Step 2 - Tidy Edges
In order for the new fiberglass to bond correctly, the damaged area on the hull must have clean, smooth edges rather than a ragged scrape. Cut around the damaged area until you have a smooth-edged hole to work with. After cutting, use a dry cloth to clear away any debris and clean the edges of the hole thoroughly with soap and water. Don't use bleach or any strong chemical cleaners, as they will prevent the fiberglass epoxy from bonding properly and may lead to a leak.
Step 3 - Cut Fiberglass Patches
While you wait for the damaged area to be totally dry, you can cut the fiberglass sheet sections that you will use to cover the hole. Measure the hole in the hull then use the jigsaw to cut two identically sized pieces that will overlap the damaged area by between two to three inches on all sides.
Step 4 - Apply Backing Section
From inside the boat, use the steel wool to roughen the fiberglass around the hole you have made. The texture aids in the bonding process. Attach the panel that you have cut to the hull using the epoxy.
Step 5 - Apply Front Section
Roughen the exterior of the surface with the steel wool and apply the front section of fiberglass using more epoxy. Smooth the material out carefully to minimize any bumps and blend the repair smoothly with the rest of the hull. Leave the epoxy until the whole area is completely dry.
Step 6 - Sand and Refinish
Use the sander and 400 grit paper to remove any bumps or imperfections from both sides of your repair. Sanding also helps to blend the fiberglass patch in with the surrounding area, which is especially important if you use a clear finish rather than paint. You may find it beneficial to add a thin layer of polyester-based body filler if you want to re-create the shape of the hull perfectly. This can be rubbed down to a P400 grit finish.
When you are finished, clean the area with a dry cloth, and you can complete the procedure by painting or spraying the hull in the appropriate color.