Repairing fiberglass isn’t as difficult as it sounds. That hole in the hull is quickly healed as well as any boat repair professional would, with glass fabric, resin, and equal parts skill and care. Fiberglass lay up is nothing more than layers of glass fabric saturated with polyester or epoxy resin, yet most boat owners can’t imagine doing the repair themselves. Follow the directions and your repair will be as durable as the rest of the boat.
Pull the boat out of the water and allow it to dry. Tap around the damage with a screwdriver handle to determine its extent. Solid areas make a sharp sound, while damaged areas sound dull.
1. Cut away damaged fiberglass in a circular hole, preserving the hull’s strength.
• Wash the hull around the hole with a de-waxing solvent to ensure a clean working surface. From here on, you’ll be working on the inside of the boat unless noted.
• Grind an area a few inches all around the hole to build up a fiberglass patch without creating a lump.
• Brush away dust and wash the area with acetone.
• Apply paste wax to the outer hull around the hole to prevent any resin from sticking.
• Cut stiff plastic sheet a foot larger than the hole to form a backing. Wax and tape it over the hole on the outer hull. This will make it much easier to obtain a smooth finish.
2. Repairing the Hole
• Cut several layers of fiberglass mat and cloth ½” larger than the hole. The number will depend on the thickness of the hull, but generally you’ll want one layer for every 1/32”.
• Mix gelcoat and catalyst in a bucket, following the instructions for what you’re using. Above the waterline, use polyester resin. Below the waterline, use epoxy and skip the gelcoat steps.
• From the inside of the boat, brush a layer of catalyzed gelcoat 1/32” thick on the surface of the plastic sheet. This provides a smooth outer surface. Allow the gelcoat to cure until it’s dry.
• Mix resin and catalyst in another bucket, then brush a coat of catalyzed resin onto the gelcoat.
• Apply fiberglass mat into the resin. Mat provides a smoother surface for the first few outer layers.
• Tap more resin into the fiberglass to saturate it. Tapping resin instead of brushing it eliminates trapped air bubbles that weakens fiberglass.
• Add another layer of mat and resin, then alternate between cloth and mat until you’ve filled the hole.
• Finish with two layers of mat cut slightly larger to ensure a good blend. Use a resin roller or squeegee to get the patch smooth.
• Allow the fiberglass to cure fully.
3. Sand the inner surface smooth.
• Remove the plastic sheet from the hull and fill any imperfections with fresh gelcoat.
• Allow the new gelcoat to cure, and then sand the entire area smooth.
• Paint, wax and polish as needed.