How To Repair a Fiberglass Boat

Fiberglass is popular as a boat-building material due to it being lightweight, durable, and weather-resistant. Of course, even the strongest materials can only take so much. Luckily, fixing a hole in a fiberglass boat is fairly easy once you know how. If you do everything correctly, it’ll be hard to tell that there was a hole there to begin with! For a step by step guide on how to patch up your fiberglass boat, check out this article from Thayer’s Marine.

1. Cut the Damage Away

Your first step should be to assess the hull damage by tapping a plastic screwdriver along the laminate. If you tap a particular area and it sounds duller than when you tap the other parts of your vessel, it means that particular patch is delaminated. Remove anything on the inside surface of the boat that might get in the way of the repair process, and then cut away the damaged section in a round shape with a sharp blade. 

2. Repair from Inside

Smaller holes located above your vessel’s waterline can be repaired from the inside rather than the outside. Wash the area around where you made your cut with a dewaxing solvent. This will remove any coatings that might weaken the bond you’ll be making. Next, use a disk sander with 36-grit sandpaper to sand a bevel around the perimeter of the hole. Finally, take a  rag dipped in acetone and wipe away the dust. If you’ve done everything correctly, you should have a dull and smooth surface in which to work. 

3. Apply Wax & Laminate Backer

Your next step will be to coat the area around the hole with paste wax. Be sure to mask the area below the hole so that resin doesn’t run out of the hole and stick to the boat. Cut a piece of smooth laminate or acrylic about a foot larger than the hole to be the backer for the repair. Spray the laminate or acrylic with polyvinyl alcohol mold release and then screw or tape the backer to the outer surface of the hull. If you’re having trouble getting the piece to adhere to a curve, you may need to heat the piece with a heat gun. 

4. Apply Fabric

Spray gelcoat on the waxed backer. Once the gelcoat starts to set, dampen it with a polyester resin and start applying layers of mat and fiberglass fabric. Make each subsequent layer about an inch smaller than the previous one. Use a resin roller every few layers to smooth things out. The number of layers needed will depend upon the thickness of your boat’s fiberglass hull. Once the repair is flush with the inside surface of your boat, you’re done!

5. Finishing

Finally, cut a rectangular piece of mat along with a piece of cloth that’s just slightly bigger and apply them over the patch. Smooth these pieces over with the resin roller and seal them with PVA. Allow the pieces to cure and then remove the waxed backer from the outside. Finally, fill in the gelcoat paste, let it cure and then sand or polish as needed to get a smooth finish.

Shop boats at Thayer’s Marine in Norwich, Connecticut. We also offer boat parts and servicing. We’re proud to serve communities like Springfield, Massachusetts, and we hope to see you soon!