Patching A Fiberglass Boat Hull

To begin you will need to purchase a polyester resin fiberglass repair kit from your local boat store that works with the manufacturer of the boat. It will need to be quart sized and you have to purchase a gel coat that will match the color of the boat you have. Also purchase a quart of polyester resin and hardener, 2 square feet of 10 ounce roving, a 7 ½ ounce fiberglass cloth, and fiberglass rubbing compound.

What To Do

  • When preparing the boat or canoe for the patch you must actually make the hole in the hull bigger. Grind down the edges of it to help firm up the fiberglass using a disc sander or an electric drill that has a medium grit sanding disc attachment. The hole should be three inches wider then it was and should be surrounded by sound fiberglass. This will help to give the patch a surface that is easy to bond with.
  • Make sure that you wipe off the dust using a soft cloth and use acetone to clean off the area. Be careful when using the acetone because it is extremely flammable. You need to work in an area that is well ventilated and wear any necessary safety goggles, gloves, and overalls.
  • Cut a packing piece using light cardboard that is two inches bigger then the hole and cover it with plastic wrap. Bend the cardboard carefully so that it matches the contours of the hull and use masking tape to secure it to the inside of the hull. Once you have placed the backing on the hole you will use 10 ounce roving to add thickness to the hull. The top layer of this needs to be cut from 7 ½ ounce fiberglass cloth to work with the surface.
  • The first layer of the roving has to match the diameter of the home from the smallest part of it. Any other layer that is cut must overlap the inside and feather out to taper the edges of the hole you are fixing. You need to stack the various layers together as you are cutting them out. Just have enough to make it level with the surface of the hull. You will then need to cut the fiberglass cloth to overlap it all and patch it up.
  • Lay down the roving and fiberglass onto a clean surface that is near the boat and combine the polyester resin and hardener following the necessary directions from the manufacturer. Only apply enough that you can for ½ an hour because it will become hard very fast. Place the smallest roving patch on a piece of cardboard and apply the catalyzed resin with a small paintbrush. It needs to be thoroughly wet. It is now ready to be placed onto the hole in the hull in the bottom of the depression. Use the paintbrush and dap the edges to make it centered. Repeat this process with each layer of roving that you have.
  • Once they are applied you can close the patch using the fiberglass cloth that you cut out. Leave it dry and place it over the hole. Use the paintbrush to work it into the already wet area. You may need to add a bit more resin to the edges. Allow it to dry for eight hours or more.
  • Use a sander to smooth any irregularities in the patch and around it. After this is done clean the area and apply a gel coat to it that matches the boat. Cover it with plastic and allow it to dry for eight hours. Now sand it down one more time to remove any scratches and clean it off. Next you will need to apply the fiberglass rubbing compound and buff the surface of it. Once this is done the only thing you have left to do is to apply a coat of car wax.