How to Repair a Small Hole in a Fiberglass Boat
Fiberglass boats can develop holes from time to time. Small holes are not difficult to patch up on these types of boats, but the process does take quite a bit of of time. Do not rush this process or you will not end up with a waterproof patch and you will have to start over. The fiberglass is actually many layers of fiberglass fabric, which are applied separately to get the result you need.
Check to see how much damage there is to the layers of material beyond the immediate hole. Tap around the hole with the butt end of a screwdriver and listen for a sharp sound. This indicates that it isn't damaged. If it is damaged, it will sound dull. If you are unsure of the sounds, try tapping somewhere that you know isn't damaged and compare the sounds.
Cut out a larger hole to take out all damaged area where the layers have separated. Use a hole saw to cut it.
Rub on a dewaxing solvent around the edge of the hole made with the hole saw on the inside of the boat. Apply the solvent to remove wax film to prepare the surface around the hole for grinding.
Bevel the edges of the hole the inside of the boat with the orbital sander and 36-grit sandpaper. Use a sander to create the bevel around the hole so that the taper extends back at least 12 inches from the edge of the hole.
Wipe around the hole area with an acetone cleaner.
Paste wax around the hole on the outside of the sanded area to keep any product from getting onto parts of the boat that do not need repair.
Place waxed Plexiglas or laminate over the hole on the outside of the boat and tape it in place as a temporary hold.
Work from the inside of the boat and cut two pieces of glass fiber mat one inch larger than the hole: Apply an epoxy resin to one side of the glass fiber mat and put it in place over the hole. Spread epoxy on the other side of the mat and add a second layer of glass fiber mat. Apply more epoxy and then a layer of fabric. Repeat these three layers, making sure that each layer extends out beyond the beveled edge 1/2 inch further than the one before.
Remove the waxed Plexiglass or laminate used to cover the hole on the outside of the boat. Allow at least 24 hours for the epoxy on the inside of the boat to dry and cure.
Things You Will Need
- Hole saw
- Dewaxing solvent
- Acetone cleaner
- Paste wax
- Epoxy or laminating resin
- Fiberglass mat and cloth
- Orbital sander
- 36-grit sandpaper
- Use a laminating resin instead of the epoxy if you are going to apply a gelcoat to match the hull color.
- You can apply the gelcoat first since you are working from outside in. Let the gelcoat start to harden against the laminate taped patch about 30 minutes before starting the layering. Wait for the first three layer pattern to set up and then continue with the next four layers of mat and cloth.
- You must use epoxy for repairs below the water line.