How to Patch a Hole in Fiberglass

Fiberglass is a lightweight material that is durable and strong. It is used for many different things, some of which include boats, cars, planes, tanks, bathtubs and industrial pipes. A very good quality of fiberglass is that most all cracks, fractures, and holes can be repaired back to original strength. Fiberglass also is fairly easy to work with and can be repaired without the need for a professional.

Things You'll Need

• Respirator
• Air compressor
• Air hose
• Dye grinder
• Coarse grit sandpaper
• Aluminum tape
• Scrap board
• Rags
• Acetone
• Razor knife
• Fiberglass matting
• Polyester resin
• Methyl ethyl ketone peroxide (hardener)
• Small bucket
• Stir stick
• Felt roller
• Air roller

Instructions

1. Plug the air compressor into an electrical outlet, and allow it to build air pressure. Attach the air hose to the compressor. Attach your grinder to the end of the air hose.

2. Wearing a respirator, grind the walls of the hole using a dye grinder. Taper the walls of the hole so that a 1/2-inch of each layer of fiberglass is showing. The more gradual the taper the better the bond will be. Scuff an area that is at least 6 inches in diameter larger than the actual repair.

3. Secure a flat piece of wood behind the hole for a backing. Cover the hole with aluminum tape. Cut the edges of the tape with a razor knife and sand smooth.

4. Clean the repair area with a rag and acetone. Remove any dust or grease that remains on the surface. Any grease or dust left on the surface can affect the bond of the fiberglass.

5. Cut the fiberglass matting for the repair. Start with a piece that is the same size as the hole. Make each following layer 1/4-inch in diameter larger than the last. Continue to add layers until the last layer covers up to the top of the tapered edges and is as thick as the wall of the repair.

6. Mix the resin with the hardener as directed on the containers. Use a small bucket and a stir stick to mix the resin. Stir thoroughly until the mixture is one color. Wet out the surface of the repair and place the smallest layer of mat in the center of the hole. Saturate with resin using your felt roller. Roll the air out of the mat using your air roller. Continue this process until the repair is as thick as the surrounding fiberglass. Let cure until it is hard and cool to the touch.

7. Sand the surface of the repair until it is smooth. Remove the board and sand the back of the repair smooth.

Tips & Warnings

• Always wear a respirator when working with fiberglass.

References

• Fiberglass Site