How to Repair Fiberglass with Epoxy

Use epoxy to repair fiberglass

Fiberglass is a strong, durable material; that is why it used for such machinery as cars and boats. The vigor of fiberglass means that if it is damaged, the repair process is challenging yet manageable. Make sure to follow the specific mixing ratios of your manufacturer's resin. Each brand of epoxy will have its own specifications, so try to buy the epoxy that will work well with your fiberglass.

Things You'll Need

• Marker
• Saber saw
• Tape measure
• 50-grit sanding disc
• Grinding disc
• Sand paper
• Plastic
• Soft foam
• Plywood
• Piece of wood
• Biaxial glass material
• Scissors
• Epoxy resin
• Hardeners
• Peel-ply
• Colloidal silica
• Squeegee
• Low-density filler
• White pigment

Instructions

1. Draw an oval shape around the damaged area with a marker. Cut out the shape with a saber saw.

2. Bevel the edge of the hole that you made. Measure how thick your fiberglass is as this will determine how big your bevel will be. The ideal bevel measurement is 12:1, where the bevel is 12 times the thickness of your fiberglass. If your fiberglass thickness is 1/4 of an inch, then your bevel should be 3 inches from the edge of the hole. Make bevel marks around the hole.

3. Sand the bevel using a 50-grit sanding disc on a grinding machine. The bevel should provide a smooth transition from the sharp edge of the hole to the non-beveled areas of the fiberglass.

4. Sand the sharp edge with sand paper.

5. Put a piece of plastic on the back of the damaged area. Place a piece of soft foam, followed by a piece of plywood over the plastic. Prop these three materials up with a piece of wood. This will provide temporary support for the repair.

6. Make a template from the hole and beveled area. Place a piece of plastic over the damaged area and trace the largest part of the bevel with a marker. Lay this template over biaxial glass material and cut out the shape with scissors. Make five more templates, each smaller than previous one, so the final template is the size of just the hole. Cut out glass material from each of these templates.

7. Mix epoxy resin and hardener and paint the entire area. Spread the epoxy onto each piece of glass material, starting with the largest piece and separating every layer with a piece of plastic. Work down in size, so you end with the smallest piece. Place the finished pile on a piece of peel-ply, smallest oval face down and lay the entire patch on another piece of plastic with the peel-ply down.

8. Add colloidal silica to the epoxy mixture until the consistency is that of mayonnaise. Spread this over the damaged area.

9. Apply the patch, with the largest oval shape facing in towards to the surface. Press out excess epoxy and air bubbles with small squeegee. Peel back the plastic on the front.

10. Let the patch cure, or dry, for a day. Remove the temporary backing from the inside. Peel back the peel-ply.

11. Sand the repaired area with sand paper and clean dust with a paper towel.

12. Prepare a batch of resin hardener and spread it over the clean repair area. Add low-density filler to the hardener until it feels like peanut butter and apply this over the hardener. Remove excess epoxy with a squeegee. Let this dry for at least five hours and sand.

13. Add white pigment to some epoxy resin and roll on with a foam roller. Apply a second coat of pigmented resin when the first is tacky. Let this cure overnight before applying your desired finish.

Tips & Warnings

• You can leave the opposite side of the repaired areas open as long as no sunlight will reach it.

• Work in a well ventilated area when working with chemicals.

References

• You Tube: West System Fiberglass Repair Part 1
• You Tube: West System Fiberglass Repair Part 2