How to Fix a Fiberglass Fender
Fiberglass is a durable and lightweight material that's easily repaired. One of fiberglass' best characteristics is that a secondary bond, or repair patch, on a fiberglass fender can turn out as strong as the original fiberglass. The damaged fiberglass is replaced with layers of new fiberglass material that's as thick as the surrounding fiberglass. Working with fiberglass can get messy, but it's relatively easy to pick up. Done correctly, the repair will last as long as the rest of the car.
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Things You'll Need
- Die grinder
- Rag
- Acetone
- Fiberglass mat
- Polyester resin
- Small buckets
- Catalyst
- Paint stirrer
- Felt roller
- Air roller
- Fiberglass filler
- Plastic putty knife
- Palm sander
- 200-grit sandpaper
- 400-grit sandpaper
- Plastic
- Spray glue
Instructions
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1
Grind away damaged fiberglass with a die grinder. Once you have all the damaged and frayed fiberglass ground down, gradually taper the edges of the damage as far as possible. This will give the repair a maximum amount of surface area to bond to.
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2
Wipe down the surface of the repair, using a rag damp with acetone. Let the acetone completely dry.
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3
Cover the back of the repair from the inside of the fender if it is a large hole, using thick plastic. Secure the plastic to the back of the repair, using spray glue. This will give the wet fiberglass repair support until it hardens.
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4
Tear pieces of fiberglass mat the same size as the repair, using as many layers as it takes to build the fiberglass back up to its original thickness. Make each layer 1/4 inch larger than the last so the edge of the repair will gradually taper instead of forming a ledge.
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Mix a batch of polyester resin in a small bucket, using 2 percent catalyst and a paint stirrer. Wet the surface of the repair area with the resin, using a 4-inch felt roller. Apply the smallest layer of mat to the center of the damage and saturate it with resin, using the felt roller. Roll out any trapped air bubbles, using an air roller. Continue the process until all the layers of mat are applied to the repair. Let the fiberglass harden for two to three hours.
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6
Sand the repair smooth, using a palm sander and 200-grit sandpaper. Wipe the repair clean, using a rag and acetone.
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7
Mix a batch of fiberglass filler on a scrap piece of cardboard, using 2 percent catalyst. Work the catalyst into the filler so the mix is the consistency of putty. Apply a thin, even layer of filler over the fiberglass patch, using a putty knife. Let the filler harden for a few hours.
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Sand the filler with 200-grit, then 400-grit sandpaper with the palm sander. The repair will be level with the surrounding fiberglass and should be invisible when painted.
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Tips & Warnings
Always wear a respirator and safety gloves when working with fiberglass materials.
