How to apply fiberglass repair to a metal car fender

Written by jay kurz
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Fibreglass is a versatile material that is used for many different applications. Among the uses is for reinforcement or for repairs on materials such as wood, styrofoam and metal. Fibreglass is applied in layers of dry fibreglass mat that is saturated with a resin mixture. Fibreglass is commonly used for fender or other bodywork on cars. The fibreglass is easy to work with, and it will restore the metal back to its original surface. You can find fibreglass repair materials for cars at auto parts stores.

Skill level:

Things you need

  • Safety glasses
  • Air grinder
  • Rags
  • Acetone
  • Fibreglass mat
  • Razor knife
  • Fibreglass resin
  • Catalyst
  • Small bucket
  • Stir stick
  • Felt roller
  • Air roller
  • Respirator
  • Palm sander
  • 200 grit sandpaper

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  1. 1

    Put on safety glasses and grind the damaged metal using an air grinder. Grind any broken or jagged metal smooth and thoroughly scuff the entire area around the damage.

  2. 2

    Clean the grinded area with a clean rag and acetone to remove any dust or grease residue.

  3. 3

    Cut the first layer of fibreglass mat using a razor knife to fit directly over the damage. Cut each layer of mat that follows 1/4-inch bigger than the last. This will allow the edges of the repair to gradually taper instead of forming a ledge. Cut as many layers as it takes to restore the thickness of the damaged metal.

  4. 4

    Mix the fibreglass resin with the catalyst in a small bucket, following the recommendations on the containers. Use a stir stick to thoroughly mix the fibreglass.

  5. 5

    Wet the surface of the damage with the resin mixture, using a felt roller. Apply the smallest layer of mat to the surface and saturate it with resin. Remove any air bubbles that are trapped under the mat using an air roller. Apply the remaining layers of mat, following the same process for each layer. Let the fibreglass harden.

  6. 6

    Put on a respirator and sand the fibreglass repair using a palm sander with 200 grit sandpaper. Sand the repair until it's level with the surrounding metal and the edges are no longer visible.

Tips and warnings

  • Always wear a respirator when grinding or cutting fibreglass.

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