How to Repair Fiberglass
Fiberglass is a notoriously strong material that is used in boats, bathtubs and even garage doors. However, as with any material, it can develop cracks or holes. You will repair the hole from the inside out, so you can create a seamless repair that will match the original.
- Difficulty:
- Moderately Challenging
Instructions
Things You'll Need
- resin roller
- gelcoat
- polyester resin
- fiberglass mat
- methyl ethyl ketone peroxide
- tape
- grinder
- dewaxing solvent
- razor
- fiberglass fabric
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1
Find the damaged piece of fiberglass if it is not clearly visible. This can be done by tapping the fiberglass with a hard tool. Damaged fiberglass has a dull sound, while normal fiberglass sounds tight.
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2
Start the repairs by working from the inside. This will allow you to have a seamless repair on the outside.
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3
Cut away the damaged area and use a grinder to taper the hole. The reason for creating a taper is to give the new laminate more surface area to bond to. This will increase the chance the repair will work.
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4
Treat the exterior border of the hole with a de-waxing solvent. This will help create a strong bond when you apply the new fiberglass.
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5
Coat the area around the hole in paste wax. Paste wax will ensure that any resin that runs will not bond to the undamaged exterior.
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6
Screw or tape a waxed backer to the bottom of the hole. The wax backer will give you a hard surface to work on while you are patching the hole.
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7
To start the repair, you will need to coat the waxed backer in a gelcoat. Gelcoat is pigmented resin, so you will need to match up the colors. This will serve as the smooth exterior finish that will match your undamaged fiberglass.
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8
Cut fiberglass fabric and mat to the size of the hole. Place in two layers of mat, and then fabric. Then alternate layers of fiberglass mat and fabric. The amount of fabric and mat you use is determined entirely by the thickness of the fiberglass, but any more than four layers will weaken your bond.
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9
Use polyester resin or epoxy to patch the hole and secure the fabric and mat. For polyester resin, you will need to use a laminating resin as well. A laminating resin will increase the strength of the bond.
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10
To harden polyester resins, you will need methyl ethyl ketone peroxide as a catalyst. Follow the manufacturer's instructions on how much to use. Using a resin roller, remove any bumps or air bubbles.
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11
Remove the wax backer and fill in any exterior imperfections with more gelcoat. Sand and polish as necessary.
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1
Tips & Warnings
Make sure you taper your hole. Tapering the hole will provide you with adequate surface area to create a strong bond.
Laminating resin however does not cure in the open air. To get it to cure fully, you will need to seal it off from the air using plastic.
For a professional fix, make sure to wax the area around the hole and use a waxed backer. These two things will prevent resin runs hardening on your fiberglass.
Never use more than 4 plies of fiberglass cloth and fabric. Using more than four plies will cause the bond to weaken.
