How to Repair an FRP Boat
The majority of boats these days are constructed using FRP (fiberglass reinforced plastic). FRP consists of layers of fiberglass material that are individually saturated with catalyzed resin. Overall fiberglass is a very strong and durable material, but it will crack or break when struck hard enough. Repairing an FRP boat is a fairly simple process that involves removing the damaged fiberglass and replacing it with new material. Whether the damage is large or small, the process is the same; and when done correctly, the original strength of the fiberglass will be restored.
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Things You'll Need
- Respirator
- Dye grinder
- Rags
- Acetone
- Mylar plastic
- Razor knife
- Spray glue
- Boat wax
- 1.5 ounce fiberglass mat
- Polyester resin
- Small bucket
- Methyl ethyl ketone peroxide (catalyst)
- Paint stir stick
- 4-inch felt roller
- Air roller
- Palm sander
- 300- and 320-grit sandpaper
- Masking paper and tape
- Gel coat
- Gel coat spray gun
- Electric buffer
Instructions
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Put on a respirator and grind away all the damaged fiberglass using a dye grinder. When you reach solid fiberglass, gradually taper the edges of the hole or groove in order to give the repair patch a maximum amount of surface area on which to bond.
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2
Clean the surface of the repair area with a rag damp soaked in acetone. This will remove all the dust and any contaminants such as grease or oil residue.
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3
Cut a piece of Mylar plastic one foot bigger than the damaged area using a razor knife and glue it on the inside of the damaged area using spray glue. This will give the fiberglass patch support when you are wetting the layers with resin and keep it from sagging in the hole. If the hole is smaller than an inch, you will not need a backing. Cover the surface of the plastic with boat wax so the fiberglass will not bond to it.
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4
Cut as many layers of 1.5 ounce fiberglass mat as it takes to build the damaged area back to its original thickness using a razor knife. Cut the first layer the same size as the hole and make each following layer 1/4 inch bigger than the last.
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5
Fill a small bucket with polyester resin and add 1 to 2 percent catalyst (methyl ethyl ketone peroxide). Thoroughly mix the catalyst into the resin using a paint stirrer.
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Wet the surface of the repair area with the catalyzed resin using a 4-inch felt roller. Apply the first and smallest layer to the center of the damaged area. Saturate the mat with resin using the felt roller. After the entire layer is wet with resin, roll out any trapped air bubbles using an air roller. Repeat this process for each layer until the damaged area is built back up and flush with the surrounding fiberglass. Let the fiberglass harden for at least two hours before sanding.
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Sand the repair patch smooth using 300-grit sandpaper on a palm sander. Tape off the perimeter of the repair with masking paper and tape, leaving only scuffed fiberglass exposed. Mask off at least three to four feet further than the repair to avoid overspray.
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8
Mix a small bucket of gel coat with 1 to 2 percent catalyst and mix it together. Add the catalyzed gel coat to the spray gun and spray the first coat onto the repair in a heavy mist. Let the first coat become tacky then apply a second, heavier coat. Repeat this until you get the desired cover then let the gel coat harden.
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Remove the masking paper and wet sand the tape lines left in the gel coat smooth using 320-grit wet sandpaper. Rinse the area clean and apply two to three coats of boat wax. Allow the wax to dry then buff the area with an electric buffer.
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Tips & Warnings
Always wear a respirator when grinding or cutting fiberglass.
References
- Photo Credit speed boat image by Roy from Fotolia.com
