How to Cover a Wood Box With Fiberglass & Gelcoat

Measure the length and width of each side of the box.

Cut your fiberglass panels to fit the dimensions of the wooden box using a power circular saw with a carbide blade. Wear eye and skin protection whenever using a power tool to prevent fiberglass splinters from causing injury.

Wash off the wooden box with oil soap and a soft sponge to remove any dirt, dust or debris that could interfere with the bonding process. Allow the box to fully dry before continuing.

Apply epoxy glue to the back of each fiberglass panel and then press them firmly, one at a time, to the wooden box. Wipe away any excess epoxy that leaks out with a soft rag. Allow one panel to dry fully before applying the next panel. Continue until the box is covered in fiberglass panels.

Squirt a silicone sealant into the seams between panels to help prevent moisture infiltration.

Sand the fiberglass thoroughly with course sandpaper if a gelcoat is not already applied to the panels. This helps prepare the fiberglass surface for gelcoat application. Run a fine piece of sandpaper over each surface after the initial sanding and wipe away loose sand with a rag.

Clean the fiberglass with a rag and an acetone-based cleaner. Ventilate the area because acetone fumes are harmful. Wear rubber gloves and safety goggles. Use a respirator if possible.

Mix the polyester resin of the gelcoat with 1 or 2 percent methyl ethyl ketone peroxide. The methyl ethyl ketone peroxide is a catalyst for the resin to form the gelcoat. Add a small amount of styrene to thin the gelcoat if necessary, but only add 10 percent max. Follow all safety and usage instructions on the packaging for best results. Once the gelcoat is fully mixed, add it into a gelcoat sprayer. Gelcoat usually damages a regular paint sprayer because of its thickness and hardening properties.

Spray on the first coat of gelcoat and then add a second coat after the first coat starts drying. This gives the fiberglass a more durable finish.

Wax the gelcoat once it is dry by rubbing a boat wax on it and buffing it with a rag. Do this in two coats for maximum protection.