- 1). Dip a rag in acetone and scrub away any wax or grease buildup located on the damaged surface of the boat. Wipe the area dry with a clean cloth.
- 2). Examine the damaged area to determine if the damage is to the fiberglass skin only or extends beyond the skin to the core material of the boat. If the core is affected, then repair the core before repairing the damage to the skin.
- 3). Fill in damage to the core material with a thick fiberglass resin. Use a putty knife to apply resin into the gouge in the core material, packing it firmly. Allow the resin to dry overnight before continuing. Check for shrinkage of the resin. If any occurs, apply more resin to the damaged core area and allow a second night for the material to dry.
- 4). Place a coarse sanding pad onto an orbital sander and smooth out the damaged area. Create a slope in the fiberglass leading from the center of the damage outward, using a slope of about 12 to 1 with the distance from the point of damage to the edge of the sloped area twice as wide as the damage is deep within the fiberglass. Surround the damage with a circular patching area to avoid leaving any hard edges of patching cloth to curl up and peel away. Wipe away the sanding residue with a cloth dampened with acetone.
- 5). Cover the surface adjacent to the patched area with newspaper affixed to the boat with masking tape. This cover will prevent splashes of the patching resin from marring the undamaged surface outside of the patched area.
- 6). Cut fiberglass cloth into patches for application with a sharp pair of scissors. Cut the cloth in circular patches beginning with one large enough to cover the original damaged area then increasing in size to eventually cover the entire patched area. The number of cloth pieces required will vary depending on the depth of the damage but make sure you have enough to bring the damaged area flush with the surrounding surface of the boat. Test the thickness by dry-fitting the cloth in place, stacking the pieces together and placing them over the patching area for fit. Use biaxial weave cloth for all but the final piece. Change to a chopmat piece of cloth for the topmost patch.
- 7). Mix epoxy resin and catalyst in a small bucket with a wooden paint stirrer to create a resin paste. Cover the center of the patched area above the original damage with a thin layer of paste. Use a wide brush to spread the resin. Wait a full minute then place the first patch over the resin layer. Brush an additional layer of resin over the cloth and use a fiberglass roller to remove any air bubbles. Wait another minute and repeat the process with the next cloth patch, increasing the size of the patch slightly. Repeat with the third cloth layer then mix a fresh batch of resin, before continuing, to avoid using resin that has hardened slightly. Continue placing the patches three at a time until you apply the final chopmat piece and layer of resin. Allow the repair to dry overnight.
- 8). Wipe the patched area with acetone then sand the last layer smooth against the surrounding fiberglass surface to remove any obvious repair marks using 120-grit sandpaper.
- 9). Wipe away any sanding residue with acetone. Remove the newspaper and masking tape then finish the surface of the boat according to the original finish type, either by painting or by applying a gelcoat to the fiberglass.
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