How to Repair Epoxy Glass on an Aluminum Boat

Reparing a Scratch

• 1

  Clean a scratch in the surface with soap and water. Follow this by scrubbing the fiberglass surface with acetone on a clean cloth

• 2

  Place the point on the edge of a large screwdriver in the bottom of the scratch. Pull the screwdriver through the scratch to enlarge it somewhat and rough up the surface surrounding it.

• 3

  Mix two drops of the hardener into 1 ounce of the resin in a gelcoat paste kit, in a clean container, following the manufacturer's instructions. This results in a 1-to-2 percent mixture. Mix the paste thoroughly with a plastic spoon, working the resin up from the corners and the bottom of the container.

• 4

  Spread the paste into the scratch, using a flexible plastic spreader like those available at paint stores. Allow the paste to bulge up above the level of the fiberglass; the paste will shrink as it cures. Scrape away any paste beyond the edges of the scratch. Lay clear plastic wrap over the repair and tape the edges down tightly with duct tape since the paste won't cure if it's exposed to air. Wait 24 hours.

• 5

  Pull the plastic film off. Start sanding the repair with a 220-grit sanding block, feathering the repair into the surrounding fiberglass. When you can no longer feel a difference between the repair and the fiberglass, switch to a 400-grit sanding block. Clean the sanding dust away with a clean cloth and acetone. Buff the area, using buffing compound and an electric buffer. Apply automotive paste wax to the fiberglass surface. Allow it to dry to a white powder, then buff with a clean pad on an electric buffer.

Larger Repairs

• 6

  Remove any broken fiberglass from the damaged area. Measure the depth of the damage using a machinist's rule. Multiply the depth by 12. Wash the damaged area with mild degreasing soap and water. Saturate a clean cloth with acetone and wipe the damaged area with it to remove any wax.

• 7

  Sand around the outside of the damaged area, using a palm sander and 180-grit sandpaper until you've sanded out a crater that's 12 times the depth of the damage, to give the epoxy part of the fiberglass a large surface area upon which to grip. Wipe the sanded area with acetone to remove the sanding dust.

• 8

  Cut a piece of 1 1/2-ounce fiberglass mat as large as the bottom of the crater, using scissors. Cut a second piece of fiberglass mat 1/8 inch larger than the first. Continue to cut pieces of fiberglass mat, each 1/8 inch larger than the previous one, until you have seven pieces of mat. Cut a piece of 6-ounce fiberglass cloth 1/8 inch larger than the largest piece of mat.

• 9

  Spoon five parts resin from a marine epoxy resin kit onto a hard surface, like a sheet of plastic or a piece of wood. Add one part hardener to the resin and mix the two parts thoroughly with a plastic putty knife. After you mix the components completely, spread the epoxy mixture into a thin line on the plastic or wood to ensure the mix remains streak-free.

• 10

  Spread the epoxy mixture over the damaged area with the plastic putty knife and lay the smallest mat on the epoxy. Press the fiberglass into the epoxy. Spread more epoxy over the first layer of fiberglass and add the next-largest piece of fiberglass. Press the fiberglass into the epoxy again. Continue to apply epoxy and the next-largest fiberglass until you have placed the last piece of fiberglass. Cover it with epoxy, allowing it to mound up slightly.

• 11

  Sand the epoxy down, using a 220-grit sanding block. Switch to a 400-grit sanding block when you can no longer feel the difference between the new fiberglass and the old. Clean the sanding dust away with acetone or denatured alcohol on a clean cloth. Apply paste wax to the surface. When the wax dries to a white powder, buff the surface with an electric buffer and a clean buffing pad.