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How to Repair a Sun Damaged Fiberglass Canoe

Tom King

Fiberglass canoes are susceptable to sun-damage if stored in direct sunlight. The boat's gelcoat and even the hull and underlying structure may be damaged from prolonged exposure. Depending on the extent of the damage there are a couple of ways to approach the repair.

Leaving a fiberglass canoe in the sun can damage the hull.

Repairing the gelcoat itself can restore the finish and protect from further damage. Adding another layer of fiberglass can strengthen and add years to the life of an older boat.

Gelcoat Repair

  1. Clean the hull with acetone if you are only repairing the gelcoat to remove any dirt, wax, grease or oils. Sand the hull smooth with 200, then 400 grit sandpaper. Wipe down the hull again with acetone, then with styrene to activate the old gelcoat and prepare it for a new gelcoat.

  2. Mix the gelcoat and catalyst mix and stir in the manufacturer recommended amount of pigment to achieve the color you want. Apply the same measurements of gelcoat, catalyst and drops of pigment to get a consistent color.

  3. Thin the mix with the high-gloss additive if you use a sprayer. Paint the gelcoat in thin layers over the hull if using a brush. Don't mix more than you can apply before it sets up and hardens.

  4. Allow the gelcoat to cure for four hours between coats. The gelcoat should be slightly sticky when applying the next coat. Once you've applied three coats, allow the gelcoat to cure overnight until hard.

  5. Sand the hull lightly with the orbital sander and 1000 grit sandpaper and very fine steel wool until the surface has a dull luster to it. Dry the surface with a clean dry cloth, then wipe it down with rubbing compound. As the rubbing compound dries, buff it till the swirl marks disappear.

Fiberglass Repair

  1. Clean the hull with acetone and wipe down with styrene to soften the gelcoat. Sand with 60 grit sandpaper using the orbital sander until smooth. Mix up the fiberglass resin and catalyst according to the manufacturer's instructions.

  2. Cut the fiberglass cloth to fit over the hull in a single piece. Paint the hull one section at a time, laying the fiberglass on top of the fresh resin. Brush on a second coat of resin over the top of the fiberglass.

  3. Smooth the fiberglass cloth and resin coat with the fiberglass resin until it lays flat. Use the scissors to trim excess as you lay the fiberglass, Overlap the edges of the canoe with fiberglass for an inch or so to allow for shrinkage as the gel sets up. Allow to cure overnight.

  4. Sand away any excess fiberglass with the disk sander once it has set up and hardened.

  5. Apply gelcoat following the instructions above, then sand and wax the boat to protect it from further sun damage.

Bed-Liner Repair

  1. Clean the hull with acetone, then wipe down with styrene to soften the gelcoat and promote bonding.

  2. Take the canoe to a shop that applies spray on bedliners. Tape the hardware and gunwales with nylon reinforced tape and plastic sheet to protect from overspray.

  3. Spray on the bedliner over the hull of the canoe. The spray gun that the vendor uses mixes the two part solution as it sprays on. The bedliner material will adhere to the hull and dry very quickly.

  4. Remove the tape while the bedliner material is still wet in order to preserve a crisp edge and so you won't have to cut the tape away if the bedliner dries first.

  5. Cure the bedliner according to manufacturer instructions before using the boat. No further coating is necessary as the material will dry to a shiny finish and will strengthen a weakened hull significantly, although the process adds almost as much weight to the boat as an extra layer of fiberglass.

  6. Tip

    Cover the boat when storing or store inside out of the weather. If the hull is badly weakened recoating the gelcoat may not be enough to make the boat usable. A layer of fiberglass or spray-on bedliner material can strengthen the boat and give you several more years of use.


    Applying a layer of fiberglass can add 20 to 40 pounds to the weight of the boat and reduce the carrying capacity of the boat. Covering with the bedliner can add almost as much weight.