Do It Yourself: How To Repair A Fiberglass Canoe

Fiberglass canoes are relatively easy to repair with fiberglass cloth and epoxy resin. Here is a step-by-step explanation of the process and the tools and mateials needed.

If you have a damaged fiberglass canoe in need of hull repair, consider yourself lucky. Even severely damaged fiberglass canoes can be brought back to like new condition. Canoes built of other modern materials, such as aluminum and varieties of plastic composites such as Royalex are often not repairable at all.

Fiberglass canoes are repaired the same way they are built, by laminating layers of glass cloth onto the hull with fiberglass resin. The first step is to access the damage and gather the required materials. Damage can be in the form of abrasion from dragging your hull over rocks or sand, or it can be more serious impact damage resulting in cracks or even holes in the hull. To prepare the damaged area for new layers of glass and to really see the full extent of it, you will first need to sand or grind the surface of the area surrounding the repair to remove the Gelcoat and loose material. Sanding is best done with a random orbital sander, but a small electric finishing sander will also work, it just takes longer. Belt sanders should not be used, as they can quickly remove more material than you might have planned for. Use course sandpaper, of 36 to 60 grit, for the initial grinding. After this is done, you will be able to tell how much fiberglass cloth will be needed for the job.

Fiberglass cloth is sold by the yard at marine supply stores. It comes in a variety of cloth weights, but for canoes, which must be kept lightweight, all you are interested in is 6 oz. cloth. This weight will provide adequate strength and still be thin enough not to soak up too much resin. Resin is the key to fiberglass work, and while most canoes and fiberglass boats are built with cheaper polyester resin, for repairs I recommend using epoxy resin. This is not the 5-minute epoxy sold in hardware stores, but rather boat-building epoxy which you can find in marine supply stores. It is a two-part product, consisting of resin and hardener. Boatbuiding epoxy is expensive but you will find plenty of other uses for any you have left over. You will also need a small amount of filler for the epoxy to mix up a thickened batch that can be used for leveling the surface and filling small holes before the glass cloth is laminated on. A wide variety of fillers are sold by epoxy manufactures, but all you need is the one called "microballons." This is a white powder that will make a thick paste when mixed into the epoxy.

To work with epoxy, you will need mixing cups to mix up batches of resin, disposable bristle brushes to apply it, and disposable latex gloves to keep it off your hands. Buy a small can of denatured alcohol for cleaning the surface to be repaired and for wiping off any excess epoxy that might get spilled.

With supplies ready, you can now begin your repair. If your damage is a deep abrasion, you will simply apply one to three layers of fiberglass over the area from the outside. The first step is to mix up a batch of thickened epoxy with the microballons and use this paste-like compound to fill in any holes and level out the surface. This works like spackling compound in drywall repair or Bondo in automobile body work. Wait for the thickened epoxy to cure, then sand it smooth, blending it in with the rest of the hull. Add the glass cloth using a batch of pure epoxy without fillers. Paint the resin on with a disposable brush, add a layer of cloth, and then "wet-out" this cloth with more epoxy until it becomes transparent in the resin. It is important that the cloth is completely "wetted-out" so that there are no dry spots. Add a second, slightly larger piece of cloth over the first so that it covers the edges of the first layer and wet it out as well. When this cures, paint on another layer of epoxy; wait for it to cure, then sand the whole area smooth. In most cases, this is enough, but if the results are not satisfactory, you can laminate on more layers of glass cloth in the same manner.

Cracks and holes that go all the way through the hull have to be repaired from both sides. This is done by laminating layers of glass cloth on the inside as well as the outside. It may take some practice, but with epoxy and fiberglass, you can learn to make repairs that are invisible. This brings you to one final choice. Do you want to paint the newly-repaired surface or leave it visible as a "battle scar" that shows how much you use your canoe? A hull full of fiberglass patches is the mark of a true river veteran and will make you the envy of the beginners with their shiny new canoes.

© High Speed Ventures 2011