How to Repair the Bottom of an Aluminum Canoe

Inspect the seams along the keel. It may be helpful to clean the keel with a strong stream of water and dishwashing soap. Pay particular attention to the area below where water was observed leaking into the hull, but remember that water can travel laterally through gaps in the aluminum seams. The keel may be constructed of rivets, welding, or a combination of the two. Pay attention to any areas where the seam isn't uniform. If your canoe is painted or has any type of coating, pay particular attention to areas where the surface is chipped.

Clean an area with a radius of at least six inches around the source of the leak as thoroughly as possible. First use a sponge and dish soap, then dry the area with a cloth. Do not clean the repair area with alcohol or mineral spirits, as this may affect the performance of the epoxy. Instead use acetone or lacquer thinner if necessary to prepare and clean the surface of the aluminum. Never allow acetone or lacquer thinner to come into contact with any paint or exterior coating, as it will ruin the finish.

Ensure that the keel is in its proper shape and is symmetrically aligned. If the leak is caused by a physical distortion of the keel fin, the first step is to return it as closely as possible to its original shape. Like auto body repair, you can do this by carefully hammering the metal back into shape. Do not strike the aluminum directly with a metal hammer because this will fatigue the metal and lead to future problems. Instead hit a small block of wood held against the area being shaped, using gentle, controlled blows, ideally with a rubber mallet. Be patient, and remember that the symmetry of the keel is important for navigating the canoe in the water. When you are satisfied with the shape of the keel, you are ready to apply the epoxy sealant to the seam.

Mix the epoxy as directed by the manufacturer's instructions and quickly apply along the seam, overlapping the gap by at least two inches on each side. You may wish to spread the epoxy along both sides of the entire keel beyond the repair area to prevent future leaks. To avoid the epoxy setting prematurely, work on one area at a time. Use the body filler spatula to work the epoxy into the crevices and around the rivets to assure a strong seal, and make sure that there are no bubbles in the epoxy. At this stage, it is better to apply too much and not worry about irregularities--you can sand these out later. When the leak has been adequately covered, clean up any excess epoxy, as directed by the manufacturer, and allow it to fully cure.

Inspect the keel after the epoxy has cured (usually overnight) to make sure that it has properly set. If you are satisfied with the uniformity of the epoxy, your work is done. If there are significant irregularities in the cured epoxy, you may sand the epoxy to achieve a more regular surface. In extreme cases, or for cosmetic purposes, you may wish to use a marine body filler (available at many auto repair stores) to smooth out the keel. Make sure that the body filler is approved to bond with aluminum, as many fiberglass fillers may simply peel off. Once the body filler is fully set, you may sand and paint as instructed by the manufacturer. You may paint or coat over the repair as much or as little as you desire.