Repairing Polyethylene: Cracks and Fractures

One of the universal truths about polyethylene is that it is difficult to repair. Fortunately, it is a material that rarely needs repair, but there will be times.

Shallow scratches and gouges are sometimes best lived with. Unless quite deep, they are cosmetic in nature and will not impact the integrity of the hull. If you have some gouges with raised “feathers” of material around the edges, there’s no harm in using a sharp knife to trim away those feathers.

If the unlikely occurs and you have an actual crack in the hull, it’s a different story. Depending on location and extent of the crack, it may or may not be repairable. It is very difficult to perform a structural repair on polyethylene and if the crack is extensive or in a critical location, it may pose a hazard to continue to use the canoe and it may be time to take it to the recyclers. The best way to determine whether such an injury is fatal is to contact customer service and email pictures to them. They can advise you of your options.

The Adventure series construction is single layer polyethylene and a crack in the hull means a crack that goes all the way through the hull. If the crack is small, you may be able to keep the canoe functioning by melting some linear polyethylene onto each side of the hull for the length of the crack, kind of like filling a gouge in a PTEX ski base with new PTEX. Polyethylene has a low melting point and a lighter is usually sufficient to kick the material to a liquid state. Simply drip the new material over the top of the crack and for about ¼” beyond each end of the crack. Then repeat on the opposite side of the hull. If you have some buildup at the edges of the new material, it is a good idea to lightly sand those areas until they are fair to the hull. Leaving a sharp edge to the patch makes it more likely that the patch can be scraped loose as the boat crosses an obstruction.

Unfortunately, there is no reliable adhesive that can used in conjunction with fiberglass cloth to build a reinforcing patch over a crack. There are adhesives making such claims but results continue to be mixed. However, if your boat is laid up due to such a crack and the option doesn’t exist to replace it, there’s not much to lose in trying some of the new “wonder” adhesives. If you give this a try, it’s best to retire the boat from demanding waters and just use it on friendlier protected waters as there’s no easy way to tell how effective your repair is or will be.

Improved results in terms of getting adhesion between repair and hull are obtained by first sanding the hull surface to create a texture and then “flaming” the hull in the area to be repaired. Flaming consists of passing a torch or open flame back and forth over the hull, keeping the flame moving at all times and removing it before the material shows any sign of melting. For best results you should be prepared to proceed with the repair immediately after flaming the surface.

The patching process consists of spreading a layer of adhesive or resin on the interior of the hull over the crack and extending about 1” beyond the edges of the crack. Then take a cut to fit piece of fiberglass cloth and embed it into the adhesive or resin you just placed on the hull. Next spread a layer of adhesive over the patch cloth and lay a second patch on top of the first, allowing the edges to overlap the first layer by about an inch. Again spread a layer of adhesive over the 2nd patch layer. Continue adding layers until hull is consistently stiff between repaired area and unrepaired area.

All patch layers should be placed on the interior of the hull and the exterior of the crack should be covered by the polyethylene drip method described earlier. Placing patch layers on the exterior of the hull is just asking for them to be peeled off by encountering sand bars, gravel bars or other obstructions on the water.

Again, be conservative in how you use your repaired canoe. Inevitably, the repaired section of hull will be more rigid than other areas and therein lies one of the challenges of polyethylene repair: the innate flexibility of the material. Poly can distend, bend, distort, deflect, etc., very easily (in fact, that’s one of the “secrets” of its durability). It “absorbs” impact by flexing away from it.  The challenge is finding a material that is as elastic as the poly so that it can bend and distort equally and not separate from the hull.