I recently got a Old Town Canoe Polypropylene. Anyway it has been setting out in the weather and has cracks on one side and some bigger ones on the bottom. I spent a day on the lake with it already and it has no leaks. Just looking for advice on the best way to fill the cracks and possibly paint it. Thanks
Old Town sells two different varieties of polypropylene canoes. The “Discovery” models, for example, are triple-layer rotomolded hulls. Others, such as the “Saranac” line are single-layer PE. The single layer PE boats always have big, clunky molded seats with “footers” that extend down to the hull bottom as well as a big, clunky center “console” with a footer. Those big seats and console are needed to provide some stiffness to the hull floor as a single-layer of PE would be too flexible unless it was made so thick as to prohibitively heavy. With the triple-dump rotomolded boats a central “foam core” provides enough thickness to give it reasonable rigidity.
The difference is important because in single-layer PE kayaks and hulls the favored method of repairing simple cracks has become thermal welding. Heat, necessary for thermal welding, will deform the central foam core of a three-layer PE hull. Some claim they can thermal weld cracks in these boats, but they are few in number and special equipment is required.
Assuming you have a three-layer poly canoe, if the cracks are small you might be able to simply plug them up with something that keeps the water out. I have seen people use anything from plumber’s goop to Gorilla Tape. But that won’t restore any lost structural strength and cracks, once formed, tend to propagate. The problem is that most conventional epoxies simply can’t achieve a reasonable bond strength with polyethylene.
The one epoxy that probably will work is West System G Flex but only if you first “flame oxidize” the hull surface first. This is fairly easily done using a hand-held propane torch available at any hardware store. The detailed instructions on how to do this are included with the G Flex epoxy. For small cracks simply filling them with G Flex might suffice. For larger cracks I would back up the repair by bonding some fiberglass fabric to the hull interior over the cracks.