Why are gunwales oiled instead of varnished?
Canoe gunwales are subject to incessant flexing as the boat is handled and paddled. A certain amount of flex occurs every time you take a stroke. It’s also inevitable that a gunwale will be bumped or scraped. Varnish is great for use on static pieces of wood like furniture. It is a surface protectant that provides a barrier coat against the elements. Canoe-wise, you’ll find varnish used to coat seat frames, yokes, and thwarts. These pieces are very static and rigid and not subject to flex. Flex causes problems for varnish as varnish is not very dynamic or giving. Repeated flex will create a series of minute stress cracks in a varnish coat. Bumps and scrapes will also crack or abrade the varnish top coat. Once that surface coat is cracked, water can creep underneath and affect the wood. This is evident by the gray discoloration that shows up on worn varnish coated products. Take a look at the edges of a used wooden canoe paddle and you’ll see signs of water penetration via surface crack
