One more note. I've just spoken with David Taylor, author of Boat Building in Winterton, Trinity Bay, Newfoundland. (Handily, he happens to be my boss, so I see him every day.)

His take from the verses he knows is that the song is not making fun of the boat. It's the narrator that comes off looking foolish. "Chinched with putty" and "planched with nails" aren't terms out of boatbuilding that he was aware of. Looking them up on the Dictionary of Newfoundland English, I find that they come primarily from housebuilding: "planching" is laying floorboards and "chinching" is sealing the walls of log homes. David says in Trinity Bay they weren't used for boats.

The proper term where he was was "corking" seams on a boat, which indeed means to seal against leakage in the DNE.

Furthermore, David says every seam would normally be corked. So it's not the technique that sounds wrong in this song, it's the description. Specifically, it sounds like a landlubber describing boatbuilding techniques.