: I think that would be more of a problem with a kayak, with its
: complex section shape, than a canoe. I use rachet straps on my
: plywood canoe all the time, don't bother to slacken them when
: the car is stopped even on a hot day, never had a problem,
: although I certainly wouldn't do that to my plastic kayak.
: Upside down, the canoe's gunnels sit nice and square on the
: carrier with foams block between them, and the straps hug the
: outside of the hull so the plywood is under compression.
: Probably, if a kayak had a snug fitting cradle it would be OK
: too.

There is a fine line between having it tight enough with the ratchet straps and crushing the boat. Can't get enough tension without the ratchet straps to hurt the boat yet you get enough tension to hold the boat onto the cartop easily. I've seen about a half dozen over the years that required very expensive repairs because of using ratchet straps. I've got a canoe too btw :)

Bill H.