: A question - is a vent recommended even with hatches? I assume the hatches
: would let excess pressure vent out, unless held down extremely well. But
: in the case of a vacuum, the seal on the hatch may become even tighter
: than usual.

Probably depends. A kayak with VCP or the equivalent "Tupperware" seal hatches would probably hold a good seal, whether positive or negative pressure. (I blew a forward hatch off a FRG Pintail in surf once, but the pressure had more to do with the impact with the water coming off a haystack than with temps. A wooden hatch with some sort of foam or soft seal would vent positive pressure, but your point that a partial vacuum would draw it tighter is well taken.

I think the point of what I was trying to say at the start was that, in the warmer weather that draws kayakers out, we're far more likely to put a warm kayak in relatively colder water, thus generating the negative pressure that implodes decks --- or whatever the weakest point surrounding the compartment turns out to be. We certainly have the problem of blowing a hatch off a kayak after returning it to the rack --- and you can blow out a windshield in the process, apparently --- but you do not have the added potential for drowning at that point.

Jack Martin