: The basement temp is about 50 deg. F. (or just slightly over) because I had
: to add a little heater when I used to work with epoxy to bring the
: temperature up a bit to a decent curing level. It doesn't matter really
: for sewing nylon as long as there isn't excessive humidity.

You mean 'as long as there -is- excessive humidity' , don't you??

I skinned at 70 deg f and maybe 70% rel hum as measured on a hygrometer. I kept misting the Dyson 8 oz nylon with a Windex bottle and sewed the cloth as tight as possible after pinning to the gunwales. Now any time the humidity is over whatever I skinned at it goes slack. But if the sun hits the skin it tightens up, even when being wetted while paddling. You used water based PU and I used oil based PU but that should produce the same results...

If I ever do this again it will be after someone writes a definitive book on materials and coatings for kayaks!

Still confused,
Rich