Its simply the nature of nylon. There seems to be quite a lot of variation in sewing/shrinking techniques and actual material, so some nylon skins seem to get the raisin look easily while others never loosen. Nylon skins should return to their original state after drying out for a while, however.

The retrieval 'yak I have is skinned in 12 oz. nylon and coated with Zar (though I didn't build it, so I don't know how many coats are on it or where the fabric was purchased). The deck will loosen *slightly* after being cold and wet for several hours, but the hull never seems to change at all. There are definitely more coats of poly on the hull for whatever that is worth.

Having said all that, I've also had "drum tight" linen and polyester fabrics go permanently wrinkly after coating, even with Zar, although I think it had something to do with how I applied the coatings (not enough drying time between coats). Both of the problem fabrics were meant for upholstery, so its not really a fair comparison to the higher denier material that is typically used for kayak skins.

I tried to heat shrink a coated sample of the polyester fabric, and did not have good results. The heat caused the poly to burn/fail before the skin would shrink, and I would be wary of trying to do this on a completed skin, even though in theory it should work. Just a warning, that is all.

: What did I miss here? 12 oz nylon from George Dyson. Drum tight last night
: when I went to the water. Paddled new boat for an hour I guess. Load it on
: the trailer and come home happy as a clam.

: Walked out to the garage and the whole skin is loose on the boat. It's upside
: down and dry. What the heck happened and how do I prevent this in the
: future? ZAR finish.