I have no idea why nylon is so popular.

Nylon is much more abrasion resistant than polyester. From the very early days of modern SOF construction George Dyson, eminent historian, builder of baidarkas, and seller of fabric long before it was cool, sold heavy nylon for expedition boats, saying that nylon was the only real choice, and if you wanted the best skin you'd have to put up with the loss of tension when the nylon gets wet. However- he was building baidarkas which have multiple chines along their rounded hulls, so the deflection of a slack hull was certainly much much less than a slab-sided Greenland kayak.

HOWEVER- I have seen many boats built by Maligiaq Padilla, and even worked with him reskinning kayaks, and I can say that he uses 8 oz. nylon and his boats do not get a saggy skin over time or with exposure to moisture. He wets the fabric for about an hour before he puts the skin on, and works very hard stretching the fabric around the frame before sewing, and his sewing technique further tightened the skin. When I told him how I had stretched carefully (although not as much as he did) with wet nylon he asked if I had ironed it. When I said no, he said that ironing nylon doesn't really shrink it the way that it does with polyester, but if you go slowly with a hot iron it sears the fabric, slightly melting it, and making it dimensionally stable in the face of moisture contact. I think that the reasoning is highly anecdotal and not very scientific, but I've never seen one of his qajaqs get a slack skin, and I've seen quite a few of his qajaqs over t he years.

m