I've been paddling a Baidarka caovered with #10 duck for quite a while. In that time I've run over countless rocks, logs and asorted garbage in the water. I have also landed it on many rocky beaches. At most I have only scratched the varnish. Contrary to popular belief cotton canvas it quite stroung. If I every encounter an object powerful enough to seriously rip the canvas I'll be more worried that I'll be digging splinters out of my thighs from a crushed frame. And finally, I have the piece of mind of knowing that one day my canvas will rot away naturally and not end up yet another piece of unbiodegradable trash in a land fill. Personally I think that if one goes through the trouble of building a boat with natural, organic materials it seems a shame to cover it with an odd skin made of exotic chemicals. Just my opinion. I must admit I have seen some beautiful nylon skined boats.