Spar varnish is a polyurathane varinsh. It's specifically made for use on boats for their wood trim. It's got a lot of UV protection, and tends to last longer than many others for that use. I'm not sure how well it will work on a flexible surface, but I know I've read here that people often use it.

I used Verathane Diamond Finish Satin waterborne exterior varnish for my 12oz nylon skin. It goes on thin and dries very quickly, so recoats can go on as early as 1 to 2 hours after the previous coat. Unfortunately, each coat is thinner, and it takes a lot more coats to fill the weave. It took ten coats just to get the weave mostly smoothed out. Robert Morris' "Building Skin-on-Frame Boats" praises the waterborne varnishes as being very flexible, and not sticking to the frame as much, since the oiled frame and water don't mix.

I had very good results, but the finish is a little less durable, I think, than oil-based skins I've seen. Since my skin is free from the frame, though, the boat flexes incredibly well over swells and rough chop.

Good luck,
Mark

: Hello again;
: I have two skinned Greenland kayaks. Skinned with 8oz nylon I want to finish
: my boats with a solvent based finish. I have some questions. What are the
: differences between Spar varnish and polyurethane? Is one better the than
: other? What are the average recoat times?

: I want to get the boats finished by Saturday any suggestions

: Thanks
: Richard