Brian, I've used Zar on many pieces of wood and it's just dandy. Applies easily and dries quickly. Lasts pretty good in the sun, though a yearly touch up is often required. I say, for an easy varnish for your kayak, go for it.

However, it just doesn't produce the same deep, rich finish that more traditional varnishes acquire (after many coats, of course). If you're making a show piece, whether it's a whole kayak or just a random bit of wood on an otherwise fiberglass boat, I recommend the extra work involved with using the old standbys.

Read all you can about varnishing, first . . . .

Good luck!