Zar also sells a slow-drying exterior polyurethane varnish, which is what I use on my SOFs. It's listed under the "Wood Finishing" link on their website, but there seems to be a problem with the link. Personally, I wouldn't use fast-drying varnish on any project where the quality of the finish was important. Varnishing is not the place you want to rush, especially after all the work you've put in building the boat.