Spar Varnish

Any Advise?

About two years ago I built a cedar strip drift boat. It really came out nice, but I'm going into the third season and decided to put another coat of spar on to build the finish a little. The boat is totally epoxied with glass cloth and three coats of spar. My question is, why do all the spar varnishes say "not to be used below the water line".
One distrib said it's ok but not for long term, meaning over 6 or eight hours( that doesnt seem long). What is everyone using on clear coat boats and canoes. I want to take the boat on a week long trip. Do I take it out of the water every day?

Thanks Coop

 

Although the finnishes are for use in the marine environment, these paints are by no meens water proof. A well known example (at least more so than varnish) is gel cote. any boat finnished with it below the water line can land up with osmosis (blisters of water that has permiated through the membrane of gel cote). This is why the suppliers have said do not use below the water line.
On the other hand, I have seen varnishes and paints last at least a week below the water line and have no problems at all. If you were to use some form of Spar Varnish (note Spar means mast and not hull) you would probible find that a two part epxy or ply-urithane finnish would be best.
how long it would last is anyones guess.
p

 

West Systems makes a UV resistant epoxy varnish. It last several years on Florida boats. I am not sure if it is rated for bellow the waterline use though.

 

I'd expect you'll be okay. After all, there isn't a whole lot of difference between what you're going to do, and having the topsides of a boat get rained on for a week. I've used spar varnishes on wooden racing shells for years without problems, both above and below the waterline, and there's been plenty of times the boats have been wet for days on end.

Those are oil-based spar varnishes. Don't know if anyone's using water-based varnishes, but I'd personally steer clear of that. Also, no idea how it holds up to salt water. As someone stated earlier, the lifespan may not be that great, but you've got epoxy and three coats of varnish underneath. I'd recoat in a year just to see.

Regards,

Matt Turner
Turner Racing Shells Ltd.

 

Thanks for the comments and advise , everyone..... I'm going to stick with what is on the boat which is Z-spar Flagship varnish. It has held up nice so far. I also like to wax the bottom heavily, that seems to help. Part of owning a wooden boat is the maintenance, I'm sure every wooden boatbuilder has been told "you could have bought an aluminum boat and had less upkeep" I usually dont even try to explain. Nothing against aluminum outfits, just a different purpose entirely.

I think I will try a two part finish on my next project.
Thanks again. This is a great site, its nice to read discussion and info on boatbuilding. Not much boatbuilding going on in my local area.
Coop