Polyurethane on a boat

I've got polyurethane varnish that I want to apply to two mahogany battens that will be attached to the deck of a sailing boat. These are going to get very wet.

What's the best way to go about applying the varnish (this is also a fairly general question about finishing with polyurethane)? How many coats would you recommend? Should the first one be thinned? Should they all be, and what thinner should be used (white spirit)? Also, what grade of sandpaper should I sand the mahogany to before applying the first coat? And would rubbing down with 0000 steel wool be adequate in between coats?

So many questions - I'm a complete novice! :o

spar marine would be good for this as it's less likely to crack, normal poly will not last outside in those conditions, and i have seen some lovely poly work been done in the cockpit of a yacht but only to see it looking crapy by the folowing season, once you poly the timber can't breath and the moisture sets in somewhere...

i know of a fab. product that remains flexable and breathable, can be recoted as many times as you like throughout it's life and does'nt require sanding between coats, very easy to put on and yes it's just meant for yachts so it's what you really should use, forget the poly...

only i can't remember the name of the bloody stuff :confused:

i will find out and get back to you...

Forget the poly unless its a marine exterior one.

If you thin the first coat more it will soak into the timber and help with adhesion and sealing.

Every paint has its own solvent poly solvent for poly, lacquer for laquer , enamel for enamel.

When you purchase material get the solvent for it then,

The finer the paper the better the surface the least scratches and the harder they are to see. - always along the grain for clear finishes. Again watch steel wool as it often leaves bits stuck in the surface proper abrasive paper (nice and fine as your coat of material should be fairly smooth)

I have a tin of International's schooner varnish and their original varnish - so the stuff is made with wet marine conditions in mind. I don't know if you can get International's products in Australia but it and Ronseal seem to be the most popular for marine varnishes in UK/Ireland.

I would be interested to know what that product is La Huerta and I wonder is it available in this part of the world?

So there's even a special solvent for polyurethane varnish, durwood, shows how little I know. Would white spirit work as I already have some of it and my wallet looks as if it could do with a rest?

When you say the finer the paper is that for the bare wood prior to any coats of finish - as opposed to simply rubbing back on varnish already applied? Would you go past 1200 grade sandpaper on the bare wood?

Oh, one final question durwood, how much solvent should I use when thinning the first coat - 10%, 20%, etc.? Does it depend on the type of wood you're coating?

hey wooden ...

the guy i know who uses this stuff has been building boats all his life, and his in his 60's, so that's a lot of knowedge you know what i mean...he swears by this stuff as he has always been a traditional varnish sort of guy but now only uses this product for all marine timber applications...it's made in norway i think, so you should get it at your end...and it's so easy to apply, no skill required...

i won't keep you in suspence any longer, here is the website...
http://www.igoe.ie/cms/content/view/29/45/

let me know if you want some instructions if you don't get the info from the site or your supplier...

he reciently built a little baby ply and fiberglass runabout for fun, and used this for all the ply, it looks fab still a year later, i'll find some pics for everyone, there on my PC somewhere........

La H

Oops, it turns out that the stuff I thought was polyurethane varnish - International's Schooner actually is a tung oil (substitute?) varnish. Anyway I've used it and it seems to thin with white spirit. The application guide on the tin says to apply nine coats - the first being thinned 30%, the second 20% and the third 10. All later coats go on unthinned.

la Huerta, I asked around and it turns out that that product has been widely available around here for years. I think I might get some - depends on the price of course - as from what you say it sounds like really great stuff.

yeh it's fantastic mate, recommend it over anything else,

i'll try and find a pic of a little tender my mate used it on...