Polyurethane or varnish

[mgamike]

Ok, so what is the best and most durable exterior finish? Varnish or Polyurethane? Are any of the water based finishes worth consideration? I just finished constructing new doors out of Sapele and Lexan for our companion way and would like the finish to hold up. They will get a few weeks use out of the year otherwise we use the hatch boards.

[MarkSF]

No simple answer. Polyurethane is physically tougher, but spar varnish is more sun resistant. I'd say spar varnish is more attractive too.

I have main hatch boards, and some slot-in replacements with Lexan windows, all with spar varnish. Every few years they start to look scruffy from physical abrasion, but I just give them a light sand and an extra coat of varnish. Hardly a lot of work.

The companionway steps are done with polyurethane and wear great, but are not as attractive.

[Reefmagnet]

I think polyurethane doesn't "breathe" like varnish does. We painted some washboards with ployurethane a few years back and after about 12 months, large blisters formed under the ployurethane on the outside facing surface which I assumed was from the moisture in the wood not being able to escape through the coating. Haven't had that happen with varnish in the same situation.

[Cheechako]

I used Varathane Exterior on parts of my early boats. I liked it alot. I also used McCloskeys Spar varnish... it's a bit gummy but good. I preferred both to the Schooner or Z Spar Yacht Varnish.

[s/v Beth]

Had all exterior bright work done with poly 3 years back. Within a year it had bubbled and looked horrible. Finally removed the remainder with a heat gun and did cetol. Will not be going back.

[Cheechako]

I think you guys had prep problems... no reason Polyurethane should have bonded any worse than regular varnish.
I used Cetol on my 44 for a while, the nice thing is you dont really have to do much prep to add more, the bad thing is... you better be adding more constantly!
But yeah, it's all a compromise when it comes to outside wood for sure.

[casual]

Fasco water based UV 25 varnish.Small co from Miami. Applied 10 coats to my bowsprit 15 months ago still looks fine. You can apply a coat every hour or so depending on temp used a foam brush.

[Reefmagnet]

Originally Posted by Cheechako

I think you guys had prep problems... no reason Polyurethane should have bonded any worse than regular varnish.
I used Cetol on my 44 for a while, the nice thing is you dont really have to do much prep to add more, the bad thing is... you better be adding more constantly!
But yeah, it's all a compromise when it comes to outside wood for sure.

It wasn't bonding; the blisters were pressurised and had moisture inside them. I live in the tropics so rain and humidity come with the territory.

[s/v Beth]

Cheech- mine were done professionally by our man in Bellingham. I think it is a product that is not suitable for our climate.

[Cheechako]

I've not applied it in the tropics... have taken the boat south after applying north with no issues. But yeah... application in the tropics...IS different. I learned that 5200 applied on too hot a day down there ended up with bubble gum like balloons the next morning! I assume the 5200 skinned over too fast and then the outgassing from inside blew up the balloons.
Newt- mine was done in Seattle with no issues. I learned long ago that a PRO ....when it comes to varnishing can mean a lot of things... often just an artist who likes to use a brush. Think about it.... if he was a PRO, and if Poly isnt any good.. then why would he apply it? There's a conundrum there somewhere!

[Suijin]

If the doors don't get that much use/exposure, I would go with Varnish, the full 12 coats routine. They'll last for ages. Varnish is pretty hard and scratch resistant...it's a good finish for things that get moved around, like hatch boards and so forth. I would recommend Cetol (two coats of natural followed by two coats of clear) since it lasts longer in the sun and annual maintenance is much easier, but it's not as hard as varnish and so not as durable for things that get handled, in my experience.

[minaret]

Originally Posted by s/v Beth

Cheech- mine were done professionally by our man in Bellingham. I think it is a product that is not suitable for our climate.

Any pro worth his salt knows that poly must be applied as a final coating over traditional varnish, not just naked poly. There are numerous varnish systems designed to do just this, ie traditional varnish with accompanying poly designed to work together. I use Awlspar top coated with Awlbrite. Works great.


http://www.awlgrip.com/products/varnishes/awlbrite.aspx



Together, these products are marketed as Awlgrips "Ultimate Brightwork System". This is how most megayachts are finished in the US.


http://www.awlgrip.com/support-and-a...rightwork.aspx



System II. Ultimate Exterior Brightwork System - Awlspar/Awlbrite Clear
This system combines the color highlights of the Awlspar Varnish to provide a traditional look, with the durability of the Awlbrite Clear in a fast recoat, relatively easy to repair combination of varnish and urethane coatings.

Awlbrite Clear has a unique blend of solvents that can be applied over Awlspar. This allows for the system to be sealed and protected by a tough, durable two–pack urethane that is easier to repair than other similar systems.

The rapid cure of Awlspar combined with the Awlbrite Clear eliminates the typical 30–60 day wait between varnish and urethane. The system can now be completed in little over a week.

This union of Awlspar and Awlbrite Clear allows you to have an easy application system, traditional appearance, and long term durability allied with low maintenance.

[Cheechako]

I guess the real key isnt so much what you use but getting the 12 coats. Once you have that done well then add at least 3+ coats a year and it last supposedly. ME.... I never got past 6 coats or so..... Done it all, Cetol, Poly, Spar, Oil, Bare. I'll take the salt water wash!

[Hudson Force]

Polyurethane or varnish? ...no way! I quit that choice many years ago. I'm strictly stainless steel, polycarbonate and Starboard plastic over fiberglass. I can't justify a surface that requires repeated maintenance. All my pretty wood is below!

[minaret]

Originally Posted by Cheechako

I guess the real key isnt so much what you use but getting the 12 coats. Once you have that done well then add at least 3+ coats a year and it last supposedly. ME.... I never got past 6 coats or so..... Done it all, Cetol, Poly, Spar, Oil, Bare. I'll take the salt water wash!

12!? Try 16 minimum for teak....