Long term issues, varnish over epoxy

[Antler24]

Are there any long term issues varnishing over epoxy? Im apart of a couple wooden boat groups on facebook and a couple of times folks have had the idea that epoxy under varnish will (not can, it WILL) fail as a coating and turn yellow, hazy, and even delaminate from decks. They are convinced that its not just possible for epoxy to fail as a coating, its simply a matter of time before the epoxy fails, then it needs to be stripped to bare wood. They recommend instead to use a pettit sealer under varnish, and then an acrylic on top of the varnish.


Of course this goes against everything I've learned on this forum, and Im very weary about it. I didnt give it much thought after I saw these posts a few months ago but recently I saw another member posting the same things and it got me wondering. If an adequate amount of UV protection is used and maintained, how can the epoxy degrade over time?


Any finished boats on this forum seen any long term issues with epoxy failures under varnish?

[Roberta]

I have never been a real fan of epoxy under a varnished finish. I think the reason epoxy fails under varnish is due to a lack of UV inhibitors that protect the varnish and everything below it. Varnish UV inhibitors float to the top of the product as they are applied. As the varnish "wears out" with age, it needs to be refreshed. Refreshment intervals are based on age, time in the sun, and how the boat is stored. The more protected the boat is, the longer between the time it will need to be sanded and several to many new coats applied.

On the Torpedo, I went a different route. I stained and sealed with epoxy resin. Then the finish was done using two part Poly-urethane paints. The Torpedo is entering it's 7th boating season with very little noticeable degradation in the finish. Two part Poly-urethane paints have UV inhibitors throughout the coating and do not wear off and are not sanded off when recoating.

The Zip I built had 17 coats of Epifanes varnish and has held up well. I refinished that boat in January of 2013. I don't think the new owner has had to refinish that boat and it still looked great last year. It was stained, sealed with Pettit sealer, and then the vanish was applied. No epoxy was used.

Here are some pictures of the Zip after refinishing, of the Torpedo during completion, and one taken a few days ago during some cleaning of caulk lines.

Roberta

[Hercdrvr]

I dont encapsulate the decking because varnish alone protects the wood from water and sanding epoxy is a pain. It’s all about the level of exposure. There are plenty of parts l leave bare wood, like the underside of the bow decking. If it gets sun or water under there, it’s a bad day. From the keel out to the chine is another story, I glob the epoxy on.
The most extreme exposure on my boat is the Ash wood soul. It gets lots of water and sun and foot traffic. It needs sanding and varnishing every other year. Probably why most boats have carpet on the soul.
When I started building boats and discovered epoxy I thought it was the answer for everything and I over used it. It has its function but wood in direct sunlight ain’t it unless it’s covered in paint.
My 2 cents,
Matt B

[steveh41]

Here's a quote from the System 3 "Clear finishing over wood" brochure:

"System Three Marine Spar Varnish™, a high gloss/silky satin, high-solids, "oil-base" finish, is designed for marine and exterior wood surfaces. Our Spar Varnish is a polyurethane formulation, and contains ultraviolet light absorbers which will keep wood looking beautiful even with constant exposure to sunlight. It was formulated specifically to cure properly over System Three epoxy resin products."

My 2 cents...

[Roberta]

Their varnish is polyurethane. Always good to stick with a manufacturer family or tried and true methods.

Roberta

[kens]

within today's modern age of 2-part paints, 2-part epoxies, urethanes, polyurethanes, why on this green earth would you want any old school 'varnish'??

Albeit, I did use satin varnish on the stripper canoe, and 1 reason only.......I did it on the cheap because it gonna get scratched up with crab traps.

Those same people talk about what such a FINE finish they put on their boat, and they got all the finest modern products available to them, then they talk about 'varnish'.
Polyurethanes are compatable with epoxy, this has been proven many times over.
The only reason to use varnish is to be cheap, it does not last longer, does not UV protect any better, does not look any better than modern finishes.

[Bill Edmundson]

I agree with Ken! I do have an allergy to some of the solvents used.

Bill

[Roberta]

I would not call using varnish "being cheap". It's a personal preference that can be more expensive and more work. And there are differences in look and feel.

Roberta

[Antler24]

I just wanted to bring up the question to get some other opinions. I've long decided that Ill be using WR-LPU on my build simply because of the lack of solvents. The extra UV protection and durability are icing on the cake.

[Roberta]

WR LPU is a very good product. I originally used it on the Zip. It remains on the bottom, but I did do a redo on the Brite finish with Epifanes varnish.

It is best applied when humidity is high to prevent early flashing. Use thin coats of fairly thinned product. Do not over work it and try to fix mistakes. Let it dry and sand mistakes out between coats. You can apply several coats in a day. It dries very quickly. If you coat too heavily, you'll be wiping it off the floor and creating lovely curtains.

Do any sanding prior to the paint curing. Once it cures, it is extremely hard and difficult to sand. Some people omit the crosslinker until the last coat or two so it can be sanded at a later date. The clear is very clear and will not darken any wood or stain. Follow System Three directions and recommendations.

Roberta

[Flash]

On my Flying Saucer, I used System 3 spar varnish on the deck over Interlux Chris Craft stain/sealer.

I just stained the deck for my new Zip with Cetol mahogany. I'm wondering what you folks think of approx. 2 coats of System 3 mirror coat epoxy over the stain finished off with about 6 coats of Total Boat Gleam spar varnish? My thinking is that the mirror coat would give it more depth than just varnish.

[chugalug]

Before painting "Chug",I tried a single part spar varnish over epoxy-shield.I let it sit for 3 weeks.It was just like I had applied it so check compatability.Was a pita to remove with a water-based stripper so painted instead.A 2 part might have worked.

[kens]

My Double Eagle is 15 years old now. The natural finished parts are automotive sprayed clear over clear epoxy resin.
these clears still look like new and the paint whites have faded.
some areas I experimented with epoxy primers and they failed.
ALL epoxies need UV protection, whether primer or paint or resin,
Epoxies protected by some overcoat of UV will hold up.
Epoxies not protected by some overcoat will not hold up

[Nigeb22]

Hi
I'm building a Barrelback in Portugal still very early days but as I have no experience with Epoxy I decided to make my own experiment
to see how epoxy fairs in sunlight.
I had read that it has no UV properties
What I did was to use some offcuts of the deck Sapele Ply that I intend to use and coat it with West Systems Epoxy using fast hardener.
The results after only 2 months in the winter/spring sun are all too obvious.

I painted one section is straight varnish, using Epifanes one side and a cheaper Ronseal Yacht varnish, you will see the Epifanes seems to make the colours stand out the Ronsela is turning a reddish opaque colour so full marks to epifanes

The last one after doing some reading I found WestSystem 207 special hardener with UV additives which stay within the epoxy and not like varnish
where they float to the surface and need re-coating after a year or so.
The results have been magic I have coated one half with Spifanes and both actually bring the colour and depth of the Sapele out and seem the way to go!

downside is 1.45kg of 207 was £94 and mixed 3:1 instead of the normal 5:1
Epifanes ain't cheap either but looks like what I shall be using.

Does anyone have any other epoxies that have UV protection I'd happily try them as well leave them all in the hot summer sun and report back

Cheers
Boycie's Barrelback on youTube

[Nigeb22]

Sorry the attachment would only take 3 photos this is the Special hardener 207 from West Systems which is holding up the best so far

The other pic was done when it was 10C and 90% humidity, the water vapour spoiled the epoxy almost instantly
so don't epoxy in the cold!
Doh!

cheers
Nige