Removing 2-pot Polyurethane Varnish

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wilfbishop1
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Joined: Wed Sep 15, 2010 6:12 pm

Removing 2-pot Polyurethane Varnish

Post by wilfbishop1 »

I have just been given a Fairey Duckling sailing dinghy to restore which I intend to use to teach my two young grandchildren to sail. However the immediate problem is that the boat seems to have been varnished inside & out with 2-pot poly varnish and a quick trial patch with my usual paint stripper confirms that it has no effect on the varnish al all!

I have trawled back through our archive and it seems the only way to remove this is to sand & scrape! Has anyone found any alternative method? If so I would be pleased to hear about it. The other aspect of this renovation concerns the re-finishing after I have made the appropriate repairs - It seems that there are a number of possible options as follows:

1) Refinish the hull in traditional yacht varnish
2) Epoxy saturate the stripped-back hull with clear epoxy and then traditionally varnish to block UV
3) Apply a layer of glass fabric with clear epoxy to get a clear finish then traditionally varnish

I do appreciate that options 2) & 3) are certainly non-traditional but has anyone anything to report on these two options please? I am particularly interested in durability and robustness of these two options?

Lastly has anyone found a source for Skarsten Scraper blades please? I have used these wonderful scrapers for many years but now it weems that replacement blades are no longer available?

Thanks,

Wilf Bishop
Cornish Comorant No 1 (wood) - to be restored
Cornish Cormorant No 78 (grp)
Fairey Duckling - to be restored
solentgal
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Re: Removing 2-pot Polyurethane Varnish

Post by solentgal »

Hi Wilf,

Try a heat gun on a small patch......I can't remember offhand if it works or not on 2 pack, but I always use one when I can, so worth a quick try. The best scraper I have found is the green Harris one with the 4 way blade.....blade looks like a square with a blade on each edge, 2 facing up and 2 facing down so that you unscrew the blade and flip it over as needed.....this gives 2 shorter blades one way up, and 2 longer ones the other way up. You can sharpen these blades over and over again and they last a very very long time...I think you can still get blades......haven't needed to buy any for ages though. A tip though: Many folk seem to sharpen them from the wrong direction......they are sharpened with a fine flat file from the direction you pull towards when scraping, so the file runs in the same direction as the the surface you are scraping.....and it is important to maintain the angle that is on the face of the blade when new too.....I hold mine at an angle against my workbench so it is nice and solid to file, and it only takes a few careful strokes with a good file. Sorry if this is something you know already.........but I have meant to mention these excellent scrapers on here for a while, so it may be of use to others as well hopefully :)
Sami.
Rupert
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Re: Removing 2-pot Polyurethane Varnish

Post by Rupert »

In terms of finish, I would go for options 1 or 2, not 3, unless the boat is in such a poor state you are just thinking of getting her floating for a few more seasons, as once the glass scrim is on, that is it, once any problems come to light with the veneers.

I have taken 2 pack off with a hot air blower, but I know others have failed - I think it depends on the particular type. You'll just have to give it a go. I assume it is in too poor a state just to sand back and use as a base for new varnish?

Ducklings are lovely boats - your grandkids should have a great time - don't forget to teach them to row in her, too!
Rupert
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Ed
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Re: Removing 2-pot Polyurethane Varnish

Post by Ed »

Different 2-pots need different methods!

I always try to start with heat, and then go down to stripper.

If you are having no luck with stripper.....do try first to sand the surface so the stripper can get in past the oxidised surface - seems to help. And try one of the other makes. Maybe one of these new types that you leave on for 24-48 hours before trying to remove it??

As for what finishing system.

Any of those methods can work.....but agree that method 3 will in the end limit the life of the boat...but in the short term will/may provide a stiffer stronger boat.

I don't really think there is much difference between method 1 and 2....just a choice of how 'hard' a coating to use. I used to really like using one of the really 'hard' non-epoxy wood primer/sealers like UCP or Blakes woodseal.....(maybe G4 would still work?) and then over-coating in traditional varnishes, but I don't think epoxy would be that much better or worse.

What puts me off using epoxy is getting really good penetration. (now I know that Wilf is bit of wizz with epoxy) How would you do that. Use a diluent? Work with a very thin epoxy? Work somewhere very warm? Use a vacuum?

If you don't get that penetration....then I figure UCP/Blakes/G4 is just as good and much easier to apply.

cheers

eib

ps lucky you....would love a duckling
Ed Bremner
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billytwiglet
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Re: Removing 2-pot Polyurethane Varnish

Post by billytwiglet »

These are worth a look. It may be worth using a neutraliser after stripping which will aid against any reaction if there is stripper still stuck in the grain. Some of these products are aimed at the fine carving resto market where sanding and scraping isn't an option. There are specific lacquer and 2-part poly removers in there and you can order trial packs etc.

If you give them a call they will point you in the right direction.

Has anyone had problems with the green dye they now put in nitromors? it can be very difficult to get completely off!

http://www.stripperspaintremovers.com/index.htm

http://www.paintstripper.com/paramosepaintvar.html
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jpa_wfsc
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Re: Removing 2-pot Polyurethane Varnish

Post by jpa_wfsc »

Ed wrote:
What puts me off using epoxy is getting really good penetration. (now I know that Wilf is bit of wizz with epoxy) How would you do that. Use a diluent? Work with a very thin epoxy? Work somewhere very warm? Use a vacuum?
SP systems 300 family epoxies 'eposeal' - they are carried by a dilutent, and are when applied very thin. Soaks in lovely, and then as the dilutant evaporates the two parts resin and hardener come together inside your wood and harden off. I tested some on cardboard and it came out very stiff! And certainly toughened up a 3mm deck that I restored some years ago.
j./

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Ed
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Re: Removing 2-pot Polyurethane Varnish

Post by Ed »

Yes, used to use Eposeal. Had some success with it....and some failures.

Found it very hard to get a good adhesion with following coat. Suspect you may have to 'wash' and 'sand'.

But in the end didn't think it was anything special.....just an epoxy with a diluent and reckon you get much the same by using epoxy with a recommended diluent.

eib
Ed Bremner
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billytwiglet
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Re: Removing 2-pot Polyurethane Varnish

Post by billytwiglet »

Pros and cons for epoxy:-

Pros:-
provides a longlasting protective coating
adds structural strength
Cons:-
doesn't last forever
wood moves underneath
epoxy takes more wood away when removed

analogy with brick pointing; if I re-point my victorian soft traditional brick house with cement based mortar, it is much harder than the bricks and sticks to them. When I need to repoint, I rake out the cement mortar and the edges of the bricks come away because the bond with the mortar is stronger than the brick. If I use lime mortar, it is flexible and can be removed without significant wear to the bricks. You can clean it out leaving the bricks virtually untouched and nicely sharp in detail with original fine mortar lines.

Traditional one pack varnish is to wood what traditional lime mortar is to traditional clay bricks. Renewable protection.

Merlin 36 was re-varnished nearly 3 years ago, has been sailed through two winters during which time she was liberally covered in 18" snow last year in kent, twice! I inspected the varnish under the cover a couple of days ago; decks look beautiful apart from minor marks where the cover's mast collar has let in some water, and the undersides are still excellent! Tiny spots of remedial work to wear and tear and movement of screws (no glue in the whole boat!) are required and so I will rub down to flat the surface and put on two coats of epifanes trad one pack gloss; job done! One weekend for the work, a week to dry off, then back in the water.

Main problem with varnish; sunlight. The wooden mast has the varnish cracking and peeling where it faces the sun and my other merlin has lost varnish from the stem and transom because of sunlight. The cover for 36 has an extended tail to cover the transom and underneath it looks as good as new. I will be trying to make a breathable cover for the wooden masts so that I can store them outside (25') if anyone has done this I be glad to hear your ideas.

Did I say back in the water? Bewl water reservoir has run out for the time being. The tide is so far out it's not possible to launch and recover. There is still sailing at present but not for me.
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Stephen Hawkins
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Re: Removing 2-pot Polyurethane Varnish

Post by Stephen Hawkins »

I am just starting to scrape my Merlin 950 hull.

I am soooooo glad it was varnished - heat gun a scraper and it comes off like sunburned skin....ish..

Its still going to take an age though, even the slim ones have a lot of hull!

I feel your pain.
Steve Hawkins

1967 National 12 2383 "Sparkle"
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