stripping varnish

[paul oman]

I'm beginning the restore of an old firefly sailing dinghy. It's vanished deck and interior
range from no varnish to thick solid varnish 'where the sun don't shine.'

The paint stripper I picked up at home depot barely seems to lift the varnish. I tried a heat
gun with about equal success.

Can anyone offer up some tips and tricks to speed up the job?

paul oman
progressive epoxy polymers

[Wild Wassa]

I think that there is no one stripping technique for old boats, everything is valid, so when the going gets tough, out comes the sander/polisher. If you are not adverse to using a sander/polisher strip as much off as you can with this tool.

Are you sure it is a varnish and not something like an old Estaplol?, or varnish and an Estapol (type) in combination or alternating. Both poly and varnish can heat-up far too quickly if the coats are thin and layered or different paint types are alternating. Thin coats harden and become very dificult to remove with heat, ... I did find, once.

When this happens I reduce the gun temperature, which heats the skin slowly and I keep the gun moving otherwise the tendancy is to scoarch the wood. This will require more heating time (at a lesser temperature) and I don't try to strip in full blade widths when the paint is stroppy. I remove edges of the film, 1cm at a time (in lengths of about 10-20 cms or longer if possible) ... it is a quicker technique than it sounds.

Do you use a carbide scraper (with a pulling action) or an Oldfield's stripping tool (for pushing)? Each scraper type, works well on some paint types and not others, so try different tools.

If you are not adverse to using a paste stripper (although the gel stripper didn't sound good), could I suggest a product like Peel-Strip. Peel-Strip is a paste stripper backed with a rolled on sheet (to exclude air), then the total is peeled off at once, once the stripping time is worked out. A test kit will allow you to calibrate the stripping time/s.

Hydro blasting, high pressure water blasting at (3500psi) I'm about to do my house exterior, or pay someone to do it for me. If you do try hydroblasting make sure the hydro blaster's pressure can be adjusted to 'make sure' you don't damage the timber, this one works well but is inherantly risky at 3500psi. Testing the paint removal and jet pressure that will be needed, is essential. If timber doesn't look sound enough to be hydro blasted, it won't, guaranteed.

Good luck I hope this helps. It will be good to see a Firefly dinghy on this site.

Warren.

[ 11-08-2004, 06:03 PM: Message edited by: Wild Wassa ]

[wndsnd]

Hi Paul,

Knowing your epoxy expertise, I thought I would give you my 2 cents.

I have a 1969 Tartan 37 Blackwatch that the previous owner restored in 1996. He brought all the cockpit teak down to bare wood and sealed with epoxy before finishing with multiple coats of varnish. I purchased the boat in 2000, and the brightwork looked good. I don't know what he used for brands etc, however I know the epoxy he used was hardened in drips under the cockpit coamings. I guess he either didn't see them, or just let them go.
Last year I noticed that moisture had got under the epoxy, and was working its way down the coamings. By the end of the season it was pealing off in sheets. My guess is that the epoxy was not thinned enough to penetrate the wood fibres for a good bond, or the wood oil just did it's thing over time. I doubt he used CPES or a similar product. So... I embarked to take it all down to bare wood again this year, and found that a heat gun, or propane torch with difuser on the mooring, and good scrapers did the job, even where the epoxy and varnish were well bonded. It is hard tedious work, but it does the job. My problem is getting the heat near other painted (Awlgrip) surfaces or winches. I wanted to use a solvent there, but noticed on the Smith's website that CPES might have problems if I choose it to be my next sealer. Anyway, in my mind sanding is too destructive and scraping is just painfull. It is so dam hard to get off, yet the sun reeks it havoc, the prices we pay.

[Victor]

Sounds like this boat won't take too much sanding or scraping. I found the various brands of stripper vary tremendously in their effectiveness. Shop around. I don't know about that hydro thing, Warren - sounds like he'd blow a hole through it before he'd get that old varnish off.

Also interesting, with stripper, a piece that looks totally bare just keeps producing more old varnish with every app.

[ 11-08-2004, 05:26 PM: Message edited by: Victor ]

[paul oman]

Hi Guys

thanks for all the feedback. I am trying the chemical stripper I bought covered overnight with a sheet of plastic. Will see what happens. Also testing our 'solvent less' cleaner on it too which will soften epoxy if left on long enough. If something amazing happens I will get back to you guys.

- the firefly needs so much work, I got it free! I purchased a used boat trailer and the seller asked if I wanted a free boat with it! Anyway, a have a tiny fleet of small sailing dinghies (but no time to use them!). I spent my college summers as a sailing instructor...

Wndsnd: about your stripping varnish covered epoxy.... about a year or two ago I coated a piece of wood with unthinned marine epoxy and then covered about 8 spots on it with various clearcoats to see which would hold up the best. It has been sitting outside here in NH ever since. What has happened is that the epoxy has started to fail/peel for the edges of the wood and along cracks etc that have developed in the wood. Instead of figuring out which topcoat is best, I've learned to treate the wood first with solvent thinned eopxy for better penetration. I recently talked with a 'traditional boat builder' and he uses solvent thinned varnish under more coats of lesser solvent thinned varnish with great results (no epoxy for him!)

-----

I had another posted question about osmotic blisters a day or two ago. I wanted to find out now long it took for blisters to form - it should be a slow process. After averaging the results for here and other places, I think (can I assume this?) that it takes about 2 years (with polyester hulls). We had a customer who used our barrier coat epoxy (2 coats) last year and when they hauled out recently found lots of new blisters. I suggested these were pre-existing blisters that were too tiny to see last year but had grown since then. I don't think you would get fresh, new blisters, especially thru a two coat (about 15-20 mils) epoxy barrier coat system, within one year. Am I right or am I missing something??? I certainly respect all of your opinions.

paul

[Hwyl]

Be careful Paul. The outer veneers are pretty thin on your Firefly. Also look out for delamination where the veneers meet the keel ( a spot of epoxy might help there).

Call me if you need help with rigging, they have a very different jib halyard tensioner. Do you have the all aluminum mast or the older (and much better) aluminum mast with wooden top section.

[Wild Wassa]

G'day, I've seen (what might be called) delamination through osmosis (which I originally thought had happened to the boat) but which turned out to be fine fisheyes caused by the sun's heat. The hull was upturned and uncovered outside, for three months, when she was first painted (She had been kept inside prior to painting).

When I examined the paint it was fisheyes not osmosis that I think had formed from expanding gas as the boat had been kept dry and had hardly seen water. None of the fisheyes were broken (?), so I feel it was gas expanding between the interfaces that caused this problem. When I broke the fisheyes (the largest one was the size of a small finger nail), I could find no hint of moisture absorption. I expected to find some cloudiness in the epoxy from moisture but found well defined bubbles in the epoxy.

I didn't paint the hull (so I'm unable to retrace all the steps fully). There was an excess of air, fine bubbles were in the paint skin and in the epoxy underneath (caused through mixing and then by roller applications I think). Also the paint was a polyurethane that was not physically keyed adequately to the epoxy coat (I'm guessing, knowing the workers). The epoxy was a non blusher from Boat Craft Pacific, so I don't think that the lack of adherence between the interfaces was caused by amine blush. After seeing how the boat had been positioned in the yard all the blisters were on the hull, on those areas that were directly in the sun for the 3 months. Any parts of the hull that had been kept in shade showed no problem areas. I think that this examlpe was caused by excessive heat. When the boat was the right way up it looked like water absorption had started to cause osmosis problems.

Also, I’ve recently found fine craters in a paint skin on a foil. Filtration to expel air is somewhat essential with polyurethane after finding problems recently. There is something about air in paint that I think tends to be overlooked, that shortens the life of the paint. With the quick skinning of polyurethane the paint can have fine bubbles burst on the surface and without any self levelling properties and with the rapid skinning of the poly, these very fine bubbles become craters with no coat over the underlying layer. That will give a way in for water to seep between the interfaces and start the absorption of water in the underlying layers.

All osmosis problems (that I've seen or chattered about) have formed on fibre glass hulls, after the breaking of the gel coat. One boat (I've talk to her owner Hankey Pankey out of San Fransisco), had a repaint and the fibre glass wasn't dry (the owner thinks) when the painting was done. I've had a good chat with her owner and he feels that the hull may have been still wet when the boat was painted professionally, the osmosis problems started almost immediately after the first painting. The boat was stripped, allowed to dry, sealed with something like 'Interprotect 2000E' and then recoated. He reported all fine after the repainting was done ... time will tell.

Warren.

[ 11-09-2004, 05:11 PM: Message edited by: Wild Wassa ]

[sdowney717]

Blisters can also form from water penetrating from the inner surface of a hull. So perhaps the epoxy barrier coat is working keeping water out but water from in the bilge area is still working to produce more blisters.