Stopping the rot?

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Michael Brigg
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Joined: Fri Jul 06, 2007 7:11 pm
Location: Gosport, UK

Stopping the rot?

Post by Michael Brigg » Mon Jun 23, 2008 7:50 pm

Does anybody out there have any experience with CUPRINOL as a primer of bare wood before varnishing as a means of preventing rot especially in those “difficult” nooks and crannies where the sun doesn’t shine??!

I only ask because I was applying the clear variety to a newly exposed timber frame where a rather unruly passion flower had recently been brutally pruned and noted the instructions for its use as a primer on “timber window frames and doors” before “Varnish and paint overcoats.” It was, as it said, clear, and didn’t cause anything other than some slight darkening of the grain on what was admittedly cheap if well seasoned pine.

I already know that the best thing to do is try it out on a test piece, but I’m damned if I have the time and I’ve always felt that after all that stripping and repainting there must be some additional, possibly TRaditional way to stop the rot when using varnish. After all painted hulls can be liberally doused with a variety of toxic heavy metal finishes in ghastly shades of metallic grey or purple, safe in the knowledge that a few coats of undercoat and overcoat will produce a finish like a shiny white ceramic tile, but what about the clear stuff? Is there anything out there other than watered down varnish? Our forefathers no doubt had the time, skills and supply of material to be able to regard their material as disposable (yes, even best quality rainforest hardwoods!) so some traditional methods are as much of a first aid bodge up as some of our modern ones. “Black varnish,” that devils brew of coal tar and varnish comes to mind for one. (I’m sure it’s what they line the closed tanks on a firefly with, and it really doesn’t come off anything and breaks through any finish.)

However, to get back on track again, about wood preparation: Lets presume I’ve managed to strip all my 524 lands and sanded/scraped to bright new wood. Can I preserve this? Also as I progress snail like from stern to bow, can I deep treat the wood in some way to prevent it from drying or cracking as I am sure this process is going to exceed a year or more!

Harry Potter has a bottle of Broom oil for his Firebolt and as a wee lad I well remember there was a certain pleasure to administering a weekly application of linseed oil to a “new” cricket bat. Now does the same apply to the newly exposed and seemingly thirsty wood of a boat that last saw exposure to fresh air some time before our darkest hour?

…but was it raw or boiled? Would teak oil do it better, or is it just for teak. How much to water it down by and what with? Turpentine, White spirit or Turps substitute.

What is the true science and chemistry behind these various witch’s brews and are they really better?
Michael Brigg

Rupert
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Joined: Thu Sep 16, 2004 8:40 pm
Location: Cotswold Water Park

Re: Stopping the rot?

Post by Rupert » Mon Jun 23, 2008 9:26 pm

I've used Varnol from a place called Black Dog stores, which was a mixture of tung oil and varnish, and it went on great, and soaked in really well. I've never heard back how well it lasted, though.
Cuprinol has been used as primer. The Firefly it was used on back in about 1970 recently had a new plate case and substantial amounts of hog replaced. Read into that what you will...personally, I think it was age, rather than the cuprinol, but it doesn't seem to have been a magic bullet...
Almost any finish will need regular refinishing. The advantage of things like sadolin is that you don't have peeling varnish to deal with first.
Rupert

Garry R

Re: Stopping the rot?

Post by Garry R » Mon Jun 23, 2008 10:20 pm

I used clear cuprinol on one of my Merlins when I was restoring it. It is very runny and does soak in well. I used several treatments then went on holiday to let it dry out before varnishing it on my return. I have also used the Ronseal wood hardener as well which I am sure has anti rot properties. At least on varnish finish you can keep an eye on it.

roger
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Joined: Mon Sep 20, 2004 12:08 pm
Location: Frome Somerset UK

Re: Stopping the rot?

Post by roger » Tue Jun 24, 2008 12:38 pm

Garry what Micheal needs to know is does it do what it says on the tin?? :)
Hornet 191 Shoestring,
Hornet 595 Demon awaiting restoration
Hornet 610 Final Fling
Hornet 353

chris
Posts: 2446
Joined: Sat Sep 18, 2004 7:43 pm
Location: somerset

Re: Stopping the rot?

Post by chris » Tue Jun 24, 2008 1:28 pm

http://www.rotdoctor.com/
may give you some food for thought.

A while a go I found quite a bit on the webb about this, especially a Norwegian ( ithink, or possibly Finnish) boatbuilder. So ask google too.

Michael Brigg
Posts: 1662
Joined: Fri Jul 06, 2007 7:11 pm
Location: Gosport, UK

Re: Stopping the rot?

Post by Michael Brigg » Tue Jun 24, 2008 3:53 pm

THis is all great information. I recall "stumbling upon" Rot doctor in the course of browsing. It seems predominantly about effective "bodger repair" of boats that would otherwise be seriously terminal but there are certainly some interesting products and projects in there. Probably some interesting american references in there as well. Things like "Deck damage where a grizzly took a swipe at my fishing punt," and "how to get 'gator teeth out of the hog." Theres some serious perusal to be done.

Actually my real agenda is about finding a suitable primer material for application under varnish that will not discoulor the antique mahogony on oak. My plan is to varnish after an attempt to remove all the old paint and varnish so while I have the wood in a hopefully pristine condition this seems an opportunity to get some serious preventative work done. As I don't anticipate repeating the process for many years I am aware that knocks and scratches will inevitably expose some of the wood from season to season to a certain amount of damp. Additionaly the first bits to be stripped are likely to be exposed for some while and I am concerned that they should not dry out to much while waitng for the new varnish.

However, these primers such as cuprinol do contain a variety of salts so do they discoulor or bleach the wood they treat? If so then perhaps best avoided. I'm asking if anyone has had any problems and what the consensus of opinion is on this subject. Brainstorming really.
Michael Brigg

Garry R

Re: Stopping the rot?

Post by Garry R » Tue Jun 24, 2008 4:32 pm

Re-reading the original post I would suggest that if you don't have the time then the clear Cuprinol may not be the way to go. If it isn't rotten then you shouldn't need to do anything - the G4 sealer and varnish should be fine. If there is rot and you aren't picking it out and replacing then the Ronseal Wood Hardener is fine - does exactly blah blah blah!! I don't like applying it when it is very warm as I think it dries out too quickly and you want it to soak well in. I am certain that it is acetone based from the smell so I think you should be safe to thin it with that and it would penetrate well. Keep following up with repeated coats. It's amazing what the wood will take. Then let it dry well - it really does harden. I then used G4 on the top inside the boat (and nothing else actually). Blakes on the outside of the hull. There have been a few G4 discussions on this Forum in the past but I for one am a fan. Used it on 2 boats now and no problems so far. Either G4 alone or topped off with Blakes DuraGloss.

Rupert
Posts: 6249
Joined: Thu Sep 16, 2004 8:40 pm
Location: Cotswold Water Park

Re: Stopping the rot?

Post by Rupert » Tue Jun 24, 2008 7:32 pm

Or you could use UCP or the like, which soak into the wood very well and are completely clear. Don't forget, though, that much of the "look"of old boats was brought about by the tits in the varnish "bringing out" the colour of the wood.
Rupert

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