Butt end brightwork anti-fungal treatment?

[Guest]

most of the local canoes I have worked on have had blackened butt ends of thwarts and yokes.

Maybe a water repellent preservative would be a good choice, if only as a first coat, in protecting against mold and fungus

The open grain butt end of thwarts and yokes presents the biggest opportunity for rotted wood. The narrow crevice between the butt ends and edge of the hull is perfect to trap dirt, debris and lingering moisture, hastening bacterial growth at that open grain when the canoe is inverted for storage.

BTW, storing a canoe with wood brightwork outside in proximity to rain splashed dirt is a death sentence for thwarts and yoke. All of the cheap and freebie canoes I have restored have suffered that rotten fate.

I have yet to see a factory canoe with what I considered well sealed yoke or thwart butt ends. That open end grain drinks in sealant, and most manufacturers seem happy to slap on a couple thin coats of varnish and call it good. If that, who is gonna see it, just cut it and stick it in raw.

It isn’t hard to remove the (as yet unwanked) machine screws from a brand new canoe and take out those crosspieces one at a time to inspect and seal.

Don’t be surprised if you find places where a poorly drilled hole barely catches the end of the thwart or yoke. The double hung yoke on a high end Bell tripper had two machine screws that missed the ends all together and two that caught the edge by the scantest fraction of an inch. That boat would have come down on my head toot sweet.

There is no UV exposure on those edges, so I have been sanding off the varnish and coating the butt ends and under-gunwale edge portion of yokes and thwarts with epoxy, but I’m not sure if that is good, keeping moisture (and bacteria) out, or bad, trapping any moisture under an impermeable layer of sealant.

I think good, so far the epoxy sealed ends have held up better over time than scant factory varnish. But some of the canoes I resurrected 10 years ago will need attention soon. The exposed varnish coats mostly, but I’ll be interested to see how the butt ends have faired, and if I only have to yank them out every decade I’ll be happy.

If bacteria and fungus are the butt end’s worst enemies I wonder if some anti-bacterial or anti-fungal treatment wouldn’t be a better first coat soaked in application.

Would epoxy or varnish seal coats adhere after a rot preventive coating of ?????

Or just submerge the last inch of thwarts or yokes in a tub of something for a few days?

 

[yellowcanoe]

I can't answer your last questions. But soaking in something like real spar varnish for a month does preserve dried moose poop for earrings. And each pooplet can be sawn in half to allow mounting of hardware for a pin. You can get these little gems in Gorham NH or Greenville ME. Christmas shopping time. Come on you know your DW would like this http://www.ebaumsworld.com/pictures/moose-poop-jewelry/80624114/

Seriously thwart rot can be sneaky.. One river trip on the upper Androscoggin where we were camping and canoeing we stopped for lunch. One of the Old Town guys fell on his boat knocking all the thwarts and yoke out. All the ends were black, soggy and now not holding anything..

I've noticed the same poorly placed drill holes in some new boats. Its something bearing watching when shopping. And a potential bargaining point if you have the shop to make a new one or fix the old.

 

[Alan Gage]

Would epoxy or varnish seal coats adhere after a rot preventive coating of ?????

Good question. Paint sticks over it so a good chance other finishes will as well.

Alan

 

[Muskrat]

Rot preventing soak of ?????? Polyethylene gycol should soak in and stop the rot. Epoxy should still bond, I don't know about paint or varnish. I used to work with some cross section microscopy guys. They would preserve specimens with PEG and then encase in epoxy before slicing them up.

 

[frozentripper]

Zinc naphthenate is said to be varnishable... clear unlike copper naphthenate which is green.

https://www.homehardware.ca/en/rec/...r-Zinc-Wood-Preservative/_/N-ntltp/R-I1874984

 

[Muskrat]

Disregard my previous post. Talked to my old co-worker, they didn't use polyethylene glycol as an antimicrobial, they used it to control the moisture content in the sample. So, don't use that.

Back to actual preservatives, I actually looked it up this time instead of just from memory. Borax and boric acid in a 60:40 mix is a common treatment. Another is propylene or ethylene gycol, maybe that's why I was thinking polyethylene gycol. Those two are antifreezes and should be the easiest to get. Propylene is the less toxic of the two.

After reading a bunch, all of those treatments are hygoscopic so they'll actually want to retain more moisture in the wood, which doesn't seem ideal since that's what causes the rot in the first place.

Epoxy can be thinned with a little solvent (

 

[Muskrat]

Hmm, for some reason my post got cut short and I can't edit it.

Epoxy can be thinned which would help it soak into the end grain, but will sacrifice some of the epoxy properties.

http://www.westsystem.com/ss/thinning-west-system-epoxy/

I don't have my Gougeon brothers book right now, but in it is a test of epoxy thickness and moisture resistance. A layer of fiberglass and epoxy was much more resistant than several epoxy coats alone, so the best bet would be to use some scrap fiberglass for the thwart ends.

Borate treatment:
http://www.westsystem.com/ss/borate-salt-treats-decayed-wood/

 

[frozentripper]

Some discussion on Wooden Boat Forums, eg....

We have been using zinc naphthenate to treat the bilges in our boats for years. As Frank pointed out, the lack of green color allows us to apply varnish over it.

http://forum.woodenboat.com/showthread.php?5235-Zinc-naphthalate

 

[forest runes]

Years ago there was a great wood preservative called "woodlife" aka. pentaclorophenol , that was clear & you could paint over but alas it caused numerous health problems & lasted forever polluting the environment. But nothing's perfect & hey, we're trying to save thwart ends here after all !

 

[tump_lion]

pine tar...

 

[Muskrat]

Pine tar, turn it black from the get go. Good anti fungal properties. Out of sight out of mind. Brings up a good point, why do we care? What's the big deal of replacing three sticks of wood every 5 or 10 years?

 

[Boatman53]

One usually find out there is a problem when you really need them, because they are out of sight. I epoxy the ends and varnish over when I varnish the thwart. I like the pine tar idea, I think I have some around here someplace.
Jim

 

[MagicPaddler]

Muskrat
Thanks for the link on thinning epoxy. I have thinned epoxy with acetone for years and been told by the sails rep that that was not a good idea but they could not give any particulars as to why not. I found that the acetone slows the setting and improved the wetting. I described it action as stops the setting until the acetone evaporates. I purchased some epoxy thinner and it did not evaporate noticeably. I used the purchased thinner in a vacuum infusion process and did not see it come out of the epoxy during vacuum degassing which the acetone would have. In the information about the thinner it stated the same problems listed in the link you provided.

 

[Mihun09]

Zinc naphthenate is said to be varnishable... clear unlike copper naphthenate which is green.

https://www.homehardware.ca/en/rec/...r-Zinc-Wood-Preservative/_/N-ntltp/R-I1874984

This is what we use on the canvas before applying the filler, I had never considered using it on ends of thwarts/seats etc. It IS end cut preservative after all. Will try it on the present build before applying the new varnish.

Brings up a good point, why do we care? What's the big deal of replacing three sticks of wood every 5 or 10 years?

If not treated it could break at the worst of times. For us restorers it means that in the years to come the original pieces should still be viable as well.