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Thread: Gunwale repair

  1. #1
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    Default Gunwale repair

    Hi,

    I ask for advise. On my dinghy I have made (external) gunwale from beech, which I guess is not most "marine" wood. Three layers of 10 mm planks have been glued with West system epoxy, epoxy coated and vanished to or three times. Everything was OK until last September, when boat was under tent and rain was pouring (literally) every single day.
    After removing the tent I have found that at some places vanish and epoxy have sliced off, beech has darkened (got fungus?).

    IMG_3093.jpg22664269_846537012181186_401936589_o.jpg
    So, what to do - to repair and to prevent such failures in future:
    Make external gunwale layer from redwood soaked in linseed oil?
    Put a rope around outside of gunwale for ventilation?
    Put more layers of vanish?
    Get rid of epoxy on gunwale at all?

    Best regards,

    Jonas

  2. #2
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    Default Re: Gunwale repair

    First: beautiful work, but beech is a bad choice. That is fungus, and you can hope to get ahead of it, but replacement is a better long-term fix. Redwood is not a bad idea, but on the outer side of a gunwale, know that while it's very flexible and rot resistant, it's very easily dented. Gun'ls take a lot of abuse. There are better choices to consider. Also, before next winter, consider how to better ventilate your tent. The rot appears to be happening where the tent rests against the boat. Air circulation and the avoidance of standing fresh water are critical.

  3. #3
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    Default Re: Gunwale repair

    I think your varnish is a bit thin and perhaps a bump against a hard surface caused it to be cracked or abraded. Not to worry! I would use a card scraper to take the area down to bare wood. The card scraper is the easiest tool to control for delicate work. If you are not familiar with them, here is a reference: https://en.wikipedia.org/wiki/Card_scraper
    You may also need to use a bit of hot oxalic acid to remove the fungus stain from the wood grain, if the scraping does not clean it up.
    All that is left then is a proper sanding and more varnish. Be sure to rinse off the acid as it can cause the varnish to remain sticky and not fully Harden up.
    Good luck!
    Jay

  4. #4
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    Default Re: Gunwale repair

    Thank you for advises.
    Shall vanish be on wood or epoxy priming?
    Jonas

  5. #5
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    Default Re: Gunwale repair

    Varnish does not need priming other than a first coat that is thinned a bit with turpentine. This is to allow a better bond for subsquent coats.
    Priming with epoxy can allow moisture to intrude under the epoxy film and cause staining. These are stains can be difficult if not impossible to remove.
    Jay

  6. #6
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    Default Re: Gunwale repair

    Once you are done repairing the rail I think you should figure out a way to keep the cover from chafing through the finish or you'll be back it again next year.
    Steve

    Boats, like whiskey, are all good.
    R.D Culler

  7. #7
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    Default Re: Gunwale repair

    Quote Originally Posted by Jay Greer View Post
    I think your varnish is a bit thin and perhaps a bump against a hard surface caused it to be cracked or abraded. Not to worry! I would use a card scraper to take the area down to bare wood. The card scraper is the easiest tool to control for delicate work. If you are not familiar with them, here is a reference: https://en.wikipedia.org/wiki/Card_scraper
    You may also need to use a bit of hot oxalic acid to remove the fungus stain from the wood grain, if the scraping does not clean it up.
    All that is left then is a proper sanding and more varnish. Be sure to rinse off the acid as it can cause the varnish to remain sticky and not fully Harden up.
    Good luck!
    Jay
    I have used oxalic acid but never been that satisfied. When you say hot oxalic acid how hot?

  8. #8
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    Default Re: Gunwale repair

    Quote Originally Posted by stromborg View Post
    Once you are done repairing the rail I think you should figure out a way to keep the cover from chafing through the finish or you'll be back it again next year.
    That's easier said than done. May it be something like this:

    Jonas

  9. #9
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    Default Re: Gunwale repair

    Three coats is never enough. Eight coats is the usual recommendation.
    It really is quite difficult to build an ugly wooden boat.

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  10. #10
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    Default Re: Gunwale repair

    What Jay said, with one small addition.

    After the scraping and bleaching have removed the visual traces of the mold - the infestation still like entends further into the wood than you'd expect. For that reason - just before you kiss the area for the last time with abrasive or scraper... in preparation for thinned varnish... I'd give a soak with borax in water, then let it dry. This treatment will get deeper, and be more toxic to existing mold and preventative against future outbreaks, than anything else easy. And it won't interfere with color, or finish adhesion.

    Yes... more coats of varnish. And you can create a soft spot on your cover - instead of on your boat - if you like, by using self-adhesive velcro strips to attach some softer fabric in the areas where you've now discovered chafing is likely. But there are several routes to protecting your varnish from chafe. That's just the first that occurred to me.
    David G
    Harbor Woodworks
    http://www.harborwoodworking.com/boat.html

    "It was a Sunday morning and Goddard gave thanks that there were still places where one could worship in temples not made by human hands." -- L. F. Herreshoff (The Compleat Cruiser)

  11. #11
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    Default Re: Gunwale repair

    Quote Originally Posted by tink View Post
    I have used oxalic acid but never been that satisfied. When you say hot oxalic acid how hot?
    Boil some water, put same in a glass container and add the acid crystals till the water will absorb no more into solution. Apply it hot with a brush. Yes and if it is a sunny day, so much the better. If at first it does not bleach, add another treatment. Protect your eyes, skin and lungs!! Wear at least a painting mask.
    Jay
    Last edited by Jay Greer; 02-01-2018 at 07:28 PM.

  12. #12
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    Default Re: Gunwale repair

    In addition to chafe, that cover may be keeping the gunwale wet. If the cover doesn't breathe, it will accumulate condensation on the inside. That will keep the boat wet wherever it touches.

  13. #13
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    Default Re: Gunwale repair

    Quote Originally Posted by johngsandusky View Post
    In addition to chafe, that cover may be keeping the gunwale wet. If the cover doesn't breathe, it will accumulate condensation on the inside. That will keep the boat wet wherever it touches.
    I believe this was the reason in addition to thin coat of vanish. What type of vanish is best to use? Brands may differ between countries.
    Jonas

  14. #14
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    Default Re: Gunwale repair

    Has anyone tried "Bar Keepers Friend" (a soft kitchen cleanser containing oxalic acid) for removing fungus from wood?

  15. #15
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    Default Re: Gunwale repair

    Quote Originally Posted by spirit View Post
    Has anyone tried "Bar Keepers Friend" (a soft kitchen cleanser containing oxalic acid) for removing fungus from wood?
    You want both the oxaclic acid and the borax solutions to be as 'wet' (low viscosity) as possible - for maximum penetration.
    David G
    Harbor Woodworks
    http://www.harborwoodworking.com/boat.html

    "It was a Sunday morning and Goddard gave thanks that there were still places where one could worship in temples not made by human hands." -- L. F. Herreshoff (The Compleat Cruiser)

  16. #16
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    Default Re: Gunwale repair

    Quote Originally Posted by Jay Greer View Post
    Varnish does not need priming other than a first coat that is thinned a bit with turpentine. This is to allow a better bond for subsquent coats.
    Priming with epoxy can allow moisture to intrude under the epoxy film and cause staining. These are stains can be difficult if not impossible to remove.
    Jay
    I believe that Jay is talking about traditional varnish and not polyurethane varnish. It has been my experience that polyurethane varnish tends to dry very slowly and softer if there is any turpentine on a paint brush. The PU varnish eventually hardens, but it is weeks to months before it is as hard as it should be. I would not thin polyurethane varnish with turpentine. Turpentine is a great brush cleaner for PU varnish.

    It may be that I only used a brush that was just cleaned with turpentine with Varathane PU varnish and possibly Minwax Spar urethane. Varathane isn't a good choice here. Minwax is better than Varathane, but you won't find a lot of fans for either of them here.

    Hopefully Jay will shed some light on this. What I ran into may be specific to the brand of PU that I was using at the time.
    Management is the art of counting beans. Leadership is the art of making every being count. --Joe Finch

  17. #17
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    Default Re: Gunwale repair

    You are correct, I prefer to use traditional oil based varnish rather than polyurethane. I find that the amber cast that oil based varnish imparts is both pleasing to the eye and provides better UV protection from sun bleaching of the wood.
    Jay

  18. #18
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    Default Re: Gunwale repair

    Thank you for all advises. This is a very useful forum.
    Jonas

  19. #19
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    Default Re: Gunwale repair



    As previously stated, you need better ventilation. I'm not sure a rope rubrail is the answer, although I do like the looks of it on the example you posted. A couple of tent poles set diagonally into pockets on the inside might be enough to keep the material away from the sides. A few cross members at gunwale height might work for the time being.

  20. #20
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    Default Re: Gunwale repair

    Thank you!

  21. #21
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    Default Re: Gunwale repair

    You're welcome. Let her breathe!

  22. #22
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    Default Re: Gunwale repair

    It's varnish. It always looks like that

  23. #23
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    Default Re: Gunwale repair

    Hello,
    I have tried soaking with boric acid solution and borax solution. The boric acid solubility depends more on the temperature than borax solubility. Below is the picture after (probably) 5th attempt. The look is much better than in the beginning, but still some stains are seen (especially after wetting). I do not expect much better look with more "boric" attempts. Still another option is to use chlorine base bleaches, but I have a feeling that these can remove color of wood and make it weaker.
    Regards,
    Jonas
    IMG_3601.JPG

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