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Thread: Caulking, again!

  1. #1
    Join Date
    Nov 2019
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    Port Renfrew, BC, Canada
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    3

    Default Caulking, again!

    Can't find any recent threads and things change, if there is a relevant thread point me at it. My boat is 35ft, solidly built in UK in 1972, Iroko planks on rock elm. After a very rough Atlantic crossing she started leaking and has now been laid up ashore through the pandemic so I am planing to recaulk completely below the waterline before she goes back in. My main question is what do others use to prime the wood? Everything I can find available is listed as for 'above waterline' unless it is an epoxy. I suspect this is manufacturers assuming boats are only made of fiberglass. It the past I have use oil based aluminum primer designed for exterior house paints and not had a problem but since I am doing the whole boat wondering if there is something better. (will be using cotton caulking and Interlux brown seam compound).
    As a 'side' question I am wondering how often boats usually need recaulking, mine is still the original so 50 years old.

  2. #2
    Join Date
    Feb 2017
    Location
    Seattle, W.A., U.S.A
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    306

    Default Re: Caulking, again!

    Professionally speaking, I would be hesitant to do a complete recaulk, she likely doesn't need it, and unless you know what your doing you may well do more harm then good. I'm also unclear what you mean in terms of priming the wood? I assume you mean what paint do you put over the driven cotton, in which case I recommend using whatever bottom paint is at hand for below the waterline, and the topside primer of your choice above.

    Nicholas

  3. #3
    Join Date
    Oct 2009
    Location
    South Puget Sound/summer Eastern carib./winter
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    22,236

    Default Re: Caulking, again!

    Yea, if you are asking these questions, it says you best hire it out maybe?

  4. #4
    Join Date
    Jan 2011
    Location
    Norwalk CT
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    2,799

    Default Re: Caulking, again!

    What Bruce said.

    If you're going to use Interlux caulk, I'd talk to their tech folks about what they recommend.

  5. #5
    Join Date
    Apr 2019
    Location
    Massachusetts
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    2,226

    Default Re: Caulking, again!

    Last time I did it I used the old standard: Kirby's Red lead

  6. #6

    Default Re: Caulking, again!

    Quote Originally Posted by Boatbum View Post
    Last time I did it I used the old standard: Kirby's Red lead

  7. #7
    Join Date
    Jan 2016
    Location
    Auckland New Zealand
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    213

    Default Re: Caulking, again!

    Talking of red lead mixing starts around 28 minutes.

  8. #8
    Join Date
    Feb 2017
    Location
    Seattle, W.A., U.S.A
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    306

    Default Re: Caulking, again!

    I debated mentioning this for a while, but y'all do know that modern red lead is just iron oxide right? And that further, lead does not help kill fungal life. I'm aware that it has been the traditional choice for centuries, but the science doesn't back it up. What the science and several hundred years of experience do support is that lead primer will help kill your shipwright. Lead has places on wooden boats, but its not in paint, and its not necessary for priming caulked seams.

    Nicholas

  9. #9
    Join Date
    Apr 2019
    Location
    Massachusetts
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    2,226

    Default Re: Caulking, again!

    Quote Originally Posted by Pelirrojo View Post
    I debated mentioning this for a while, but y'all do know that modern red lead is just iron oxide right? And that further, lead does not help kill fungal life. I'm aware that it has been the traditional choice for centuries, but the science doesn't back it up. What the science and several hundred years of experience do support is that lead primer will help kill your shipwright. Lead has places on wooden boats, but its not in paint, and its not necessary for priming caulked seams.

    Nicholas

    Not sure if I understand what you are saying here. You are saying red lead only has Iron Oxide (rust)? It might have iron oxide, but it definitely has lead. From the Kirby Paint website:
    WARNING! This product contains LEAD!
    As for its effectiveness. Everything I read is that it is a great primer. It binds better to bare wood and is more waterproof. If it didn't have a nasty tendency to kill people it would still be in use extensively.
    Last edited by Boatbum; 09-15-2022 at 02:50 PM.

  10. #10
    Join Date
    Feb 2017
    Location
    Seattle, W.A., U.S.A
    Posts
    306

    Default Re: Caulking, again!

    Apologies for my inaccuracy in the led content of the Kirby’s. Many of the other modern red lead primers do not contain lead. And yes, lead does help make an excellent primer, it is also does have a nasty tendency to kill folks, it doesn’t help help much with killing fungus. People are welcome to use the toxins they choose on their own vessels, just please be aware that the continued insistence on unnecessarily toxic products is part of what drives the costs of wooden boat ownership up. I am a working shipwright and am happy to use the products that are best for the boat. I also am unwilling to die for my costumers vessels and will pass along the costs of my PPE to them. In the particular case of lead based primers they are not better for the boat, but they are much worse for me. Thus, the client gets to bear the extra cost, and I get to enjoy working in a respirator.

    Peter, I honestly cannot think of a single time I have ever sanded a bullet, would you also argue that silica dust is harmless because you have never fallen in your driveway?

    Nicholas

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