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Thread: Hull paint recommendation needed

  1. #1
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    Default Hull paint recommendation needed

    I am new to the forum and am very impressed with the knowledge and subsequent advice provided by members and hope that my request will also find a solution. Searches of the forums have revealed numerous threads associated with painting, however for the most part are associated with anti fouling coatings or topside paints only.

    I am seeking a recommendation for a paint suitable for application below the water line on a small wooden dinghy (Oughtred Puffin).


    The dinghy is trailered and only remains in the water for a few hours during weekend sailing before a hose off and storage.

    A single pack polyurethane system was recommended by International during the build some eight years ago (knowing that it was to be applied below the waterline). The coating has stood up well on the interior of the boat and the hull above the waterline but is looking shabby below showing signs of general degradation and cracking. As indicated elsewhere in the forums I am sure the cracking is caused by the application of an inflexible coating applied to a flexible substrate. To reduce the amount of work, I was considering repainting the hull below the waterline only, however inspection revealed that the degraded coating extends to the plank immediately above the actual waterline.

    I was intending to do some overnights stopovers in the boat and assume that this would only add to the problem. I don't see any merit in repainting the hull with a similar coating (Toplac recommended by International) or similar. I would assume that the preparation may include sanding the existing top coat (back to the undercoat if necessary) before re-application.

    In view of the limited time in the water, the use of an antifouling product is also not particularly attractive.

    I reside on the Sunshine Coast in Queensland Australia and would greatly appreciate any assistance with regards to paint products that are likely to be available locally and that can be applied effectively with a roller and tip off method.

  2. #2
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    Default Re: Hull paint recommendation needed

    'Below the waterline' means nothing for a boat that doesn't spend long periods in the water.

    All the normal choices are open to you, including 1-part polyurethane.

    Hard to imagine that immersion is your problem. I'd be looking elsewhere. For instance - it is quite common for a trailer for such a light boat to be too harshly sprung, Intended for similar length, but much heavier, fiberglass boats. Which could be abusing your bottom. Or... another common issue is that people don't follow the prep instructions precisely. Many paint systems these days - like the polyurethanes - are far more 'highly engineered' products and less forgiving than the older long-oil enamels.
    Last edited by David G; 04-12-2021 at 01:05 AM.
    David G
    Harbor Woodworks
    https://www.facebook.com/HarborWoodworks/

    "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)

  3. #3
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    Default Re: Hull paint recommendation needed

    I used International Marine Coat Classic Enamel on my TS16 for years without any problem. I've also used Norglass Premium Enamel but I can’t say that I’ve seen how well it held up long term in the water.

    You could always go for a two pack but you’d have to strip the single pack off to apply it.
    Larks

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  4. #4
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    Default Re: Hull paint recommendation needed

    I agree with David G. I do a lot of small boats. A one part poly should be fine. Interlux brightside, Epifanes, Prep is everything. Sanding well and priming if you can. color match? one plank up, should still look fine. Dave. www.sattersrestoration.com

  5. #5
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    Default Re: Hull paint recommendation needed

    Thanks Larks, I think I will stay clear of the two pack systems. I will do a bit of research into the other systems suggested.

  6. #6
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    Default Re: Hull paint recommendation needed

    Thanks David G
    I agree that trailering could be the cause of the cracking. It may also be caused by my weight in the boat. The boat is fitted with floors and floor planks but some flexing is still likely to be occurring, it is a light boat after all. There is not much that can been done other than to use a flexible coating I would suggest.
    As you say, I would also expect any reasonable coating to handle the short term immersion but it does seem odd that the problem only occurs below the waterline.
    I am waiting for feedback from Jotun about their Easygloss coating.

  7. #7
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    Default Re: Hull paint recommendation needed

    Thanks for the feedback David Satter. Do you consider it necessary to apply a primer after sanding the existing single pack coating?

  8. #8
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    Default Re: Hull paint recommendation needed

    Not to disparage your painting skills, but if you were painting directly on to bare wood and if the paint system (primer and topcoats) that you used hadn’t been heavily enough applied first up you may be getting a saturation of the timber when she’s wet, causing it to expand and contract a lot more than the paint can cope with and so to crack the paint......

    My TS16 was a ply hull and had been epoxy coated under the paint system so if your Puffin was painted directly over wood my experience with it may not suit your application.
    Larks

    “It’s impossible”, said pride.
    “It’s risky”, said experience.
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  9. #9
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    Default Re: Hull paint recommendation needed

    I can't comment without inspecting it. Priming would depend on how much paint is there and how much you sand and how much time you have. but like Larks said if it's just bare wood under, I'd think about priming. Wish I could give you an exact answer. You'll get lots of good advise here. Dave

  10. #10
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    Default Re: Hull paint recommendation needed

    Larks you are correct, during the build I applied a paint system consisting of primer, undercoat and topcoats direct to the plywood in accordance with the Interlux system data sheets as far as I am aware. I can't be sure of the film thicknesses achieved during application but at least one of the coatings was fairly heavily sanded and I can't recall if a further coat was applied prior to top coating. I feel that your assessment regarding the coating thickness is likely to be correct and would explain why a proven system would break down as it has and only below the water line. I don't know if I can justify stripping the hull and applying an epoxy coating but I will certainly give it some thought.
    It would seem that the hull will need to be stripped to remove the cracked topcoat in any case, so an extra coating is hardly going to be a problem. I can't wait I love sanding.
    I thank everyone for your generous assistance.

  11. #11
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    Default Re: Hull paint recommendation needed

    I am looking for a shortcut now. Is it feasible to apply an epoxy coating to the existing single pack polyurethane (to avoid the stripping)?

  12. #12
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    Default Re: Hull paint recommendation needed

    Quote Originally Posted by Island Pointer View Post
    I am looking for a shortcut now. Is it feasible to apply an epoxy coating to the existing single pack polyurethane (to avoid the stripping)?
    No, it’d be a waste of epoxy. It’s not a big hull but I suggest strip the paint first with a heat gun and scraper and then sand the timber, you might be surprised how therapeutic stripping paint with a heat gun can be... (I say “might” - it works for me )
    Larks

    “It’s impossible”, said pride.
    “It’s risky”, said experience.
    “It’s pointless”, said reason.
    “Give it a try”, whispered the heart.

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  13. #13
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    Default Re: Hull paint recommendation needed

    Thanks again Larks. If I opt for stripping the paint, do you consider one coat of thinned epoxy and one coat of full epoxy to be adequate? Followed by a wash down and sanding before priming and top coating?

  14. #14
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    Default Re: Hull paint recommendation needed

    Quote Originally Posted by Island Pointer View Post
    Thanks again Larks. If I opt for stripping the paint, do you consider one coat of thinned epoxy and one coat of full epoxy to be adequate? Followed by a wash down and sanding before priming and top coating?
    Sounds good - though if you are going to go with an epoxy coat I wouldn’t thin the first coat. Also if you find areas that you want to fill and fair after epoxying and before painting you can use something like Jotun Jotafair - it’s easy to use and easier to sand and get a nice smooth finish on than epoxy with fairing fillers in it.
    Larks

    “It’s impossible”, said pride.
    “It’s risky”, said experience.
    “It’s pointless”, said reason.
    “Give it a try”, whispered the heart.

    LPBC Beneficiary

    "Keep away from people who try to belittle your ambitions. Small people always do that, but the really great make you feel that you, too, can become great!"

  15. #15
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    Default Re: Hull paint recommendation needed

    I have been off the air for a while. Also waiting for feedback from International and Jotun.
    It has all become a bit difficult and as a result I have decided to start sanding the affected areas of the hull and see what I find.
    Contrary to the recommendations by Jotun and International, I believe that I will simply sand back, prime and recoat with a similar one pack top coat. If the paint blisters due to immersion I will simply have to start the process again. Thanks again for all the assistance provided.

  16. #16
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    Default Re: Hull paint recommendation needed

    If you hate sanding, use a 2 part epoxy barrier coat that is made for "painting" on, not resin. Resin drips and waves.
    Interlux 2000 in the states.
    It does not need any top coat. Why make the bottom of a boat shiny ?

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