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Thread: Bottom paint recoat with topside?

  1. #1
    Join Date
    Oct 2006
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    Default Bottom paint recoat with topside?

    Hey folks. Sorry, I couldn't find my answer in using the search. If there's a how-to already established please point me to it.

    I have a wood hull, NO fiberglass layer, with what I'm assuming is standard aqua color ablative bottom paint over what seems to be the bare wood (no primer).

    I want to repaint it, but I trailer the boat and it will probably never spend more than a week at a time in the water. I feel like I can get away with just using a topside paint all the way around the exterior hull. (I've bought Rustoleum Topside but could be persuaded to not be so cheap if there's really a good reason to buy something else)

    Should I go ahead with my plan? Do I need to remove the whole bottom paint or can I just sand, wipe, then apply the topside over the remaining bottom paint? Is it okay that there's no prime underneath the existing bottom paint? If the best thing, and easiest, is to just recoat with another ablative bottom paint, I can be persuaded to do that (in black).

    I appreciate the feedback

    Thanks

  2. #2
    Join Date
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    Walney, near Cumbria UK
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    Default Re: Bottom paint recoat with topside?

    As it is an ablative bottom paint with no primer, I would strip to bare wood, and prime with the correct primer for your top coat.
    You are moving from permanently wet and stable to keeping her dry and stable, so you do need an adequate, robust paint film.
    It really is quite difficult to build an ugly wooden boat.

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  3. #3
    Join Date
    Dec 2003
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    Default Re: Bottom paint recoat with topside?

    While removing bottom paint I have applied linseed oil to it so that heat will bubble it up. Any part that doesn't get cooked off loses it's ablative quality from the linseed oil. I think I've always used boiled linseed because it's what I have on hand. The relevance of this to your question is that I applied a drying oil to bottom paint and it hardened. In your position I would scrape and loose paint and test a patch with your chosen paint. If it seems sound, paint it all. If you want the bottom paint to be firmer before coating, try boiled linseed oil and let it set.
    I use Rustoleum Marine on my dinghy that lives outside year round, it is sufficient.

  4. #4
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    Default Re: Bottom paint recoat with topside?

    The old rule of thumb is that any application of paint or resin, no matter how good it is, is only attached as well as the weakest bond underneath it. So, enamel over ablative bottom paint will most likely create ablative enamel, at least to some extent. Sounds like a pretty big risk just to get out of doing the job the way you probably know it really should be done. Good luck.

  5. #5
    Join Date
    Mar 2007
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    East Quogue,NY
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    Default

    +1

    And use precaution scraping and sanding antifouling paint. It is poison, after all. A respirator and eye protection are called for if mechanically removing. There are chemical strippers that will remove at least most of it, without generation of any dust or chips.

    Kevin


    Sent from my iPhone using Tapatalk Pro
    There are two kinds of boaters: those who have run aground, and those who lie about it.

  6. #6
    Join Date
    Oct 2006
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    16

    Default Re: Bottom paint recoat with topside?

    Was it a mistake for the person to not prime under the ablative paint? ...if I decide to take the easy route and just go over with another ablative paint.

  7. #7
    Join Date
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    Default

    What does it look like? If the current coating looks ok and has been on for a while, you are probably OK.

    Kevin


    Sent from my iPhone using Tapatalk Pro
    There are two kinds of boaters: those who have run aground, and those who lie about it.

  8. #8
    Join Date
    Dec 2003
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    Sound Beach, NY
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    Default Re: Bottom paint recoat with topside?

    My recollection is that primer for bottom paint is bottom paint. I've been wooding my boat gradually, and just apply the bottom paint on wood.

  9. #9
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    Portland, Oregon
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    Default Re: Bottom paint recoat with topside?

    Quote Originally Posted by Todd Bradshaw View Post
    The old rule of thumb is that any application of paint or resin, no matter how good it is, is only attached as well as the weakest bond underneath it. So, enamel over ablative bottom paint will most likely create ablative enamel, at least to some extent. Sounds like a pretty big risk just to get out of doing the job the way you probably know it really should be done. Good luck.
    This.

    And, in addition, the days are gone when all paints used a basic, standard, formulation and interactions were widely understood. These days, topcoats are more highly engineered, and it becomes ever more important to match all components. By applying the Rustoleum over an unknown bottom paint... you'd be courting failure.
    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)

  10. #10
    Join Date
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    Default Re: Bottom paint recoat with topside?

    How big a boat are we talking about? Assuming that it’s larger than a couple of people could hand-carry, I’d say stick with bottom paint on the bottom. Yes you could go to the trouble of stripping it all back and painting with topside paint but it’s not the right stuff for the job so you would be spending a significant effort for no gain beyond a minuscule savings in paint costs. There was just another person posting here a few days ago with exactly the opposite problem. They were buying a trailered boat with a bottom painted with topside paint and they wanted to store it in the water and they were contemplating the project to strip off all the topside paint and start over with bottom paint. So I suggest that you a save yourself or some future owner the hassle and go with proper bottom paint.
    - Chris

    Life is short. Go boating now!

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