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Thread: Paint over a splined douglas fir deck

  1. #1
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    Default Paint over a splined douglas fir deck

    I have an aft deck on my 45 year old lobster boat that was built with 2x6 douglas fir over oak frames. It is splined and very tight and was painted when I bought the boat 5 years ago. The paint was ugly, a classic New England tan color that had faded to a weird looking salmon pink color. It was mostly sound other than the color so I had the yard sand it, not to bare wood, just to sound paint and put some two part Epifanes over top of it. It has held up pretty well other than some bubbles here and there and some annoying cracks in the paint at some of the seams. Most of the seams look good. It is very dry underneath with good airflow. So my question is what to do about the occasional cracks and bubbles. I have opened up a few of the bubbles by cutting them open and peeling the paint right off by hand. The paint comes up in a thick skin leaving a dark wet wood surface which is easily sanded to clean dry wood. My thinking is that the paint is just too thick and old to breathe and adhere well to the paint so my current plan is to sand the entire surface down to fresh wood, coat with a two part primer and follow with a two part paint. My hope is that this will stick well to the dry wood and flex enough to deal with the splined joints and keep any water from getting into the wood.

    Any thoughts?2012 old paint.jpg2015 three year old paint.jpg2015 new paint.jpg

  2. #2
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    Default Re: Paint over a splined douglas fir deck

    You'll get as many strategies as there are replies. Here's mine.

    It looks like water got under that 1/4 round and soaked into the end grain, so if it's still there I would remove it before stripping to bare wood. Once the fir has dried as well as possible, and I wouldn't be afraid to apply heat from below for a while, I would saturate with CPES. Many here will tell you that CPES contains so many solvents that once those solvents evaporate it's not a very good sealer after all, that it's nothing more than a somewhat honey-combed substance, and I expect that they're correct, but that's 1/2 of what makes it such an excellent primer. The epoxy that remains is very well bonded to the wood, it's epoxy, the other half of how it works so well as a primer, but since it's somewhat porous the paint will form a mechanical bond as well as an adhesive bond.

    Once the CPES has had a week or so to completely cure, and it does take a while to stop off-gassing, I would work Sika 291 into the joints as deeply as possible, first with a fine hole in the tip of the caulking tube, then with a putty knife held flat, thereby forcing it a bit deeper. You should mask the seams so as not to fill the honeycombed surface with caulk.

    Once that has cured for a few days sand with a random orbit sander, vacuum clean, then apply thinned paint with a brush, so you can work it into the honeycombing. The more you force it in the better. Don't use a rag with paint thinner to clean up, it will push dust into the pores, just vacuum well, using the brush attachment. Compressed air will do the job well too.

    If that 1/4 round has to go back make sure to bed it in the 291, and before that when you're applying the CPES just pour it into the end grain that the 1/4 round covers. The solvents in it will soak a ways into the end grain and kill any fungus that's there, and slobber paint in behind it when you paint, then fill any remaining gap with 291.

    That's a nice boat. Can I have it when you die?

  3. #3
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    Default Re: Paint over a splined douglas fir deck

    I think Gib pretty much nailed it. I would only add that Id seal and backprime the 1/4 round before you install it.
    Keep slathering the CPES into the endgrain until it wont take any more.
    Nice boat.

  4. #4
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    Default Re: Paint over a splined douglas fir deck

    I think using the right paint is important.
    Wouldn't something old school and flexible like Kirby's be in order here?
    A hard paint may just crack again.

  5. #5
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    Default Re: Paint over a splined douglas fir deck

    canvas?

  6. #6
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    Default Re: Paint over a splined douglas fir deck

    Quote Originally Posted by timo4352 View Post
    I think using the right paint is important.
    Wouldn't something old school and flexible like Kirby's be in order here?
    A hard paint may just crack again.
    Here is the crux.

    The yard should have advised you that a tough, but very inflexible, film finish - like a 2-part polyurethane - is inappropriate over timber. Douglas fir is not the worst for movement in use, but neither is it the best.

    Nothing wrong with the scenario Gib paints. But it doesn't address the core issue. Until you remove that hard, rigid, film, and replace it with something more flexible (a long-oil, oil-based enamel formulation would be my recommendation)... this issue will not go away. Once you've stripped off the paint, using the GibPrescription will add suspender to your belt and garters.
    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)

  7. #7
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    Default Re: Paint over a splined douglas fir deck

    My other thought was truck bed liner. Not pretty enough for most though, especially on that beauty.

    I used a spray can of truck bed liner in the bottom of my dory this last summer. Except that the solvents in it were absolutely incompatible with any paint residue that I hadn't thoroughly removed I was quite pleased with it's durability and non-skid quality over glass in epoxy over plywood. It just foams up any paint that it goes over, the substrate must be very clean. I don't know how it would do over CPES or Sika and it might crack at the seams, but for anyone considering trying it over fresh clean plywood or glass in epoxy I say just go for it.

  8. #8
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    Default Re: Paint over a splined douglas fir deck

    Many thanks to all who offered some fairly uniform advice. I agree that there is likely some moisture getting under that quarter round and it will be pulled up and ends and surfaces well sealed before being reinstalled with a good slather of 291. All of the existing paint will be removed down to bare wood, primed with Epifanes Werdol Woodprimer and painted with Epifanes Yacht Enamel so that it matches the existing Epifanes two part paint on the other surfaces. That should allow it to breathe and flex more than the two part paint and it should be easier to maintain, just may need a coat more often than the two part stuff that is holding up well on the other surfaces. The two part has held up well on the MDO plywood deck over the engine and on the side decks, wash deck and cabin roofs. I plan to skip the CPES epoxy sealer, I have used it successfully before but the smell is too much to handle while the boat is in the shop for the winter.

  9. #9
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    Default Re: Paint over a splined douglas fir deck

    I think using the right paint is important.
    Wouldn't something old school and flexible like Kirby's be in order here?
    A hard paint may just crack again.
    I'm a dyed-in-the-wool traditionalist, so I'd skip the CPES and just use Kirby's. Or 'Phanes; I haven't ever heard anything bad about them other than the chronic financial shock users seem prone to. (I use 'Phanes varnish exclusively.)

    I don't use CPES and in 39 years haven't had any trouble. But David G pegged the fundamental problem:

    The yard should have advised you that a tough, but very inflexible, film finish - like a 2-part polyurethane - is inappropriate over timber.
    And whatever paint or paint/CPES combo you use, don't skimp on sanding. Even the perfect paint won't stick if it doesn't have a properly prepared surface.

    Alex

  10. #10
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    Default Re: Paint over a splined douglas fir deck

    My own take is also to skip the CPES and dry scrape the old paint off using heat. Stay out of the rain till the job is done! Once the wood is bare and dry you can do a light sanding just to smooth it. Then apply your favorite color of Kirby's that is thinned so as to soak in. Keep applying the oil based paint until you have sufficient build up and Bob's your uncle. Letting the paint be its own primer takes longer but prevents water intrusion and blistering.
    Jay

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