Boat finishing layer

Discussion in 'Boatbuilding' started by Chikokishi, Aug 9, 2011.

  1. Chikokishi
    Joined: Mar 2010
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    Location: Montana

    Chikokishi Junior Member

    My girlfriend and I are build a couple of small sailboats (7'8") to sail occasionally. They might be in the water for 2-3 hours every other weekend or so for a couple months, but then it will be winter and they wont touch water for months.

    We are trying to make them as cheap as possible also, so i dont want to fiberglass them. And becuase they are only going to cost like 50$ to build, i would rather not drop another 90$ on some fancy marine grade epoxy.

    Can anyone suggest a cheap solution to keeping the wood and paint safe for the 2-3 hours they are in water? I thought about putting multiple coats of clear coat, or varnish, or something like that.
     
  2. jehardiman
    Joined: Aug 2004
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    Location: Port Orchard, Washington, USA

    jehardiman Senior Member

    Good quality porch paint. Make sure you give it a week or so to dry, but after that it will last for years as long as you keep it from chalking in the sun.
     
  3. Chikokishi
    Joined: Mar 2010
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    Location: Montana

    Chikokishi Junior Member

    Porch paint? Is that what it is called? Iv never heard that before. Ill look for it when i go to town. thanks
     
  4. jehardiman
    Joined: Aug 2004
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    Location: Port Orchard, Washington, USA

    jehardiman Senior Member

    It is used for painting porches...i.e. exterior floors. It is formulated to resist being wet for a limited time (a day or so, not full time immersion) and for hard wear. While not as good as some marine enamels, it is much cheaper and comes in water-based formulations (which is why it needs to throughly dry).
     
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  5. Chikokishi
    Joined: Mar 2010
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    Location: Montana

    Chikokishi Junior Member

    Thanks for the info! This forum is useful. I wish i knew enough to add back to it.
     
  6. CutOnce

    CutOnce Previous Member

    My experience differs a little

    Thinned varnish can be brushed onto plywood to saturate the wood and then dry into a surface penetrating coat before barrier painting with an exterior grade primer and paint. Soaking all edge grains of the plywood before assembly with thinned varnish will let a low cost plywood boat last years more than a boat with just paint.

    Plywood failures generally all start on edges and voids - not flat painted surfaces, so a little prep work on the edges makes all the differences when using cheap materials. Two or three coats of thinned varnish, allowed to cure after cutting and before assembly is the best prep.

    Problem with paint-only is that even exterior grade paints form a barrier layer, but do not penetrate the grain of the wood. Thinned varnish penetrates the grain and makes a huge difference.

    --
    CutOnce
     
  7. Chikokishi
    Joined: Mar 2010
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    Location: Montana

    Chikokishi Junior Member

    When i see boats (like the PDRacer) that have a wood finish, do you think that they used multiple layers of varnish, or perhaps something else? Would varnish eventually build of and become a protective layer?
     
  8. messabout
    Joined: Jan 2006
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    Location: Lakeland Fl USA

    messabout Senior Member

    Use varnish as suggested. Make it thin so that it penetrates the wood. After the impregnation and the varnish is dry, add porch paint as mentioned.

    Varnish as a final coating is not anywhere near as durable as paint, so do not use it for a finish coat.

    The PDR builders are using all sorts of finishing techniques. A the cheap and dirty end, they slap on some house paint and call it good. At the upper end they will be artfully covered with fiberglass and epoxy, then painted to a fare thee well.

    Your boat at three feet wide and eight feet long is going to be pretty tender. You will be much more pleased by making it wider. As an engineering type, you will have no problem with calculating the immersed volumes. It should be apparent that the wider boat will float in shallower water and be much more stable and capable of carrying the 40 odd square feet of sail without causing you to swim frequently.
     
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  9. Chikokishi
    Joined: Mar 2010
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    Location: Montana

    Chikokishi Junior Member

    Messabout:

    Yeah havign a wider boat would make it float higher. today we took the boat out and water tested it, it only sank into the water about half an inch while empty and almost 1.5 inches while we sat in it. The sides at 10" ... so i think we have a good bit of space. =)

    Chiko
     
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