sealing wood

Discussion in 'Boatbuilding' started by computeruler, Aug 7, 2008.

  1. computeruler
    Joined: Aug 2008
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    computeruler Junior Member

    i wanna build a cheap boat out of plywood but i cant afford marine grade plywood or firberglass cloth so i want to know whats the best way to seal it and make it water proof other then that
     
  2. BHOFM
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    BHOFM Senior Member

    Porch and floor paint! Lots of it!
     
  3. duluthboats
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    duluthboats Senior Dreamer

    The importance of marine grade plywood has more to do with strength and uniformity than its resistance to water. It is often necessary to fiberglass with epoxy, cheap plywood to make up for its deficiency.

    Gary
     
  4. BHOFM
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    BHOFM Senior Member

    Lumber yard plywood has voids that can get water in them
    and cause all the problems!

    however, if you just want a cheap boat, build it and paint
    the crap out of it and it will last a few years if not left
    in the water for long periods of time!

    I have built many weekend project boats and had them in
    the water the next weekend and they lasted longer than
    we thought they would and all they had was 3 or 4 coats of
    good old porch and floor paint! Inside and out! Sealing the
    edges of the ply is very important, we used tigerhair body
    filler most of the time!

    If you want a boat for a life time of enjoyment, do not
    read the above statement!
     
  5. alan white
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    alan white Senior Member

    Paint each part before assembly, three coats porch and deck enamal, use a polyurethane or polysulfide caulk on all faying surfaces, fill all edge gaps with same, and maintain, maintain, maintain. You'll get some decent mileage out of it.
     
  6. Trevlyns
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    Trevlyns Senior Citizen/Member

    Have a look at this thread and read up a bit on ethylene glycol.
     
  7. eponodyne
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    eponodyne Senior Member

    1/4" birch underlayment ply is very low void and is glued with waterproof glue (for use in bathrooms). I make kiteboards out of the stuff. It is not at all rot-resistant so sealing is a given, but also a no-brainer.

    MDO is also available, but I don't know how many thickness options there are. Many boatbuilders are using MDO to good advantage; the paper facing takes either glue or paint uncommonly well.

    Ethylene glycol is one option; borax is another, just as effective, probably cheaper. Simply dissolve borax crystals in hot water until it will take no more (saturated solution) and swab on the surface needing protection. Rot fungus spores will not be able to live in this environment.
     
  8. PAR
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    PAR Yacht Designer/Builder

    Anti freeze (ethylene glycol) isn't especially effective, because the glue lines don't permit much penetration into the interior veneers.

    MDO comes in 3/8", 1/2" and 3/4" (maybe 1" too), but lacks the veneer count to be particular strong, though it is long lived and easily paintable.

    The low buck route is paint and care. If you keep it dry, covered and out of the direct sun ashore, then you'll get some service out of the puppy.
     
  9. computeruler
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    computeruler Junior Member

    so for the borax do i put that on before or after i paint
     
  10. computeruler
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    computeruler Junior Member

    so hows this sound first use some anti freeze stuff or borax? which is better? and then use this everdure and paint?? should that give me good results?
     
  11. Trevlyns
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    Trevlyns Senior Citizen/Member

    Here's another useful publication which should help you

    Best!
     

    Attached Files:

  12. computeruler
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    computeruler Junior Member

    thanks so was what i put good? should i use borax or antifreeze first? then uverdure and then paint it?
     
  13. computeruler
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    computeruler Junior Member

    or what about using some sheetmetal? would that be even better?
     
  14. rwatson
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    rwatson Senior Member

    Sheetmetal by itself or over the wood ?
     

  15. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Good construction techniques, good material selections, full ventilation of all enclosed spaces and keeping the boat clean will do as much for the life of the wood as any topical wood preservative.

    As a rule, preservatives (regardless of what they might be) are applied to raw wood only.

    You can try a home made brew if you want. It's your money and boat. If in a few years you notice rot or other issues, then how much have you saved by using a home mixed concoction.

    Sheet metal over the wood will work fine, IF you can guarantee moisture can't get between the metal and wood. This will likely involve epoxy and vacuum bagging the sheet metal down during the cure. Of course you'll then have to contend with the metal corroding, which will lift it free of the wood and the problems begin, not to mention the weight it will add to the boat.

    Use the best materials you can afford, then take good care of it and you'll get the best service your material choices will permit.
     
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