Epoxy coating strip planks and other material

Discussion in 'Boat Design' started by Cmw505, Sep 9, 2019.

  1. Cmw505
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    Cmw505 Junior Member

    pretty self explanatory. just curious what effect would this have?. logic would say that epoxy would block the wood from swelling. effects on epoxy coating metal?.
     
  2. Deering
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    Deering Senior Member

    Correct. Fully encapsulated wood strips will not contact the water so will not swell. Standard resin/hardener (like West System) won’t cause any appreciable swelling.

    Metal is a more complex question do to the widely varying properties of different metals that affect adhesion of coatings. Surface preparation also has a large role. In general, if you wish to epoxy coat metals it’s best to find a specific flavor of coating designed for the metal you’re considering.
     
  3. Cmw505
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    Cmw505 Junior Member

    thanks for the reply!.
     
  4. Eric ruttan
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    Eric ruttan Junior Member

    as epoxy is a fluid, absorbed by wood, how can it not swell said wood?
    Does it harden too fast to actually penetrate much?
     
  5. Blueknarr
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    Blueknarr Senior Member

    Epoxy simply doesn't penetrate far enough to significantly change the wood's dimensions. There is likely to be some surface fibers raised by swelling, but not much else.

    Epoxy's benefit is as an encapsulation barrier. Not as s saturated blockage.
     
  6. Deering
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    Deering Senior Member

    Wood is a porous medium. A green tree is about 50% water, and typically around 15-20% when it’s ‘dry’. That leaves a lot of void space. The cellular structure of wood is hydrophilic - it’s designed to swell up to store water. Petroleum-based liquids don’t elicit the same response.

    Any woodworker will tell you that if you paint your piece with a water-based finish, it will ‘raise the grain’, which is basically the wood swelling. Oil-based finishes won’t do that.

    There are lots of different epoxy formulations designed to harden at different speeds. Many of the popular brands offer various hardeners that cure faster or slower.
     
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  7. Blueknarr
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    Blueknarr Senior Member

    Most solvent based paints and wood finishes will raise grain.

    It takes days of water contact to change the dimensions.
     
  8. fallguy
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    fallguy Senior Member

    Most strip planked hulls get glassed; so they end up getting epoxied then.

    It would be an extra step to neat coat the strips prior to laminating glass.

    Of course, there are variations...
     
  9. upchurchmr
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    upchurchmr Senior Member

    In talking about strip planking you need to compare kayak or canoe sized boats to bigger boats.
    Kayak/ canoe will have strips of 1/4 x 3/4.
    Bigger boats might have 3/4 x 3/4 or much larger.
    There is really no reason to precoat a strip before assembling into a boat.
    Kayaks use normal wood glue to edge glue strips together on the frame or form.
    Then the surface is sanded and glass epoxy applied to coat and provide strength.
    You can put neat epoxy on a kayak surface before the glass epoxy coating - it's been done both ways.

    A bigger heavier boat can be done the same way, or you could epoxy each strip together, its probably also edge nailed to set the shape.
    Then coat with glass/ epoxy as above.

    That's way too simple to describe the 100's of different ways people have built modern boats.

    Epoxy does not penetrate very far - it's too thick. Even water takes quite a time to fully penetrate a wood hull.

    If you really want to know - download this book. https://www.westsystem.com/wp-content/uploads/GougeonBook-061205-1.pdf
    And study for a long time.

    Have fun.
     
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  10. Magnus W
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    Magnus W Senior Member

    Does increased depth of the epoxi penetration do anything except making the barrier thicker?

    Does the performance of wood (in general) change with different levels of epoxi saturation? Not so much in terms of say resistance to rot but rather flexibility and strength.
     
  11. Deering
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    Deering Senior Member

    I think you’re focusing too much on penetration and saturation. Unless you’re forcing saturation, by vacuum bagging or some similar means, the epoxy generally won’t soak in more than a couple millimeters. Most of it will remain on or near the surface. Once cured, depending on the species, the wood will be a bit stiffer. But stiffness really increases once the fiberglass is laminated over it.

    Thickness of the wood matters. A layer of fiberglass over a thin strip has a major effect on strength and stiffness, but that same fiberglass over a thicker piece may have a negligible effect.
     

  12. upchurchmr
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    upchurchmr Senior Member

    100% agree.

    If you want info from a group who spent lots of years and lots of money on research, see the Gougeon brothers book as referenced above. Many of us started there.

    Even vacuum bagging won't increase saturation enough to be noticeable.
     
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