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Thread: Plywood preparation in humid enviroments

  1. #1
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    Default Plywood preparation in humid enviroments

    I'm getting ready to start constructing my first wooden boat. I've found a relatively local supplier of marine plywood, I've got the plans on order, and I'm getting the workspace cleared out.

    The problem I can foresee is that my workspace is an awning in the sub-tropical Texas Gulf Coastal Plains. Although the boat project will be protected from rain, it will not be protected from the humidity. I'm wondering if it would be prudent to treat each sheet of ply with epoxy before I start working with them so that it will be less likely to absorb moisture, especially along the end-grains.

    For those who are curious, the project in question is going to be a Welsford Daniel's Boat. It was originally going to be a Welsford Navigator, I've even purchased and received plans for such, but those plans are going to be shelved for a later date.

  2. #2
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    Default Re: Plywood preparation in humid enviroments

    Quote Originally Posted by t_roy View Post
    . I'm wondering if it would be prudent to treat each sheet of ply with epoxy before I start working with them so that it will be less likely to absorb moisture, especially along the end-grains.
    I wouldn't bother. Unless the supplier has the ply in a climate controlled environment, it should have the same moisture range. Also, once you start cutting you will be exposing endgrain. The epoxy will only be protecting the face. Furthermore, you will need to remove all blush from the sheets before you glue anything together. Failure to do so can lead to joint failure. Good luck on the build and post as you progress.

  3. #3
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    Default Re: Plywood preparation in humid enviroments

    I also would not bother . Don’t fix what ain’t broke.
    More importantly I’d ask, what flavor of ply?
    If the boat is in a tough envoronment( before even being launched) , I’d stay away from occume and lean towards meranti.

  4. #4
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    Default Re: Plywood preparation in humid enviroments

    Quote Originally Posted by Dusty Yevsky View Post
    I wouldn't bother. Unless the supplier has the ply in a climate controlled environment, it should have the same moisture range. Also, once you start cutting you will be exposing endgrain. The epoxy will only be protecting the face. Furthermore, you will need to remove all blush from the sheets before you glue anything together. Failure to do so can lead to joint failure. Good luck on the build and post as you progress.
    I knew about the endgrain, but I didn't think about the fact that it'd be in the same moisture range.

    Quote Originally Posted by wizbang 13 View Post
    I also would not bother . Don’t fix what ain’t broke.
    More importantly I’d ask, what flavor of ply?
    If the boat is in a tough envoronment( before even being launched) , I’d stay away from occume and lean towards meranti.
    I'm looking at either meranti or douglas fir, since the local wood is loblollie pine. The meranti is a little bit cheaper in 6mm/1/4", but then I read stories about nightmares in consistancy... It's a part of why I went from the Navigator to Daniel's Boat, because I could use the difference in wood and sail cost to get better materials then mess around in a nice little boat while I'm working on my CPA.

    I'm from the Houston area. I know full well that sometimes you just have to pay your money and roll your dice. But there's no reason not to tilt the odds in your favor.

  5. #5
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    Default Re: Plywood preparation in humid enviroments

    Can you put eyes on the meranti?
    Is is aqua tek or hydro tek branded.
    Check that the inside lams are not a lighter colored .
    They should all be dark.
    Fir needs glassing, hydro tek... not so much.

  6. #6
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    Default Re: Plywood preparation in humid enviroments

    Quote Originally Posted by wizbang 13 View Post
    Can you put eyes on the meranti?
    Is is aqua tek or hydro tek branded.
    Check that the inside lams are not a lighter colored .
    They should all be dark.
    Fir needs glassing, hydro tek... not so much.
    The hardwood store offers both aqua tek and hydro tek. I will be going to their physical location to select the ply when it comes time, but it's a two hour journey into their part of Houston so it's not something I'm going to do casually.

    I do want to glass the bottom regardless of if it's 'needed' or not. I want practice for the Navigator and 6m Whaler I want to build later on down the road.

  7. #7
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    Default Re: Plywood preparation in humid enviroments

    If you can swing it financially, get Hydrotek. This is built to the BS1088 standard by a reputable manufacturer, so the stamp actually means something. Aquatek is also good but isn't built to 1088. I've used it for non-immersion marine applications and it's great stuff to work with.

  8. #8
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    Default Re: Plywood preparation in humid enviroments

    Okay, so the big take-aways are to not epoxy until assembly, get Hydrotek if I can swing it, and make sure that the inner plys are darker than the veneers on meranti. Anything else I need to know?

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    Default Re: Plywood preparation in humid enviroments

    At assembly I'd be using a few coats of CPES to treat the parts before attaching - not epoxy. CPES soaks in much more effectively and more deeply.
    Then unthickened epoxy on the mating surfaces and thickened epoxy for the final join.

    A layer of epoxy over everything in situ before painting.

    It's not as convoluted as it sounds.
    It's all fun and games until Darth Vader comes.

  10. #10
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    Default Re: Plywood preparation in humid enviroments

    Quote Originally Posted by t_roy View Post
    Okay, so the big take-aways are to not epoxy until assembly, get Hydrotek if I can swing it, and make sure that the inner plys are darker than the veneers on meranti. Anything else I need to know?
    The inner plies should not be lighter, but won't necessarily be any darker. The idea was that the inner plies should, but might not be the same species of wood. They should look similar to the outer plies.

    CPES is not worth the trouble in my opinion. Two schools of thought on this. It is a good primer, but on new wood, I see no benefit. On a weathered plywood surface, it can help.
    Management is the art of counting beans. Leadership is the art of making every being count. --Joe Finch

  11. #11
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    Default Re: Plywood preparation in humid enviroments

    I agree with not using CPES in this case. It would make the panels less “nice” to handle, having been freshly coated with the worlds stinkiest product.

  12. #12
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    Default Re: Plywood preparation in humid enviroments

    Thanks Dave, yes that is what I meant by avoiding ply with junk wood on the inner veneers.

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    Default Re: Plywood preparation in humid enviroments

    A Marine Plywood Primer

    https://www.woodenboat.com/marine-plywood

    In the Sheldon Cooper fun facts department: Meranti is (not) the world's tallest tree, but 97m is up there http://www.dailyexpress.com.my/news.cfm?NewsID=125818
    Management is the art of counting beans. Leadership is the art of making every being count. --Joe Finch

  14. #14
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    Default Re: Plywood preparation in humid enviroments

    I read that consumer guide while waiting for my tax finals. It's why I came here for extra help.

    The plans came in today for Welsford Daniel's Boat. Only four pages versus the eleven for the Welsford Navigator. I'll post up a new thread when I start production.

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