Plywood application

Discussion in 'Boat Design' started by captlloyd, Jul 4, 2015.

  1. captlloyd
    Joined: Jan 2015
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    captlloyd Junior Member

    Here is one for any of you builders who have worked with plywood construction. I am thinking of building a plywood hull and my thinking is that applying the plywood on a bias will enhance and ease its ability to be formed into a panel with some compound curve. I am talking about panels that will be roughly 4x7. Could I get some comments on this? Thanks. :)
     
  2. upchurchmr
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    upchurchmr Senior Member

    http://www.westsystem.com/ss/assets/HowTo-Publications/GougeonBook 061205.pdf
    Here is the bible.

    You can get lots of curvature, if you have the right thickness and its within the ability of the panel.
    Will you be working with 3 ply or 5 ply panels?

    5 ply will be less valuable to try on the bias. Three ply will be rather strange shapes that will result. I think.

    What kind of a hull?
     
  3. captlloyd
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    captlloyd Junior Member

    Thanks upchurchmr. I will be working with both 4 and 5 ply on a one-off design.
     
  4. captlloyd
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    captlloyd Junior Member

    That would be a 38 ft catamaran hull.
     
  5. snowbirder

    snowbirder Previous Member

    Building part of a Kurt Hughes a while back, I used 3 ply, 3mm plywood to make a developed surface / complex curve. It worked very well to get a catamaran hull curve.
     
  6. rwatson
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    rwatson Senior Member

    No, not so much.

    The ply layers are angled differently, so the grain alignments effect is almost totally negated.

    BUT - dont forget you can use a router or circular saw to cut grooves to encourage curves in a desired direction
    eg
    http://www.boatdesign.net/forums/bo...8-plywood-14-degreesees-3-12-pitch-53591.html


    These examples below are about the best you can do.
     

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  7. Jamie Kennedy
    Joined: Jun 2015
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    Jamie Kennedy Senior Member

    This fellow from 'the other forum' ;-) made some birch bark style cuts.
    http://forum.woodenboat.com/showthread.php?165793-Plywood-Canoe-Concept-Birchbark-Style

    Beautiful results...
    [​IMG]

    I think the darts add to the aesthetic; but it may depend on the design, and the beholders familiarity with the tradition. Truly amazing what can take shape without the use of a mold. Adney's classic would be the resource on where to place the darts to get certain traditional shapes. See pages 30 and 31. The Micmac Rough Sea Canoe is my personal favourite. Amazing feat of engineering. See page 12...
    https://books.google.ca/books?id=1a...AA#v=onepage&q=tappan adney 58 micmac&f=false
     
  8. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Diagonal molding is fairly common and you can get much tight curves than shown above. I've done both power and sail with Ashcroft and double diagonal and the key is to figure out the tightest radius you'll need to bridge, then use the thickness necessary to make this radius. The width of these panels will change along the length of the hull, as the amount of curve changes. Also the angle you'll need to apply it will also change a bit too.

    I wouldn't use a 4 ply, as the veneer orientation would be odd to say the least. The only even veneer count stocks I've seen are low grade construction plywood, which generally isn't suitable for use in a hull.
     
  9. Jamie Kennedy
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    Jamie Kennedy Senior Member

    Par. How difficult is it to obtain and work with single veneers and do your own orientation, ala cold-molding? What sort of compound curves are possible?
     
  10. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Veneers are easier to work with than plywood, but it's also more delicate work, especially the first layer. Curves can be much tighter, because the veneers are thin. I've found no design that couldn't be molded with veneers. As an example I did a 16' powerboat some years ago, with 1/10" veneers and the bilge turn at the transom was about a 3" radius.

    Veneers aren't hard to find, though you'll want to purchase un-backed, "live edged" fitches, for the best choices.
     

  11. captlloyd
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    captlloyd Junior Member

    Thanks.

    Thanks for the input guys, the info is helpful. ;)
     
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