I need help decking a canoe, please......

Discussion in 'Sailboats' started by 360weatherbound, Mar 10, 2010.

  1. 360weatherbound
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    360weatherbound Junior Member

    I have a set of plans for a decked canoe. I am trying to build the mold for the deck. I measure from the sections to their respective baselines with a measuring tape off the attached pdf and take the width from the plans. With these points I draw an arc which represents the decktop.
    I just don't see how these series of arcs avery 12" are going to meet up with the hull which isn't flat at the sheer line.
    Does the arcs on the file (attached) represent the same one I am going to draw as above?
    :confused:

    Thanks
     

    Attached Files:

  2. alan white
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    alan white Senior Member

    What matters is that the crown of the deck is fair. It appears the sweep of the deck crown can be established by sagging a string or wire from each end (to the height of the lowest midship deck height) and using a straight-edge at each station to create three points---- port half breadth at the sheer, stbd half-breadth at the sheer, and deck height at centerline.
    Each mold station will have its own unique set of points. A perfect arc will connect the three points. Draw the arc by swinging a pencil on a string from a movable pivot. The pivot point wiill be different for each mold, though it will always fall along a line on the vertical centerline of the hull.
    You can draw right on the molds or use paper and transfer to the molds.
    This method will be the most accurate, but it will only work if the deck crown curvature is consistant, which I'm almost certain it is viewing the drawings.
     
  3. 360weatherbound
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    360weatherbound Junior Member

    Looking at this plan how would one make a mold for the deck without turning the boat hull over? Or is that part of the project?
    Am I supposed to use the scale at the bottom with the side view of the canoe and measure the hash marks with the scale above the boat and that becomes the top of my arc, take the width cut it out?
    Then do I (looking at section 7 for example) use that scale, measure to baseline and get I 9 inches. So if I were to invert the arc and attach it to a
    9" board and do the same for the rest, would that be my mold?
    Thanks
     
  4. 360weatherbound
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    360weatherbound Junior Member

    Little more clear.

    The bottom, I think shows the deck three inches above the hull at section 7.
     
  5. alan white
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    alan white Senior Member

    Flip the boat and make sure to level and brace it to remain level while you build the deck. You haven't in
    Sect. #8 or #9 seem to be the lowest (and the plans show both to be nearly the same). Seems if you sagged a wire or string (first making dead sure the boat is level side to side), you'd find that the deck crown at each 12" station was in agreement with the plan (measurement of baseline to deck crown).
    You are, in essence, lofting the fore/aft curve of the deck crown, which is the accurate way to do it short of lofting. This could have been lofted on the floor but I'm curious how you are building the hull--- are you lofting, or did you get full size patterns, etc.?
    Is the boat plywood? Is the deck tortured plywood or strip-built? Just curious.
     
  6. 360weatherbound
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    360weatherbound Junior Member

    The boat is plywood, I used 1/4 " marine grade fir. It was not Ideal, It was all that was around. I would do it differently. If by tortured you mean cut in slight arcs and forced down, yep it was torture.
     
  7. alan white
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    alan white Senior Member

    1/4" will be rugged! Harder to torture too. I wonder if you'll be able to torture the deck down? If all you can get ahold of is 1/4", you may want to strip the deck instead of plywood. Others might comment at this point regarding how difficult it might be to use 1/4" in this situation.
    Now I can tell you a skin-on-frame deck would be very doable and light as well, but you probably would prefer a solid deck.
     
  8. 360weatherbound
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    360weatherbound Junior Member

    I used 1/4 for the hull, didn't know better and it was all i could get. Could I have built this in any plywood? Seeing that it is sealed. I was told the glue would break apart in water.
    Anyway, I am going to use foam for the deck, and plan to build another all in foam.
    To lighten it up I planed at least 25 percent off the boat course that created a bunch of sanding and pathching. I mistakenly thought it wouldn't matter too much under that black carbon cloth, apparently it will.
     
  9. alan white
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    alan white Senior Member

    There is a big difference in plywoods. AC or better, AB exterior will work, but I have no idea what you used. Luan? If so, rather weak and sometimes the glue is not waterproof. Did you do a boil test?
     
  10. 360weatherbound
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    360weatherbound Junior Member

    nope, just used marine plywood. 5 ply. some kind of fir. It was a bit heavy, I thought. I wont do it twice. I thought the point of epoxy and cloth was to keep water out?
     
  11. alan white
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    alan white Senior Member

    Epoxy is one product and glass is another. Epoxy alone forms a waterproof barrier, and glass may also be used to lend tensile strength and abrasion resistance. Plywood already has enough tensile strength so that sealing the surface with epoxy alone is enough. However, adding a layer of fiberglass outside adds toughness to the surface.
    Marine plywood need not be boil-tested. It's good you chose marine, since a lot of plywood out there is not suitable for boats. Even if you slather epoxy onto cheap plywood, there may come a day when water somehow gets in. A scrape, a screw hole, rainwater sitting for weeks or longer, once in, water can do a lot of damage--- much more than unsealed wood, since the water can't easily get out. Marine plywood stands this abuse far better than non-marine plywood. It has virtually no voids, more plies for greater consistancy and strength, and glue that won't let go even if sopping wet for years.
     
  12. messabout
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    messabout Senior Member

    Strip build the deck. Lighter, strong enough, not difficult, looks good too.
     

  13. 360weatherbound
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    360weatherbound Junior Member

    About the wood?

    I haven't checked on price, but why use wood at all? Woudnt foam be the best? I have what I have now but I am going to add strips of wood over the mold, slice foam and shoot for a round hull with few flat areas on the next one..
    The plywood is way to hard to work with. To make matters worse, I desided to shave off 1/16" where I could for weight, needless to say fairing was a hassle.
     
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