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nailing pattern for longitudinal strip built

Discussion in 'Traditional All-Wood Construction' started by mccloud, Dec 22, 2016.

  1. mccloud

    mccloud Wooden Canoe Maniac

    I've only worked on two longitudinal strip built canoes, but both had the same problem: a lot of cupping of planking particularly along the bilge near the center of the canoe. Why? It's not easy to get rid of this cupping, but after soaking, steaming, and clamping, I can sometimes get another nail thru the center of the plank to hold it down permanently. So after dealing with this problem too often I had a thought - did any of the builders of longitudinal strip built, all wood canoes stagger the nails, for example, on one rib position the nails close to the lap in the usual way, and on the adjacent rib, put the nail thru the center of the plank? Seems this would be a good and permanent solution to the cupping problem. Tom McCloud
     
  2. Paul Miller

    Paul Miller Canoe Nut

    I could be confused, but are you getting cupping on an all wood Canadian with plank only 1 1/2" wide?

    Or are you talking about a wide board?

    Pics of nail patterns attached.

    Paul
     

    Attached Files:

  3. OP
    OP
    mccloud

    mccloud Wooden Canoe Maniac

    Both canoes I've worked on are longitudinal strip built, with the strips around 1 1/2" wide. The cupping is always to the inside of the canoe, creating a gap of ~ 1/8" between the rib and the strip, and sometimes pulling a lap loose, creating a crack in the hull. Your photos show all the nails positioned close to the lap, typical of the way these all wood canoes were typically built, not staggered. My question, or comment, is that if the nails were staggered on alternate ribs when the canoe was built, cupping could never occur. Tom McCloud
     
  4. alick burt

    alick burt LOVES Wooden Canoes

    Hi Paul & Mcloud

    Sounds like Mccloud is getting cupping on an all wood boat with narrow planking.
    I have this on a couple of planks on the boat I am working on and yes they are in the bilge area but I will probably leave them alone as I think it unlikely that they will go back to the original shape and as long as they don't leak I'm not going to mess with them.If anyone has an easy trick for this I would be interested.
    you can see one of them 7 planks up in this picture.
    20161112_162837.jpg
    Cheers
    Alick
     
  5. Dick Persson

    Dick Persson Canoe builder & restorer

    The cedar-strips to be used in the bilge areas were coved (or backed-out as the old timers called it) during the building process to fit better.

    Cheers
    Dick
     
    Last edited: Dec 24, 2016
  6. alick burt

    alick burt LOVES Wooden Canoes

    Thanks Dick
    That's interesting but it seems on my boat at least that if this was done it was only done on one part of one plank ( not all along it and not evenly)it is flat as normal on the other side of the boat and at the other end of the plank on the same area of the hull. Still I am not in a rush to do anything about it as it isn't too bad.
    Merry Christmas
    Alick
     
  7. OP
    OP
    mccloud

    mccloud Wooden Canoe Maniac

    Easy to see how 'coving' would help make the fit. Good information that I had not heard before. Thanks, Dick. I can imagine two ways to make a cove: 'pinch' the cedar until it bulges outward, then tack it in place, which leaves the wood the same thickness, or 'gouge' the inside face thus making the wood a little thinner and therefore easier to bend and fit.

    The copper nails were delivered about an hour ago, so tomorrow I can go back to work.
    Tom McCloud
     

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