Norwegian Pram- lapstrake construction

Discussion in 'Boat Design' started by druidking, Jun 22, 2010.

  1. druidking
    Joined: Nov 2008
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    Location: New Hampshire

    druidking Junior Member

    Hey guys,
    I'm building a 7.5 ft pram from 15mm thick pine planks (aprox. 4 inches wide). I have a book on how to build one, but it is rather vague on shaping the planks. So i was wondering if anyone could help me to understand how to shape them.
    Once I've got the first plank shaped (and bent) the way I want (and cut the angle), do I trace the bottom of the next plank? What do i do for the top of that plank?

  2. apex1

    apex1 Guest

    Why two times??
  3. DCockey
    Joined: Oct 2009
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    Location: Midcoast Maine

    DCockey Senior Member

    What book?

    Generally in lapstrake planking the lower edge of a plank is spiled from the upper edge of the previous plank with an allowance for the lap width. A traditional Norwegian boatbuilder working at most a couple of molds would then shape the upper edge of the plank by "eye" based on his experience and what shape he wanted for the boat. More "modern" building techniques would generally use a series of cross-sectional molds with the lap locations laid out on the molds, and then lift the plank shapes from the molds.

    This is really a boatbuilding question, not a boat design question. You might try the Boatbuilding section here at or the boatbuilding section of the WoodenBoat Forum.
  4. druidking
    Joined: Nov 2008
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    Location: New Hampshire

    druidking Junior Member

    I have 10 Wooden Boats You Can Build put out by Woodenboat Magazine, and The Boat Building Manual by i don't know who.

    Thanks for you're help, I think after thinking about it for a few hours i came up with the solution to my broblem.
  5. Squidly-Diddly
    Joined: Sep 2007
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    Location: SF bay

    Squidly-Diddly Senior Member

    If you are asking about angle of the cut at bow...

    instead of wrestling with a whole plank, I'd first use a curved section of plank about 12" long and place the on the last plank and fit to the bow with trial and error until it fits right.

    Then copy that angle to the real plank.

    I'd do this by clamping a large belt sander upside down on a bench so you can use both hands on the wood.
  6. messabout
    Joined: Jan 2006
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    Location: Lakeland Fl USA

    messabout Senior Member

    If the planks have much curvature or twist, 15mm thickness is going to be a *****. Also the boat will be heavier in weight than need be. Why are you using such robust planking on a 7.5 foot boat?

  7. Knut Sand
    Joined: Apr 2003
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    Location: Kristiansand, Norway

    Knut Sand Senior Member

    I don't know the load your estimating to load this boat with, but the shape of a pram this short, may come a bit low on the water, (What we locally call "high tide" :D ) 11'-12' ft is the normal (minimum) length of these. Regarding thickness, I'd guess they are 10-12 mm thick, those I've seen (or had, my first boat (12') was one of these, I was 6 yrs old, and king of the world, nice to be king :D ). The width was maybe as wide as 5", also. Too narrow planks may get the bow a bit "crowded" with planks/ klinkers etc..). And during building; shaping of planks, they are just bent, normally not steamed. They use a "beam" under the roof of the shack and planks to press down(/or up).
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