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Re: [MedievalSawdust] 'peaked roof' boxes

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  • conradh@efn.org
    ... A kamal is a simple navigational tool that works by sighting a distant target across a known angle. (Traditionally a wood or bone tablet with a string
    Message 1 of 50 , Aug 11, 2009
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      On Mon, August 10, 2009 8:03 am, Liedtke Goetz wrote:
      > I'm home ill - therefore brain-dead - but I suspect there's something in
      > classic geometry that makes possible constructed rather than carved
      > peaked roof chests.  My brain is trying to find the right information but
      > failing....it has something to do with isosceles triangles, 30 and 60
      > degree angles, and such stuff.
      >
      > I've been reading a book on navigational instruments (worth checking out
      > by those on this list) and much of period navigation is based on that
      > same classic geometry.  I wonder if working out the angles could be done
      > with something like a kamal <http://en.wikipedia.org/wiki/Kamal>?

      A kamal is a simple navigational tool that works by sighting a distant
      target across a known angle. (Traditionally a wood or bone tablet with a
      string running from its middle. The far end of the string has a knot in
      it, arm's length away from the user. The knot is held in the observer's
      teeth, so as to give a consistent "arm's length" for every sight taken.
      Navigators use it to judge the height of a star above the horizon. (In
      the Indian Ocean, Polaris is close enough to the horizon to measure
      latitude this way.)

      Kamals only work for small angles, and basically for getting angles
      between two distant objects. You calibrate your kamal by sighting pairs
      of known stars with it, and marking off in "esbah" units, which I
      understand originally referred to finger widths--traditional navigators
      all over the Indo-Pacific just extend their arm with the palm bent at
      right angles toward the face and sight stars that way; the Arabs just
      added standardization by marking the card against the star pairs.

      This actually works for navigation--believe it or not you can get your
      latitude right within thirty miles, as long as you are in low northern
      latitudes and have a clear level horizon to the north.

      More than you ever wanted to know about traditional navigation! But what
      I can't see is how you'd find it useful close up. As I understand Baron
      Conal's problem, he already has a formula for the compound angle he needs,
      it's just a PITA to set up. You don't need a kamal when you already own a
      protractor, and most table saws have a couple of those right on the
      machine.

      Mary's suggestion of kerfing between oversize pieces makes sense, and
      could certainly have been done in period. A similar method from
      traditional metalwork (for precision fitting) is to put chalk or charcoal
      powder on one side of the joint you're fitting, press the parts together
      and look for high spots. The chalk rubs off the high spots on the chalked
      piece, and shows up on the high spots of the bare piece; you then take the
      high spots down a little with file or scraper. Or for woodworkers,
      perhaps a small plane.

      Whether any of these save time over a bunch of trial cuts, questionable.
      They might reduce the firewood buildup problem, though. Personally, I've
      never seen why firewood buildup would be a problem, but then I've heated
      with wood the last thirty years. Gives a whole new perspective on shop
      scrap...

      Ulfhedinn

      >
      > p.s. Latitude Hooks and Azimuth Rings: How to Build and Use 18
      > Traditional Navigational Tools, Dennis Fisher, ISBN 0-07-021120-5 -
      > http://www.amazon.com/Latitude-Hooks-Azimuth-Rings-Navigational/dp/0070211
      > 205/ref=sr_1_1?ie=UTF8&s=books&qid=1249916419&sr=1-1
      >
      ike this....
      >
      >
      > http://s147.photobucket.com/albums/r295/ConalOhAirt/Chests%20and%20Boxes/
      > ?action=view¤t=bf41-1.jpg
    • Cheri or Anne
      I love this group.  Where else can one ask about how to clean copper pots and end up making moonshine in them!  A natural progression.   Anne Go softly and
      Message 50 of 50 , Aug 20, 2009
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        I love this group.  Where else can one ask about how to clean copper pots and end up making moonshine in them!  A natural progression.
         
        Anne

        Go softly and gently for those you meet here will be
        those you know hereafter."

        ---

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