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Re: [bolger] Re: Spar making

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  • Patrick Crockett
    Doug: An excellent analysis -- useful to me in future projects, I think. Patrick
    Message 1 of 24 , Dec 9, 2007

      An excellent analysis -- useful to me in future projects, I think.


      Doug Pollard wrote:
      > Wanna say a little more about spar making. I would say that spar
      > size is more a matter of how you think than any size a designer can
      > decide on. A rig designer has to make his decision based on the idea
      > that we very unprofesional boat builders will use a piece of wood that
      > is not perfect and maybe even worse than that. Normally you figure that
      > something has to carry a certain load then you double or even tripple it
      > to allow for all the things you can't calculate. A step ladder for example.
      > So the builder decides and he makes that decision at the lumber
      > yard. If he can find a perfect piece of very light strong wood he can
      > make the spar smaller than called for. If the wood selected is mediocre
      > the spar needs to be what the designer calls for. If you pick a louzy
      > piece of wood you better make the spar plenty heafty and in which case
      > you will wind up with a heavy rig that may even be weaker than the
      > designer intended.
      > The guy who designs things from wood faces a really difficult
      > problem where strength of material is concerned. He likely has a table
      > that gives the strength of a piece of wood of a certain kind . The
      > problem is the figure on that table is only for the piece of wood
      > tested. Or maybe an average of a bunch of differencet pieces.
      > The test for a mast has traditinally been to set the ends on a
      > sawhorse and stand in the middle if it doesnt break it's good,but then
      > that depends on how big the mast is. If your mast is for a 14ft boat
      > you will likely break then all.
      > If you're not going to put much thought into buying wood I would
      > say make it as strong as called for because very little thought and
      > little understanding of wood is what the designer was counting on.
      > Doug
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