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41085Re: Sharpie Cat design

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  • graeme19121984
    Dec 11, 2004
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      The cabin is neat. Kinda Birdwatcher flexible utility. Ok for semi-
      protected waters?

      What about individual hull static WLLength/WLBeam ratio? Maybe ~
      18'/23"? Giving approx 9.3? Too high?

      Wharram's Design book says his first Atlantic crossing catamaran,
      Tangaroa, was 23'6". It says the defects were: it had a flat bottom
      which pounded ( Bolger says sharpiecat would be rather noisy), its
      8/1 individual hull L/B dragged a displacement wave,

      and its full
      bows gave a slow hull speed. (also after this cat he adopted as one
      of his design principles: No permanent deck cabin between hulls.)
      IIRC JW states elsewhere superstructure height should be 11% (no
      more than 15 percent) of length, or windage will be too much.

      Wharram's trailerable 16' Maui design (now not marketed due to newer
      stitch and tape stringerless construction methods superseding) has
      the option of a solid ply bridgedeck. I gave a lot of thought to
      somehow adding spartan accommodation - in the hulls by raising
      topsides but leaving an open bridge deck, or by walling in the
      bridge deck something like Bolger's Fishcat with a tent top, and so
      on. The 60 degree V hulls, displacement, deck clearance and
      seaworthiness made it too difficult for me.

      However a simple trailable catamaran, easily (= quickly) rigged and
      launched at the boatramp, with some spartan accomodation (not a
      tent) for one or two, yet with acceptable performance remains an
      attractive concept.

      Could Sharpiecat be reduced to a trailable beam (Sail area may need
      complementary reduction/lowering), or could the bridgedeck/cabin be
      fastened down over raised hull coamings in an easily demountable
      way? To trailer it dissassembled put the cabin, rotated 90 degrees,
      on top of the hulls.
      Graeme

      --- In bolger@yahoogroups.com, "Todd" <ktsrfer@m...> wrote:
      >
      > The cabin is the kicker on this cat . Seems you can't have your
      cake
      > and eat it to. Start optimising the cabin for windage you end up
      > with making the hulls taller to acommadate space lost in cabin
      which
      > adds windage. The cat just looks fun . But I keep seeing 2 skinny
      > hulls one short and a one long with a big square cabin in the
      > middle;) I'll keep you posted.
      >
      > Todd
      >
      > --- In bolger@yahoogroups.com, "doug6949" <prototype@c...> wrote:
      > >
      > > Windage is always going to be a factor to consider in catamaran
      or
      > > pontoon designs. Any cabin you put on it will significantly
      > increase
      > > the profile.
      > >
      > > 18" freeboard is not much for a 23 foot cat. Your cabin profile
      is
      > > what you need to evaluate.
      > >
      > > Doug
      > >
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