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50591Re: [bolger] Re: External chines (runners?)

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  • Martyn Aldis
    Sep 1, 2006
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      In message <00eb01c6cc92$25f87810$0a00a8c0@oemcomputer>, John and Kathy
      Trussell <jtrussell2@...> writes
      >PCB's essay on Light Dory in Small Boats states that the external
      >chines may reduce turbulance at the chines and add slightly to
      >stability, but I've never seen anything that suggests that they prevent
      >leeway.
      >
      >Conrad Natzio in England sells plans for various flat bottomed boats
      >and at one time had a flat bottomed pram with runners on the bottom
      >which he said allowed the boat to sail upwind. However, he has not
      >incorporated this feature in subsequent designs and I infer that the
      >runners were not that effective.

      I have an Oyster Catcher built to Corned Nato plans. There is far too
      little lateral area. Even an oyster could escape if it jumped up-wind a
      few times.

      The old off-centre board is becoming the rudder blade and a new tilt
      dagger board is under construction. It may even work.

      The other boat we have with external chines is a Tortoise and I think
      that may have too much "foils" area - I'm going to try a Mirror rudder
      as the large one on the plan is so sensitive.

      About deference to the designer's intentions. One great advantage of the
      books is that PCB gives us hints about why he did what he did and he
      often has variations on a theme. I would not put a full stern deck on a
      Tortoise again. It makes it very difficult to get the crew weight were
      it is needed running in a breeze and as we don't get ice in our harbour
      and do not go mud larding I have no need of the deck to flop on when the
      ice gives way or my boot hits a soft patch of mud. The Brick does not
      have the full deck.

      A modification I made on the Tortoise that worked well was to use the
      "New Instant Boats" smooth glass chine for the ends of the bottom and
      the original external chine for the sides. I've added topping lifts
      (Lazy Jacks) to the lateen rig and they are really worthwhile. I can now
      rig the boat with the sail in the lifts and wheel it to the water and be
      away fast and without the yard going in the sea. Similarly the sail
      doesn't smoother me at the end of the outing. This would have been
      useful in 1990 when we first rigged the boat and our son was a child.
      --

      Martyn Aldis, e-mail martyn.aldis@...
      ==============================================================================
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