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[bolger] Re: Convertible Cabin-top

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  • Peter Vanderwaart
    ... The wide cabin top/side deck of the Catfish is an important part of the design, and while I think some alteration is feasible, it does require some
    Message 1 of 11 , Mar 1, 2000
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      > > 1. In the Bolger and Michalak designs, the slot-top cabin is used to
      > > keep the boat from swamping in the case of a knock-down and it may
      > also
      > > provide some structural value as well. If I start with a design like
      > > Catfish and remove the permanent cabin, am I significantly
      > compromising
      > > the structure and safety (knock-down) of the design?

      The wide "cabin top/side deck" of the Catfish is an important part of
      the design, and while I think some alteration is feasible, it does
      require some thought.

      Structurally, in order to keep the boat clear for sprawling and
      sleeping, there is very little framing amidships. The deck contributes
      a major part to the stiffness (torsion resistance) of the center part
      of the boat. If you were to make the deck real narrow, I think you
      might consider putting in a midships frame.

      From the point of view of safety, the deck keeps the water out in a
      knockdown, and making the deck narrower would detract from that
      function.

      If you were to try to re-think the boat into a more conventional
      arrangement, you could put a full bulkhead across the boat a foot or so
      aft of the mast to enclose a cuddy. The cabin top would be solid. The
      deck aft of that point would be elimated. Along the sides of boat there
      would be side-facing seats at a comportable height. The space beneath
      the seats would be enclosed for flotation. You might need another frame
      between the bulkhead and the aft end of the cockpit. With this
      arrangement, you could sit well out to the side for optimum use of live
      ballast with your back comfortable against the hull side. This is like
      the Cynthia J. and worked out well.

      Compared to the original, the boat would probably be heavier, better
      for daysailing, not suitable for sleeping, faster in a breeze (due to
      the better use of live ballast). And, there is the danger that you
      would still have Chebacco-envy.

      Peter
    • Chris Crandall
      ... First, topsides means the side of the hull, from the waterline to the gunwhales. They are *always* structurally significant, of course. But the top of the
      Message 2 of 11 , Mar 1, 2000
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        On Tue, 29 Feb 2000 Wmrpage@... wrote:

        > This is pure B.S., but I think:

        > 1) Yes: the great freeboard of the "slot-top" cabins like
        > "Birdwatcher", etc. are probably very important to their ultimate
        > stability. (pure B.S., of course) I very much doubt that the topsides
        > are structurally significant


        First, topsides means the side of the hull, from the waterline to the
        gunwhales. They are *always* structurally significant, of course.

        But the top of the boat (the "upper deck"?).
        They are structurally significant, too.

        Imagine a cardboard box, with no top at all.
        Then imagine a cardboard box, with two flaps, that, when firmly
        taped down, don't quite meet in the center.

        Which is stiffer?
        The one with the attached flaps, and by a long shot.

        Chris Crandall crandall@... (785) 864-4131
        Department of Psychology University of Kansas Lawrence, KS 66045
        I have data convincingly disconfirming the Duhem-Quine hypothesis.
      • Lincoln Ross
        I have a vague recollection of something like this that was available in the 1970 s, possibly by Oday. short-@shortypen.com wrote: original
        Message 3 of 11 , Mar 1, 2000
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          I have a vague recollection of something like this that was available
          in the 1970's, possibly by Oday.

          short-@... wrote:
          original article:http://www.egroups.com/group/bolger/?start=3346
          > 1 - How about a telescoping cabin that would pop up? snip
          > 2 - How about a hinged cabin that rotates up? snip
          >
          > snip. Wonder why a boat like this
          > hasn't been designed yet?
          >
        • Shorty@ShortyPen.com
          1 - How about a telescoping cabin that would pop up? Normal looking deck, then, after dropped sail, pull up the cabin. That way can keep a low sail and have
          Message 4 of 11 , Mar 1, 2000
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            1 - How about a telescoping cabin that would pop up? Normal looking
            deck, then, after dropped sail, pull up the cabin. That way can keep a
            low sail and have a tall cabin.

            2 - How about a hinged cabin that rotates up? The hinge at the forward
            edge of the cabin, triangular shaped sides to the cabin, and pops up
            when sails are dropped.

            I really like the idea! Low center of gravity while sailing, tall cabin
            at anchor (home made anchor that is). Wonder why a boat like this
            hasn't been designed yet?
          • KF4call@aol.com
            In a message dated 00-03-01 22:28:23 EST, you write:
            Message 5 of 11 , Mar 1, 2000
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              In a message dated 00-03-01 22:28:23 EST, you write:

              << - How about a telescoping cabin that would pop up? Normal looking
              deck, then, after dropped sail, pull up the cabin. That way can keep a
              low sail and have a tall cabin. >>

              One of the major manufacturers of porta-potties already makes one. It is an
              inflatable. Sort of a phone booth-like room with inflatable pillars on each
              corner and a porta-pottie sitting on the floor of the booth.. An outrageous
              price as I recall though.

              <<How about a hinged cabin that rotates up? The hinge at the forward
              edge of the cabin, triangular shaped sides to the cabin, and pops up
              when sails are dropped>>

              I thought of something similar...a set up like the sun screen on a
              traditional baby buggy, ...side frames about 3-4 feet long, with pivot points
              aft and the "top" of the frame made to fold down forward (side frames joined
              forward at a central point ) or to fold "up" aft to extend over the storage
              compartment of an Oldshoe (or similar small boat), which could have a
              portapottie placed in it.

              Regards, Warren
            • Wmrpage@aol.com
              The correct analogy is not between an open box and one with abutting flaps, but between a box with closed and joined flaps (i.e. able to take both compression
              Message 6 of 11 , Mar 1, 2000
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                The correct analogy is not between an open box and one with abutting flaps,
                but between a box with closed and joined flaps (i.e. able to take both
                compression and tension loads) and one with separated flaps, joined only at
                one end (i.e. near the bow). The latter corresponds to the the "slotted
                cabin" designs. The former is a box girder. In doing this experiment with
                small boxes, the ability of closely fitting flaps to absorb compression loads
                might give a misleading impression. If the flaps of the latter are trimmed
                back so they don't can't make contact with each other and that box's rigidity
                compared to that of a box with the flaps butted and taped together, I think
                you might find some merit in my argument. I remain inclined to think that as
                far as structural strength is concerned, the two halves of a "slotted" cabin
                top have to be considered as independent, non-mutually supporting,
                structures. As far as bouyancy generating structures above the sheer-line
                ("top-sides") go, can you suggest a suitable terminology that takes into
                account the bouyancy of both the "top-sides" and the cabin sides, as so
                dramatically described in Bolger's description of "Birdwatcher" laid on its
                beams ends so the children can watch the fishies through the submerged cabin
                windows?

                Bill in tropical MN, wondering where I put my canoe's new license.
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