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Re: water ballast vs lead, iron, etc

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  • pvanderwaart
    ... You are quite right that the stiffness of a flat-bottomed hull disappears at quite small angles of heel. When Bolger did some after-capsize stability
    Message 1 of 25 , Dec 2, 2006
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      > By my stiffness formula, the empty slab would be
      > very stiff, but only at very, very, small angle. Once the bottom
      > lifted above the water, a slight breeze would flip it over.

      You are quite right that the stiffness of a flat-bottomed hull
      disappears at quite small angles of heel. When Bolger did some
      after-capsize stability studies of the Martha Jane sharpie, he found
      that the point of no return was much higher than expected, maybe 45 or
      50 degrees. AS-29 was not compromized by thoughts of trailering and is
      more heavily ballasted.

      High topsides and careful attention to hatches and other openings are
      required for safety. You can see this in production boats with inside
      ballast too, such as the water-ballasted 25-footers from Hunter and
      Catalina.

      Peter
    • Guy Vandegrift
      My boat stability project has reached the point where it must go dormant till I get collaborators. The price a professor pays for doing trivial research is
      Message 2 of 25 , Dec 2, 2006
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        My boat stability project has reached the point where it must go
        dormant till I get collaborators. The price a professor pays for doing
        "trivial" research is that it must focus on education. Anybody who can
        contribute is welcome to apply.

        I need someone who either did well in high school physics, geometry,
        and algebra, or who has strengthened these skills in college. Most
        college graduates have poor writing skills, but anybody who can
        write can be prinicpal author on a paper to AJP (American Journal of
        Physics). A high school student with a parent who can write, along
        with somebody who knows boats and can run hull stability software,
        would make an awesome team! Though most papers in AJP have one author,
        I think they will like the diversity and perhaps even physical
        remoteness of those who solve this problem.

        Guy

        See "Stiffness of an Advanced Sharpie" on my homepage at
        http://faculty.valpo.edu/gvandegr/.

        P.S. AJP pays authors ten times what I hear they pay contributors to
        MAIB, which is nothing.
      • Bob Slimak
        Hmmm..... ten times nothing is ... NOTHING! Bob ... Check out the all-new Yahoo! Mail beta - Fire up a more powerful email and get things done faster.
        Message 3 of 25 , Dec 4, 2006
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          Hmmm..... ten times nothing is ... NOTHING!
          Bob


          ---------------------------------
          Check out the all-new Yahoo! Mail beta - Fire up a more powerful email and get things done faster.

          [Non-text portions of this message have been removed]
        • Guy Vandegrift
          That s why I am not interested in writing the paper myself. Re: idea for overbuilt boat . I know I am mixing threads, but both are linked by my attempt to
          Message 4 of 25 , Dec 5, 2006
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            That's why I am not interested in writing the paper myself.

            Re: "idea for overbuilt boat". I know I am mixing threads, but both
            are linked by my attempt to collaborate via internet with a group of
            kids, somewhere in the world. I think the LNS on that project is a
            12-ft "overbuilt" dinghy out of 0.25in by 1.5in lathe sticks (the
            cheaper the better). Instead of a double-transverse layer, consider
            a cross-stitched "weave" of long transverse sticks with longitudinal
            sticks only a few boardwidths accross (short to permit clamping).
            That should solve the buckling problem.

            They say the hull is only a third the cost of a boat. I bet if we
            cut the cost of the hull by a third, people will find ways to cut the
            other 2/3s by 1/3. Both projects are long-range and admittedly long-
            shots, justified by the idea that this is educational, and not too
            dangerous if the work is done by WELL SUPERVISED middle or high
            school kids. This is more fun and a lot more usefull than most of
            the stuff I wrote for AJP.

            Guy


            --- In bolger@yahoogroups.com, Bob Slimak <otter55806@...> wrote:
            >
            > Hmmm..... ten times nothing is ... NOTHING!
            > Bob
          • derbyrm
            Careful on the lath. The stuff one bought forty years ago was fine wood; continuous lengths with few flaws. I used it for model RR roadbed. A few years
            Message 5 of 25 , Dec 5, 2006
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              Careful on the lath. The stuff one bought forty years ago was fine wood; continuous lengths with few flaws. I used it for model RR roadbed. A few years later the only sticks I could find were made up from short segments joined with finger splices. It didn't bend and it broke if you looked at it funny. Probably still adequate for rose vines, but worthless for the task I wanted.

              As for collaboration, don't you first have to find someone who is as enthusiastic about the idea as you are?

              Roger
              derbyrm@...
              http://home.insightbb.com/~derbyrm

              ----- Original Message -----
              From: Guy Vandegrift
              To: bolger@yahoogroups.com
              Sent: Tuesday, December 05, 2006 11:40 AM
              Subject: [bolger] Re: water ballast vs lead, iron, etc


              That's why I am not interested in writing the paper myself.

              Re: "idea for overbuilt boat". I know I am mixing threads, but both
              are linked by my attempt to collaborate via internet with a group of
              kids, somewhere in the world. I think the LNS on that project is a
              12-ft "overbuilt" dinghy out of 0.25in by 1.5in lathe sticks (the
              cheaper the better). Instead of a double-transverse layer, consider
              a cross-stitched "weave" of long transverse sticks with longitudinal
              sticks only a few boardwidths accross (short to permit clamping).
              That should solve the buckling problem.

              They say the hull is only a third the cost of a boat. I bet if we
              cut the cost of the hull by a third, people will find ways to cut the
              other 2/3s by 1/3. Both projects are long-range and admittedly long-
              shots, justified by the idea that this is educational, and not too
              dangerous if the work is done by WELL SUPERVISED middle or high
              school kids. This is more fun and a lot more usefull than most of
              the stuff I wrote for AJP.

              Guy

              --- In bolger@yahoogroups.com, Bob Slimak <otter55806@...> wrote:
              >
              > Hmmm..... ten times nothing is ... NOTHING!
              > Bob





              [Non-text portions of this message have been removed]
            • Guy Vandegrift
              Thanks for warning me about lathe. I would want to do any scarfing myself. Regarding the enthusiasm problem, middle school kids can get enthused about
              Message 6 of 25 , Dec 5, 2006
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                Thanks for warning me about lathe. I would want to do any scarfing
                myself. Regarding the enthusiasm problem, middle school kids can get
                enthused about anything. I just have to verify that the middle school
                is aware of the safety issues. Also, a novice amateur boatbuilder
                might like the idea of an overbuilt dinghy. I didn't regret
                overbuilding my Piccup Pram until I tried to lift it. Guy.

                --- In bolger@yahoogroups.com, "derbyrm" <derbyrm@...> wrote:
                >
                > Careful on the lath. ...
                > ... don't you first have to find someone who is as enthusiastic
                about the idea as you are?
                >
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