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Re: water ballast vs lead, iron, etc

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  • adventures_in_astrophotography
    Timbo, ... Last night I did some calculations exactly along these lines and convinced myself that what I wrote yesterday was in error. I humbly withdraw those
    Message 1 of 25 , Nov 29, 2006
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      Timbo,

      > Bottom lines:
      > Weight is weight.
      > COG and COB determine righting moment.
      > Dense materials tend to make more useful ballast because they provide
      > a greater shift in the COG relative to the COB

      Last night I did some calculations exactly along these lines and
      convinced myself that what I wrote yesterday was in error. I humbly
      withdraw those remarks! It's especially embarassing since I'm an
      astrodynamacist by trade and have enough physics and engineering
      background to know better. Next time I'll remember the old adage that
      a closed mouth gathers no foot.

      As for Cartoon 40, I still would use the lead shot, mainly for the
      reason given above, but also because it's simpler to build the boat
      that way, and another couple hundred pounds on the ramp shouldn't be a
      problem.

      Jon Kolb
      www.kolbsadventures.com/boatbuilding_index.htm
    • derbyrm
      But think of the pleasure you give to others. :-) Roger derbyrm@NOSPAMinsightbbNOSPAM.com http://home.insightbb.com/~derbyrm ... From:
      Message 2 of 25 , Nov 29, 2006
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        But think of the pleasure you give to others. :-)

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

        ----- Original Message -----
        From: adventures_in_astrophotography
        To: bolger@yahoogroups.com
        Sent: Wednesday, November 29, 2006 9:41 AM
        Subject: [bolger] Re: water ballast vs lead, iron, etc


        <snip>

        Next time I'll remember the old adage that a closed mouth gathers no foot.

        Jon Kolb
        www.kolbsadventures.com/boatbuilding_index.htm
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      • Christopher C. Wetherill
        Jon, Bear in mind that the two advantages of dense ballast are that it lowers the aggregate CG much more effectively than water, thereby giving a better
        Message 3 of 25 , Nov 29, 2006
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          Jon,

          Bear in mind that the two advantages of dense ballast are that it lowers the
          aggregate CG much more effectively than water, thereby giving a better
          righting moment for a given displacement and that it provides righting
          moment in a swamped boat. The second point may be the source of this thread
          in the first place as PCB opined in one of his books that the water ballast
          in the design he was discussing at the time would not hold the boat upright
          for bailing when swamped.

          btw, we marine engineers have training in fluid dynamics, but I can't speak
          reliably about airplane flight dynamics without crunching numbers.

          V/R
          Chris
          -----Original Message-----
          From: bolger@yahoogroups.com [mailto:bolger@yahoogroups.com]On Behalf Of
          adventures_in_astrophotography
          Sent: Wednesday, November 29, 2006 9:41 AM
          To: bolger@yahoogroups.com
          Subject: [bolger] Re: water ballast vs lead, iron, etc


          Timbo,

          > Bottom lines:
          > Weight is weight.
          > COG and COB determine righting moment.
          > Dense materials tend to make more useful ballast because they provide
          > a greater shift in the COG relative to the COB

          Last night I did some calculations exactly along these lines and
          convinced myself that what I wrote yesterday was in error. I humbly
          withdraw those remarks! It's especially embarassing since I'm an
          astrodynamacist by trade and have enough physics and engineering
          background to know better. Next time I'll remember the old adage that
          a closed mouth gathers no foot.

          As for Cartoon 40, I still would use the lead shot, mainly for the
          reason given above, but also because it's simpler to build the boat
          that way, and another couple hundred pounds on the ramp shouldn't be a
          problem.

          Jon Kolb
          www.kolbsadventures.com/boatbuilding_index.htm
        • Nels
          ... I agree Jon, Somehow I have to wonder why a person would build a boat with a lot of effort and expense invested to keep water out and then put holes inside
          Message 4 of 25 , Nov 29, 2006
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            --- In bolger@yahoogroups.com, "adventures_in_astrophotography"
            <jon@...> wrote:
            > As for Cartoon 40, I still would use the lead shot, mainly for the
            > reason given above, but also because it's simpler to build the boat
            > that way, and another couple hundred pounds on the ramp shouldn't be a
            > problem.
            >
            > Jon Kolb
            > www.kolbsadventures.com/boatbuilding_index.htm

            I agree Jon,

            Somehow I have to wonder why a person would build a boat with a lot of
            effort and expense invested to keep water out and then put holes
            inside to colect water to make it more stable. Not to mention the
            environmental issue regarding contamination of other waters with
            unfriendly flora and fauna.

            I would consider making the ballast boxes with closing lids and
            searching some garage sales for cast iron weights that are used in
            exercise machines. Many are also encapuslated with vinyl so they don't
            even rattle around.

            Transferring them back and forth to the boat would even give a person
            a work-out at the same time:-)

            Nels
          • Derek Waters
            ... I have to wonder why a person would build a boat ...to keep water out and then put holes inside to colect water to make it more stable. The primary
            Message 5 of 25 , Nov 29, 2006
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              "... I have to wonder why a person would build a boat ...to keep water out
              and then put holes inside to colect water to make it more stable."

              The primary answer is, I think, that in the event of a hull breach all that
              metal ballast will tend to sink a wooden boat. The water ballasted hull will
              need much less volume devoted to floation to remain safely above water. Of
              course, the water ballast has a larger volume requirement than the metal,
              implying tradeoffs. The metal can sit with its mass concentrated lower in
              the same hull shape, but the foam has weight and generally needs to be
              placed high in the hull to ensure an upright tendency when flooded. In a
              converted design the high position of the foam is likely to reduce useful
              interior volume. Some shapes and sizes suit one approach, some another.

              'Horses for courses', in other words.

              cheers
              Derek
            • Nels
              ... all that ... hull will ... water. Of ... metal, ... lower in ... useful ... Good points. Perhaps a system to easily jettison the dumbells in case of a
              Message 6 of 25 , Nov 30, 2006
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                --- In bolger@yahoogroups.com, "Derek Waters" <dgw@...> wrote:
                > The primary answer is, I think, that in the event of a hull breach
                all that
                > metal ballast will tend to sink a wooden boat. The water ballasted
                hull will
                > need much less volume devoted to floation to remain safely above
                water. Of
                > course, the water ballast has a larger volume requirement than the
                metal,
                > implying tradeoffs. The metal can sit with its mass concentrated
                lower in
                > the same hull shape, but the foam has weight and generally needs to be
                > placed high in the hull to ensure an upright tendency when flooded. In a
                > converted design the high position of the foam is likely to reduce
                useful
                > interior volume. Some shapes and sizes suit one approach, some another.
                >
                > 'Horses for courses', in other words.
                >
                > cheers
                > Derek

                Good points. Perhaps a system to easily jettison the dumbells in case
                of a breach might be possible, and maybe quicker than pumping out
                water tanks.

                I wonder, in the olden days, if this is where the expression "getting
                your rocks off" originated?

                Nels
              • Guy Vandegrift
                Timbo, As far as I can tell, your explanation of righting moment is correct. I think one can go a bit further when talking about a flat bottomed Bolger Box. I
                Message 7 of 25 , Nov 30, 2006
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                  Timbo,

                  As far as I can tell, your explanation of righting moment is correct.
                  I think one can go a bit further when talking about a flat bottomed
                  Bolger Box. I finally documented some stuff I did with
                  non-mathematical students a few years ago. See the unfinished essay

                  "The Stiffness of an Advanced Sharpie" at

                  http://faculty.valpo.edu/gvandegr/

                  Though the equations take more time to work through, they can also
                  yield insights. For example, the blunt end of prams and advanced
                  sharpies only slightly increase the stiffness (small angle righting
                  moment) of a boat. But even a slight increase in overall beam has
                  significant effect.

                  If anybody has software to calculate righting moment, let me know.
                  There is more to done on this project.

                  Guy
                  --- In bolger@yahoogroups.com, timbo@... wrote:
                  >
                  > There are two things that determine righting moment of a sailboat.
                  >
                  > They are:
                  > Center of boyancy
                  > and
                  > Center of gravity
                  >
                • graeme19121984
                  Guy, at your The Stiffness of an Advanced Sharpie at http://faculty.valpo.edu/gvandegr/ there is this: This axis of rotation ensures that the total area
                  Message 8 of 25 , Dec 1, 2006
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                    Guy,

                    at your "The Stiffness of an Advanced Sharpie" at
                    http://faculty.valpo.edu/gvandegr/ there is this:


                    "This axis of rotation ensures that the total area of this
                    underwater section remains constant. Close inspection of the graph
                    indicates that the rotation slightly increases the area under the
                    waterline. Hence the rotation is accompanied by a slight lifting of
                    the boat, which becomes important only at large angle, I believe."

                    What lifts the boat? How is it lifted if it remains the same mass?
                    (disregarding any lifting component of the forces on any sail)

                    I can imagine wider hull sections aft coming into play as they are
                    immersed (more) with increasing heel, and so perhaps lifting this
                    represented midships cross section. If this is the case then the
                    data set gained from only this representative cross section would be
                    insufficient to construct a generally representative model.

                    If this is not the case it would appear that, as the boat is not
                    able to just arbitrarily "lift" by some unknown means, then the
                    assumptions made from this represented cross section are somewhat
                    erroneous and therefore any further calculations based on them are
                    also going to be in error. My calculus skills are too rusty to
                    comment on your derived equations, and the insights and intuitions
                    gained, other than to raise the point that any initial error in
                    assumptions may be compounded, perhaps more than trivially so.


                    Graeme
                  • graeme19121984
                    I meant to observe first that if there is increased area under the waterline at this cross section then that at first would appear to indicate more water being
                    Message 9 of 25 , Dec 1, 2006
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                      I meant to observe first that if there is increased area under the
                      waterline at this cross section then that at first would appear to
                      indicate more water being displaced. If more water is displaced then
                      the boat is being sunk not lifted as stated.

                      Sail heeling forces may account for the boat being pressed into the
                      water, and so the increased displacement. However the experiment
                      involved heeling the boat by shifting fishing weights athwartships
                      without dynamic sail forces, and so there seems need to explain how
                      the extra water came to be displaced when the total mass of the boat
                      remained constant.

                      Graeme

                      --- In bolger@yahoogroups.com, "graeme19121984" <graeme19121984@...>
                      wrote:
                      >
                      > Guy,
                      >
                      > at your "The Stiffness of an Advanced Sharpie" at
                      > http://faculty.valpo.edu/gvandegr/ there is this:
                      >
                      >
                      > "This axis of rotation ensures that the total area of this
                      > underwater section remains constant. Close inspection of the
                      graph
                      > indicates that the rotation slightly increases the area under the
                      > waterline. Hence the rotation is accompanied by a slight lifting
                      of
                      > the boat, which becomes important only at large angle, I believe."
                      >
                      > What lifts the boat? How is it lifted if it remains the same mass?
                      > (disregarding any lifting component of the forces on any sail)
                      >
                      > I can imagine wider hull sections aft coming into play as they are
                      > immersed (more) with increasing heel, and so perhaps lifting this
                      > represented midships cross section. If this is the case then the
                      > data set gained from only this representative cross section would
                      be
                      > insufficient to construct a generally representative model.
                      >
                      > If this is not the case it would appear that, as the boat is not
                      > able to just arbitrarily "lift" by some unknown means, then the
                      > assumptions made from this represented cross section are somewhat
                      > erroneous and therefore any further calculations based on them are
                      > also going to be in error. My calculus skills are too rusty to
                      > comment on your derived equations, and the insights and intuitions
                      > gained, other than to raise the point that any initial error in
                      > assumptions may be compounded, perhaps more than trivially so.
                      >
                      >
                      > Graeme
                      >
                    • graeme19121984
                      The more I ve pondered some emblematic examples of the extraordinarily parsimonious writing style of PCB the younger, the more I wonder at the wonder of it.
                      Message 10 of 25 , Dec 1, 2006
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                        The more I've pondered some emblematic examples of the
                        extraordinarily parsimonious writing style of PCB the younger, the
                        more I wonder at the wonder of it. The vision exchanged, much said
                        in little ink.

                        There's the old adage of a picture being worth a thousand words
                        (here too PCB excels). Ho hum, heard that before. However I find it
                        remarkable how sometimes PCB has strikingly used but a few words to
                        describe a thousand pictures.

                        For example, regarding the current discussion, I believe all to do
                        with ballast, cross sectional shape, beam, draft, length,
                        metacentric height, COG, COB, GZ, deep bulb keels, though perhaps
                        not specifically ballast moment of inertia, was REDUCED to writing
                        by PCB the younger quite some time ago. One needs perhaps be a
                        little familiar with the context where presented, and no doubt a
                        rudimentary understanding of the naval design terms also helps, but
                        once assimilated I think a reasonable approximation of almost how
                        any hull is likely to perform under press of sail can be "seen" in
                        the mind's eye when guided by PCB's enlightening insight, so well
                        expressed.

                        PCB could explain it in two sentences. I have to repeat that, in
                        two (!!) sentences:

                        "The upright stance is possible because in spite of being narrow for
                        her length, she's wide for her depth under water." (FS, p81 Rondo
                        ll); and "But regardless of her length, a boat that is deep-bodied
                        for her breadth, and doesn't carry her ballast on a deep fin, will
                        be tender under sail." (FS, p69 Blackgauntlet ll)

                        This explanation takes quite a bit of unpacking, however I believe
                        it contains all that is required - perhaps a book or two's worth.

                        (Also, when mentally considering neutral ballast hull volumes simply
                        subtract them from the overall hull shape until they are above the
                        waterline.)

                        Graeme
                      • graeme19121984
                        The more I ve pondered some emblematic examples of the extraordinarily parsimonious writing style of PCB the younger, the more I wonder at the wonder of it.
                        Message 11 of 25 , Dec 1, 2006
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                          The more I've pondered some emblematic examples of the
                          extraordinarily parsimonious writing style of PCB the younger, the
                          more I wonder at the wonder of it. The vision exchanged, much said
                          in little ink.

                          There's the old adage of a picture being worth a thousand words
                          (here too PCB excels). Ho hum, heard that before. However I find it
                          remarkable how sometimes PCB has strikingly used but a few words to
                          describe a thousand pictures.

                          For example, regarding the current discussion, I believe all to do
                          with ballast, cross sectional shape, beam, draft, length,
                          metacentric height, COG, COB, GZ, deep bulb keels, though perhaps
                          not specifically ballast moment of inertia, was REDUCED to writing
                          by PCB the younger quite some time ago. One needs perhaps be a
                          little familiar with the context where presented, and no doubt a
                          rudimentary understanding of the naval design terms also helps, but
                          once assimilated I think a reasonable approximation of almost how
                          any hull is likely to perform under press of sail can be "seen" in
                          the mind's eye when guided by PCB's enlightening insight, so well
                          expressed.

                          PCB could explain it in two sentences. I have to repeat that, in
                          two (!!) sentences:

                          "The upright stance is possible because in spite of being narrow for
                          her length, she's wide for her depth under water." (FS, p81 Rondo
                          ll); and "But regardless of her length, a boat that is deep-bodied
                          for her breadth, and doesn't carry her ballast on a deep fin, will
                          be tender under sail." (FS, p69 Blackgauntlet ll)

                          This explanation takes quite a bit of unpacking, however I believe
                          it contains all that is required - perhaps a book or two's worth.

                          (Also, when mentally considering neutral ballast hull volumes simply
                          subtract them from the overall hull shape until they are above the
                          waterline.)

                          Graeme
                        • graeme19121984
                          The more I ve pondered some emblematic examples of the extraordinarily parsimonious writing style of PCB the younger, the more I wonder at the wonder of it.
                          Message 12 of 25 , Dec 1, 2006
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                            The more I've pondered some emblematic examples of the
                            extraordinarily parsimonious writing style of PCB the younger, the
                            more I wonder at the wonder of it. The vision exchanged, much said
                            in little ink.

                            There's the old adage of a picture being worth a thousand words
                            (here too PCB excels). Ho hum, heard that before. However I find it
                            remarkable how sometimes PCB has strikingly used but a few words to
                            describe a thousand pictures.

                            For example, regarding the current discussion, I believe all to do
                            with ballast, cross sectional shape, beam, draft, length,
                            metacentric height, COG, COB, GZ, deep bulb keels, though perhaps
                            not specifically ballast moment of inertia, was REDUCED to writing
                            by PCB the younger quite some time ago. One needs perhaps be a
                            little familiar with the context where presented, and no doubt a
                            rudimentary understanding of the naval design terms also helps, but
                            once assimilated I think a reasonable approximation of almost how
                            any hull is likely to perform under press of sail can be "seen" in
                            the mind's eye when guided by PCB's enlightening insight, so well
                            expressed.

                            PCB could explain it in two sentences. I have to repeat that, in
                            two (!!) sentences:

                            "The upright stance is possible because in spite of being narrow for
                            her length, she's wide for her depth under water." (FS, p81 Rondo
                            ll); and

                            "But regardless of her length, a boat that is deep-bodied
                            for her breadth, and doesn't carry her ballast on a deep fin, will
                            be tender under sail." (FS, p69 Blackgauntlet ll)

                            This explanation takes quite a bit of unpacking, however I believe
                            it contains all that is required - perhaps a book or two's worth.

                            (Also, when mentally considering neutral ballast hull volumes simply
                            subtract them from the overall hull shape until they are above the
                            waterline.)

                            Graeme
                          • Mike French
                            When the Shearwater (larger Dovkie)was designed I believe PCB and Peter Duff thought about water ballast. They decided on lead approx 2 inches thick, glassed
                            Message 13 of 25 , Dec 1, 2006
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                              When the Shearwater (larger Dovkie)was designed I believe PCB and
                              Peter Duff thought about water ballast. They decided on lead approx 2
                              inches thick, glassed to the inside of the flat hull bottom, across to
                              the beginning of the turn of the bilge on each side and 2 feet or so
                              fore and aft. It was located at the bottom of the companionway and did
                              not interfere much. It added inertia, but good righting moment only
                              when well heeled. It represented about 500 lbs out of a total of 2200
                              lbs - which is still pretty light for a 28 footer.
                            • Guy Vandegrift
                              Graeme, You are absolutly right in observing that the lifting of the boat begins as soon as the angle deviates from zero. Hence, the linear relation between
                              Message 14 of 25 , Dec 1, 2006
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                                Graeme,

                                You are absolutly right in observing that the lifting of the boat
                                begins as soon as the angle deviates from zero. Hence, the linear
                                relation between torque and angle is never strictly true. I believe
                                (hope) that this effect is sufficiently small in most boats. This
                                needs to be checked, either numerically or experimentally.

                                Regarding your second comment, we didn't add the fishing weights, but
                                shifted them "leeward" from the "windward" side. There was no "wind"
                                of course, and the actual force of the sails on the boat are
                                complicated and dynamic. Though unable to model all complexities, I
                                believe our experiment exactly matched what computer stability codes do.

                                Enjoyed your commentary,

                                Guy
                              • Patric Albutat
                                Since the dreaded stability question has been raised again, here s a link I came about (after the last discussion ended in a fierce battle over multihulls -
                                Message 15 of 25 , Dec 1, 2006
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                                  Since the dreaded 'stability question' has been raised again, here's a
                                  link I came about (after the last discussion ended in a fierce battle
                                  over multihulls - guess I'll have to pick my words more carefully):
                                  http://www.boatdesign.com/postings/pages/knockdown.htm
                                  If everybody knows already, sorry!

                                  My search for rightening moment actually reveiled not only that a flat
                                  boat without any keel at all can still be a very seaworty vessel, it
                                  has been done for more than 3000 years:
                                  http://www.flickr.com/photos/67816918@N00/sets/72157594372244167

                                  As for internal ballast: the British Navy (Nelson's Navy that is) used
                                  shingle

                                  Patric
                                • Guy Vandegrift
                                  Patric, No need to apologize about the Junk photos. I have long looked for something like this. And I forgive you for reposting the well known, but classic,
                                  Message 16 of 25 , Dec 1, 2006
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                                    Patric, No need to apologize about the Junk photos. I have long
                                    looked for something like this. And I forgive you for reposting the
                                    well known, but classic, link on Bolger Box knockdowns.

                                    Guy

                                    --- In bolger@yahoogroups.com, "Patric Albutat" <albutat@...> wrote:
                                    > http://www.boatdesign.com/postings/pages/knockdown.htm
                                    > If everybody knows already, sorry!
                                    >
                                    > My search for rightening moment actually reveiled not only that a flat
                                    > boat without any keel at all can still be a very seaworty vessel, it
                                    > has been done for more than 3000 years:
                                    > http://www.flickr.com/photos/67816918@N00/sets/72157594372244167
                                  • graeme19121984
                                    Guy, I m missing something here. How can the boat lift in static conditions when the mass is unchanged. Lift defined by displacing less water. How is the
                                    Message 17 of 25 , Dec 1, 2006
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                                      Guy,

                                      I'm missing something here. How can the boat lift in static
                                      conditions when the mass is unchanged. "Lift" defined by displacing
                                      less water. How is the boat made lighter?

                                      By the way, please keep on inquiring. Very interesting work.

                                      Graeme

                                      PS Sorry group for three repetitive posts above. Not sure how that
                                      happened - I hit stop after send, once, as I wanted to edit
                                      something.

                                      --- In bolger@yahoogroups.com, "Guy Vandegrift" <guy.vandegrift@...>
                                      wrote:
                                      >
                                      > Graeme,
                                      >
                                      > You are absolutly right in observing that the lifting of the boat
                                      > begins as soon as the angle deviates from zero. Hence, the linear
                                      > relation between torque and angle is never strictly true. I believe
                                      > (hope) that this effect is sufficiently small in most boats. This
                                      > needs to be checked, either numerically or experimentally.
                                    • Guy Vandegrift
                                      Ouch! You caught me being vague and sloppy in my language. When one chine goes down, the other one comes up. But in my defense, the center of the bottom does
                                      Message 18 of 25 , Dec 1, 2006
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                                        Ouch! You caught me being vague and sloppy in my language. When one
                                        chine goes down, the other one comes up. But in my defense, the
                                        center of the bottom does "lift" up.

                                        I developed this insight when I was building Michalak's 4'x12' Piccup
                                        Pram. I saw these 4'x8' Styrofoam slabs (maybe 3" thick) in a home
                                        improvement store and wondered how one would behave if it rested
                                        (empty) on water. 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.

                                        A typical Advanced Sharpie might resemble this slab. When I first
                                        started looking at boat hulls on the internet, I was surprized by the
                                        shallow draft.

                                        --- In bolger@yahoogroups.com, "graeme19121984" <graeme19121984@...>
                                        wrote:
                                        >
                                        > Guy,
                                        >
                                        > I'm missing something here. How can the boat lift in static
                                        > conditions when the mass is unchanged. "Lift" defined by displacing
                                        > less water. How is the boat made lighter?
                                        >
                                      • 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 19 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 20 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 21 of 25 , Dec 4, 2006
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                                              Hmmm..... ten times nothing is ... NOTHING!
                                              Bob


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                                              [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 22 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 23 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 24 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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