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[bolger] Re: sharpie stability/recovery

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  • Richard
    ... A long, narrow, flat bottom boat would be very fast. Of course, you would have an interesting time turning it, to say nothing of trying to go through
    Message 1 of 12 , Jan 30, 2000
      Ron Badley wrote:

      >
      > > Why this? The more I read, the more beaminess seems like a liability.
      > > I'm beginning to suspect boat are made wide so as to make them easy
      > > to sell, not easy to sail. I can't help but wonder what you end up
      > > with if you design for maximum, rather than minimum waterline.
      > >
      > > Anyone want to kick this around?
      >
      >

      A long, narrow, flat bottom boat would be very fast. Of course, you would
      have an interesting time turning it, to say nothing of trying to go through
      stays.

      The beaminess is what give it the stability, that's why the hulls of a cat
      are so far apart. Mine is 5 ft wide and 20 ft long, for a 4:1 length to beam
      ratio. Say you went to the extreme, 3 feet wide and 30 feet long. Basicaly a
      very long canoe. It would be pretty fast, but very hard to turn. If you
      increase rocker to improve turning, you loose waterline....
    • Giuseppe 'Pippo' Bianco
      David, you may want to read this nice article by Bruce Kirby http://www.coastalcruising.com/shallow.htm Very instructive! Best, Pippo david ryan
      Message 2 of 12 , Feb 1, 2000
        David,
        you may want to read this nice article by Bruce Kirby

        http://www.coastalcruising.com/shallow.htm

        Very instructive!
        Best, Pippo

        david ryan <davi-@...> wrote:
        original article:http://www.egroups.com/group/bolger/?start=2150
        > FBBB --
        >
        > I've been thinking a lot about stability and recovery, and studying
        > BWAOM very hard, especially the AS29 and LooseMoose. I think I'm
        > finally starting to get the shallow draft/high freeboard concept.
        >
        > Having spent my whole life sailing dingies, I have always equated
        > stability with hiking over the side, and maybe a weighed
        > centerboard. Recovery meant standing on the centerboard and prying
        > the thing back to upright. In a larger boat, this seemed to
        > *obviously* indicate the necessity of deep keels and heavy ballast.
        >
        > The AS29 and LM (if I understand correctly,) seem to prove otherwise,
        > and I am very intrigued.
        >
        > I've spent the weekend imaging a crusing sharpie that takes the
        > concept to extremes -- a very long, very slender craft sporting a low
        > sail plan and high freeboard: sort of like an extrastretched
        > tarantula (minus the keel) with a multi-mast sail plan and high
        > topsides. At what point is the beam to freeboard ratio optimized?
        >
        > Why this? The more I read, the more beaminess seems like a liability.
        > I'm beginning to suspect boat are made wide so as to make them easy
        > to sell, not easy to sail. I can't help but wonder what you end up
        > with if you design for maximum, rather than minimum waterline.
        >
        > Anyone want to kick this around?
        >
        > YIBB,
        >
        > David Ryan
        > Minister of Information and Culture
        > Crumbling Empire Productions
        > (212) 247-0296
      • David Ryan
        ... very stable right side up, very stable upside down. David Ryan Minister of Information and Culture Crumbling Empire Productions (212) 247-0296
        Message 3 of 12 , Feb 1, 2000
          >
          >
          >
          > You'll end up with a multihull ;-)
          >
          >Ron
          >Kismet 31 "Big Bird" (trimaran, building a cat)

          very stable right side up, very stable upside down.

          David Ryan
          Minister of Information and Culture
          Crumbling Empire Productions
          (212) 247-0296
        • Peter Vanderwaart
          David, Moderation in all things. Note that despite its boxy shape, the AS-29 is petty close to ordinary beam and weight for its length. The overall beam is
          Message 4 of 12 , Feb 1, 2000
            David,

            Moderation in all things. Note that despite its boxy shape, the AS-29
            is petty close to ordinary beam and weight for its length. The overall
            beam is perhaps less than average (due to having no flare), but the
            waterline beam is in the ordinary range.

            I think of these sharpies as being sort of like a banana, floating
            'convex down.' The rocker, which has virtues Mr. Bolger talks about
            with respect to flow, works with respect to stability by giving the
            boat a low belly, in which to put some ballast, and high ends. In a
            knockdown, the high ends move the center of buoyancey away from the
            ballast, giving a high righting moment (i.e. high reserve stability).
            However, this sort of stability does not give much sail carrying power
            at small angles of heel.

            The sail carrying power comes from hull sections with a lot of form
            stability, i.e. the box cross section, which depends on having adequate
            beam.

            If you take a small boat, and simply build it longer with the same
            beam, the resulting hull can carry more sail area in proportion to its
            length, but it can not carry it higher. As the boat gets longer and
            longer, the rig must stay the same height. As you go from one mast to
            two or three masts (remember Rondo II?), the aerodynamic effeciency
            suffers.

            That's my view, anyway.

            Peter

            >
            > I've been thinking a lot about stability and recovery, and studying
            > BWAOM very hard, especially the AS29 and LooseMoose. I think I'm
            > finally starting to get the shallow draft/high freeboard concept.
            >
          • ed haile
            David, Another aspect of all this, namely high freeboard. I had long objected to high sided boats as being such for the sake of too much downstairs at the
            Message 5 of 12 , Feb 1, 2000
              David,

              Another aspect of all this, namely high freeboard. I had long objected
              to high sided boats as being such for the sake of too much "downstairs"
              at the cost of excessive windage topside. A look at the oldtime
              galleons and it's obvious they were exclusively downwind sailers. But
              then something struck me in the Bolger boats. Look at the X-section of
              a box boat. It's just about square. That means that windage (despite
              the high sides) does not substantially increase or diminish with heel.
              What's more, a square section (vertical sides) becomes more streamlined
              when it heels (angled side facing the wind). Now look at your standard
              dinghy, fin keel yacht. On an even keel most of them are very low. But
              when they heel they throw up that ole weather rail and effectively have
              the same windage as one of your box boats, if not more, and, since you
              can see underneath, are much less streamlined.

              Ever notice how in yacht photos you almost never see a picture of a
              heeling yacht taken from windward.

              Hull windage is an advantage downwind, precisely where standard brands
              have the least, riding on an even keel. Windage is a disadvantage
              upwind, precisely where standard brands develop it when they heel. So,
              I became convinced that high freeboard was not a bad idea from a
              windage standpoint, and from there to Bolger's statement that shallow
              draft requires high freeboard.

              To say nothing of rigging windage.

              I am not yacht designer, and I admit in my lifetime on the water in
              boats I have learned next to nothing. The above simply reasons from
              facts & lines on paper. On the other hand, my Martha Jane pretty much
              bears it all out.

              Ed Haile
            • peter lenihan
              Hello Ed, I never quite saw it that way but it sure does make a whole lot of sense,thanks!Now I have a wonderful arguement to give to all of my infidel friends
              Message 6 of 12 , Feb 1, 2000
                Hello Ed,
                I never quite saw it that way but it sure does make a whole lot of sense,thanks!Now I have a wonderful arguement to give to all of my infidel friends without having to take them out for a sail on my Micro.
                Despite the high sides of my Micro,I have never felt blown sideways since that lovely long keel just keeps on biting and biting long after the centerboarders and finkeelers have blown out of range!
                Regards
                Peter Lenihan


                --- ed haile <bolger@egroups.com> wrote:
                >David,
                >
                >Another aspect of all this, namely high freeboard. I had long objected
                >to high sided boats as being such for the sake of too much "downstairs"
                >at the cost of excessive windage topside. A look at the oldtime
                >galleons and it's obvious they were exclusively downwind sailers. But
                >then something struck me in the Bolger boats. Look at the X-section of
                >a box boat. It's just about square. That means that windage (despite
                >the high sides) does not substantially increase or diminish with heel.
                >What's more, a square section (vertical sides) becomes more streamlined
                >when it heels (angled side facing the wind). Now look at your standard
                >dinghy, fin keel yacht. On an even keel most of them are very low. But
                >when they heel they throw up that ole weather rail and effectively have
                >the same windage as one of your box boats, if not more, and, since you
                >can see underneath, are much less streamlined.
                >
                >Ever notice how in yacht photos you almost never see a picture of a
                >heeling yacht taken from windward.
                >
                >Hull windage is an advantage downwind, precisely where standard brands
                >have the least, riding on an even keel. Windage is a disadvantage
                >upwind, precisely where standard brands develop it when they heel. So,
                >I became convinced that high freeboard was not a bad idea from a
                >windage standpoint, and from there to Bolger's statement that shallow
                >draft requires high freeboard.
                >
                >To say nothing of rigging windage.
                >
                >I am not yacht designer, and I admit in my lifetime on the water in
                >boats I have learned next to nothing. The above simply reasons from
                >facts & lines on paper. On the other hand, my Martha Jane pretty much
                >bears it all out.
                >
                >Ed Haile
                >
                >
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              • David Ryan
                FBBB -- I m glad I asked. My understanding continues to grow. A couple of thoughts/questions: 1) As I said before, I am convinced that *most* boats are
                Message 7 of 12 , Feb 1, 2000
                  FBBB --

                  I'm glad I asked. My understanding continues to grow.

                  A couple of thoughts/questions:

                  1) As I said before, I am convinced that *most* boats are designed
                  with salability, not sailabilitly as their primary design
                  consideration. I think what has impressed my most about BWAOM is that
                  PCB is willing to realistically consider the way a boat will actually
                  be used. His comment about LM spending more time in port than in
                  ocean crossing, and then the resulting design really spoke to me. On
                  the other hand, since most boats spend most of their time tied up,
                  maybe a imitation offshore racer sponsors (that you don't actually
                  sail) sponsors more satisfying fantasies than a big Bolger box (that
                  you don't actually sail.) People sure get a big kick out of driving
                  SUVs will never see a dirt trail.

                  2) Tacking: Given similiar waterlines/rocker, is a narrower boat
                  harder to tack? Or is it simply that longer boats are harder to turn?
                  And besides, how often do you tack your LM on a trip from France to
                  Jamaica?

                  3) Multi-masts/Aero efficiency. As I understand it, multiple masts
                  are an answer to the practical limits of mast height, i.e. clippers
                  couldn't got as high as they wanted, so they went wide. Is this a
                  correct understanding? If it isn't, what is correct. If it is, where
                  are the practical lower limits (of hull size) of many small masts vs.
                  one big one?

                  What I am envisioning is a very long, very lean cruiser. She'd have
                  less sail, less beam, and more waterline. Doesn't tack very well? Who
                  cares, I'm on a beam reach for the next 1500 miles! No deep heavy
                  keel? If I can't get the nose into the wind and a sea anchor out,
                  I'll ride out the blow on my side (like Kerby's timber carrying
                  schooner,) confident my topsides will keep my from going any further.

                  Has Bolger or anyone else designed such a beast? If so, what are her
                  strengths? faults?

                  YIBB,


                  David Ryan
                  Minister of Information and Culture
                  Crumbling Empire Productions
                  (212) 247-0296
                • ed haile
                  ... I think the issue here is maneuverability, something you don t give up lightly. ... The limit is sail size vs crew. Not mast height. Clippers had masts
                  Message 8 of 12 , Feb 1, 2000
                    > 2) Tacking: how often do you tack your LM on a trip from France to
                    > Jamaica?

                    I think the issue here is maneuverability, something you don't give up
                    lightly.

                    >
                    > 3) Multi-masts/Aero efficiency. As I understand it, multiple masts
                    > are an answer to the practical limits of mast height, i.e. clippers
                    > couldn't got as high as they wanted, so they went wide. Is this a
                    > correct understanding? If it isn't, what is correct. If it is, where
                    > are the practical lower limits (of hull size) of many small masts vs.
                    > one big one?

                    The limit is sail size vs crew. Not mast height. Clippers had masts
                    plenty high. But compare them to what went before and you see much
                    taller masts together with much smaller sails. They furled more than
                    they reefed and some prefer that on our-size boats. I think the Jochems
                    schooner has a lot of sails for an under-25 footer. Some might think
                    the main on a Loose Moose is a monster.

                    >
                    > What I am envisioning is a very long, very lean cruiser. She'd have
                    > less sail, less beam, and more waterline. Doesn't tack very well? Who
                    > cares, I'm on a beam reach for the next 1500 miles! No deep heavy
                    > keel? If I can't get the nose into the wind and a sea anchor out,
                    > I'll ride out the blow on my side (like Kerby's timber carrying
                    > schooner,) confident my topsides will keep my from going any further.

                    You might consider comfort important too, after a couple of blows. But
                    maneuverability.

                    >
                    > Has Bolger or anyone else designed such a beast? If so, what are her
                    > strengths? faults?
                    >
                    > YIBB,

                    The very question I put to PCB years ago: how about a long low-rig
                    sailing canoe? He referred me to the folding schooner. If he has
                    designed a proa since then, he might now mention that.

                    > David Ryan
                    > Minister of Information and Culture
                    > Crumbling Empire Productions
                    > (212) 247-0296
                  • Wmrpage@aol.com
                    How about this concept? Sail power is only required for those long hauls from Bermuda to the Azores, Canaries to Carribean - all down-hill sailing. Why use a
                    Message 9 of 12 , Feb 3, 2000
                      How about this concept? Sail power is only required for those long hauls from
                      Bermuda to the Azores, Canaries to Carribean - all down-hill sailing. Why use
                      a conventional rig, requiring a substantial righting moment (ballast or beam
                      = expense), if there was an alternative? My thought is of a reasonably long,
                      narrow, lightly balanced "box" suitable for low-powered internal combustion
                      engine operation in coastal waters, inland waters and canals, just
                      sufficiently ballasted for self-righting, with hatches amidship, etc. for
                      off-shore survivability. For the ocean crossings, one would use some form of
                      traction kites. Thrust from the kite could be taken at the rail by snatch
                      blocks. ( very low c.e. = low stability requirement for thrust developed).
                      Sail area ( I get the impression that projecting adequate non-chafing
                      downwind sail area in the Trades can be a problem with conventional boats)
                      would be independent of mast dimensions (low windage, low cost, low clearance
                      in canals). My perusal of traction kiting websites (e.g.
                      DaveCulpSpeedSailing) hasn't done much to dispel my ignorance of how such
                      kites are deployed and managed, but it does seem to me that they could
                      develop as much power as one could desire on courses up to at least a broad
                      reach with minimal heeling force. A buttoned-up hull of "Tennessee" or
                      "Wyoming" type dimensions (provided with some appendage to provide a suitable
                      CLR) might be one hell of a downwind sled.

                      Bill Page in the land of HARD water (MN)
                    • tjfatchen@ace.net.au
                      BO Another aspect of all this, namely high freeboard. I had long objected BO to high sided boats as being such for the sake of too much downstairs BO at the
                      Message 10 of 12 , Mar 11, 2000
                        BO>Another aspect of all this, namely high freeboard. I had long objected
                        BO>to high sided boats as being such for the sake of too much "downstairs"
                        BO>at the cost of excessive windage topside.
                        <snip>
                        BO>I became convinced that high freeboard was not a bad idea from a
                        BO>windage standpoint, and from there to Bolger's statement that shallow
                        BO>draft requires high freeboard.

                        BO>Ed Haile

                        I was originally alarmed at the windage possibilities of the AS29 hull,
                        particularly given the necessity to get out of tight and narrow marinas
                        (and back in) at dead slow speeds with vicious crosswinds. We did have
                        windage problems, in particular the bow falling off, but all to do with
                        the windage of the mainmast (which is quite respectable). The hull
                        itself, with boards down, is close to neutral.

                        Now, if they'd allow us to sail in and out of marina, we wouldnt have
                        any trouble at all....

                        Tim & Lady Kate
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