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Re: Isometric of Bolger's 1 Man live-aboard concept.

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  • prairiedog2332
    Fred, Have you seen this? http://groups.yahoo.com/group/bolger_study_plans_only/files/Small%20Moto rsailer/ Sort of a scaled down version of the Alaskan Motor
    Message 1 of 13 , Sep 1, 2010
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      Fred,

      Have you seen this?

      http://groups.yahoo.com/group/bolger_study_plans_only/files/Small%20Moto\
      rsailer/

      Sort of a scaled down version of the Alaskan Motor Sailor. I think the
      box keel creates too much wetted surface to make for good sailing
      performance in a hull this short, but is an ideal location for a tiny
      diesel engine. This cartoon also points out another disadvantage - lack
      of storage space - mainly due to the deadrise in the hull shape.
      Anything stored in the box keel - you lose standing headroom there.

      Nels

      --- In bolger@yahoogroups.com, Fred Schumacher <fredschum@...> wrote:
      >
      > On Tue, Aug 24, 2010 at 3:43 PM, Bruce Hallman hallman@... wrote:
      >
      > >
      > >
      > > http://hallman.org/bolger/1man/
      > >
      > > This has long been one of my favorite Bolger designs, for several
      > > reasons. It simply crams in maximum capability into minimum space,
      > > with a strong emphasis on function. 19 feet x 7'6" means it is a
      > > modest project to tackle, and to keep up and berth.
      > >
      >
      > Bruce,
      >
      > Was this a design from Phil's pre-box days, before he abandoned
      complex
      > curves for the possibilities of parsimony? I thought it a good mental
      > exercise to take this concept and apply it to the more space
      utilization
      > efficient Micro and see what comes up.
      >
      > By replacing Micro's salient keel with a narrow, two foot wide box
      keel
      > under a 9/8ths scale up of Micro, it's possible to achieve the
      functionality
      > of the One Man boat in a smaller (17.5 x 6.75 x2) boat that would be
      easier
      > to build. It would have standing headroom, without the need of a pilot
      > house, two berths, galley and head with shower space, room for a
      Tortoise on
      > top and 7 feet of cockpit, 50 gallons tankage and 75 cubic feet of
      storage.
      >
      > I think whole books could be written about the possibilities of the
      Micro
      > form factor.
      >
      > fred s.
      >
    • Fred Schumacher
      ... Yes, I have seen this, and it s what originally got me to thinking about the benefits of a box keel. If a box keel has the same profile as a salient keel,
      Message 2 of 13 , Sep 2, 2010
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        On Wed, Sep 1, 2010 at 1:25 PM, prairiedog2332 <arvent@...> wrote:
         

        Fred,

        Have you seen this?

        http://groups.yahoo.com/group/bolger_study_plans_only/files/Small%20Moto\
        rsailer/


        Sort of a scaled down version of the Alaskan Motor Sailor. I think the
        box keel creates too much wetted surface to make for good sailing
        performance in a hull this short, but is an ideal location for a tiny
        diesel engine. This cartoon also points out another disadvantage - lack
        of storage space - mainly due to the deadrise in the hull shape.
        Anything stored in the box keel - you lose standing headroom there.

        Nels

        Yes, I have seen this, and it's what originally got me to thinking about the benefits of a box keel.

        If a box keel has the same profile as a salient keel, it has virtually the same wetted area, especially if its on a box boat. The two sides of the box keel are the same as the two sides of the salient keel; the bottom of the keel replaces the bottom of the main hull. The added area comes from curvature and, when following Bolger's pressure equalizing "Sea of Peas" formula, more area toward the bow of the boat, since it would not have the "drag" (cut away forefoot) of the salient keel.

        As you note, several problems enter because of the deadrise hull. There is less lateral plane (only 9") because of the deadrise coming down to meet the box keel, and the dead rise hull has nearly the same inefficiency of space utilization as a complex curved boat. It would pound less than a box boat, especially in a chop or at anchor.

        The box form provides so much usable space that a much smaller boat becomes functional. There  is also more lateral plane, since the box keel extends lower below the main hull. A narrower box keel would also provide more lateral resistance. On Bolger's boat, it's 2.5 feet; on my sketch I kept it at 2 feet. A box keel is a totally submerged body and would act somewhat like a submarine. It would not create the same wave making resistance as a surface body of equal displacement. I wonder if a bulbous bow would be useful.

        A center cockpit boat can use a box keel to great advantage. Tankage can be placed under the cockpit. As for placing the engine in the box keel, I like the direction Phil and Susanne have gone with the use of lightweight air cooled diesels placed above the water line with sail outdrives. They used Deutz engines. I think for smaller boats, another German manufacturer, Hatz, makes a nice line of small, lightweight industrial diesels that would work. Their vertical shaft models could be mated to an outboard's lower unit.

        The box keel allows for reduction of top hamper and replacement of lead ballast with cheap steel plate that also protects the bottom and lowers the center of gravity. Over the past few years, Phil and Susanne moved away from the full length box keel, only retaining the cutwater portion. Perhaps they discovered some serious problems with it. However, I'm thinking of knocking together a quick and dirty 5/8 scale test boat (10.5' x 4' x 1.2', 700# estimated displacement) just to see how a box keel Micro would act.

        fred s.





      • Bruce Hallman
        ... One of the benefits I get from modeling a whole bunch of Bolger boats, is that I sometimes get glimpses into the thought process of PCB and PB&F as
        Message 3 of 13 , Sep 2, 2010
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          > Yes, I have seen this, and it's what originally got me to thinking about the benefits of a box keel.

          One of the benefits I get from modeling a whole bunch of Bolger
          boats, is that I sometimes get glimpses into the thought process of
          PCB and PB&F as he/they worked out trade-offs that go into the
          development of their design ideas. To me, the biggest issue that
          comes up with box keels is the effect on hull displacement and mass.

          Fundamentally, the AS-29 is an extreme case of box keel. And, the
          AS-29 needs lots of ballast to make her settle down into her
          waterline. If the AS-29 was reconfigured where the hull bottom was
          to be stepped with a box keel, the biggest thing that would change
          would be the amount of ballast.
        • Fred Schumacher
          ... Bruce, I want you to know how much I look forward to every new model you post. They re fascinating, and I think all of us here appreciate what you are
          Message 4 of 13 , Sep 2, 2010
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            On Thu, Sep 2, 2010 at 10:05 AM, Bruce Hallman <hallman@...> wrote:

            One of the benefits I get from modeling a whole bunch of Bolger
            boats, is that I sometimes get glimpses into the thought process of
            PCB and PB&F

            Bruce,

            I want you to know how much I look forward to every new model you post. They're fascinating, and I think all of us here appreciate what you are doing.

            If the AS-29 was reconfigured where the hull bottom was
            to be stepped with a box keel, the biggest thing that would change
            would be the amount of ballast.

            That's exactly right. A box keel is a submerged body, and even a narrow one displaces a lot of water. Total displacement goes up, even with the main hull floating higher, and more ballast would need to be added. The benefit of the box keel is that that ballast can be inexpensive steel plate which also protects the bottom and is located at the lowest possible point on the boat, lowering the center of gravity.

            fred s.

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