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Re: [bolger] Flat / curved ?

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  • Bruce Hallman
    Most of the Bolger square boats IE, those in the Advanced Sharpie series, and others, actually are not flat bottomed, but rather they are very much curved.
    Message 1 of 10 , Jun 2, 2004
      Most of the Bolger 'square boats' IE, those in the
      Advanced Sharpie series, and others, actually are not
      flat bottomed, but rather they are very much curved.

      [The exception are a few of his boats that are
      intended to be planing boats, like Wyoming,
      or Sneakeasy.]

      These 'Square Boats' look 'flat' because they are made from
      bent sheets of plywood. They bend in only two dimensions
      rather than three.

      Bolger's concept for these 'square' boats is that if
      he designs the curve of the sides to match the
      curve of the bottom, then there is no differential
      pressure as the water flows around the boat. The
      particles of water have equal distance to travel
      without regard as they flow across the bottom
      or the side.

      If the curve of the bottom did not match the sides
      then the differential pressure of the flowing water
      would 'suck' water across the chine edges between
      the bottom and the sides. This turbulence would
      be detrimental to the performence of the boats.

      Boats that have curves in three directions rather
      than two directions also are intended to reduce this
      turbulence from differential pressure of the flowing
      water, but they achieve this by having gradual changes
      in the directions and distances of the flow of water.

      On Wed, 02 Jun 2004 21:49:43 -0000, alternateuser2001
      <alternateuser2001@...> wrote:
      >
      >
      > Hi there ,
      >
      > 'Got a question for you all - can anyone explain to me why
      > the 'classic' boats all have a 'curved' underside (aiii...what a
      > terrible terminology to USE , dutchman ...and that to a boatbuilding
      > group ... Go wash your mouth with some soap !! ) While the boats from
      > Mr.Bolger (and other modern boats) often have a much more "flatt"
      > one ??
      > I DO know that it would be much better to take up some sort a course
      > in 'elementary shipbuilding' or something like that, and I will in
      > due time...but I just was curious .
      > Allready I know (by studying the texts and articles from this great
      > site (!) that my own little "shanty-boat' / 'narrow-boat' is gonna
      > get a flatbottom - she will be going very slowly through very calm
      > water, with allmost no deep water at all ... So that will do just
      > fine then .
      >
      > If anyone would be so kind as to explain this a little I would be
      > very gratefull for that.
      > Also my earlier offer; to be willing to search for anything "Dutch-
      > related" still stands, ok ?!
      >
      > Sincere greetings,
      >
      > M.Hulleman
      >
      >
      > Bolger rules!!!
      > - no cursing, flaming, trolling, spamming, or flogging dead horses
      > - stay on topic, stay on thread, punctuate, no 'Ed, thanks, Fred' posts
      > - Pls add your comments at the TOP, SIGN your posts, and snip away
      > - Plans: Mr. Philip C. Bolger, P.O. Box 1209, Gloucester, MA, 01930, Fax: (978) 282-1349
      > - Unsubscribe: bolger-unsubscribe@yahoogroups.com
      > - Open discussion: bolger_coffee_lounge-subscribe@yahoogroups.com
      > Yahoo! Groups Links
      >
      >
      >
      >
      >
    • doug6949
      The greatest volume you can enclose for a particular surface area will be in the shape of a circle. Thus, round bottom boats minimize the amount of skin
      Message 2 of 10 , Jun 2, 2004
        The greatest volume you can enclose for a particular surface area will
        be in the shape of a circle. Thus, round bottom boats minimize the
        amount of skin friction. Additionally, they minimize turbulance if
        designed correctly.

        Flat bottomed hulls have higher initial stability. They don't roll as
        much. Most important, they are easier to build. And least important,
        from Bolger's point of view, they tend to be ugly.

        Doug

        --- In bolger@yahoogroups.com, "alternateuser2001"
        <alternateuser2001@y...> wrote:
        >
        > Hi there ,
        >
        > 'Got a question for you all - can anyone explain to me why
        > the 'classic' boats all have a 'curved' underside ... While the
        boats from
        > Mr.Bolger (and other modern boats) often have a much more "flatt"
        > one ??
      • alternateuser2001
        Thank you very much !! Wow ! that cleared up a LOT , for me that is - the whole hull-form issue s much more clear now . And how logical it is, when you
        Message 3 of 10 , Jun 2, 2004
          Thank you very much !! Wow ! that cleared up a LOT , for me that is -
          the whole "hull-form" issue 's much more clear now . And how logical
          it is, when you think of it; what would move the easiest through
          water - a square block or a needle ?! (why didn't I think of
          that ...;)Thanks!

          But that leaves me with the question: for a sort-of "narrow-like-
          shanty-boat", the flatt hull ( 'box-style' they call it
          at 'cimplicityboats') like f.o. off Bolger's Tennessee , isn't a good
          idea ,because this boat isn't going to plane over the water...??
        • pvanderwaart
          There are many complicating factors, and many different ideas. Boat shape questions do not have single answers. The weight of the boat is an important factor.
          Message 4 of 10 , Jun 2, 2004
            There are many complicating factors, and many different ideas. Boat
            shape questions do not have single answers.

            The weight of the boat is an important factor. The lighter a boat is,
            the flatter the bottom will be. A light boat can't push a rounded
            shape deep enough into the water. Tenessee is very light for her
            size. Bolger uses a very flat bottom so the boat does not go deep in
            the water. It only has to push a little surface water aside as it
            moves along. (And it is an easy shape to build.)

            A shanty boat built on a barge-like shape will have a flat bottom
            because it is easy to build and will float in shallow water. It will
            never go anywere fast, so the shape does not have to be very
            boatlike. The flat bottom will also rock the least.

            Peter

            --- In bolger@yahoogroups.com, "alternateuser2001"
            <alternateuser2001@y...> wrote:
            >
            > Thank you very much !! Wow ! that cleared up a LOT , for me that
            is -
            > the whole "hull-form" issue 's much more clear now . And how
            logical
            > it is, when you think of it; what would move the easiest through
            > water - a square block or a needle ?! (why didn't I think of
            > that ...;)Thanks!
            >
            > But that leaves me with the question: for a sort-of "narrow-like-
            > shanty-boat", the flatt hull ( 'box-style' they call it
            > at 'cimplicityboats') like f.o. off Bolger's Tennessee , isn't a
            good
            > idea ,because this boat isn't going to plane over the water...??
          • alternateuser2001
            Thanks people ... that s a LOT of info, a lot to think about as well. I m off to make some planns and sketches ! Thanks again . Sincere greetings, M.Hulleman
            Message 5 of 10 , Jun 2, 2004
              Thanks people ...
              that 's a LOT of info, a lot to think about as well.
              I'm off to make some planns and sketches !

              Thanks again .


              Sincere greetings,

              M.Hulleman
            • craig o'donnell
              ... But there are also Dutch boats with flat bottoms! -- Craig O Donnell Sinepuxent Ancestors & Boats The
              Message 6 of 10 , Jun 2, 2004
                >If anyone would be so kind as to explain this a little I would be
                >very gratefull for that.
                >Also my earlier offer; to be willing to search for anything "Dutch-
                >related" still stands, ok ?!
                >
                >Sincere greetings,
                >
                >M.Hulleman

                But there are also Dutch boats with flat bottoms!
                --
                Craig O'Donnell
                Sinepuxent Ancestors & Boats
                <http://freepages.genealogy.rootsweb.com/~fassitt/>
                The Proa FAQ <http://boat-links.com/proafaq.html>
                The Cheap Pages <http://www.friend.ly.net/~dadadata/>
                Sailing Canoes, Polytarp Sails, Bamboo, Chinese Junks,
                American Proas, the Bolger Boat Honor Roll,
                Plywood Boats, Bamboo Rafts, &c.
                _________________________________

                -- Professor of Boatology -- Junkomologist
                -- Macintosh kinda guy
                Friend of Wanda the Wonder Cat, 1991-1997.
                _________________________________
              • craig o'donnell
                ... If a boat is going to go very slow, then the barge shape: or scow shape is no problem. When scow shapes are very large they are very efficient load
                Message 7 of 10 , Jun 2, 2004
                  >But that leaves me with the question: for a sort-of "narrow-like-
                  >shanty-boat", the flatt hull ( 'box-style' they call it
                  >at 'cimplicityboats') like f.o. off Bolger's Tennessee , isn't a good
                  >idea ,because this boat isn't going to plane over the water...??

                  If a boat is going to go very slow, then the "barge shape: or "scow shape"
                  is no problem. When scow shapes are very large they are very efficient load
                  carriers. Keep the transom out of the water. In the case of the scow keep
                  both transoms out of the water.

                  There is another reason for flat bottom boats. In the USA, many small
                  working boats were "crossplanked" that is the boards on the bottom were
                  nailed across. This makes for an easily built, cheap and very strong hull.
                  Sometimes there is a little "V" to the bottom but the principle remains the
                  same.

                  Cheap and strong is what the fishermen wanted.


                  --
                  Craig O'Donnell
                  Sinepuxent Ancestors & Boats
                  <http://freepages.genealogy.rootsweb.com/~fassitt/>
                  The Proa FAQ <http://boat-links.com/proafaq.html>
                  The Cheap Pages <http://www.friend.ly.net/~dadadata/>
                  Sailing Canoes, Polytarp Sails, Bamboo, Chinese Junks,
                  American Proas, the Bolger Boat Honor Roll,
                  Plywood Boats, Bamboo Rafts, &c.
                  _________________________________

                  -- Professor of Boatology -- Junkomologist
                  -- Macintosh kinda guy
                  Friend of Wanda the Wonder Cat, 1991-1997.
                  _________________________________
                • Roger Derby
                  One other issue with flat surfaces -- they oil can. By introducing a curve (aka arch) the stresses do not reverse and the material/structure lasts longer.
                  Message 8 of 10 , Jun 2, 2004
                    One other issue with flat surfaces -- they "oil can." By introducing a
                    curve (aka arch) the stresses do not reverse and the material/structure
                    lasts longer.

                    Roger
                    derbyrm@...
                    derbyrm.mystarband.net/default.htm

                    ----- Original Message -----
                    From: "pvanderwaart" <pvanderwaart@...>
                    >
                    > There are many complicating factors, and many different ideas. Boat
                    > shape questions do not have single answers.
                    >
                    > The weight of the boat is an important factor. The lighter a boat is,
                    > the flatter the bottom will be. A light boat can't push a rounded
                    > shape deep enough into the water. Tenessee is very light for her
                    > size. Bolger uses a very flat bottom so the boat does not go deep in
                    > the water. It only has to push a little surface water aside as it
                    > moves along. (And it is an easy shape to build.)
                    >
                    > A shanty boat built on a barge-like shape will have a flat bottom
                    > because it is easy to build and will float in shallow water. It will
                    > never go anywere fast, so the shape does not have to be very
                    > boatlike. The flat bottom will also rock the least.
                    >
                    > Peter
                  • grant corson
                    One good reason would be a softer ride, no pounding, however if you are building a slow moving flat bottomed boat you wont need to be concerned too much about
                    Message 9 of 10 , Jun 2, 2004
                      One good reason would be a softer ride, no pounding, however if you are
                      building a slow moving flat bottomed boat you wont need to be concerned too
                      much about it....
                      Grant
                      on 6/2/04 5:49 PM, alternateuser2001 at alternateuser2001@... wrote:

                      >
                      > Hi there ,
                      >
                      > 'Got a question for you all - can anyone explain to me why
                      > the 'classic' boats all have a 'curved' underside (aiii...what a
                      > terrible terminology to USE , dutchman ...and that to a boatbuilding
                      > group ... Go wash your mouth with some soap !! ) While the boats from
                      > Mr.Bolger (and other modern boats) often have a much more "flatt"
                      > one ??
                      > I DO know that it would be much better to take up some sort a course
                      > in 'elementary shipbuilding' or something like that, and I will in
                      > due time...but I just was curious .
                      > Allready I know (by studying the texts and articles from this great
                      > site (!) that my own little "shanty-boat' / 'narrow-boat' is gonna
                      > get a flatbottom - she will be going very slowly through very calm
                      > water, with allmost no deep water at all ... So that will do just
                      > fine then .
                      >
                      > If anyone would be so kind as to explain this a little I would be
                      > very gratefull for that.
                      > Also my earlier offer; to be willing to search for anything "Dutch-
                      > related" still stands, ok ?!
                      >
                      > Sincere greetings,
                      >
                      > M.Hulleman
                      >
                      >
                      >
                      >
                      > Bolger rules!!!
                      > - no cursing, flaming, trolling, spamming, or flogging dead horses
                      > - stay on topic, stay on thread, punctuate, no 'Ed, thanks, Fred' posts
                      > - Pls add your comments at the TOP, SIGN your posts, and snip away
                      > - Plans: Mr. Philip C. Bolger, P.O. Box 1209, Gloucester, MA, 01930, Fax:
                      > (978) 282-1349
                      > - Unsubscribe: bolger-unsubscribe@yahoogroups.com
                      > - Open discussion: bolger_coffee_lounge-subscribe@yahoogroups.com
                      > Yahoo! Groups Links
                      >
                      >
                      >
                      >
                      >
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