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Enlarging a Plan

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  • srelt@iclub.org
    I am thinking about purchasing a Long Micro plan and enlarging it mathematically to 23 6 . Anyone see a problem from that? I thought I would increase the
    Message 1 of 7 , Aug 2, 2000
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      I am thinking about purchasing a Long Micro plan and enlarging it
      mathematically to 23' 6". Anyone see a problem from that? I thought
      I would increase the scantlings by 1/4" ply all about.

      Phil Sharp
      srelt@...
    • Peter Vanderwaart
      I think that it is too big an increase to do without a careful computation of weights and sail area, not to mention the construction plan. Are thinking of just
      Message 2 of 7 , Aug 2, 2000
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        I think that it is too big an increase to do without a careful
        computation of weights and sail area, not to mention the construction
        plan. Are thinking of just making it longer, or also wider?

        All sorts of things can get out of whack, and from what I hear, you
        don't want to risk getting the rig any bigger porportionally than it
        is. But the crew (live ballast) will be smaller for the size of the
        boat. If you make the boat wider, how does the bottom make use of
        plywood sheets? If the keel is the same width, is the ballast to
        little? If the keel is the same width, is the ballast too light?
        Should the keel be deeper? What about the mast dimensions? Thicker?
        Longer?

        You will find, I think, when you start to work out the details of the
        construction that PCB has made very efficient use of the materials.
        He has had a lot of practice. If you just charge into it, you could
        end up with a much higher material cost.

        On the other hand, if you want to do your own design at the new size,
        modeled after the LM, I think it's probably a fairly safe way to go.
        Just do the homework.

        Why not Sea Bird '86? Black Skimmer?

        Peter

        > I am thinking about purchasing a Long Micro plan and enlarging it
        > mathematically to 23' 6".
      • srelt@iclub.org
        Peter--thanks for the many good points. As a 60 year old, I want and need a boat stable enough I don t worry about it, able enough to take the bumps of
        Message 3 of 7 , Aug 2, 2000
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          Peter--thanks for the many good points. As a 60 year old, I want and
          need a boat stable enough I don't worry about it, able enough to take
          the bumps of trailering but also do offshore work if I should decide
          to, large enough to let my wife and I spend some time aboard but
          small
          enough to be singlehanded. The Sea Bird (I still consider a raised
          flush decked version of the original) by PB is great, but too tiddly
          for my taste and purpose--perhaps too tiring. I don't know much
          about
          Black Skimmer. And the point about the sails, I thought I would do
          an
          enlargement of the modified cross between gaff and fully battened lug
          that PB worked out for a Micro. You are right about the ballast,
          etc.
          I must be very careful.
          Thanks for all your ideas.

          Phil Sharp


          --- In bolger@egroups.com, "Peter Vanderwaart" <pvanderw@o...> wrote:
          >
          > I think that it is too big an increase to do without a careful
          > computation of weights and sail area, not to mention the
          construction
          > plan. Are thinking of just making it longer, or also wider?
          >
          > All sorts of things can get out of whack, and from what I hear, you
          > don't want to risk getting the rig any bigger porportionally than
          it
          > is. But the crew (live ballast) will be smaller for the size of the
          > boat. If you make the boat wider, how does the bottom make use of
          > plywood sheets? If the keel is the same width, is the ballast to
          > little? If the keel is the same width, is the ballast too light?
          > Should the keel be deeper? What about the mast dimensions? Thicker?
          > Longer?
          >
          > You will find, I think, when you start to work out the details of
          the
          > construction that PCB has made very efficient use of the materials.
          > He has had a lot of practice. If you just charge into it, you could
          > end up with a much higher material cost.
          >
          > On the other hand, if you want to do your own design at the new
          size,
          > modeled after the LM, I think it's probably a fairly safe way to
          go.
          > Just do the homework.
          >
          > Why not Sea Bird '86? Black Skimmer?
          >
          > Peter
          >
          > > I am thinking about purchasing a Long Micro plan and enlarging it
          > > mathematically to 23' 6".
        • Peter Vanderwaart
          Phil, I don t want to be a dead horse, or even a living horse, but I have a specific point to add. The Bolger boxes have, on average, a frame or bulkhead every
          Message 4 of 7 , Aug 3, 2000
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            Phil,

            I don't want to be a dead horse, or even a living horse, but I have a
            specific point to add.

            The Bolger boxes have, on average, a frame or bulkhead every 4 feet.
            The LM has 5. Your boat would need six. That raises questions about
            the layout.

            The bulkhead between cabin and cockpit is about midships. If you
            space 6 bulkheads equidistant, then you don't have a one at midships,
            and would have to decide between a bigger cockpit or a bigger cabin.

            Or, you could decide, sensibly enough, that proper construction
            requires a bulkhead at midships and then have to arrange an
            additional frame both forward and aft.

            Peter

            p.s. The mast would probably have to be in a proper, pivoting
            tabernacle. This would end up being a big boat to trailer in any case.
          • pmcrannell@yahoo.com
            Dear Phil, There was a trick to enlarging boats, mostly cargo carriers, that the shipyards used. The boatbuilders would simply move the bow and stern further
            Message 5 of 7 , Aug 3, 2000
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              Dear Phil,

              There was a trick to enlarging boats, mostly cargo carriers, that
              the shipyards used. The boatbuilders would simply move the bow and
              stern further apart. They would increase the length by adding to the
              middle of the boat, keeping the beam and mid-section shape the same
              at the point of the cut. What you end up with is a roomier boat, that
              will be faster with the same power as the original. You should be
              able to keep the sailplan and ballast the same by this method.

              There are a number of examples of this. Phil Bolger did this with
              a number of designs. The one that comes to mind is Surf. He took the
              mid-section of the Elegant Punt, and stretched her out 7' 9", and
              tapered the ends somewhat. Surf uses the same rig, rudder, and
              leeboard as the Punt. She sails rings around the shorter boat, can
              carry a lot more weight, and rows much better.

              Pearson Yachts used to build a boat called a Vanguard, 32' long,
              designed by Phil Rhodes. She looks vaguely Concordia-ish. They took
              this design, and added an 8' mid-section, and came up with a very
              fast boat called the Rhodes Reliant 40. This boat has more sail area
              than the Vanguard, and more ballast, I'm sure. This is a very fast
              boat. A local one (St. Michael's, Md., Chesapeake Bay) won her class
              in this year's Bermuda Race. She's a hard boat for us to beat in
              local races (I race on a friend's old Cal 36). We owe her an eighteen
              second per mile handicap. She whips us consistently, boat for boat.

              Another boatbuilder, I can't think of whom, used another old trick
              to get a bigger boat. They'd take the molds of a successful design,
              and simply space them farther apart, say, 4' centers instead of 3'
              centers. The stem and transom bevels would be different, but not much
              else was. This technique was widely used by workboat builders for
              centuries.

              The key to all this was that the builders didn't change the size
              or shape of the mid-section. The determination of this section is the
              first step in designing a boat, governing displacement. Everything
              else grows out of the mid-section.

              Using one of these techniques is how I'd go about expanding an
              extant design. I'd simply add whatever length to the middle of the
              boat. If you increase the beam, as you proposed, you're going to have
              to change everything about the design. Sail area, ballast, lateral
              plane area, centers of gravity and bouyancy would all have to be
              recalculated.

              The cautionary advice everyone is giving you is good. Enlarging
              the boat needs a lot of thought and planning. I wouldn't hesitate to
              do it, however, if you keep what's been learned over time about boat
              design firmly in mind. Do your research. Read as much about boat
              design as you can. I recommend Bolger's books, Dave Gerr's "The
              Nature Of Boats" (a little corny in style, but totally interesting
              information), and "How To Design A Boat" by John Teale (so far very
              good. I haven't finished reading it yet).

              Take care,
              Pete Reynolds



              --- In bolger@egroups.com, srelt@i... wrote:
              > I am thinking about purchasing a Long Micro plan and enlarging it
              > mathematically to 23' 6". Anyone see a problem from that? I
              thought
              > I would increase the scantlings by 1/4" ply all about.
              >
              > Phil Sharp
              > srelt@i...
            • pmcrannell@yahoo.com
              Afterall, you re only adding four feet to the Long Micro! ... that ... the ... that ... with ... the ... area ... class ... eighteen ... trick ... much ... the
              Message 6 of 7 , Aug 3, 2000
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                Afterall, you're only adding four feet to the Long Micro!


                --- In bolger@egroups.com, pmcrannell@y... wrote:
                > Dear Phil,
                >
                > There was a trick to enlarging boats, mostly cargo carriers,
                that
                > the shipyards used. The boatbuilders would simply move the bow and
                > stern further apart. They would increase the length by adding to
                the
                > middle of the boat, keeping the beam and mid-section shape the same
                > at the point of the cut. What you end up with is a roomier boat,
                that
                > will be faster with the same power as the original. You should be
                > able to keep the sailplan and ballast the same by this method.
                >
                > There are a number of examples of this. Phil Bolger did this
                with
                > a number of designs. The one that comes to mind is Surf. He took
                the
                > mid-section of the Elegant Punt, and stretched her out 7' 9", and
                > tapered the ends somewhat. Surf uses the same rig, rudder, and
                > leeboard as the Punt. She sails rings around the shorter boat, can
                > carry a lot more weight, and rows much better.
                >
                > Pearson Yachts used to build a boat called a Vanguard, 32' long,
                > designed by Phil Rhodes. She looks vaguely Concordia-ish. They took
                > this design, and added an 8' mid-section, and came up with a very
                > fast boat called the Rhodes Reliant 40. This boat has more sail
                area
                > than the Vanguard, and more ballast, I'm sure. This is a very fast
                > boat. A local one (St. Michael's, Md., Chesapeake Bay) won her
                class
                > in this year's Bermuda Race. She's a hard boat for us to beat in
                > local races (I race on a friend's old Cal 36). We owe her an
                eighteen
                > second per mile handicap. She whips us consistently, boat for boat.
                >
                > Another boatbuilder, I can't think of whom, used another old
                trick
                > to get a bigger boat. They'd take the molds of a successful design,
                > and simply space them farther apart, say, 4' centers instead of 3'
                > centers. The stem and transom bevels would be different, but not
                much
                > else was. This technique was widely used by workboat builders for
                > centuries.
                >
                > The key to all this was that the builders didn't change the size
                > or shape of the mid-section. The determination of this section is
                the
                > first step in designing a boat, governing displacement. Everything
                > else grows out of the mid-section.
                >
                > Using one of these techniques is how I'd go about expanding an
                > extant design. I'd simply add whatever length to the middle of the
                > boat. If you increase the beam, as you proposed, you're going to
                have
                > to change everything about the design. Sail area, ballast, lateral
                > plane area, centers of gravity and bouyancy would all have to be
                > recalculated.
                >
                > The cautionary advice everyone is giving you is good. Enlarging
                > the boat needs a lot of thought and planning. I wouldn't hesitate
                to
                > do it, however, if you keep what's been learned over time about
                boat
                > design firmly in mind. Do your research. Read as much about boat
                > design as you can. I recommend Bolger's books, Dave Gerr's "The
                > Nature Of Boats" (a little corny in style, but totally interesting
                > information), and "How To Design A Boat" by John Teale (so far very
                > good. I haven't finished reading it yet).
                >
                > Take care,
                > Pete Reynolds
                >
                >
                >
                > --- In bolger@egroups.com, srelt@i... wrote:
                > > I am thinking about purchasing a Long Micro plan and enlarging it
                > > mathematically to 23' 6". Anyone see a problem from that? I
                > thought
                > > I would increase the scantlings by 1/4" ply all about.
                > >
                > > Phil Sharp
                > > srelt@i...
              • srelt@iclub.org
                Thank you for all the comments. I am probably not as inept at boat design and construction as I appear, and, much more probably, more so than I know. So,
                Message 7 of 7 , Aug 3, 2000
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                  Thank you for all the comments. I am probably not as inept at boat
                  design and construction as I appear, and, much more probably, more so
                  than I know. So, thanks for your restraint.

                  Several mentioned the new Martha Jane. I can find nothing about it.
                  I have an old Commonsense catalogue, the web, and PB's "Boats with an
                  Open Mind." So far I have seen nothing new. Can someone put me onto
                  a better, available source?

                  Phil Sharp
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