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Re: Another design question

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  • Peter Vanderwaart
    ... the ... I m not sure that the meaning I take from this sentance is the one you intend. But as I read it, it is not true. Suppose you have two identical
    Message 1 of 12 , Nov 2, 2000
      >For a fair, untwisted side panel there is a set
      > relationship between the angles of the end cuts and the width of
      the
      > frame that determines the flare and the sheer.

      I'm not sure that the meaning I take from this sentance is the one
      you intend. But as I read it, it is not true.

      Suppose you have two identical side pieces. Top and bottom edges are
      stright and parallel. Ends are at an angle. If you stitch the ends
      together with wire, you can fit a midships frame for either a narrow
      boat or a fat boat.

      I think geometry is the way to go to answer your questions. If you
      lay out the body plan (i.e. end view), you can see how the wider the
      boat is, the greater the dip in the sheer.

      Peter
    • Hal Lynch
      Message 2 of 12 , Nov 2, 2000
      • Jeff Gilbert
        Pete Nit picking dept Widening the boat alone with the same side angle wont dip the sheer. Widening the boat at deck level by increasing the angle of the side
        Message 3 of 12 , Nov 3, 2000
          Pete
          Nit picking dept
          Widening the boat alone with the same side angle wont dip the sheer.
          Widening the boat at deck level by increasing the angle of the side (twist
          out)
          relative to the angles carried through the bow and stern will.
          Is that what you meant?
          Jeff
          ps Curving the sides halfway down(introducing tumblehome) will
          dip the sheer too, without widening the boat.


          ----- Original Message -----
          From: Peter Vanderwaart <pvanderw@...>
          To: <bolger@egroups.com>
          Sent: Friday, November 03, 2000 10:52 AM
          Subject: [bolger] Re: Another design question


          I think geometry is the way to go to answer your questions. If you
          lay out the body plan (i.e. end view), you can see how the wider the
          boat is, the greater the dip in the sheer.

          Peter



          Bolger rules!!!
          - no cursing
          - stay on topic
          - use punctuation
          - add your comments at the TOP and SIGN your posts
          - add some content: send "thanks!" and "ditto!" posts off-list.
        • pmcrannell@yahoo.com
          Matthew, If the ends of your straight edged panels are cut at an angle, you ll automatically get some flare. With frames wider on the top than the bottom,
          Message 4 of 12 , Nov 3, 2000
            Matthew,

            If the ends of your straight edged panels are cut at an angle,
            you'll automatically get some flare. With frames wider on the top
            than the bottom, you'll automatically get sheer. Varying these will
            give you differing amounts of both.

            If you increase the rake of the panel ends on a given midsection,
            you'll indroduce more twist to the sides. You won't get constant
            bevels (no biggy, especially in a flat bottomed boat). Decrease the
            rake, and you'll have less twist.

            Increasing the flare, only, you'll end up with more sheer.
            Decreasing flare will produce a flatter sheer.

            I have no idea how you'd calculate the results. If I were doing
            it, I'd make make scaled, card stock models. Then you'll be able to
            see how much a small change effects the sheer and flare. It can be
            pretty dramatic. Make sure you can disassemble the model. Then you
            can take the measurements directly off the panels.

            Take care,
            Pete Reynolds



            --- In bolger@egroups.com, "Matthew, Agnès & Fletcher Peillet-Long"
            <matthew.long@l...> wrote:
            > Here's another question for all the other would-be small boat
            designers
            > in the group. (That Duckworks contest is calling!)
            >
            > I've got Jim Michalak's SECRET GUIDE TO PLYWOOD BOAT DESIGN, and
            > Chapelle's BOATBUILDING, and I still can't get this one clear in my
            > head.
            >
            > Say you want to make a boat out of straight cut sides, like Teal or
            > Zephyr or many others, just cutting off the ends at an angle,
            spacing
            > the sides with a frame, and joining the ends at stem and stern (or
            bow
            > and stern transoms). For a fair, untwisted side panel there is a
            set
            > relationship between the angles of the end cuts and the width of
            the
            > frame that determines the flare and the sheer.
            >
            > Can someone explain this to me? I can visualize it, I can
            demonstrate
            > it, but I'd like to be able to calculate it. Basically, I want to
            > start with rectangular side panels of a given length (8', 16', 24',
            you
            > get the idea) and height, and play around with the possibilities.
            >
            > Feel free to contact me directly if this is too far off-topic.
            >
            > Thanks,
            >
            > Matthew
          • pmcrannell@yahoo.com
            Jeff, I have both of these programs, and have fiddled with them, but I haven t progressed very far with them. I just got an old 386 doorstop computer for home
            Message 5 of 12 , Nov 3, 2000
              Jeff,

              I have both of these programs, and have fiddled with them, but I
              haven't progressed very far with them. I just got an old 386 doorstop
              computer for home (a giveaway). Once I get the disk drive switched to
              a 3.5 incher, I'll be able to practice more. It's dicey doing it here
              at work!

              One thing that stumps me is how to save the dimensions on the
              panels in the nesting program, in Hull Design. I also haven't figured
              out how to do stability stuff with it. I'd like to print them so that
              I can make some models to test if plywood will take the bends. I
              haven't learned how to expand panels from a drawing by the
              traditional manner. Yet.

              I wish some of us could get together sometime, equipped with a box
              of pencils, a sharpener, reams of paper, splines, and ducks! I think
              we'd have a blast, and produce some good arguments, drawings, and get
              our fill of cross-pollenation. Rum, of course, would be involved!

              I agree that it's hard to communicate a lot of these things in
              print. I takes a long time to figure out how to explain things that
              are best done visually. I'll have to try to do some drawings, and
              scan them.

              My work schedule has been nuts. You guys don't realize this, but
              it's Christmas, already (!), for us web (and regular) retail guys.
              That and server explosions have increased my workload. I'm going to
              try to get my boat design entry finished in time, and do some other
              drawings, illustrating some of the threads I've stuck my oar in on. I
              can't wait for a hard winter!

              Take care,
              Pete


              --- In bolger@egroups.com, "Jeff Gilbert" <jgilbert@d...> wrote:
              > Pete,
              > you can calculate it out reasonably, but only if you assume all
              your curves
              > are
              > part of a circle, Thats probably ok for
              > a wharram canoe hull,
              > but not most monos.
              > Otherwise you can use Carene (free shareware) and look at the
              developed
              > panels.
              > I think Greg Carlsons shareware program does it too.
              > I agree with what you say below.
              > Its very hard to discuss without a pen & paper,
              > isnt it?
              > Jeff.
              > ----- Original Message -----
              > From: <pmcrannell@y...>
              > To: <bolger@egroups.com>
              > Sent: Saturday, November 04, 2000 4:02 AM
              > Subject: [bolger] Re: Another design question
              >
              >
              > Matthew,
              >
              > If the ends of your straight edged panels are cut at an angle,
              > you'll automatically get some flare. With frames wider on the top
              > than the bottom, you'll automatically get sheer. Varying these will
              > give you differing amounts of both.
              >
              > If you increase the rake of the panel ends on a given midsection,
              > you'll indroduce more twist to the sides. You won't get constant
              > bevels (no biggy, especially in a flat bottomed boat). Decrease the
              > rake, and you'll have less twist.
              >
              > Increasing the flare, only, you'll end up with more sheer.
              > Decreasing flare will produce a flatter sheer.
              >
              > I have no idea how you'd calculate the results. If I were doing
              > it, I'd make make scaled, card stock models. Then you'll be able to
              > see how much a small change effects the sheer and flare. It can be
              > pretty dramatic. Make sure you can disassemble the model. Then you
              > can take the measurements directly off the panels.
              >
              > Take care,
              > Pete Reynolds
              >
              >
              >
              > --- In bolger@egroups.com, "Matthew, Agnès & Fletcher Peillet-Long"
              > <matthew.long@l...> wrote:
              > > Here's another question for all the other would-be small boat
              > designers
              > > in the group. (That Duckworks contest is calling!)
              > >
              > > I've got Jim Michalak's SECRET GUIDE TO PLYWOOD BOAT DESIGN, and
              > > Chapelle's BOATBUILDING, and I still can't get this one clear in
              my
              > > head.
              > >
              > > Say you want to make a boat out of straight cut sides, like Teal
              or
              > > Zephyr or many others, just cutting off the ends at an angle,
              > spacing
              > > the sides with a frame, and joining the ends at stem and stern (or
              > bow
              > > and stern transoms). For a fair, untwisted side panel there is a
              > set
              > > relationship between the angles of the end cuts and the width of
              > the
              > > frame that determines the flare and the sheer.
              > >
              > > Can someone explain this to me? I can visualize it, I can
              > demonstrate
              > > it, but I'd like to be able to calculate it. Basically, I want to
              > > start with rectangular side panels of a given length (8', 16',
              24',
              > you
              > > get the idea) and height, and play around with the possibilities.
              > >
              > > Feel free to contact me directly if this is too far off-topic.
              > >
              > > Thanks,
              > >
              > > Matthew
              >
              >
              >
              > Bolger rules!!!
              > - no cursing
              > - stay on topic
              > - use punctuation
              > - add your comments at the TOP and SIGN your posts
              > - add some content: send "thanks!" and "ditto!" posts off-list.
            • Jeff Gilbert
              Pete, you can calculate it out reasonably, but only if you assume all your curves are part of a circle, Thats probably ok for a wharram canoe hull, but not
              Message 6 of 12 , Nov 3, 2000
                Pete,
                you can calculate it out reasonably, but only if you assume all your curves
                are
                part of a circle, Thats probably ok for
                a wharram canoe hull,
                but not most monos.
                Otherwise you can use Carene (free shareware) and look at the developed
                panels.
                I think Greg Carlsons shareware program does it too.
                I agree with what you say below.
                Its very hard to discuss without a pen & paper,
                isnt it?
                Jeff.
                ----- Original Message -----
                From: <pmcrannell@...>
                To: <bolger@egroups.com>
                Sent: Saturday, November 04, 2000 4:02 AM
                Subject: [bolger] Re: Another design question


                Matthew,

                If the ends of your straight edged panels are cut at an angle,
                you'll automatically get some flare. With frames wider on the top
                than the bottom, you'll automatically get sheer. Varying these will
                give you differing amounts of both.

                If you increase the rake of the panel ends on a given midsection,
                you'll indroduce more twist to the sides. You won't get constant
                bevels (no biggy, especially in a flat bottomed boat). Decrease the
                rake, and you'll have less twist.

                Increasing the flare, only, you'll end up with more sheer.
                Decreasing flare will produce a flatter sheer.

                I have no idea how you'd calculate the results. If I were doing
                it, I'd make make scaled, card stock models. Then you'll be able to
                see how much a small change effects the sheer and flare. It can be
                pretty dramatic. Make sure you can disassemble the model. Then you
                can take the measurements directly off the panels.

                Take care,
                Pete Reynolds



                --- In bolger@egroups.com, "Matthew, Agnès & Fletcher Peillet-Long"
                <matthew.long@l...> wrote:
                > Here's another question for all the other would-be small boat
                designers
                > in the group. (That Duckworks contest is calling!)
                >
                > I've got Jim Michalak's SECRET GUIDE TO PLYWOOD BOAT DESIGN, and
                > Chapelle's BOATBUILDING, and I still can't get this one clear in my
                > head.
                >
                > Say you want to make a boat out of straight cut sides, like Teal or
                > Zephyr or many others, just cutting off the ends at an angle,
                spacing
                > the sides with a frame, and joining the ends at stem and stern (or
                bow
                > and stern transoms). For a fair, untwisted side panel there is a
                set
                > relationship between the angles of the end cuts and the width of
                the
                > frame that determines the flare and the sheer.
                >
                > Can someone explain this to me? I can visualize it, I can
                demonstrate
                > it, but I'd like to be able to calculate it. Basically, I want to
                > start with rectangular side panels of a given length (8', 16', 24',
                you
                > get the idea) and height, and play around with the possibilities.
                >
                > Feel free to contact me directly if this is too far off-topic.
                >
                > Thanks,
                >
                > Matthew



                Bolger rules!!!
                - no cursing
                - stay on topic
                - use punctuation
                - add your comments at the TOP and SIGN your posts
                - add some content: send "thanks!" and "ditto!" posts off-list.
              • GHC
                Enter a displacement for the hull to begin to see stability calculations. Enter 0 to turn them back off. After you Save/Create, you can go to nesting. Check
                Message 7 of 12 , Nov 3, 2000
                  Enter a displacement for the hull to begin to see stability calculations.
                  Enter "0" to turn them back off.

                  After you Save/Create, you can go to nesting. Check -->[x] and you get
                  offsets. Save, and they all go into nest.txt, which you can read. All
                  your "raw" panels, unnested, are saved in handplot.txt. No one said
                  freeware had to make sense, too... (well, that's not true, someone did once
                  tell me so ;-)

                  While nesting, you can also Print to your printer, though my print driver
                  isn't all that reliable. Maybe better to Save/Create to DXF or HPGL and
                  import and print from your favorite CAD program.

                  Gregg Carlson


                  At 07:53 PM 11/3/2000 -0000, you wrote:
                  > One thing that stumps me is how to save the dimensions on the
                  >panels in the nesting program, in Hull Design. I also haven't figured
                  >out how to do stability stuff with it. I'd like to print them so that
                  >I can make some models to test if plywood will take the bends. I
                  >haven't learned how to expand panels from a drawing by the
                  >traditional manner. Yet.
                • pmcrannell@yahoo.com
                  Gregg, Hey! Thanks for the quick response! I wasn t complaining about your program, by the way. I like it A LOT. I was just stumped, and hadn t fiddled enough,
                  Message 8 of 12 , Nov 3, 2000
                    Gregg,

                    Hey! Thanks for the quick response! I wasn't complaining about
                    your program, by the way. I like it A LOT. I was just stumped, and
                    hadn't fiddled enough, yet. I'll try your instructions.

                    Take care,
                    Pete



                    --- In bolger@egroups.com, GHC <ghartc@p...> wrote:
                    > Enter a displacement for the hull to begin to see stability
                    calculations.
                    > Enter "0" to turn them back off.
                    >
                    > After you Save/Create, you can go to nesting. Check -->[x] and you
                    get
                    > offsets. Save, and they all go into nest.txt, which you can read.
                    All
                    > your "raw" panels, unnested, are saved in handplot.txt. No one said
                    > freeware had to make sense, too... (well, that's not true, someone
                    did once
                    > tell me so ;-)
                    >
                    > While nesting, you can also Print to your printer, though my print
                    driver
                    > isn't all that reliable. Maybe better to Save/Create to DXF or
                    HPGL and
                    > import and print from your favorite CAD program.
                    >
                    > Gregg Carlson
                    >
                    >
                    > At 07:53 PM 11/3/2000 -0000, you wrote:
                    > > One thing that stumps me is how to save the dimensions on the
                    > >panels in the nesting program, in Hull Design. I also haven't
                    figured
                    > >out how to do stability stuff with it. I'd like to print them so
                    that
                    > >I can make some models to test if plywood will take the bends. I
                    > >haven't learned how to expand panels from a drawing by the
                    > >traditional manner. Yet.
                  • Phillip Lea
                    I have had the same question. Peter has addressed how flair and tumblehome could affect sheer. But I have been interested in the geometry and design of (and
                    Message 9 of 12 , Nov 5, 2000
                      I have had the same question. Peter has addressed how flair and
                      tumblehome could affect sheer. But I have been interested in the
                      geometry and design of (and designing) instant boats (built with no
                      backbone) where there is a (virtually) constant flair from stem to
                      stern, with a constant width side plank, such as Windsprint and
                      Birdwatcher - but also boats like Black Skimmer (or Skillygalee) ,
                      with a varying plank width. The section view of these boats have the
                      flair lines parallel. Getting the plank ends cut at the proper angle
                      ensures that the plank will lie correctly and come together just
                      right. Just recently I have worked it out on paper like this.

                      At the bow (and the stern of double-ended boats) of a straight
                      stemmed boat, you can work with three related right triangles in a 3
                      dimensional figure. Since the fore and aft distance is so short, and
                      there is so little curve to the sides in this short forward section
                      of the boat, we just assume that there is zero curve to the plank.
                      Take a look at the plan view of Birdwatcher or Windsprint and you can
                      see this straight line forward.

                      The first right triangle is in the profile (side) view and lies on
                      the centerline, where the stem is the hypotenuse, the bottom corner
                      is
                      where the stem meets the boat's bottom, the other two sides are
                      perfectly vertical (side Y) and perfectly horizontal (side Z), all on
                      centerline. One of the angles of this triangle is equal to the bow
                      profile angle, the angle above horizontal.

                      The second right triangle is in the section (end) view. It describes
                      half of a vertical bulkhead (if there were one) and sits on its point
                      right at the base of the stem. Its has a vertical side on the
                      centerline (side Y shared with the first triangle), its upper side is
                      horizontal running athwartship to the sheer (side X), and its
                      hypotenuse lies on the side plank. Its bottom angle is the angle of
                      flair.

                      The third right triangle is seen in plan (top) view, and its sides
                      are the top edge of the vertical bulkhead (side X with triangle 2),
                      the centered horizontal line to the peak of the stem (side Z shared
                      with triangle 1), and its hypotenuse is the sheer (or really close to
                      it). The forward angle of this third triangle is the entry angle.

                      Note: as in Carlson's HULL program, X is width (or 1/2 beam), Y axis
                      is vertical, and Z is horizontal along the length. If I explained
                      this well enough, and you were able to draw this, you would have all
                      three right angle sharing edges or sides with another right angle.
                      We can make these comparisons,

                      Tangent of the bow angle (angle above horizontal) = Y/Z
                      Tangent of the entry angle = X/Z
                      Tangent of flair = X/Y

                      Assuming a given entry angle and given flair, there can be only one
                      bow angle. As you said, you can play around with the possibilities.
                      Less flair and a wider entry angle will force the bow angle up from
                      the horizontal. And conversely, more flair and a narrower entry
                      angle will lower the bow angle towards horizontal. If you have Build
                      the New Instant Boats, it is quite evident when you compare the Light
                      Schooner with Windsprint.

                      I have been "working" on a Bolger-inspired, instant-type box sharpie,
                      that has much in common with Skillygalee, has the leeboards of
                      Blackskimmer, and uses planks 20 to 22 feet long. That's how I've
                      gotten into this. But I have know idea how Bolger or Michalak come
                      up with the angles. They probably are drawing the lines in a cad
                      program and they all come out because they are being calculated
                      constantly.

                      Seems "on topic" to me. ;-)

                      Phil Lea
                      Russellville, Arkansas

                      > From: Matthew, Agnès & Fletcher Peillet-Long
                      <matthew.long@l...>
                      > Date: Thu Nov 2, 2000 10:59pm Subject: Another design question
                      >
                      > Here's another question for all the other would-be small boat
                      designers in the
                      > group. [snip] Say you want to make a boat out of straight cut
                      sides, like Teal
                      > or Zephyr or many others, just cutting off the ends at an angle,
                      spacing the
                      > sides with a frame, and joining the ends at stem and stern (or bow
                      and stern
                      > transoms). For a fair, untwisted side panel there is a set
                      relationship between
                      > angles of the end cuts and the width of the frame that determines
                      the flare and
                      > the sheer. Can someone explain this to me? I can visualize it, I
                      can
                      > demonstrate it, but I'd like to be able to calculate it.
                      Basically,
                      I want to start
                      > with rectangular side panels of a given length (8', 16', 24', you
                      get the idea)
                      > and height, and play around with the possibilities.
                      > Thanks,
                      > Matthew
                    • Peter Vanderwaart
                      ... I haven t had time to go through your math, but with respect to the above, I believe that they draw the boat and then figure the angle from the drawing via
                      Message 10 of 12 , Nov 6, 2000
                        > But I have no idea how Bolger or Michalak come
                        > up with the angles. They probably are drawing the lines in a cad
                        > program and they all come out because they are being calculated
                        > constantly.

                        I haven't had time to go through your math, but with respect to the
                        above, I believe that they draw the boat and then figure the angle
                        from the drawing via geometric methods. That is, draw the angle, then
                        measure it with a protractor or measure the sides and get the angle
                        from a trig table.

                        Mr. Bolger drew most of the boats you are talking about before small
                        computers & cheap CAD were available. He is very much a paper and ink
                        person.

                        Michalak has described bits and pieces of his design methods in his
                        various essays, and he also designs on paper.

                        I have a set of plans for the Norwalk Island Sharpie. They all came
                        from a CAD system of some sort and some of the details are a little
                        silly. For example, the radius of the transom crown was given as 23'-
                        5.1875". (On balance, I think the plans are exhaustive and very
                        clear. A complete plan for each frame is given on a separtae 8 1/2 x
                        11 page, which is not necessarily as convenient as putting them all
                        on a bigger sheet.)


                        Peter
                      • Jeff Gilbert
                        Pete Crown radius is h/2 + ((b**2)/8h) where b is the chord and h the max height of the crown above it, & B**2 = b squared. Jeff ps 23feet 5.1875inches is
                        Message 11 of 12 , Nov 8, 2000
                          Pete
                          Crown radius is
                          h/2 + ((b**2)/8h)
                          where b is the chord and
                          h the max height of the crown above it, &
                          B**2 = b squared.
                          Jeff
                          ps 23feet 5.1875inches is the kind of rot you
                          get when you calc everything in decimal feet to say 5 decimal places, and
                          decide to
                          convert it to inches so people can actually measure it.
                          (thus going from the sublime to the ridiculous )
                          But then if America insists on retaining feet over mm,
                          where are the decimal feet tapes and rulers??
                          One simply cant both calc and measure in imperial.
                          Chorus:
                          The English, the English, the English are best etc etc

                          pps Whover cautioned our mathematical doodlings as OT
                          please note my feeble attempt to switch lists. But I would say that
                          the ballasting thread is very relevant to Bolger as he offers a range of
                          ballasting
                          systems in his work which could be bewildering to a potential Bolger
                          builder.
                          Further the safety of a sailboat is directly linked to choosing the correct
                          ballasting
                          for your hull and sail grounds. There is no wrong list for safety issues.

                          ----- Original Message -----
                          From: Peter Vanderwaart <pvanderw@...>
                          To: <bolger@egroups.com>
                          Subject: [bolger] Re: Another design question
                          I have a set of plans for the Norwalk Island Sharpie. They all came
                          from a CAD system of some sort and some of the details are a little
                          silly. For example, the radius of the transom crown was given as 23'-
                          5.1875". (On balance, I think the plans are exhaustive and very
                          clear. A complete plan for each frame is given on a separtae 8 1/2 x
                          11 page, which is not necessarily as convenient as putting them all
                          on a bigger sheet.)
                          Peter
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