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Re: Boat Offsets and Stitch n Tape

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  • pvanderwaart
    ... It s all based on the concept that the ply doesn t stretch, so the triangles all stay the same size and shape. Suppose you have a chine hull drawn with the
    Message 1 of 15 , Mar 1 9:13 AM
      > I recall reading that Jim Michalak uses the method of joining
      > triangles.

      It's all based on the concept that the ply doesn't stretch, so the
      triangles all stay the same size and shape. Suppose you have a chine
      hull drawn with the usual 11 stations (0-10). To lay out the
      topsides, you could start with the triangle that has the base at the
      chine and rail at station 5, and the peak at the rail on station 6.
      The next triangle would have a base at the chine and rail at station
      6 and the peak on the chine at station 5. Etc, both ways.

      So far as I know, all the fancy software works basically the same
      way, except they use a larger number of stations (and/or cleverly
      chosen triangles) to cut down the error.

      Exercise for the student: What happens when you try this process with
      a "non-developable" hull shape? Hint: the trouble begins because the
      straight-line length of a triangle side is not the same as the length
      measured along the curve of the hull.

      Peter
    • ghartc
      I wrote the Hulls program freeware which you can get from carlsondesign.com. You design in 3D and it develops the flat panels to cut. You can model an
      Message 2 of 15 , Mar 1 12:34 PM
        I wrote the "Hulls" program freeware which you can get from
        carlsondesign.com. You design in 3D and it develops the flat panels
        to cut. You can model an existing design, which you know is
        "developable". On a scratch design, my program doesn't restrict you
        to conical development (which means each panel lies on a cone or
        cylinder), mainly because it doesn't know how. In Hulls, you can
        freely bend and twist panels, so they *might* be tortured.

        It's a little like bumblees flying - they can't fly, but since they
        don't know that, they do anyway. Practically, what happens when you
        really bend and twist is that your panel might want to "cup" some
        from the straight line segments going around the bulkhead. The
        program doesn't know any different. You might see some in short, fat
        panels/boats with a lot of torture, though it's generally less
        than "manufacturing" (sawing and epoxy-ing) tolerances.

        Actually, its a lot more intuitive than it sounds - what looks
        pleasing to the eye and streamlined to the water is not going to be
        tortured much if at all. So, lots of hulls get built by people who
        never heard of donical cevelopment. (Pls send your broadsides to me
        directly.)

        {That's the difference between engineers or "applied scientists"
        (like me) who design to +/-10% and get it built, and scientists who
        enjoy rigor. But, I will concede here that I will NOT be volunteering
        for the Mars shot that makes it 90% or so of the way back to earth;-}

        To output, you can 1.) send the hulls output to a sailmaker who has
        one of my plotting machines and would put it on paper for you, 2.)
        find a draftsman with a big roll paper plotter and give him the HPGL
        or DXF output to plot, 3.) use the handplot.txt and tape meausure to
        loft out the panels, or 4.) under the hulls nesting feature, nest the
        panels and plot them directly, X by Y, onto the plywood as shown by
        the program. The optical method sounds like a lot of extra work (?)

        Gregg Carlson
        www.carlsondesign.com

        --- In bolger@y..., "steelcb" <steelcb@y...> wrote:
        >Don't know if this is what you have in mind, but I have been using
        >the chine designer software I downloaded through the "files" section
        >to develop some interesting hull shapes which I modeled in cardboard.
        >
        >After printing them out, I scanned in those images and inserted
        >scanned images into Micrsoft Powerpoint slides. I adjusted these
        >inserted images to take up whole page and superimposed a gridwork...
      • steelcb
        Greg, I ve enjoyed your hulls software immensely. It provides such scope for the imagination. I don t worry about how it works, I just use it for hours on
        Message 3 of 15 , Mar 1 8:57 PM
          Greg,

          I've enjoyed your hulls software immensely. It provides such scope
          for the imagination. I don't worry about how it works, I just use it
          for hours on end pulling and pushing and contemplating the new hull
          shapes. It works well for designing decks and structures, wings, and
          fuselages too. Thanks a million.

          Tom Pannell
          Tulls Bay, NC

          --- In bolger@y..., "ghartc" <gcarlson@c...> wrote:
          > I wrote the "Hulls" program freeware which you can get from
          > carlsondesign.com. You design in 3D and it develops the flat panels
          > to cut. You can model an existing design, which you know is
          > "developable". On a scratch design, my program doesn't restrict you
          >
        • jhkohnen@boat-links.com
          THE book on developing panel shapes is: Ship And Aircraft Fairing And Development for Draftsmen and Loftsmen and Sheet Metal Workers by Sam Rabl It s available
          Message 4 of 15 , Mar 2 10:21 AM
            THE book on developing panel shapes is:

            Ship And Aircraft Fairing And Development for Draftsmen and Loftsmen and
            Sheet Metal Workers by Sam Rabl

            It's available for reasonable prices used (see http://www.abe.com), but
            I've also heard that it's been reprinted recently (or maybe it never went
            out of print?).

            Yes, that's the same Sam Rabl who wrote Boatbuilding in Your Own Back Yard.


            --
            John <jkohnen@...>
            http://www.boat-links.com/
            Nobody ought to wear a Greek fisherman's hat unless they meet two conditions:
            1. He is a Greek
            2. He is a Fisherman <Roy Blount Jr.>
          • David Romasco
            Westie Farmer had some great tales about Sam s experience in designing a flash amphibian aircraft, worth looking up at the library ( My Old Boat Shop ). Good
            Message 5 of 15 , Mar 2 5:25 PM
              Westie Farmer had some great tales about Sam's experience in designing a
              flash amphibian aircraft, worth looking up at the library ('My Old Boat
              Shop'). Good book anyway, no matter what Thomas Firth Jones says..

              David Romasco

              -----Original Message-----
              From: jhkohnen@... [mailto:jhkohnen@...]
              Sent: Saturday, March 02, 2002 1:21 PM
              To: bolger@yahoogroups.com
              Subject: Re: [bolger] Re: Boat Offsets and Stitch n Tape

              THE book on developing panel shapes is:

              Ship And Aircraft Fairing And Development for Draftsmen and Loftsmen and
              Sheet Metal Workers by Sam Rabl

              It's available for reasonable prices used (see http://www.abe.com), but
              I've also heard that it's been reprinted recently (or maybe it never
              went
              out of print?).

              Yes, that's the same Sam Rabl who wrote Boatbuilding in Your Own Back
              Yard.


              --
              John <jkohnen@...>
              http://www.boat-links.com/
              Nobody ought to wear a Greek fisherman's hat unless they meet two
              conditions:
              1. He is a Greek
              2. He is a Fisherman <Roy Blount Jr.>






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            • filmokentucky@aol.com
              Please unsuscribe me
              Message 6 of 15 , Mar 2 9:16 PM
                Please unsuscribe me
              • ravenouspi
                ... If you are taking this group via email, simply click on the Unsubscribe link at the end of your message (it comes in every single email post you receive
                Message 7 of 15 , Mar 2 9:32 PM
                  --- In bolger@y..., filmokentucky@a... wrote:
                  > Please unsuscribe me

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