Diagonals And Offset Tables

Discussion in 'Boatbuilding' started by BASIL J WALL, Aug 8, 2012.

  1. rwatson
    Joined: Aug 2007
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    Location: Tasmania,Australia

    rwatson Senior Member

    Thanks for that diagram.

    I think you may have left out important detail on 'The Tool' diagram - a hole on the centre of each 'circle' on the tool to place on the curve being offset.

    I have included them as green dots, on a green line representing the frame line, to show what I am alluding to.

    I have also included the orange 'wrong' triangle solution overlaid on it, with slightly wider centres for illustrative purposes only. I cant see any difference in operation for either tool, except that The Triangle has a much more convenient permanent 'pen' hole for plotting the inner point, whereas 'The Tool' will require manual matching of the dimension mark on the guide tongue.

    Likewise, for the lofting floor, the two bottom corner points of 'The Triangle' tool can be shaped to be conveniently laid up directly against any guide batten.

    Attached Files:

  2. jehardiman
    Joined: Aug 2004
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    Location: Port Orchard, Washington, USA

    jehardiman Senior Member

    Nope, you have to use the TANGENTS, not the centers. Which is why I pointed out the possible very small error. You could strike a line from inside to outside and split the difference, but I have found that in drafting and even on full size ship lofting, the lines overlie each other (i.e. error >> 0.5mm in ~6" or 300 mm.

    Again you misunderstand... the error in your method is shown in the attached graphic. You missed measuring the secant offset of the arc.

    Attached Files:

  3. SukiSolo
    Joined: Dec 2012
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    Location: Hampshire UK

    SukiSolo Senior Member

    I can verify that THE TOOL is also found this side of the 'Pond. ;)
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