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Thread: Different kind of offsets, or just incomplete?

  1. #1
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    Default Different kind of offsets, or just incomplete?

    I'm practicing lofting by drafting scale models from offsets, and I've come across something that I don't quite understand. I have a table that appears to be only diagonals, and a layout for the diagonals and something do do with waterlines? It's a 7.6m boat with a beam of 2.2m

    Offsets2.jpg
    diags.jpg
    The stations are 500mm apart, and the D lines make sense when drawn as diagonals across the stations, but I can't figure out what the V offsets mean. Am I looking at a partial set of offsets, or just a different style? It's a Scandinavian design if that helps.

  2. #2
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    Default Re: Different kind of offsets, or just incomplete?

    V2 - V5 are beam of waterline.

    JS
    www.sassdesign.net
    I'm not lost, I'm just uncertain of my position.
    I'm still confused, but on a higher level

  3. #3
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    Default Re: Different kind of offsets, or just incomplete?

    Yes, VL appears to be standing in for WL. Judging by the spelling of "sektion" and those nice clean metric measurements this must be a German boat?

    You can fully define a hull using diagonals alone, in fact it is a nice clean way to do it although not very common.

  4. #4
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    Default Re: Different kind of offsets, or just incomplete?

    Swedish language does not use a "W" in its alphabet, and uses a "V" in its place, unlike Germany, so probably a Swedish design. I have seen similar offsets drawn by Ruben Ostlund and others.

  5. #5
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    Default Re: Different kind of offsets, or just incomplete?

    Knud Reimers Tumlaren is designed with diagonals alone.

  6. #6
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    Default Re: Different kind of offsets, or just incomplete?

    Diagonals are all you need for lofting EXCEPT for the heights and half breadths of the backbone, rabbet and sheer, which I don't see in that table. On the lofting you can develop buttock and waterlines for establishing rabbet bevels.
    Tables of offsets do refer to a lines plan and without the lines drawing it is hard to give as adequate decision on completeness.
    Last edited by Thad; 09-14-2020 at 09:43 AM.

  7. #7
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    Now, there's a long story...
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    Default Re: Different kind of offsets, or just incomplete?

    I have plans for both FAME and the Sound Schooner by B. B. Crowninshield. Both are focused on diagonals, and I'm guessing that was his usual method. Once I started lofting to it (I was just scaling it up from ¾ inch to the foot to 1 ½ inch to the foot for practice), it was amazing how well it worked.
    Heute ist so ein schöne Tag...

  8. #8
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    Default Re: Different kind of offsets, or just incomplete?

    Thanks everyone's input. I do have drawings of the shear, rabbet, keel, etc., so this isn't all I have, it's just what I didn't understand. You've also helped me wrap my head around the water line measurements. They were making no sense to me, but suddenly something in my brain clicked this morning, and now I think I understand it. I'm going to give it a go this evening and see how it turns out.

  9. #9
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    Default Re: Different kind of offsets, or just incomplete?

    It works!
    I don't have any splines or ducks yet, or even curves, so I'm just freehanding it, but it's actually really quick to plot out compared with plotting height above baseline and half breadths. Drawn at 1/10th scale.
    PXL_20200915_055411528.jpg

  10. #10
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    Default Re: Different kind of offsets, or just incomplete?

    Good, you've acquired new skills

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