How to calculate outside hull dimensions

Discussion in 'Wooden Boat Building and Restoration' started by Insomniac, Jul 25, 2018.

  1. BlueBell
    Joined: May 2017
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    Location: Victoria BC Canada

    BlueBell Ahhhhh...

    "I considered contacting him but I try to avoid bothering him too much so thought I would see if I could find a solution on my own."
    Ridiculous.
    Colin needs to know what people are doing with his plans.
    He needs your feedback and to know what your trying to do.
    He'd have the best advice for you as it's his plan and he needs to know what's working and what isn't with his design.
    Plans take into consideration just what you are trying to do.
    He will give you the best advice.
    I know Colin and he'd want to know what you're up to, trying to do and why.
    Contact him, as I think you are barking up the wrong tree.
    Good luck, and let us know the outcome.

    Q. Did you hear about the insomniac, dyslexic, agnostic?
    A. He would lay awake in bed at night wondering if there really was a dog!
     
  2. DCockey
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    DCockey Senior Member

    @rwatson Do you have an example of starting with a set of flat panels and computationally/analytically determining the 3D shape of the panels joined at the chine without using any a-priori knowledge of the 3D shape?
     
  3. SamSam
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    Location: Coastal Georgia

    SamSam Senior Member

    PITA means Pain in the butt.
    A solid support placed wrong could introduce unfairness. If the base the supports are attached to is on a single plane, or is accurate however you do it, and you attach the supports accurately, it should work. It seems like a lot of extra work for one boat, but for a multitude it seems a good idea.
    Assuming you have the supports you envision, then what? Do you temporarily attach the panels to the supports or? Do you attach the panels to themselves with a fillet or fiberglass tape or tabbing? What are the panels made from, wood or foam or ?
     
  4. SamSam
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    Location: Coastal Georgia

    SamSam Senior Member

    I'm just wondering here. Does a long, slim boat like this ever change shape with the weather? Does it flex in the water when in use?
     
  5. rwatson
    Joined: Aug 2007
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    Location: Tasmania,Australia

    rwatson Senior Member

    Yes, that's what I am saying. The example I gave had the original hull shape as a proof of concept, but you don't need it.

    That little illustration provided some hints as to how its done.

    By triangulating the dimensions of the flat panels, you can build a 3d shape, so you can calculate the station shapes.

    The triangles can be very small, or pretty large. The larger the triangle, the more "sawtooth" the project result is, but by using "Fair" and drawing a join line, the actual smooth dimensions can be produced.

    You will need a 3d Cad package to make it possible. I am sure it can be done by hand, but it's pretty tedious even with CAD.
     
  6. Insomniac
    Joined: Jul 2018
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    Insomniac Junior Member

    Good point. Thanks for setting me straight.
     
  7. Insomniac
    Joined: Jul 2018
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    Insomniac Junior Member

    Ah ok I see what you mean. All very important considerations. Panels would be made from 3mm plywood. Idea was to cut supports from thin plywood, and not affix them the the panels, just have the panels rest on the supports while I place the necessary fillets and fiberglass tape on the inside of the hull.
     
  8. Insomniac
    Joined: Jul 2018
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    Insomniac Junior Member

    Thanks for sharing the drawing. I really don't understand this but I will give this some more thought. Any links you may be able to share that provide more detailed instructions on this process?
     
  9. TANSL
    Joined: Sep 2011
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    TANSL Senior Member

    @rwatson the method could be very, very interesting, could you give more details about the problems it presents and how to solve them ?. I tried something similar with AutoCAD and I had to give up. Thinking about it, because it really interests me, I wonder if, since we are working in space, we should not draw spheres instead of the circles that are seen in your sketch. Any clarification that would allow to advance in that procedure would be very appreciated. Thanks in advance.
     
  10. rwatson
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    rwatson Senior Member

    "Insomniac - Thanks for sharing the drawing. I really don't understand this but I will give this some more thought. Any links you may be able to share that provide more detailed instructions on this process?"


    If you look very closely at the example I showed you, it mentions three colours of spheres that Tansl refers to, for that very reason.

    I just don't show them in the example, because they obscure the actual flat panel section that are being processed.

    That's where the triangulation comes in - the end of the "pyramid" is where the three spheres intersect.

    It's a shame they have "dropped" all the old articles, because I went through the steps one by one in the example, and now I have to re-create the "lessons".

    I did make a mistake in that original article though, in that I did not regard the Keel line of the bottom panel as having to stay in a perpendicular plane, so in that sense the exercise was flawed.

    If I get inspired over the next few days, I will try to get a stage by stage scenario re-created.

    Luckily, once you get the hang of it, it's quite straightforward.
     
  11. TANSL
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    TANSL Senior Member

    @rwatson, thank you for your efforts to teach us the method, very kind. I look forward to your explanations.
     
  12. TANSL
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    TANSL Senior Member

    @rwatson , I know that I have no right to ask for anything but the procedure indicated by you is so interesting, it would be so useful, that I dare to ask you if there has been any progress in "re-creating stage by stage scenario" and when we could expect to read something definitive about it .
    Once I understand the method, and with your consent, I would like to program it to include it in any of my applications.
    Thank you
     
  13. Insomniac
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    Insomniac Junior Member

  14. TANSL
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    TANSL Senior Member

    Some help that a CAD / CAM program, properly used, can provide.


     

  15. Insomniac
    Joined: Jul 2018
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    Insomniac Junior Member

    Thanks for sharing. I would like to give ARQN a try; however,I have AUTOCAD 2018 for MAC. I am guessing ARQN only works on a Windows version?
     
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