Create a listing hullform

DELFTship forum Hydrostatics and stability Create a listing hullform

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    • #36477
      giorgio zuppin
      Hello everybody, here is a question that I think would be of some interest:

      It is possible, with the free program, to create a hull, in that case of a sailing boat, rotated around its longitudinal axis by steps, for ex.: of 5°, in order to obtain hydrostatics data for different listing angles?

      I’ve tried, but since I’m just exploring the various tools, I have found the process a bit cumbersome:-draw a non simmetric hull-rotate-mirror-assign hydrostatic property to layers-

      The result was aesthetically good, but I lost full hydrostatics, the grid had to be cleaned of all unwanted points before to mirror and it was not possible to do it completely, so I got plenty of invalid edges: in a world a Fail.

      All answers are wellcome, thank you in advance.

      P.S. Attached is a Jpg image of the Fail.

    • #36485

      I’m thinking that your hydrostatics disappeared because you have inadvertently created a leak point somewhere in your model. I don’t believe that the program will give hydrostatics along varying degrees of angle.

    • #36486
      giorgio zuppin

      Thanks MAL, there are no leaking points, hydrostatics data are still calculated, partially,
      The problem is that the program is limited to simmetric hullforms, so to display listing boats you have to do some tricks.
      Obviously it does’nt work, not at all at least
      What I wanted to achieve ( hydrostatics for listing angles, in order to have a better knowledge for the design process ) it could be a bit complicate: I’ve got some informations here and there and the answer is – cool down and buy a full 3D dynamic flow simulation program, or build a model and be patient –
      When you search for shortcut it doesn’t work ever!

      A goodbye with my respects, Jurgen.

    • #36489
      Klaus -Peter Knopik

      Hi Jürgen,

      what you are looking for is implemented in PolyCad. You need to export the model from Delftship with STL-format >>EXPORT in ASCI-Format<<. Import that file in PolyCad an you can do what you need in "Calculation / Free Hydrostatic …". Enjoy it …

      Klaus from Kanu-Werft

    • #36490
      giorgio zuppin

      Thanks for the reply, I’ve just downloaded PolyCad and I’ll try your suggestion.
      Jurgen 54

    • #36493
      Jesus Cruz

      Where can i get polycad??

    • #36495
      giorgio zuppin


      Download the trial and and have a nice day.

    • #36521

      Jurgen, very nice work with that 40feet cantingkeel! I only suggest you to check the spreaders distribution 😉 .
      Delftship free can perform heeled hydro but in a very basic way, and it will NOT do it over a range of heel angles, so the job can be done but being very patient. What I do usually is a simplified model having just the heeled hull and a 3Dpoint showing the CG position. All I do is rotate over “x” (heel), move up and down and trim (rotate over “y”) until CG vertically fits CB while displacement remain unchanged. Anyway, check this post for a Cp issue that DS shows when calculating hydro in symetrized objects:

    • #36523
      giorgio zuppin

      Well, it works.
      Since I’m not pressed by time, I can – been patient – do small tests step by step.
      It’s not a breakthrough but it works.
      So here’s the prize: For your eye’s only (!!??!!) the 40′ feet in its splendour.

      P.S.: You’r right about the spreaders, I’ve scaled up a previous mast and
      obviously forgot some “details”:

      thanks Jurgen.

    • #36524

      Absolutely amazing job, Jurgen! thanks!
      Just a cup of hints in DS:
      – Activate the “Coef based in actual dimensions of submerged body” option.
      – Deactivate the “Default at 0.5*L” option of the Midship location, and fix it at the real “x” position of your maximum immersed area (check your curve of sectional areas).
      – To do a proper curve and locate the real maximum immersed area, you must deactivate hydrostatics from all layers but the hull (or Canoe Body if you prefer).
      Then you’ll find your Cp is too high, I would try a bit more Tc shifted to bow.
      There is a hinge at 1/4 from stern, it reminds me an IMS yacht. IMHO, that shape will reduce planing capabilities, I would try a smoother transition there.
      Thanks, it’s a beautiful boat!

    • #36525
      Klaus -Peter Knopik

      Polycad can be downloaded here. You have to registrate but the use is for free.

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