Rhino3d Script to get trim angles for different heels

Discussion in 'Stability' started by Tapsa84, May 22, 2016.

  1. TANSL
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    TANSL Senior Member

    I can help you check your results with my own programs and with MaxSurf. But the first thing to check is that the models created with each program are exactly the same. If this is not so, not worth checking anything.
    It is even possible that importing files from one software to another the information is changed.
    The first would be to do a quick check of the hydrostatic values to focus more the problem.
     
  2. vv3k4i
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    vv3k4i Junior Member

    Theoretical tests can be also accurate. In the document I have attached there is an example of test case proposed by ABS, and the document contains some small angle data to compare with as well as reference to other documents with reference data.
     
  3. Tapsa84
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    Tapsa84 Junior Member

    Much appreciated, thanks.
     
  4. Tapsa84
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    Tapsa84 Junior Member

    Rhino3d stability calculation plugin

    Finally on my summer holiday! It took 3 days of hard coding, but it seems that I am finally there! I have some issues with performance, but I think I can fix it by coding the hydrostatic-measurements from scratch. At the moment, I am using the built in script from Rhino3d, and for some reason it is adding lots of latency. Everything else works super fast, especially if I turn redraw off.

    So, I have attached a screenshot of an analysis from a shallow draft 17 meter sailboat hull, which is emulating a Dériveur intégral design, which has no ballast in the lifting keel. I will be doing more testing with an added pilot house and also on the effects if free floating trim is removed.

    TANSL, if you are still interested in doing a comparison, please let me know. Would be nice to see how it compares to other software. I have been also looking on adding a weight management system, so one could calculate the center of gravity in Rhino3d. At the moment, I have been using Autodesk Inventor for weight studying, but a thought has grossed my mind to just make a similar plugin for Inventor.
     

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  5. TANSL
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    TANSL Senior Member

    Of course I'm interested in helping you and compare results. Send me a 3D model, or at least a 2D body lines plan, to work.
    I do not recommend that you use several applications to perform calculations because that would be very expensive and complicated for a non-expert user in applications that you have chosen.
    When analyzing the figures of your previous post it is not very clear what you mean by hydrostatics. For each list or/and trim you have to calculate the values of the hull and the coefficients at various drafts. I do not know if that's what you are calculating.
     
  6. Tapsa84
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    Tapsa84 Junior Member

    Many thanks!

    Can you specify, in which format I could send the model in? Just in case Rhino3d is supported, I have attached the model I used in my stability calculations. It has the center of gravity point included inside the model. Also, it is not by accident, that the center of gravity is not inline with center of buoyancy in the model. :D I needed to see, that it will actually trim the boat to show how it will float with no heel. This will allow to just drop any model with it's specified COG to see how it will actually float and be trimmed.

    Displacement for the model should be 13900kg and the water density I used was 1kg/dm3. Just for simplicity's sake.

    What I meant with the reference to Autodesk Inventor, was just to make a similar stability calculator plugin also for Inventor. I checked the Inventor SDK, and it looks doable.

    You are correct in your assumption about what I mean by hydrostatics. It contains all the relevant data related with the immersed part of the hull. Including but not limited to displacement volume, center of buoyancy and center of flotation.
     

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  7. TANSL
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    TANSL Senior Member

    Atteched file with MaxSurf calculations for your model : Hydrostatics values
     

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  8. Tapsa84
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    Tapsa84 Junior Member

    Thanks.

    Can you also get the righting arm curve and the associated trim figures for it?

    vv3k4i, would you be interested in doing the same with your plugin? I could also run one of your models with mine?
     
  9. TANSL
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    TANSL Senior Member

    What is the position of c. of g. for the load condition of 13900 kg?
     
  10. Tapsa84
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    Tapsa84 Junior Member

    When transom surface is vertical, it is 7600mm from transom and 1000mm up from the lowest point of keel. It is in the same position as the COG point inside of the model.
     
  11. TANSL
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    TANSL Senior Member

  12. Tapsa84
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    Tapsa84 Junior Member

    TANSL, I owe you one! Big time. My results are spot on with the ones you provided.

    I could tweak the accuracy up also. Displacement is adjusted to +- 2kg and LCG and LCB are adjusted to +- 10mm. I would just need to code the hydrostatic-calculations part again to get more efficiency. The one provided in Rhino is adding too much latency. I am also making the calculations for each degree of heel. I could make less heel points and use least squares to fit the points to an equation.

    Once again, many thanks for your time. If you ever happen to visit Finland, I will buy you beer! :D

    Edit: And for anyone else reading this thread, I think I will make this plugin available free of charge. I will need to tweak it up, add few more features, and also do extensive testing to make sure the results are inline with reality. I will also start to work on adding a weight management system, so the COG determination can be made "in house".
     
  13. TANSL
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    TANSL Senior Member

    Tapsa84, you're welcome. If I can do anything else for you, I am at your disposal.
     
  14. vv3k4i
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    vv3k4i Junior Member

    This is very nice you are getting the results correct. I tihnk that simplle stability calculations plugin for rhino in 21st century should be easily accesible, so this is nice you want to share this. I would still like to see one case checked with your algorithm in 0-180 deg range, and the model is attached. This is very nice case to check.
    COG data: LCG = 22.51 m, TCG = 0 m, VCG (KG) = 24.37 m Displacement 11.644 T.
    You will have to align the model with your coordinate system. Aft is this wide part. The model in my file is placed along X axis.
     

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  15. Tapsa84
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    Tapsa84 Junior Member

    Sure thing! I will run it soon as possible and post the results here.
     
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