Analysis of racking movement of superstructure

Discussion in 'Boat Design' started by ShafiqToha, Mar 28, 2011.

  1. ShafiqToha
    Joined: Mar 2011
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    ShafiqToha Junior Member

    Hi,

    I'm doing a thesis topic on the racking movement of a superstructure on a 80m catamaran. I was given a drawing of the ship but I'm really having difficulties on modeling the superstructure. What I have in mind in to analyze the 3D model of the structure using Ansys or Strand7. Can anyone here give me a few pointers.

    Cheers.
     
  2. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    ShafiqToha

    What you need it the GA and/or Lines of the supertsructure. Then you'll need the midship section dwg and the Deck and Profiles dwg. Once you have these, you have all the information to describe the superstructure in its correct dimensions and scantlings.

    Good luck with your thesis
     
  3. ShafiqToha
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    ShafiqToha Junior Member

    Thank you for your quick response. I do have the dwg of the whole ship and the major problem that I'm having is to model it. Is it best if I use Auto Cad then import the 3D model to Ansys?
     
  4. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    The best thing to do, which I still do today when i perform such analysis is to make it simple. Sure, you may be able to import the file via dxf or iges into Ansys or Strand, but you shall have a model that is huge, in terms of number of lines and keypoints. The problem comes then having to mesh it and trust the meshing etc etc.

    Make the superstructure from very simple shapes, which is usually the case anyway. Draw this in autocad, if your FE software is not so user freindly for modelling. Make the superstructure from literally just 3 lines per deck....1 for the port side, 1 for the deck and 1 for the stbd side. This is simple. Then add the other decks in the same way. But make sure that the deck above, where does the side finish...is it in the same location as the deck below, or slightly inboard. If inboard..break the line at this juniction, and then to the same 3 lines again.

    The hull is made in the same way, since you only need a stiff "box" to transfer the laods from the hull to the superstructure.

    Does this make sense?...see below:

    Basic FEM.jpg
     

  5. ShafiqToha
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    ShafiqToha Junior Member

    Thank you. That does make sense. I'll discuss this idea with my supervisor.
     
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