Multihull software?

Discussion in 'Software' started by Guest, Oct 9, 2003.

  1. Guest

    Guest Guest

    Has anyone got info as to WHAT sofware is capable to designing a multihull?
     
  2. nico
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    nico Senior Member

  3. Chris Krumm
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    Chris Krumm Junior Member

    Nico -

    Does Multisurf include hydrostatics for multihulls (or monos, for that matter) within the surface modeler, or do you have to purchase Hydro?

    Also, is the software actually capable of performing hydrostatics at various degrees of heel and trim for a multihull? I'm really curious, because the other programs I'm familiar with do not have that capability. If so, sounds like the answer. If not, programs such as ProSurf or Rhino will allow you to model a multihull, even though they will balk at the hydrostatics. Not to say MultiSurf isn't a good program, but that there are other options.
     
  4. nico
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    nico Senior Member

    Multisurf includes a detailed hydrostatics. Hydro will be able to draw Section area curve (Multisurf doesn't), and will draw GZ curve.
    Multisurf is capable of performing hydrostatics at various heel and trim angle. But will not iterate to match LCB-LCG by itself.

    Multisurf is an impressive program, the parametric capability is great, and the OLE links are easy to use to develop customised add-ins to multisurf.

    Nico
     
  5. Andrew Mason
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    Andrew Mason Senior Member

    Maxsurf can model multihulls of any complexity and its associated stability program Hydromax can do complete large angle stability analysis (plus much more) with free trim.
     
  6. Chris Krumm
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    Chris Krumm Junior Member

    Nico -

    Will Multisurf do hydrostatics for a 2 or 3 hull system (separate, "isolated hulls") at a single angle of heel, or will Hydro do the same iteratively for progressive heel angles? or would you need to use OLE functionality to develop your own applet for this?

    Andrew -

    Same questions as applied to Maxsurf and Hydromax.
     
  7. Andrew Mason
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    Andrew Mason Senior Member

    If you mean can Hydromax analyse multiple disconnected volumes the answer is yes, as long as they are not articulated i.e. they must be rigid with respect to one another rather than free to rotate independently.
     
  8. Guest

    Guest Guest

    Chris

    Multisurf will do hydrostatics for any number of hulls. (of any shape). In fact Multisurf is a 3d surface modeler which can be used to model everything.
    In multisurf before entering the hydrostatics window, you ll input the heel angle and trim angle. You can't (directly into Multisurf) input a heel angle and let the program find equilibrium by changing trim angle to match LCB-LCG. This is where programs like Hydro or Hydromax come in.
    For a first user of such programs, Maxsurf is by far easier to use. But multisurf will do much more when mastered. Unfortunately Hydromax (Maxsurf range) is better than Hydro.
    As I am a student and I use the programs at uni, i start with multisurf and use Hydromax.
    But for commercial work, buying multisurf, maxsurf and hydromax is a problem.

    Nico


    Multisurf and Maxsurf will do almost the same hydrostatics (Maxsurf does section area curves, Multisurf doesn't). The other difference is that directly into Multisurf you can specify a heel (or trim) angle, but for a specified heel angle multisurf won't change the trim angle to match LCB and LCG . You ll need hydromax or hydro. Hydromax is very good.
     
  9. Andrew Mason
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    Andrew Mason Senior Member

    Nico

    As the author of Maxsurf I would take you to task on your evaluation of Maxsurf versus Multisurf. I agree that Maxsurf is easier to learn than Multisurf and I also agree that Hydromax is a much better program than Letchers's Hydro.

    However I do not agree that you can do much more with Multisurf when you master it than you can with Maxsurf. Although Multisurf's paradigm of relational surfaces is attractive to many, I believe Maxsurf's approach of using multiple intersected and trimmed surfaces is ultimately more powerful.

    I think John Letcher has done a good job convincing the marine design market that the supposed advantages of relational modelling are worth the trouble involved in dealing with an arcane and complex user interface. I for one am not convinced.
     
  10. nico
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    nico Senior Member

    I find Multisurf great in several ways :
    You have many choices of surfaces, curves etc. So you have to understand how they work to use them, I think it is important to understand how these programs work.
    Multisurf is easily customised, OLE capability is great, and relational geometry can be interesting.
    Ergonomics is better, ctrl+mouse to zoom, alt+mouse to pan, etc


    But Multisurf is a slow program, hydrostatics are not real time.
    I don’t think relational modelling is particularly interesting; it is too time consuming to use.

    Finally as a student and not counting my time, I can design in Multisurf export in Maxsurf and then to Hydromax. But it is obviously time consuming. As a yacht designer I would choose the Maxsurf because of the power of Hydromax.


    Nico
     
  11. Andrew Mason
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    Andrew Mason Senior Member

    I guess that's the difference in the philosophy behind the design of the programs in the Maxsurf suite compared to Aerohydro's software .

    Mutisurf seems to be written with the "more is better" approach-more surface types, more commands, more complexity. Unfortunately the result is a program that most dismiss as being too complex and too hard to learn. If you are the sort of person who thrives on solving cryptic puzzles, and secretly yearns for the return on the DOS command line interface, Multisurf is the program for you.

    With Maxsurf and its associated programs we try to subscribe to the "less is more" approach - why have a multitude of different and sometimes problematic surface type when you have one surface type (NURBS) that will handle virtually any geometry task required. NURBS can represent simple points, vectors, polylines, circular arcs, ellipses, free form curves, surfaces and solids. This is the reason that NURBS are so widely adopted in the CAD community and why they have become the standard for hull design geometry worldwide.

    I feel that the key to design programs such as Maxsurf is taking what is an incredibly complex subject and presenting it as simply and as logically as possible. Judging by the number of people we get commenting on Maxsurf's ease of use, I think we have suceeded. However you should not interpret this as a lack of power in the software, Maxsurf has been designed to be as simple and consistent as possible without losing the capability to perform modelling of complex or unusual shapes.

    Note that we have not tried to make Maxsurf a general purpose surface modeller in the same mould as Multisurf or Rhino. Maxsurf is primarily intended for the creating of hull shapes and superstructures, it is not intended to be used for creating detail down to the level of windows, liferings and guardrails. This is where Rhino comes in and the roles of the two programs should not be confused.

    On your comment that Multisurf's ergonomics are better, Maxsurf uses the mousewheel for zoom in/out and the center button click and drag for pan, I believe this is consistent with the user interface used by AutoCAD and is what several other CAD software suppliers have chosen.
     

  12. tspeer
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    tspeer Senior Member

    You can do multihull hydrostatics in Multisurf, but it's not as straightforward as you might think. You really need to do each hull separately - you can't just designate all the hulls and let'er rip. And the Multisurf's Hydro program won't handle multihulls at all from what I've seen.

    However, it turns out Multisurf's fundamental hydrostatic calculations are built into the program itself - Hydro is just a user interface that accesses them. And since Multisurf supports Object Linking and Embedding (OLE), you can link Multisurf to other programs. Like Excel.

    So you can have Excel call the hydrostatics routine in Multisurf and get the data back in Excel. Excel can query Multisurf for each of the hulls in turn. I've used this capability to build up tables with regular variations in pitch, roll, and heave, and then interpolate between them to produce center of buoyancy contours.

    The result is a multihull footprint like this: http://www.tspeer.com/temp/hullbalance.gif that can be compared with the virtual c.g. from the sail loads.
     
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