Question for Maxsurf experts- how would you model these surfaces?

Discussion in 'Software' started by nrg710, Jun 30, 2014.

  1. nrg710
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    nrg710 Junior Member

    I am trying to recreate this ship in Maxsurf, but not having a lot of luck at the moment (the ship, BTW, is RMS Titanic/Olympic/Britannic)

    Obviously I want to keep the number of surfaces to a minimum. So far, though, I am having real trouble trying to fit the bow curve. And I haven't even started on the transom yet and rear knuckles yet, but I am expecting that to be a total b*tch.

    The method I'm using might also not be the best, so I'd welcome your input here. I'm using the default 1/4 cylinder surface and attempting to manipulate this. However, it's proving quite difficult, because I don't find Maxsurf that intuitive.

    I've had a bit more luck using the skin curves function, but that still leaves the bow curve to be modelled and I've no idea how to do this.

    And any advice on how you would model the transom would be much appreciated.

    [​IMG]
     

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    Last edited: Jun 30, 2014
  2. TANSL
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    TANSL Senior Member

    Check out. It's done in AutoCAD using the command "loft" between water lines.
     

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  3. NavalSArtichoke
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    NavalSArtichoke Senior Member

    In general, it's very difficult and tedious to try to use modern tools to recreate a set of faired lines. These programs are set up to create a faired surface from scratch, and they don't have a lot of functionality to fit a surface using existing offsets.

    The whole idea of B-splines and Nurbs surfaces is to use the control points/control mesh so that the curve/surface can be changed by moving one or two points around. That's not to say what you want to do is impossible, it just takes a different approach.
     
  4. TANSL
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    TANSL Senior Member

    I totally agree with NavalSArtichoke. It is almost impossible with modern programs, generating the surface you need. They have a tendency, very marked, to make the surface they want.
    In my work I have to do in many cases the model of an existing boat and must start from a table of offsets to achieve as closely as possible the actual boat forms. I have tried several programs and none of them makes this process correctly. So I had to develop my own software which, from the ship's lines, generates in AutoCAD, in a reasonable time, hull surfaces (or a solid model) with all the accuracy that the designer wants to give. After obtaining the model in AutoCAD, export to MaxSurf, for example, is simple.
    I have to say, therefore, that what nrgt710 wants to do is entirely possible, though not directly in MaxSurf.
     
  5. nrg710
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    nrg710 Junior Member

    As I suspected, then!

    TANSL, when you say you developed your own software- is this readily available?

    I've used Autocad in the past, haven't used it for a while though. I'm more familiar with Rhino these days, but it wouldn't take me long to get back up to speed with Acad.

    Interesting also that you lofted between the waterlines for that shape. What sort of results did you get lofting between the sections?
     
  6. TANSL
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    TANSL Senior Member

    nrg710, you can access my software from my website.
    By lofting between cross sections generally do not get good results. Especially the bow and stern are modeled very poorly.
    This is my experience. No doubt others may have different opinions.
     
  7. bhnautika
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    bhnautika Senior Member

    Nrg710 If you divide the hull at chine lines with bonded surfaces you can get the stern corner also if you adjust the control point weighting and stiffness you can get different curvature where you want it, rather than adding to many points. I did a quick hull to show what I mean.
     

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  8. TANSL
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    TANSL Senior Member

    bhnautika, no doubt that the model you've built (in a fast way, like you said, and still developing) resembles the Titanic. The problem arises when you have to get the model of the Titanic and not a very similar model. Do you think you can bring your boat to the original model with sufficient accuracy?. I'm not saying that you can not, it's just a question. Do you think hydrostatic values ​​can have an error less than, let´s say, 3%?.
     
  9. bhnautika
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    bhnautika Senior Member

    Tansl this was only a modelling exercise but even so I scaled up the example file to full size, I adjusted the turn of the bilge to tighten them up a little as I thought they were a little soft. Even just using the buttock lines and profile from nrg710 original drawings I got a displacement of 50000 tonne Cp 69, Cb 66 pretty close to the original, which is not bad considering no sections or waterlines as a guide. I don’t think there is any table of offsets to my knowledge for this class of ship (I am probably wrong!), that only leaves digitised and printed line drawings which at best could be close but not that accurate. If I wanted a 100% accurate model of an exciting structure I would probably use a variety of different methods.
     
  10. TANSL
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    TANSL Senior Member

    bhnautika, I agree with you, your work is very correct. I did not really want to criticize what you've done, what I want to make is my belief that, with MaxSurf, is not easy (I think it's impossible) to get an existing boat reproduce with sufficient accuracy. I totally agree with you that, for this, we have to use other means.
    NOTE: I suppose a super-expert in MaxSurf, in time, is capable of performing wonders. The problem is that many naval architects are not great experts in modeling programs. And my opinion is that they should not be forced to spend much time on that task. For some of them this is a difficult obstacle to overcome, forcing them to rely on other people.
     
  11. nrg710
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    nrg710 Junior Member

    bhnautika, your model is extremely good! As far as I can see, it's 3 surfaces bonded together, and it does give me a pretty good idea of what I should be doing- thank you.

    If someone wants to try and reproduce RMS Titanic accurately, I can supply the msd file with the background images and the design grid already set up.
     
  12. bhnautika
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    bhnautika Senior Member

    Nrg710 if you add another surface up above the sheer you can trim that to get the steps of the original sheer line.
    Tansl no offence taken and the more tools available the better.
     
  13. JosephT
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    JosephT Senior Member

    Are these the only lines available? If you have pictures/lines of the loft from a profile, top and the bow & stern would be much easier to replicate the hull very closely. At present you only have the profile and this is not enough. The current view just leaves out too much information and will leave one to guess a lot.
     
  14. TANSL
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    TANSL Senior Member

    Could you provide us the background images?. I´ll try to do something with them.
    Thanks
     

  15. nrg710
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    nrg710 Junior Member

    I am working on setting up a MSD file with the correct zero points, references, FP, AP etc. Should have it done in the next day or so and will make it available then- thank you, TANSL! :)
     
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