Shell plates and hull lines.

Discussion in 'Software' started by Alexanov, Oct 14, 2020.

  1. Alexanov
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    Alexanov Senior Member

    Find in internet picture of such new building. Is it only shell plates problems or also hull lines? upload_2020-10-14_21-3-28.jpeg
     
  2. jehardiman
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    jehardiman Senior Member

    Neither, it is fabrication ease.
     
  3. TANSL
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    TANSL Senior Member

  4. Alexanov
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    Alexanov Senior Member

    Shell plates subdivision looks very unprofessional for me.
     
  5. TANSL
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    TANSL Senior Member

    Certainly very unprofessional, it looks as if it were a poorly done repair on the initial shell plates.
    The technical and material resources were probably very limited.
     
  6. Ad Hoc
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    Ad Hoc Naval Architect

    In what way ...?
     
  7. Alexanov
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    Alexanov Senior Member

  8. Ad Hoc
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    Ad Hoc Naval Architect

    Alexanov:

    That doesn't answer my question.. what do YOU think it is 'unprofessional'....?
     
  9. TANSL
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    TANSL Senior Member

    @Alexanov, very good article, very useful.
    Do you have any writing on methods for "developing" (approximate) non-developable plates?
     
  10. Alexanov
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    Alexanov Senior Member

    Most of biggest plates has a lot of double curvature. Guys in workshop had a big troubles to bend it correctly. Usually seams need to be placed in areas to minimize double curvature and deformation inside one shell plate. Big plate in upper par of the bulb has too much curvature. Additionally, seams must be more even and naturally distributed around hull shape. It is not only help to produce and weld peace of metal to the hull, but looks more esthetic. At this picture it is more like Piccaso touch. Looks like designer, who making model, has very little knowledge how it will be produced at workshop.
     
  11. Alexanov
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    Alexanov Senior Member

    Algorithms for non-developable plates is quite complicated. In Shape Maker we use shell expansion method based on rectangular mesh. Surface splitting for belts, than they join each other. Condition for joining is equal between gap and overlapping areas. I know, in new version of shell plates developed in Cadmatic, they use something similar but on triangle mesh. Never seen any algorithm description. Usually such development take a long time with a lot of tests and trials.
     
  12. TANSL
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    TANSL Senior Member

    As I understand it, the FORAN software package uses conical triangles to reproduce the shapes of the hull.
    But I was referring to some of the manual methods used, before computers, for complicated developments: the straight base method, the geodesic line method, ... I know the names because I studied them when I was a student, but I no longer remember the procedures. I think they would be relatively easily programmable to create simple and cheap applications applicable to small boats.
     
    Last edited: Oct 15, 2020
  13. Ad Hoc
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    Ad Hoc Naval Architect

    That is hard to state in a 2D image of a 3D shape.

    There "appears" only one major plate that could be suspect this one:
    upload_2020-10-16_7-38-22.png

    But without seeing the front/bow view...it is hard to state categorically this is the case.
    Since this could be part of a large conical shape:

    upload_2020-10-16_7-41-37.png


    That is always the objective.
    But whether it is possible in practice is never clear until you begin the actual assembly - which is usually dictated by the skill of the fabricators and the equipment they have to hand to produce such shapes..

    Vessels of this size are usually faired by the mould loft. These personnel are extremely skilled and knowledgeable in hull lines & plate development.
    If however, it has been done all by software, like most things software related, it could simply be a case of the software being the master and the user the slave (i.e the software is incapable of doing what is wanted)...and this is about all that was possible.

    Unless one wishes to have endless smaller plates which = more labour = more time = more money.

    Everything in design is a series of comprises. Including production.

    Thus, I wouldn't be too quick to judge on these issues...
     
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  14. jehardiman
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    jehardiman Senior Member

    Alexanov, I take it you have never had any actual yard experience. In my old office we had piece of steel about a meter long and ~ 20x40mm. On one side was written " 'Splain stick" and on the other side was "Obvious meter". I am now going to figuratively pick that stick up and hit you with it....
    Now I have picked up a few pounds since I turned over "yard and docks" to the younger guys in the office before I retired, but not too many years ago I was ~100 kg and I'm still 1.98 m tall. Look at that picture you posted; that whole bow in the picture is ~3m x 3m, which means I can just about span it with my arms. And based on the welds, I doubt the plating is over 6mm with a maximum 500mm frame spacing. There is no way in hel, you are ever going to get any modern welder, in kit, up inside that. I bet that whole plating set weighs less than I do and was done with single sided welds. Unlike some of the inter-war French ships, nobody today is going to hire a tribe of pygmies to do internal work. Some of those "plates" are about the size of one, and I can't even see one larger than 1x2m. And they are that small to make sure you land on the backing bars on alternate frames, with the welder reaching in to the frame bay to skip weld alternate frames. I suspect most of the "plate forming" was done with dogs, a torch, and a sandbag; we used to call something small and thin like that "tin bending" in the yard, because compared to 20mm plate, it is.
     
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  15. baeckmo
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    baeckmo Hydrodynamics

    My spontaneous comment (with experience from the traditional lofting procedures) is that the bulb and the transverse thruster are "afterthoughts" (look at the difference in color); I wouldn't be surprised if you found parts of an origininal stem structure behind the clowns nose. Judging from the depth markings, there should be space enough to work from the inside (I'm over 6' tall and I've been in those corners chipping and back-welding), but as Jehardiman says, it looks as if it is an "outside job", cramped by remaining paraphernalia inside. This is why I speculate about "afterthought.

    The hull plate attached to the thruster does not meet the plate above tangentially, but with an edge. What happens forward of the vertical seam close to the depth markings would not have passed the lofting master where I was practicing, and the seam divisions are strange in comparison with the rest of the skin. Either it was an in situ "design", or the panel division done by elbows on a computer. Would be interesting to know more about her!
     
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