Rebuild body-plan of 100 ft Sailboat

Discussion in 'Boat Design' started by Cacciatore, Oct 8, 2018.

  1. Cacciatore
    Joined: Oct 2008
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    Cacciatore Junior Member

    Hi Guys , anyone could suggest to me the best method to rebuild the bodyplan of a 100 ft Sailboat from the real hull ?
    3D laser scan with a drone ?? or anyone know an ''old'' simple method ?

    Thanks in advance
     
  2. rwatson
    Joined: Aug 2007
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    rwatson Senior Member

    3d Laser for sure. You don't want a drone, you have to know the scanning point.
    Get a point cloud for the "best" side, and you can reproduce the hull in minutes with CAD.
    Only way to go.


     
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  3. TANSL
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    TANSL Senior Member

    A 3D laser is the best tool to obtain a very fast and very expensive cloud of points that, processed by means of an expensive software, will allow you to sort and classify those points and eliminate the points that do not work, for, with other software, obtain a huge series of polygonal meshes that, although they will not allow you to do any naval architecture calculations by themselves, will allow you, with the right software, to obtain some surfaces of the hull that you will be able to handle with one of the multiple naval CAD / CAN programs existing
    A laser distance meter, very cheap, will allow you to obtain points of 10 or 12 cross sections, as well as the longitudinal profile, points that processed with a program like "Formas" (created by me self) will allow you to obtain in 2 or 3 hours the body lines plan of your boat. This done, in a few moments you will be able to obtain, if needed, the nurbs surfaces of that hull.
    If you opt for the second solution, which is cheaper but involves working several hours in situ , once the points have been obtained, I could carry out the process of generating the body lines plan for you.
    Cheers.
     
    Last edited: Oct 12, 2018
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  4. Cacciatore
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    Cacciatore Junior Member

    Thanks for reply Ignacio . The only issue is the obtain the cloud points of trasversal section without laser scanner 3D . You suggest to measure the offset space from shell plates to a perpedicular to the ground and tangent to gunwale ? How to proceed if the floor is not well levelled ?
     
  5. TANSL
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    TANSL Senior Member

    Leveling the floor is the main problem. If you can not get a correct floor it is best to draw a grid on the floor, using wires, which will form a fictitious base plan, and take measurements from that base plane.
    Although the ground plane is not perfect, the work with the sections in the computer, and the drawing of water lines, buttocks and bilge diagonals of verification, allow to obtain some results more than acceptable. It is a job similar to that of the old loftmen.
     
  6. gonzo
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    gonzo Senior Member

    If you are going to take the lines manually, the first step is to set reference lines and planes. That will create a coordinate system to measure from. By reversing the procedure you can redraw the lines. It is a time consuming process that requires a fair amount of experience and expertise. It will also be several times more expensive than a laser scan.
     
  7. TANSL
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    TANSL Senior Member

    @gonzo, here is an example of a boat model obtained by a 3D scanner. Apart from the fact that it is a very expensive process for a normal person, in time and money (although you, I do not know with what experience, seem to suggest that it is not expensive) , can you explain to me what would you do with a "thing" like this?
    Carmita.jpg
     

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  8. rwatson
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    rwatson Senior Member

    Tansl - that figure is NOT what was obtained by a 3d scanner.

    It is a grid created by using points obtained from a scanner.

    Now, to get the lines, all you have to do is develop a surface on the grid, create some frame points, and start creating the framing profiles.

    In any case, that diagram is what the OP was asking for. The "lines plan" of the boat.

    He could get all the dimensions he needs straight from that probably NURBS surface.
     

  9. TANSL
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    TANSL Senior Member

    You're right @rwatson. What I have shown is NOT what you get directly from the scan, but what is achieved after a process, not simple, of elimination of points, ordering of others, creation of meshes through points, etc ... All this edition process has to be developed with specialized software managed by specialized personnel. And, once the meshes of the hull have been obtained, it is necessary to eliminate and add some things. For example, for the naval architectural calculations, the bulwark does not work and must be eliminated; if the deck is not there, you have to create it, ... And now, as the meshes are useless, you have to create the nurbs surfaces, trying to make them pass as close as possible (even though you will never know how much) of the vertices of the meshes.
    If you limit yourself to working with the point cloud obtained with the scanner, you may end up desperate. In summary, 3D scanning allows you to obtain the 3D model of the hull, but it is not the fastest, it is not the cheapest, nor is it within the reach of most (if not none) of the boat designers.
    My advice, and I have used several times both 3D scanning and taking measurements by hand, is to use this second method. It is, simply, my experience, it is not the absolute truth. But, I think, my experience allows me to speak with more reasons than those who do not have that experience and have only read things on the web.
    All that is almost true. It is a description of what needs to be done, regardless of how it is done or the precision that is to be obtained. The problem is how to put it into practice in real life, and at what price.
     
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