How to draw a shell expansion plan?

Discussion in 'Boat Design' started by Alson An, Aug 16, 2019.

  1. Alson An
    Joined: Jul 2018
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    Location: UK

    Alson An New Member

    Hello!

    I am working as an Aluminium boat designer.
    Usually, the shell expansion plan was not needed among the key plans(for a small boat), but it is needed to be inspected. I've never drawn this before. Is there anyone ever done this? I would appreciate it if you could write a book or a link to know how to do this.
     
  2. JSL
    Joined: Nov 2012
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    Location: Delta BC

    JSL Senior Member

    What type & size of boat?
     
  3. jehardiman
    Joined: Aug 2004
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    Location: Port Orchard, Washington, USA

    jehardiman Senior Member

    Just measure off the lines plan and draft it knowing that the CL is a straight horizontal line. Starting at midships, lay out each panel between each waterline and station as a trapezoid where the heights are the shell girths and the top line (which could be curved) is the length along the waterline. You should get something that looks like this;
    Redirect Notice https://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&ved=2ahUKEwjxw83JhYnkAhVxMH0KHVzPBbgQjRx6BAgBEAQ&url=http%3A%2F%2Fcaptaindamley.net%2Fe-modules%2Fgeneral-ship-knowledge%2Fshell-and-deck-plating%2F&psig=AOvVaw1WIelwBqqtOs3t3wPnIyaI&ust=1566101691238357
    Sorry for the rant, but if you want to be a boat designer, you should be able to do basic drafting and lofting. This is bread and butter old school Naval Architecture that you should have done in Freshman year. Right now I cringe at all the people working in the field who cannot do plate cutting layout and plate development. Those are basic skills! Sorry, I'm going to go drink rum and sulk now.

    Edit: FWIW, the shell expansion is one of the most important drawings about a vessel, it not only shows where to block to repair damage, but a correct one will show all penetrations and sea chests which will need to be missed by the docking plan.
     
  4. Alson An
    Joined: Jul 2018
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    Location: UK

    Alson An New Member

    thanks for reply

    this is an oil skimmer boat. The shape of the hull is similar to the boat on the YouTube link below.


    its size is
    LH 16m
    beam 4.9m
    depth 1.70m
     
    Last edited: Aug 17, 2019
  5. JSL
    Joined: Nov 2012
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    Location: Delta BC

    JSL Senior Member

    A shell expansion plan should be simple for a barge hull form and from my experience, not usually necessary.
    Apart from showing plates it can be valuable to see where there might be 'conflicts' such as intersections of welds (butts and seams) with frames & internals. As an example, I have attached a photo (sorry- poor quality) of an expansion for a 44' steel ketch (round bilge) which did a circumnavigation 1991-97 Perelandra shell expansion lores.jpg
     

  6. Alson An
    Joined: Jul 2018
    Posts: 4
    Likes: 0, Points: 1
    Location: UK

    Alson An New Member

    thanks for reply.
    your plan was very helpful!!!
     
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