Construction method with prefabricated sandwich panels

Discussion in 'Boat Design' started by HJS, Oct 28, 2020.

  1. HJS
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    HJS Member

    Here we present a simplified construction method that directly create a hull with a perfect finish without going through the production of a mold. The method is suitable for all boats that are usually built in sheet material, such as plywood or sheet metal. It fits all sizes of boats, everything from small canoes to large yachts.
     

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  2. pironiero
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    pironiero Junior Member

    What about stitches between panels? They have different density and elasticity than panel itself and I'm pretty sure it will be noticeable
     
  3. Olav
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    Olav naval architect

    Jürgen, thanks for sharing, this is a nice building method!

    Here in Lübeck, Germany, there is the Baltec Shipyard where they build catamarans using a similar approach: Standardised foam sandwich panels with a quasi-isotropic (quadraxial iirc) glass fibre layup are laminated beforehand and then the developed panels are cut using a cnc router. All panels are joined using epoxy fillets and glass tapes.

    I used to have a very elaborate paper written by their structural engineer but cannot find it anymore. I remember there was a rule of thumb regarding the minimum bending radius of the sandwich panels as a function of their thickness. The minimum radius was quite large, indicating that this method would lend itself for rather slender hulls with little curvature in the panels.

    What is your experience in this regard?

    Thanks in advance!
     
  4. HJS
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    HJS Member

    The problem has probably rather been that the panels are too flexible. Longitudinal stringers have been required in the external templates.
    In sharp curves it may be appropriate to cut grooves in the core. In this example, it is seen at the bow.
    JS
     
  5. DCockey
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    DCockey Senior Member

    Thanks. It appears to be a very useful method for suitable shapes. How is the thickness of outer laminate selected? Have you had a situation where the outer laminate is too stiff or cannot be bent in a tight radius without cracking or other failure?
     
  6. HJS
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    HJS Member

    The dimensioning of the laminate thickness is done as with ordinary sandwich laminates to meet the requirements of the classification societies. There have never been any problems with bending the panels.
    JS
     
  7. Doug Halsey
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    Doug Halsey Senior Member

    Am I correct in assuming you can only build developable shapes that could also be done with plywood?
     
  8. HJS
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    HJS Member

    Based on my experience, plywood has a limited ability to be bent. With this method, the panel can be bent much more as long as it is developable. This is clearly seen in the illustrations at the bow.
    JS
     
  9. Squidly-Diddly
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    Squidly-Diddly Senior Member


  10. Mr Efficiency
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    Mr Efficiency Senior Member

    There are schedules available that show the bending limits of various thicknesses of ply, GRP sandwich panels I haven't seen the equivalent, but I expect the limitations are imposed by the total thickness, more than the skin thicknesses ?
     
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