Foam core: Planking Split up

Discussion in 'Fiberglass and Composite Boat Building' started by AJP, Oct 1, 2019.

  1. AJP
    Joined: Jul 2019
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    AJP Junior Member

    Hey Guys,

    Just wanted to get few ideas on building a 10 m vessel using strip on plank method.

    i would like to split the hull into two and join it at the end. Any ideas on how to join the cores at the end, I do understand that laminating on top and bottom is done for solid fibre construction, but when it comes to sandwich construction how do we get a good bond between the cores during joining the individual parts together.
     
  2. Mr Efficiency
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    Mr Efficiency Senior Member

    Sounds like an unusual method of construction. Regardless of that, the core doesn't need to be continuous, or bonded together, in any cored construction. But the skins do.
     
  3. AJP
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    AJP Junior Member

    Just trying out possibilities due to limitation in space Mr.efficiency, and a scarf joint between the core would be advisable?
     
  4. TANSL
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    TANSL Senior Member

    Any image of how and where do you want to make the union? Is it a section of the hull by a longitudinal or transverse plane?
     
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  5. fallguy
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    fallguy Senior Member

    You would not need to scarf.

    Typically, butt joins are sufficient.

    Then vacuum bagging, for example; there is enough flow that the seams are well bonded.

    However, you won't have a continuous glass and your bonding at that seam or over it will be all secondary.

    And then you will probably rebate and tape.

    But somewhere at the join, to me at least, I would want primary bonding, or if secondary bonding; something larger and continuous.

    And then this means no bulkhead should be near the join which is also simply good construction and I believe a standard.

    The difficulty will be getting it to look right/stay true as the slightest bit of angle will show amd require major fairing.

    Scarfing is of little benefit. In foam construction; the epoxied butt join is much stronger than the foam.

    What you need to focus on is the glasswork.

    You can also strengthen the area from inside with stiffeners for mental comfort, if you will. A shelf, or shelves, for example, well bonded and continuous over the seam. Or just stiffeners.

    I would first avoid the method.

    Second, if no other option, try to secondary bond the seam with some xtra glasswork inside. Or if primary, better still. But not sure how you'd do that.
     
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  6. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    If you were going to do all the planking and infuse the entire hull; you would have continuous glass and primary bonding.

    But you have a space constraint. At some point you need to reconcile the space problem.

    Really, you need to explain how you will be glassing it for anyone to help you.

    A much better option is accommodating the build.

    This is a 36' deep building, but the prime real estate for the cabin base was here. This was up for a month until laminating was done.
    6EC2858D-8DCC-4B07-A1F0-EA7F9A2B5544.jpeg
     
  7. ondarvr
    Joined: Dec 2005
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    ondarvr Senior Member

    You can join the sections just about anywhere you want, although some places make it easier.

    Not sure what you mean by “the end” so a sketch or pic might help us understand a little better.

    As mentioned, nothing special needs to be done with the core, virtually ever seam in the core is already a butt joint.
     
    Last edited: Oct 1, 2019
  8. waikikin
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    waikikin Senior Member

    Hi AJP
    Sounds similar to Ian Farriers approach to trimaran hull construction(RIP).
    Reusing the form in mirror configuration for the second half- link- The composite construction of my Farrier F-39 trimaran http://www.fram.nl/construction.html
    As above the core can be butted however continuity of structural fibre across the join vital- on a one off this requires a wide tape internal and external with associated fairing operation, in contact molds the core can be installed after the external skin join complete then internal skin completed.

    Jeff
     
  9. fallguy
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    fallguy Senior Member

    So the exterior skin is done; then the core is glued in, then an interior skin?

    Any possible way that can be done in a split?

    Don't see how.
     
  10. waikikin
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    waikikin Senior Member

    In female contact molding with split molds no problem. External skins are laminated to the centreline, the core is left out either side of the centreline join for 100 to 150mm then the tooling brought together and flanges bolted then the external skin joined with prescribed laminate across the join 200-300mm wide, the core installed then the internal skin can be completed also across the join of 400-600mm wide- some tidy up will always be needed externally .
    On a one off hull without tooling you're nearly always going to need to add a bandage of laminate both sides unless someone invented a better way- not impossible but- the skins can be quite thin and easily damaged-- repairs can often be done from one side only with core removed, skin completed then core reinstalled . At least with the centreline join fairing is not so hard.

    Jeff.
     
  11. AJP
    Joined: Jul 2019
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    AJP Junior Member

    Hey All,

    Thank you for your really informative replies,
    so my whole idea was to make a hull for the initial sea trials and then use the same as a male mould to get the final hull. I was planning on splitting up the hull transversely in two sections and pinning down the cores, further joining the two strongbacks together and glassing them up by hand layup ( so that there wont be any discontinuity for the fibers) in an open spaces, And add the bulkheads and the stiffners at the end? Any thoughts on the same?
     

  12. fallguy
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    fallguy Senior Member

    It sounds like a big floppy mess when removed from the mould.

    I was advised against on a 10M powercat build and followed the recommendation to go female jig/mould.

    I think you'll need too much glass to hold the shape before stiffening to just lift off.

    If you built the inside; that would not be an issue. Of course this means a lot more work unbuilding the original hull assuming stringers, etc.

    Perhaps there is some other way to help keep the shape. In a female mould, you can walk right in...pretty handy. Add BHs perfectly to design lines. This was a good way to build for me. We did have some panel movement to deal with in fairing and I really should have ended short and noseconed the beast instead of building back to 2" wide.

    Perhaps others here will have ideas on how you can do it. I am worried you will be super floppy coming off.

    DC737973-0E65-4D01-A8C7-CDC79A65A950.jpeg
     
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