Sea Sled madness. It’s in my brain.

Discussion in 'Fiberglass and Composite Boat Building' started by DogCavalry, Nov 11, 2019.

  1. DogCavalry
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    DogCavalry Senior Member

    Between ram and B1, it goes through almost 30° rotation. Those points are only 36" apart. I can make that twist, but then it doesn't want to land on B2.

    Here are my temporary assembly screws. 1¼" particle board screws. 20200208_134955.jpg
     
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  2. bajansailor
    Joined: Oct 2007
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    bajansailor Marine Surveyor

    To save folk going back to page 3, here is the lines plan photo for reference.

    I am wondering, would it be feasible to plank this area with double diagonal locally in the area of extreme twist?
    Or as Bluebell suggests, keeping the 5/8" thickness, but halving the width to about the same from 1.5"?
    Would square section strips twist more readily than rectangular?

    Dog Cavalry Sea Sled lines.jpg
     
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  3. BlueBell
    Joined: May 2017
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    BlueBell . . . _ _ _ . . . _ _ _

    No, I was suggesting making the strips half thick at 5/16"
    and doubling them up, staggering the seams.
    But, I like double diagonal!
     
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  4. DogCavalry
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    DogCavalry Senior Member

    I was thinking to plank as far as I can, with the standard strips. Then a layer of ⅜ plywood out to the edge, and a layer of ¼ glued on top of that.
     
  5. DogCavalry
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    DogCavalry Senior Member

    The difficult rotation is between the ram and B1. B1 is the section immediately below the electrical outlet in the image Bajansailor thoughtfully provided.
     
  6. TANSL
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    TANSL Senior Member

    Could it be a solution to make a correct body lines plan, a fairing of the hull?
     
  7. bajansailor
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    bajansailor Marine Surveyor

    And further to Tansl's comment above, with that amount of twist shouldn't the frames ideally have some curvature (rather than being straight lines) - ie conically developed (rather like unwrapping an ice cream cone)?

    OK, conic development is designed for using sheet materials (rather than strips) - but if even strips cannot cope with the amount of twist in DC's bottom sections, then there is no way that (eg) plywood would, unless it is unwrapped from a cone and the frames have some curvature(?)
    https://www.boatdesign.net/attachments/multiconicdevelopementhullsurfaces001-pdf.82878/
     
  8. DogCavalry
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    DogCavalry Senior Member

    The surfaces through this region are certainly developable. The planks don't want to simultaneously curve around the frames, roll on their axis to lay flat on the frames, then arc sideways to hit the apex of each frame. Any 2, but not all three.
     
  9. TANSL
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    TANSL Senior Member

    Sorry but I don´t think so and I belive that is precisely the problem that you have.
     
    Last edited: Feb 10, 2020
  10. DogCavalry
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    DogCavalry Senior Member

    Well, you may be correct. I can certainly plank the area with narrower planks, or thin plywood, but I can't do it with my current plank section.
     
  11. DogCavalry
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    DogCavalry Senior Member

    A plank that runs from the tunnel b6 to b1 then turn to land on the ram, must have a large sideways arc. As if it was cut from a sheet of plywood, shaped like a field hockey stick. My straight planks are too stiff to distort that much.

    There are a number of solutions. I'm not defeated, just mulling over which option has the least difficulties.
     
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  12. BlueBell
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    BlueBell . . . _ _ _ . . . _ _ _

    TANSL raises some good points, of course.
    What are your possible solutions John?
     
  13. DogCavalry
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    DogCavalry Senior Member

    I need to reduce the dimensions of individual planks, to reduce stiffness. Losing that much stiffness at the critical intersection means adding a chine log though. I was going to do liquid joinery.

    Or finish the region in plywood, probably in a ⅜ layer, with a ¼ layer over top of that, then saw and plane off the overhang. That allows large motion in 2 dimension without trying to force the third as well.
     
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  14. BlueBell
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    BlueBell . . . _ _ _ . . . _ _ _

    Hmmmmm...
     

  15. DogCavalry
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    DogCavalry Senior Member

    Tonights stopping point 20200210_211952.jpg
     
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