Composite forestay attachment point.

Discussion in 'Multihulls' started by Corley, Oct 9, 2011.

  1. DGreenwood
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    DGreenwood Senior Member

    The failure described here can be mitigated by distributing the fibers across a broader thimble or using two broad thimbles with a gap between them and a pin spanning them. Stacking fibers on a small radius curve is to be avoided. What your proposing is common stuff now and most designers that use carbon could give you guidance that would make a safe attachment point.
     
  2. Ajg2199
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    Ajg2199 Junior Member



    Is there a rule of thumb or ratio for how wide the fibers should be stacked?
     
  3. waynemarlow
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    waynemarlow Senior Member

    Always wondered about these guys in this situation, as long as it’s mounted correctly into the deck any stress relieving fibres can be built into the structure rather than the chain plate.
    [​IMG]
     
  4. revintage
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    revintage Senior Member

    The first to images sh0ws the carbon/G10/Divynicell bulkhead I made for my small tri foiler build.
    The sketch shows the forestay attachment I intend to use on my tri(250sqft SA, 9.5m mast) with a Nacra 5.8 hull as center. I could think of using a Kraken forestay, but I have no idea of how to do it with a light design. A bridle will be adequate, as the selftacking Tornado jib is designed to have its tack more than 1 ft above deck. Will be easy to implement as the glued deck can be removed rather easy.

    0skott2.png 1forestaybh.png

    bridle.png foredeck.png
     
    Last edited: Sep 11, 2022
  5. Ajg2199
    Joined: Aug 2022
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    Ajg2199 Junior Member

    What comes first in design, the chainplate or the hardware?

    Most of the composite chainplates I’ve seen cut a slot in the middle to fit the turnbuckle and secure it with a pin.
    Would it be difficult (or expensive) to find turnbuckles with legs wide enough to fit the outside of the chainplate? Using shackles to connect the turnbuckles to chainplates seems like it leaves more options, but it becomes a lot of moving parts. And the sizes would still need to be pretty precise to make sure the chainplate hole is appropriate to the shackle pin and that the turnbuckle fits the shackle.
     
  6. Corley
    Joined: Oct 2009
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    Corley epoxy coated

    Just out of interest I eventually decided to not take the forestay to the bow and will instead use a small structural furler and a composite chainplate with carbon spread over the correctly angled bulkhead underneath the Genoa where the roller reefing mounted in the past.
     
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  7. revintage
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    revintage Senior Member

    It´s about the same as I have applied to my small foiler. Think it is is the way to go, once you have a correctly angled and secured bulkhead to build on.
    About my tri I might try this corny asymmetric forestay as there is already a chainplate on one side of the center hull. The lower image is a mock up, with the tri in 2,6m trailer mode, in sailing mode it will be 4,6m. To spread the load I might also add double forestays, A-cat style(green).

    IMG_9742.JPG IMG_1065.jpeg
     
    Corley likes this.
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