Hydrofoil collision safety

Discussion in 'Boat Design' started by Storm_Eagle, Oct 27, 2020.

  1. Storm_Eagle
    Joined: Aug 2020
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    Location: Norway

    Storm_Eagle Junior Member

    Hydrofoils colliding with underwater objects and animals can have big consequences as the ship is usually traveling at high speed and will stop pretty fast when the foils are caught on something like a whale or a anchor chain.
    But can this not be mitigated by design? By designing a weak point in the attachment points of the foil struts so the foils brake away if a sudden large force occurs. The ship will then fall down the small distance to the water but not have such a major crash as with the foils attached by a weary strong point.

    Is this done on any hydrofoils? And if not why?
  2. portacruise
    Joined: Jun 2009
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    portacruise Senior Member

    This is a link to and old hydrofoil design that used shear pins, which worked fairly well. There is a couple of stories about collisions, apparently even a plastic bag Tangled in the foil was a safety concern!

    http://histarmar.com.ar/InfGral/Hidroalas/TheUp-RightHydrofoil Kits.htm

    Search The Up-right Hydrofoil Kits by Tom Lang, if hot link not working.
    Collisions story after Figure 6, and also the fifth paragraph of the addendum.
    Last edited: Oct 27, 2020
  3. Mr Efficiency
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    Mr Efficiency Senior Member

    Shear pins do come to mind, but maybe also a shock absorber of some kind so it does rotate back and smash the hull.
  4. Doug Halsey
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    Doug Halsey Senior Member

  5. BlueBell
    Joined: May 2017
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    Location: Victoria BC Canada

    BlueBell . . . _ _ _ . . . _ _ _

    For us here on the Canadian west coast, hitting debris in the water is a common occurrence.
    Including deadheads, and more shore logs than you can shake a stick at!

    To be practical, they need to break away and then reset instantly
    as one cannot to be sitting dead in the water while replacing a pin.
    This is hugely challenging to overcome.
    As a result, you don't see hydrofoils around here.
  6. Doug Halsey
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    Doug Halsey Senior Member

    Even just hitting a strand of kelp can be problematic. I've pitchpoled my Moth that way.

  7. kapnD
    Joined: Jan 2003
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    Location: hawaii, usa

    kapnD Senior Member

    I’ve tinkered with the idea of hydraulically deployed foils that would give way to overpressure for this purpose with a
    large pressure relief valve.
    The initial impact would still be a jolt!
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