Back to the Future

Discussion in 'Boat Design' started by Ad Hoc, Nov 3, 2020.

  1. Ad Hoc
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    Ad Hoc Naval Architect

    In addition to Bill's commentary (that no cat's have flipped - commercial cats at least), the foundations for the foils are designed, well, that's how we design them, to break free under a given load.
    So all you do, is lose the foil - not the hull. The foils nowadays have a little GPS type tracker sender unit inside for locating and retrieval later.
     
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  2. Mr Efficiency
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    Mr Efficiency Senior Member

    What, from sitting on the bottom of the sea ? That would need to be a sound device, wouldn't it ?
     
  3. BMcF
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    BMcF Senior Member

  4. BMcF
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    BMcF Senior Member

    Actually that is correct..the foils are equipped with an acoustic "pinger" that is activated when the cover plated is ripped off a water-contact-activated battery embedded in the foil mounting flange along with the pinger. Then a locater is brought to the area where the foil was lost to find and, hopefully, retrieve the foil.Of course the "MOB" function of the vessel's GPS/Nav system is what marks the spot to start searching...assuming someone on the bridge had the presence of mind to hit the button. ;-)
     
  5. BMcF
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    BMcF Senior Member

    Exactly. And if all goes as designed, you are left with a foundation that is undamaged and ready to accept another foil. Like this one, for example... The stub of the broken actuator shaft is still in place in this pic.
     

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  6. portacruise
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    portacruise Senior Member

    Interesting, BMcF! Something like a compact time or depth activated inflatable float system (like auto inflate life jacket) might make finding a broken off hydrofoil easier, but I'm probably overlooking something? Another way might be a long tether attached to the broken off hydrofoil which is set to pay out behind the boat and is referenced in my previous link. But these may not work for your particular situation....
     
  7. BMcF
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    BMcF Senior Member

    Neither of those would be practical when talking about the abrupt departure of an appendage that can weigh more than a ton that leaves a vessel moving at 40 knots at the moment of separation... ;-)
     
  8. Ad Hoc
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    Ad Hoc Naval Architect

    And if you recall, they worked very well in HK Harbour :D
     
  9. BMcF
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    BMcF Senior Member

    ..yep..and not so well in deep water. We had a foil get knocked off one big catamaran that was too deep to attempt recovery without spending more than the foil cost. ;-)
     
  10. Tiny Turnip
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    Tiny Turnip Senior Member

    What happens to a fully foiling vessel if it loses a foil at speed? are they designed to sit down gently minus one appendage?
     
  11. BMcF
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    BMcF Senior Member

    They behave no differently than an aircraft that suddenly lost a wing. They crash.

    Fortunately, they have a much shorter distance to fall. ;-) There have been incidents where foil collisions resulted in injuries to passengers, unfortunately. But the same is true for other fast craft too...not just hydrofoils.
     
  12. Doug Halsey
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    Doug Halsey Senior Member

    This is a little different kind of hydrofoil, but you get the idea... Broken-Foil Crash 8-26-09 #0049 (Cropped).jpg
     
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  13. BlueBell
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    BlueBell Ahhhhh...

    I remember this photo Doug!
    Love it!
     
  14. Tiny Turnip
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    Tiny Turnip Senior Member

    Thanks Bill, Doug. As you might expect, then.

    Given that foiling has much to offer (speed, smooth ride,) then a workable detection system for floating hazards has got to be a rich prize.

    My understanding is that neither radar, sonar or lidar are as yet effective in waves at picking out floating hazards far enough ahead for a vessel at speed to avoid. And the casualty rate in the Vendee Globes is witness to how much of an issue it is. Is there anything that looks promising?
     
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  15. Doug Halsey
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    Doug Halsey Senior Member

    Me too! It's one of my favorite portraits.
     
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