AC 36 Foiling Monohulls

Discussion in 'Sailboats' started by OzFred, Sep 13, 2017.

  1. Earl Boebert
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    Earl Boebert Senior Member

    I revisited the video and it seems to me that the narrator was quite clear that the battery drove what I would call a shuttle pump that moves fluids from one place to another, and does not charge the accumulators -- that is done (I think) by scavenging the energy from the lifted foil by letting it drop, and using the "pre charge" pressure tank to make up for any loss. So it is the capacity of the "pre charge" tank which is the limiting factor. I would love to see a schematic of the gizmo but that will probably never happen.

    Cheers,

    Earl
     
  2. Doug Lord
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    Doug Lord Flight Ready

    Might happen , Earl-one good thing is that this tech is not secret and is being shared by all Challengers and the Defender....
     
  3. OzFred
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    OzFred Senior Member

    I think we're talking at cross purposes. I didn't say or infer anywhere that the foils are electrically actuated and yes it's clear from the video that hydraulic pumps and rams are used. Batteries are only involved in that they drive the "top–up" pump (perhaps augmented by human power). I don't think battery capacity will be a limiting factor for AC racing and haven't said it is.

    I presume that when you say "it is the capacity of the "pre charge" tank which is the limiting factor" you're referring to the speed of raising the arm, which I agree has nothing to do with the batteries and I wasn't referring to them in that context.

    I did say that in the context of a long sea voyage, batteries (for the top–up pump and other energy consuming devices) will need to be augmented or replaced with another energy source. E.g. large racing yachts use diesel engines as an energy source to pump water for ballast and cant their keels.

    Oh, I also found:

    22.13 Energy may only be stored within HCCs:
    (a) by one high-pressure accumulator per yacht with a maximum capacity (gas plus hydraulic fluid) of 2.0 litres;

    Where "HCC" is hydraulic control circuit. So only one accumulator for the foils and they'll have to wait the full cycle time after raisng a foil.
     
  4. Dolfiman
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    Dolfiman Senior Member

  5. Earl Boebert
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    Earl Boebert Senior Member

    OK, I understand now, thanks. Sometimes it takes a while :)

    Cheers,

    Earl
     
  6. Doug Lord
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  7. OzFred
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    OzFred Senior Member

    No problem. I now have an answer on the multiple high–pressure accumulator question. :)
     
  8. Doug Lord
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    Doug Lord Flight Ready

  9. Earl Boebert
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    Earl Boebert Senior Member

  10. Doug Lord
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    Doug Lord Flight Ready

    It's getting more interesting by the minute.....
     
  11. Doug Lord
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    Doug Lord Flight Ready

  12. Doug Lord
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    Doug Lord Flight Ready

    From Jack Griffins "Cup Experience":
    There is also some very poor quality video in this issue showing an INEOS capsize where she appears to spinout then capsize......no way to up load the issue or video so far.

    Foil Cant System Update - Foil Arms
    The Foil Cant System (FCS), including the foil arms and the hydraulic system to raise and lower the foils will be supplied equipment. Each team will design and build their own foil wings, flaps and the systems to control the flaps. The supplied foil arms are complex composite structures that must withstand loads in multiple directions. This is a difficult structural design task. Early designs failed in load tests. Structural specialists from other teams have now joined Luna Rossa's designers to find a solution. This group seems to be confident that they now have a solid design. Sample foil arms will be built and tested to destruction. Production foil arms and the FCS should be delivered to the teams within a few months. The schedule delay could impact the dates of the first America's Cup World Series, currently planned for October in Cagliari.
     
  13. Doug Lord
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    Doug Lord Flight Ready

  14. Earl Boebert
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    Earl Boebert Senior Member

    A different foiling monohull question: can somebody explain to me the sequence of arm movements that gets one from displacement mode to foiling mode. My knowledge of these matters is limited, and I can't for the life of me visualize how they get from two arms down to one up/one down on a beat or reach while still maintaining adequate righting moment.

    Cheers,

    Earl
     

  15. Doug Lord
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    Doug Lord Flight Ready

    Seems to me that two arms fully down is their "docking" mode. I would think as they approach an area where they want to foil they would raise both arms to their foiling positions in a sort of "takeoff mode" ,then as the boat begins to fly they would raise the windward foil completely*. This way they would have max foil lift for takeoff .
    They may use both foils down for certain conditions and for tacking and gybing.
    *It's probable that they would set the flaps down for takeoff and raise the windward flap to neutral before raising the windward arm. As far as I remember it is not legal to use the windward foil for downforce but I wouldn't be surprised if that changed -at least for a few seconds after a tack or gybe.....
     
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