AC 36 Foiling Monohulls

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

  1. Doug Lord
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    Doug Lord Flight Ready

  2. Konstanty
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    Konstanty Junior Member

    There will be a little more wave or wind and the races will be canceled again.
     
  3. Doug Lord
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    Doug Lord Flight Ready

  4. Doug Lord
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    Doug Lord Flight Ready

  5. OzFred
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    OzFred Senior Member

    Doug, can you please stop calling the AC75 boat "NZAC"? That is your name for your design, it's not relevant when discussing the actual boat that will be used for AC36.
     
  6. OzFred
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    OzFred Senior Member

    A few more articles on the AC75 boat:

    America's Cup - Dan Bernasconi explains the foiling AC75—Part 1
    (http://www.sail-world.com/USA/Ameri...oni-explains-the-foiling-AC75---part-1/158994)

    Some quick points:
    • Foiling in 9kns of breeze
    • Foil tacks and gybes
    • Foils will weigh 1 to 1.5 tonnes
    • As fast as an AC50
    • Downforce from windward foil possible but more advantage it flying it for righting moment
    • Foiling in waves
    • Conventional rig with code 0
    • Foils and rig much further aft than AC50 so safer in nosedive

    America’s Cup – Franck Cammas : « L’AC75, un hybride entre un multicoque et un monocoque »
    (America’s Cup – Franck Cammas : « L’AC75, un hybride entre un multicoque et un monocoque » http://voileactu.blog.lemonde.fr/2017/11/21/americas-cup-les-neo-zed-devoilent-leur-ac75/)
    In French, but if you use Chrome it will offer to translate it for you, or use this link to Google translate into whatever language suits.

    I'd like to provide a précis of the content, but I don't have time.
     
  7. schakel
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    schakel environmental project Msc

    So we can expect a smooth race.
    About men falling of into foils.
    The foils are situated in front of where the crew operates so little chance to that.
    [​IMG]
    Is any thing said about the wing?
    Will it be 3 parts segmented?
    Double sails with ingenious profile adjustment in between?
     
    Last edited: Nov 23, 2017
  8. CT249
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    CT249 Senior Member

    Interesting. Frank Bethwaite reckoned that 9 knots was the average peak windstrength in most popular sailing areas. That means that if all predictions are true, even the most advanced foiling yachts won't normally be able to foil on a normal day in a normal sailing area.

    I'd rather they brought back the cats, and I didn't think I'd say that.
     
  9. TANSL
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    TANSL Senior Member

    I suppose that when speaking of 9 knots, or any other number, they refer to the apparent speed of the wind. That speed can be reached with lower values of the real wind speed. Is this correct?
     
  10. Doug Lord
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    Doug Lord Flight Ready

    ===================
    NZAC stands for New Zealand AC boat which makes it completely relevant to this thread.
    ---------------------------------
    Foiling in 9 knots of breeze seems like a step backwards- some foilers are designed to foil in 5-6 knots and upwind in 7-8. For production boats foiling throughout the windrange is important-for NZAC it may be important to some Teams.
     
  11. Dolfiman
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    Dolfiman Senior Member

    Here is a proposed translation of this Frank Cammas interview :

    Introduction :
    "On its foils, the AC75 has the potential to be faster than an AC50 [the multihull of the last Cup]," said Grant Dalton, the boss of the New Zealand team. "Not sure," answers Franck Cammas.

    Q : What is your hot analysis of this boat that Team Zealand presented to us ?
    A : "It is a very innovative concept. There is currently no boat of this type that exists with this way of sailing. To fly monohulls is absolutely not evident but to have removed the keel should allow it more easily."

    Q : Do you think the AC75 is as easily achievable as this little movie suggests ?
    A : "These are boats based on numerical models and predictions. Presently, there is still no model that flies on this principle. Hopefully it works like the little movie shows. What is certain is that it will be extremely complex to draw. It's a real challenge to design a boat that flies with such stability. A challenge also to make it sail because there are two big foils ballasted to provide the righting moment in the phases of transition. Well, you have to move them like a classic canting keel, but there are two of them ... That means that it takes a lot of energy to get them up and down, and to rotate them from one side to the other. An equation difficult to solve."

    Q : There are still many unknowns
    A : Even for New Zealanders. They released the concept but the rule is not out yet. It is scheduled for March 2018. By then, they will have had time to do further calculations with real life simulations, perhaps with models.

    Q : Is not this model the marriage "between carp and rabbit" (Translation note : french wording meaning marriage against nature) , between the monohull and the multihull?
    A : It is clear that the New Zealanders have tried to satisfy the demand of the Italians to return to monohulls while keeping this innovative spirit of the Cup. From what we see, they tried to make a monohull that could fly on the same physical principle of the old flying multihulls. That's why they put such foils outside the hull as points of support, and to dose this power when it accelerates. On the other hand, as long as the boat is not at full speed, contrary to multis who have floats to support when they cannot fly, this monohull has nothing or little means to rely on archimedian buoyancy. A priori, in the example they give, to overcome this phase of acceleration on this machine that has no RM at low speed, they move and ballast the windward foil which gives it enough RM to overcome this transition phase before the leeward foil can do its job and makes the boat fly. I think this phase is quite difficult to conceive. It will depend on the weight of the foils. This data will be in the rules.

    Q : It will also be a challenge for crews?
    A : It will be necessary to see how they will maneuver all that. We still feel that it is a boat that will be very penalized in the starting and maneuvering phases if everything does not unfold perfectly as the short film shows. And in addition the race starts will be upwind so without speed.

    Q : It was important to publish this movie now ?
    A : Yes, now the world of the Cup knows what to think by March. Of course the Italians and New Zealanders already know where to go but the other teams will not be speeded up. For the moment, it's an engineer concept, no a sailors one because they have never sailed on such a boat.

    Q : ETNZ takes a lot of risks in opting for such an innovation.
    A : Yes, they go to the unknown. It's very exciting because no one knows this kind of completely innovative boat. On the other hand, it is possible that the regatta will not go as ewpected because these boats will not be able to sail in match-racing that the Cup requires, which was reproached for the multihulls. That said, we have seen in the history of the Cup that the teams were able to meet these kinds of technical challenges. Now we know that these boats will be slower than AC50s.

    Q : That's not what Grant Dalton says.
    A: I do not know how he can say that. With numbers alone, we know it's impossible. When we take three data: weight, RM and drag, we know that this AC75 is over the AC50. So we know that the AC75 will be slower.

    Q : If you had to give him a note ?
    A : (laughs) Artistic note ? Frankly the little movie is cute ! Technical note? In the spirit, the concept is interesting. It is rather good that with this monohull specification, they could do something that is so different, innovative and so fast. It is clearly an hybrid between a multihull and a monohull. Italians can be happy because it's still a monohull by definition, even if it has lost its keel and has two appendages that bring it closer to a multi than a monohull.
     
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  12. PNW sailor
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    PNW sailor New Member

    No Doug,
    the proper name for the N.Z. boat and team is
    "Emirates Team New Zealand."
    The proper name for the Class is "AC 75"
    The Race is "America's Cup 36"


    Please stop trying to rename these in your own image.
     
  13. Doug Lord
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    Doug Lord Flight Ready

    =======================
    Sorry, I came up with NZAC to refer to the newest* New Zealand Americas Cup boat.
    Ridiculous!!!
    *inspired by TANSL
     
    Last edited: Nov 23, 2017
  14. TANSL
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    TANSL Senior Member

    Which boat of all those who have competed in the America's Cup.
    It is not good that each one puts a name chosen by him to each thing. In the same way that the "uptip foil" should not be called "L foil", the type of ship in each edition of the America's Cup has its own name. Let's be consistent with what we preach.
     

  15. CT249
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    CT249 Senior Member

    I wouldn't think so, because that's too circular a definition, particularly given the speed at which the apparent may increase once the boat gets onto the foils. It wouldn't tell anyone whether the boat was doing 8.5 knots in one knot of true wind, or 1.5 knots in 8 knots of true wind.
     
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