35th Americas Cup: Foiling Multihulls!

Discussion in 'Multihulls' started by Doug Lord, Sep 26, 2013.

  1. Skyak
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    Skyak Senior Member

    Good information all.

    About your big moth, did you consider moving the water foil rather than the ballast? Since the foil is in the moving water it is 'powered' and the challenge moves on to control.

    The catamarans or tris and their three point stance will be the strong platforms while control systems develop. But when the multi-hulls max out there will still be less drag and more speed with less hulls or even hull. And I am pretty certain that the future is reverse heel wings. Have you seen any 3D aerodynamics of them?

    The sailrocket demonstrates about every speed trick there is. The only chance I see to go faster is to cut the drag from skimming over the surface -maybe with suspension or ground effects. But then there's the 'boat' issue. My definition of a boat is something that provides some level of maneuverability and protection in reasonable conditions, including no wind. Sailrocket is not a boat because it can only sail on one tack and can't sail in waves that would be typical in the wind it needs.
     
  2. Doug Lord
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    Doug Lord Flight Ready

    ==================
    Several very fast foilers have been designed with dual independent wand or "feeler" systems that allow the foils to generate all the righting moment for the boat up to the structural strength of the boat. This works real well is when the beam of the boat is over-square: the Osprey is 22' wide and 18' long.
    The Hobie Trifoiler and Longshot were examples by Greg Ketterman and the Rave, Skat(40') and the Osprey are examples from Dr. Sam Bradfield. The disadvantage is that doing this causes a lot of drag and in medium and light air affects the ability to sail well upwind in some of the boats. Bradfields 18' Osprey is the only small boat using movable ballast -on the Trifoiler, Longshot and the Rave the crew is stationary in the center. The Osprey is the best performing of Bradfields boats but ,unfortunately his last design.
    I'm not convinced,by any means, that this system would work better than the 3 foil, single mainfoil with a hybrid surface piercing/fully submerged foil coupled with manual angle of incidence control. Especially around a course....

    Pictures, L to R--1)Hobie trifoiler with dual, independent, altitude sensing feelers, 2)Rave,3) Osprey, 4) Skat. 2-4 all use the dual, independent, wands, the modern version of which was pioneered by Dr. Bradfield, and then "borrowed" and refined by John Ilett for the Moth. The Osprey is the only one of the small boats designed to have the crew move side to side which drastically improves performance in light and moderate wind by reducing the load on the foils.
    click for a better view:
     

    Attached Files:

  3. xarax

    xarax Previous Member

    True, but now we have the foils...If both foils are immersed, the heeling force can be controlled and balanced by the angle of attack of the windward foil. The sail itself can be left in its classic pulling/pushing role...
     
  4. RHough
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    RHough Retro Dude

    That would be much slower and more expensive. With a wing the reduction in heeling force also reduces drag. Loading up the windward foil for "dynamic RM" adds to drag. The boats structure would have to be substantially stronger, as if the boat actually had mass equal to the RM generated by the foils. IIRC one of the reasons for the one main foil at a time rule was to prevent loading the structure as you suggest.

    IMO a wing with the top 2/3 trimmed to zero lift is a vastly superior solution to a reefed soft sail.
     
  5. Doug Lord
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    Doug Lord Flight Ready

    2nd Foiling AC

    ====================
    Good point, Randy!
     
  6. Doug Lord
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    Doug Lord Flight Ready

    35th America's Cup: Foiling Catamarans!

    UPDATE 9/30/13: Australias Hamilton Island Yacht Club confirmed as Challenger of Record.
    Bob Oately, owner of the fantastic "Wild Oats XI" ,which has just been fitted with an experimental DSS foil, is behind the challenge. I'ts great to have Australia back in the Cup! I hope we don't lose Jimmy!

    Given Australia’s previous success in the America’s Cup, the Admiral’s Cup and Olympic yachting, and as proud Australians, we think it is time for our nation to be back in our sport’s pinnacle event,” Mr. Oatley said. “The recently completed America’s Cup in San Francisco has revolutionized the sport for sailors and fans, and we were excited to see how many Australians played key roles on the teams and in the regatta organization.”


    http://www.americascup.com/en/news/...-yacht-club-confirmed-as-challenger-of-record
     
  7. oceancruiser

    oceancruiser Previous Member

    monohull 104 ft foiling center

    I would like to see the monohull 104 ft foiling center board as the vessel design as the challenger has this proven winning design and it would keep his costs in check and the only cost would be larry's. No other challengers and the race would be around all hawaii islands with full race time helicopter filming for live tv viewing for all to see, to save the spectactors adding further unnecessary man made global warming emmission as the viewing public probably would in the main be all Kiwis and Aussies as was for the 34 th cup.


    OC
     
  8. RHough
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    RHough Retro Dude

    Going to take 14 feet from one end or from the middle? :)
     
  9. SteveMellet
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    SteveMellet Senior Member

    If we're discussing what we think the next AC should be sailed in, I'd propose that they replace all the lawyers with accountants.

    Specify a maximum spend over the period from today until the next final is complete, set the date, appoint an independent accountant and auditor to each team, and leave the design totally unrestricted.
    Budget cap to include everything except getting the team and boats to the venue, so the defender has no advantage.

    Whichever team brings the smartest design within the budget, wins. You might see the paid rockstar sailors having to take a pay cut to have more money to spend on the boat ! :D
    We might see the French team on a Flying Phantom 18ft foiling cat sail against an American team sailing a 100ft Speeddream style monohull, and it would truly be in the spirit of 'may the fastest yacht win'...
     
  10. Doug Lord
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    Doug Lord Flight Ready

    2nd Foiling AC

    ================
    I like the AC 72's.....
     
  11. P Flados
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    P Flados Senior Member

    Fast cats are likely.

    Fast with the AC 72 was approaching (or may have reached) serious cavitation challenges.

    If you want anything resembling traditional in shore racing, you need the handling that goes with traditional foil sections that do not deal with cavitation well.

    As much as I pulled for "faster is better", future AC will probably be better off trying to limit speeds to stay away from all of the agony of trying to overcome / work around cavitation (as Paul Larson how fun this can be).

    I understand the lure of simpler "box rules" but I also understand that this scares many challengers given the opportunity this provides the best funded teams.

    A lower beam to length ratio makes sense for "safety" where it greatly reduces pitchpole disaster threat.

    Wings vs. soft sails will probably be less of a cost issue as general "state of the art" knowledge base matures. The ETNZ wing was drastically different than that OR design. The fact that both seemed completely capable reduces concerns about choosing an acceptable design. Wings have a much more "high tech" image and not enough of a real penalty to be ruled out at this point.

    Others (at SA) have promoted losing the foresail for cost control. If you take away the foresail, the "skill" required to keep a wing dialed in goes up.

    From the ramblings above, here is a stab at "better":

    • 55 to 65 ft is long enough to be adequately beyond normal
    • Go with a max hull beam at 80% of LOA for "saftey" (to help the general pitchpole threat). This will translate in to less height on the wing
    • Wing only for "cost", but this translates into more skill required therefore transferring more importance from the design process back to the crew.
    • Go ahead and allow "limited crew based stored energy". Set this to be close to the estimate for the output of the grinders for X (1 minute?, 3 minutes?) amount of time.
    • Less rules on foils. Probably allow rudder "stabilizer" foils to extend a foot or so past B Max just in case it helps with the reduced beam.
    • Allow mechanical inputs/feedback into wing/foil/rudder control, but no direct electronic/digital inputs. I do not think anyone is ready for digital controls, but heck we see wand control on a Moth without freaking out.
     
  12. oceancruiser

    oceancruiser Previous Member

    INTERESTING ::: Don't you think.


    In ”hangover” news from the Cup, there are details of the monohull the Kiwis would have proposed if they had won.


    OC
     
  13. Doug Lord
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    Doug Lord Flight Ready

    35th AC-2nd Foiling America's Cup

    Great interview with Russel Coutts about the future. World Series in foiling AC 45's and more. This is going to be exciting!

    http://www.sportspromedia.com/quick...s_losing_the_lawyers_and_the_future_of_the_am

    What’s the future, as you see it, of the America’s Cup World Series?
    "Obviously the foiling boats this time have become part of the brand going forward, part of the image, so we have to address that and recreate that."
     
  14. Doug Lord
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    Doug Lord Flight Ready

    35th Foil Systems

    This is a rough sketch of a concept for a wand controlled "L" foil. However, it might be simpler to allow a rule change that permits a wand controlled t-foil for the single main foil. The windward foil+ wand would be retracted.
    Gives automatic altitude control but to be as good as the current system the wand length would have to be adjustable to allow the boat to fly close to the water or higher up.
    click--
     

    Attached Files:


  15. P Flados
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    P Flados Senior Member

    Doug,

    For an L foil with moving flap, the answer is probably more simple than you think. The hinge line would be straight, and the width of the flap could taper on both ends the eliminate any edge discontinuity drag. You would retain curvature in a rounded transition from vertical to horizontal. The flap would stop before getting to this region.

    The other choice is to have more of bulb at the vertical to horizontal junction.
     
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