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Oracle Game Changing Mods

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  • Oracle Game Changing Mods

    Yachting Worlds Matthew Sheahan just published some insight to Oracle Racing's sucess in the later stages of the AC Finals. One of things he did not mention was the
    Supercomputer model crunching which Oracle had access to. Keep in mind Oracle is a leader in the computing business and has virtually endless capacity when running complex model equations. On the other hand, Pete Melvin of ETNZ notes that their processors and computer stations are quite minute in comparison. The team had been sailing their 2nd AC 72 back in February some three months prior to Oracle 2nd boat launch, and were quite content with their learning curve. Oracle had observation boats out eyeballing their training daily and 2 boats to work with, and obviously a much larger facility compared to the small, crowded tents on Piers 30-32. Edge to defender.

    Dean Barker noted today in an exclusive interview with John Cambell NZ'z TV3 News the he knew it was over in the 2nd to last race when ETNZ had done everything right, leading into the bottom mark only to have Oracle leave them in the dust foiling upwind.

    Having remained in San Francisco for a few days after the end of the event, I got to speak to a number of people about what was really going on. It didn't take long for the real picture of what was behind the speed improvements to emerge.

    Oracle's jump in performance half way through the America's Cup is still the subject of hot debate, particularly among the New Zealand press who are convinced that the black cat had some special device that allowed them to foil more effectively. Was the ‘Herbie', as it became nicknamed, legal? Would Team New Zealand take legal action?
    The speculation should have been brought to a halt after team boss Grant Dalton confirmed on Saturday that the team would not be taking legal action over the alleged device. But the chatter still goes on.

    Oracle's two boats were very different in their handling characteristics, indeed so much so that they were nicknamed by the crews, ‘the wife' and ‘the mistress', the latter being boat number one, the more lively, wayward boat. Modified extensively after the big crash in October, the mistress, which was the boat Ben Ainslie helmed during two boat training, was twitchy and difficult to keep under control. (Incidentally, I'm told that Ben's full-on attitude towards helming the mistress often gave her crew the jitters.)

    Boat number two ‘the wife', Spithill's machine, was a far better balanced and dependable machine. This was the boat that went on to be in the Cup, but even then she was a very different boat by the end of the event.
    Here are some of the modifications that took place.
    Rudder T foil modification

    This was one of the biggest performance enhancing changes.
    The T-foils on Oracle's rudders were found to be cavitating at speed which caused drag and reduced the lift of the foil. The bubble was developing at the intersection of the vertical rudder and horizontal foil, towards the after end. To reduce this a filet was added.

    But I'm also hearing that a nose cone type device was also fitted to the forward end of the rudder foil intersection to move the pressure distribution, much like the bulbous bow on a ship.

    While the modifications may have reduced the drag of the rudder, there may well have been an improvement in the trim of the boat too. With more efficient lift at the back, it may have been possible to reduce the angle of attack of the main foils, reducing drag further.

    Hull interceptor
    A vertical plate like device known as an interceptor was fitted to the transoms to modify the flow out from the stern and reduce drag. The system acts like a boot spoiler on a car and is a popular device on boats like Open 60s.

    Asymmetric set up
    I'm told that the boat was set up asymmetrically, possibly with a bit more angle of attack on the starboard daggerboard. This improved the boat's performance on port tack, allowing the crew to put the bows down, go for more speed, pop up onto the foils, increasing speed as the drag reduced and yet still maintain the same true wind angle on port.

    On starboard the boat performed less well, but with the breeze cranked around more to the left, there was more port tack action than starboard.
    When they were sailing downwind on starboard, the boat sailed deeper for the same speed as the foil hauled the boat to leeward making a better VMG downwind. Again with left hand breeze there was more starboard tack than port.

    Mast Rake
    The rig was raked further aft to make the boat point better and improve her balance.
    Wing power lower down
    More power was generated in the wingsail by sailing with a more vertical leech in the lower sections and twisting the op off more.

    The team made plenty of play of this, most likely as it was the most visible change, but the reality was that removing it for breezy days reduced weight and windage. The latter was however particularly important with 50knots over the deck upwind.

    Main foil adjustment
    Contrary to the Kiwi press' speculations, the boat did not have a ‘Stability Augmentation System' (SAS) fitted. I'm led to believe that the team did look into something along these lines early on but ditched the idea.
    Instead, the main foils were adjusted with a mechanical ratchet style device that had fixed settings for a variety of angles of attack. Broadly speaking similar to the way that a bicycles gears are changed with a lever and fixed settings.

    Other differences
    Although not specific alterations, there were other key differences with the main foils. Oracle has much shallower foils, by around 1m and are much less curved than the Kiwis. Presumably one of the advantages here was lower drag from the reduced wetted surface area. A visible clue to this was how Oracle rode lower to the water's surface than the kiwi boat. A less welcome characteristic aboard Oracle when at speed was that the boat would rise up so far that the main foil would run out of lateral support and jump sideways, planting the boat back down on the water. We saw this on a few occasions when she was being pressed hard on the first leg and around the first mark.

    Key game changer
    I'm also told that Oracle's big changes, I think to the rudder, were made on the 16 October, the day that both teams agreed to take off rather than race. In hindsight this could have been one of the Kiwis' big mistakes as they were on a roll at this point having 7 points to Oracle's one. Agreeing to a day off allowed Oracle to engineer their biggest leap in performance as the built the major mod. Although this didn't give them an instant win straight away, it took just one race to tweak the boat after which they won every race from the 19th onwards.
    The Kiwis only won a single race after the 16th.

    " I just found out my nest egg has salmonella" Photo Gallery

  • #2

    Close up of rudder
    " I just found out my nest egg has salmonella" Photo Gallery


    • #3

      Back end July

      Back end race 17 AC Finals
      " I just found out my nest egg has salmonella" Photo Gallery


      • #4
        I'm not seeing this "interceptor" thingy. Is it like a mini sugar scoop? Maybe Matthew Sheahan needs to review the meaning of "vertical" and "horizontal", because I sure don't see anything that looks like a spoiler on a trunk lid.

        My new rudder is going to have concave leading and trailing edges just like Jimmy's! Heck with this elliptical crap. That's so last century.


        • #5
          I'm not seeing it either, nor the filet. But then maybe it's undistinguishable.


          • #6

            It's under the bacon.



            • #7
              OK, I see it in the last boat photo. A little lip at the bottom of the transom, extending the hull profile aft for a couple of inches. Definitely not "vertical"! Unless he meant "vertical relative to the transom, where the transom is deemed horizontal".


              • #8
                Originally posted by Hanno View Post
                OK, I see it in the last boat photo. A little lip at the bottom of the transom, extending the hull profile aft for a couple of inches. Definitely not "vertical"! Unless he meant "vertical relative to the transom, where the transom is deemed horizontal".
                I'm not so sure I see the lip extending past the transom - look at the close up photo in post #2. The transom is pretty flat, and it seems like the photo is during the finals after the mods because Ainslie is on the boat.

                I don't know if my eyes are tricking me, but is a vertical lip visible in the post 2 photo?


                • #9

                  A couple close up of the mods....

                  " I just found out my nest egg has salmonella"

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                  • #10

                    Great piece of info on Asim Khan, the 32 year old from Pakuranga, New Zealand.


                    • #11
                      AC72 Foil Control Secrets

                      AC72 Foil Control Secrets:

                      By Jack Griffin

                      Some people have questioned whether Oracle Team USA had a secret (and illegal) foil control system in their AC72 that helped them defend the America's Cup.

                      OTUSA has released drawings and photos of their system, which used a simple "mechanical feedback" loop to allow precise control of the daggerboard rake. Helmsman Jimmy Spithill had buttons on the wheel to rake the daggerboard fore and aft in precise increments of 0.5° giving him better control over lift for hydrofoiling.

                      OTUSA designers Dimitri Despierres (mechanical systems) and Eduardo Aldaz Carroll (electronic systems) began work in late June 2013 to help the team gybe better. The goal was to reduce distance lost in a gybe from 150 meters to 30 meters. To do this the engineers needed to deal with the problem that board movement varied depending on hydraulic pressure, making it impossible to control lift. What they needed was a way to move the board a fixed amount independent of the pressure and drag load on the board. Within a month, mechanical engineer Alex Davis developed a test bench with a servo control, hydraulic valve and hydraulic ram to simulate movement of the daggerboard box (see photo below).

                      Once the test bed system worked, the system was tested on board. Accuracy was fine, but it reacted too slowly. Mechanical engineer Neil Wilkinson and hydraulics specialist Rolf Engelberts improved the system to improve response speed and make everything more reliable and robust.

                      AC72 daggerboard controls on OTUSA Boat 1

                      The hydraulic ram for rake is not visible in the photo below, but you can see the rams for board cant, as well as the daggerboard cage and daggerboard box. The box moves within the cage, which is fixed in the hull.

                      Rendering of AC72 daggerboard cage below. The cage is fixed in the hull. The daggerboard box moves fore / aft (rake) and side-to-side (cant) within the cage.

                      Controversy and protest by Team New Zealand

                      OTUSA wanted to make sure their system complied with the AC72 Class Rule. They filed a "Public Inquiry" to the Measurement Committee and got approval on 8 August 2013 - only a month before the America's Cup Match was to begin. Team New Zealand then tried to have OTUSA's system ruled illegal but the Measurement Committee stood by their initial decision and the International Jury ruled that New Zealand's protest was made too late, but would not have succeeded even if it had been filed on time. The marked up schematic below was part of Team New Zealand's submission. OTUSA eliminated the spring labeled "Component X" making the TNZ protest moot.

                      " I just found out my nest egg has salmonella"

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