Cup Experience

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Less Stability Means More Speed

Ian “Fresh” Burns of Oracle Team USA explains in this Sail Racing Magazine interview how the team trades off stability for speed with their foil design.

Foils with less drag are less stable. Improvements in the control systems can partially overcome this. As the sailors learn how best to handle the boat, they are happy to make the tradeoff to get more speed.

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“A big challenge is how to project/predict where your sailing crew’s abilities are going to be by the Cup. You have to be saying to yourself, well our guys can control this level of stability now, but in a year’s time they will probably be better and able to handle a less stable boat. So you have to be working on a final foil design that is something that, if we built it right now, the guys probably wouldn’t be able to sail.”

Read the full interview here.

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Team Lineups for Toulon – Spithill not Racing

It looks like my report two weeks ago about Jimmy Spithill re-injuring his recently operated elbow was correct – he is not in the lineup; Tom Slingsby will be on the helm. Olympic sailors have rejoined their teams and will be in Toulon. Peter Burling and Nathan Outteridge will be back helming Team New Zealand and Artemis, respectively. Giles Scott is in the team list for Land Rover BAR. Teams are allowed to name 11 sailors and shore crew for each AC World Series. Here are the lists for Toulon. For Artemis we can assume that the last five names are the sailing crew; all the other teams list their sailors first.

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Groupama Team France Happy with Testing

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Team France christened their AC45X test boat on July 11 and began sailing two weeks later. They were happy to be foiling on their first day of sailing and happy that the boat performed very close to the predictions from their simulation programs. The performance numbers from the VPP (velocity prediction program) are based on the full aerodynamic optimisation of the final race boat, which is different from this test boat. Head of design Martin Fischer notes that this boat is about 90% of the race boat – everything except the hulls will be used in the race boat – wing, foils, rudders, crossbeams and longitudinal pod.

In the photos, notice the bulbous bow shape and the splash rail on the bow, just under “Groupama.” Neither is allowed on the race boat, but they add stability to the four foot shorter test boat. Note, too, the aft fairing that extends beyond the stern of the hulls. This will be flush with the stern of the race boat’s hulls.

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Team France AC45X test boat, bow on. It looks like they are testing straight daggerboards with dihedral (upward sloped) winglets. You can clearly see the spray rails on the bows.

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Video: Oracle’s Foiling Tack

One day after Team Japan released their foiling tack video, Oracle followed suit, saying that they, too, had done a foiling tack in April, a few days after Team Japan. They claim that they have now done foiling tacks in “full manual mode” – with their electric pumps switched off. Click the image or here to watch Oracle’s video.

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Video: Foiling Tacks by SoftBank Team Japan

Back in April, SoftBank Team Japan pulled off their first foiling tack in their AC45X test boat. Last week they released a video and a news article. A day later, Oracle Team USA reported that they, too have done foiling tacks, including in complete “manual mode” meaning without electric motors pumping hydraulic oil to operate the daggerboards. Here are the videos and a detailed look at Team Japan’s choreography. To describe the action, we’ll number the crew positions 1 to 6, starting in the bow.

At 12 seconds into the video, we hear helmsman Dean Barker call, “Standing by” to start the manoeuvre. Wing trimmer Chris Draper hands Barker the wing trim line and crosses to the port hull to set up the wing trim line on that side and to steer while Barker crosses over later. The number 1 man crosses with Draper.

At 19 seconds into the video, the number 3 man leaves his cockpit to tack the wing using an inverter line. He then crosses to the port hull. Remember that in 2013, Team New Zealand almost capsized their AC72 in Race 8 when their hydraulically controlled wing did not tack. Oracle had an inverter line to tack their AC72 wing manually, and their AC Class design, used by Team Japan, also has a manual inverter line for the wing.

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As they complete the tack, Barker crosses over after the number 4 man. While Barker crosses, Draper is steering from the wing trimmer position, and trimming the wing. At the end of the manoeuvre, the number 2 man is still in his cockpit in the starboard hull.

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When you play the video, listen to the high pitched whine of the electric pumps for the hydraulics.The louder, groaning sound is the wing trim line as the trimmer lets it slip on the winch drum. The AC Class boats that will race next year must only use manual power – no electric pumps permitted.

Click here or any of the photos to watch the Team Japan video.