America’s Cup Boat for 2021 Revealed By Steve Morrell Animated images © Virtual Eye
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n November, Emirates Team New Zealand (ETNZ) and Luna Rossa design teams revealed the new monohull that will be raced in the 2021 America’s Cup—the AC75 foiling monohull—and it will rock the world of sailboat racing, just as many of the America’s Cup boats have been doing in the last three decades. The design teams suggest that this concept “could become the future of racing and even cruising monohulls beyond the America’s Cup.” The AC75 will have twin canting T-foils, one on each side of the boat, that are “ballasted to provide righting-moment when sailing, and roll stability at low speed.” They claim the boat can right itself if it capsizes. Its normal sailing mode will have the leeward foil lowered into the water and the windward one raised out of the water. Both foils can be lowered into the water to increase stability—and lowered completely under the boat for even greater stability and to enable the boat to fit in a standard berth. The AC75 will not have the wing sails that have been so popular in recent Cup boats, but will have conventional “Code Zero” sails, which is a relatively new category of sails that are still under development, although their broad and evolving definition includes sails that were introduced more than two decades ago. The name means different things to different people. The North Sails website defines Code Zero sails: Code Zeros are free flying, designed for close reaching angles, generally used between 40-90 degrees apparent wind angles and true wind speeds under 20 knots. To understand the different names and different
News & Views for Southern Sailors
Animated drawing of the AC75 foiling monohull under sail (normal sailing mode configuration).
versions of these sails, it helps to look back at their origin. Originally Code Zeros were designed to qualify as spinnakers under various rating rules, which require the midgirth to be 75% of the foot length. Multihull sailors called these sails screechers, while Volvo Ocean Racers coined the term Code Zero. The greatest benefit of the Code Zero is adding a great deal of sail area and efficient sail power to underpowered, close reaching angles.
The ETNZ and Luna Rossa teams have been studying a new monohull concept for four months and one of their main principles has been to establish technology that can, in their words, “trickle down” to other sailing classes and yachts. This concept does not stop with hull designs but with the rigs also. They have not developed the final rigs for the AC75, but are hoping to have rigs that do not have to be craned in and out every day. Released were design drawings, including animations of the Normal sailing mode. Leeward foil provides lift. boats under sail, even with aniWindward foil provides righting-moment. mated sailors operating coffee grinders, which will be necessary to operate the hydraulic systems for raising and lowering the Tfoils. The videos and drawings can be viewed at americascup.com. They believe that the boats have the potential—when up on their foils—“to sail faster than an AC50 both upwind and downwind.” It will definitely be a major change in the future America’s Cup—probably as great as the switch to the foiling catamarans was back in 2013. The 2021 Cup races will he held in Auckland, New Zealand, Stable sailing mode. Maximum stability in manoeuvres but pre-Cup racing of the AC75 and difficult conditions. should start in 2020.
SOUTHWINDS
January 2018
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