AC72
The AC72 (America's Cup 72) is a class of high-performance, foiling catamarans designed specifically for the 34th America's Cup in 2013, featuring wing sails up to 40 meters tall and L-shaped daggerboards that enable the boats to lift out of the water on hydrofoils, achieving speeds over 30 knots.[1][2] Governed by a "box rule" that limited dimensions such as length (22 meters), beam (14 meters), displacement (5,700–5,900 kg), and wing sail area (255–260 square meters), the AC72 allowed competing teams significant freedom to innovate in hull shapes, foil configurations, and structural elements while ensuring competitive balance.[2][3] Introduced by Golden Gate Yacht Club (defender) and hosted in San Francisco Bay, the AC72 class marked a shift to larger multihulls following the smaller AC45 one-design boats used for training and the America's Cup World Series from 2011 to 2013.[2] Only four teams ultimately built AC72 yachts due to the class's high development costs and three-year timeline: defending Oracle Team USA (USA 17), Emirates Team New Zealand (Aotearoa), Artemis Racing (Sweden), and Luna Rossa Challenge (Italy).[3] The yachts were launched starting in July 2012, with teams limited to a total of 30 sailing days from July 1, 2012, to January 31, 2013, to maintain fairness.[3] The 2013 regatta was marred by several high-profile incidents that highlighted the AC72's extreme speeds and risks, including Oracle Team USA's capsize during training in October 2012, which damaged their first yacht and delayed their campaign.[4] In May 2013, Artemis Racing's AC72 disintegrated during a practice run, resulting in the death of British Olympian Andrew "Bart" Simpson and injuring two others, prompting safety reviews and structural inquiries under the class rules that lacked specific scantling requirements.[5][6] Oracle Team USA also faced penalties in September 2013, including a two-point deduction and the exclusion of three team members (one sailor and two shore crew), for illegal modifications that added undisclosed weight to their AC45 training boats, though this did not directly affect their AC72.[7] Despite the controversies, the Louis Vuitton Cup challenger series in July–August 2013 saw Emirates Team New Zealand defeat Luna Rossa 9–5 to advance to the America's Cup match against Oracle Team USA, where New Zealand initially led 8–1 before Oracle staged a historic comeback, winning eight straight races to claim the Cup 9–8 on September 25, 2013.[8][9] The AC72's innovative design, pioneered by naval architects like Pete Melvin and Gino Morelli, influenced subsequent America's Cup classes by demonstrating the potential of foiling multihulls, though the class was not reused due to safety concerns and costs exceeding $100 million per team.[3][10]Development and Rules
Origins in America's Cup Evolution
The America's Cup had long been dominated by monohull designs, particularly the International America's Cup Class (IACC) yachts used from 1992 to 2007, which were criticized for their high development costs—often exceeding $100 million per campaign—and limited spectator appeal due to relatively modest speeds of around 12-15 knots.[11] The 32nd America's Cup in Valencia in 2007, defended by Société Nautique de Genève (SNG) aboard Alinghi 5, highlighted these issues, prompting calls for a format that could reduce expenses while increasing excitement and accessibility.[12] This dissatisfaction set the stage for a pivotal shift toward multihulls, influenced by legal proceedings and a desire to revitalize the event's global draw. The transition accelerated through the 2007 Deed of Gift arbitration between the Golden Gate Yacht Club (GGYC), representing BMW Oracle Racing, and SNG, the defender of the 32nd Cup. GGYC challenged SNG's acceptance of an invalid challenger, positioning itself as the legitimate Challenger of Record under the Deed of Gift, the foundational 1852 document governing the competition.[13] The New York Supreme Court ruled in GGYC's favor in December 2007, invalidating SNG's prior protocol and enforcing a Deed of Gift match for the 33rd America's Cup in 2010, which permitted multihull designs within specified length limits (90 feet by 90 feet).[13] This led to the iconic 2010 matchup in Valencia, where GGYC's trimaran USA 17 defeated SNG's catamaran Alinghi 5 in straight-set races, demonstrating multihulls' superior speed—up to 25 knots—and spectacle, while underscoring the format's potential to lower relative costs through innovative design efficiencies.[12] The victory by GGYC, now rebranded as Oracle Team USA under owner Larry Ellison, empowered them as defender to dictate the 34th Cup's parameters. Building on the 2010 multihull success, Oracle Team USA announced the AC72 class on September 13, 2010, in Valencia, introducing 72-foot wing-sailed catamarans as the platform for the 2013 event to prioritize high-speed racing, foiling technology for reduced drag, and enhanced viewer engagement through closer-to-shore courses.[11] The protocol governing the 34th Cup was released on September 9, 2010, outlining the multihull format and establishing the America's Cup Race Management (ACRM) for transparent administration.[14] To bridge the gap and test concepts, the one-design AC45 class—smaller 45-foot catamarans—was introduced in late 2010 for the America's Cup World Series, with the first launches occurring in December and racing commencing in 2011.[15] The AC72 class rule was finalized and published on October 18, 2010, ratifying the box rule specifications that balanced innovation with competitive equity, marking a definitive departure from monohulls in pursuit of faster, more dynamic competitions.[16]Box Rule Specifications
The AC72 class rule, introduced for the 34th America's Cup in 2013, is a box rule that establishes maximum dimensions and parameters for catamaran yachts, promoting design innovation within defined boundaries rather than enforcing a strict one-design format.[17] This approach allows teams flexibility in optimizing aerodynamics and hydrodynamics while ensuring competitive equity through measurable limits on size, weight, and components.[18] Core specifications include an overall length limited to 22.000 meters (approximately 72 feet), a maximum beam of 14.000 meters, and a wing height (serving as the primary sail structure) capped at 40.000 meters.[18] The crew is restricted to a maximum of 11 members, with a total weight range of 957 to 1,012 kilograms (in light shorts), and the yacht's sailing weight range is set at 5,720 to 5,920 kilograms, encompassing hulls, appendages, wing, and equipment but excluding crew.[19][19] Appendage restrictions emphasize simplicity and safety, permitting a maximum of four appendages total—two rudders and two daggerboards (also called bilgeboards)—with rudders limited to 5.000 meters and daggerboards to 7.000 meters in any dimension and no movable components such as trim tabs or winglets.[19][18] Daggerboards must fully retract to no more than 0.500 meters below the main water plane, and no canting keels or similar adjustable ballast systems are allowed, focusing lift generation on fixed or simply rotatable hydrofoils.[19] Protocol elements incorporate one-design requirements for safety gear, including standardized cockpits, tethers, and emergency equipment, which must be approved by the America's Cup Race Management measurement committee.[18] Innovation remains open in areas like wing aerodynamics (limited to 260 square meters area) and hull hydrodynamics, but propulsion is strictly wind- and crew-powered, with no engine assistance permitted except for low-speed docking maneuvers using stored energy sources like batteries for auxiliary pumps.[19]Design Features
Hull and Hydrofoil System
The AC72 class features a twin-hull catamaran design optimized for high-speed performance, with narrow, lightweight hulls constructed primarily from carbon fiber composites to minimize hydrodynamic drag and structural weight. Each hull measures approximately 22 meters in length and the overall beam spans 14 meters, allowing the vessel to slice through waves efficiently while maintaining stability under extreme loads. These dimensions adhere to the class box rule, which imposes strict limits to ensure fair competition among teams.[16][20] Central to the AC72's revolutionary capabilities is its hydrofoil system, comprising L-shaped foils mounted on retractable daggerboards and T-shaped foils on rudders, which generate sufficient lift to elevate the hulls completely out of the water once boat speeds exceed 20 knots. This foiling mode dramatically reduces the wetted surface area, slashing drag and enabling sustained planing at velocities far beyond traditional displacement hull limits, often reaching 40 knots or more in optimal conditions. The main foils on the daggerboards provide primary vertical lift and lateral stability, while rudder foils contribute additional balance and control during flight. Foil shapes varied by team, including straight and curved L configurations for daggerboards.[1][21][22] Foil configurations emphasize fixed, high-aspect-ratio winglets angled upward for inherent stability, with daggerboards limited to a maximum length of 7 meters per the class rule to balance performance and safety. Adjustability is achieved through hydraulic canting of the daggerboards, allowing teams to optimize rake angles for varying wind conditions—vertical for upwind efficiency and raked aft in lighter airs—without active flap mechanisms, as prohibited by regulations to prevent complexity. Both hulls and foils utilize advanced carbon fiber laminates, selected for their superior strength-to-weight ratio, enabling the structures to withstand dynamic loads exceeding 10 tons while keeping total displacement around 5,900 kilograms.[21][18] Structural innovations in the AC72 hull design include wave-piercing bows that minimize pitch and submersion in choppy waters like those of San Francisco Bay, reducing slamming forces during maneuvers. Additionally, the hulls incorporate modular construction with easily replaceable forward and aft sections—each up to 1 meter long—that can be repaired or swapped in under 12 hours, facilitating rapid maintenance between races. These elements underscore the class's focus on durability and hydrodynamic efficiency, drawing on aerospace-inspired composites and computational fluid dynamics for refinement.[1][18]Wing Sail and Rigging
The AC72's rigid wing sail represents a significant advancement in yacht propulsion, functioning as a multi-element airfoil akin to an aircraft wing to generate aerodynamic lift. Constructed primarily from carbon fiber composites, the wing stands up to 40 meters tall from the waterline, with a maximum projected area of 260 square meters as specified in the class rule, though representative implementations provided approximately 240 square meters of sail area for optimized performance.[18] The design typically features two primary airfoil elements separated by a narrow aerodynamic slot, augmented by a smaller trailing-edge trim tab to adjust camber, enabling precise control over the wing's shape and angle of attack through twistable actuators and hydraulic systems.[1] This configuration allows the wing to achieve lift coefficients of up to 2.5, far surpassing traditional soft sails, which typically reach 1.5 to 2.0, thereby facilitating boat speeds exceeding 40 knots in optimal conditions.[22] Integrated rigging eliminates traditional components like halyards and booms, with the carbon fiber structure serving as both mast and sail in a seamless unit mounted on a rotating base near the waterline for full 360-degree adjustment. Control is managed via hydraulic cables and rams—often exceeding 30 in number—linked to a master quadrant at the wing base, powered by manual inputs without stored energy for primary adjustments, per class rules.[23][18] Cyclors, or grindless winches operated by crew pedaling, provide hydraulic pressure for fine-tuning sheets and flaps, ensuring rapid response to wind shifts. De-powering in gusts is accomplished by twisting the upper sections to feather the leech and adjusting camber via flap and slot positioning, effectively reducing lift without altering the overall angle of attack dramatically.[1][22] Crew involvement in sail handling is critical, with four to six members dedicated to wing trimming from platforms on the weather hull, utilizing joysticks, hydraulic levers, and digital displays fed by embedded fiber-optic sensors for real-time data on loads and performance.[23] These sailors monitor instrumentation via personal digital assistants (PDAs) to optimize twist and camber, coordinating with the helmsman to maintain stability during maneuvers, while the remaining crew focuses on foil and hull adjustments. This division underscores the wing's role as the primary power source, demanding constant vigilance to harness its high lift while mitigating risks like structural deflection under load.[1]Competition History
The 34th America's Cup Events
The 34th America's Cup events were hosted in San Francisco Bay, California, spanning July to September 2013, with the Louis Vuitton Cup challenger series running from July 4 to August 30 and the Cup finals occurring from September 7 to 25.[24][25] This venue was selected for its challenging wind conditions, particularly the strong westerlies in the bay, which tested the high-speed capabilities of the AC72 catamarans.[26] The events marked a significant evolution in the competition's structure, incorporating preliminary regattas to build international interest and refine team strategies ahead of the main match.[27] Initially, nine teams expressed interest as challengers, but the field narrowed to three primary competitors—Emirates Team New Zealand, Artemis Racing, and Luna Rossa Challenge—through the Louis Vuitton Cup selection process.[28] The challenger series began with a round-robin stage, where each team raced the others multiple times to establish seeding, followed by semifinals that eliminated one team and advanced the top two to the Louis Vuitton Cup final.[29][24] This multi-stage format ensured a competitive elimination, with Emirates Team New Zealand ultimately winning the right to challenge the defender by defeating Luna Rossa Challenge 7-1 in the final.[30] As the defender, Oracle Team USA, representing the Golden Gate Yacht Club, did not participate in the challenger series but prepared through the America's Cup World Series (ACWS), a series of precursor events from 2011 to 2013 using smaller AC45 catamarans to test foiling concepts and match racing tactics.[31][32] These ACWS regattas, held in various global locations, involved up to nine teams and served as a proving ground for the AC72 class rules and operational logistics.[28] The Cup finals adopted a best-of-17 match racing format, requiring the first team to nine points to win, with a strong emphasis on pre-start maneuvers to gain advantageous positioning in the 13.5-nautical-mile courses around buoys in San Francisco Bay.[31] This structure highlighted the AC72's speed and agility, where tactical decisions in the starting sequence often determined race outcomes, aligning with the Deed of Gift's focus on direct defender-challenger confrontations.[33]Key Races and Team Performances
The 34th America's Cup finals between defender Oracle Team USA and challenger Emirates Team New Zealand unfolded as a best-of-17 series on San Francisco Bay, where New Zealand surged to an 8-1 lead after the first nine races, putting Oracle on the brink of defeat. Oracle, penalized one race point prior to the match for unauthorized hull modifications during pre-regatta testing, effectively started from a 0-1 deficit and needed nine wins to prevail while New Zealand required only eight. The challenger's early dominance stemmed from superior foiling stability and speed, allowing consistent high-performance sailing that averaged over 25 knots across legs, with downwind averages reaching 32-37 knots in optimal conditions. However, Oracle mounted an unprecedented comeback, securing victories in races 9 through 13 through iterative boat upgrades—including rudder T-foil adjustments for better upwind foiling, hull interceptors to reduce drag, and mast rake modifications—that improved their upwind speeds to match or exceed New Zealand's, often by 1-2 knots per leg. These enhancements, combined with sharper pre-start maneuvers led by skipper Jimmy Spithill, enabled Oracle to control key crossings and build leads, such as the 1:24 margin in race 13.[9][7][34][35][36] In the challenger series for the Louis Vuitton Cup, Artemis Racing faced severe setbacks following a fatal capsize during training in May 2013, which destroyed their initial AC72 and delayed their program by months, forcing a rushed second build that compromised performance. The Swedish-flagged team struggled with inconsistent foiling and speed, ultimately swept 4-0 by Italy's Luna Rossa Challenge in the semifinals after a penalty-aided start in the opener. Luna Rossa, meanwhile, advanced past Artemis but faltered against New Zealand in the Louis Vuitton Cup final, losing 1-7 amid tactical mismatches and rule protests earlier in the regatta over safety modifications proposed by event organizers, though they ultimately competed without formal withdrawal. New Zealand's path was marked by flawless execution, dominating the round-robin with a bye to the final, followed by aggressive foiling tactics that exploited the AC72's hydrofoil potential, maintaining leads through precise gybes and tacks at speeds often exceeding 30 knots downwind.[37][38][39][40] Several performance factors influenced outcomes across the regatta, including variable weather that caused multiple delays—light winds below 10 knots postponed races on several days, while gusts exceeding 25 knots halted others, favoring boats with reliable foiling transitions in marginal conditions. The Oracle cheating scandal, involving illegal weight modifications to AC45 wingsail boats in warm-up events, resulted in a $250,000 fine, the suspension of two crew members, and the one-race penalty, intensifying scrutiny on the defender. Crew errors, such as nosedives during high-speed maneuvers, proved costly; New Zealand narrowly avoided a capsize in race 17 after a foil stall, while Oracle experienced a dramatic pitch in the decisive race 19 but recovered without penalty. Notable achievements included New Zealand's record top speed of 47.57 knots in race 18, underscoring the AC72's extreme capabilities, and tactical innovations like boundary plays, where teams used the course's fixed limits to force opponents into unfavorable tacks, as seen in New Zealand's race 11 strategy to "bounce" Oracle and gain leverage on the upwind leg.[41][7][42][43][44]Built Yachts
List of AC72 Catamarans
The AC72 class for the 34th America's Cup resulted in seven completed catamarans that were used for testing or competition by the four participating teams. These yachts were constructed by specialized composite builders under each team's design direction, adhering to the class's box rule. The following catalogs the built yachts, including their identifiers, builders, and construction years.- Emirates Team New Zealand's New Zealand: Built by Cookson Boats in New Zealand and launched on July 21, 2012, this was the team's initial AC72 used as a trial boat for early foiling tests and development sailing in Auckland. It was decommissioned after initial testing.
- Emirates Team New Zealand's Aotearoa: The team's second AC72, built by Cookson Boats in New Zealand and launched on February 3, 2013, incorporated upgrades for the Louis Vuitton Cup and Cup Match.[45]
- Oracle Team USA's USA 17: Built by Core Builders Composites in New Zealand starting in 2011 and launched on August 30, 2012, this served as the defender's initial development platform. It was damaged in a training capsize in October 2012 and repaired, relaunching in February 2013.[46][47]
- Oracle Team USA's USA 17 (second): The team's second AC72, also built by Core Builders Composites and launched on April 23, 2013, featured modified foils and wing for improved performance and was used in the 2013 America's Cup match.[47]
- Artemis Racing's Big Red: Built by King Marine and launched on November 3, 2012, this was the Swedish challenger's first AC72, used for initial testing. It disintegrated in a fatal capsize on May 9, 2013.
- Artemis Racing's Big Blue: The team's second AC72, built by King Marine and launched on July 22, 2013, was used in the Louis Vuitton Cup after the first boat's loss.[48]
- Luna Rossa Challenge's Luna Rossa: Built by Persico Marine in Italy and launched on October 26, 2012, this yacht represented the Italian challenger in the Louis Vuitton Cup, with hulls and foils fabricated using advanced carbon infusion techniques.[49]