Data-Driven Design and Opti­miza­tion of the INEOS Bri­tan­nia AC75

The Amer­i­ca’s Cup is not only a fierce sporting, but also an engi­neer­ing com­pe­ti­tion. Years of devel­op­ment, and the con­cen­trated effort of over 100 team members, cul­mi­nate in approx­i­mately two months of intense match racing. As in the previous install­ment, the current 37th Amer­i­ca’s Cup is sailed with AC75s – high-per­for­mance foiling mono­hulls that are very demand­ing to sail and capable of upwind and downwind speeds of 2.5 and 3.5 times the wind speed, respectively.

Design­ing the hull of an AC75 presents a complex engi­neer­ing chal­lenge, with numerous factors to consider, espe­cially in terms of aero­dy­namic effi­ciency in con­junc­tion with the rig and sail package. Its opti­miza­tion pri­mar­ily focuses on max­i­miz­ing this effi­ciency, while also account­ing for various oper­a­tional modes: take-off, high-speed foiling aero­dy­nam­ics in dif­fer­ent wind speeds and headings, and touch-down hydro­dy­nam­ics, when the hull makes contact with the water while impact­ing waves.

The AC75 class rules impose strict guide­lines that heavily influ­ence hull design, covering para­me­ters like dimen­sions, volume dis­tri­b­u­tion, and hydro­sta­t­ics. While stan­dard­ized com­po­nents like the foil cant system remain fixed, their posi­tion­ing adds geo­met­ric con­straints that design­ers must consider. The hull is subject to tight tol­er­ances, allowing little devi­a­tion. Design­ers must balance these restric­tions, while opti­miz­ing for aero­dy­namic effi­ciency, sta­bil­ity, and hydro­dy­namic resistance.

INEOS Bri­tan­nia tackled the AC75 design chal­lenge using CAESES, along­side expert modeling and CFD know-how from FRIEND­SHIP SYSTEMS, by devel­op­ing a sophis­ti­cated para­met­ric model of the hull capable of explor­ing a wide-ranging design space. This model incor­po­rated all relevant class rule con­straints and pre-pro­cess­ing steps required for CFD sim­u­la­tions. After gen­er­at­ing suf­fi­cient high quality CFD data, machine learning algo­rithms were used to predict forces during take-off, touch-down, and aero­dy­namic effi­ciency in foiling mode, based on flight height and trim in dif­fer­ent wind, waves, and heading conditions.

The sub­se­quent opti­miza­tion process focused on gen­er­at­ing the fastest, rule-com­pli­ant hull shapes for various con­di­tions. This data-driven approach revealed trends in how the optimal hull shape changes in dif­fer­ent sce­nar­ios. Rather than aiming at winning every race, the objec­tive was to design a robust hull that max­i­mized the chances of winning the com­pe­ti­tion, based on the most likely dis­tri­b­u­tion of con­di­tions to be encountered.

A wide range of addi­tional factors, such as foil per­for­mance, cant angle, heel, sail trim, and others, must be metic­u­lously accounted for when pre­dict­ing the time on course for a specific design variant and envi­ron­men­tal con­di­tion. Accurate CFD sim­u­la­tions and com­pre­hen­sive data analysis are essen­tial to iden­ti­fy­ing the optimal winning shape. The exper­tise and in-depth knowl­edge at INEOS Bri­tan­nia are excep­tional, and it was a priv­i­lege to col­lab­o­rate with their team of experts on such a complex and demand­ing project.

Accord­ing to INEOS Bri­tan­ni­a’s chief designer, Dr Martin Fischer, this method of design and opti­miza­tion has been crucial to their devel­op­ment success, as described in his pre­sen­ta­tion at the CAESES User Con­fer­ence 2024. And it has already paid off for INEOS Bri­tan­nia. On October 1, 2024, during Day 5 of the Louis Vuitton Cup Final, Bri­tan­nia set a new speed record for the AC75 class, reaching 55.5 knots (102.8 km/​h or 63.9 mph). Addi­tion­ally, on October 4, they won the Louis Vuitton Cup and are now chal­leng­ing the defend­ing champion – Emirates Team New Zealand – for the 37th Americas Cup.

To get some more details about how INEOS Bri­tan­nia has used CAESES to design their AC75 hull, see Martin Fis­cher’s pre­sen­ta­tion from the CAESES User Conference.

We wish INEOS Bri­tan­nia all the best for their upcoming races as they take on the defend­ers in the America’s Cup!