The Boats

Groupama Team France AC Class boat

The AC Class in brief


Length: 15 metres
Beam: 8.47 metres
Maximum draught: 2.40 metres
Wing height: 23.60 metres
Surface area of wing: 100m2
Weight of the wing: 445kg
Weight of the platform: minimum 1,887kg – maximum 1,987kg
Total weight: minimum 2,332kg – maximum 2,432kg
Weight of media and safety equipment required by the organisation: 149kg
Crew maximum weight :525 kg for 6 crew members
12 headsails
2 T-foil rudders
4 foils permitted
Able to sail in wind of between 5 and 25 knots
Upwind flight in upward of 10 knots and downwind flight in upward of 8 knots of breeze
Peak speed 45 knots

The AC Class rules

Exit the leggy 22-metre spiders, which dominated the race zone in San Francisco in 2013. Farewell to the AC62, which had been hinted at for a while. Make way for the AC Class… On 1 April 2015, it was decided that the 35th edition of the America’s Cup would be held on catamarans with a fixed wing, measuring some fifteen metres or so in length, which is a lot smaller than those from the 2013 edition, as well as being quicker thanks to the use of foils that transform the multihulls into fighter planes. Given the progress made in the design of the appendages, the speeds are virtually identical.

Certain elements of the boat are common to all the competitors, while others can be developed.


The framework provided by the official America’s Cup Class (AC Class) measurement

  • The AC Class must measure 15 metres.
  • The maximum permitted beam equates to 8.48 metres.
  • The maximum water draught is 2.40 metres. 
  • The wing must measure 23.60 metres high from the mast foot.
  • The shape of the hull below the waterline, the sail width and surface area, the cockpits and the Pod on which the wing sits, are all one-design.
  • The structure of the wing, the appendages (rudders and foils), the electronic and hydraulic control systems and the fairings are free of regulations.


- white : one-design parts
- red : one-design in shape but free of regulations in structure
- blue : free of regulations parts


Using this framework, Groupama Team France’s engineers, split into different sectors, each worked on optimising the boat’s performance within the limits of the regulations.

La jauge des Class AC

The wing

The wing of the Test AC Class comprises 3 sections:

1 • the one-design mast which is seated on a ball joint measuring 60 millimetres in diameter on the platform.

2 • the forward section, flap 1

3 • the aft section (flap 2), which is itself made up of three flaps

The forward section of the wing, of which a large part is one-design and constrained by the measurement rules, has been part built at Core Builder Composites in New Zealand, which has already made the wings for Oracle Team USA and SoftBank Team Japan. However, Groupama Team France has put a lot of work into the lower section of this flap 1, which houses the wing control systems.

Eloi Stichelbaut/GroupamaTeamFrance


The utmost care has gone into the three aft flaps, which can be twisted. Their structure is created using numerous carbon ribs whose position is governed according to aerodynamic criteria.

In fact, the implementation of TPT technology (Thin Ply Technology) enabled Groupama Team France’s Design Team to optimise the weight and direction of the carbon ply during the lay-up of the wing’s aft flaps. Ultimately, a little weight has been saved on each of the flaps.

These ribs are then wrapped in the same film used in agrifoodstuffs, which is an easy material to stretch and make rigid.

Eloi Stichelbaut/GroupamaTeamFrance


The wing control system

Between flap 1 and flap 2, hinges are positioned to adjust the different elements. To rotate each joint, we use a quadrant. The upper section of the wing being fixed, the challenge is to be able to twist and bend the flaps by angling them differently if necessary, and this has to be done quickly as the legs are short in a race! 

With the parts manufactured at the CDK yard and GUELT responsible for the mechanics, the system must be easy to use and be readily adapted to adhere to the constraints.

There are two possible parameters: the camber and the twist.

  • The camber: When there is no or little wind, you increase the angle to give the wing shape. When it’s windy, you seek to flatten the wing.
  • The twist: you perform this motion when you do not wish to have the same level of force in every part of the wing. At the top of the latter in particular, the flap can work ‘in reverse’, contrary to a classic sail, so as to improve the wing’s performance.

Subtitles can be activated in the video - L'aile rigide du Class AC Groupama Team France | Franck Cammas


Concevoir l'aile du Class AC - par Gwénolé Bernard

The aerodynamics

The aerodynamics of the AC Class is split two ways: 

  • Aerodynamics of the wing
  • Aerodynamics of the platform (or windage)

Aerodynamics of the wing

The team is working on three main areas:

  • Calculation of the loads

This element focuses on the study of the loads on the wing, rig and sails. As such the engineers simulate the whole of the wing and sails using fluid structure interaction (“aero-elastic coupling”). The latter enables a balance to be struck between the aerodynamic forces and the structure of the wing/sails. It indicates the internal stresses that the wing will have to withstand, as well as the loads on the shrouds, control line, sheets, etc. These loads are used for the rigging, as well as to proportion the hydraulics.

In this section, we can assess the form the wing will have once there’s wind on it. Various sailing conditions have to be envisaged to ensure optimum distortion in different wind strengths, as well as making sure that it doesn’t break!

  • CFD studies

Julien Pilate uses CFD software (panel code and RANS) in order to simulate the wind around the boat. It illustrates the stresses (Forces/Moments). In this way, the team can explore different types of trim for the wing and sail configurations.

  • North VPP

This prediction tool enables the optimum shapes to be determined, which were previously calculated using CFD. It’s a key process in the design phase and it is geared at quantifying the impact of different trims in relation to the boat’s performance. Once the boat is launched, this tool will also be able to answer the sailors’ questions, as well as optimise the Test AC Class and then the AC Class.

Aerodynamics of the platform (windage)

Studies into windage involved studying the fairings so as to reduce the boat’s drag.

It’s Juan Kouyoumdjian’s team which is working on this subject. The members of Groupama Team France are providing VPP input, a prediction tool designed to quantify the performance of the various platform candidates.

Eloi Stichelbaut / GroupamaTeamFrance

The appendages

The appendages press onto the water and enable the boat to lift up as the speed increases. There are two types:

  • The adjustable, retractable L-shaped foils aft of the forward beam.
  • The T-foil rudders, which are also adjustable and positioned on the aft section of the hulls.

Les foils de l'AC 45 Series

Exemple d'un safran en T (AC 45 Series)


Focus on the fully carbon foils:

The foils are made up of two elements

  • The upper section of the appendage called the SHAFT
  • The lower section is called the TIP.
  • The junction between the two is called the elbow or knee.

The class rule imposes a maximum number of Shafts and Tips

  • On the training boat, the team can build 6 Shafts and 12 Tips
  • On the AC Class, just 4 Shafts and 8 Tips are permitted.

The lower section, the Tip, must not represent more than 30% of the foil weight, but its length is not restricted.


Groupama Team France, like its rivals, is adapting the foils according to the wind ranges and is building two types:

  • Foils for light to medium airs, whose Tip is longer
  • Foils with a shorter Tip, optimised for higher speeds

Martin Fischer“The rule does not require the boat to be configured symmetrically when racing. As a result, our port and starboard foils can be different. This is an interesting element, because when you run the race simulations, you notice that the course is not symmetrical. There’s more emphasis on starboard tack than port tack. There are two high-speed reaching legs on starboard tack.”

With the notable use of ESTECO software, the members of Groupama Team France are optimising the foil shapes by integrating the design parameters so as to optimise the boat’s performance for different operating ranges.

© Eloi Stichelbaut / Groupama Team France

Le foil sous le vent est en position basse (descendu), le foil au vent est en position haute (relevé).

The foil control system

Eloi Stichelbaut / GroupamaTeamFrance
Eloi Stichelbaut / GroupamaTeamFrance

This system enables the foil movements to be controlled and fixed.

Three types of motion are identified:

  • Longitudinal = rake
  • Sideways = cant
  • Vertical extension = up and down

Stéphane Chatel: “The sailors are engines when it comes to putting the foils in motion. To prevent then wasting energy unnecessarily, we have to avoid friction as much as possible. We must ensure the fluidity of the water flow around the foils, by assessing such things as the choice of materials permitting a smooth passage. Three rams enable the foil to be operated and adjusted as the crew wishes, within a lower limit of 2.40 metres.”

The helmsman deals with 27 action buttons to trim the foils and adjust the flight of the Class AC.

Eloi Stichelbaut / GroupamaTeamFrance

Subtitles can be activated in the video - Les controles à la barre du Class AC | Franck Cammas

Title Sponsor

Official Partner

Exclusive Suppliers

Official Suppliers

  • 1198
  • 1197
  • Engineers from the French team will leverage ESTECO’s first-class optimization technology to maximize the hydrodynamic and aerodynamic performance of their catamarans.

    ESTECO SpA, a leading provider of numerical optimization solutions, provides Groupama Team France its best-in-class software to perfect the design of Team France’s high-performance foiling catamaran design.

    As design specifications get tighter and time for physical testing becomes shorter, engineering technology is increasingly crucial in the race for the America’s Cup.

    ESTECO technology, also used by the Luna Rossa team in the past and by Ben Anslie Racing team in the current edition of the America’s Cup, helps designers make the most out of their simulation data and perform advanced optimization processes in order to refine design parameters.

  • 1185
  • 1188
  • Groupama Team France is using the “Designed for Sea” industry solution experience provided by Dassault Systèmes, the 3DEXPERIENCE Company, world leader in 3D design software, 3D Digital Mock Up and Product Lifecycle Management (PLM) solutions, to design and simulate a lightweight, high-performing racing catamaran that complies with the competition’s design and schedule requirements.

    In preparation for its first America’s Cup race on May 26, 2017, Groupama Team France needed to design, build and test its catamaran within 18 months. Boats for the challenge must adhere to specific protocols concerning the hull, the wings and the transverse structures as well as the quantity of materials used. The length of a team’s catamaran is restricted to 15 meters and it could not be tested in water until December 26, 2016.

    Based on Dassault Systèmes’ 3DEXPERIENCE platform, “Designed for Sea” industry solution experience enables Groupama Team France to virtually design, simulate and optimize its catamaran’s weight, performance, stability, strength and safety in a collaborative digital environment, before any construction begins. Since October 2015, Groupama Team France has had a single source of data and fully integrated applications to streamline and accelerate the boat’s development as well as the flow of information between the 30-person design team, the crew and external partners participating in the design effort.

  • 1853
  • 2243
  • The EXAGONE company specialises in the development, operation and commercial management of a satellite positioning system network synonymous with centimetre-precision, the TERIA Network.


    Heir to technical and scientific knowledge, the EXAGONE company is born from a desire to become a reference in this domain on the part of the French Council of the Order of Licensed Land Surveyors in partnership with the National Geographic Institute. Together with skills and modernity, it brings to the fore innovative, sustainable solutions to the various economic, technological and environmental challenges.


    Armed with its expertise, EXAGONE provides its clientele with permanent, accurate, high performance services of impeccable quality. EXAGONE is involved in a wealth of different projects including measurement, monitoring of the various glacial sites (Mont Blanc, the Arcouzan glacier and Barre des Ecrins…), and the tracking of whale sharks in partnership with the Megaptera Association.


Club Team France

Supplier and Providers

Official Supports

Challenger Yacht Club