AC Class Articles

TECH FOCUS #4 - 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).

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