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AC75 and Modern Foiling Technology
The AC75 marks a turning point in the history of the America's Cup: for the first time, monohulls in the world's premier sailing competition are permanently foiling – at speeds that put previous Cup generations and even the AC50 catamarans in the shade. The 75-foot yachts combine the tradition of the single-hull boat with the radicalism of modern foiling technology and have redefined professional sailing technologically, tactically and in the media.
What Is the AC75 Class?
The AC75 (America's Cup 75) is a one-design racing class developed specifically for the 36th America's Cup (2021 in Auckland) and the 37th edition (2024 in Barcelona). Unlike earlier Cup generations with catamarans (AC45, AC50), the class returns to the monohull – albeit one that only touches the water at selected points.
Key Data at a Glance
The class was designed as a compromise: spectacular for TV, technologically demanding, and with safety and cost controls.
AC75 vs. AC50 vs. Classic Monohulls
The AC75 strikes the golden mean: faster than IACC monohulls, slower than AC50 catamarans, but visually unique through the monohull silhouette in flight.
The Revolution: Foiling with a Single Hull
Why Monohull and Not Catamaran?
After the AC50 catamarans at Bermuda 2017, the Cup opted for a foiling monohull – for three reasons: classic silhouette at foiling speed, higher technical challenge than the catamaran, and tactical closeness in match racing even at high speeds.
Canting T-Foils: The Heart of the AC75
The canting T-foils are the technological heart of the AC75. Unlike fixed foils, the lifting wings can be swung out sideways from the hull:
- The windward foil is typically retracted or minimised to reduce drag.
- The leeward foil carries most of the lift and stabilises the boat in flight.
- The canting angle is adjusted hydraulically – one of the most demanding tasks for the crew and the flight control system.
The foils are made of high-strength carbon and operate under enormous loads. Even minor damage to the edge or profile can massively impair lift – which is why foil maintenance is part of every syndicate's daily routine.
Foil Control During Racing
- Wind analysis – assess conditions and set foil strategy
- Foil selection – which foil active, which minimised
- Set canting angle – hydraulic adjustment for lift
- Stabilise flight control – maintain height and roll in flight
- Manoeuvres (tack/gybe) – coordinate foil and sail changes
- Recalibration after manoeuvre – restore stable flight
Soft Wing and Sail Technology
Twin-Skin Mainsail
The AC75 mainsail is neither a classic fabric sail nor a rigid wingsail like on earlier catamarans. Instead, the class uses a twin-skin mainsail – two sail layers forming a profiled shape, similar to an aircraft wing:
- Higher drive for the same sail area compared to soft sails.
- More precise shape control through trim and hydraulics.
- Less friction than rigid wingsails – lighter and more repairable.
The headsail (jib) is changed depending on wind strength and course. In tight match race duels, the right sail combination often decides boatspeed and manoeuvrability.
Hydraulics and Grinders
All moving elements – foils, sails, rudder – are operated via hydraulic systems powered by grinders using hand cranks (hand grinders) or ergometric stations (cycling grinders). There are no engines during racing; every watt of power comes from the crew.
Important: On the AC75, the crew are not just sailors but also energy producers. Grinder performance directly determines how quickly foils and sails respond – and thus victory or defeat.
Flight Control: Flying on Water
Flight Control in Flight
A foiling boat is unstable. Flight control keeps it in the air:
- Height control – Too high: stall risk. Too low: hull in the water, massive drag.
- Roll stability – Heeling is balanced via foil canting, crew weight and rudder.
- Pitch control – Bow vs. stern height affects lift and manoeuvrability.
Modern AC75s use sensors and real-time data (within the class rules). The flight controller works closely with the helmsman – coordination errors lead to speed loss or capsize within seconds.
AC75 speed development: Average racing speed Auckland 2021 approx. 35–40 knots, peak values over 53 knots (Emirates Team New Zealand). For comparison: AC50 Bermuda 2017 approx. 45 knots peak, classic IACC approx. 12–15 knots.
Manoeuvres in Foiling Mode
Tacks and Gybes on Foils
Foiling tacks and foiling gybes are among the most spectacular moments in AC75 racing. A tack on foils means:
- Reduce speed but maintain foiling mode.
- Switch foils – change active foil.
- Bring sails through the wind.
- Immediately accelerate again and return to stable flight.
Teams that execute manoeuvres cleanly in under 30 seconds gain decisive boat lengths. Faulty tacks cost 100 metres or more – often the race in match racing.
Pre-Start and Low Speeds
In the start phase, in light wind or during harbour manoeuvres, the AC75 is in displacement mode – the hull is in the water. Here the duality of the class becomes apparent: the boat must be both slow-manoeuvrable and extremely fast in strong wind. Transitions between modes are critical training content.
Tip: Observers should pay particular attention to transition phases when live tracking: teams that get on foils early and cleanly often win already on the first leg.
AC40 as Sister Class
The AC40 (40 feet) serves training, youth and Women's America's Cup. It transfers canting T-foil principles to four crew members – a technology transfer platform for young talent before moving to major syndicates.
36th Cup Auckland 2021 vs. 37th Cup Barcelona 2024
Auckland and Barcelona
At the 36th Cup in Auckland, Emirates Team New Zealand dominated with superior flight control. For Barcelona 2024, more challengers – INEOS Britannia, Luna Rossa, Alinghi – further developed their foils, hydraulics and soft wings. Different wind and wave conditions made the 37th edition a tough test of design adaptability.
AC75 Development Over Time
Comparison with SailGP F50
Those familiar with SailGP and the F50 catamarans will recognise parallels in foiling and speed. Differences lie in format and philosophy:
Checklist: Understanding AC75 Technology
For beginners and regatta enthusiasts – the most important concepts at a glance:
- Foiling basics – What is take-off, what is flight control?
- Canting T-foils – Why does the foil swing sideways?
- Twin-skin mainsail – How does a soft wing differ from a classic sail?
- Grinder system – Where does the energy for hydraulics come from?
- Crew roles – Who steers, who flies, who trims?
- Manoeuvres – How do foiling tacks and gybes work?
- Match racing context – Why does every boat length count in the duel?
- AC40 – How are youth development and the main class connected?
Future of Foiling Technology in the Cup
The America's Cup remains an innovation engine for sailing: carbon foils, flight control software and soft-wing constructions influence America's Cup boats and future classes. Larger formats (AC85) and more precise design rules are under discussion – the Cup continues to test the limits of foiling.
Warning: Foiling technology at AC75 level is not intended for recreational sailors – safety risks, costs and rulebooks make these boats the domain of professionals.
Frequently Asked Questions (FAQ)
How fast does an AC75 sail?
Top speeds over 50 knots are possible in optimal conditions – faster than most motorboats.
Why monohull instead of catamaran?
Tradition meets spectacle: the AC75 combines the classic silhouette of a single-hull boat with foiling speeds and technical challenge.
How many sailors are on board?
Eight core sailors plus additional roles depending on the rulebook – each with a specialised task from grinding to flight control.
What does an AC75 programme cost?
Programme costs run into hundreds of millions – design, build, crew and multi-year preparation make the Cup the most expensive sailing competition in the world.
How can you follow AC75 racing?
Live via TV, streaming and onboard cameras – flight control, foiling manoeuvres and match racing tactics are made visible for spectators.
Related Topics
- History and Tradition of the America's Cup
- What Is Foiling
- America's Cup Boats – Development of the Classes
- Foiling Tacks and Gybes
- SailGP: Format and F50 Catamarans
Last updated: July 4, 2026