The class rules and technical regulations for the 38th America's Cup in Naples 2027 have been published. One of the most important decisions is to reuse the hulls from the 37th America's Cup in Barcelona 2024 or modified versions from the 36th America's Cup in 2021. This measure was taken after detailed analyses showed that the hull shapes themselves make only minimal differences in speed. The real performance gains lie in the foils and systems.
Dan Bernasconi, Chief Designer for Emirates Team New Zealand and one of the main authors of the rules, explains: "As a collective between Defender and Challenger of Record, we analysed all the hull shapes used in Barcelona on the AC37 and realised that the speed differences in hull shapes alone were minimal. All the gains were in foils and systems, so it made perfect sense to focus the design time on these development areas and reuse the hulls."
The one-hull revolution
The rule change regarding the hulls is drastic. Each participant is limited to a single stock hull that has already been used in the AC36 or AC37. This measure is intended to control costs. Only limited modifications to the stock hulls are permitted:
- Changes to the hull surface within defined "crew zones"
- Modification of up to 4 m² hull area without changing the corresponding surface
- Modification of up to 4 m² hull top for sliding covers
- Replacement of the bow area to fulfil the "constructed-in-country" requirement
Stock hulls from AC36 may be modified with a reduced retained percentage of 87.5 per cent, while newer hulls from AC37 are more strictly regulated.
No more cyclists
Another radical change concerns the internal structure of the yachts: The pedal drives will be eliminated in favour of stored energy. The specification of a single battery unit that will power all moving parts on the AC75 is to be published shortly.
This rule is accompanied by another significant change that affects the composition of the crew. Each AC75 yacht will sail with five crew members instead of eight, with at least one woman on board. This expansion to five active crew members means a greater emphasis on racing strategy and tactical sailing. The focus in crew selection will once again be more on sailing performance, as no specialised athletes will be required for the pedal drives.
In addition to the America's Cup itself, there will once again be a Women's and Youth America's Cup give. The rule with a female crew member in the America's Cup is intended to bring the Women's America's Cup teams of each syndicate closer to the actual Cup, as rotation will be inevitable and a large talent pool will be needed for the entire campaign.
A "Guest Racer" cockpit will also be introduced, allowing a non-team member to sail on board an AC75 during the race - a new edition of a programme last seen in Valencia in 2007. This is intended to open up the America's Cup to a wider audience.
It will be exciting to see how the designers distribute the crew members on the boats. In the last Cup, each team had two helmsmen, one on each side of the boat, plus three more people on each side, trimmers and cyclists. There were no changes of position in manoeuvres. Now an odd number of crew was determined. Either a crew member will change sides or the "understaffed" side will be filled by a guest.
Strict component limits
The restrictions in the new regulations extend far beyond the fuselage. The new regulations set clear limits for all controlled components:
| Component | Stock quantity | New quantity | Total quantity |
| Hulls | 1 | 0 | 1 |
| Foil arms | 4 | 4 | 4 |
| Foil wings | 3 | 3 | 6 |
| Foil flaps | 3 | 5 | 8 |
| Rudder | 2 | 1 | 3 |
| Masts | 2 | 0 | 2 |
| Mainsail | 8 | 12 | 20 |
| Foresail | 10 | 13 | 23 |
The rules for the components
- Three older Foil wings from the AC37 can be adjusted by up to 20% within narrow parameters, and the teams are allowed to build a total of three new foil wings, again within fixed parameters.
- Three existingFoil flaps can be adjusted by 20% and the teams can build a total of five new foil flaps.
- The One DesignFoil armswhich have remained unchanged since the creation of the AC75 class are reused.
- For the teams that have two AC37 Masts have built, no new masts were authorised. Only one team, Orient Express Racing, built just one mast, so they would be allowed to build another one within tight parameters and with a similar design for Naples 2027.
- A total of four old Mainsail and six new mainsails are authorised; each of these elements can be recut an unlimited number of times as long as 85% of the original remains.
- 13 new Foresail are allowed, plus 10 old jibs, making a total of 23 for the teams - with the same re-cut authorisations as the mainsail.
- Only 1 new Rudder is permitted.
- Changes to Control, hydraulics and electronics are unlimited, as long as they can be installed in the existing hull moulds.
Stock components and stock replicas
The rulebook introduces the concept of "stock replicas", which allows new teams in particular to build components that exactly match the designs from previous Cups. Veteran teams may only build stock replicas under certain conditions, for example if the original component has been sold or irreparably damaged.
Special quotas for stock replica sails apply to new teams:
- 4 Mainsail
- 5 Foresail
However, these sails may only be used on the corresponding existing hull.
For new teams that do not have their own stock hull, there is the option of a "legacy replica", which means that they can build a hull that exactly matches an existing stock hull - but is not a completely new design.
Ban on wind tunnel tests
The new rules prohibit any model testing in controlled environments such as wind tunnels or towing tanks. Teams are not allowed to receive or use model test data that is not publicly available. This is a further step to lower costs and reduce competitive advantages through expensive test infrastructure.
There are also new requirements for the support boats: All teams must use eChase boats that are powered by batteries, hydrogen or biofuels. These must have a minimum length of 10 metres, a minimum maximum speed of 35 knots and a range of 75 nautical miles.
Training phase and preparation
The teams will now start customising their AC75 yachts, with a lot of training focused on the AC40 class. Here, teams will be allowed to enter two boats for the three planned preliminary regattas in 2026. At these regattas, teams will be able to enter two boats, with one being a mix of youth and women sailors as per Protocol must have. The teams will be allowed to train with their AC75 yachts again from 15 January 2026.
The teams must now make important decisions that will determine the overall success of each campaign. In particular, the construction and introduction of the three permitted new foils will be crucial, with the sailing team needing time to test and familiarise themselves with each foil.
A new era in the America's Cup
The AC38 Technical Regulations mark a paradigm shift in the America's Cup. Instead of unlimited technological upgrades, the competition is now focussing on:
- SustainabilityReuse of existing components and requirements for environmentally friendly support boats
- Cost control: Strict limits for new components and expensive tests
- Fairer competitionJoint information and equal access to environmental data
- TransparencyOpen process for rule interpretations
These changes could make the America's Cup more accessible to new teams and at the same time significantly reduce the overall costs of a campaign. It is estimated that the new rules will help to achieve the goal of a campaign budget of around 60 million euros - significantly less than the three-digit million amounts of previous campaigns.
