America’s Cup: Differences in design

The much-anticipated launch of the first two AC75 foiling monohull yachts from the Defender Emirates Team New Zealand and USA Challenger NYYC American Magic respectively did not disappoint the masses of America’s Cup fans waiting eagerly for their first glimpse of an AC75 ‘in the flesh’.

© Emirates Team New Zealand

Emirates Team New Zealand were the first to officially reveal their boat at an early morning naming ceremony on September 6. Resplendent in the team’s familiar red, black, and grey livery, the Kiwi AC75 was given the Maori name ‘Te Aihe’ (Dolphin).

Meanwhile, the Americans somewhat broke with protocol by carrying out a series of un-announced test sails and were the first team to foil their AC75 on the water prior to a formal launch ceremony on September 14 when their dark blue boat was given the name ‘Defiant’.

But it was not just the paint jobs that differentiated the first two boats of this 36th America’s Cup cycle – as it quickly became apparent that the New Zealand and American hull designs were also strikingly different.

© Amory Ross / NYYC American Magic

On first comparison the two teams’ differing interpretations of the AC75 design rule are especially obvious in the shape of the hull and the appendages.

While the New Zealanders have opted for a bow section that is – for want of a better word – ‘pointy’, the Americans have gone a totally different route with a bulbous bow that some have described as ‘scow-like’ – although true scow bows are prohibited in the AC75 design rule.

The differences between the two AC75 hulls do not stop there, with the two design teams taking significantly contrasting approaches on the underwater profiles of their AC75s as well.

While the American Magic AC75 appears to have been built with an all but totally flat underwater section, Emirates Team New Zealand’s boat has a pronounced longitudinal bulge underneath running almost from bow to stern.

© Emirates Team New Zealand

These two different approaches have set the sailing world alight with fans speculating over the thinking is behind each of them and pondering what the sailing characteristics of each boat might be.

Despite being very different the images of the two boats reveal some similarities as well such as the cockpit layout. Both teams have their cockpit divided in two by a central extension to the forward deck, creating two pits in which the crew can operate low down and out of the airstream.

There will be plenty of improvements to come on how teams will maneuver the boats but so far both teams seem to have decided on fixed positions for their grinders who won’t cross sides during tacks and jibes.

With foiling now established for the America’s Cup, a key focus for designers has been to make the foils more efficient. Once again designing the shape, width and thickness of the foil wing is a trade-off between speed and stability.

© Amory Ross

The path chosen by the two teams have been very diverse.

Emirates Team New Zealand has two different foils: one with anhedral angle and the other one which is straight.

American Magic, on the contrary, seems to have two very similar foils wings in terms of shape and that’s probably because the Kiwis are still testing solutions whereas the Americans having been sailing consistently with their test boat, might have already got to some key conclusions.

Given that we can expect the teams to build and test a multitude of shapes in the run up to the 36th America’s Cup, there is probably little to be gained from too much analysis there at this stage.

After almost a decade, soft sails are back in the America’s Cup and a lot of effort has been put in by the teams adapting the twin skinned mainsail concept to the new Class Rule with the main difference between the two AC75 appearing to be the boom position in relation to the mainsail foot.

The Americans sporting a conventional boom, whereas the Kiwis have opted for a deck-sweeper mainsail foot, not unlike those used on the latest A-Class catamarans.

Despite all their differences – in their bows, underwater sections, and other design features – it is worth noting that both boats were foiling (and seemingly stably) within hours of going sailing for the first time. That is a remarkable achievement for both syndicates and a testimony to both the designers and builders, as well as to the efficacy of the AC75 design rule itself.

And it seems we will not have to wait very long for the next two AC75s to see the first light of day. The Italian Official Challenger of Record Luna Rossa Prada Pirelli Team is scheduled to be the next to launch on October 2, with the British INEOS Team UK syndicate following suit two days later.

Could we see two more surprising design ideas on show then?

Source: AmericasCup.com

In addition to Challenges from Italy, USA, and Great Britain that were accepted during the initial entry period (January 1 to June 30, 2018), eight additional Notices of Challenge were received by the late entry deadline on November 30, 2018. Of those eight submittals, entries from Malta, USA, and the Netherlands were also accepted. Here’s the list:

Defender:
• Emirates Team New Zealand (NZL)

Challengers:
• Luna Rossa (ITA) – Challenger of Record
• American Magic (USA)
• INEOS Team UK (GBR)
• Malta Altus Challenge (MLT) – WITHDRAW
• Stars & Stripes Team USA (USA)
• DutchSail (NED) – WITHDRAW

Of the three late entries, only Stars+Stripes USA remains committed, but they still must complete the entry fee payment process before they will be eligible to race. They have already paid their initial payment but as a late entry challenger under the Protocol they also have a liability to pay a US$1million late entry fee due in installments by October 1, 2019. This deadline coincides with the venue schedule which has the construction of their team base beginning in late 2019, which we assume was done in the event the team is unable to fulfill their payment deadline.

Key America’s Cup dates:
✔ September 28, 2017: 36th America’s Cup Protocol released
✔ November 30, 2017: AC75 Class concepts released to key stakeholders
✔ January 1, 2018: Entries for Challengers open
✔ March 31, 2018: AC75 Class Rule published
✔ June 30, 2018: Entries for Challengers close
✔ August 31, 2018: Location of the America’s Cup Match and The PRADA Cup confirmed
✔ August 31, 2018: Specific race course area confirmed
✔ November 30, 2018: Late entries deadline
✔ March 31, 2019: Boat 1 can be launched (DELAYED)
✔ 2nd half of 2019: 2 x America’s Cup World Series events (CANCELLED)
October 1, 2019: US$1million late entry fee deadline
February 1, 2020: Boat 2 can be launched
April 23-26, 2020: First America’s Cup World Series event in Cagliari, Sardinia.
During 2020: 3 x America’s Cup World Series events
December 10-20, 2020: America’s Cup Christmas Race
January and February 2021: The PRADA Cup Challenger Selection Series
March 2021: The America’s Cup Match

AC75 launch dates:
September 6 – Emirates Team New Zealand (NZL), Boat 1
September 10 – American Magic (USA), Boat 1; actual launch date earlier but not released

Details: www.americascup.com