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Cup Spy Oct 3: AC75 teams get vital light air testing session at Barcelona

by Richard Gladwell/Sail-World NZ 3 Oct 2023 21:21 PDT 4 October 2023
Alinghi Red Bull Racing - AC75 - Day 87 - Barcelona - October 3, 2023 © Paul Todd/America's Cup

Two teams, Emirates Team New Zealand and Alinghi Red Bull Racing sailed their AC75s off Barcelona in light airs.

The British team was also sailing in their AC40 One Design, unfortunately there is no coverage of AC40s sailing in One Design mode by the AC37 Joint Recon Team.

Wind strength measured by the nowcasting at Port Olimpic adjacent to the America's Cup course showed the winds building to 6kts at 1400hrs before easing and then building back to 9kts around 1800hrs. Recordings from the AC37 Joint Recon Team with the Kiwi team recorded winds of 6kts increasing to 8-9kts at 1600hrs from SSE (120degrees), before fading.

The wind limit for racing is 6.5kts measured on a 30 sec rolling average measure from 9mins to 4mins before the start. Takeoff wind speed for an AC75 to get foilborne is reckoned to be in the 6-7kt range. Of course, wind shear can affect wind strengths above sea level, and AC75s can take off in winds that appear to be lighter at sea level.

It would seem likely that the 2024 America's Cup will be sailed in light airs - requiring the teams to have confidence in their ability to start foiling in winds at the bottom end of the range, and to be able to remain foiling during tacks and gybes while remaining foil-borne, if the winds drop below the 6.5kts test at pre-start.


Emirates Team New Zealand is expected to continue sailing until the end of October, when the team will relocate to New Zealand and should be the beneficiary of El Niño's return to southern climes.

Coach Ray Davies told AC37 Joint Recon Project's Justin Chisholm, that the team did not expect to be missing too much by leaving Barcelona, the venue for the next America's Cup, which for the Defender, starts on October 12, 2024.

The Challengers start their Selection Series two months earlier in mid-August 2024.

"I think coming November is flick-a-switch time, here. Daylight saving ends [October 29], and it gets dark much earlier. Conditions are very different to what we see in September and October. So we won't miss out on too much there," Davies explained.

New Zealand is also expecting the arrival of El Niño weather system, which should see more SW (offshore) winds and less rain. Because Auckland is located on an isthmus, without the influence of a significant land mass, between the Pacific Ocean to the east and the Tasman Sea to the west, it is one of the few places in the world that experiences a double-seabreeze.

From what we have seen of the Barcelona weather pattern over the past couple of months, it follows a familiar pattern to Auckland in an El Niño summer, with one of two sea breezes building during the day and dying away in the evening.

The difference is that the breeze is usually from the South in Barcelona, while Auckland can vary between NE and SW on successive days.

With just a few weeks left, and as the 12-month Cup window arrives in just over a week, the Swiss and New Zealand teams want to extract as much intel as possible from the current light, or bottom end of the racing wind-range, conditions.

Interestingly, American Magic, the only other team with an AC75 in Barcelona, have not yet sailed that boat at the Cup venue - preferring to two-boat test in their AC40s.

Today, the breeze started light but increased in the Kiwi training area to around 10kts by the end of the session, around 1730hrs CET.

"It was a fantastic day. It's nice when you have conditions like this where you can scroll through a lot of the tests and information," Davies said.

"We had a lot of the time in quite light conditions, which is invaluable. Normally, the breeze is building or is not quite enough. So this was a really good day for bottom-end conditions."

As well as the Swiss AC75, the British team were also out getting bottom-end practice in their AC40 - in conditions with which they struggled sailing their AC40 in the first Preliminary Event in Vilanova a few weeks ago.

The presence of the AC75 in the same patch of water as the AC40 highlighted the difference in power between the two foiling monohulls, with the AC75 being able to lift onto its foils much more readily than the AC40.

"In these boats, you can do quite a bit more with the sails compared to the AC40," Davies explained. "The big sails can generate a lot of horsepower. So it's important that you know how to manipulate them effectively in the light air."

Davies wouldn't be drawn on the key differences between ETNZ's current America's Cup champion, Te Rehutai and their new raceboat, expected to be launched in January-February 2024.

"We're obviously moving towards what we think the future is, so there's a lot of stuff that no one will ever know until after the Cup. We're working hard to make the incremental gains that should all add up to something significant compared to where we were last time."

A key difference between the 2021 Cup and the upcoming 2024 event is that Te Rehutai was designed and signed off with construction commenced before the Kiwi's first boat, Te Aihe - since purchased by the Swiss - was launched. In other words, there was no significant design data or sailing experience from Te Aihe put into the hull design for Te Rehutai. The same constraint may have applied to the other teams.

In this Cup cycle, the Kiwis have two years and one Cup campaign of intel and performance data to draw on, plus what has been learned from the AC40, which is a design development of Te Rehutai.

In the first Cup using AC75s, in 2021, all teams were forced to rely on their various computer design packages - while this Cup will see a mix of actual performance data and computer design and performance prediction packages used. The output will be intriguing.

Of course, the AC75 hulls are the first design component to be locked off. Other significant components such as wingfoils, rudder elevators, mechatronics, masts, sails and all onboard systems also hit their design deadlines before the Cup, with sails being the last component to have a deadline - often between rounds in the Cup racing.

As Defender, the Kiwi team has two more months of workup (and can be later with their design lock-off) than the Challengers, who must be at their peak in mid-August for the start of the Challenger Selection Series.

"Everyone must be under construction now, so they're definitely locked in on hull shapes and designs and structure and all of that," Davies remarked.

"I think most teams are within a couple of months of each other's launch date," he added.

"No one wants to launch too early because they're missing out on development time. And you obviously can't go too late because you risk not being ready. I think we'll all be popping boats out three or four months before the Cup," Davies opined.

All teams must compete in the second Preliminary Event in Jeddah in late November (no decision has been announced on the US team's request to be excused).

By early 2024, Davies expects to "have a couple of AC40s and the new boat back in New Zealand for the summer - similar to what we had last summer back there. "

"Any feeling you might be missing out on some Barcelona conditions while you're away?" Chisholm asked.

"Not really. I think it's going to be quite different," Davies replied.

AC37 Joint Recon Team Report:

Emirates Team New Zealand - AC75 - October 3, 2023 - Barcelona

Emirates Team New Zealand started their second week of AC75 sailing in Barcelona with an initially super-light air session that developed later into around nine knots of southerly wind.

Sea conditions were flat all day which helped with initially coaxing the Kiwi B2/Te Rehutai into the air several times under its own steam, but for much of the early part of the day the crew had to resort to hitching a ride on the back of one of the team's two chase boats that are always close by.

B2 rolled out at 1230hrs and was rigged and launched by 1310hrs ahead of a fractionally delayed 1405hrs dock out.

The M1-3 mainsail and J1-3 headsail were hoisted by 1420 with the boat leaving the harbour at 1420hrs.

If there was ever a debate about whether the AC75 or the AC40 had the best power to weight ratio in bottom end foiling conditions, the answer came loud and clear today when in the Kiwi AC75 sailing at the same angle as the British AC40 in no more than 7 knots was comfortably able to reach take off speed and leave the AC40 in its wake. (See highlights video 00.49 to 01.28).

Despite this early foiling success the crew soon had to resort to tow ups for the next five take offs until around 1600 the wind squeaked into the eight to nine knot range that allowed for self take offs.

In contrast to much of last week's sailing sessions, when the crew was focused on sailing practice laps of a virtual course, today the sailors seemed more interested in experimenting sail trim on long straight line runs.

On many occasions members of the crew could be seen moving around the boat while foiling and photos were observed being taken of the sails from deck level. That said, the final part of the day – after the only cyclor change over at 1600 – was given over more to maneuvers with a string of 22 quickfire gybes over a circa 20 minute downwind run, as well as a series of repeated aggressive round ups and bear aways.

A change from the J1-6 to the J2-6 at 1655 was followed by 35 minutes more of the same unpredictable maneuvering before time was called at 1730hrs.

Sails were dropped by 1740hrs and the team docked in at 1755hrs. Another AC75 sailing day is planned for tomorrow (October 4).

Alinghi Red Bull Racing - AC75 - October 3, 2023 - Barcelona

Alinghi Red Bull Racing (ARBR) went for another light wind session today in Barcelona.

ARBR team rolled their AC75 at 09:45hrs, and after the mast procedure, the yacht was craned into the water and placed alongside the chaseboat where they tested the hydraulic systems.

At 10:00hrs, they left the dock and hoisted the main and J1 inside the port.

They towed the yacht out for twenty minutes and started sailing in displacement mode in the vicinity of Badalona. Having not enough wind to take-off, all their attention was on the main sail skins and the leech from the J1.

At 15:00hrs, they towed the AC75 fifteen miles away from Barcelona along the coast, until catching the cloud line where the wind was reaching 8 knots from 120º. They started foiling upwind on their port tack at 24knts of speed, until they did one touch-down tack . They proceeded with one unsuccessful assisted take-off that made them stop, as they were struggling with the light wind conditions. At 15:40hrs, with a building 10knts breeze that didn't stayed long, they dropped the J1 and hoisted the J2.

In the first stint, they did 3 tacks and 6 gybes in twenty minutes, sailing at 36knts and apparently with their nose down. At 16:35h, they started the second stint, which consisted in a 11 gybe downwind. At this point, we spotted them touching down and struggling every time that they were dropping their starboard foil after the gybes.

With a light breeze barely reaching the 5 knots the team decided to lower the sails and tow the AC75 back to port.

ARBR docked in at 18:00hrs, after foiling for 1h 5min out of 3h 22min and 54nm session out on the water.

This commentary was written and compiled from video, still images and statistical content extracted from the AC37 Joint Recon program and other material available to Sail-World NZ including photo files, and other on the water coverage from the 2010, 2013, 2017 and 2021 America's Cups. Its format is intended to give Sail-World readers a snapshot of all teams' progress on a given day or period.

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