Cup Spy Oct 17: System reset in Barcelona as breeze and seaway return to 'normal'

by Richard Gladwell/Sail-World NZ 18 Oct 2023 02:53 PDT 18 October 2023

Only two America's Cup Challengers American Magic and Emirates Team NZ, were reported as sailing on Tuesday in changed conditions to the day before - but more akin to that predicted for Barcelona - southerly seabreezes with an "off-axis" sea-state, which as we can see from the AC Wave Buoy still had much of Monday's height, but much longer interval, typical of a left over swell. Two other teams sailing AC40s in One Design mode were also out off Barcelona.*

What happened in the Cup - October 17, 2023:

• Emirates Team New Zealand sailed their AC75, working through a test program, which in the AC75 is limited to analysis of sailing technique, and some modification of legacy sails from the 2021 America's Cup.
• American Magic sailed their two AC40s, again in development testing - with flap changes to their test wingfoils and one design rigs.
• Alinghi Red Bull Racing - No report.
• Luna Rossa Prada Pirelli - No report.
• INEOS Britannia - No Report. Their test boat T6 is still in the shed after the catastrophic destruction of their rudder and rudder assembly during a towing session. They were sailing alone in their AC40 One Design.
• Orient Express Racing Team - sailed alone in their AC40 One Design.

Commentary: Playing the wind triangle

Emirates Team New Zealand had a under three hour mid-late afternoon training session off Barcelona. The session spanned the expected racing time, except that October 17, 2024, is a Reserve Day - following Race Day 5, by which time ten races should have been completed.

In fact, at that juncture, the 37th America's Cup may well be over.

In contrast to yesterday's discombobulated seaway of just under a metre, pushed up by a NE breeze on an overcast, rainy day. Today, there was a partial return to the more usual conditions of late - a southerly breeze and flatter seas, with some overhang from Monday's sea state.

Over the past three months, we have seen the occasional commentary from the teams on various test strategy options they have adopted.

Two scenarios are in play in the 2024 Cup design/test cycle. Teams can use their 40fters to test wing foils, sails, control systems, and even a different hull shape in the case of the Italians and the Brits.

Or there is the AC75 route - with the teams restricted to some modification of legacy sails and control systems.

Over the past three months in Barcelona, only two teams have seriously gone down the AC75 route, which is geared more towards full-size data gathering of performance in the sea and wind conditions experienced in Barcelona.

On the surface, that is a rather tedious approach, with other teams like American Magic testing up to four different wing foil designs, allowed under the rules, as well as gathering the performance data in their 40ft test boats.

Elise Beavis, a Performance Engineer with Emirates Team New Zealand, now in her third America's Cup campaign, offered some insights into the method of the Kiwi data madness.

"There's a few sides to my role," she told AC37 Recon Team's Justin Chisholm. "Part of it is when we're sailing in the simulator. I'm involved with creating models for that incorporating changes in conditions and looking into the data produced."

When the team is sailing, in the real as opposed to the digital world, she has a data analyst function, keeping one eye on the incoming data and also eyeballing what is happening a few metres away on the AC75.

A critical factor in the data collection process and its later use is resolving what Beavis calls the "wind triangle".

Most remember the triangle as that dreadful instrument given to the least musically talented to play at junior school orchestra, on the basis that any contribution was OK. However for the America's Cup teams the Wind Triangle is quite different, and must be played with great accuracy and precision.

"We've got the wind gear - at the front of the AC75, same as the AC40s - the cups that spin round and measure the apparent wind speed. [Which is the same wind you feel sticking a hand out of a car window on the motorway].

"And then we've got the wind vane giving a direction," she continues.

"So we do a little calibration on that because those numbers aren't perfect.

"And then we do another calibration to accommodate the presence of the yacht [and sails/rig] - so we have what's called upwash.

"Because we've got this boat and these big sails producing lift. The wind gear is not that far away, but further than with the AC40 - and we need some correction for the impact of the boat being there.

"That's one side of the wind triangle.

"And the other side is how fast the boat is going in what direction.

"And from that, we can work out the last side of the triangle. And that's our true wind speed and true wind direction."

The outcome of that calculation is that the raw performance data stream is scrubbed or calibrated using an identical common process to determine the true wind speed and direction, regardless of when it is collected.

Being in Barcelona from July to October with their 2021 Cup-winning AC75, the Kiwi team is in a great position to record a database of AC75 sailing information from the America's Cup venue.

From their summer sailing program in Auckland, they have a similar database of the same AC75 (which has been upgraded to the new version of the AC75 Cass Rule).

To some extent, that data from Barcelona can also be compared with the data gathered during the 2021 America's Cup Match and work-up in Auckland in the same boat to an earlier version of the AC75 Class Rule. That gives some idea of AC75 behaviour and performance data in an opposed Cup racing situation rather than just training runs.

"It's particularly interesting at the moment, being October, which is the best guess at what we'll see next year," Beavis explains.

"We can test more new components on the AC40s. But we can't change much on this boat - we can't change the underside, we can't change the foils. We can do some tweaks to the sails, but no new ones. So we can't do much development in that area."

"But we can learn about the conditions because, obviously, the foils and gear are all bigger with the AC75 than a shorter and lighter AC40."

"And as the waves get bigger, the AC75s can deal with it better than the AC 40."

How the more experienced AC teams in AC75s would cope was one of the big questions to be answered for all teams over the past four months in Barcelona with its notoriously tricky sea state. The potential problem was not answered by the early images sent back from the Joint AC37 Recon team of Alinghi Red Bull Racing coming to grips with B1, their first AC75.

"It can be quite different, especially the waves today were quite skewed to the wind."

"That's not something that we often see at home in Auckland. That's part of what's valuable being up here. And that seaway can really make some quite big differences between tacks."

Beavis, who is also the world women's champion in the foiling WASZP class, explains the AC75 seaway behaviour variance in racing dinghy parlance.

"If you're in a Laser or similar, and you've got some old waves pushing you forward upwind - you get some really good performance, in one direction, but not on the other tack/gybe."

It's the same on the AC75s, which can "surf" on their foils with wave assistance.

Emirates Team New Zealand are expected to shut down their AC75 test program in Barcelona in a few days. The AC75 will remain in Barcelona, with the data captured in Barcelona being on-sent to Auckland and massaged for use by the ETNZ design teams and also in the AC75 simulator.

Obviously, there are many other uses of a Barcelona performance database. One of the keys to the build-up for the upcoming America's Cup will be how others have captured the same data. While there may/may not be conditions that can be replicated on the water, accurate computer simulation overcomes most of that issue.

The intriguing point will be if and how various teams engage AI to work through the database and offer up some design and sailing options for simulator and on-the-water testing.

AC37 Joint Recon Team Reports:

Emirates Team New Zealand - AC75 - October 17, 2023 - Barcelona from Justin Chisholm - ETNZ Recon Unit

A forecast of light inconsistent breeze for this morning saw Emirates Team New Zealand set a 1430hrs dock out time for their second sailing session of the week aboard their AC75 in Barcelona. After rolling out on time at 1300hrs this afternooon the Kiwi AC75 was rigged and launched by 1330hrs before - for reasons unknown - dock out was pushed back by 30 minutes to 1500hrs.

With the M1-3 mainsail and J3-6 headsail hoisted and two guests on board the boat left the harbour at 1522hrs and was soon foiling downwind in a 12-knot southerly breeze that kicked up a light chop that became mixed in with a long 0.5 metre swell from 060° that was left over from yesterday's stronger north easterly breeze.

After the initial long downwind run with several foiling gybes the boat turned back upwind for slightly longer beat that took the boat south of the harbour entrance. A second windward / leeward lap followed before a 10-minute stop at 1600hrs.

The second sailing session lasted 25 minutes and saw more windward / leeward free sailing before the boat came to a stop at 1625hrs for a cyclor change lasting 10 minutes.

The third session - lasting an hour and briefly punctuated by a minute and a half stop midway through - saw more windward / leeward free sailing but with a slight increase in the rate of tacking and gybing. The final 20 minutes of sailing saw the breeze start to fall away below 10 kts making things tricky for the crew during the final batch of tacks on the last upwind section to the harbour entrance. Time was called at 1725hrs with sails down by 1735hrs and dock in taking place at 1745hrs.

Session Statistics: Emirates Team New Zealand - AC75 - October 17, 2023 - Barcelona

• Weather: Cloudy 22°C
• Wind Strength 8-12kts
• Wind Direction: 180° - 200°
• Sea State: Light wind chop from 0180° Residual swell 0.5m from 060°
• Crane In: 1330hrs Dock Out: 1500hrs
• Dock In: 1745hrs Crane out: 1815hrs
• Total Tacks: 33 - Fully foiling: 31; Touch & Go: 3; Touch Down: 0
• Total Gybes: 30 - Fully foiling: 26; Touch & Go: 0; Touch Down: 0

Crew: Peter Burling (Starboard) Nathan Outteridge (Port), Andy Maloney (Starboard) Blair Tuke (Port).

Cyclors on rotation: including: Louis Sinclair, Sam Meech, Simon Van Velthoven; Dougal Allan, Marcus Hansen; Cameron Webster, Louis Crosby

American Magic - AC40 x 2 - October 17, 2023 - Barcelona - from Sebastian Peri Brusa - NYYC AM Recon Unit

New York Yacht Club American Magic (NYYCAM) rolled out Magic at 11.45hrs and America at 12:20hrs. Both AC40s on LEQ12 mode.

Magic with the same foils' configuration as yesterday and the past two weeks, with foil wing and flap #1 on the port side and #4 on the starboard side; while America's foils were switched during the last weekend. Foil wing and flap #2 are now on the port side, while foil and wing #3 are on the starboard side.

Magic was craned to the water at 12:15hrs, and then America followed at 12:45hrs. Both boats docked out at 13:55hrs, as planned.

One-design main sails were selected for both boats, which were hoisted at 14:05hrs while coming out of the port. Once out, one-design J1s were hoisted at 14:10hrs.

From 14:30hrs till 15:25hrs one long straight-line speed test upwind and downwind was carried out, in bottom-end southerly wind conditions, combined with an ENE swell that was left from yesterday.

Magic was consistently faster and higher on both tacks on the upwind, and slightly faster on starboard tack on the downwind. Nothing conclusive could be extracted from the downwind port tack speed test.

At 15:25 there was a break until 15:40, when the J1s were replaced by J2s.

At 15:40 another upwind and downwind was executed but focused on the tacks and gybes. Approximately, 9 tacks and 6 gybes were done per boat on each leg, respectively.

Magic was more comfortable and consistent tacking and gybing, never falling from the foils, while America fell-off and landed completely on one tack and on one gybe.

On top of that, in these conditions it seems like onboard America the error margin is a lot smaller than in Magic and, as usual, when the wind gets lighter tacking into the foil with the smallest area of the four (foil #2 on America) is hard. Magic was first at the top and at the bottom virtual marks.

After another 20-minute break, at 16:35 two one-lap upwind-downwind races took place, with virtual boundaries and virtual marks, doing rabbit starts, and seven to eight tacks on the upwind and five to six gybes on the downwind.

Magic was ahead on the four mark-roundings for a considerable margin. Differences were larger in racing mode than in straight-line speed testing mode. America nose-dived at least once per leg.

An extra upwind was sailed, heading back towards the port, performing some tacks in a dyeing breeze with J2s.

Both boats entered the port and lowered their sails at 17:40hrs, docked at 17:55hrs, and America was the first of the two to be craned out at 18:25 indicating the end of the day.

Session Statistics: American Magic - AC40 x 2 - October 17, 2023 - Barcelona

• Weather: Part Cloudy 17°C
• Wind Strength: 7kts- 11.5kts
• Wind Direction: 160° - 190°
• Sea State: 0.62mtr, ENE
• Crane In: 1215hrs(Magic) 1245hrs (America) Dock Out: 1355hrs Both Magic and America
• Dock In: 1755hrs (both) Crane out: 1825hrs(Magic) 1855hrs (America)
• Total Tacks: 27 - Fully foiling: 23; Touch & Go: 0; Touch Down: 4
• Total Gybes: 23 - Fully foiling: 20; Touch & Go: 0; Touch Down: 3

Crew: America: Tom Slingsby (stb), Paul Goodison (port), Riley Gibbs (stb), Andrew Campbell (port).

Magic: Lucas Calabrese (stb), Harry Melges (port), Severin Gramm (stb), Michael Menninger (port)

Weather Observations - Port Olimpic - 17 October, 2023

The breeze recorded at Port Olimpic at a point 12 metres above waterlevel eased slightly to an average of 12.5kts, gusting to just above 15kts. The breeze was at its peak for a much shorter time than the previous day and for the majority of the sailing period (between 1200hrs and 1800hrs) was below 10kts average and gusting only slightly above that level in "gusts". The directional pattern of the breeze was steady around 180°-190°.

The wave height at the America's Cup Buoy showed the waves only dropping overnight by 0.1mtrs to 0.7mts but with the period between waves increasing from 3secs, the day before to 5.5secs on Tuesday.

Additional Images:

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. Weather information is by Predictwind. * By agreement between the teams, there is no AC37 Joint Recon reporting of teams that are sailing AC40s in One Design mode.