America's Cup Rialto: December 23 - The Elephant in the Room
by Richard Gladwell, Sail-World NZ 23 Dec 2020 10:39 AEDT
23 December 2020
Te Rehutai, Emirates Team New Zealand - wins the ACWS - December 20, 2020 - Waitemata Harbour - America's Cup 36 © Richard Gladwell / Sail-World.com
The America's Cup World Series which concluded on Saturday was determined not by who could sail the fastest. Not by who could do a dry lap. Not by the slickest in foiling tacks and gybes. Not by the best match racer. But by who was able to stay, or get foiling in the lightest of windspeeds.
In the second leg of the final race of the America's Cup World Series, a long chase began after Emirates Team New Zealand dropped off her foils squeezing to get around Mark 1 - allowing Spithill/Bruni to extend their already handy lead at Mark 1 from 250 metres to 800 metres.
"We're just going to shoot it", Kiwi skipper Peter Burling said to his crew as he squeezed the AC75 around the mark sailing at just 10kts, off the foils, compared to Francesco Bruni's foiling 28kts just 30 seconds earlier.
"Let's gybe," he said 30 seconds later, after which the boatspeed halved to a pedestrian 5kts.
"It's going to be a real horror race from here, fellas," he said, for the benefit of those crew who could not see, as the Kiwis completed the gybe still sailing at sub-10kts as the race leader, Luna Rossa, faded into the distance, still foiling fast.
"I don't think we'd have got out of it the other way either [by tacking]", he added to the pregnant-pause ridden on-board comms dialogue - which featured a tactical and performance dialogue amongst the five members of the ETNZ afterguard.
In the commentary booth, Nathan Outteridge, Burling's long-time sailing rival in two Olympics, and the 2017 America's Cup looked at the apparently hopeless situation and declared "this could all change inside 30seconds". It proved to be a prescient comment.
About half a minute later the Kiwis got the first sniff of an increase in breeze, lifting to 8kts - the first time in the race they'd had the same as the Italians, who'd been sliding away at 30kts, and sailing at four times the wind speed.
Although Luna Rossa had an impressive speed through the water, the real story lay in the VMG [Velocity Made Good, or speed directly towards the next mark] - a navigational calculation spat out by the performance and navigation computers.
Despite their impressive 28-30kts of speed through the water, the Italians were only making an effective speed of 7kts in the direction of the leeward mark.
Their opponents, still at the top end of the course, were limping along, off their foils, at just 6kts boatspeed, but making only 1-2kts VMG.
Spithill gybed, hitting 31kts in 8kts of breeze and briefly getting his VMG up to 15kts, through the gybe, before handing the helm over to his alternate helmsman Francesco Bruni.
As Bruni exited the gybe, Luna Rossa's boat speed dropped to 16kts as the race leader dropped off the foils, with a lead of 805 metres.
Almost a kilometre behind, the Kiwis boatspeed had just cracked double digits but were still 4kts slower than the Italians. The telling number was in the VMG with Bruni making just 1kt VMG and Burling 0kts - meaning he was making no progress at all toward the bottom mark, and Bruni only fractionally.
The chase was on!
The chasedown begins
Despite now sailing in exactly the same 7kts of breeze, albeit, with a 10-degree difference in direction, the kiwis began accelerating and sailing faster than Luna Rossa.
Burling and friends, were first onto their foils, lifting off at 20kts of boatspeed, and then gybing at 28kts in just 8kts of breeze.
Luna Rossa's boatspeed had picked up to a meagre 13kts - but an improvement on the ten knots they were achieving a minute earlier.
Once up on foils, the New Zealanders were away, briefly out-stripping their chase boat as they quickly accelerated to 30kts in just 8kts of wind.
When the Italians were overtaken, or rather Emirates Team New Zealand crossed their course, the Kiwis were making 14kts VMG compared to the Italians 0kts VMG - despite Luna Rossa sailing in the stronger 10kts of breeze.
The Kiwis relentlessly continued the Italian paddy-whacking as Burling extended their lead by a further 300 metres at Mark 2.
The dramatic Leg 2 turnaround in the final race of the ACWS underlined the unique sailing dynamics of the AC75, and actually determined the winner of the Prada ACWS trophy.
The race data analysis reveals that the edges in marginal foiling conditions are a lot fuzzier than we've been led to believe - and that the gains are significant.
That same lesson illustrated differently in the Xmas Cup - where spectators witnessed the bizarre sight of Emirates Team New Zealand and INEOS Team UK having a gybing duel on the final leg to the finish for ETNZ. Both boats off their foils - but the hapless Brits were really two legs behind.
The key take-outs from the Luna Rossa/Emirates Team NZ encounter was how quickly such a distance could be lost, and regained, in just over half a downwind leg, and then increased by as much as the original margin.
Occasionally in all yacht racing - a backmarker gets private breeze and sails around the becalmed fleet to take the win. But this is not the situation here.
Code Zero conundrum
This game of AC75-style poker is a scenario that could be played out several times during racing in the next couple of months.
One of the burning questions in the media sessions has been why Code Zero's, which could provide the sail area to provide the horsepower to get foiling, stay in the sail locker.
The AC75 class rule requires that if the Code Zero weights less than 90kg, then a compensating weight must be secured on top of the deck at the centreline. Presumably, if no Code Zero is carried then a full 90kg of compensator must be fitted. And of course, teams would not want to carry both the compensator and the Code Zero.
If the sail were to be rigged, that decision would, according to one answer given, have to be made at least 10 minutes before the start.
A close look at photos of the Code Zero's tack point on Luna Rossa, Emirates Team New Zealand and INEOS Team UK reveals that there is no furler fitted, as is usual for furling headsails.
Instead, the whole arrangement is designed for aerodynamic efficiency. The Code Zero is not easily removed - prompting the comment from the teams that if the Code Zero use call is made, it must be set up before the and remains there for the duration of the 25-minute race.
It is hard to believe that with all their resources, one of the four super-teams could not get a Code Zero adapted for Americas Cup use - given that the furling equipment is available off the shelf. One of the world leaders in the technology KZ Race Furlers is located in Auckland, who advise that "each team has a unique, custom furling system for their Code 0 from KZ Racefurlers".
Testing the Code Zero
The final leg of the only race started in the Xmas Cup was a replay of the endgame in one race from San Francisco in the 2013 America's Cup, where Team New Zealand failed by a narrow margin, to finish a light air race, which determined that regatta's outcome.
Maybe the Kiwis have learned from that experience.
In early December, we reported Emirates Team New Zealand training with the Code Zero in its ideal conditions.
"For reasons that are not entirely clear the defending champions are putting in a lot of time with the super-sized jib, flying it whenever the conditions allow, while the other teams very quickly get onto their #1 hull hoist jib and get foiling with that," we wrote.
"As they have done before Emirates Team New Zealand, used the sail upwind and down, including tacks and gybes. They seem to have mastered the foiling gybe, but upwind the drag from the big sail is said to be a killer."
A couple of weeks earlier, after a day on the Hauraki Gulf similar to Saturday, when the sea breeze crumped out, the three Challengers went to the inner Waitemata harbour on the top end of Course C to get some training done using the new westerly breeze.
Two challengers, Luna Rossa and INEOS Team UK, flew their Code Zeros, while American Magic sailed around using what they call a "J1" or jib with the maximum luff length of 20 metres.
Luna Rossa got going OK, with her sweet hull getting clear of the water occasionally and not looking very sticky in a light patch of breeze. INEOS Team UK looked much the same as the ACWS - when the wind was light - she seemed very sticky. Once foiling, she looked fast - and that is maybe the British conundrum.
American Magic looked great when she caught enough breeze to get foiling with her J1, and super-dead when there was not.
It seems that all teams now have to make a choice - either leave the Code Zero off the boat and accept that if they drop off the foils in light winds, it could cost them races.
Or they get the Code Zero to work, in a way that gives the crew some options if the breeze goes light and get wins on the leaderboard.
Obviously from the video above Luna Rossa has progressed down the FR0 path, and tacks quite easily with it. But no-one had the courage to make the call for the FR0 in any of the Practice Racing, preferring to stay with their J1's or smaller. The interesting aspect of the team-think is that they see to rig for a mid-forecast situation - and if the breeze drops below that level, then they take the hit along with all the other competitors who have opted for the same setup.
Conventional wisdom has it that you rig for the minimum expected condition, and work out how to dump/live with the excess power. With races being only 25 minutes long - no doubt the teams believe that the breeze will hold for the 25 minutes, plus the 9 minute countdown, plus 10 minutes on top of that to allow for headsail set up from bareheaded.
However as we have seen on several occasions, the wind has dropped once the minimum limit of 6.5kts (averaged over 30secs) has not been reached between the ninth and fourth minutes of the start countdown. And as was seen in Race 12 of the ACWS Emirates Team NZ was able to turn an 800 metre deficit into a 300 metre leg on a 2500 metre leg, by being able to foil earlier and sail a deeper course than their opponent Luna Rossa.
Considered by apparently discarded
Our nagging impression, amongst the Challengers, is that there is some Group-think that says the Code Zero is too hard, they have other, more immediate, options to address.
The other nagging impression is the campaigns are becoming boffin-led, as they search for elusive boat-speed, and often there is over-thinking on fundamental issues.
Of course, such a scenario has, in the past, played directly into the hands of Emirates Team New Zealand - renowned for being able to devise a unique solution to a fundamental issue, which proves to the winning point of difference.
We saw that in the last America's Cup on several occasions - most notably with the use of cyclors - a concept which the other teams claimed they had all explored and discounted.
The increase in efficiency allowed the New Zealanders to carry two instead of three accumulators in the boat - saving weight that could be better spent elsewhere. And there were numerous other advantages.
Other innovations were the addition of the rudder gantry on their only test boat - extending the AC45 to an AC50 and giving the Kiwis a march of six months on the other teams who didn't get into an AC50 until late February 2017. But a couple of teams had up to four test AC45's in the meantime.
There were also the light weather foils which had a higher wind range than the other teams.
The big difference between the Challengers and the Defenders is that the New Zealanders have the time to refine a Code Zero, which is already part-developed. The Challengers meantime have a Challenger Selection Series to worry about - and their preparation should now be one of refinement rather than major development.
But the lesson from the weekend is that the development of maximum power in the light will have a big payoff on the result sheet, and there are some difficult judgement calls to be made.