After the first AC75 racing we saw in the America’s Cup cycle, the British team looked to be in trouble with an uncompetitive boat. But since the start of the Prada Cup there have clearly been some big changes made to INEOS Team UK’s boat which have turned their fortunes around and the Brits have yet to lose any of their opening four Prada Cup races.  

The question is how has Ben Ainslie’s team achieved this incredible turnaround in such a short time? Some even wondered if the Brits had been sandbagging (deliberately sailing their boat slowly) in order to throw off the opposition – a not unheard of concept in the history of the America’s Cup, though something that is usually more rumour than fact. Ainslie himself laughed off the suggestion in a press conference – it would certainly be a high risk strategy whilst trying to reassure your backer that their £110m+ investment is worth continuing with. 

What did the British America’s Cup team need to fix?

INEOS Team UK’s boat, Britannia, was not just slightly slower than all the other teams in the America’s Cup World Series, it looked to be significantly slower around the course, struggled to get on the foils as early as the other teams, and needed more power (a bigger headsail) to do so. 

Foil control was clearly an issue, and Britannia experienced unscheduled crash downs in her early racing. The following battle of words with ETNZ about whether that was the fault of the supplied foil control software was far from edifying. How this was resolved – whether by ETNZ or INEOS or Mercedes F1 (a significant technical partner of the British team) – is unclear, but it doesn’t seem to be an issue at the moment. A good thing too, as the problems did suggest a scary loss of control.

In the early racing we saw from all the teams, it was plain to see the British boat spent longer with both foils down during their tacks and gybes than any other team and lost significant distance due to this. During the live broadcast this point was picked up several times by all the commentators.

A hint at the future?  

The Brits left the America’s Cup World Series in December 2020 without a win and with a great deal of work to do on a boat that was slower, by some large margins, around the racecourse than any other team. However, there were some positives. 

The British recorded the top boatspeed and were regularly competitive in a straight line when windspeeds were similar. This indicates they had not gone down a design blind alley, only that their manoeuvres were the main source of their woes. 

Identifying the elements of your boat that need to be refined is a relatively easy task. Working out how to improve things without compromising other areas of performance is the difficult part. 

When Ainslie was asked what work his British America’s Cup team had done to the boat ahead of the first weekend of the Prada Cup, he gave some clues to the extent of the changes, saying: “The team has been working flat out since the World Series and we think we have improved a lot from where we were.

“We have brought a lot of new parts online including a new rudder, new rudder elevator, new mast, new mainsail, and new headsails. Then alongside that we have made modifications to our foils, to the aero package on our hull and we have changed the systems inside the hull. We knew our development from the World Series would have to be significant and we have certainly been busy.”

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This could be viewed in the context of a team who were in trouble making wholesale changes, and it’s clear the Brits worked enormously hard in between the ACWS and Prada Cup start (reportedly 24 hours a day every day – though they were generously allowed Christmas day off). However, this is less an indication that everything was wrong about Britannia, and more an indication of just how interconnected every component of an AC75 is. You cannot make one significant change to anything without changing a lot of other things in response.  

How did the British America’s Cup team improve? 

The exact details about what has been done to develop Brittania into a race winning boat are hard to discern – and Ainslie and co. will certainly be at pains to keep as much a secret as possible because this development race is far from over. But there are a number of observations we can make that hint at some answers.

One of the big giveaways came in Shirley Robertson‘s commentary on day one of Prada Cup racing, when she revealed that British team’s foils had previously been taking on water. To the casual observer the INEOS foils did previously seem to be creating a larger rooster tail than, for example Luna Rossa Prada Pirelli’s, but now it seems that they were in fact leaking – Robertson described the previous problem as ‘like dragging a bucket around the course’.

It’s well documented that the UK team had used up their foil allocation (each team can make 6 individual foils – or 3 pairs – from launch of their first AC75 to the final of the America’s Cup) and so could not deploy a new set of foils for the Prada Cup, only a modified set, with modifications limited to 20% total mass.

Clearly the team has worked hard on their foil shape and development. The foils are subtly different in terms of their outright shape with clear changes in both the tip shape, overall size and there is a new (or at least bigger) bulge sitting beneath the main foil arm where they two wings connect. They have also been smoothed out much more, where the surface previously showed sections that were not entirely fared. 

Without access to some serious computing power and Computational Fluid Dynamics (CFD) programmes it’s difficult to make an assessment of exactly what these tweaks aim to rectify. However, we can see the team have absolutely made changes and these will will have been led by the knowledge that they were already fast but not providing enough lift in the manoeuvres. 

Sail Trim 

The mainsail seems to be a key area of development and is a relatively new concept. The 2017 America’s Cup catamarans sported large wingsails, which are very efficient, but impossible to drop without a crane and require a lot of people to handle them ashore. 

The AC75 has a mainsail that actually consists of two sails set on the back of a D-Shaped mast tube. Each sail is connected to one corner of the D-shaped mast to create a ‘soft wing’ sail. Within the sails there is a great deal of scope for the teams to add their own proprietary control systems, particularly at the head and the foot of the sail. As such, they have been a significant area of development for all teams, though much of this development is in the form of controls hidden between the two sail skins. 

There is a significant change to Brittania in this area. Previously, the Brits had a boom which articulated in the middle section. This was clearly designed to provide depth to the sail very low down, which they presumably felt was needed to create enough power to get the boat onto the foils. 

Once these boats are foiling, the apparent wind moves forwards rapidly so they typically require a relatively flat sail even when heading downwind. However, with no keel beneath the hull, when the boat is not foiling it has very little righting moment to keep the boat upright. A deeper sail means you can generate more power down low, which causes the boat to tip over less than a sail which is flatter and so needs a more even distribution of power from head to foot. 

Teams have gone in two different directions with regards to their boom setup. Both Emirates Team New Zealand and Luna Rossa Prada Pirelli have, essentially, gone for a setup which has no boom, controlling the shape of the sail with a series of hydraulic rams and complex control systems hidden between the two skins.

American Magic and INEOS Team UK have both gone for a more traditional boom between the two sail skins. In theory a boom allows for much more control over the sail, but no boom makes it easier to generate significant depth in the lower part of the sail. 

During the racing in Prada Cup so far, we have seen Brittania sailing without this articulating boom (although it could feasibly be the same boom with the articulation locked). The effect of this – if you watch the team closely through tacks and gybes – is that through the manoeuvres, the mainsail sets on the new tack or gybe much quicker. The articulated boom seemed to take longer to go from camber in one direction to camber in another. With the new boom system, the team are able to start generating power on the new tack quicker and so suffer much less speed loss through the manoeuvre. 

Aerodynamics

The British America’s Cup team are the only team to have sideways facing grinders and there are fewer members of the crew grinding. Britannia has only six grinders, where most of the other teams have eight. Each of these grinders uses their own, dedicated, grinding pedestal too, while on the other boats they typically have two crew members per pedestal.

To the layman’s eye, the sideways facing grinders look woefully unaerodynamic – no creature in nature turns sideways to make themselves more streamlined (apart from possibly a sunfish) and the crew’s helmets were clearly visible higher up than on other teams. 

This point was raised by many commentators when the team were not performing as they had hoped, but with hindsight, this appears less of an issue. Now the team have sorted their troubles elsewhere it has slowly become clear that their grinder arrangement has built in some potential advantages that can be capitalised upon now the British team is competitive in other aspects of their boat. 

There are possible benefits to having one sailor on each pedestal – both in terms of power transfer and cadence. It is much more effective for a human to grind ‘forwards’ rather than ‘backwards’ so despite having fewer grinders than the other teams INEOS may yet generate more power output than other teams. 

Certainly there have been plenty of rumours that individually the British grinders push out the biggest numbers of any teams, and having sailors like Olympic rower Matt Gotrel and man mountain Chris Brittle make it clear why.

 The reduced number of grinders has also allowed the British America’s Cup team to free up Giles Scott to operate as a dedicated tactician. Other teams have, so far, split the tactician role with another job – American Magic has Terry Hutchinson on tactics but also grinding at a pedestal, while Luna Rossa has gone for two helms, one on each side, who alternate tactical and helming roles from tack to tack. So far in the tight racing scenarios we have seen, this has been a boon for the British team. 

Ultimately it seems the British team has taken a minor aero hit in order to give themselves other tactical advantages. This was not obvious when they were slow as no tactician will win an event in a slower boat. Being able to out-match-race other teams is not something we expected to be a deciding factor this early on, but it is clearly going to become increasingly important going through the series.

How the British America’s Cup team changed crew movement  

There is one, final obvious change from the ACWS to the Prada Cup, how the crew cross the boat. 

It might seem a small change, the choreography of the helmsman, tactician and mainsail trimmer in each manoeuvre, but it probably points to a fundamental change the team have made – or possibly is the result of the fundamental changes.

During the World Series as the team set up for a tack, Giles Scott, the tactician would cross the boat before the manoeuvre, Ainslie the skipper would then steer the boat through the turn and, once through the turn both he and Belddyn Mon (mainsail trimmer) would cross the boat to the new side, while Scott took the wheel until Ainslie had crossed. 

During the Prada Cup, however, both Scott and Mon cross the boat ahead of the tack or gybe, while Ainslie still crosses after. Presumably the team had identified they were too slow getting the mainsail powered up once on the new tack and have taken steps to rectify this with both the new boom / mainsail arrangement and by switching the mainsail timer to the new side early, allowing him better sight of the sail and – crucially – having him at the controls in the key seconds when the tack has been completed and they are trying to develop power quickly as the foil is lifted.  

These are only the changes we have seen so far from the British America’s Cup team, but they have certainly been positive ones. However, all teams will continue development right up until the moment the America’s Cup final is concluded. If the Brits can make such gains, it is reasonable to assume everyone can.

What else might be waiting up the sleeves of Ainslie and co.? We can’t wait to find out!

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