Toby Heppell looks at the design decisions taken by INEOS Team UK in the build up to the America's Cup and asks where the Brits got it right and where they got it wrong

Mere days before the Prada Cup Final to select one of either INEOS Team UK or Luna Rossa Prada Pirelli as the team to take on Emirates Team New Zealand in the America’s Cup, the world held their breath in anticipation of what looked likely to be an extremely close-fought competition.

Indeed the final race of the Prada Cup Round Robin series between the two teams had seen a battle royale between the British and Italian teams and was easily the most exciting race in AC75s to date.

For all the hype and hope, the resulting series was something of a let down with Luna Rossa Prada Pirelli winning emphatically by 7 wins to INEOS Team UK’s 1. So where did it go wrong for the Brits?

Start of the America’s Cup cycle

To fully answer this we have to go back to a time before Covid-19, lockdown, and PPE were all in the public lexicon; the launch of the teams’ first AC75s.

It is a phrase so well worn in the America’s Cup as to be cliche, but ‘the one thing you can’t buy is time’ saying is worth heeding. As Defender of the America’s Cup, Emirates Team New Zealand were able to design an entirely new class of boat for this America’s Cup alongside their Challenger of Record, Luna Rossa Prada Pirelli.

As such, both teams got a jump on the competition in terms of feeding the design concept into computer simulations to get a better understanding of the performance characteristics of the design, and to compare different design concepts against one another.

It’s worth mentioning, this advantage should not be considered unfair. The America’s Cup is a unique event and the Defender and Challenger of Record always hold an advantage – the Defender a significant one. That is the nature of the Cup and is something all teams know to be the case when entering. It is part of the reason it is such an enduring and engrossing contest – at times both on the water and in the courts.

INEOS’ first AC75 featured a flat hull. Photo Mark Lloyd / Lloyd Images

That the two other challengers (INEOS Team UK and American Magic) produced initial AC75s with flat hulls and both Emirates Team New Zealand and Luna Rossa produced hulls that featured some form of skeg/bustle shows how much further they were down the development path than the others.

By the time the second AC75s were launched they all featured this pronounced skeg to one degree or another, with INEOS Team UK’s being the largest and most angular of the fleet. That INEOS’ second hull was so drastically different shows they took something of a clean sheet of paper approach in designing their second AC75.

This second hull was a bold and radical step. But it also implies the team were not yet following an incremental development path.

INEOS launched a very different boat 2.

As for Luna Rossa Prada Pirelli their hull shape was visually very similar to the first AC75 they launched indicating they were pleased with their initial design and it had vindicated their simulation numbers on the water. In fact, the Italians’ second boat is the most similar to their first attempt of all the other teams.

Mainsail Setup

So radical are the latest iteration of America’s Cup boat, that almost every component on them is essentially new and untested. This is true in terms of hull shape, foils and the sails, particularly the mainsail.

There are plenty of previous examples of soft wing sails, which attempt to replicate some of the efficiency of solid wing sails without some of the key drawbacks – wings require craning onto and off the boats, cannot be removed at sea if a boat needs to be towed home, and are usually severely damage by any capsize.

In the context of an AC75, the two-skinned, soft wing concept, on a D shaped carbon mast, needs to generate a great deal of power early on to get the boat onto it’s foil. It also needs to be able to be extremely flat when the boats are sailing upwind on their foil – generating around 50 knots of windspeed once apparent windspeed is factored in. Additionally the mainsail needs to transition from one profile shape to the other incredibly dynamically, as the moment the boat is onto its foils the requirements of the sail change rapidly.

Initially there is a need for a lot of power down low, to prevent heeling moment on a boat without a keel. Next, when the boat is up on her foils, righting moment increases massively and very quickly, at which point the sail needs to develop a lot of power from head to foot. Finally as the AC75s reach speeds of 30 knots upwind, the sail will need to start flattening and then shedding power in a low drag, aerodynamically efficient fashion.

The masts might all be one design, there are sail size rules to comply with, and controls to force shape into the sails are limited to the top couple of metres of the sail and the bottom few metres, but beyond that there is plenty of scope for development.

Luna Rossa’s very clean boomless setup. Photo: Borlenghi Studio / COR36

Again when we compare Luna Rossa Prada Pirelli with INEOS Team UK we see a relatively stable development path from the Italian team as compared to a development path from the Brits that moves from concept to concept.

Luna Rossa’s first boat was launched with a boomless setup, which allowed the sail to neatly sit at deck level, cleaning up aerodynamic efficiency and allowing for significant depth in the bottom few metres of the sail.

This concept has been retained for the second iteration of the Italian’s AC75. INEOS Team UK also launched their first America’s Cup boat with a boomless setup, though it was not as refined as the Italian approach, which appears to have a solid device not dissimilar to a boom and traveller underneath the deck to help transfer loads though the hull in a traditional way, but keeping the depth in the sail above deck when needed and a clean, aerodynamically efficient foot.

It seems the Brit’s first attempt was to use something akin to a very stiff (presumably controllable by some mechanism between the two skins) pair of battens in the lower part of the sail, which was later filled in with a skirt of sorts to get rid of the gap between sail and deck.

The Brits first boat had a boomless setup at first

The Brits then moved away from this idea – presumably their data did not show it to be quick or they felt the development time needed could be better spent elsewhere.

When the British second boat was launched, she arrived with a solid boom – the Americans had had a solid boom from the start. This boom on the Brits second boat was able to articulate along its length, theoretically representing something of a compromise – a solid boom, that could bend to get shape into the foot. Emirates Team New Zealand had something similar on their first boat.

Later, following their dismal showing at the America’s Cup World Series, the Brits made a significant number of changes to their boat, including getting rid of the articulation and settling for a solid boom with no articulation, and accepting they would be unable to get the depth into the foot of their sail that Luna Rossa (and New Zealand who went to a boomless setup for their second boat) could.

The final, solid boom solution for INEOS Team UK. Photo: Borlenghi Studio / COR36

Once again this shows us how far behind the Brits and probably Americans were in terms of their development. Luna Rossa came out of the shed on day one with an impressive, well worked, boomless setup that must be the work of a great deal of study, development and expense.

Emirates Team New Zealand launched with a boom that had significant articulation and developed this concept of allowing depth in the foot of their sail into a boomless setup for their second boat.

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The Brits launched with a boomless setup, developed it slightly, went in an entirely different direction and finally ended up with something else altogether.

Foils still a work in progress for the America’s Cup

From the moment the AC75 rule was announced it was clear that foils were going to be a key factor. Not simply because these boats are designed to spend most of their time on the foils, but because the limitations on foil numbers are so stringent.

For the AC75s in the 36th America’s Cup, each team is limited to six individual foils, making three pairs total across both of their boats.

They are able to modify these foils to a degree (up to 20% of their mass may be modified) and they are able to build a greater number of flaps on the foils, which control how much lift you can generate. Broadly, however, these numbers seriously hindered development opportunities.

Most teams took a similar path. When the first AC75s were launched they all had a different foil on either side of the boat, meaning teams could get data on a couple of different design paths, presumably with an aim to selecting the best options and refining that design over the next few foils before settling on a final design for the last set, which could then be modified slightly should they need further refining.

Emirates Team New Zealand launch their first boat with a T foil and a Y foil.

That the final set of foils for each of the teams are still significantly different to each other shows how much scope there likely remains in terms of development in this area.

All teams have experimented with different foil shapes and sections, and there remains no clear direction that offers a significant advantage – though Emirates Team New Zealand now have foils that are probably furthest from the three other boats in terms of their size and shape, being smaller and the closest to fully flat wings (a T shape) than the others. Most teams settled on some form of anhedral wing (a Y shape).

The Brits produced one of the most experimental foils we have seen in a W shape which makes the most of the rule which requires the foils to fit into a rectangular shape. This W foil provides a larger amount of foil than any other shape within the confines of the measurement box.

The Brits’ W foil is an engineering marvel

Looking at the images released of the foil being built (done alongside one of the team’s partners, the Mercedes F1 team) it appears this foil features some impressive rule workarounds. The rules state that each foil must have two flaps on it, one on each wing, either side of the foil arm. The W foil manages to extend both flaps the full length of the foil wing, despite the wing being bent.

The foil also looks to be able to manipulate the flap so that for a single input on the flap control, the inner section of the flap will move more while the flap at the tips will move less. In theory this could provide better control in a more hydrodynamically efficient package.

Ultimately, though INEOS was still testing this design up to the America’s Cup World Series (they had a W foil on one side of the boat and what became their final Y foil on the other in the run up to the series), they abandoned the concept.

It is a clever concept and is the product of some impressive engineering, and it might yet be the best solution, but it also looks to be a concept that could churn though development time very quickly. Whether the team dropped the concept because they ran out of time to develop it, or it simply proved to be slow is hard to tell. But having produced a pair of launch foils with prominent bulbs, then a pair of complex W foils and finally a pair of Y foils, once again their development path looks far from smooth.

INEOS focus on sailing

A route the British team did take, which has served them well, was to go with a traditional tactician and helmsman role in Giles Scott and Ben Ainslie. They have done this by sacrificing some grinders. Where other teams have four grinders per side, the Brits have three.

It seems that the British team have never struggled for power so that they managed to output the same if not more – rumours are the British team’s grinders were putting out more wattage than all of the other teams – might indicate they have spend development in this area.

Three grinders on INEOS all have a dedicated set of handles

The Brits opted for a single grinder pedestal per grinder whereas other teams are using two people per pedestal. There are 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 generate more power output than other teams.

Certainly on the shifty courses, the ability to have fewer people spinning the handles and more people with their head out the boat has been a boon. But, as we saw in the Prada Cup Final, if you are up against a demonstrably quicker boat, decision making will only get you so far, and, at times, in the Final the Brits made the sort of rash calls in the pre-start that come from being under pressure to win a start at all costs.

What to make of the British America’s Cup effort?

Fans of INEOS Team UK will naturally be disappointed with their failure to make it through to the America’s Cup itself. It would be easy to look at what has been written here as a slight on the team’s development process.

However, looking at their effort for this America’s Cup it is hard to fault many decisions made at the time. They started the cycle behind both Luna Rossa Prada Pirelli and Emirates Team New Zealand and must have known when they trained against the Italians in Cagliari in late 2019 that they were well behind the curve.

From there, the decision to radically change their boat design must have been made and we saw them fit a small skeg to their first AC75, a clear acknowledgement this was the path to take.

That their second hull was so different to their first represents a team that was willing to accept their mistakes and move on and keep faith with their design team.

A conservative approach to design is not going to win the America’s Cup, so the radical W foils were a good concept, built alongside people that really know what they are doing in mechanical engineering terms (Mercedes F1). As mentioned the foils are clearly an area every team is still exploring and there is plenty of development left on the table in this area.

It’s not clear that the Brits ever fully got to grips with the softwing sail and may have just decided their development time was best spent elsewhere.

We can’t know how much the Covid-19 lockdowns affected the development path of the teams and each will have been hampered to a different degree. However, it must be the case that if you start out behind some teams in terms of development time, any further lost time to all teams, is going to affect you more.

Ultimately in Luna Rossa, they came up against a team who have been fighting for the America’s Cup since 2000. Fighting to win the America’s Cup is a long term game and, should the Brits race again in an AC75 (if they’re kept for the next cup), they should be in a very strong position.

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