American Magic’s AC75 Patriot glides through the water near Pensacola, Florida, and as it picks up speed with the day’s favorable winds, the imposing dark hull rises from the water and begins to plane on its hydrofoils. Crouched near the bow, pedaling furiously, John Croom is lashed by spray. His earpiece crackles with chatter from the rest of the crew. He has watched videos of America’s Cup boats. He’s logged hundreds of hours of training on land. But this is his first time—his first time on any sailboat.

“Still to this day, that’s one of the most euphoric moments I’ve ever had in my career,” Croom says. “Getting the opportunity to sail, and then just feeling that actual takeoff and being on the foils was something super special. That was the day I fell in love with it.”

While some of sailing’s traditionalists bristle at the inclusion of cyclors in lieu of grinders on America’s Cup boats, there’s no turning back now. The technology will be found on every boat in the 2024 America’s Cup.

This novel power-delivery method has opened the door for newcomers like Croom to hop aboard, like throwing a ­drivers-ed student into a Formula 1. It has also led to a revolution in the way America’s Cup teams recruit talent, hone their physiological training, and use cycling know-how to power the AC75’s hydraulic controls.

“We’re finding that cyclors bring much more power to the table,” says Ben Day, American Magic’s performance lead. “Cycling uses much bigger muscle groups; therefore, they can produce more power than arm grinders. And with the new AC75 regulations of reducing crew numbers (eight sailors total), we need to find that power in other ways. So, most teams are looking at cyclors at this stage. Glutes, quads and hamstrings can produce more explosive power and more power for a longer sustained period.”

Day is another example of someone outside the sailing establishment who quickly entered American Magic’s inner circle. Day had a 12-year career as a professional cyclist, racing primarily in North America. Once he retired from racing, the Australian started Day by Day Coaching out of his adopted hometown of Boulder, Colorado.

Not surprisingly, Day and American Magic looked to the cycling world to find athletes to fill their “power teams.” The team had preliminary conversations with Kiel Reijnen, a professional rider who spent six years in cycling’s WorldTour, racing the sport’s premier events, such as the Tour of Spain, Tour of Flanders, and multiple UCI World Championships.

“We focused on leg-­dominant power sports, with similar activities that would fit the needs for racing on the boat,” says Day of the recruitment process. “We have taken time to examine a whole list of athletes that might fit the bill, and then have reached out to consider interest.”

It wasn’t as simple as assembling a bench of top cyclists. The rule book states the combined weight of the eight-person crew must be between 680 and 700 kilograms. Split evenly, that means each person should be between 85 and 87.5 kilograms. Reijnen weighs 65 kilograms. It’s rare to find a pro cyclist that weighs more than 80 kilograms because power-to-weight ratio in cycling rules all. Cyclists can control both variables in the power-to-weight equation. Training can boost power output, measured in watts. They can also lose weight to improve their power-to-weight ratio. Naturally, any given rider has limits for both variables. The best professionals are extremely efficient in their power production and astonishingly lean. It would be a tall order for someone like Reijnen to gain 20 kilograms without compromising their power output.

Croom is uniquely suited to the challenge, having found cycling late in life after playing football in his younger years and at times weighing close to 136 kilograms. Though he slimmed down to about 90, he’d never be suited for road cycling. Track cycling, on the other hand, was a good fit. Since track events are held on a flat, 250-meter track, weight can be sacrificed at the expense of raw power.

Ashton Lambie is another hopeful on American Magic’s power team who never quite fit cycling’s mold. This mustachioed Nebraskan holds the record for the fastest ride across the state of Kansas. He’s also the only human to ever ride the 4 km track pursuit event in under four minutes.

The riders you might see on television at the Tour de France are not going to be aboard an AC75 in Barcelona. Similarly, the athletes who have been recruited to pedal the cyclors aren’t ready to ride on day one, despite their extensive backgrounds in cycling. Intense training is underway to prepare them for the demands of an America’s Cup race.

“There are periods where we spend time focusing more on endurance or strength development,” Day says. “At other times, we’re working more around the high-intensity phases.”

While American Magic has been mum about the specifics of the training and the AC75’s power demands, Croom has posted many of his recent workouts and training rides on Strava, an online activity tracker.

Croom has done extensive endurance work, already logging weekly rides longer than 80 miles in January. He’s also been completing viciously intense interval workouts to build his body’s tolerance for maximum efforts. For example, he was able to hold 371 watts for 20 minutes in one such workout. Simply a statistic, right? I’ve been racing bikes for the last 25 years, and at my best, I can hold 302 watts for 20 minutes. Someone without training or experience would do well to maintain just half of Croom’s wattage.

While the training and performance of these new crewmembers are opaque, the technical details of the AC75 are practically impenetrable. American Magic’s spokespeople and crew did not answer specific questions about how the hydraulic power system works, but what we do know is that the boat has a hydraulic accumulator tank, which stores pressure generated by the cyclors. The crew uses a hydraulic actuator to convert the tank’s pressure into force, which in turn powers the boat’s controls. Any time the boat needs to tack, jibe or simply trim a sail, power is needed.

Sources indicate that the hydraulic accumulator results in a very unusual feel at the pedals for the power team. It’s also believed that as the tank gets full, the effort to add more pressure to the accumulator becomes harder.

“We can change the different inputs to the system,” James Wright, of the American Magic power team, told the America’s Cup Recon Unit, which monitors and reports on the team’s developments. “The different power demands necessitate different inputs from us on our side. The system kind of auto-adjusts depending on the demands from the sails and, of course, what we can give it.”

It’s easy to imagine how the team might strategize its efforts, given the intensity of a 20- to 30-minute America’s Cup race and the essentially limitless power demands of the boat. They might attempt to keep the tank as low as possible with steady, moderate pedaling, and then fill it as fast as possible with maximum effort ahead of a demanding maneuver like a tack. Perhaps some of the four riders would be specifically reserved for all-out efforts to fill the tank on demand, while others would ride steadily to feed power to minor adjustments.

Whatever the strategy, it is clear that the entire crew needs to be in lock-step during a race. “When we talk about the sailing team, we consider the power team part of a sailing team; they have to work in cohesion,” Day says. “The afterguard will request efforts from the guys as they trim the boat, and they’ll learn what they can deliver in terms of power. And the guys will give it their all to deliver what’s asked of them. So, there must be solid cohesion between the two groups; ultimately, we are one team.”

Clearly, the sailors, engineers and coaches are working furiously to optimize the use of the cyclors. There is another area of the sport that has some catching up to do, and that is World Cycling’s anti-doping controls. Even the casual cycling fan is aware that performance-­enhancing drugs have long tarnished the sport’s reputation. Given the massive physiological demands placed on the AC75’s power team, the sport’s governing body, World Sailing, would be wise to heed the lessons of cycling’s past.

In the wake of a major doping scandal about 10 years ago, cycling began rigorously testing athletes out of competition because it was found riders could achieve huge performance gains by doping for training and then cleaning up in time for in-competition controls at races. It stands to reason that this is a major liability for the America’s Cup, given the amount of run-up that the teams have to train for the 2024 event.

Although World Sailing conducted 186 in-competition tests between 2020 and 2022, including anti-doping ­controls at the last America’s Cup, it did not conduct any out-of-­competition controls during those three years. To ramp up efforts for the 2024 Cup, World Sailing brought on Vasi Naidoo as its director of legal and governance. Naidoo has experience with anti-doping efforts at the Olympics and Commonwealth Games, and she served on the Ethics Commission at the UCI, cycling’s international governing body. World Sailing confirmed that there will be out-of-­competition anti-doping tests in 2023, and the testing will include America’s Cup athletes.

Fortunately, on the whole, the interplay between cycling and sailing—two unlikely ­bedfellows—has resulted in a fascinating exchange of technology and science. “The transition to cyclors allows a tech-forward, applied-­sciences sport to pull in a completely separate sport and borrow technology from it,” says Reijnen, who himself is an accomplished sailor, having finished the WA360 event sailed out of Port Townsend, Washington, in 2021. “What does sailing borrow from cycling, but what does cycling then borrow from sailing?”

Even at the person-to-person level, this exchange of information and experiences has been rapid and, in fact, quite cordial.

“The coolest part about being part of this team is that I came into this group of sailors so new and so green,” Croom says. “And they were super-­welcoming, understanding, and trying to get me to learn as quickly as possible. Like, any questions I had, there was no such thing as a dumb question, and that was something special.”

The post The Cyclors of American Magic appeared first on Sailing World.

Whether you’re for or against the new America’s Cup-class yachts, we can all agree that the massive lifting foils and wings have everyone’s attention. But another thing we can agree upon is that the AC75 is still a sailboat powered by the wind. If the sails aren’t fast, then a team will need to find a substantial advantage somewhere else to have any chance of hoisting the Cup aloft next March. So, in the spirit of the belief that “everything changes and everything stays the same,” the new technology we should be talking about this time around is the sails, what the inside techies refer to as the “aero package.”

The core of the AC75′s sail plan is the rotating ­soft-wing sail, comprised of two sails—or “skins”—of a double-sided mainsail that must be attached to each of the two aft edges of a D-section spar. The AC75 class rules that control all the components of the sail plan have the same mixed approach as the rest of the boat. There are supplied one-design parts, and then there’s wide latitude for innovation.

“The idea of the class rules is to have all the teams sailing with a similar mast but to let them be free to work on sails and control systems,” says Luna Rossa Prada Pirelli’s mainsail ­trimmer, Pietro Sibello. “The spar is dictated by a minimum scantling rule. Starting from the same laminate provided by the rule, we are allowed to reinforce it within known tolerances. By doing so, every team is responsible for the structure of their own mast.”

Standing rigging is supplied equipment as well and is the same for everybody, with that portion constituting a single set of spreaders and running backstays. Beyond supplied elements of spar and rigging, development is rampant and closely guarded—especially the shape-forcing components hidden between the skins. “For the sails, there are tolerances to make sure the boats on the starting line look like they are competing in the same class,” Sibello says, “but there is room to play with area, structure, geometry, shape and batten layout. And this is where the control systems are more open—in the lower zone and the upper zone we are allowed to have active control systems.”

This is where it gets interesting. There are no limitations in these two zones—­identified by the class rule as the top 4 meters and the bottom 1.5 meters of the sail plan—where the only boundaries are set by the laws of physics and the cost.

The playing field is not short of either challenges or opportunities, but the first problem was to figure out what was the real nature of the problem. “This concept has been around for a really long time,” says Andrew Gaynor, a five-time Cup veteran, and now part of American Magic’s spar design team.

“I believe a patent was actually filed by L. Francis Herreshoff in 1920-something describing a twin-skin setup, [but] somewhere along the line, this idea always disappeared. Like, you don’t see this thing every day now. So at some point, all of these concepts have failed. Was this because of a material-science thing or is there some other fundamental flaw?

“So that’s an easy place to start trying to understand this thing. And then you’re like, well, what’s the goal? Is this thing a more refined, soft sail that everyone’s familiar with? Or is it another way of achieving the rigid wing that we’ve seen in the past couple of Cup cycles?”

Is it a rabbit or is it a hare? Time was the one thing that everyone needed to figure it out, particularly time on the water. Unfortunately, even before COVID-19 turned everyone’s world upside down, there was never going to be enough of it. The good news was that the onward march of technology had enabled an alternative: computer simulation.

“The struggle is to identify and properly model the physics of these twin skins,” Gaynor says. “There’s the way the two sails interact with each other and the way the air interacts around them. It’s not a rigid wing like we’ve been used to, and in the same respect, it’s not a single sail for which many mainsail design tools have been built over many years now. So it’s about developing a whole new set of tools to properly analyze this new setup. What we’re seeing more and more in this Cup is that modeling is king. If you can nail your model and nail it early, then it’s a huge advantage because of the time it requires to build and test something in real life,” Gaynor adds.

North Sails is building sails for Emirates Team New Zealand, Luna Rossa Prada Pirelli and INEOS Team UK. JB Braun, North’s ­director of design and engineering, has been the man in the hottest seat. “We didn’t really have any good tools for double-surface sails at that time,” Braun says. “Our North Design Suite wasn’t oriented to develop or analyze a double-surface main. So when the rule was being created, we committed our resources to developing our fluid structure interaction codes to allow us to analyze these sails, creating the powerful suite of tools we enjoy today. We incorporated the ability to add the two control arms, and have a D-section mast and two sails coming off that,” as specified in the AC75 rule.

The design tools are intended to simulate a sail’s performance by ­calculating how the initial shape changes under pressure applied by the wind, creating the flying shape. This process uses Fluid Structure Interaction software, and it pretty much does what it says on the tin: calculating how the sail structure is ­modified by its interaction with the fluid. Once the flying shape is calculated by the FSI code, the next stage is to use computational fluid dynamics programs to calculate the amount of force generated by the sail plan. Sometimes it’s easier to visualize this force by describing it as a point (the center of effort) through which the force acts.

“That [force vector] is generated from changes in sail shape, and using the fluid structure interaction [software], you’d generate a data set,” Braun says. This is the first step in an iterative process. “I like talking about it as spinning the design wheel—you spin it once to get your ­baseline, and that’s one cycle.”

The results of that one cycle, Braun says, can lead designers in a specific direction. “It’s a balance. It’s not just about the aerodynamic efficiency; it’s about the balanced efficiency of the system, because as you lower and raise your center of effort in the sail and your sail plan, it changes the side force the foils are seeing. So changing the side force changes your leeway or the lift distribution on the foil, which changes the drag of the foil, which then changes how much drive force you need. Then the aerodynamic part of it needs to change to account for that change in drive. It’s a coupled solution. You can look at these things independently, but to come up with an answer or an optimal shape, it’s a coupled solution for aero- and hydrodynamic.”

Once the modeling produces a solution —a sail design that will generate the optimal force vector for the foils and hull—then the problem quickly becomes a matter of practical engineering. How do the teams control the two skins to achieve that shape, and trim it with the necessary speed to meet the dynamic demands of the boat?

RELATED: The Flying Technology of the AC75

“It comes down to the teams’ individual choices; when they rotate the wing mast, how they’re able to manage turning the two individual mainsails into what is fundamentally a high-pressure and low-pressure side of an asymmetric wing,” says Mike Sanderson, Doyle Sails CEO, a three-time Cup veteran, Volvo Ocean Race-winning skipper and former mainsail trimmer.

Like Braun, Sanderson is not personally involved with a team, but Doyle is supporting the American Magic challenge. It is a continuation of the collaboration with Quantum that was started back with American Magic team principal Hap Fauth’s Bella Mente, Sanderson says. It’s a joint collaboration and design, with the sails manufactured and built in Doyle’s New Zealand loft. “There are lots of problems in how you control getting the inside surface flat enough and the outside surface deep enough for it to be an efficient enough wing to justify the weight of ­having basically two mainsails up.”

The second skin is a lot of extra weight, and that’s an issue of which Gaynor is particularly conscious. “The weight allowances in the rule are pretty tight,” he says. “And keeping within your weight budget is made more difficult when you consider two mainsail skins, two sets of battens and all the associated hardware.”

If you are going to have two skins, they’d better be more efficient than a single one, and that means finding a way to make the windward surface flatter than the leeward surface. One of the principal tools for adjusting mainsail depth—mast bend—is denied to the sail trimmer because it affects both skins equally. Only tools that work on a single skin—like cunningham or outhaul —are useful.

“We’re not talking about two millimeters of luff curve here,” Sanderson adds. “We’re talking about pretty drastic depth changes between the inside and the outside to get the most efficient setup, and that’s what you see people battling with.”

It’s not the only problem, either—not by a long way. “How you deal with the whole area of connectivity of the wing, down to the deck, and the sealing of the endplate of the wing onto the deck [is another],” Sanderson says. An endplate uses a perpendicular surface at the end of an aero- or hydrofoil to prevent fluid flowing between the two sides of the foil and reducing the pressure difference. It also hinders the formation of a tip vortex, and both things improve efficiency. This is where the design of the lower mast zone will be important, creating an efficient endplate between the soft-wing sail and the deck, while still enabling effective ­control of the lower mainsail.

And then there is the upper mast zone. How they can control the twist will be a big driver of performance, Sanderson says. “It was quite well-documented how the Kiwis sailed in Bermuda [AC35] by using twist probably more than wing sheet, and that that was a more efficient and lower drag way of sailing those boats with the hard wing.

“Being able to react with the twist quickly enough [will be important]. And to be able to react with the depth, so it’s [inside] skin versus outside skin adjustment, versus traveler up and down, versus sheet on and off. The guys have got plenty going on as a wing trimmer. We’re seeing pretty much everyone using a PlayStation-style box, like Glenn Ashby was famously doing in Bermuda.”

Wing trimmer Pietro Sibello is well-aware of the complexities. “The fact that you can work on so many details, and you need more controls to model the shape of a soft sail in the different stages of the race, makes the game more challenging,” he says. “We have all been used to trimming the windward sail, but now we have a second sail to leeward, which is difficult to see and analyze, and that’s the most important of the two. On top of that, we have to think about what happens when we start to rotate the mast.”

It seems that even the simple things ­cannot be taken for granted. Telltales on the leeward skin cannot be seen by a wing trimmer to windward. Nothing about this is easy. “All the teams have been experimenting a lot,” Sibello says. “We have seen big and invasive control systems slowly getting simpler and lighter. It’s a matter of finding the best balance between control, aerodynamics, structure and weight.”

Both Gaynor and Sibello agree that ­diversity is the best way to find that balance. “We luckily have designers with different backgrounds and ages so that they can approach the challenge from a distinct point of view,” Sibello says.

“On our squad,” Gaynor says, “we have a bunch of people with lots of wing-trimming experience. And we have people with a lot of conventional sail-trimming experience. I think it’s good that we have this balance internally because I don’t think anybody’s figured out the right answer yet.”

The post The Sails of the America’s Cup appeared first on Sailing World.

Winged keels, Deed of Gift-controlled matches, rule changes, cheating allegations. The America’s Cup is no stranger to controversy, and for much of the past decade, the hot button has also been the new big thing: foiling. To traditionalists, this is heresy. The Cup is a yacht race, and sailing boats belong in the water. Others believe the Cup is a design, engineering and innovation contest that should be raced at the bleeding edge of technology. So is the modern AC75 the spiritual descendant of the 1903 ­superboat Reliance? Or should it go the way of the Seawanhaka Rule—collateral damage to Reliance’s one-sided victory? It may yet come to pass. No one knows what the 37th edition of the Cup will look like at this point, but whatever the future, the genie has soared out of the bottle: Foiling is now at the ­forefront of sailing.

It’s been one of those overnight ­successes that took a long while to come about: Italian Enrico Forlanini achieved 42.5 mph with a small, one-­person foiling powerboat just three years after Reliance’s win. The science is well-understood, at least in macro terms; hydrofoils use the same physics as sails and aircraft wings. They guide the flow of water around them, generating low pressure on one side and high pressure on the other. The resulting imbalance creates enough lifting force to get the boats up in the air, and that’s a lot quicker because the hull doesn’t have to push water out of the way anymore.

The original foiling Cup boat was the AC72 in the 34th America’s Cup in San Francisco. It was a Team New Zealand innovation, and they achieved it despite a class rule that was otherwise written to keep the boats in the water. The central innovation in 2012 was to shape the daggerboard into a foil that could provide both lift and leeway resistance. The next part of the challenge was to control the lift sufficiently well to enable stable flight. The rules controlling the AC72 forbid any part of the foil to move independently, so the New Zealanders couldn’t use flaps—an adjustable trailing edge that controls the amount of lift from aircraft wings. Instead, they moved the whole foil to change its angle of attack to the water. This has the same effect, varying the amount of lift ­generated. The AC50 that raced in the 35th Cup in Bermuda also forbid movable parts on the foils. In contrast, the AC75 is a new development because it ­specifically allows flaps on the two T-shaped foils, ­ushering in a new era in ­foiling Cup boats.

If we want to understand the challenges and opportunities presented by the foils of the AC75, then we first need to understand the rule. Nine-time Cup veteran Kurt Jordan, now structural engineering lead with the New York YC’s American Magic, explains: “In the rule terminology for the foils, we have the foil arm, which is the big, curved structural bit that comes out of the boat. And that is a one-design supplied part built by Persico. It’s compulsory that every team buys that; it has a hydro shape to it that you’re not allowed to alter. It’s kind of a rectangular shape with curved sides to create the hydro[dynamic] surface. The leading edge of that, the nose of that, is also a one-design part that comes assembled. And you’re not allowed to touch it. The trailing edge, which is anywhere from 300 to 500 mm long, is open for the teams to design and install.

“The foil arm comes down to a ­junction, and at the bottom of it is the foot. And from there down is where teams have freedom in design; in our terminology, we call that the foil wing. The foil wings must be symmetric about centerline. They have articulating flaps like an airplane. There’s also a very stringent weight and center-of-gravity rule for the foil package. As you design the wings, you need to be very cognizant to meet that center of gravity and weight.”

There are also geometric limitations on the foils, explains Nick Holroyd, chief designer with INEOS Team UK. “If you’re looking from the transom forward [the rule defines] a trapezium-shaped box. While ­longitudinally the foils also have to fit [in the space] between 10 and 12 meters ­forward of the transom. You have this 3D box that the foil has to fit within. The trapezium is about 4 meters across its base, and to some degree, that defines the maximum span the foil can have.”

The final restrictions are on the numbers of these parts that the teams are allowed to build. “The foil wings, you’re allowed to build only six of them, three sets,” Jordan says. “Then there is a rule that once you declare them, you’re allowed to modify [as many times as you want] up to 20 percent of the mass. It actually gives you quite a bit of freedom for significant changes to them.”

An Overview of the AC75

These restraints have led to teams making asymmetric sets of foils, so that within one pair, they can explore two different design avenues.

The whole T-shaped foil package is lifted in and out of the water by what’s called the foil-cant system, or FCS. “It’s another one-design part,” Jordan explains. “It’s a compulsory system that everybody has to use. It’s a big electrohydraulic system that does the cant of the foil arms. The [only] allowed movements of the foil arms are cant about a fore and aft axis. This system has a one-design battery to power it, so the power for canting the foils is not manpower.”

The teams use the same battery to ­control the foil wing flaps, even though this is a part that they can otherwise ­themselves design and build.

One-design parts have attracted their share of controversy in the past couple of years, and Jordan was deeply involved in the most serious of them. “The Challenger of Record Luna Rossa [Prada Pirelli] and the Defender [Emirates Team New Zealand] wrote the rule behind closed doors, and they divvied up responsibility for the one-design parts. Team New Zealand took on the responsibility of designing the foil-cant ­system, the hydraulic package. And Luna Rossa took on the design of the foil arms, the structural foil arm, which is a very ­critical part, as you can imagine.

“[Luna Rossa Prada Pirelli] pursued a method of construction that some of us have learned in the past doesn’t scale up to this size. The method of construction was basically a closed-mold composite structure. And there are a lot of foils built with that style of construction, like dagger­boards for IMOCA 60s. But we tried to build boards that way for the big Alinghi cat [AC33 in 2010]—we actually built 14 of them. Most of them were not successful, because as you scale it up, the thickness of the composites gets so great that a lot of the thermal stresses and things like that just start to become gremlins.”

Despite the warnings, Luna Rossa Prada Pirelli’s engineering team went ahead.

“They were pretty confident that they’d improved since what we learned in those days. So they built a test set, and a bunch of us went over to Persico for the first load test. It failed the load test, and at that stage they—kind of with open arms—embraced a consortium of engineers from all of the teams to create a working group who all collaborated on the design for what is now the foil arm. It was a painful start, and there were a lot of delays. We were delayed five months sailing our first boat because we didn’t have foils. It was controversial in that way, but they took on a very hard task.”

The new working group set to the ­problem and developed a new design that was also built by Persico. “The foil-arm ­construction is what we are calling ‘C-plate’ or carbon-plate-style construction, which consists of multiple long, contoured 20 mm plates stacked edgewise to create the structural backbone.” This version passed the structural tests and has now been sailing on the boats launched so far. “The confidence in them is super high at this stage,” Jordan says.

The final part of the jigsaw is the FCS, as Nick Holroyd explains: “The foil-cant ­system was designed by Team New Zealand, and it’s a good pointer for the future of the Cup. As of the 31st of August of this year, the final spec of the foil-cant system was issued, and any modifications or design improvements now need to be made unanimously.

“That’s forced the same group of four technical teams [who dealt with the foil-arm failure] to the table, and it’s been a very positive step because there are a number of technical issues still outstanding with the foil-cant system. It is prone to contamination within the hydraulic oil, and then that contamination undermines the reliability of the system. It’s in nobody’s interest—least of all the event’s—that there are races that are decided by the reliability of a supplied one-design ­system; that would be an awful outcome for the event.”

There isn’t much time left, with the opening races slated for Christmas, and the teams are all taking the problem seriously. “We’re only just a month past that [August] date, and we’re into having weekly meetings between all the teams, and there’s some really good work happening,” Holroyd says. “My takeaway from watching this Cup cycle is that we’ve produced far better results with all the stakeholders at the table.”

The various issues with the one-design parts have also proved a distraction from what should be the real work: ­designing the parts that the teams can control —the foil wings and their control systems or mechatronics.

“We are operating in a fluid that is 800 times denser than air, and so you end up with these foils that are quite small but—because of the fluid density and speeds you’re operating at—are capable of producing astronomical amounts of force,” Holroyd says. “If I’m designing a foil that will take off at 15 knots boatspeed, then it ­follows that it can produce enough lift for the boat and the crew; that’s seven and a half tons [of lift] at 15 knots. And I’m contemplating top speeds of, let’s say, 45 knots, so three times the speed. This means—because of the speed-squared term that occurs in all kinds of fluid dynamics—the maximum lift at 45 knots could be nine times the weight of the boat.”

And that would be nearly 77 tons of force being derived from those frail-looking flaps on the wings.

“The strength requirement—both for the structure of the wing itself, and the design and manufacture of flap-control systems [to fit] in such a very small space—to deal with those loads is quite tricky. The mechanical packaging side of these is a big deal.”

Jordan concurs: “You want an articulating flap that’s hydro or electric, or a combination system that controls the flap angle in salt water. And it deflects a lot. It’s just a huge mechanical-engineering challenge to cram the systems in there. And across the fleet, there have been systems that we’ve already seen where there are gears, cams, and tiny little hydraulic pushers and pullers. It’s unclear, I think, exactly what will prove the best system for these things over time. But a lot of clever mechanical engineering is going into it from all the teams because it’s a very tight package down there.”

One consequence of this is that some of that engineering is external on some of the wings, as Jordan points out. “If you have seen wings with a bunch of little strakes sticking down, for example, or sometimes up. Those, just like you see on an aircraft, those are for control systems for the flaps.”

There are two more aspects to the mechanical-engineering problem that the design teams face; the fluid ­dynamics and the rules on center of gravity and mass—all three of these things interplay. “It’s actually the packing of the ballast that really starts to drive a lot of the design trade-offs,” Holroyd says. “At one end of the design spectrum, you can have a larger wing area and package most, if not all, of your ballast within the wing section. Or if you want to go for a smaller wing area, then ultimately, at some point you have to sprout a bulb or a ballast package of some description to meet that weight/CG requirement.”

What are the advantages of small wings and a bulb, versus larger wings and no bulb? Larger wings will provide more space for engineering the flap articulation—but that’s just the start. Jordan says: “The foil that gets you up and foiling early—which is very important—and the foil that does good maneuvers is not the foil that gives you high speed. In very simple terms, a bigger foil helps you get out of the water sooner. But then at high speed, it’s a lot more drag. And so teams are trying to balance those two characteristics to find what’s optimal for getting around the racecourse.

“If you see a wing without a bulb, a ­visible bulb, for sure it’s going to be on the larger size because it has to pack the ballast into it. That’s going to be a wing that’s geared more toward early takeoff and maneuvers. And when you see a wing that has a center bulb, then that’s one that they’re going for the least amount of wetted surface, and it is leaning more toward top speeds. It’s the balance between those two goals that is kind of the holy grail…a bit of a challenge, for sure.”

The transition to foiling was particularly important for Jordan. “Unlike the [AC] 50s, these boats seem to take longer to get up on the foil. So the team that can get back up on it in any kind of lighter conditions is going to have a huge ­advantage, because you can go from 10 knots to 30 knots with that transition. Even in the higher wind speeds, it’s a little bit ­cumbersome. A ­fundamental difference with these boats versus the boats of the last Cup is that a multihull has the ­majority of its ­righting moment when it’s sitting flat in the water. These boats have very little righting moment until they start to lean on the foils—and they start to fly. It makes the transition from displacement to flying harder than a multihull; it’s a balancing act between ­leaning on it and not tipping over.”

Wind speed will also be a factor in this calculus. Lighter wind will make it harder to get quick takeoffs and stay airborne during the tacks and jibes, while stronger wind means higher top speeds. The right balance in the trade-off between big foils versus small foils plus bulb will be very different at 8 knots of wind speed, and then at 20 knots of wind speed. This makes the designer’s job even more difficult, thanks to a change in the way this Cup regulates measurement certificates. In previous America’s Cups, the teams could change the certificate each day, and so they could change configuration according to the weather forecast.

“We have a single certificate that needs to be declared five days prior to the Cup and the Challenger Final,” Holroyd says. “This puts the racing outside the forecast horizon. It frames the design problem as creating an all-purpose set of foils, really based on the climatology statistics for the venue.”

He points out that a lot has changed since the Cup was last held in Auckland in 2003. The racecourses have moved into the harbor, and the race start time has changed from 1 p.m. to 4 p.m. “The ­expectation is that the average wind speeds will be a ­couple of knots higher than they were for the racing in 2000 to 2003,” he says.

We all know that the average wind speed is not the only wind speed that the boats will race in and that—while a truly all-­purpose set of foils would perform at both the lowest speeds in light winds, and at the highest high speeds when it gets breezy—in the end, something has to give in the trade-off.

We shouldn’t wrap up without a word about the rudders. Unlike the T-foils, the rudders work in the same way as on the AC50 catamarans.

“We have two axes of rotation of the ­rudder, both centered on the bottom bearing,” Holroyd explains. “One is the vertical axis; it’s the conventional steering rotation of the rudder, and that must be connected to a steering wheel. The second axis is transversely across the boat through the bottom bearing, and that allows us to rake the rudder fore and aft, increasing or decreasing the angle of attack on the ­rudder horizontal element [often called the elevator], and that gives us pitch control of the boat. In both cases, we are trading control versus wetted area and ­outright speed.”

Put simply, the bigger the rudder, the more control the helmsman has but the slower the boat will go because of the extra drag. “The simulated ­environment is central for making those trades, and ­ultimately, it’s a decision that you really need to make with the pilot and helmsman.”

It should be clear by now that while the design problem has undoubtedly got more dimensions in a foiling boat, its essence has not changed since Capt. Nathanael Herreshoff drew Reliance. One thing must be traded for another—ease of takeoff against top-end speed, steering control against straight-line speed, and so on. The designer’s job is to pick the right balance, and then optimize that solution to within a micrometer of its life. For all the froth and fuss over foiling, this balancing act will be the essence of this America’s Cup…just like all the others, before and after.

The post The Flying Technology of the AC75 appeared first on Sailing World.

Hull design has always been the most venerated aspect of an America’s Cup yacht. The name on the drawings has often been remembered with the same reverence as that of the skipper. This might not hold for much longer because the result of the 36th America’s Cup is just as likely to be determined by the work of a systems engineer as by a naval architect.

“The hull design is one aspect of many, but it’s not the ­dominant aspect,” explains Martin Fischer, co-design coordinator (along with Horacio Carabelli) for the Luna Rossa Prada Pirelli Team, who is on his second America’s Cup with the Italian team. “It’s not as it was with the 12 Metre or with version five (of the International America’s Cup Class), where the hull is really almost everything.”

The rules controlling a class are always a good place to start when seeking to understand a race boat because they drive so much of the design; working for the Challenger of Record, Fischer was part of the team that wrote the class rule for the AC75 with the defenders, Emirates Team New Zealand.

In the case of the AC75, the rules, Fischer says, are actually very open. They have little to say on the structure, for instance, requiring only a “minimum areal density of any part of the hull shell” (2 kg/m²). There’s also a limit on the internal volume (at least 70 m³), and after that, much of what’s left deals with details such as water retention, fairing flaps and penetrations.

There are only a few rules that drive the hull shape and its potential performance. “There is the length,” Fischer says. “The overall length is limited to 20.6 meters (minimum, without the bowsprit), while the beam must be 5 meters. Then there are two other very important rules: There is a theoretical capsize test that is done virtually on the computer. If the boat is turned by 90 degrees, the center of buoyancy must be at a certain position.

“This rule has a strong influence on the deck shapes. You might have noticed that all the boats have relatively high freeboard; this is partly for aerodynamics, but also, if you don’t have relatively high freeboard, you don’t pass this capsize test. The next important rule is that there is a minimum requirement for the waterplane inertia.”

Er…the water what?

“If the hull is floating, then you look at the intersection of the hull with the water surface (waterplane), and that gives the surface a certain shape. And then compute the inertia of that shape (it must be at least 20 m4). It’s not important to understand exactly what it is; in the end, it is more or less a measure or a constraint on the ­combination of that surface and its width.”

I’m not going to try to explain the ­calculation of the “second moment of area”—the important thing, according to Fischer, is that you “basically cannot make an extremely narrow hull, so you have to respect a certain area for that surface, and a certain width. The rule on the inertia is also quite type-forming; it imposes widths at the waterline. Of course, we all would like [the hull] to go narrow. Especially when the boat starts going fast, just before takeoff, we all want a narrow hull. And this is why we have these humps ­underneath the hull.”

Ah yes, the humps, skegs or bustles are one of the most significant shared ­features on all four of the newly launched, second-generation AC75s. The terms refer to the narrow, protruding section that runs down the centerline underwater. In the first-generation boats, only the Kiwi and Italian boats had this feature, and it was most ­pronounced on the latter.

“It’s a trick not to get around this inertia rule but to deal with it,” Fischer explains. “What you do is design a hull wide enough to pass this inertia rule while it is at the design flotation. And then as soon as it gets a bit of speed, the foil starts pushing up, and so the boat comes up, and then this wide part of the hull gets out of the water and only the narrow part remains. This significantly reduces the drag, especially during the takeoff phase.”

The humps also help when the boat touches down. “And that’s another reason for these humps underneath, because they allow you to fly lower, to take more risk, because if you touch a wave, the wetted surface, or the area that touches the wave, is very small, and therefore it slows you down only very little.”

Benjamin Muyl is on his second Cup with Ben Ainslie’s British challenger, having been involved in the event since 2005. Now the architect, he sums up the factors driving the performance of the AC75: “As soon as we decided that these boats are only going to race in flying (foiling) conditions, then there’s no point in having any righting moment from the hull. The whole righting moment comes from the foil, so then the hull shape is all about takeoff capabilities, so effectively [acceleration and performance at] slowish speed, in the order of 16 to 20 knots—the touchdowns. So, the ability of the hull to develop little drag when touching the water at speed or out of tacks, or out of jibe. And the other part of it, which is actually very important for these boats, is the aerial performance of the hull.”

This is the reason all four boats have skegs; they provide a benefit in all three areas that Muyl and Fischer describe. They enable better acceleration at slower speeds, and reduce the hydrodynamic drag and deceleration on touchdowns. This allows the boat to fly closer to the water, which has another important aerodynamic contribution. “On every wing, you have a high-­pressure side and a low-pressure side,” Fischer explains. “And obviously, the air tries to flow from the high-pressure side to the low-­pressure side, and if you let it do that, you lose lift. On a normal sailboat, this circulation that makes you lose lift is at the bottom, underneath the boom, and this loss is quite significant. To avoid that, on all the [AC75] boats, we see deck sweeper sails.”

Muyl worked with both Fischer and ETNZ’s Guillaume Verdier on Franck Cammas’ Groupama 5, the International C-Class Catamaran Championship winner. It should be no surprise, therefore, that their thinking is aligned here. “In recent years, we’ve seen sails and wings extend to seal to the deck. It pretty much started with the Groupama C-Class boat for Cammas. And then that was also seen on the AC72, and since then all the Cup boats have the mainsail sealing on the deck. On these boats (the AC75), for the first time we have a monohull that’s flying. So, what’s happening is that now there is a gap again, so we pushed to effectively seal the hull to the water.”

It’s impossible to completely seal the hull to the water without increasing the hydrodynamic drag, and even maintaining the minimum distance is made harder by waves. “So, even if you had perfect control of the boat, it would be impossible to close that gap completely. But [the teams] make big efforts to close that gap as much as ­possible,” Fischer says.

“We spotted [the performance effect of sealing the gap] early in the project,” Muyl adds, “and always questioned whether it was a true phenomenon, or whether it was an artifact of the computation. We finally made the call to go there to try to achieve it. It’s interesting to see that all the boats have gone there now. So, yes, we followed the same path. It was done with different means between the various teams, but we went for this very squared bustle to try to create a vortex off the sharp edge that would effectively seal [the gap].”

When we look at the four new boats, it’s clear there is significant agreement on what makes for a fast AC75. The skegs are the most obvious element, but an aerodynamic hull shape is a close second. The speed of the boats drives this one, with apparent winds that can easily exceed 40 mph.

“If you stick your hand out of a car when you’re driving at that speed, you feel how big this drag is,” Fischer says. “This drag component is comparable to the drag we see in the water. All the teams have paid enormous attention to this; they hide the crew as much as they can, and have the shape of the hull as aerodynamic as possible, to reduce drag as much as possible.”

If looked at sideways from the beam, all the second-generation hulls reveal an aero foil section from bow to stern—don’t be fooled by the high sides of the Kiwi’s crew pods. Fischer explains: “It is hidden because [ETNZ has] these relatively high cockpits on the side to cover the crew. But in between the cockpits, the shape is pretty much like an aero foil. The American boat also has a pretty nice aero foil shape, and as well, the British boat. I think the only main difference is that on our boat, it’s a bit more obvious, but the others have more or less the same idea.”

The third consistent element is the split cockpit. “The cockpits were pretty much the same everywhere at the beginning,” Fischer says. “All the teams have cockpits on each side, with the crew well-protected from the wind to reduce drag. Also, the Americans at the beginning had the cockpit very far aft. Now they are farther forward. So overall, I think we can see quite a bit of convergence, but there’s still a wide variety.”

The variety in the boats is driven by the details, and they will decide the winner. For instance, there are significant differences in the skegs, which shouldn’t be a surprise given there are three different motives for having the skeg in the first place. “The optimal shape for these purposes is different,” Fischer says. “If you focus on ­aerodynamics, then you want a pretty narrow hump, because if you touch down, the wetted surface is really small, and so you can fly lower. The penalty you pay, if you touch a wave, is less than with a wider hump. But with a narrow hump, you have difficulties in takeoff because the volume in such a narrow hump is very small, and you need a lot more lift from the foil to get the flat part—the wide part of the hull—out of the water.”

The choices the teams have made reflect the capabilities they have prioritized for the upcoming racing. “The Kiwis and the British have a wider hump underneath, which is pretty flat at the bottom,” Fischer says. “So, in my opinion, they try to generate positive lift when they touch, and probably also during takeoff. Of course, if you generate lift when you touch, that comes at a price —you also generate drag.”

Muyl agrees, adding: “[It’s] not forgiving if we touch because there’s quite a lot of wetted surface area to start with. So, effectively, we are relying quite a lot on the ability of the sailors to control the boat and to fly it just above the free surface.”

“American Magic has a very narrow hump,” Fisher says. “So, in my opinion, they’re focused more on aerodynamics and flying low than on takeoff.”

Or maybe they want the best of both worlds. Muyl points to a different takeoff technique. “Their strategy to takeoff is to accelerate as well as they can, but then, when they are at the speed to takeoff, somewhere between 16 and 19 [knots], they force the nose up with their rudder, and effectively increase the angle of attack on the foil and takeoff like that.”

American Magic’s designer, Marcelino Botin, wasn’t giving much away at this stage. Speaking at the launch of Patriot, he said: “We’ve got a philosophy of the boat that we need, and the boat we have produced is our interpretation of the best possible boat to take forward that way of thinking.”

And the Italians? “Our hump is more rounded, and I would say ours is somewhere in between what the Americans did, and what the British and Team New Zealand did,” Fischer says. “So that’s a choice. When you design the yacht, you have to make ­assumptions and define conditions for which you want to optimize your shape.”

The winning design will need both the most accurate set of assumptions about the competing priorities, and efficient optimization. Easy to say, but there is nothing straightforward about this process, as Muyl explains: “I find this boat really complex, in terms of how everything is so interlinked. If you look at just the foils, we have [in the fleet] some very large bulbs and some very small bulbs—the whole scope. So, that’s interesting that four teams of competent people with comparable tools, with comparable budget and time, effectively reached some very different solutions in the end. I personally found it very hard to have a feeling for what’s the direction to go to be faster. The whole thing is incredibly intertwined. I find it very complex. And that’s at every level of the design.”

Fischer agrees, adding: “This kind of hull was new for everybody, and basically, everybody had to start from scratch and find new ways. And I can say, I don’t know what the others did, but we went for a very mathematical approach to get there. We used, right from the beginning, a dynamic simulator.

“We used systematic, automatic optimization methods to get to the hull shape that we got in the end. And I think without this mathematical approach, it would have been very, very difficult. And I guess for the other teams, it’s the same. I think it is very difficult with these boats to get to a good result with pure intuition.”

Now that they can see where they fit into the fleet, how do they feel?

“Well, I think we don’t really know,” Muyl says. “We have a feel for New Zealand. I mean, they won the last one. They gave a sailing lesson to everyone. So, they are usually strong, but so much is about reliability that I find it really hard to have a sense that I can trust about where things are.”

Fischer was more guardedly optimistic about the Challenger’s chances. “I think as usual, [ETNZ] did a good job, but I don’t think they…well, I hope they won’t be superior, and I don’t think they will be superior. I think it will be pretty tight racing.”

The post Hulls of the Modern America’s Cup appeared first on Sailing World.

One final burn back to the barn onboard American Magic’s AC75 Defiant is one experience Terry Hutchinson won’t soon forget. At the conclusion of another long day of training in late September, helmsman Dean Barker pointed the bulbous blue bow toward the base, some 11 miles away, with a 12-knot breeze tickling the back of his neck. Fifteen minutes later, they were home, having almost cracked the 50-knot barrier along the way.

“It was exciting,” says Hutchinson, who experienced the high-speed tear from the boat’s 12th-man spot in the transom. “It was the first time I’d ever sailed in that spot and it was really good to see the starboard side of the yacht. I was hanging on for dear life because, at 40 knots there’s a lot of movement back there.”

The jovial banter over his comms unit as his teammates chased the elusive five-oh on the speedo, passing powerboats as if they were standing still, is what he remembers most. “It was really cool,” he says, “and it was impressive to see the level of comfort. It’s like when you hear the Formula 1 guys talking to their pit guys as they’re going around the track at more than 100 miles per hour. Just awesome.”

When Defiant finally came to rest alongside the team’s tender, Hutchinson could finally relax and exhale, knowing the boat had more than served its purpose on the long, complex and calculated path to the America’s Cup Match in March 2021. It was the final day for Defiant, which the shore crew would begin decommission and focus its full resources on Patriot, the team’s second AC75, which will be sailing by mid-October.

Patriot, shipped from its build facility in Rhode Island to Auckland in the belly of an AN-124 transport aircraft in early September, is more than halfway through its four-week fit-out, says Hutchinson, as a result of 24-hour shifts inside the base since its arrival. “When we were sailing one boat and finishing out the other one, that 24-hour shift was huge because it allowed us to do both operations,” he says. “Now we have twice as many hands working on Patriot, which has been great.”

It’s all seemingly going according to plan, Hutchinson jokes, especially given the COVID-19 curveballs thrown at challengers and Defender alike. Through luck and good planning, they appear to be one step ahead of major disruptions.

“We started sailing [in Auckland] on July 27, which was about seven days earlier than what we had planned for pre-COVID,” he says. “To meet that milestone is pretty amazing. The time in the simulator kept everyone up to speed, and the motivation among the guys to go sailing when we got here was essential to getting us on the water and being efficient with our days.”

From their first Auckland outing to Defiant’s final day, Hutchinson says, the team logged 26 days of on the water, losing only two weeks to weather. It’s also worth noting, he adds, that the New Zealand winter has been the warmest on record since 1903. In fact, warmer than their winter session in Pensacola, Florida.

Fortune presents itself in many ways, and their quality time on the water in the eyesight of Defender, Emirates Team New Zealand, is yet another boon. “The pressure of having them across the harbor has been a positive as well because it gets us out sailing in conditions that we might not go out in because it’s too windy. There’s a certain level of pride that comes from executing in those days. The gain rate is exciting.”

How much faster they are today than when they left Pensacola in March is impossible to quantify, Hutchinson says, but “we’re going in the right direction.”

Everyone else is as well, however: “It’s now getting very real,” he adds. “We’re in the venue and don’t have the ability to hide.”

From images and videos shared by the team, as well as footage captured by land-based observers, there’s been plenty of training conducted in wind strengths well beyond the limits in place for the pre-Cup races, starting with the Christmas Cup in December. “The knock-on effect of sailing into the upper wind range is the confidence you come in off the water with,” Hutchinson says, “the guys get over the intimidation and start sailing the boat better every time. The more comfortable you are in that sort of environment, each day becomes just a race day—nothing more, nothing less.”

And building that comfort level also includes the inevitable capsize, which the team recently experienced. Like no big deal, the AC75 was reportedly righted in 4 minutes. The rig and the array of hydraulics inside the boat were inspected before they were cleared for a few more hours of high-wind sailing.

he capsize happened in slow motion, much like that of Emirates Team Zealand’s earlier in the year. “We were hauling the mail [in 24 knots of wind] and when we bore away the foil arm dug in really hard,” Hutchinson says. “When the boat decelerates like that the apparent wind goes aft very quickly and the momentum of the rig pushes you over. We were sailing through the apex of the acceleration, so anything that causes deceleration on these boats is no bueno. We all got a chuckle on the comms, made sure everyone was OK, got the bow line on, pulled her into the wind and up she came. No harm, no foul.”

Having inadvertently checked off “capsize recovery” from their to-do list and begun preparing Defiant as an “insurance policy,” Hutchinson says the effort is now fully on commissioning Patriot, which is rumored to be different enough to give spies and Cup watchers plenty upon which to speculate.

How different?

“I’m not going to give you much,” Hutchinson says, ever careful to hint at anything that would tip off his competitors too soon, “but if you look at the evolution of all the boats, the position that INEOS [Team UK] and us are in—because we didn’t have the class rule as long as the defender and challenger of record—our opportunity to make big gains between hulls one and two is substantial. The Defender and Challenger of Record have very nice platforms. There are features of both of those team’s boats that other teams like, so I expect to see all the teams gravitating in that direction.

“You won’t be disappointed,” he concludes. “Defiant has been a great boat for us. It’s taken us a bit of time to sail it to its potential and we were still just scratching the surface, so it’s been the right platform for us to learn on.”

While American Magic’s crew has yet to sail Patriot, they have spent plenty of time with it in the simulator, which has certainly become the most powerful proprietary tool of this Cup cycle. Still, nothing beats time on the water with a new boat.

“There will be a certain component of starting over,” Hutchinson says, but that’s the exciting thing because Defiant taught us certain techniques, and with Patriot those techniques will be different.”

Looming in the near future, he adds, is the racing itself, and there is a level of anxiety among all the teams. For the past year, each syndicate has been exclusively focused on their AC75 development, and with cancellations of events in Italy and England, the Christmas Cup will be revealing—for better or worse. “This will be the first America’s Cup for all the teams where they’ve come into the main event and have not done any racing, which is terrifying in itself,” Hutchinson says. “You can only simulate racing in practice and in the simulator, so there is always an added pressure when there’s another boat on the course next to you. There’s a lot of investment that goes into this and it’s all decided on the water in a short period of time.”

The Defender, he admits without pause, is a polished team, and the benefit of now being on the same waters is critical: “We see a lot of clever thinking, so we like being around them, and learning from them is a real opportunity. If we were to go racing with them today, we’d have our hands full, but that’s OK. We’re focused on the results, but we’re also focused on the details to get that result.”

The post Faster Times Ahead for America’s Cup Challenger appeared first on Sailing World.

From where Dan Morris ­usually stands on board American Magic’s 75-foot ­foiling America’s Cup yacht, the view is pretty spectacular. It’s a perspective only a handful of humans will ever experience. It’s wet and windy, and it’s Zen-like when the boat soars at 40 knots. As the portside headsail trimmer, Morris has the luxury of full visibility of his towering sail. He can see up the leech and across the acreage of black cloth, its dozens of yarns flickering and painting a picture of the wind as it streams across both sides of the sail and exits with full force in his face. He can observe the leeward side of the twin-skinned mainsail as well, plus the big grinder in front of him, relentlessly pumping hydraulic oil so he can make microadjustments at will. This is life in the slot for Morris, and life is good when all senses are being bombarded.

Sights in the Slot

I’m on the port forward ­pedestal, facing forward, so I can see what’s coming on the water from only about 30 seconds out. I can’t see what’s coming at 10 seconds. Because I’m trimming on the leeward side, I can see the jib really well, but with all the end-plating we do on the mainsail, I can’t see the windward side at all. I can see way out in front of me, but I can’t see the gust that’s going to hit in three seconds. It’s quite different from a normal boat in that way.

On starboard tack, I’m in this deep chasm of a cockpit—up to my shoulders more or less. The wind rushes through the slot, and there’s so much wind in my face that my eyes are always watering. I don’t wear sunglasses when I sail because they change the way I see the breeze and the sails, so I’m always squinting as hard as I can to keep them from ­watering too much.

One of the coolest things about being on the leeward side trimming the sail is there’s never that mental trade-off of “should I be hiking or trimming the sail perfectly?” like I would on normal boat. I always have sight of my sails, something I never get on most boats.

When I look to leeward, all I see is a massive plume of spray coming off the foil. That’s when I realize how fast we are going. I’m looking at our targets on the display, and trim to them most of the time—unless we are in a different mode for tactical reasons. I’m looking at the leech, the entry of the sail, and trying to balance the power from top to bottom.

If we want to go fast, we need a flatter, more twisted sail. If we want to go high mode, we want a deeper sail, so I have to balance the power across the whole sail. That’s the coolest thing about these boats: I can see the entire sail and make continual adjustments. When I sail a conventional boat, I can get only a snapshot of the sail profile when I go to leeward, and then go hike and try to know what the sail looks like from the leeward side. On the AC75, trim is instantaneous; I can make any adjustment I need at any time. I never have to decide whether it’s worth leaving the rail to make an adjustment. It’s always worth the adjustment.

When I’m on the weather side, on the opposite tack, I’m grinding more, but I get to have a look out of the boat and see the breeze; that’s when I can sort of calibrate myself. I have a better look at what the main trimmer and driver can see with the mainsail; I can see the wind, see how the boat is reacting, and link these mental images together when I’m back on the other tack.

The other part of my sight is that I have this massive human in front of me pumping away, and he can block my view sometimes, so I have to look around him as well. Also, the mainsail is big and always moving, and it can block my view of other things. That’s the big trade-off: I can see my sail, but I can never see upwind of what I’m ­trimming to.

The Sounds of Efficiency

When I’m on the leeward side and trimming, I can’t hear anything that anyone says on the boat. Ever. Terry (Hutchinson) is right behind me, and he and Dean (Barker, helmsman) and Paul (Goodison, mainsail trimmer) all have comms, and they can speak into their microphones. The rest of us have earpieces, but there’s so much wind going over my face and past my ears that a lot of what I hear is like having my head out the car window on a freeway.

I feel changes to the boat, for sure—with my entire body—and in my position, I really have to anticipate. If I know it’s going to be shifty and we just got into a puff, I know we’re probably going to be going into a lull pretty soon, so I’m planning for what my next move is going to be and what needs to happen in what order. It’s not quite the same as visual anticipation, but it links into the hearing part of sailing the boat in that any verbal cue I get off Dean or Goodie saying, for example, “The breeze is building” or “Shot coming,” I can be ready for it. On regular boats, the trimmer is usually calling the breeze back to the driver, but with this, it’s opposite. Dean calls out what he sees in the breeze, and that’s a call to me to be prepared to make an adjustment to match what he’s going to do with the wheel and what Goodie is going to do with the mainsail.

Going into a tack, I hear the calls coming from Dean—always super calm and neutral. It’s a steady, “Set up tack, and then 3…2…1….” The cadence from Dean is always the same. He’s soft-spoken, so I always have to be searching for it. Then I go straight to my processes. Once the boat starts to turn and we start to slow down a bit, some of the wind noise goes away. The foils get a bit quieter, then the traveler car and sails cross the boat, and that’s quite noisy. When the mainsail pops, ­everyone knows it. It’s a big mainsail with two skins and twice the sets of battens popping. As we build speed again, all the other noises come back. Hopefully the foils are not making too much noise, but sometimes they do, and that’s just water over the trailing edge, just like the hum on a 420 ­centerboard on a windy reach.

In and out of any maneuver, we’ve got the guys pumping a lot of oil to get the boat settled. Imagine coming out of a maneuver on any big boat; there’s a lot going on with sails being eased and retrimmed or flattened and deepened, and that takes energy, so everyone is just hammering away at the handles. I hear the grunts of the big dudes as they’re putting in massive effort. The electric pumps for the foils are whining away, like they do on a canting-keel boat. Then it gets quiets right out the maneuver, and I just hear the wind rushing over my ears and the comms from Dean and Goodie about what we’re going into next.

The Feel of Fast

The AC75 feels like a big Airbus jumbo jet. Everything is so big and loaded. It’s not the same as with a Moth, which is loose and fast; this thing is very locked-in and smooth. It’s a giant piece of machinery, which makes it feel slower, but the speeds are really high. And even though it is this big locked-in thing, when we go through gusts and lulls and have big changes in lift on the foils, the speed changes fast, so the boat can get loose sometimes. If it does, my feet are trying to hold onto the deck as best I can, which sounds silly, but I’m always trying to stay connected to the boat. If I don’t, I get tossed around a bit. It’s like standing in the back of a pickup truck doing doughnuts in a parking lot. My hands are either on the handles or on the sheet so I have something to hold onto, but when we bear away, it’s full-on G-forces, so I have to brace myself against something. One thing for sure is it brings real fatigue into my lower body from stabilizing myself all day.

When I’m trimming, the sheet is pretty loaded and I have to be accurate with every adjustment, so I really have to have a firm hand on the sheet so I never accidentally overease it. The jib is very high-aspect, so a small ease on the sheet does a lot to the shape of the sail, top to bottom.

When we take off, I get a good hosing from the foil arm. It’s worse for the guys on the windward side. Water comes at me with pretty good force when we’re going that fast, so it’s cold. Usually it’s really cold at the beginning of the day, but once I’m warmed up, it’s not a big deal. The wettest part is takeoff because the whole boat is in displacement mode and both foils arms are submerged, but once we’re up on the foil and in the air, it’s pretty dry.

The Smells and Tastes of Team Effort

I sail with Luke (Payne) ­opposite me on the pedestal. He’s one of my best friends and an awesome guy to sail with, and yes, he’s got proper odor. We used to sail against each other in the match racing and he had the same scent, but it’s a very comfortable scent to me to go racing. Other than that, it’s hard to smell anything on the boat because your nose gets really dried out because of the wind flow. But the one defining smell of this campaign, for real, is the smell of good, hot coffee. We are now in the land of coffee. New Zealand has some of the best coffee in the world, and I guess that’s because they love it so much. All the boys in the boat love coffee. I suppose we all drink a bit too much, but there’s a camaraderie to it as well. You have your best meetings when you have a coffee together. (Team testing manager) Anderson Reggio is also a coffee lover. He has a little 12-volt espresso maker that he brings out with him on the chase boat. He’s an analytics guy, so he likes it right. He’ll have his espresso that he makes midday, and if I’m lucky, I might get one off him. I’d be in favor of having a proper espresso set up on the chase boat. If I were at the top and in a position to make big team decisions, that would be the first thing I would do.

RELATED: Weighing In On The AC75

There’s also the smell of the base in the morning. It’s the smell of work. These boats are heavily reliant on hydraulics, so the smell of the oil is always there. That’s the first scent that hits me when I come into the base. After that, I check my gear in the container with the drying room and make sure my personal kit is ready for the day. As you can imagine, there’s a pretty foul smell in there with 20 guys’ gear and wetsuits hanging in here. We have long days on the water, and you just rinse it and hang it up; it’s close to the smell of a hockey locker room.

Then, it’s breakfast. We’re lucky to have good teammates sort out our food, always making sure we have nutritious food, and that we get our bacon. I love the smell of warm breakfast, especially when I don’t have to make it myself.

On the water, once you get out and away from the city, the air is definitely fresh and clean, especially when the breeze is coming off the ocean—that’s always a treat.

The Sense of Space

As high-tech and wired as the boat is, there is a definite seat-of-your-pants element to it as well. We’re not sitting, per se, but I definitely feel all the subtle motions of the boat. I have the performance numbers in front of me all the time, but they’re more of a report card of how we did in the last second or two; they don’t tell us how we’re doing in that instant. Feel is different for everyone, so it’s a hard one to describe. When you take off enough times, you get a feel for ­anticipating what the boat will do next and what it needs in order to do that.

Like any boat, flat is fast, and whatever the perfect heel angle might be, we have to stick to it. Heel angle is huge, and that’s one we can get from sight, especially for the guys looking aft; they’ll be looking at the horizon across the transom. But I also get that heel sensation through my feet; I can instantly feel changes to heel angle before I see it.

When the windward foil gets dropped, that’s essentially the start of the turn, and everything is focused on how that foil responds to the water. If it connects well and everything goes right, it’s very fluid. That’s all on (flight controller) Andrew Campbell. I don’t envy his job at all and don’t want anything to do with it—ever. He has to get it right. If just one little thing goes wrong when the foil goes into the water, it has a huge effect for a bit after the maneuver. If it enters well, the attitude and feel of the boat don’t change at all. It feels seamless. The heel angle is consistent, and we exit not much slower than when we started the turn. It’s magical when it happens. If it doesn’t go in perfectly, it throws off the way the boat feels and the way it reacts to everything else. In that case, everything needs to get readjusted; everything on the boat is moving, the rate of turn is changing, and you’re slower out of the maneuver. It’s a huge effort to get back up to speed. We’re still foiling and going fast, but everything is unsettled, and it’s a big job to lock it all in again.

I’m also feeling the pitch of the boat; the bow up-down trim is huge. The foils have a big effect on that, but so do the sails. As much as I’m feeling the heel angle and using that to judge how to balance the power in the sails, I’m also thinking about how my sail trim affects the pitch. The 75s being so big, the boat is quite steady when we dial in the pitch.

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“Seeing our boat unloaded in Auckland was an awesome moment for our team, and a significant milestone for the America’s Cup as well,” said Terry Hutchinson, Skipper and Executive Director of American Magic. “Soon we will all see American Magic out on the same patch of water as the Defender, Emirates Team New Zealand. That’ll definitely be an exciting sight for sailing fans worldwide, and for us it will be a daily reminder of the huge task we have in front of us. Every possible training day from now until the Prada Cup is priceless, and we are focused on going sailing again as quickly as possible.”

The Bristol, Rhode Island-built foiling monohull is the first Challenger yacht to arrive at the venue of three upcoming regattas: ACWS Auckland (December 17-20, 2020), The Prada Cup (The Challenger finals, January 15 – February 22, 2021) and the 36th America’s Cup (March 6-21, 2021). The U.S. team also expects to take delivery of their second AC75 in Auckland sometime during the fall of 2020.

American Magic’s focus over the coming weeks will be in three primary areas. First, the team will work to complete the New Zealand entry and quarantine process for team personnel and their families, which was made possible after the team received border exemptions from New Zealand’s Ministry of Business, Innovation and Employment on June 12. Second, the AC75, chase boat fleet and the team base will be assembled and activated in Auckland. Third, American Magic’s production team in Bristol will put the finishing touches on the second AC75, and prepare it for air transport from Rhode Island to New Zealand.

“I could not be more proud of how our 145-person team has handled this shipping process, and everything else the pandemic has thrown at us,” said Hutchinson. “Our shore and operations team pivoted incredibly well as events happened, and as the focus changed basically overnight from getting us to Europe to getting us to Auckland. Our production guys have been able to safely keep the Boat 2 build process going, and it looks incredible. And our design group has maintained a singular focus of developing an AC75 capable of winning the 36th America’s Cup. Now we just need to pass our remaining team members through quarantine, keep everyone healthy and safe, and get back to business on the water.”

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“Mechatronics engineer.” That’s one job title that never existed back in the America’s Cup’s 12-Metre era. But today, every Cup team has a few on payroll. These are the unknown wizards tasked with ensuring that every adjustment on the AC75 is precise. From micro to macro, from the top of the rig to the tip of the foil flap, when and if someone presses a button or pushes a toggle on these complex flying beasts, something logical better happen, and it better be right. Such is the new high-tech domain of modern America’s Cup ­sailing, one in which software, hardware, electronics, hydraulics and human input interplay through intricate systems.

“It is the crux of performance,” says James Lyne, head coach of the New York YC’s American Magic challenge. “The Cup can be won or lost in these control systems.” Lyne, who analyzes every move and every adjustment the American Magic sailing team makes on board its AC75 Defiant, can see through 14 onboard cameras and a deluge of data streamed from the boat just how important this business of mechatronics is to getting up to speed and around the race track.

Let’s start with the big picture: Who does what on the boat?

We’ve split up the tasks of controlling the boat. Dean [Barker], the helmsman, has control of the wheel and various things, but his primary role is to steer the boat around the course. Paul [Goodison], as the mainsail trimmer, controls the shape of the mast and the [twin-skinned] mainsail. He also has some control of the jib. Andrew Campbell is then, ­effectively, in control of flight. From his position, he controls the foil cant, foil flap and ­rudder rake. Other people can also control those functions, but 99 percent of the time, three people effectively have control of the boat.

That leaves eight grinders, and one of those is a tactician. The tactician is talking about the course and the options, so in that sense, we’re set up a bit like a traditional boat. All the grinders are doing is, as they say, “We grind forward and then we grind backward.” It’s an oversimplification, of course, because these guys are electronically changing gears and choosing functions depending on the task at hand.

The grinders are ­essentially running who’s in what and how much power to put in at any moment. If they choose the wrong function at the wrong time and let oil pressure get too low, the boat will get unbalanced quite quickly, and the flight controller and the helmsman can’t do anything about it. Nothing ­happens on these boats without hydraulic pressure.

How many control buttons do the grinders have to manage while also hammering away at the handles?

It’s traditional in that they’re using foot buttons, but they’re electronic rather than mechanical. When you look down into the cockpit, into all the grinding stations, you’ll see there’s an array of buttons. The jib trimmer has at least six [foot] buttons just to himself, from the engaging of the winch, to the jib cars and the up-down systems that affect his sail shape. It’s like a dance/game for them because they can’t be off the handles for any lengthy period of time. We need a certain amount of watts, on average, to power the boat.

The grinders are producing almost what a professional cyclist would produce, over a relatively short period of time. We’re asking these guys for more than 200 watts on average, with spikes of nearly 1,000 watts on special occasions where they need to dig deep.

So, what’s happening, systems-wise, when a foot ­button is engaged?

When they press a button, an electronic signal is passing to a programmable logic controller, which is programmed to control the opening and closing of hydraulic valves or ­mechanical mechanisms to achieve a given function. For example, are they straight into a winch, or switching to fill an accumulator tank or drive a hydraulically controlled sail function? Are they behind in how much oil they’re producing? When they’re coming to the boundary and they have to jibe, if they’re low on oil, it’s not going to be pretty. Paul, Dean and the trimmer are the primary consumers of the energy, and the grinders are choosing how that energy is allocated around the boat.

I can imagine there is quite a ­complex web of hoses, pumps and rams below deck.

When you look inside the boat, it looks way more like the inside of a plane than it does the inside of a boat. It’s impressive. You’ve got a lot of electronics, a series of pumps and hoses to produce and supply pressure, and tanks to store high- and low-pressure oil. Without the high-pressure tank/accumulator, there are moments around the racecourse where it’s impossible to generate enough grinding power to meet the demands of the boat, so we’re always asking the hydraulic system to be more and more efficient.

When people look at the boat, it looks sort of traditional in that there’s an outhaul, a mainsheet and jib sheets, but the big difference is the forces this boat generates are so big that the whole boat would have to be one big purchase system just to do something as basic as trimming on the mainsheet. We have to handle tons of mainsheet load, so that’s why the systems are dominated by hydraulics. These boats produce so much righting moment that the loads on all the sail-control systems—never mind the foil-control systems—are more similar to a 120-foot multihull, in terms of righting moment.

How much of all of this can be automated with software?

The class rule is pretty ­stringent on how we can use feedback loops in our software systems, but everything has to have logic. For example, when Paul pushes a button or a lever on his control box, there is logic running in the background to translate his input into a valve command, or series of ­commands that perform ­multiple functions at a time.

Let’s put the boat in motion. What’s the sequence of ­mechatronic events to get the boat flying?

The AC75 is unique because the boat has no effective initial stability. It gains stability only when it gets flow across the foils. In light air, we can hip-tow the AC75 [with the tender] up to a speed of around 7 knots, where they have steerage and some semblance of righting-moment flow out of the foil. Then we spike the side tow off and they fall off onto whichever tack, ease the sails, and then slowly accelerate the boat.

As they accelerate to about 10 knots, the boat starts generating quite a lot of righting moment from the leeward foil. At this point, they can start sheeting on the sails. They’re always trying to balance the righting moment generated by the foil versus the aero load of the sails to allow us to get to takeoff speed. Where takeoffs can go bad is when they’re either producing too much righting moment versus aero lift or vice versa.

Takeoff, in other words, is a delicate balance between the forces, so one moment they’re sort of sailing in displacement mode at 12 knots or so, and there’s not a lot of load on anything. Once they’ve taken off and they’re doing more than 20 knots, all of a sudden, the loads on the boat increase by a factor of 10.

Explain what’s happening when we see the massive foil arms set in motion.

Andrew, as the foil trimmer, has control of the cant system, so as soon as they’re off the tow and at a decent wind angle, he brings the windward board up, which increases righting moment and gives them the ability to take aero load very early on, while they don’t have a lot of foil load. Then, he effectively puts the leeward board to a target cant angle, which at that time will be set up to provide the right amount of lift and side force for the acceleration. The foil-cant system is one-design; it is run by a battery, so the grinders don’t need to power it. All we have control over is when it moves and how much it moves. The rams are big gears, and as you would imagine, the amount of load the foil arm and the cant system sees is incredible.

How much control then do you have of the active leeward foil when it’s loaded?

We use it dynamically, though the adjustments are relatively small. Think of the foil cant as a gross adjustment and foil flap as the ride-height control.

The accumulator tank volume is one-design as well?

Yes. It’s about a liter and a half, which is hardly any, so that’s why you see the grinding team working the whole time, from the moment they come off the tow to the moment they’re back on tow.

One challenge of the catamarans of San Francisco and Bermuda is the transfer of crew during maneuvers, which is less of a factor with the AC75, right?

There are all sorts of things that must go right with every maneuver. The rates of the maneuvers are very similar to the boats in Bermuda, so for most people, it’ll appear to be a pretty fast rate of turn. There’s a big onus on producing aero lift into and out of the tacks and jibes. They can turn too fast and skid out, which means all of sudden there’s no flow over the foils. So, there is a limit as to how fast they can maneuver.

As far as crew moving from side to side, some teams send people across, while other teams don’t. We’re still working on who goes where, but compared with the AC50, there are fewer people moving through the tack. The people who are moving, however, are the most important, so that makes it relatively tricky, and that’s where the efficiency of every system has to be right.

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The launching of a new boat is always a special moment, especially for an America’s Cup team, because it’s a defining and major milestone in the campaign. Until the sequential revelations from Emirates Team New Zealand, American Magic, Luna Rossa Prada Pirelli Team and finally Ineos Team UK, development and design had happened behind tightly closed doors or through small-boat testing; we are now in a period of reckoning for the four challengers on a number of fronts.

Internally for each team, the next phase is about validating design tools and debugging many of the new detailed design features found everywhere on the boat. Externally, it’s checking in with the solutions of the other teams and understanding why they chose certain directions. Moving forward from the launches of these first-generation AC75s, design teams will adjust and simulate the different directions, if they haven’t already; but only when the sailing teams actually line up in Cagliari, Italy, at the end of April will we know who is on the best track.

To make an early assessment, we must first consider the overall package, starting with the hull and deck. Considerations of whether the America’s Cup races in Auckland in 2021 will be sailed in foiling conditions or how often or in what windspeed will a team drop off the foils when tacking is important. There is likely much discussion about the minimum true-windspeed in which these boats will race. One thing is for sure, the racing will be pretty boring to watch if these AC75s are not foiling.

Before getting into the details of the ­different solutions, however, it’s important to point out some of the hull and deck limitations defined by the AC75 box rule. The illustration above shows a perimeter line, which is the projected shadow of the boat’s ­outline, down to the measurement water plane (MWL). There are minimum and maximum dimensions that the perimeter line must pass through, or be within, which limits the shapes of the hull to a certain extent. The strictest limits are hull length—basically 68 feet—and beam, which is set at 16 feet.

The deck is also called the upper hull ­surface, and it is anything above this perimeter line. The minimum height of the bowsprit is 3 feet above MWL. The mast-rotation point is specified at 5 feet above MWL and a fixed distance from the transom, so the mast position is set. Another important parameter that affects the ­overall hull and deck shape is the ­cockpit sole, which must be at least 4 inches above the MWL. This leaves a roughly 4-foot ­cockpit cavity to hide the crew below the mast ball. A big, strong grinder (arm grinding is required this time) needs at least 5.5 feet to be mostly upright and efficient.

Other requirements are based on hull volume. For example, a minimum bow volume forward of the 31-foot plane is 40 cubic meters, in consideration of pitch-pole prevention. Similarly, for stability, the 90-degree capsized volume of the hull and deck in the water must be at least 32 inches above MWL, so there needs to be significant volume above the waterline so that the boat will have some tendency to right itself. There are a few other stability requirements to ensure a minimum righting moment with the boat upright, which keeps some level of required transverse waterline fullness.

With the AC75, we probably need to replace the term “sheer line,” which used to be an important aesthetic consideration even with race boats, with the “perimeter line.” The perimeter line, as mentioned earlier, is the outermost portion of the hull tangent to the tumblehome shapes we see on these boats. The packages of both Ineos UK and American Magic push the perimeter line down close to MWL, for a softer leading-edge bow shape and better lead into the airflow around the jib.

Emirates Team New Zealand and Luna Rossa have more slab-sided bow profiles. Three of the teams opted to put the aft perimeter point quite low. Team New Zealand and the Italians look the lowest, with American Magic and the outlier Ineos being the most radical by pushing their middle and aft points at least 1 foot above the mast rotation and carrying their ­maximum beams all the way aft, resulting in a barge‑like appearance.

Again, these are all aerodynamics-based decisions and directly connected with the deck layout, crew positioning and grinding-pedestal heights. Each team is trying to keep crews out of the free stream as much as possible and has chosen to create a centerline deck endplate aft of the mast that tapers down to a narrow trailing edge at the transom. This approach minimizes vortices as the airflow exits the hull.

Each team will eventually seal the mainsail down to this surface for the best efficiency from the mainsail.

The centerline cockpit structure ­essentially locks most of the crew into set positions, so it looks as if three of the teams have chosen to keep all eight grinders in permanent spots (four each to port and starboard), with the helmsmen and trimmer being the only sailors switching sides behind the traveler track. Ineos, in contrast to the other teams, placed two grinding pedestals forward of the helmsman station and two aft, allowing for all of the crew to be on one side of the boat to take advantage of the extra righting moment. This also explains why it carried its maximum beam all the way aft and high—to shield the crew­members and keep them outboard. Maneuvers on Ineos’ Britannia will require a bit more calisthenics and coordination transferring from side to side, as well as the additional weight of four additional grinding pedestals.

Below the perimeter line, differences between the boats are significant as well. Britannia has the fullest shape with the maximum beam extending right down to the waterline and carrying a U-shape aft to the transom. It’s also wider than the minimum 13-foot beam at the transom. It appears the boat might be close to the forward-beam maximum limits too. Britannia’s underbody is fair and smooth, with minimal rocker, which produces a ­shallow dish-like shape. It is by far the most stable hull, which should allow the sails to power up quicker and accelerate for takeoff, but the extra surface area might make it a bit sticky. This transition zone may become a critical area for all the teams.

American Magic’s Defiant has similar full‑hull sections and looks to be close to the maximum forward-beam limits, but with a narrower waterline than Britannia. It also has much softer sections and a strikingly different bulbous bow, which is likely aero-friendly. The transom section looks as if it’s close to the minimum beam limit and has a fairly low aft sheer line.

Prada Luna Rossa and Team New Zealand’s Te Aihe are the most similar with pronounced V-shaped sections blending into a rounded keelson, then blending forward and aft into the hull profile from stem to transom, deepest in the middle—with Prada Luna Rossa looking to be the deepest and sharpest of the two. One thought about the reasoning behind this is that distributing the required volume toward the centerline could allow for more windward heel before the hull edge touches the water. Certainly all hull touchdowns while foiling will be costly regardless of hull shape, but these shapes might reduce the effects of the touchdowns.

I suspect all of these hull and deck shapes are derived primarily based on computational fluid dynamics upwind-foiling velocity predictions. With some baseline sail shapes fixed, each team would have run through a matrix of different hull/deck shapes and crew positions that satisfied the rule limits and refined these shapes and crew arrangements to maximize overall straight-line performance. There are plenty of options here that give similar results. The full-foiling, dynamic simulations are complicated, but it is possible to include tacking and jibing with many assumptions and ­bottom-end limits.

Plenty of other work is being done on displacement sailing and transitions from partial-displacement sailing to foiling takeoff. Displacement foiling transitions require an extensive database to properly support the simulator’s velocity prediction and give useful results without too many assumptions. There is still a lot to learn from sailing these boats at full scale, especially in lower windspeeds. Compared to the AC50 and the AC72, the AC75 is a comparatively heavy boat with a short mast and no wing.

I’m curious to see how each package ­performs in 8 knots of wind—even 10 knots of windspeed—and how much the hull shapes contribute to performance in these marginal conditions. It all begs the question: What is the windspeed required to fly an AC75 around the entire racecourse?

The Foil Packages

From the early launches we’ve seen many different shapes emerge: straight wings, anhedral wings, fences, bulbs, no bulbs and winglets. Hardly surprising. Again, let’s first review the sandbox in which the teams are allowed to play. The trapezoidal area in the illustration below is the only zone in which teams can attach their wings and wing-control systems. Variations seen from each of the teams already are indicative of the many options available.

An additional requirement is ballasting in the wings. The rules mandate a certain level of stability, so the total weight of these wings must be at least 2,000 pounds.

Consequently, the boat’s overall center of gravity is low for low-speed handling. Teams are only allowed to build six wings, but are allowed to change up to 20 percent of the wing weight. Three of the four teams have elected to integrate bulbs into their wing designs. It’s conceivable that 80 percent of the wing weight is in these bulbs, which would allow the three teams to plug multiple wing designs into these same bulbs without them counting toward the six-wing limit.

Emirates Team New Zealand did not go in this direction, which means it could be more confident that it has enough options available and wants to develop shapes without bulbs to distribute the required volume into the foils. Steel has about 70 percent of the density of lead. The bulbs are likely to include lead, and Te Aihe’s foils are most likely all steel.

The flaps on these foils, like those on an airplane, control fly height, but it’s hard to glean much from the photos released to date. There are, however, flaps like those on Britannia that show a distinct line separating the main foil from the flap at around the last 30 percent of the main foil. Morphing foils have been around for some time; the rule requires a distinct axis of rotation for the flap, but allows for flexible material to act as the hinge. Some of the foil-flap ­intersections are indiscernible from the available images, so it is hard to tell exactly what Emirates Team New Zealand is doing here.

The one-design foil arms look pretty chunky, but have been structurally vetted through full-scale testing, which delayed the launches of these AC75s by about six months. The 2 to 4 feet of the foil arm are available for variation. Most teams have pushed to reduce the surface areas and thicknesses here, leading to steps or sharp reductions in the bottom of the foil arm, which will be in the water most of the time.

The above illustration shows the basic-force diagram of an AC75, looking from behind, in the foiling condition. Essentially, the boat’s weight working against the lifting foil provides an available righting moment against which the sails can push with heeling force.

A small portion of this heeling force is actually thrust forward, which is equal to the hydrodynamic drag of the foils in the water and the aero-drag of the boat in the airstream. The game is both maximizing thrust and minimizing drag.

These boats are interesting in that the foil arm can be rotated (or canted) to almost any angle. The farther outboard the foil arm is canted, the more righting moment the boat can develop, which can mean more speed. Many combinations of foil cant, boat-heel angle and fly height need to be quantified. Some early videos of Defiant and Te Aihe show the boats foiling with the hulls quite close to the water.

A boat’s distance to the water needs to be minimized both to increase the righting moment and to seal the lift from the sail plan against the water to reduce the vortices traveling around the hull. The foils need to be as close to the water surface as ­possible without ventilating.

What is under the hood—in other words, the parts we don’t see—might in fact be the most important aspect of the AC75. In the 12-Metre days of the Cup, some of the old guys used to say you could tell who was winning the race by the boat that was more heeled over.

With the AC75, it will likely be the boat with the smoothest flight and the ability to get settled quickly after maneuvers that will win in 2021. That said, all the internal systems controlling the foils and the sails are key elements to stable flight. All four teams promptly launched, sailed and foiled; however it appears that Team New Zealand and perhaps American Magic actually have significant air time.

Team New Zealand appears pretty stable, much like it was in the 2017 Cup with the AC50; no doubt elements from that system have been incorporated into its AC75.

While internal controls are unseen, some portions of the external sail systems show obvious differences. Defiant, for example, sports a conventional boom, as does Te Aihe. However, Te Aihe’s sails extend all the way down to the deck. Britannia and Prada Luna Rossa appear to be boomless, with something closer to battens controlling the lower sail shape. The twin-skin mainsails are on all of the boats as dictated by the rule, along with the one-design mast and rigging.

It also appears that all teams are ­experiencing some downtime as they debug their new boats. These are complicated machines, so technical difficulties are to be expected. Sailing time, however, is precious for continued system development; so the teams must balance reliability versus potential gains because some of these time losses can cascade into larger problems.

While simulators are great training tools, there is no substitute for time on the water, which can lead to further overall development. Deadlines for each team’s second and final packages are fast approaching, and the sailors are eager to be on the water sailing, testing the designs and developing the skills required to sail these boats to their full potential. The first Prada Cup in April will certainly be the first true reckoning of concept, reliability and performance.

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American Magic’s 75-footer sits high in its cradle, on public display for the first time at the team’s base in Portsmouth, Rhode Island, on a crisp and blustery mid-September morning. From certain angles, and especially without its mast stepped, this vessel looks nothing like a sailboat. It’s more akin to a giant fuselage, a scow with a nosecone and an intricate blend of chines and hull rounds that curve around the foil-arm barrels before running straight for the wide, open transom.

As I step back and try to makes sense of its unique lines, I wonder about the deep technical debates that must have waged between the team’s primary designers, Marcelino Botin and Adolfo Carrau, and the Airbus wizards working alongside them. As a sailboat that’s essentially meant to fly, it stands to reason, it should look more like a plane than a yacht.

“It’s ugly when it’s out of the water,” one team member confides, “but it starts to look better once it’s in the water. When it’s sailing, it’s a thing of beauty.”

The parallels to flight are visible throughout the boat: from the complex contours of the foil arms themselves, to the razor-sharp trailing-edge flaps on the foils, and especially the rudder elevator, sculpted with amazing curved precision, into the shape of what looks like an albatross in flight.

It’s not a boat. It’s a three-dimensional work of modern art.

The up-close details of this, American Magic’s first of two boats, can only be described here, for the mandate upon entering the base for the private and confidential christening ceremony is, “No pictures, No video.” Such is the heightened and hyper state of confidentiality as challengers and defender alike reveal their first interpretations of the AC75 Class Rule. The spies are busy around the American Magic compound these days, with INEOS Team UK’s Ben Cornish and a fellow from Luna Rossa Prada Pirelli hovering and shadowing the team’s every move, observing from RIBs and poking cameras through gaps in the base’s privacy fencing to get a closer look.

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What spies undoubtedly report back to their bosses is that the New York YC’s AC75 Defiant is indeed unique, and already foiling into maneuvers after only two days on the water. As far as everyone can tell, the American challenger is one, or maybe two, steps ahead of any other syndicate.

And that alone is—perhaps—what has team executive director and skipper Terry Hutchinson choked up and struggling with his speech to more than a 125 teammates, suppliers, partners and yacht club patrons, as well as his mother and family looking on with admiration from the front row.

“I want to take a minute to acknowledge our team,” Hutchinson starts before pausing to take a deep breath and clear what’s welling up in his throat. “Look at what we’ve done. We have constructed a build facility in Rhode Island, we rebuilt the Mule, we launched and tested it in Rhode Island and then Pensacola. We’ve built four foils for the Mule, two masts, constructed and operating system inside the boat that, when on the water, is not distinguished between the Mule and the AC75. We built a D-spar section at Offshore Spars in Detroit, Michigan, for the AC75. We built two foils that are on display here for the AC75, and one rudder and one elevator. We designed and built an AC75 that represents roughly 76,000 manhours.”

Having logged 84 days on the water, Hutchinson says, he can look back on 19 months of high-stakes development and be satisfied with where they’re at: “To think we’d be at this point in the competition, you’d happily take it. But probably most importantly, we’re the first team to foil on an AC75.”

With a short history lesson and words of encouragement that follow from New York YC Commodore William Ketchum, the crane engine roars to life. Strops grow taught as sailors and shore crew take the reins of the 15,000-pound hull as it’s lifted from its cradles and swings out over water for Hutchinson’s mother, Patricia, to lead the official blessing.

With a successful smash of Mumm champagne on the robust carbon prod, the boat is lowered into the water, allowing guests a closer look at the deck and cockpit configuration for the 11 crewmembers that will race the boat. The foredeck is sparse, save for the bowman’s non-skid runway to the prod and the surprisingly small steel ball onto which the D-shaped mast will be stepped. From there, the deck slops down dramatically with a centerline ramp leading to the cockpit. Here, in the “trenches” are four forward-facing pedestals (Emirates Team New Zealand’s are transverse). The forward-most grinders, I’m told, will spend most of their time on their knees.

“That’s the point, confirms grinder and veteran Cup sailor Sean Clarkson. “We can’t see anything, but if we can see anything, then the wind can see us.”

The team’s coach, James Lyne, quantifies it as such: “The lower they can be the better the aero. A person standing up in 20 miles per hour of breeze is 4.5 kilos of drag.”

Following further aft, to starboard, is the stand-up office of dedicated foil trimmer, Andrew Campbell. On a carbon “desk” smaller than a clipboard are various buttons and a video screen that allows him to see what’s happening with the foils below the boat. He’s positioned to starboard at all times.

Behind Campbell is trimmer Paul Goodison’s work station, with a carbon L-shaped leaning post to wedge himself against, a tablet mount and a wired joystick controller to adjust the twin-skinned mainsail’s dynamic and complex systems, as well as the jib sheet. With batteries to control the supplied foil-adjustment system, Goodison has the collective power of all eight grinders.

For American Magic’s towering and lean helmsman, Dean Barker, there’s a leaning pad and a relatively small steering wheel on either side. He has a few buttons on the wheel, as well as custom foot buttons to toe tap. Even with his height, Barker, I’m told, can barely see over the front of the boat. Better visibility comes when the boat is at full tilt, however, because of its bow-down attitude.

During maneuvers, only Barker and Goodison will transfer from side to side. “There isn’t a lot of movement,” says Clarkson, “but that doesn’t mean there’s not a lot going on: you’ve got mast rotation, changing twists, and travelers, outhauls and all that.”

There are plenty of foot buttons alongside the pedestals, which Clarkson says is pretty straightforward. “It’s not complicated at all. You get used to it.”

Clarkson anticipates grinder rotations after what is expected to be 40-minutes races in Auckland, bringing fresh arms into every race. “The more power you have, the faster you’ll go and the more maneuvers you can do,” he says. “Last time, you couldn’t really race the boats like you wanted to because you didn’t have enough oil. This time, we only have to make the energy for the sails.”

In the busy days before Defiant‘s christening, the team reportedly conducted only one day of towing before stepping the rig and going full steam ahead with a high-speed flyby through the New York YC’s Rolex Invitational Cup fleet racing on Narragansett Bay. Spectator cameras and iPhones captured what one sailing team member describes as such: “Compared to the Mule, it’s really stable. Everything is just bigger. You feel the speed for sure. We hit maybe 37 knots and it was just starting to just feel a bit loose. Yeah. It gets going pretty fast.”

Once the invitation-only crowd disperses from the base, sailors and shore crew linger before returning to the day’s work list. There are more six-day work weeks and long days ahead as the team must make hay before packing up the entire operation in November and relocating to its winter training facilities in Pensacola. The next few weeks are critical for decisions to be made for Boat No. 2, which is not far behind in the grand scheme of things. As far as Hutchinson is concerned he’s happy where they’re at, stating as much in his opening remarks.

“When we thought about the name,” he says, “There was really only one word: defiant. It describes us as we go through this, with everyone coming to work with a purpose and a higher meaning to beat the guys that are out there behind us, to beat team new Zealand and to go to work, day in and day out, with a commitment to winning. We are on a great trajectory to bringing the Cup back to the United States.”

If anything, it’s good to be first.

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