A modern AC catamaran is traditionally steered using the rudder. These are connected to the steering wheel. But in addition to the pure direction, the helmsman also has to regulate the altitude, position and stability of the cat. This is done by pressing a button or other input options on the wheel. These send signals to the control valves of the hydraulics, which then adjust the foils accordingly (see article Foil mechanics).
So it can be set so that one press means an angle change of half a degree. This signal is sent to the valve and electronically controls how long it has to be open before half a degree is reached. The vertical control of the cat is done digitally for some teams.
The Oracle Team US steering wheel with integrated rotary handles
Various teams reported 120 to 200 helmsman inputs per minute, Team Land Rover BAR reported 1200 during a 20 minute race. This step-by-step adjustment is a simplification for the helmsman. If it were to take place in the same way, i.e. the angle of attack would change as long as the helmsman held the button down, he would have to visually check via displays when the desired position has been reached. That would distract him, especially since the speed of adjustment also depends on how fast the catalytic converter is, i.e. how much pressure there is on the foils and how much pressure there is in the hydraulic system.
The Land Rover BAR steering wheel with integrated paddle shifters
With this "bucking method", on the other hand, he can count the inputs and draw conclusions about the angle of attack. Oracle Racing introduced this system at the previous Cup and thus secured a great advantage for itself.
Story about the creation of the Land Rover BAR wheel
However, Oracle Team U has now published pictures and videos of its bike, which has two twist grips like motorcycles. According to his own information, the helmsman Spithill could control it analogously. As long as he turns the handle forwards, the Kat sinks, if it turns backwards, it rises. However, this variant could also be a "jerking method", only that Spithill does not have to press buttons, but rather rotates the foils accordingly for a certain degree of adjustment.
Helmsman Jimmy Spithill, Oracle Team USA, explains his steering wheel with motorcycle handles
Land Rover BAR has also integrated rocker switches, borrowed from the automotive sector, into the wheel, which can even be operated when the helmsman changes grip variants.
Suspension on an Oracle prototype
How exactly the transmission of the signals to the foil valves is carried out by the teams is kept strictly confidential.
However, computer-aided control and electronic feedback to the helmsman about the position of the foil are not permitted.
Hydraulics - power from arms or legs
All energy for the mechanical systems on board must also be generated on board. These systems are operated using hydraulics. With the exception of the New Zealanders, all teams use two grinders each, which can be cranked by up to four men. The New Zealanders, on the other hand, have four pedal systems integrated into each fuselage. Instead of using the arms, they use their legs to crank.
View into the cockpit of an Oracle prototype
In both systems, the rotation of grinders or pedals drives hydraulic pumps, which provide the necessary pressure on hydraulic cylinders distributed everywhere. These cylinders adjust the individual components either directly or via line connections.
Only three energy stores for hydraulic pressure are allowed: one each for the angle of attack of the swords and one to move the swords up or down. These memories are a concession to the competition dynamics. A maximum of hydraulic pressure is required, especially in maneuvers, because most of the adjustments are made. The crew has to change the sides of the hull and at times cannot crank, there would not be enough pressure available in these important phases, power turns completely on foils would hardly be possible.
Challenge: Fitness expert Ross Edgley vs. Land Rover BAR sailor Neil Hunter
Each team would then have to consider whether it can afford a turnaround or not. With partially stored energy, however, this problem is defused. Nevertheless, the energy storage must be topped up after each maneuver.
Depending on how much energy the team can generate and how much energy the adjustment systems require, this is a limiting factor for maneuvering behavior. For example, how many turns can be made in a row or how often the foils can be fine-tuned.
With their leg-powered pedal system, the New Zealanders can generate around 40 percent more energy than the other teams with their arms. In addition, the position of the crew members is said to be aerodynamically more favorable than with standing grinders.
Impressions from the brutal training at Emirates Team New Zealand
However, it takes a little longer to take this position or to change, so the crew is less agile. This disadvantage was hardly noticeable during the first training runs off Bermuda. In maneuvers, only two "cyclists" change positions at the same time on the other side of the fuselage. The other two remain seated and can thus generate as much power during the maneuver as three men on the other teams' grinders.
Often three men change sides at the same time. They are back in position faster than if they had to get off and on their bikes, but with the New Zealanders one more person stays seated. The advantage with the New Zealanders is that they ensure permanent pressure generation. Instead, after the maneuver, they have one more man sitting down leeward for a longer period of time.
A new installation was discovered at the defender's two days ago, a bicycle behind the helmsman. This means that the New Zealanders are no longer the only ones who rely on wheel drive. However, this change at Oracle Team US probably has a different background than the New Zealanders.
However, the higher energy supply is only one reason why the New Zealanders rely on bicycles. With them, the helmsman and foil trimmer functions are at least temporarily shared. While in all other teams the helmsman sets the direction of the cat as well as the flight attitude different control systems on the bike, with the New Zealanders helmsman Peter Burling is mainly responsible for the steering. Most of the foil adjustment is done by his former 49er pre-crew Blair Tuke, who sits on the front wheel, directly above the foil. Who needs free hands for this, which he would not have on a grinder, this was another reason for the New Zealanders to get the crew on wheels. However, this division of tasks requires an extremely good coordination of both active players, which is only given at Burling / Tuke through their joint 49s.
At Oracle Team US, helmsman Jimmy Spithill is responsible for both course and attitude. But a bicycle was last seen on this cat too, behind the helmsman. It is apparently mainly used for weight trimming on downwind stretches. There it is important to have the weight aft. This trim can also be achieved by adjusting the T-foils on the rudder, but this creates more resistance on the foil.
Tactician Tom Slingsby sits on the aft wheel, but on closewind courses he is fourth from the front on the grinder as usual, because on this course it is better to have the crew weight a little further ahead.
The fact that Slingsby is sitting on a wheel aft is very likely less to do with the increased force he can generate with the pedal, but more to do with the limited space that is available there. A grinder would take up more space than a wheel.
Oracle Team US does not seem to be copying the New Zealanders' pedal drive, but is simply testing a new trim variant.