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The America's Cup boats to be used on the edition of the event are unlike anything we have seen before. They might be officially sailing craft but they behave in some remarkable ways.
There are plenty who argue that this technology is so far beyond the bounds of what most people consider sailing as to be an entirely different sport. American Magic hit an impressive Topping the knot barrier used to be the preserve of extreme speed record craft and kiteboarders.
A World Speed Sailing Record was set in of Such records are set by sailing an average speed over the course of m, usually over a perfectly straight, flat course in optimum conditions. Perhaps even more impressive, in the right conditions when racing we have seen some boats managing 40 knots of boatspeed upwind in around 17 knots of wind. That is simply unheard of in performance terms and almost unimaginable just three or so years ago.
Related to the speeds the boats are sailing through the water, particularly upwind, is the wind speeds the sailors will feel on deck. When sailing, the forward motion affects the wind we experience onboard, known as apparent wind. Roll down the window and stick your hand out of it and there will be 50mph of wind hitting your hand from the direction your car is travelling.
The teams are there, the boats are there, and finally after two months of AC75 racing in Auckland, for the�. So when an AC75 is sailing upwind in 18 knots of breeze at a boatspeed of 40 knots, the crew on deck will be experiencing 40 knots of wind over the decks plus a percentage of the true wind speed � depending on their angle to the wind.
The AC75 crews might be sailing in only 18 knots of breeze � what would feel like a decent summer breeze on any other boat � but they experience winds of around 50 knots. To put that into context, that is a storm force 10 on the Beaufort scale! Once up on the foil, everything to windward of the leeward foil generates righting moment. By doing away with the keel entirely, the design is now like nothing we have ever seen, particularly when it comes to how dynamic the power transition is between foiling and not foiling.
The boats are designed to foil on the leeward foil, with the windward one raised to help increase righting moment: to help balance the boat. This means that when the AC75 is not foiling they are extremely tippy � much more so than most other boats of the same size.
Essentially, when the wind catches the sails, the boat wants to fall over as there is too much sail area for the amount of weight underneath the boat � something a lead keel usually counters on a yacht or keelboat. Once the boat is up and on the foils, however, that all changes, as everything to windward of the single foil in the water balances the sails. That means, the hull, the crew weight, the sail and rig weight, and the windward foil, all work to counter the sails. What all this means is that the boats go from being extremely tippy, to hugely powerful in just the few seconds it takes to get up on the foil.
Then immediately [once they lift off] you have more stability than, well, take your pick, but certainly more righting moment than something like a Volvo 70 with a big canting keel. With lift created to windward by the foils, it is possible that the boats can sail diagonally to windward.
With the AC75 sailing on its foil, drag is dramatically reduced, vast amounts of power can be generated and so speeds rapidly increase. But the foils can serve another purpose too. In order to be able to lift each foil out of the water, the foil arms must be able to be raised and lowered.
The further out the leeward foil arm is canted � essentially more raised � the closer the AC75 flies to surface and, crucially, the more righting moment is generated as the hull and rest of the boat gets further from the lifting surface of the foil. There is another positive to this: as the lifting foil is angled, it produces lift to windward, which can force the boat more towards the wind than the angle it is sailing.
As the foils work to provide stability to the boat when it is stationary both foils are dropped all the way down to stop it tipping over and to provide massive amounts of righting moment, they are incredibly heavy.
A pair of foil wings and flaps excluding the one-design foil arm which attaches them to the boat and lifts them up and down weigh kg.
To put that into perspective, the entire boat itself with all equipment but without the crew weighs between kg and kg. It is partly due to this that you will see some teams with bulbs on their foils. If you decide to go for a skinny foil wing which would be low drag and so faster then there will not be enough volume to cram sufficient material in to make the foil weigh enough. So some teams have decided to add a bulb in order to make it weigh enough but to also keep a less draggy, slimmer foil shape.
As with everything on the AC75, the mainsail is a relatively new concept. It consists of two mainsails which are attached to both corners of a D-shaped mast tube. This has the effect of creating a profile similar to a wing. But there are drawbacks with a wing: they cannot be lowered if something goes wrong and require a significant amount of manpower and a crane to put it on or take it off a boat.
One reason a wing makes for such a powerful sail is that the shape can be manipulated from top to bottom fairly easily with the right controls. With the AC75 the designers wanted a sail that could have some of this manipulation, produce similar power but could also be dropped while out on the water.
In addition to the usual sail controls, within the rules, the teams are allowed to develop systems for controlling the top 2m of the mainsail and the bottom 1.
What this means is that the teams are able to manipulate their Mini 12 Sailboats For Sale 50 mainsail in a number of different ways to develop power and control where that power is produced in the sail. But it also means that they have the ability to invert the head of the sail.
The advantage here is that instead of trying to tip the boat to leeward, the very top of the sail will be Sailboats For Sale Vancouver 90 trying to push the boat upright and so creating even more righting moment. The disadvantage is that it would come at the cost of increased aerodynamic drag. Each team has incredibly powerful Computational Fluid Dynamics CFD software packages and simulators in order to try to understand the various gains and losses.
To make these simulators and computer projections as accurate as possible each team has been getting as much data as they can over their three year development cycle. They even have some Mercedes staff out with the team in Auckland assessing their data. So you are looking at s of plots that we can delve into [per race or training session].
Skip to content �. Photo: Emirates Team New Zealand. Every month we have inspirational adventures and practical features to help you realise your sailing dreams. Build your knowledge with a subscription delivered to your door.
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