At 20kt you have 20 per cent more lift than at 18kt (400 tops 324). Perhaps you can encourage more lift


from the foil by moving the wing to a more horizontal position, or letting the boat heel more, who knows. But once touched down there is nothing for it but to put the bow down and hope for a gust before you end up sailing to and fro across… or even the wrong way down the course. Watching the boats sailing in Auckland the boats are changing heading by tens of degrees as they fight to stay on the foils. No one seems very confident that a hull touch- down will be easy to shrug off. All the training so far has been ‘unop-


Auckland on YouTube through the prism of my time spent sailing and designing. This spectator’s sensation has become


part video game with perfect graphics, and part model yachting with better sound effects. There is no sense of crews working hard to get the best out of the boat, nor wrestling with elements and equipment. They are all hidden away from the wind. And the viewer. Some will counter this by saying sports


like Formula One have altered their offering to chase eyeballs. But Formula One has not really changed its offering for 50 years. The tracks are the same, Spa, Monza, Silverstone and so on. The fundamental driver’s experi- ence is the same as the petrol head fans have in their car; a wheel at each corner, a steering wheel, accelerator and brakes. It feels as if there is no problem that


can’t be solved by employing complexity. The current AC75 class rule runs to 60 pages and even includes a formula for calculating the thickness of the boundary layer. Given that the Little America’s Cup in C-Class catamarans has run very well for half a century using a rule that fits on one side of A4 (letter) paper this all starts to feel a bit self-defeating fin de siècle. In the hope of being more attractive to


broadcasters and to grow an audience the Cup has abandoned its traditional open water courses for short, sharp stadium racing in impossibly expensive and esoteric yachts. Originally conceived as a ‘friendly competition between nations’ it has become an aggressive competition between multi - nationals. We are surely in ‘just because you can, doesn’t mean you should’ territory. Back in Auckland Harbour the die is


cast in terms of hardware and software systems. While there are obvious differ- ences between the boats it is hard to say that any team looks to have stolen a march on their competitors in the way that ETNZ did in Bermuda, most obviously with their cyclor grinding system. The AC75s seem fast, manoeuvrable


and well under control. As to the boats themselves, it is somewhat a case of beauty (Prada and American Magic) and the beasts (Ineos and ETNZ). I don’t think there is much to choose between the boats. The beasts’ pronounced long centreline


skegs signal a full commitment to


maximising aerodynamic efficiency, and the prospect of lower drag during a minor touchdown. Neither of these is game changing. In any event neither American Magic designer Marcelino Botín nor Prada owner Snr Bertelli would feel aesthetically able to sign off on a brutalist Ineos and ETNZ approach. Looking first at the aerodynamic sealing


effect of the skeg, it is a very low aspect ratio feature, in other words it doesn’t really extend far below the hull. As far as the performance of the boat goes, ride height is the key performance driver, detailed topo - graphy a distant second. If you can fly with the bottom of the hull a few millimetres above the water, that’s job done, skeg or no skeg. If you can’t achieve this level of ride height accuracy, then the more aggressive skeg may provide some mitigation against excessive vertical motion. Recently we have seen the boats sailing


in marginal foiling conditions and getting the boat up on the foils and holding it there through manoeuvres clearly has its chal- lenges. The catamaran sailors in the last Cup faced these issues, but they were helped in two ways: firstly, the buoyancy arrived on a long, slim hull and delivered a helpful dose of righting moment; secondly, the solid wing sail could deliver much more power than the soft sail rigs we see now. The monohulls will be much less toler-


ant so finding a wind hole and touching will quickly cut your speed in half, so a mid-race spell using buoyancy looks like a sure way to lose the race. Can the skegs mitigate this effect? The dynamic lift from the bottom of the skeg will not be of much help in stopping the hull dropping back into the water – it just doesn’t have enough angle of attack. But the long skeg can support about half of the boat’s weight before the flat bottom starts to hit the water and the extra wetted surface starts to increase fast and drag you backwards. Perhaps this parcel of buoyancy


wrapped in a small amount of wetted area will give the helmsman and trimmer a second or so’s grace to arrest the fall. But in the end there is only one solution to get back flying: more speed. Remember foil lift changes with the square of the speed.


posed’, as required by the Protocol, which prohibits not only inter-team co-operation but also a team using two boats together. How might things change when there are two teams on the pitch at once? The courses are very short, a windward


leg 1.1 to 2.2nm long, raced in a corridor that’s 0.8nm wide. To put this in my local context the course fits easily between Hamble Spit and Hythe Pier in the Solent. There is now a conventional start to wind- ward from the centre of the course. Let us imagine how the race will go. Hit


the line on time at 30kt and 60 seconds later you are at the left-hand boundary. You tack, it is two minutes to the right- hand boundary, two more tacks and you are at the weather mark. All quite straightforward if there is no


opponent, and you are up and foiling at the gun. But what will happen when the skippers must match race each other? Back in the day teams would spend weeks per- fecting their pre-start and dial-up tech- nique, a feature that was lost with the shift to reaching starts. Will there be a return to the dial-up


given the social distancing that will be needed to protect the foils? In the pre-start is there an opportunity for one boat to gain control over the other? The start sequence is only two minutes


long and with such high boat speeds can you ever ‘engage’ your opponent in the traditional match racing way? Can one boat avoid engagement and just choreo- graph a Vanderbilt start to cross the line at full speed? Given a decent breeze and a modicum of confidence in your boat speed, perhaps this is the way to go. In marginal conditions, where boats will


touch down during manoeuvres or due to missed timings, there is a danger that your opponent could get in a controlling posi- tion and force a situation where you can only take off after he does. From there you can only be on the back foot, having to tack before the boundary to get clear air, and thus getting out of sync with the game of pong between boundaries. I am intrigued, no one has seen a race


between these boats. Perhaps the teams of artificial intelligence experts have it all worked out and we will see something extraordinary and gripping. I do hope so.


SEAHORSE 49


q


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