The Cup community is all a-bustle over what Team NZ is hiding

Team New Zealand’s two new generation yachts, NZL-81 and NZL-82 disappeared behind closed doors last week as rumours began circulating about a major design breakthrough on their hulls. Neither yacht has emerged since last Thursday. Given the intense regime of in-house racing and training that Team New Zealand has undertaken, the disappearance of the yachts suggests significant modifications are under way.

Since the launching of the two new yachts a couple of months ago, Team New Zealand has gone to enormous lengths to keep the hulls shrouded from view. While concealing the keels of America’s Cup Class yachts has become commonplace, Team New Zealand has taken the practice much further, to the extent of towing their yachts out to the Hauraki Gulf race area with skirts covering the entire hulls from deck level down.

Intense speculation has surrounded this practice as Cup observers tried to figure out if the team really had something to hide, or was going to great lengths for the sake of a psychological ruse. In recent days, speculation has grown that there is indeed something to hide and that it is a device aimed at gaining extra waterline length. Length translates to speed and designers look for every means possible to maximize the effective length of the hulls. Team New Zealand syndicate head Tom Schnackenberg, who is also co-ordinator of the Defender design group, has steadfastly refused to comment on any rumours about the underwater shapes of the two new yachts.

However, the yachts have been subject to intensive surveillance out on the Hauraki Gulf particularly by the two strongest Challengers, the Swiss-based Alinghi syndicate and the US-based Oracle BMW syndicate. At times, tempers have been frayed by what the defenders considered over-zealous efforts by their rivals to uncover their secrets. It is now understood that both Alinghi and Oracle BMW Racing have attempted to replicate Team New Zealand’s innovation and are working feverishly to see how effective it is.

In essence, the device amounts to a bustle at the stern of the yacht. During the 12-Metre era, a number of yachts had bustles, which, as the name suggests, is a bulbous protrusion under the stern section of the hull, extending from the keel to the point where the underside of the transom exits the water. The name derives from the fashion device adopted by Victorian women to project the backs of their skirts out from their buttocks. The effect of the bustle is to add volume at the stern section of the yachts. When the yacht heels under sail, the additional volume translates into additional waterline length and that translates into speed.

The device is an extension of similar thinking behind the double knuckle bows, first used by Team New Zealand in 2000 and now a common feature throughout the America’s Cup Class. Whereas the object of the bow feature was to add volume up forward and increase the length of the yacht when heeled, the bustle has a similar effect in the stern.

The difficulty from a design point of view is that the America’s Cup Class rule forbids discontinuities or hollows in the hull lines. A bustle, in conventional terms, implies a hollow, because the line of the bustle curves up from the aft end of the keel to the waterline and then immediately changes direction and flattens as it extends to the stern of the yacht. Therefore, an unconventional answer had to be found. It is understood that this was achieved by treating the bustle as a separate section, or appendage, which attaches underneath the boat. The America’s Cup Class rule limits yachts to two moveable appendages -- usually, but not always, the rudder and the trim tab. There is no limit on the number of fixed appendages, so this separate underwater element is apparently attached as a fixed appendage.

Judging from confidential interpretations, one of the key considerations would be that the appendage would have to attach to the hull within a zone 250mm on either side of the centerline (Interpretation No. 22). If the appendage extends wider than the permitted 500mm-wide attachment zone, the overlapping area may never touch the hull (Interpretation No.5), which suggests there must be a gap. Even under pressure of sailing, the appendage must not be able to deflect and touch the hull. Clearly, a gap between two underwater surfaces has the potential to create turbulence and drag, both of which are slow. So the structural challenge is to keep the gap as small as possible, plus create something very stiff, which won’t deflect while sailing.

Observers point out that Team New Zealand’s yachts at present may not be class legal. They are still in a development phase and may well be experimenting with concepts and theories that may be exaggerated, or outside the class rules. The crunch time will come on January 7, when Team New Zealand is required to unveil one or both of its yachts with a valid measurement certificate confirming it conforms to the class rules. If it unveils only one yacht, it is then obliged to race that yacht in the Match.

Ernesto Bertarelli, billionaire head of the Alinghi syndicate was asked to comment on Team New Zealand’s innovations. He confirmed the team was closely studying rule interpretations for hints of what is going on. “I think Team NZ is going to be very fast and we respect Team New Zealand greatly,” he said. “I don’t think they will be shy on talent or speed. However, at the moment we are not very interested in them we are just doing our own work.”