Going in for the keel

By TERRY MADDAFORD

Big is not necessarily better. That is how Team New Zealand obviously saw it when opting for the revolutionary keel they unveiled on NZL82 on Tuesday.

Yesterday they revealed an even more extravagant development on NZL81 - the trial boat which will take only a bit-part when the America's Cup fleet heads out for racing tomorrow.

In pulling the skirts off NZL81, Nick Holroyd, who heads the appendage development team, revealed a submarine-like bulb on the keel. A little over a metre longer than the bulb on its younger sister, the new bulbs are about "half as long again as NZL60" - the boat which beat Prada 5-0 in the 2000 cup.

By going with the bulb they have on their race boat, Team New Zealand still have a bulb "substantially longer than Alinghi have gone with".

The bulb is a hefty object - about 80 per cent of the maximum weight of 25 tonnes allowed for these America's Cup class yachts.

The longer bulbs, designed by Holroyd working alongside designers Tom Schnackenberg, Clay Oliver, Mike Drummond and Andy Claughton, were the result of wind tunnel and other testing in the United Kingdom.

"It is a computer-driven design and part of the appendage package I'm responsible for," said 35-year-old Holroyd, who was born and bred in Auckland, attended St Kentigern College and spent time in the UK before joining Team New Zealand in 1997.

"My decisions on the shape of the bulb are ultimately reflected all over the boat. We tested a bunch of bulb shapes in late 2001 before coming up with these."

Of suggestions bigger bulbs mean more drag, Holroyd said: "There are different sources of drag. As you lengthen the bulb you have more wetted surface. But that also means a different frontal area which, in turn, means less pressure drag."

While the shape and weight of the bulbs on NZL81 and 82 are "pretty similar", the race boat's bulb is "slightly flatter", he said.

According to Holroyd, the keel is a bit like a Meccano set.

"The wings come off, so do the fins," he said. "The wings this time are identical to NZL60, the fins are slightly different.

"Obviously we have taken a pretty bold step when compared with where we were with NZL60. You are always looking for the optimum in a mathematical sense.

"You are always looking across the fleet at a regatta like we have had here for good ideas," said Holroyd. "For the first 18 months after the last cup we developed the software tools from which we came up with these new design ideas.

"But, with any new ideas, you have to retain your objectivity. While you might be convinced you are right, you then must work closely with the rest of the design team in confirming that."

For the first couple of years, Team New Zealand spent much time in straight line sailing to test one shape and against another.

Tomorrow Holroyd will be among those holding their breath to see whether they have got it right. After all, there is no turning back.

nzherald.co.nz/americascup

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