Cup fleet sails even closer to wind than we think

By Adam Gifford

The hammering Auckland's winds and waves have given the America's Cup challenger fleet this month shows how the teams are pushing the edge of technology.

Apart from the amount spent on carbon fibre and pricey metal alloys, millions of dollars have gone into software development to give boats that extra edge on the water that will pit them against Team New Zealand come January.

Team NZ's navigator, Tom Schnackenberg, gave a recent Computer Society breakfast an insight into why technology may have tripped up the Young America syndicate, whose boat almost repeated Australia's feat in San Diego in 1995 of racing vertically to the bottom.

Mr Schnackenberg said the formula for America's Cup-class yachts included three variables - length, plus the square root of the sail area, times the cube root of the displacement.

As the displacement has proved not to be the big factor the formula's designers thought it would, "if you save weight around the boat, you put it in the bulb."

For some boats, that may have meant shaving the carbon fibre hulls even more closely.

Mr Schnackenberg said Team NZ decided on the path it would take back in San Diego.

"One of our tenets is we want a reliable boat with good time between repairs. In 1992, the red boat didn't go for more than two or three hours without needing something fixed.

"We though that was wasteful, and we might be better to put more in the hull to improve safety margins and make it more reliable. The Australians [at San Diego] may have been pushing the envelope," he said.

A large array of specialist software has been developed for yachting, which Team NZ pushes to the limit on five SGI workstations and a large number of PCs.

Programs like VPP (Velocity Prediction Program) are used extensively to work out the tradeoffs needed, both at the design phase and in race modelling.

To design the hull shape, the team use Maxsurf CAD/CAM software from MSC Nastran, MicroStation to do the working drawings and SolidWorks for solid modelling, as well as MultiSurf to look at the overall picture.

Sails are designed with custom software developed by Mr Schnackenberg's company, North Sails.

Video cameras at the base of the mast record the sails in action for later analysis.

Mr Schnackenberg said that while teams would like the perfect sail for each wind type, the realities of racing meant versatility was crucial.

Xfoil was used to help design the keel, working out which shapes would offer least resistance through the water.

Good software was only part of the picture, he said. "Codes like this help us visualise and understand where we should be going."

Several years ago, a third-year student came to Mr Schnackenberg proposing a project to do computer model of sails.

"I said: 'Why not work on rigging - sails are boring and there are programs available.' He went away and wrote an analysis program for how to rig a mast, and he has since become a world expert in rigging."

Designers initially thought there was little to be gained in mast size or shape, until the New Zealanders turned up with a larger, stiffer version.

This regatta, some teams were seeing the mast as an extension of the sail.

Team NZ had gone a step forward, sitting down with its software and developing a new way of rigging it called the millennium rig.

Rather than a conventional rig with four spreaders, the black boats had rigging running at a diagonal from the top of each spreader through the mast.

"We've thrown away a spreader and improved safety margins," Mr Schnackenberg said.

Much of the wind, weather and water data collected in sailing was used for instrument calibration, which could play a crucial part of match racing, he said.

"In San Diego, Dennis Conner went from one boat to another after the defender series because he though it was faster, but he didn't know the machines.

"In the second race we came round the marker and gibed. On the video later we could hear voices on his boat saying,'the Kiwis have gibed' - they didn't know where the wind was going though the mark because they had not had time to get familiar with their equipment."

That Team NZ did not have to match-race to become the defender, but could practise each day with two boats, had significant advantages, he said.

When the two boats were sailing, they were exchanging on-board data into laptops, so the crews could get a better understanding of the racing environment.

"You can look at the log data later, but when you are doing tests you want to get answers right away because that way you remember things."