America's Cup: Patchy conditions in light air makes passing manoeuvres big task

Team NZ wing trimmer Glenn Ashby said it was all very well to catch up to the other boat, but passing them is more difficult. Photo / AP

Sailing is a difficult sport to get your head around at the best of times, but for casual observers tuning into yesterday's racing confusion reigned.

The light, fluky conditions on San Francisco Bay produced strange match racing scenarios in races 14 and 15.. The final downwind legs were especially frustrating for Kiwi fans as on both occasions Team New Zealand made incredible gains, only to immediately gybe away and lose ground again.

In the opening race, Oracle had a huge 500-metre lead on the final run home, but around the halfway point of the leg they sailed into a patch of lighter winds on the left of the course. When they slowly gybed back they were almost pointing directly back at the Team NZ boat which was ripping along on port gybe.

Just 25m separated the boats when they converged and for a moment it looked as though Team NZ were going to roll over the top, but the Kiwi boat gybed away and all of a sudden Oracle's lead had stretched to 400m again. As Team NZ drifted towards the boundary line, frustrated viewers threw their hands up in the air screaming, "What are they doing?"

Team NZ wing trimmer Glenn Ashby said it was all very well to catch up to the other boat, but passing them is more difficult.

"If you make a big gain you then need to convert that gain into potentially a passing manoeuvre. It's often really difficult to just follow a boat around the track when it's really dynamic and really shifty," said Ashby.

So Team NZ had little choice but to gybe away when they caught Oracle, but the problem was the wind inexplicably dropped out on them when they did. The instruments on board were reportedly showing just two knots of breeze and the tell-tales on the wingsail were pointing straight down, leaving the Kiwi boat drifting sideways for one excruciating minute until they found some breeze and were able to right themselves. While the minimum wind speed for racing is five knots, once the race has started is it is measured on a five minute rolling average, so any anomalies have a chance to level out.

Ashby said while it hindsight gybing away at that time proved costly, they needed to try to engineer something. "Decisions have to be made on board to make the gain and it's really difficult to keep attacking on days when it is really shifty and really puffy," he said.

The light, fickle conditions yesterday meant there were bigger gains and losses than seen throughout the regatta. In light winds at 12 knots windspeed the boats are on the point of foiling. So when a team sails into a bad patch of breeze, the boats drop off their foils and the loss isn't just a couple of knots in boat speed, but up to 10 knots difference.