Millions of dollars spent developing hydro-foiling technology by America's Cup teams may not be much use next year on the narrow San Francisco Bay course.
Images of Team New Zealand and Cup defenders Oracle up on foils during the testing of their AC72s has the yachting community abuzz.
Emirates Team New Zealand have reportedly clocked speeds of up to 48 knots, or around 85km/h, while Oracle skipper Jimmy Spithill has been a bit more coy on what data they were getting off the boat in their first few tentative blasts around the Bay this week.
What both teams are now investigating through their highly involved testing programmes is whether foiling - essentially being almost airborne by flying both hulls - is a viable tool to use in a match race.
Oracle chief executive Russell Coutts said foiling, as with anything, comes with a trade-off.
"Something might be faster, but it might compromise the manoeuvrability of the boat, so that's where the discovery lies - how usable is this technology on a race course," said Coutts.
The two teams yet to launch their AC72s - Luna Rossa and Artemis - are also expected to experiment with foiling. Artemis skipper Terry Hutchinson said his team would be "naive" not to look into it but was guarded about the potential effectiveness of foiling on the tight San Francisco Bay course.
"What Emirates and Oracle have shown is probably the right solution if you had 10 or 15 miles of race track. The trick will be if you have the space and the room to allow the foiling to work for you - I think the Bay is going to become quite small very quick," said Hutchinson.
Iain Murray, the head of America's Cup Race Management, said the competitors were all "very clear" they wanted three-miles legs (4.8km) at minimum for next year's races.
"I guess it's clear why they have been pushing for that now because with the boats foiling, the speeds are substantially higher than envisaged," said Murray.
Going by the speeds that have been reported, it is estimated it could take as little as five minutes to complete one leg of the course.
But, with a shipping lane to the east end of the course and the Golden Gate Bridge to the west, Murray said there is very little room to make the course any longer.
"We could probably get the legs out a little bit, maybe a few hundred metres, but not much," he said.
Moving the racing out of the confines of San Francisco Bay is not an option for event organisers. As part of their efforts to rejuvenate the America's Cup and make it a more fan-friendly event, they are intent on bringing the racing to the people. One of the most successful features of the World Series circuit, racing the AC45 catamarans has been the short in-shore courses, which allow crowds to watch the action along the sea wall.
With piers 27-29, which will house the America's Cup village next year, still under development, around 150,000 people flocked to Marina Green at the western end of the city to watch the last round of the world series in San Francisco. Bleachers were set up at the start and finish line, creating a stadium-like atmosphere.
"It was like being at a football match," said Stephen Barclay, the chief executive of the America's Cup Event Authority.
The makeshift venue was so successful, Barclay has decided to move the team hospitality areas for next year's event to Marina Green. To do so, he's had to renege on an agreement to provide hospitality facilities at the proposed area for team bases on piers 30-32, which is no longer going to be redeveloped for the Cup - much to the anger of Team New Zealand boss Grant Dalton.
This week's second round of the series is being operated a little differently, with organisers having to share their space along the Marina Green with Fleet Week - San Francisco's annual celebration of the nation's military. While they've had to compress themselves into a much smaller area in the marina, and shoehorn the racing schedule around the Fleet Week action, Barclay said the benefit is they will capture a record crowd for a live yacht race.
San Francisco authorities are estimating 500,000 visitors will be in the city this weekend, in what is being billed as the biggest weekend of events for the Bay Area. Along with the action on the water, the city is hosting the Bluegrass music festival, while the San Francisco Giants are at home for their first two national league division series playoff matches against the Cincinnati Reds.
"As well as being the largest crowd that has watched a live sailing race, there'll be half a million people spread out along the waterfront, and that will test the transport, the logistics, moving from site to site," said Barclay.By Dana Johannsen Email Dana