Ainslie overcomes light winds and heavy protests

The threat of green slime is back but Britain's Olympic sailors are leading two of the three events which have got under way on the pressure-cooker racetrack on the Yellow Sea and, in the third, the threatening presence of Ben Ainslie, up a place to second yesterday, is waiting to pounce.

"It sets the tone for the next two weeks," said the Royal Yachting Association's Lindsey Bell, adding that there was still a long way to go.

Ainslie knows that he is constantly having to watch his back in the heat of competition. In his first race yesterday he voluntarily took two penalty turns after an altercation with the American who is leading the Finn singlehander, Zach Railey.

"I thought I was crossing, but it was a classic port and starboard issue and he probably wanted to push the issue. It made life difficult for me, all the same." Railey finished second.

"I just want to stay out of trouble," he said, "but I ended giving up an awful lot of distance. Wherever I go anywhere near anybody they start shouting 'protest' at me. I want to keep my nose clean and so far I have done that."

Well enough to post a fourth, despite the twin penalty turn, and a first, which left him five points behind the American and 12 points ahead of third-placed Chris Cook of Canada. One of the pre-event favourites to rival Ainslie, Emilios Papthanasiou of Greece, again attracted penalty flags and was sent home. "I don't think boats should be disqualified," said a sympathetic Ainslie. "I think that's tough."

All of Ainslie's other top rivals are suffering on what was already a difficult track, prone to light winds and strong tides. Just a few days before the regatta, a virtual carpet of green, seaweed-like algae was cleared in a huge operation involving thousands of people. Yesterday, increasing numbers of clumps were appearing. "It's a bit of a concern," Ainslie said. "It's just about getting to the size when it catches on your centreboard or rudder or you have to sail round it."

For the Yngling trio of Sarah Ayton, Sarah Webb and Pippa Wilson a "really tough day", according to Wilson, ended with a fourth and a seventh being enough to extend their lead from five points to seven at the end of the first day.

They are still struggling to nail a commanding start but are fast enough to dig themselves out of trouble and a surge on the last leg of the second race turned a 14th out of 15 at the end of the first lap into a seventh made doubly valuable because the dangerous Dutch trio was 13th, pushed into third overall, one ahead of the equally fancied US team, skippered by Sally Barkow.

"We always kept our heads down," Wilson said, "in fact, I am a bit brain-fried. But, so far so good and every day we are just concentrating on the next race."

In front of a packed crowd who lined the harbour wall on a sultry Sunday, the 49er fleet made its acrobatic entrance with the performance dinghy's need for consistency equally imperative. A fourth, third and fifth gave Britain's Stevie Morrison and Ben Rhodes a one-point lead over the Italian brothers Pietro and Gianfranco Sibello, but this is the only scheduled 16-race series – the rest are 11 – and Morrison was in reflective mood. "We just tried not to freak out and not forget the basics. All we did today was worry about doing the right things at the right times. We've just got to go and do the same tomorrow."

Today sees the pace of the schedule pick up even more as four more classes – men's and women's 470 dinghy and men and women windsurfers – join the fray. But there remain concerns that the winds may be even lighter than yesterday's eight-knot south-easterly.