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Medals in the Olympic classes will be decided on Saturday in a final race featuring the top 10 crews from the qualification series.

Percy, 33, and Simpson, 32, and are at the head of the fleet again this week.

"We've all sailed here over the years but not in such a professional or analytical sense as we treat every Olympic Games," said Percy, who also won gold in the Finn in Sydney. "So we're here to treat Weymouth as a new venue and get used to the waters in a Star and the waters we're going to be racing on in 2012."

Goodison has won and European titles since his Olympic triumph in the Laser last summer, but he is not having it all his own way. After six of the 10 qualification races, the 31-year-old was languishing in 11th and has work to do to muscle his way into Saturday's medal race.

Wilson won gold with helm Sarah Ayton and fellow crewmember Sarah Webb in the Yngling in Beijing, but with the class now , she is racing with Saskia Clark in the 470.

"It's quite a big change but luckily I'm with Saskia who has got a lot of 470 experience so that's fast-tracking everything," said the 23-year-old. "We've got a lot to learn with both a new boat and me helming but it's exciting times for us."

In place of the Yngling keelboat is the , still for three sailors, but under a new matchracing format - boat on boat instead of fleet racing, with a round robin before the knockout stages.

It's designed to be more user-friendly for spectators, so they can see who is leading at any given time.

Lucy Macgregor and Annie Lush, who sailed with double Olympic champion Shirley Robertson in the ultimately unsuccessful Yngling campaign ahead of Beijing, have now teamed up with Allie Martin.

"It's a steep learning curve both on the matchracing side, sailing the Elliot and me helming for the first time," said Macgregor. "Obviously we're gunning for 2012 but it's one step at a time."

With Ainslie absent in the Finn class, Ed Wright has already wrapped up the World Cup series but he is facing stiff competition from Giles Scott to be top Briton in Weymouth.

In the men's high-performance 49er, the rivalry for 2012 is already hotting up. Rick Peacock and John Pink won world championship silver in July, while new pairing Paul Brotherton - Wilson's Yngling coach in Beijing - and Mark Asquith in Croatia earlier this month.

Athens bronze medallist Chris Draper and new partner Peter Greenhalgh, and Beijing duo Stevie Morrison and Ben Rhodes are also in contention in Weymouth.

"The 49er is a very competitive class," said Morrison. "The British are blessed with a lot of strong teams so at the moment it's all pretty tight.

"I guess it's the most fun boat to sail and it's fairly crash-and-burn sailing as well, so it keeps it interesting."

The men's Laser fleet sail downwind towards Weymouth

Competition for a place as Britain's Olympic representatives in the men's 470 class is also bubbling along nicely. Last year's world champions are doing battle with double Olympic silver medallist Nick Rogers and new crew Pom Green, as well as Luke Patience and Stuart Bithell, who won a surprise silver in their first outing together at the world championships in Denmark last month.

Windsurfer , winner of a bronze medal at the Beijing Games, is also in action in Weymouth but , who claimed bronze in Athens and recently won the world title, is missing through injury.

And what of Ainslie, Britain's greatest Olympic sailor? He's taking a break from the Finn to helm , Britain's America's Cup entry. But with political infighting clouding the date of the next competition proper - holders Alinghi and challengers Oracle are set for a in giant multihulls next February - there is still the danger of a clash with 2012.

Winning the America's Cup for Britain is Ainslie's last big goal, but it seems unlikely that he would spurn the chance of a fourth Olympic title given that it could come on home water.

Watch the action live on Saturday from 0900-1500 BST on the 91Èȱ¬ Sport website, with the major finals from 1200-1400 BST, also on the 91Èȱ¬ red button.