Four years ago at the Beijing Olympics, Great Britain had a lot of success in sailing events, winning four of 11 gold medals.

Now with the sailing events in their own waters, the British are again among the favorites for many of the races, which will be held in Weymouth Bay and Portland Harbour.

Sailing events have changed over the years, and this summer's games are no exception. As usual, the International Sailing Federation picked the classes for this year's Olympics and include single-handed, double-handed and triple- handed disciplines.

Events include men's and women's 470 (two-person dinghy), men's and women's RS:X (windsurfer), Star (men's keelboat), 49er (men's skiff), Finn (men's heavyweight one-person dinghy), Laser (men's one-person dinghy), Laser Radial (women's one-person dinghy) and women's Elliott 6m.

All but the women's Elliott 6m are fleet races, meaning the boats contest a series of races -- 15 for 49er, 10 for the others. Points are awarded on an ascending basis (first place gets one point, second place gets two), and are totaled after the series of races, with the points from the worst performance discarded. From there, the top 10 athletes or crews advance to the medal race, where points are doubled. Medals are awarded based on the points total after that race.

The women's Elliott 6m is a match race featuring a round-robin stage among the 12 crews. The best eight teams advance to an elimination stage.

Ben Ainslie headlines Great Britain's team, as he is the country's most decorated Olympic sailor with three golds and a silver. He was selected to compete in the Finn, which he won at the 2004 and '08 Games.

Iain Percy and Andrew Simpson also return to defend their '08 gold medal in the Star class for Great Britain. Additionally, the duo won the world championship in the event in 2010.

Paul Goodison took gold in the Laser class in '08, and is again competing in the discipline for the British. Former windsurfer bronze medalists Nick Dempsey ('04) and Bryony Shaw ('08) will also represent the host nation, along with the 2010

"The mix of experience we have with the six Olympic medallists, one Olympian and four first-time Olympians provides an exciting balance that will hopefully deliver the required results in 2012," said Stephen Park, Great Britain's sailing team leader.

The United States team is headlined by a highly competitive boat in the Elliot 6m, led by Anna Tunnicliffe and crewed by Molly Vandemoer and Debbie Capozzi. Tunnicliffe was the only U.S. sailor to win gold in '08, competing in the Laser Radial.

But she will be going for another gold with a crew that won women's match racing at the 2011 world championships. Tunnicliffe's boat only qualified for the Olympics after coming out victorious at a hotly contested Olympic Sailing Regatta in May.

"The US Olympic Trials is the hardest regatta to do in the world," said Tunnicliffe after that victory. "Coming into the Games, we knew that whichever team won here is going to the Olympics and is going to win gold."

Additionally for the United States, Zach Railey returns to compete in the Finn. He won the silver in the discipline at the Beijing Games. His sister, Paige Railey, represented the U.S. in the Laser Radial, an event for which she won the bronze medal at the 2011 world championships in Perth, Australia.

The crew of Mark Mendelblatt and Brian Fatih also earned a bronze medal at worlds, and will compete in that event for the US in London.

Australia will likely have a strong Olympic team, four years after it picked up three sailing medals, including two golds.

The Australians were impressive at last year's worlds, winning gold medals in the men's 470, Laser and 49er.

Tom Slingsby, a five-time world champion, heads the team in the Laser class. He had high hopes going into Beijing before finishing a distance 23rd, but is back to battle Goodison.

Additionally, Australia hopes for medals from world champion crews of Mathew Belcher and Malcolm Page in the men's 470, and Nathan Outteridge and Iain Jensen in the 49er class.

A pair of former Olympic gold medal winners will team up for the Aussies in the women's 470. Elise Rechichi, part of the winning team in Beijing, is racing with Belinda Stowell, whose team took first at the 2000 Olympic Games in Sydney.

Competition will run from Sunday, July 29 through Saturday, Aug. 11. Finn and Star will be the first disciplines to award medals -- on Aug. 5 -- while women's match racing will be the final event to be determined.