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Video - GB sailors enjoy mixed results
Ben Ainslie leads the standings in sailing's Finn class after claiming his third race win of the Olympic regatta.
Ainslie made a poor start to his Olympic defence coming 10th in his first race, but the 31-year-old has battled back to lead after six races.
And Team GB's women's Yngling crew maintained their lead after recording a fourth and a second in the day's races.
But GB's Stevie Morrison and Ben Rhodes suffered a bad day, falling from first to ninth in the 49er class standings.
Ainslie, who is attempting to become Britain's most successful Olympic sailor and claim his fourth medal, battled back from ninth place at the midway point to beat Brazil's Eduardo Counto in the first race.
That put him four points ahead of American Zach Railey, who had started the day five points clear.
Ainslie finished only 10th in race six but managed to maintain a one-point lead over Railey, who was seventh and eighth in the day's races.
"It was a good race in the first, but I would have liked to done a lot better in the second so that was pretty disappointing," said Ainslie.
"But still a long way to go, and it's good to be at the right end of the fleet. If you get stuck in the fleet like I did in that second race then it's hard to make the gains."
The British trio of Sarah Ayton, Sarah Webb and Pippa Wilson remained at the top of the Yngling class but have yet to win a race in the regatta.
They have 15 points after six races, three ahead of the Netherlands, who had a first and fifth.
Ayton said: "It was a really tricky day but we started off, four fleet races down, six to go, knowing that we had to put in a solid performance.
"It definitely was that, so we're feeling pretty cool now."
However, it was a disappointing day for Morrison and Rhodes, who had held a one-point lead over Italy after the first three races on Sunday but finished 14th in race four and 15th in the next two races to fall well down the standings.
They have 41 points after six races, 28 behind the first-placed Australian boat of Nathan Outteridge and Ben Austin, which finished third in race four before winning both of the next two races.
Bryony Shaw's first day in the RS:X women's windsurfing event sees her in third place after two races.
And Nick Dempsey has plenty of ground to make up in the RS:X men's category after placing ninth and 11th to lie in ninth place overall.