Spain's Carla Munté Carrasco and Marta Munté Carrasco rose from third to first today at the 49erFX European Championships in the seaside town of Gdynia in Poland today.
The sisters enjoyed a second and a fourth place finish to move onto 49 points.
This meant they overhauled Norwegian leaders Helene Naess and Marie Ronningen, who finished fourth and 47th today to slip to 47 points for the regatta.
Great Britain's Sophie Weguelin and Sophie Ainsworth are now third overall just one point further back.
They placed eighth and 10th in two races today.
There has been no racing in the men's 49er event today due to a lack of winds.
Home sailors Lukasz Przybytek and Pawel Kolodzinski currently hold the lead.