Sailed alongside a German Ballad for a while in the Kalmar Straight this summer. He had fitted a rubber ball, just larger than the drain diameter, on a cord leading up each drain and fixed in the cockpit end. Clearance to the ball, when hanging was about 1,5 to 2 cm. At speed the ball floated up and blocked the drain for backflow.
Simple and very effective solution to wet feet at whoopee speed!
