Flow-modifying element, especially a rudder

Claim 1

A hollow water-flow modifying element for boats and ships, said element having leading and trailing ends and a rear end proximate said trailing end, said element comprising a pair of opposite side walls defining a space therebetween and having a pair of opposite, outer surfaces which are symmetrical in relation to each other and in relation to water flow when said boat or ship is moving forward on a straight course and with said element positioned such that said surfaces form substantially similar angles in relation to said course; wherein one of said outer surfaces forms a suction side and the other a pressure side of said element when said element is positioned at an angle in relation to said course; a central partition wall means for dividing said space into a pair of parallel, symmetrical flow passages extending in the direction of water-flow from the leading end to the trailing end of said element; water inflow openings in said element at the leading end of said element in communication with each of said flow passages on either side of said partition; water outflow openings arranged in each of said side walls in the rear end portion thereof; wherein any water flow induced by movement of said element in water and passing through said flow passages is symmetrically distributed through the outflow openings of said side walls when said element is moving forward on said straight course; wherein such water flow will be distributed predominantly through the outflow openings at said suction side of said element to modify water flow therealong when said element is set at an angle in relation to said straight course; and wherein said outflow openings are provided in vertical and horizontal rows in said side walls.