Model experiments were carried out on the performance of a rudder with parallel auxiliary foils attached to the vicinity of trailing edge of the rudder, which has the cross section of NACA 0018 or NACA 0020 with aspect ratio of 1.67. The auxiliary foils have arbitrary cross sections with high aspect ratios ranging from 5.00 to 8.33. Open water tests were conducted using circulating water channel to measure the lift, drag and moment of the rudder and further extended to flow visualization tests to research the streak lines around the rudder. Five types of auxiliary foils were tested locating at the discretely distributed nine holding points. The results showed us relatively high performance notwithstanding its simple structure.
