Model experiments have been conducted to investigate the effect of fitting two small wing rudders of stepped section to a typical high sped round bilge displacement vessel. These rudders, fitted as an addition to the normal steering rudder, are swung over to a prescribed angle as the vessel proceeds ahead to generate a region of low pressure with the hull producing, in optimum conditions, small reductions in resistance. However, these reductions are not maintained under propulsive conditions and no clear advantage has been seen over a conventional arrangement, defined as consisting of a centreline rudder and transom wedge.