Abstract: A steering device which is particularly suitable for the automatic steering of a sailboat on a preselected heading relative to the apparent wind incorporates a hydrodynamic servo device. An oar member which forms the hydrodynamic servo is mounted in a support housing and positioned in the water behind the boat for both rotational and pendulous motion. Also mounted in the support housing and positioned in the water behind the boat for solely rotational motion is a rudder member which is coupled to the oar member to provide a rotational input thereto in response to steering control signals. These steering control signals may be provided by a dual axis wind vane which generates an output when the heading of a sailboat relative to the apparent wind changes. When the oar member is rotatably driven from its neutral position (i.e., the position where the sidewise hydrodynamic forces balance each other out), the water force pendulously drives this member substantially sidewise.