Historically, it has been useful to provide improved rudders which have the capability of turning a water vessel in a short distance. A highly satisfactory rudder is generally considered to be one which can turn a boat through 90.degree. while traveling forward a distance of about 21/2 times the vessel's length.
It is known that when a maximum angle is exceeded by a rudder, burbling occurs along the rudder which results in a significant decline in rudder turning effectiveness. This burbling is defined as the separation and breakup of the streamline flow of water across the rudder, and consequent reduction in rudder lift. It is desirable, therefore, to eliminate, or at least delay, the onset cf rudder burble at higher rudder angles.
A number of conventional rudders have been disclosed. For example, in U.S. Pat. No. 4,515,101 by Akerblom there is disclosed a rudder having a lengthwise interior cavity which is divided into two smaller cavities to allow water to enter an upstream side of the rudder and through a hollow channel within the rudder and to exit the rudder through openings in a downstream side of the rudder.
Another rudder system disclosed by Easter in U.S. Pat. No. 2,996,031, utilizes a number of flanking rudders and steering rudders which include front and/or rear articulated portions for improving vessel maneuverability.
Another rudder system utilizing flanking rudders is disclosed in U.S. Pat. No. 3,181,492 by Hockett, in which there is provided a central vertical rudder flanked by left, right smaller vertical rudders which are joined to the central rudder by upper and lower horizontal fins. A further rudder system utilizing a flanking rudder is disclosed by Einarsson in U.S. Pat. No. 2,972,323, in which the rudder system has a central vertical rudder flanked by left, right vertical laminar members which are joined to the central rudder by transverse extending struts.
Other rudder systems include U.S. Pat. No. 132,991 to Thomas, which includes a pair of upstanding rudder sections connected between a pair of horizontal discs and supported above a second pair of lower upstanding rudder sections which are also connected between a second pair of horizontal discs.
U.S. Pat. No. 99,639 to Coleman pertains to a rudder system incorporating a vertical central rudder to which left, right vertical blade sections are attached to opposite sides of the central rudder in a parallel manner.
Additional rudder systems using flanking rudders have been disclosed by Horstman in U.S. Pat. No. 2,251,133, in which the flanking rudders are pivotally aligned in a parallel manner with the water slipstream in a non turning mode, and when turned in a 45.degree. angle, the rudders are axially aligned with each other to form a single rudder.
Furthermore, in U.S. Pat. No. 2,328,041 to Wellons, there is a rudder system including a central rudder flanked by left, right curved vanes which are connected to the central rudder so that when the rudder is turned, the vanes exclude water from approaching the propeller from one side, and direct water toward the propeller from the opposite side, to aid in turning the boat.
Another rudder system which is disclosed by Uecker in U.S. Pat. No. 2,910,954, utilizes a main vertical rudder having a forward rudder section which pivots independently of the main rudder.
Also, in U.S. Pat. No. 2,686,490 by Bencal, there is disclosed a rudder system utilizing a pair of vertical rudders which are interconnected by upper and lower horizontal flanges and which include a horizontal fin mounted between the vertical rudders near their upper ends.