| 摘要 |
In such a high lift twin-rudder system that: a pair of high lift rudders 1, 2 is arranged behind a single propeller 3 ; the respective high lift rudder 1, 2 has a top end plate 6, 7 and a bottom end plate 8, 9 at the top end and the bottom of a rudder blade 4, 5 ; the respective rudder blade 4, 5 is provided with a reaction fin 10, 11 , protruding from an inboard face of the rudder blade 4, 5 on a nearly same level with the axis of the propeller 3 , that is originated nearly from the leading edge portion toward the rear and has a fixed chord length; the reaction fin 10 of the rudder blade 4 that faces on the board-side where the propeller blades rotate in the ascending direction assumes a posture that makes such attack angle that the ratio of a forward vectored thrust to a drag, both produced by a propeller slip stream having a stream component in the ascending direction, becomes maximum; and the reaction fin 11 of the rudder blade 5 that faces on the board-side where the propeller blades rotate in the descending direction assumes a posture that makes such attack angle that the ratio of a forward vectored thrust to a drag, both produced by a propeller slip stream having a stream component in the descending direction, becomes maximum, the respective rudder blade 4, 5 is so constituted that a chord length is of 60~45% of a propeller diameter.
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