PURPOSE: To enhance the propulsion efficiency of a propeller and at the same time reduce the manufacturing cost of the device by a structure wherein the setting angle of fins located at the side, at which the blade of the propeller moves upward, are rendered to be constant, resulting in effectively generating rotating currents.
CONSTITUTION: The fins 12a2 and 12b2 located at the side, at which the blade of the propeller moves upward, are fitted in such a manner that the trailing edge of the fin is lower than the leading edge and the setting angle of the fin is kept constant throughout the entire length of the fin. The fins with constant setting angle can generate the rotating currents with opposite rotating direction to that caused by the blades of the propeller as effective as the fins twisted toward their tips can do. Consequently, the enhancement of the propulsion efficiency of the propeller and the reduction of the manufacturing cost of said device are resulted.
KAWASUE YOSHIMATSU
TAKEKUMA KATSUYOSHI
