To promote the generation of cavitation without increasing the drag and while having the durability by forming a recessed groove in a back surface of a propeller along a front edge thereof so as to promote the cavitation.
In each propeller blade 16 of a propeller 14, a vessel side surface thereof is formed as a back surface 17, and an opposite surface is formed as a pressure surface. Each propeller blade 17 is formed with a narrow and long recessed groove 21 as a cavitater along a front edge 16a of the propeller blade 16. The back surface 17 of the propeller blade 16 except for the recessed groove 21 part and the nearly whole surface of the pressure surface are formed into a smooth surface. With this structure, propeller efficiency is improved, and durability of the cavitater is improved, and projection of the recessed groove as a cavitater from the propeller blade is prevented, and increase of the drag can be prevented as much as possible.
SUMINO YOSHITANE
KUDO TATSURO
SANSHIN KOGYO KK