Stern duct

Abstract

Provided is a stern duct 1 including a duct body 11 being a single tube provided in front of a propeller 5 of a watercraft 100 around a stern tube 9 at a stern and having an axial direction thereof oriented in a watercraft longitudinal direction, and disposed at such a position and in such an orientation that pressure around a surface of the tube is lower on an inside than on an outside. The duct body 11 includes a slot 23 being a long hole which is formed along a circumferential direction of the tube of the duct body 11, through which an inner periphery and an outer periphery of the duct body 11 communicate with each other, and through which a part of a water flow flowing outside the duct body 11 is introduced into the duct body 11. In this way, it is possible to increase a thrust force and also enables easy adjustment of the thrust force without greatly changing the number of duct bodies and the outer shape of the duct body from conventional structures.