PURPOSE: To make it possible to reduce fluid resistance, by providing such an arrangement that a screw shaft having a wheel is screwed into the top end of an elliptic corss-sectioned shape columner member supported by metals at the stern of a ship, and a screw shaft is clamped and supported by an elliptic hinge hardware at the lower end of the columnar member.

CONSTITUTION: A threaded shaft 9 secured at its top part with a wheel 11 is fitted through a support hardware 10 and is screwed into a threaded hole in a threaded elliptic boss 2 which is secured to the top end of an elliptic or stream- line cross-sectioned shape columnar elevating shaft 1 that is slidably held by slide metals 5, 5' attached to the stern of a ship, and a holding pipe 7 for a screw shaft 6 is coupled to the lower end of the columnar elevating shaft 1 through an elliptic hinge hardware 3 which is secured to the lower end of the columnar elevating shaft 1. When the wheel 11 is turned, the screw shaft 6 is elevated due to the threaded engagement between the shaft 9 and the elevating shaft 1. Since the elevating shaft 1 and the hinge hardware 3 are elliptical, the fluid resistance thereof may be reduced.