Stern duct, stern attachment, method of designing stern duct, and ship equipped with stern duct

The present invention provides a stern duct, a stern attachment, a method of designing a stern duct, and a ship equipped with a stern duct. In a stern duct (10) mounted forwardly of a propeller (3) which is mounted at a stern (2) of a ship hull (1), a duct body (11) is formed in an arc shape in an angle range of 90o to 140o; the radius (Rr) of a rear end arc portion (11r) formed at the rear end of the duct body (11) is not more than 50% and not less than 20% of the radius of the propeller (3); and, in a forward view of the ship hull (1) from the rear, the duct body (11) is mounted to the stern (2) using a support means (12) so that a duct center line (Yd) of the duct body (11) is inclined in a direction of rotation of the propeller (3) with respect to a propeller center line (Xv) in an upper/lower direction of the propeller (3), whereby the hull efficiency can be improved without an increase in the resistance of the ship hull (1) even with the duct body (11) attached to the ship hull (1).