Exam Question

(a) The residuary resistance of a 1/25 scale model of a ship is 7.68N when tested at 1.646 m/s in fresh water of density 1000 Kg/m3. The frictional resistance of the ship at 12 knots in sea water density 1025 kg/m3 is 148KN. Frictional resistance can be assumed to vary wild speed to the power 1.825

Calculate the effectie power (naked) for the ship at the speed currespon ding to the model test

(b) The following additional data apply to the ship operating in service aat the curresponding speed calculated in (a) with a propeller having a pitch of 4.8m.

Appendage and weather alowance = 24%

Quasi-propulsive coefficient (QPC) = 0.71

Propeller speed = 1.85 rev/sec

Taylor wake fraction = 0.3

Propeller thrust = 650kN

Calculate EACH of the following

(i) The torque delivered to the propeller

(ii) The propeller efficiency

(iii) The real slip ratio