DieselShip's Online Content Library

Q8. A ship of 25120 tonne displacement has a length of 140 m, breadth of 25 m and floats at a draught of 10 m when in sea water of density of 1025 kg/m³.

The ship’s propeller has a diameter of 6 m with a pitch ratio of 0.85. When the propeller is operating at 1.85 rev/s, the real slip is 32 % and the thrust power is 6200 kW.

The thrust power is reduced to 5000 kW and the real slip is increased to 34 %.

Assuming that the thrust power is proportional to (speed of advance)3, calculate EACH of the following for the reduced power:

(a) ship speed; (11)

(b) the propeller speed of rotation; (3)

(c) the apparent slip. (2)

Note: Wake fraction= 0.5 C_b – 0.05