DieselShip's Online Content Library

Q7. A ship of length 140 m and breadth 18 m floats at a draught of 8 m in sea water of density 1025 kg/m³. In this condition the block coefficient (Cb) is 0.68.

At a speed of 15 knots the following data applies:

Delivered power  = 4720 kW

Quasi-propulsive coefficient (QPC) = 0.70

Ship correlation factor (SCF) = 1.18

Calculate the pull required to tow a similar model of length 5 m at the corresponding speed in fresh water density 1000 kg/m³.  (16)

Note:  The frictional coefficient to be used:

for the model in fresh water of density 1000 kg/m³ is 1.694

for the ship in sea water of density 1025 kg/m³ is 1.415

Speed in m/s with the speed index (n) for ship and model 1.825

Wetted surface area (S) = 2.57 √(DL )  (m²)