Class 2 (2nd Engineer) SC&S 📅 Nov 2022

Exam Question

(a) Describe the relationship between frictional resistance and (6)

(i) Ship speed

(ii) The wetted area

(iii) The surface roughness

(iv) The length of the vessel

(b) A ship 150 m long and 8.5 m draught has a rudder whose area is one sixtieth of the middle-line plane and diameter of stock 320 mm. Calculate the maximum speed at which the vessel may travel if the maximum allowable stress is 70 MN/m2 the Centre of stock 0.9 m from the Centre of effort and the maximum rudder angle is 35 degrees.

Reference Answer

Frictional resistance arises due to the interaction between the ship's hull and the water as the vessel moves. This resistance is caused by eddying water adjacent to the hull that is drawn along with the ship. The frictional resistance is given by:
$$R_{f\:=\:}f\:.\:s\:.\:v^{n}$$
Where:
f = Coefficient of friction

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