Q7. A ship model of length 5.5 m has a wetted surface area of 4.65 m2 and is tested in water of density 1000 kg/m3. The test results give the values of residuary resistance for a range of model speeds as shown in table Q7.
(a) (i) Plot a curve of residuary resistance against speed for the model. (2)
(ii) Comment on the shape of the curve. (2)
(b) For a geometrically similar ship of length 132 m operating in sea water of density 1025 kg/m3 at service speed of 17 knots, the following data is applicable:
Appendage allowance = 6 %
Weather allowance = 12 %
Quasi-propulsive coefficient (QPC) = 0.71
Transmission losses = 3 %
Determine the shaft power required for the ship at its service speed. (12)
Note: frictional coefficient for the ship in sea water is 1.417
Speed is in m/s and index (n) for ship and model is 1.825
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