Page 265 - Introduction to Naval Architecture

250 PROPULSION

Figure 9,24

This analysis process is illustrated in Figure 9.24, and leads to the
power needed in calm seas with no natural wind. This is usually the
condition for which the required ship speed is set down in the contract
and which is aimed for in the speed trial conducted on completion of
the ship. In service the ship will seldom be in these conditions. For
more realistic powers and speeds allowance must be made for the wind
resistance on the above water form and the effects of waves on the hull
resistance and propulsor performance. This involves assessing the
average conditions a ship is likely to meet or the range of conditions
and their probability of occurrence.

References
1. Standard procedure far resistance and propulsion experiments with ship models. National
Physical Laboratory Ship Division Report No. 10.
2. Carlton, J. S. (1994) Marine propellers and propulsion. Butterworth-Heinemann.
3. Gawn, R. W. (1953) Effect of pitch and blade width on propeller performance.
TINA.