Full Scale Experience Relating to the Propeller and Its Environment

The modern ship is generally the subject of a number of calculations and studies in an attempt to establish both its performance and vibration characteristics prior to the commencement of construction. However, these calculations depend for their accuracy and interpretation on information gained from full scale measurement and correlation exercises on previous ships. It is therefore, the aim of this paper to present some of the full scale experience and conclusions relating to propeller problems which has been gained from the many investigations undertaken by Lloyd's Register of Shipping. Among the subjects discussed are the influence of the hull after-body on the wake and its consequent effects on propeller induced excitation of the hull and shafting systems, propeller cavitation and full-scale experience in the use of highly skewed propellers as a means of reducing propeller excitation. Comments are also made on service experience with flow correcting devices. The problems discussed are not peculiar to any one class of ship but have been found to manifest themselves across a broad spectrum of ship types. It is upon this experience that the comments in the paper are based.