A method for determining the free-stream characteristics of ship skeg-rudders

Article type: Research Article

Authors: Molland, A.F.

Affiliations: University of Southampton, U.K.

Abstract: A modified lifting line theory is developed which supports the form of skeg-rudder experimental free-stream data obtained previously. It is demonstrated that satisfactory predictions of the form of the spanwise loadings for different skeg and rudder angles can be made using lifting line theory with the effect of the skeg being incorporated as local incidence reduction and the effects of the midspan and tip trailing vortices being incorporated as twist corrections to the local incidence. The correct magnitude of the distributions is obtained by applying suitable empirical corrections. Chordwise centre of pressure is derived empirically. The theory is used to provide a limited extension to the experimental data. Predictions using the modified theory show that, for fixed aspect ratio and taper ratio, changes in the skeg depth can have a significant influence on the production of lift whilst changes in the skeg chord and rudder sweep have a marked effect on the stock position, balance area and hence torque.

DOI: 10.3233/ISP-1985-3237001

Journal: International Shipbuilding Progress, vol. 32, no. 370, pp. 138-150, 1985