High-speed hydrodynamic characteristics of a flat plate and 20 degrees dead-rise surface in unsymmetrical planing conditions

Daniel Savitsky, R. E. Prowse, D. H. Lueders
naca-tn-4187
Jun 1958


The results of an investigation made to obtain the wetted areas, the three components of planing forces, and the three components of moments acting on a 0 degree and a 20 degree dead-rise surface in high-speed, unsymmetrical planing conditions are presented. Hydrodynamic data were obtained for trim angles between 6 degrees and 30 degrees, roll angles between -15 degrees and 15 degrees, yaw angles between 0 degrees and 20 degrees, mean wetted-length-beam ratios up to 7.7, load coefficients up to 49.0, and speed coefficients up to 18.0. The collected test data are presented in summary plots which are readily applicable for use in determining the lift, drag, side force, pitching moment, rolling moment, and yawing moment. An analysis is presented of the variation of these quantities with unsymmetrical planing parameters. It was found that the wave rise at the leading edge of the tested planing surfaces was independent of yaw angle for all test conditions. The wave rise at the leading edge of an unrolled flat plate was equal to that of the symmetrical planing flat plate. For the rolled flat plate, the angle of inclination of the spray root line to the keel was identical to that of a wedge whose dead-rise angle is equal to the roll angle. In the case of the tested 20 degree dead-rise wedge, the spray root angle at the leading edge of the rolled-down side was equal to that of a hypothetical wedge whose dead rise is equal to 20 degree less the roll angle. The angle of the spray root line relative to the keel for the rolled-up side of the 20 degree dead-rise surface was essentially constant and independent of roll angle. There was a pronounced effect of finite chine-edge thickness on the hydrodynamic forces, moments, and spray formation at certain unsymmetrical planing conditions for a flat plate. Depending upon particular combinations of planing parameters large negative or positive pressures were developed along the length of the chine with finite thickness and noticeable changes were observed in the spray formation associated with the affected chine edge. Summary plots are presented which define the inception of the chine-edge effects in terms of unsymmetrical planing conditions.

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