A method for calculation of hydrodynamic lift for submerged and planing rectangular lifting surfaces

Kenneth L. Wadlin, Kenneth W. Christopher
naca-tn-4168
Jan 1958


A method is presented for the calculation of lift coefficients for rectangular lifting surfaces of aspect ratios from 0.125 to 10 operating at finite depths beneath the water surface, including the zero depth or the planing condition. The theoretical expression for the lift coefficient is made up of a linear term derived from lifting-line theory and a nonlinear term from consideration of the effects of crossflow. The crossflow drag is assumed to vary linearly from a maximum at an aspect ratio of 0 to zero at an aspect ratio of 10. Theoretical values are compared with experimental values obtained at various depths of submersion with lifting surfaces having aspect ratios of 0.125, 0.25, 1.00, 4, 6, and 10. The method of calculation is also applicable to hydrofoils having dihedral where the dihedral hydrofoil is replaced by a zero dihedral hydrofoil operating at a depth of submersion equal to the depth of submersion of the center-of-load location on the semispan of the dihedral hydrofoil. Lift coefficients computed by this method are in good agreement with existing experimental data for aspect ratios from 0.125 to 10 and dihedral angles up to 30 degrees.

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