Experimental and Analytical Studies of the Longitudinal Motions of a Tandem Dihedral Hydrofoil Craft in Regular Waves

Experimental investigations were conducted with a tandem surface-piercing hydrofoil configuration free to heave and pitch in regular waves. Towing velocities of 5 and 10 fps were used in head and following seas. Tests at the lower velocity were conducted to check data previously reported by Leehey and Steele; the agreement was satisfactory. The data were compared with nonlinear and linearized theory developed by Ogilvie for both quasi-steady and unsteady conditions. The oscillatory heave, pitch, and phase relationships in general agreed well with solutions based on the linearized equations. Consideration of unsteady effects in most cases improved the correlation between theory and experiment. The primary effect of the nonlinearities was in the existence of steady components of heave and pitch. The theoretical components were verified qualitatively by the experimental results.