HIGHLY SKEWED PROPELLER DESIGN FOR A NAVAL AUXILIARY OILER (AO 177)

Abstract : The design of a skewed propeller for the AO-177 Class Fleet Oiler is presented and the design procedure used is described in detail. The design objective of the skewed propeller was to minimize propeller vibration without adversely affecting efficiency. Calculations predict that, at full power design conditions, the final 7-bladed, 21-foot (6.4 meters) diameter design will reduce unsteady thrust to about 0.28 percent of steady thrust and unsteady torque to about 0.35 percent of steady torque. Endurance speed is predicted to be met at 11 percent less than design endurance power. Speed at full power is predicted to be 21.25 knots (10.9 m/s) at 100 propeller rpm (10.5 rad/s). The criteria of 10 percent margin on back bubble cavitation at full power, full load displacement is calculated to be met. In addition no back bubble cavitation is predicted at ballast conditions. At full-power design-conditions, stresses throughout the blades are calculated to be well below the allowable limit of 12,500 psi (86.2 MPa).