Stern Flap Powering Performance on a <i>Spruance</i> Class Destroyer: Ship Trials and Model Experiments

Abstract

ABSTRACT Model and full scale testing by the U. S. Navy indicate substantial powering improvements due to the installation of a stern flap on Spruance Class (DD 963) Strike Destroyers, and Ticonderoga Class (CG 47) AEGIS Cruisers. An appropriate stern flap design was determined through model scale experimentation, and full scale powering improvements were predicted. The destroyer Arthur W. Radford (DD 968) was then fitted with a prototype stem flap in order to demonstrate full scale performance improvements. Speed/power ship trials indicate considerable performance improvements due to the stern flap: reduction in power of 6% to 14%, resulting in an 11.7% time‐averaged powering reduction 0.75 knot increase in top speed $240K annual fuel cost avoidance (savings) retrofit cost amortized in less than one year The flap design on the A. W. Radford , and the associated fuel savings, can be applied to each ship of the DD 963 and CG 47 Classes, for a multi‐million dollar life cycle fuel cost savings. An economic cost analysis was performed on the stern flap installation for both the Spruance and Ticonderoga Classes. The stern flap fuel cost avoidance and retrofit costs place the Net Present Value at $60 million. The internal rate of return on investment may reach as high as 262%. The physics surrounding the operation of a stern flap on this combatant, and some identified mechanisms that account for the improved performance, are also discussed.