Hydrodynamic and Supportive Structure for Gated Ship Sterns: Amphibious Ship Stern Flap

Abstract

Stern flaps have now been at sea for more than two decades, on a variety of U.S. Navy (USN) and U.S. Coast Guard (USCG) classes, including destroyers, cruisers, frigates, cutters, and patrol craft. Application of flaps to large-deck amphibious-type ships is a fairly recent extension of the technology. Ship performance improvements such as delivered power reduction and fuel savings, and maximum speed increases, have been proven during at-sea trials and are well documented. U.S. Navy amphibious ships contain well decks, which are accessed through large folding stern gates. When open, the gates are supported by sizable structures, which are partially submerged and affixed to the transom. A new concept, the hydrodynamic and supportive structure for gated ship sterns, i.e. the amphibious stern flap, was developed and patented by the author. This design combines a stern flap’s hydrodynamic performance surface with the stern gate support structure. The Naval Surface Warfare Center, Carderock Division (NSWCCD), has now designed and implemented this new type of integrated stern flap and gate support structure on several U.S. Navy amphibious ship classes. U.S. Navy ship design and R&D programs have resulted in amphibious stern flaps being implemented as new construction items on two new Navy amphibious ship classes and one new subclass. Fleet Readiness R&D programs have funded amphibious stern flap design, retrofit installation, and evaluation trials on two existing amphibious ships. Each amphibious stern flap design spiral, model-test series, optimization, full-scale implementation, as well as performance benefits and fuel savings will be discussed.