Seakeeping and Vibration Tests of the Coast Guard 110 Foot Surface Effect Ship SEA BIRD Class (WSES)

摘要

Seakeeping and vertical acceleration tests were performed on the U.S. Coast Guard 110 ft Surface Effect Ships USCGC SHEARWATER and USCGC SEA HAWK. Roll, pitch and heave motions were recorded and later analyzed. All motions were averaged by highest one tenth and highest one third single amplitudes. Vertical accelerations were further analyzed using ISO standards to determine the human response and fatigue limits relative to high frequency (1.8 HZ) heave motions encountered. Tests were conducted in 2.5 to 4 foot seas at speeds of 16 to 28 knots. The objective of this technical evaluation was to quantify the ride quality of the Coast Guard 110 ft SES. This 110-foot surface effect ship is a high-performance air-cushion-assisted craft, designed for on-cushion speeds of 30 knots in calm water and 25 knots in sea state 3. The ship rides on a drag-reducing cushion of air contained by catamaran-type sidehulls and flexible bow and stern seals. When cruising on cushion, the center portion of the hull is clear of the water and supported by the air cushion, thereby reducing the wetted surface area and decreasing the resistance and enabling higher speed. The ship is also capable of off-cushion operations at low speeds in all sea states. The SHEARWATER was able to maintain 28 knots in 2-foot seas in December 1982; however, recent operations such as the SEA HAWK tests in November 1983 and August 1984 show lower maximum speeds than designed (18-23 knots) are attained.