THE HISTORY OF HYDROFOILS
Sealegs
Hydrofoil development dates back further than most people would think. The History can be traced back to a British patent recorded in 1869. Since then the quest for speed has established a long string of impressive records and provided remarkable advances in hydrofoil technology. In 1898 Enrico Forlanini, an Italian inventor, invented a fairly operable hydrofoil boat. In 1907 America's Wright brothers experiments in this field along with their more famous venture. In 1918 Alexander Graham Bell and "Casey" Baldwin constructed an 11,000 pound craft which attained the remarkable speed of 70.8 MPH, a record which stood unbroken for almost forty years. In the 1930's various European inventors developed workable hydrofoils. The German Navy was the first to attempt to use them in combat. Since World War II a number of commercial boats in the 20 to 90 ton class have begun regular ferry services in various parts of the world.
The U.S. Navy's interest in the potential of hydrofoils dates back to the 1940's. Between 1947 and 1960 the Office of Naval Research and the Bureau of Ships sponsored a number of research and development projects to establish the feasibility of developing fundamental design criteria for hydrofoil craft. In 1954 a U.S. design XCH-4, achieved a speed of 78 MPH in Great South Bay, N.Y., only to surrender the record seven years later when FRESH-1, a Boeing design, reached an impressive speed of 93 MPH on Puget Sound. Of all the hydrofoil craft, however SEALEGS is perhaps the most notable. SEALEGS, through the joint efforts of GIBBS and COX and the Massachusetts Institute of Technology Flight Control Laboratory,
High Point
provided the first real demonstration of the feasibility and advantages of a fully submerged, automatically controlled foil system versus surface piercing foils, which had been used in earlier United States efforts.
Surface-piercing foils, develop lift in proportion to their speed and submerged area. They couple the hydrofoil craft to the surface
Flagstaff
of the water and therefore subject it to wave action. As the surface-piercing foil enters a wave, the depth of water over the foil increases and more foil surface in wetted, thereby increasing the lifting force. The opposite occurs when passing clear of a wave. Thus, these hydrofoils are subject to vertical motion in a seaway. They are best used on lakes, rivers and protected coastal waterways, where clam weather conditions are predominant. Fully submerged hydrofoils, on the other hand, are designed to fly in a liquid medium. They do not interface with the surface of the water and offer the obvious advantages of a smooth ride and a rough water capability. Foil depth is manually set and relates to foil size, strut length and sea height. An automatic control system, which responds to craft motion, helm orders, and a signal from radar or sonic height sensor is used to assure straight and level flight and fully coordinated banked turns. All the United States Navy's hydrofoils have employed a fully submerged foil system, and the advanced hydrofoil development program has experience in this this technology unequalled elsewhere in the world.
The Navy's first hydrofoil was HIGH POINT (PCH 1) built in 1962. Later that year fund were allocated for PLAINVIEW (AGEH-1), a 320 ton experimental hydrofoil ship. In 1966 contracts were let for the construction of two Patrol Gunboat Hydrofoils, FLAGSTAFF (PGH 1) and TUCUMCARI (PGH 2), each of which saw action in Vietnam. In November of 1972, Germany, Italy and the United States signed a Memorandum of Understanding in which the three nations agreed to share development costs of a missile equipped patrol hydrofoil. The United States agreed to construct the lead ship of this PHM class. This ship, USS PEGASUS, was launched on 9 November 1974 at the Boeing Marine Systems Company in Renton, Washington. After two years of tests and evaluation, she was commissioned
Pegasus
for regular service in 1977. That same year the Boeing Company was awarded a contract for five more missile-equipped hydrofoil combatants of the PHM class, committing the United States Navy to a squadron of hydrofoils which will begin fleet operations by 1983. USS TAURUS (PHM 3) is the first production hydrofoil of this new class.
