Hydrofoils and hovercraft
are specialized water vehicles. A hydrofoil has small wing-like surfaces,
called foils, that are attached to the bottom of its hull. As the hydrofoil
accelerates, the foils act much like small aircraft wings, lifting most of the
hull out of the water. Because less of the hull is in the water, less effort is
used to push the hull against the resistance of the water. Hydrofoil speed
varies, but most passenger-carrying hydrofoils can travel about 100 km/hr
(about 60 mph). Some experimental models can travel even faster.
The hovercraft is a type
of vehicle that is lifted entirely off the water surface by a cushion of air.
Hovercraft can be propelled by giant air propellers or by water jets. Such
vessels are not limited to moving over water but can also move over land.
Because the vessel does not contact the surface, relatively high speeds can be
obtained. Hovercraft have been used for search and rescue, for moving freight,
and for passenger transportation.
Michael D. Meyer
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