Wam and W ayfaring
19 5
surface—piercing hydrofoils to fairly sheltered waters such as the
Mediterranean and the Adriatic in the summer.
The most sophisticated and seaworthy type of hydrofoil has fully—
submerged foils. These craft keep their foils constantly under water,
operating exactly like the wings of an aircraft. This similarity is
borne out in their control, because to maintain an even depth the
angle of the foils beneath the surface has to be continually changing
according to the surface of the sea ahead. The craft cuts through
small waves with little or no reaction, but it must detect and follow
the contours of larger waves which would otherwise smash against
the hull. The British hydrofoil expert, Christopher Hook, has
devised a how—sensing foil which moves over the water in front of
the boat and adjusts the submerged foils accordingly via a
‘dampened’ mechanical linkage. A more sophisticated system,
developed in the United States, controls the ‘ight’ of the hydrofoil
craft electronically. A sonic beam detects on—coming waves, while
gyroscopes sense roll and pitch. The whole system is integrated by a
‘black box’ which controls the angles of the submerged foils.
While the Soviet Union and the United States concentrated on
foil—borne craft, the United Kingdom was busy developing a
completely new kind of transport, the hovercraft. Sitting on a
cushion of air, the hovercraft escapes almost completely from the
viscous drag of the water and, because it rides over, rather than
through, the water, experiences very little wave—making resistance.
Christopher Cockerell, the man who invented this marvellous
machine, demonstrated his air—cushion idea to scientists, engineers
and government ofcials in 1956. Within three years the rst
hovercraft, the SRN—I, was on the slipway of the Saunders—Roe
Company at Cowes. The S RN—I, like Cockerell’s earlier saucer—
shaped model, was kept hoveriñg above the surface (water or land)
by air pumped down and inwards from
the outer rim. This peri—
pheral jet raised the 4—ton craft about IO inches off the ground by
means
of the ground effect: the annular jet traps a volume of
pressurized air which pushes up on the flat underside of the vehicle
in an effort to escape.
The ‘curtain’ of air around the edge also helped to keep the cushion
intact and replaced any air which managed to escape, but the limitations of this invisible restraint soon became apparent. Somehow
the clearance of the vehicle had to be radically increased for the
hovercraft to be anything more than an interesting idea. The
19 5
surface—piercing hydrofoils to fairly sheltered waters such as the
Mediterranean and the Adriatic in the summer.
The most sophisticated and seaworthy type of hydrofoil has fully—
submerged foils. These craft keep their foils constantly under water,
operating exactly like the wings of an aircraft. This similarity is
borne out in their control, because to maintain an even depth the
angle of the foils beneath the surface has to be continually changing
according to the surface of the sea ahead. The craft cuts through
small waves with little or no reaction, but it must detect and follow
the contours of larger waves which would otherwise smash against
the hull. The British hydrofoil expert, Christopher Hook, has
devised a how—sensing foil which moves over the water in front of
the boat and adjusts the submerged foils accordingly via a
‘dampened’ mechanical linkage. A more sophisticated system,
developed in the United States, controls the ‘ight’ of the hydrofoil
craft electronically. A sonic beam detects on—coming waves, while
gyroscopes sense roll and pitch. The whole system is integrated by a
‘black box’ which controls the angles of the submerged foils.
While the Soviet Union and the United States concentrated on
foil—borne craft, the United Kingdom was busy developing a
completely new kind of transport, the hovercraft. Sitting on a
cushion of air, the hovercraft escapes almost completely from the
viscous drag of the water and, because it rides over, rather than
through, the water, experiences very little wave—making resistance.
Christopher Cockerell, the man who invented this marvellous
machine, demonstrated his air—cushion idea to scientists, engineers
and government ofcials in 1956. Within three years the rst
hovercraft, the SRN—I, was on the slipway of the Saunders—Roe
Company at Cowes. The S RN—I, like Cockerell’s earlier saucer—
shaped model, was kept hoveriñg above the surface (water or land)
by air pumped down and inwards from
the outer rim. This peri—
pheral jet raised the 4—ton craft about IO inches off the ground by
means
of the ground effect: the annular jet traps a volume of
pressurized air which pushes up on the flat underside of the vehicle
in an effort to escape.
The ‘curtain’ of air around the edge also helped to keep the cushion
intact and replaced any air which managed to escape, but the limitations of this invisible restraint soon became apparent. Somehow
the clearance of the vehicle had to be radically increased for the
hovercraft to be anything more than an interesting idea. The