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History of the Hovercraft - in brief!
Over the centuries there have been many efforts made to reduce
the element of friction between moving parts. Shipbuilders have
always known that 'drag'
results from the skin friction of water acting on hulls. Early
attempts at forcing air through tiny jets either under the hull
or all around it failed simply because the engine needed to
produce so much air, plus the propulsion engines put the cost
way above any advantage in speed. Many other ideas where tried
during the early 20th
century until they came together in the genius of one man - Sir
Christopher Cockerell.
An electronics engineer by profession, his hobby was small-boat
sailing of craft he had designed and built himself. He too
thought long and hard about drag on his hulls and he
experimented like many others before him with a variety of
devices for introducing a film of air to reduce 'drag'. He
evolved the word 'lubrication' for this film of air between hull
and water. He experimented with the now world famous coffee tins
and
hair drier. By firstly blowing air through one can onto a
kitchen scale Cockerell read the 'downward pressure'. He then
added a slightly smaller can inside the original can, and by
causing the same amount of air to escape along the outer edge
(periphery) of the can he tripled the 'downward pressure'
reading. He had produced a 'skirt' of air capable of supporting
a weight. He made a working model with a boat-building friend,
and tried it out on Oulton Broad near where he lived - and it
worked. This was in 1956.
A 'being' treated with a great deal of scepticism, the
Government of the day slapped a secrecy order on Cockerell's
idea, eventually contracting Saunders-Roe to build a full sized
hovercraft to test its feasibility. Cockerell also involved the
NRDC (National Research Development Council), which fixed
patents and rights to protect the invention from being copied
abroad. They also provided the necessary funds.
So the first hovercraft - SRN-1 was flown from Calais to Dover
in 2 hours on July 25th
1959. This first craft, 30 feet in length with a 24 foot
beam weighed 3.5 tons. It was powered by a 435hp Alvis
Leonides air cooled radial engine driving an axial fan. Air was
drawn in through a huge inverted bell-shaped intake 8 feet in
diameter fixed in the centre of the oval shaped hull. The air
scooped in by the fan set inside the funnel was delivered under
pressure through a series of ducts to the 'annular jets' set
around the periphery of the craft's underside. This gave the
craft a 9 inch lift. The prototype had no 'skirt' - the jets,
turned very slightly inward around the edge, became a containing
wall to hold the cushion of air beneath the craft. A skirt was
fitted later, which meant less power was needed to 'lift' the
craft, as less air leaked away. More experiments took, place
culminating in the two most famous hovercraft. SRN-4 - the cross
channel ferry (1968) carrying 254 passengers and 30 cars - later
stretched to carry 396 passengers and 53 cars, powered by four
Marine Proteus Gas Turbine engines of 3,800 shp each. Sadly the
last two were taken out of service on the 2nd
October 2000. The smaller SRN-6 was a craft used both as a ferry
and also for military purposes throughout the world from hot
deserts to Arctic wastes.
At the same time the hovercraft principle attracted many
'pioneer' amateur builders who began to build and use single
seater craft, soon to be used for racing. In 1966 the Hovercraft
Club of Great Britain was formed which controls hovercraft
racing and leisure use of small hovercraft up to 1000kgs in
weight, and is a founder member of the European Hovercraft
Federation and World Hovercraft Federation.
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