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The Test-Rig
A diagram which shows the basic principle behind Christopher Cockerell's
original experiment. |
| See larger diagram |
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The theory behind one of the most successful inventions of the 20th
century, the Hovercraft, was originally tested in 1955 using an empty
KiteKat cat food tin inside a coffee tin, an industrial air blower
and a pair of kitchen scales.
Christopher Cockerell was initially testing out the idea that it
was possible to produce a cushion of air between the bottom of the
tins and the surface of the scales. Once he had established that
this was possible he decided to experiment with more sophisticated
models.
Although his first tests were carried out on dry land his main aim
was to prove that drag or friction between boats and water could
be substantially reduced if the ‘craft’ floated on an
air cushion. And so the ‘hovercraft’
came in to being. Indeed Cockerell came up with the word too, which
was recently chosen to represent 1959 in the 100 words, which encapsulate
the 20th century for the millennium edition of the Collins English
Dictionary.
Christopher Sydney Cockerell was born in 1910 at Cherry Hinton near
Cambridge, the son of Sir Sydney Carlyle Cockerell, sometime private
secretary to Sir William Morris and from 1908 to 1937 Director of
the Fitzwilliam Museum, Cambridge. The Cockerells were a talented
family. The sons of Sydney John Cockerell, a London coal merchant,
and Alice nee Bennett, the daughter of a City Watchmaker, Sir Sydney’s
elder brother, Theodore, was a biologist, his younger brother, Douglas,
and eminent bookbinder; while Douglas’s son Sydney Maurice
(‘Sandy’), two years Christopher’s senior and also
a bookbinder, was a celebrated and innovative designer of marbled
papers.
Despite an interest in the arts, Christopher read Engineering at
Peterhouse, Cambridge. After Cambridge he worked for the Radio Research
Company until 1935 and then for the Marconi Wireless Telegraph Company
from 1935 until 1951. He had an enormous capacity for invention and
his father, despite reservations (he once described his son as ‘no
better than a garage hand’), put up the money for his early
patents. (When Sir Sydney died in 1962, aged 94, some obituaries
of this great museum director and manuscript collector, friend of
Bernard Shaw and T.E. Lawrence, literary executor of Thomas hardy,
called him simply ‘grandfather of the hovercraft’).
During the war years Cockerell worked with an elite team at Marconi
to develop radar, a development which Churchill believed had a significant
effect on the outcome of the Second World War, and Cockerell believed
to be one of his greatest achievements. Whilst at Marconi Cockerell
patented 36 of his ideas. Cockerell left Marconi in 1950, and with
a legacy left by his beloved wife Margaret’s father, he and
Margaret were able to purchase a small boatyard in Norfolk. This
never seemed to make money and Cockerell’s mind turned back
to earlier ideas.
He decided to use larger models on water. Initial experiments convinced
Cockerell that boats could be made to float on a cushion of air,
thus reducing the effect of the water drag. After many trials he
successfully designed a craft which proved his ideas were correct.
He was not surprised. The modified punt he used had a special pump
to blow high-pressure air down under and around the rim of the craft.
A strong rubber curtain retained most of the air, hence creating
lift. Cockerell had set up a company, Ripplecraft, to develop his
ideas further and in 1955 he eventually convinced the Ministry of
Supply to back his project. He had a hard time trying to convince
the military: the Admiralty said it was a plane not a boat; the RAF
said it was a boat not a plane; and the Army were ‘plain not
interested’.
The irony is that it has been the Marines who have taken the hovercraft
most seriously, with over 100 giant craft now in use in America and
250 in the Soviet Union, many used in recent conflicts. In these
early days Cockerell’s idea was patented and immediately put
on the secret list. Nothing happened and Cockerell became increasingly
agitated. Eventually, in 1958, after declassification, the National
Research Development Council (NRDC) funded the design and construction
of SR.N1 – the world’s first man-carrying amphibious
hovercraft.
Saunders Roe, the flying boat firm at Cowes on the Isle of Wight,
were given the contract, and the firm, under Cockerell’s guidance,
worked avidly on the 20ft craft dubbed the ‘flying saucer’.
Ahead of schedule on 31st May 1959, the seven-ton craft flew, only
eight months after the commencement of design work. But it was not
until 11th June that she made her first public appearance in front
of the world’s press.
Such was the interest in this new form of transport that the press
refused to leave until she was demonstrated in the water. Within
weeks, on 25th July she made a crossing of the English Channel, from
Calais to Dover, with Cockerell aboard as human ballast, on the 50th
anniversary of the first aeroplane crossing of the Channel. Cockerell’s
dream had become a reality. Since then hovercraft have carried over
80 million people and 12 million cars across the Channel and have
been in continuous service for over 30 years.
Besides hovercraft he is attributed with the invention of wave power
in the late 1970s, hovertrains and sidewall hovercraft (catamarans).
Although Cockerell disagreed with the way the NRDC proceeded with
hovercraft production, and in 1966 resigned from the board of Hovercraft
Development, today hovercraft are enjoying a renaissance.
Cheaper, quieter diesel engines, new construction materials and
advanced skirt design mean that a hovercraft today is the same price
as one 30 years ago. With developing countries having the greatest
need for hovercraft, with shallows, coral reefs, mud flats, no ports
and unprepared beaches, hovercraft are coming in to their own.
On the last weekend in May 1999 the hovercraft industry launched
Hovershow
’99 – the biggest show since 1966. Visitors were impressed
by how the hovercraft has become a viable and versatile workboat
and export sales in the last year have reached £20m. Recent
sales have been to Canada for coastguards, to Lithuania as crew boats,
to Hong Kong for fishery patrols, to Nigeria for oil crew boats,
to Finland for coastguards to be used on ice and to Sri Lanka for
military purposes. As Cockerell said, ‘Hovercraft will always
be around – you can’t un-invent something!’
During the course of the weekend the 40th anniversary of the first
flight of the hovercraft was celebrated, and Cockerell sent his best
wishes but was too frail to attend. On the Monday a flypast was staged
in his honour. He died the following day, with as many patents to
his name as he had years.
Warwick Jacobs
The Hovercraft Society |
