Hovercrafts, or Air-Cushioned Vehicles (ACV), are used throughout the world: as ferries, for people and goods; as survey vehicles in scientific and rescue work; to provide disaster relief; as coastguard vehicles; for military and militaristic survey applications; in sport; and for industrial applications. Like Hoover and Stove the name Hovercraft has become a generic term for ACV’s but it is in fact the product name for those vehicles made by Saunders-Roe (later British Hovercraft Corporation (BHC), then Westland) and designed by Christopher Cockerell in Britain during the 1950s. The first mass produced hovercraft, the Saunders Roe Nautical 5 (SR.N5), has been recognised with an Engineering Heritage Award granted to the Hovercraft Museum who have restored the craft:
The Saunders Roe Nautical 5 hovercraft is a unique example of British design and engineering innovation. It was this cutting edge craft that spread the use of hovercraft around the world for civilian and military use.
According to British Petroleum’s (BP) publication The History of the Hovercraft, the crafts uniqueness lies in it being the only form of transport not inspired by nature (birds inspired flight, floating wood etc boats and so forth) and as such it represents a feat of pure engineering and technological skill and invention.
Cockerell’s experimentations began when he purchased a boatyard in Norfolk and started investigating why boats were made as they are: noting that wave resistance cannot be removed but could be minimised by creating either a sliding or rolling vehicle. He observed that skates and sleighs were exceptional vehicles; friction causes ice to melt which provides water lubrication that allows for a very efficient sliding motion. It was this effect he sought to recreate with air by creating a cushion that would sit in the base of the ‘boat’.
After many trials Cockerell concluded that the cushion could be sealed in place by a curtain of continuous jets of air ejected downward and inward all around the periphery of the craft, as shown in the below diagram. The cushion pressure, on the base area of the craft, would thus produce a greater upward force than the effect of the jet on its own. This led Cockerell to the concept of flexible extensions, cited in his 1958 patent.
Cockerell had previously worked on airborne equipment so he first took his idea to the aviation industry who rejected it, not because it didn’t work but because it wasn’t an aircraft; shipbuilders rejected it because it wasn’t a ship. An added complication was the placing of the invention on a secrets list in Nov 1956, this meant he was unable to demo the invention to companies. An inventor was obliged to inform the Government of any invention likely to have military application, the First Sea Lord (Lord Mountbatten) and officers of the Admiralty did receive a demo and placed the craft on the list. The Ministry of Supply then placed a small evaluation contract with Saunders Roe in order for the idea be tested, verified and expanded. As was the norm, State technical experts were sent to assess the craft and to define operation requirements for it. However, the task was impossible because the craft was so new and revolutionary that the experts didn’t know enough to be able to test it! The Ministry therefore dropped the product, leaving Cockerell free to form Hovercraft Limited in 1957; following de-classification of the craft in 1958 the project could be sponsored by the National Research Development Corporation (NRDC).
The NRDC was an independent public body formed in 1948 by Parliament to act in association with industry to develop promising ideas and inventions: although not part of Government it did require Board of Trade approval for some major ventures and their approval in order to borrow money from the Treasury. The concept of such a Corporation was also new; it sought to plug a reduction in private investment for industrial research which had decreased progressively since the outbreak of World War II.
The Hovercraft has certainly greatly enhanced British prestige. [Sir Eric Mensforth, 1970]
The NRDC sought to secure commercial success for developed projects, when development was complete and the invention ready for market its role was to enable industrial firms to take the next step and manufacture the product. These firms were already involved in the projects development and thus had a stake in the product: firms made goods under NRDC issued licenses (made possible by the inventor assigning the Corporation their patents); in return firms paid the NRDC royalties on sales, therefore paying off the Corporations investment. The Corporation saw the hovercraft as one of many inventions that would restore post-war Britain to prosperity, the theory being that technological progress would secure this through new industries, their exports and increased employment. This philosophy meant the NRDC were uniquely placed to seize upon the revolutionary nature of hovercraft, and exploit its potential.
In the autumn of 1958 the NRDC placed an order with Saunders Roe for the first full-scale hovercraft, under the designation SR.NI. Further developments led to the craft being put into production as its fifth incarnation, SR.N5. This was then more than a new transport device; it was also part of the bid to restore Britain to economic health and to reinvigorate the manufacturing sector following World War II.