Hovercraft are amphibious vehicles which are supported by a cushion of air. Since they are lifted slightly off the terrain they're travelling on, they are able to travel over both land and water and, because of the lack of friction, they are able to travel at quite high speeds.

Hovercraft should not be confused with sidewalls, which are a cross between a catamaran and a hovercraft, where pressurised air is kept between the twin hulls, elevating the vessel and reducing the drag through the water, but preventing it from travelling on land.

Early Hovercraft

The first recorded design for a hovercraft-like air cushion vehicle was put forward by Swedish designer and philosopher Emmanual Swedenborg in 1716. Swedenborg soon realised that his idea, which was to be man-powered, would not work, and so abandoned it.

In the mid 1870s, Sir John Thornycroft became interested in the idea of hovercraft. He built a number of model craft, yet because the internal combustion engine had not yet been invented, his idea did not have a suitable power source.

Sir Christopher Cockerell

In the mid 1950s Christopher Cockerell¹, a brilliant British radio engineer who also ran a boatyard on the Norfolk Broads, began exploring the use of air lubrication to reduce hydrodynamic drag. His early experiments included a punt and a 20-knot ex-Naval launch, but he soon realised that using air-lubrication as an efficient means of transport would only work with a purpose-designed vehicle. What he needed was an air cushion to lift the craft above the water, enabling it to sail not only over the waves, but also over land.

To check his theory, Cockerell used little more than a couple of tins, an air-blower and some scales. By inserting a cat food tin into a coffee tin, and blowing a jet of air through the gap between the walls of the inner and outer tins, he demonstrated the possibility of a machine that could one day travel on a cushion of air.

Christopher Cockerell had a neighbouring boat builder produce a working model hovercraft. His idea worked very well in model form, and so he decided to pursue it. At the time, it was the duty of anyone who thought of an invention that might have military potential to report it to government and so he contacted the Service Ministries. The model hovercraft flew over many Whitehall carpets in front of various government experts and was subsequently put on the secret list. Saunders-Roe, an Isle of Wight aircraft company based at East Cowes, was contacted by the National Research & Development Corporation to build a full-scale craft.

Saunders-Roe and the SR.N1

In 1959, Saunders-Roe - whose company had recently been bought by Westland Aircraft - began work on the new vehicle with great enthusiasm. The world's first hovercraft was completed two months ahead of schedule, only eight months after it was started. The Cockerell-designed research vessel Saunders Roe Nautical One (SR.N1) appeared in May at East Cowes, Isle of Wight. The first flight took place on 11 June.

The press watched with astonishment as the model craft was demonstrated to them on a lawn and over a small obstacle course. After that, the full-sized machine was carried out on to the concrete slipway and was launched into the East Cowes yacht basin. This was a nervous time for the engineers because the hovercraft had never before been tried over water, but all went well and no problems were encountered. This, the first skirtless craft, could operate only in calm seas with waves of up to one and a half feet in height, and was able to negotiate obstacles of 6 to 9 inches.

On 25 July, 1959, the SR.N1 crossed the channel between Calais and Dover in two hours and three minutes. It had been shipped to France especially for the occasion, 50 years to the day since Louis Bleriot made the first crossing of the Dover Strait by aeroplane.

In December, 1959, the Duke of Edinburgh visited Saunders-Roe at East Cowes and persuaded the chief test-pilot, Commander Peter Lamb, to allow him to take over the SR.N1's controls. He flew her so fast that he was asked to slow down a little. On examination of the craft afterwards, it was found that she had been dished in the bow due to excessive speed, damage which was never allowed to be repaired, and which was affectionately referred to as the 'Royal Dent'.

Latimer-Needham

After reading about Cockerell's experiments, another inventor, CH Latimer-Needham, thought about the size of the waves that hovercraft would likely encounter in the English Channel and the Atlantic. Although the SR.N1 was a success, it was plagued by slow performance and the inability to traverse even very small waves easily, due to its low hover height of only 23cm. Latimer-Needham was convinced that the way forward was to create a flexible skirt to contain the air cushion. This would let hovercraft travel during rougher weather and, in October 1961, Latimer-Needham sold his skirt patents to Westland.

The introduction of the skirt was a vital engineering breakthrough. It meant that the total depth of the air cushion beneath the solid structure was now equal to the depth of the skirt and engineers soon discovered that the obstacle clearance height was ten times greater. Apart from being subjected to wear and tear, particularly at high speed over water, skirts had few operational problems. The skirt was found to deform around waves, rocks and jetties, afterwards promptly returning to its normal inflated shape, keeping air leakage at a minimum.

The SR.N1, which in its original piston-engined configuration could already make a respectable 35 knots, was now fitted with a Rolls Royce Viper jet engine which gave it an easy 50 knots. With a four foot skirt fitted around its perimeter, the craft could cope with six to seven foot waves, cross marshland with gullies up to four foot deep and traverse obstacles up to three foot six inches high. Moreover, the craft was now operating at twice its original weight, with no extra lift-power needed. The SR.N1 can now be seen in the Science Museum in London.

Other Saunders-Roe Hovercraft

Other companies started building hovercraft, especially Vickers and Vosper Thornycroft, but Saunders-Roe continued to lead the way.

In late 1959 it began to design the first passenger-carrying hovercraft and, by 1962, the SR.N2 had entered commercial service with a payload of 59 passengers. However, the field was moving fast and subsequent advancements in hovercraft technology quickly overtook it, so that only the one was ever built.

The SR.N3

By the end of 1963, the Ministry of Technology asked for a larger version of the SR.N2 for military purposes. This was the SR.N3 and it was capable of carrying 92 fully-equipped soldiers at speeds over 70 knots. It was launched in December 1963 and was also designed to carry vehicles such as jeeps or medium-sized trucks. Again, only one was built. The IHTU, Interservice Hovercraft Trials Unit, tested the SR.N3 at their facility at HMS Daedalus near Gosport to ascertain whether hovercraft could have any military potential.

By 1974, after using the SR.N3 in a number of roles, the Ministry of Defence decided to use it as a testbed to see how vulnerable hovercraft were to under-water explosions. The SR.N3 was tethered and subjected to a series of explosions, some actually under the craft, and yet not only did it survive, but it was still capable of returning to base under its own power.

The SR.N5 and SR.N6

Meanwhile, Saunders-Roe had started work on the SR.N5. This was the first hovercraft to be designed from the start to be fitted with a deep, flexible skirt. The SR.N5, known as the 'Warden' class, was almost 40ft long and 23ft wide, could carry 18 passengers and had a top speed of 66 knots. The first craft hovered in April 1964 and 14 were built.

As soon as the SR.N5 appeared in service, there was a demand for hovercraft with greater carrying capacity. So, in 1964, the SR.N6 'Winchester' class was designed, essentially a SR.N5 but 10ft longer. The first SR.N6 was launched in March 1965 and could carry 38 passengers. British Rail Hovercraft Ltd, though, were not content with this and requested an even bigger craft, so in 1972 the SR.N6 was duly stretched by a further 10ft. The passenger capacity was now 58 and, perhaps surprisingly, performance was not affected by the stretch.

The last in the SRN.5/6 series was designed to be quieter, as all of Saunders-Roe's hovercraft were quite noisy². By this time, in 1982, 69 SRN5/6 craft had been built, including five for the Iraqi Navy and eight for the Imperial Iranian Navy.

The SR.N4

Westland had intended to follow the SR.N3 with a large craft, the SR.N4, but this was delayed until the skirts for the SR.N1 and SR.N5 had been fully developed and tested. In 1965, the project was authorised and work was started. Despite the Saunders-Roe company merging with Vickers Supermarine in December, 1966, forming the British Hovercraft Corporation Ltd and causing Sir Christopher Cockerell's resignation, work continued and the first trials began in 1967. The SR.N4, known as the 'Mountbatten' class, was the world's largest hovercraft, capable of carrying 254 passengers and 30 cars across the channel in half an hour. It displaced 200 tons, had a top speed of 83 knots³ and ran on aviation fuel. The SR.N4's propellers, at 21 feet in diameter, were (and still are) the largest driven propellers in the world.

The SR.N4's 2.5m skirt was expected to cope with most conditions in the Channel. It underwent two hours 30 minutes of trials, covering a distance of 20 miles and reaching speeds approaching 50 knots, in winds gusting to force 6. The world's first hovercraft car ferry made its maiden flight from Dover to Boulogne on 11 June, crossing in 35 minutes.

This not only captured the public imagination, but the British government also instructed British Rail to set up a hovercraft subsidiary and introduce an Isle of Wight route prior to taking delivery of the first SR.N4 for cross-Channel services in 1968.

It was soon realised that the skirt system still had not been perfected and, by 1976, the skirts were replaced. The new skirt, when inflated, raised the craft three metres into the air. The SRN.4s were also stretched by 55ft, increasing passenger accommodation to 418 and the car capacity to 60. Now displacing 300 tons, the SR.N4 was nicknamed 'Super 4'. It is the world's largest hovercraft, for which the Cowes, Isle of Wight, workcrew were awarded the 1978 Award for Innovation.

After the SRN.4

The Saunders-Roe team continued to make hovercraft. The next model, the BH-7⁴ was started in 1969 and was called the 'Wellington' class. Six were sold to the Imperial Iranian Navy.

In 1972, the British Hovercraft Corporation bought another Isle of Wight company, Cushioncraft, which had specialised in sidewalls. This company had been created by John Britten and Desmond Norman, who designed the very successful Islander aircraft.

The latest class of hovercraft to be built were the AP1-88 in 1982. By the year 2000 over 14 had been built including tank-landing hovercraft for the American Army, some for the Canadian Coastguard and several domestic passenger models, especially for the Isle of Wight route.

Domestic British Hovercraft Routes

Three years after the hovercraft's invention, hovercraft passenger routes soon started to open up throughout Great Britain, but few lasted long. The main exception has been getting to the Isle of Wight, home to Saunders-Roe and other manufacturers, where machines have flourished.

In August 1962, a passenger service was started from Eastney beach, Southsea (near Portsmouth) to Ryde, Isle of Wight, on weekday mornings using the newly-built 48 seat SR.N2 craft. A new company, Hovertransport, was also formed to carry passengers on the experimental Ryde to Eastney route. In 1965, Hovertravel Ltd. started their Southsea to Ryde service with Winchester Class, 38 seater SR.N6. This is now the world's oldest hovercraft operator. In addition, a Ryde to Stokes Bay, Gosport, service was also begun, but it closed two years later. Before it closed, though, it had carried over 500,000 passengers.

During March, 1965, British Rail Hovercraft Ltd formed Seaspeed and the Southampton to Cowes service started in July with two 36 seat SR.N6 craft. In March, 1967, Seaspeed's Cowes - Portsmouth Harbour link opened using an SR.N6. The service continued before it closed in September, 1969. April, 1968, saw the inauguration of a third Seaspeed Isle of Wight service, from Portsmouth to Ryde.

Considering the number of hovercraft routes to the Isle of Wight, it is not surprising that a local singer, Lauri Say, wrote and sang a popular song about them on his Songs For Singing Islanders album released in 1968:

What's this rumbling that I hear?
What's this roaring in my ear?
What's this racket driving everybody daft?
Well it's not artillery
Or the start of World War Three
It's the Westland SRN 'Super-Noiseless' hovercraft.

Oh the hovercraft is coming,
Can't you hear that crazy humming?
You can see the fishes scatter fore and aft.
With it's mighty engine pushing
Floating on it's own air cushion
It's the Westland SRN 'Super-Noiseless' hovercraft.

It's like a mobile goldfish bowl and
When it screams across the Solent,
The duration of your journey will be halved.
If you don't mind being cramped on
For your visit to Southampton
Take the Westland SRN 'Super-Noiseless' hovercraft.

The directors made a statement
In the cause of noise abatement
When we said it made a row they only laughed.
'Anyone can stand the din
If he's got his earplugs in
On the Westland SRN 'Super-Noiseless' hovercraft.'

If this method of propulsion
Fills you with revulsion
You should travel on a dinghy or a raft.
Whatever you may take
You'll never hear the end
Of the Westland SRN 'Super-Noiseless' hovercraft.

The folks who live in Cowes and
Gurnard tremble by the thousand,
And the peace of Ryde is shattered everyday.
So if you want a place that's silent,
You'd better leave the Island,
You can hear the bloody thing at Totland Bay.

Oh the hovercraft is coming,
Can't you hear that crazy humming?
You can see the fishes scatter fore and aft.
With it's mighty engine pushing
Floating on it's own air cushion
It's the Westland SRN 'Super-Noiseless' hovercraft.

Before long, though, only the Hovertravel service had survived. By 1976, Seaspeed, which had operated three services to the Isle of Wight, had transferred ownership of the Southampton - Cowes route to Hovertravel and closed soon after.

After 1 October, 2000, the Southsea - Isle of Wight hovercraft route was the only remaining one in Europe.

International Hovercraft Routes

The prototype SR.N4, the Princess Margaret, entered commercial service for Seaspeed on the 26 mile route between Dover and Boulogne on 1 August, 1968. This route was chosen so that customers could easily be switched to British Rail's ship ferry service if anything went wrong. Six daily return flights were advertised, the first leaving Dover at 8.20am and then every two hours. Wednesday was half-day - with three round trips followed by a period of maintenance.

During November, 1967, Hoverlloyd Ltd⁵ was formed with the object of pioneering the world's first international hovercraft service, between Ramsgate and Calais, although in reality it became the second. On 10 December, 1968, Hoverlloyd's first SR.N4, the Swift, was completed at East Cowes. It was the first craft with the new Mk II skirt which provided a smoother ride, more protection to the bow and 30 minutes transit time. Their second craft, Sure, was launched in 1969.

Hoverspeed was created on 25 October, 1981, when Seaspeed and Hoverlloyd merged. Initially the new company operated a fleet of six hovercraft - two SRN4 MkIII hovercraft, The Princess Margaret and The Princess Anne and four SRN4 MkII hovercraft, Swift, Sure, Sir Christopher and The Prince of Wales, on services from Dover to both Calais and Boulogne.

Sadly, however, they have been gradually replaced by Sea Cats. By 2000, only The Princess Margaret and The Princess Anne were still in operation, yet both have a claim to fame. The Princess Anne holds the record for the fastest crossing of the English Channel, travelling the 23 miles between Calais and Dover on 14 September, 1995, in just 22 minutes. The Princess Margaret featured in the James Bond film Diamonds are Forever. However, both hovercraft were withdrawn from service on 1 October, 2000, leaving the Southsea - Ryde, Isle of Wight route the only remaining hovercraft route in Europe, not far from where the hovercraft was invented.