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The history of hovercraft and air cushion vehicles


Early thoughts of air cushions

The idea of using an air-cushion as a means or aid to acceleration and reduction in (hydrodynamic) drag was first explored by Sir John Thornycroft, a British engineer, who, in the 1870's built some experimental models on the basis of an air cushion system that would reduce the drag of water on boats and ships.

In 1877 he successfully patented the idea and his theory was that if a ship's hull was given a concave bottom, which could be filled - and replenished - with air, it would create significant additional lift. And so the air cushion effect was born.

Decades later scientists and inventors were still busy with his ideas but without any practical applications. With the coming of the airplane however, it was noticed that additional lift was obtained if the plane flew closer to land or water, creating a "funnel effect", a cushion of air.

The air lift that this funnel effect created differed with the type of wing and its height above ground. The effect was strongest if this height was between one half and one third of the (average) front-to-rear breadth of the wing. Also known as "chord".

The next two decades saw little interest in air cushion development. World War 1 saw a huge increase in the development of the airplane as a military weapon and even though the ground effect was known, airplanes were designed for speed and manoeuverability in the air rather than close to the ground.

 

But because of the many difficulties these models were developed as flying boats rather than air cushion vechicles or ground effect flyers, using the ground effect for take-off from the water. No real hovercraft came along until the 1950's.
 

Boeing's B-1 Flying Boat in 1919 - Links999 ground effect vehicles.
The Boeing B-1 Flying boat in 1919. (c) Airline History.

Flying boats, however, are an integral part of aviation and transport history becoming popular and practical in an era when landing strips and airports were still sparse. They are still used today and many of the older models that proved their worth the world over are lovingly maintained by collectors and enthusiasts.

We highly recommend Airline History for a complete pictorial overview of Flying Boat history.

Early uses of the air cushion effect 1920 - 1949

The German-built Dornier Do-X flying boat proved the reality of Thornycroft's theory in 1929, when, during an Atlantic crossing, it flew much closer to the ocean's surface than was usual in order to take advantage of the air cushion effect. The trip time was significantly reduced as a result and the aircraft's performance that much greater.

The Do-X Flying Boat became quite a legend in its day, especially when it started flying around the world in 1926. Despite its enormous fuel consumption - around 400 gallons of gas per hour - it was one of the first large passenger planes capable of 150 seats. But its engines tended to overheat and, after its arrival in New York in 1931 it was refitted with American water-cooled engines.

During World War 2 the Dornier factories made several Do-X flying boats for a variety of purposes, from transatlantic mail carriers to bombers.

(For more detailed information on Dornier's Do-X see also Dafkurse (D), Aviation Posters, EADS (D), Avions-Legendaires (F) articles.)

Many flying boats were built during this era, and they formed the forefront and backbone of many aviation routes across the world, especially on the long haul destinations.

The Russian Sikorksy proved exceptionally talented at manufacturing flying boats and many airlines ordered their planes from his factories.

The military are always at the forefront in taking advantage of technological developments, and so it was with the air cushion effect.

Another decade later, for example, during World War 2, scouting aircraft made good use of the air cushion effect to extend their reconnaissance flights.

Dornier's Do-X Flying Boat

Dornier's Do-X flying boat - air cushion vehicles Links999.
Dornier's Do-X Flying Boat (c) Avions-Legendaires.

Dornier's Do-X flying boat - Links999 hovercraft history.
The Do-X Flying Boat loading and unloading.
(c) Aviation Posters.

The Do-X flying boat at rest in Rio de Janeiro's harbour - Links999 hovercraft history.
The Do-X at rest in Rio de Janeiro's harbour with
Sugarloaf Mountain as backdrop. (c) EADS.

 

The first real hovercraft - 1950 to 1960

The successful use of the air cushion effect was not lost on engineers after World War 2 was over and in the early 1950's British, American and Swiss engineers started to rethink Sir John Thornycroft's problem.

The Englishman Christopher Cockerell, commonly seen as the father of the hovercraft, being retired from the army, settled into boat building where he soon got captivated by Thornycroft's problem of reducing the hydrodynamic drag on the hull of a boat by using some kind of air cushion.

His theory was that, instead of using the plenum chamber - an empty box with an open bottom as Thornycroft had devised - air was instead pumped into a narrow tunnel circumnavigating the entire bottom, it would flow towards the center and form a more effective air cushion. This peripheral jet would cause the air to build up enough pressure to equal the weight of the craft and, as it would have nowhere to go, the pressure would force the craft up, clearing it off the ground altogether.

Cockerell successfully tested his theory and filed his first patent in 1955. The year after he formed a company called Hovercraft Ltd. He further envisioned and partially worked out other problems of the hovercraft principle that still have to be fully exploited by modern hovercraft builders. One of these was to re-use the air for greater overall efficiency.

Thinking that his air cushion vehicles would be eminently suitable as amphibious craft he approached the British Ministry of Supply, the government's defence equipment procurement authority with his findings. Soon after, in 1956, the air cushion vehicle was classified as "secret" and a construction contract was placed with a British aircraft and seaplane manufacturer. The result was the SR.N1 in 1959.

The first SR.N1 weighed four tons and could carry three men. Its maximum speed was 25 knots (1 knot = 1.15 miles or 1.85 kilometres per hour) on calm water. It had a 6-inch (15 cm) rubberized skirt to make it easier to contain the air cushion on uneven ground.

Significant wear and tear of the skirt through friction with the water at high speeds made it necessary to use more durable material and a rubber and plastic mixture was developed by 1963. The length of the skirt had also been extended to about 4 feet (1.2 m).

By this time the Americans, the French, Japanese and Swedes had begun to be interested in the air cushion vehicle and its possibilities and companies sprang up the world over.

As far as experimental vehicles were concerned the Soviets, in their race for technological supremacy, were as prolific as the Americans in building craft of all sizes, shapes and types. Nothing was too weird or technologically theoretical but it was built. Especially after World War 2, during the 1950's and 1960's did experimental constructions reach extraordinary proportions.

 

Other parts were also improved on, the craft now used a gas turbine engine, and was capable of carrying a payload of about seven tons, achieving a maximum speed of 50 knots.

In June 1959 the SR.N1 crossed the English Channel, exactly 50 years after Louis Blériot's first flight across.

Cockerell's first hovercraft - Links999 hovercraft history.
Christopher Cockerell's SR.N1 hovercraft - 1959.

 

Most of these craft were never put into production, many didn't even work properly, and modern day collectors will pay large amounts to add these craft to their collections.

But not only governments and their military where entranced with the hovercraft and the air cushion vehicle, commercial companies like Ford Motor Company even came up with a hovercar which it called the "Glideair" in 1959. It was never made commercially available for a number of reasons however.

Parallel invention

While Cockerell was busy designing and building his hovercraft in the U.K., across the Atlantic ocean Colonel Melville Beardsley was developing an air cushion vehicle of his own in the 1950's.

The skirt around the ACV platform which contains the compressed air and makes the ACV a stable vehicle is the invention of Colonel Beardsley, for example, for which patent Cockerell later paid $80,000. The modern Hovercraft would not exist without it.

A gifted man of many inventions Colonel Beardsley continued to work on ACV's for the US Naval laboratory across the river from Annapolis, Maryland through the 70's, leading to the modern amphibious military craft of today. He passed away in November, 1998, at the age of 85.

Hovercraft and Ram-wing Craft in the 1960's and beyond

Ram-wing craft

 
Ram-wing craft were craft based on the principle of a wing using the ground effect described above. They were first developed by American aerodynamicists in the early 1960's.

In the global technological race that was going on during the 1960's an amazing array of wing-in-ground effect vehicles were built the world over. The Russians in particular explored this principle in a myriad of craft, like the Ekranoplan (shown at the right) and its infamous Caspian Sea Monster.

Although few of the craft built got beyond the experimental stage, they did show that a combination of airfoil and air-cushion technology provided enough stationary hovering capability. This lift was then transferred into forward speed.

Even though it was now possible to surpass the theoretical hover speed limit of around 320 kilometers per hour (200 mph), it became clear that the air cushion would not stay in place above these speeds and another solution had to be found.

The ram-wing craft did prove beyond doubt that the air cushion principle was a practical one and had advantages over wheels and other methods of transport in certain situations.

Early hovercraft - sidewall craft

The air cushion principle found an application in the form of a sidewall craft in 1963, reusing the plenum chamber principle of Thornycroft. The resultant craft was not able to leave the water because it was more of a boat but by using the plenum chamber and its air cushion effect hydrodynamic drag was significantly reduced.

An advantage of a sidewall air cushion vehicle over the more amphibious hovering craft is that water propellers can be used, effecting in greater steering control, especially at low speeds. Another positive effect was the greater stability of the craft as opposed to the circular skirt.

Hovercraft today and in the future

Early interest in hovercraft enjoyed a peak in the early 1960's as everyone jumped to take advantage of this amazing vehicle. However, by the end of the decade only the British had produced a range of feasible and practical craft.

The problems inherent of the air cushion vehicle, such as Cockerell and others had foreseen, regarding steering control, noise, salt and skirt erosion, caused many countries to abandon their hovercraft development programs in favour of other, more established multi-function vehicles or to use different vehicles specialised in each terrain or function.

Since the 1970's however, and especially over the last decade, a renewed interest in the hovercraft as (passenger) transport (see Hovercraft in Use), military transport and weapons carrier (see Military hovercraft) and exploratory vehicle (see Hovercraft news and development) has taken ground, solving many of these problems in their development (see Hovercraft Construction).

Technology in general made large steps forward during the past twentyfive years, enabling organisations and governments, as well as many enthusiasts (see Hovercraft Clubs) to enjoy the hovercraft vehicle in its many forms including the very popular Remote Control model size hovercraft! (See Model Hovercraft.)

As far as hovercraft and their spinoff technology is concerned the future looks ever brighter.
 

Ram-wing craft links

Build a simple but working paper model ram-wing craft according to instructions from the Syozo Kubo
Department of Applied Mathematics and Physics,
Faculty of Engineering, Tottori University,
Koyama, Tottori 680, JAPAN
See the different types of ram-wing vehicles and their uses at Infinity Technologies (KR) and at the WIG page from S.E. Technology. The basic ram-wing. (c) Tottori University, Japan. Links999 hovercraft history.
All you need to know about Alexander Lippisch and his ram-wing concepts at the e-library of the University of Iowa (USA). Complete list of WIG-craft and their specifications at Infinity Technologies (KR).
Kawasaki built an experimental Ram-wing craft in 1963 called the KAG-3. The Kawasaki KAG-3. (c) 1963 Kawasaki.
Hovercraft History & Museum (UK) Hovercraft Museum (UK)

The Ekranoplan Aquaglide.
The Russian ekranoplan Aquaglide.

The Icarus Wing In Ground Effect Vehicle developed for ice - Links999 hovercraft history.
The Russian Icarus WIG effect vehicle designed for use on the ice.

The Volga-2b WIG effect craft - Links999 hovercraft development.
The Volga-2B. Is it a plane, is it a boat? No, it's a WIG!

The Remote Control StarCruiser model hovercraft - Links999 model hovercraft.
The remote controlled RC-StarCruiser model hovercraft
from Starcruiser Enterprises.

Hovercraft Books and Information on construction, design and other issues


 

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