History of the Hovercraft
Introduction
1700 – 1900: The Genesis of Air Cushion
Vehicles
1900 – 1950: The Evolution of Air Cushion
Vehicles
1950 – 1964: The Birth of the Air Cushion
Vehicle/Hovercraft Industry
Air Cushion Vehicle Family Tree
Development of the Heavy Hovercraft Industry
Development of the Light Hovercraft Industry
Technical Trends in Light Hovercraft
Future of the Hovercraft
History of the Hovercraft
Authored and compiled by:
Christopher Fitzgerald
Chairman, World Hovercraft Organization; President, Neoteric
Hovercraft, Inc.
Introduction
Water: The Ancient Highway
The growth of civilization occurred within view of –
and in many ways because of – our seas and rivers. Since
the beginning of human history, we have been shaped by our
ability to carry goods and people across water – our
most ancient highway.
Without a means of water transportation, ancient mariners
could not have explored the world or traded goods. Civilizations
that mastered ship building and sailing inevitably prospered
as centers of trade, culture and power, and the earliest cities
were located on seashores or rivers. The superiority of water
transport over ground transport was so apparent to even the
earliest civilizations that canal building was one of mankind's
earliest engineering achievements.
In 1775 Adam Smith, the first economist, recognized the importance
of water transportation in his revolutionary book An Inquiry
into the Nature and Causes of the Wealth of Nations. In his
analysis of why some nations are more prosperous than others,
Smith examined the advantages of water over ground transportation
- one ship with six or eight men could carry as much as 50
wagons attended by hundreds of men and 400 horses - and concluded
that communication across water has always been the least
expensive form of transportation. Water travel requires less
manpower than overland travel and can accommodate far greater
loads than wagons, animals or more recent ground transport
vehicles.
Breaking the Water Barrier
Throughout history, mankind has been intent upon finding
ways to transport larger loads and to increase the speed of
load movement. From their inception, ground and air transport
vehicles have dramatically and continuously increased their
speed. Such is not the case with vehicles that travel across
water, because they have to contend with the strong resistance
of water – the water barrier.
One factor that creates the water barrier is water density.
The density of water is 815 times the density of air. As a
ship increases speed, the resistance of the water increases
exponentially, causing huge increases in power to achieve
only small gains in speed.
One method of describing transport efficiency is the movement
of a specific load over a specific distance in a specific
time. Speed equals distance divided by time; therefore, transport
efficiency is the movement of a specific load multiplied by
the speed at which it can be moved.
When a load is moved via water, the various resistances increase
as the velocity times itself, and the energy needed to affect
an increase in speed rises as the energy cubed, or energy
multiplied by itself three times (the exact power is 3.0)
This is a huge number.
Another way to think of this problem is to consider the lift-to-drag
ratio. The load has to float or be lifted by the water; this
results in drag (resistance) when movement commences. A boat
has a lift-to-drag ratio about ten times lower than a steel
wheel rolling on a steel rail. The only way to improve the
lift-to-drag ration of a boat is to lift the boat's hull and
load completely out of the water, which reduces wave production
and surface parasitic drag.
In a quest to
break the water barrier, to improve the lift-to-drag ratio
and decrease the resistance of water, many vehicles have been
invented, especially during the last three centuries. It is
an old idea to pump air under a ship's hull in order to reduce
resistance, but the obvious and simple approaches to this
idea do not work; the entire hull has to be lifted off the
surface. The majority of the modern inventions are based on
the idea of lifting the water displacement hull, or lifting
the load-carrying device out of the water. These include hydroplanes,
hydrofoils and air cushion vehicles. (The hovercraft is one
type of air cushion vehicle.) Among them, the air cushion
vehicle has the best lift-to-drag ratio of any device that
travels across water when speeds exceed 35 mph.
1700 – 1900: The Genesis of Air Cushion Vehicles
When it comes to flying machines, ideas easily date back
to ancient Greece. This is not the case with air cushion vehicles.
The first recorded design for such a vehicle was in 1716 by
Emanuel Swedenborg, a Swedish designer, philosopher and theologian.
Swedenborg's design appeared in the fourth edition of Sweden's
first scientific journal, Daedulus Hyperboreus, and is the
first detailed technical description of a flying machine of
any type.
Swedenborg's man-powered air cushion platform, basically
a circular aircraft, resembled an upside-down boat with a
cockpit in the center or a "flying saucer." His manually operated
device required the would-be pilot to use oar-like scoops
to push air under the vehicle on each downward stroke in order
to raise the hull out of the water. A working model of the
design was never built, because Swedenborg soon realized that
a human could not sustain the energy needed to power the oars.
His concept required a source of energy far greater than any
available at that time. As with many other forms of transportation,
significant progress had to wait until a lightweight motor
was developed in the nineteenth century.
In 1865, William Fronde of the British Admiralty sent a letter
to B. J. Tideman, who was the Chief Constructor of the Royal
Netherlands Navy, proposing the principle of air lubrication.
The letter is on display at the David Taylor Model Basin in
Washington D.C. and also appears on page 109 of J. Scott Russell's
book, The Modern System of Naval Architecture, 1865, Vol.
I.
In the mid-1870s, the British engineer Sir John Thornycroft
built a number of ground effect machine test models based
on his theory that an air cushion system would reduce the
drag of water on boats and ships. His theory was that if a
vessel's hull were designed with a concave bottom in which
air could be contained between the hull and the water, it
would create significantly less resistance. He filed a number
of patents involving air-lubricated hulls through 1877. The
internal combustion engine had not yet been invented, however,
so the technology required to power his inventions still did
not exist. In addition, no one had yet discovered a practical
solution to the problem of how to keep a cushion of air trapped
so it could not escape below a vessel.
In 1876, John B. Ward of San Francisco, California USA, suggested
an aluminum platform with rotary fans to drive air down and
backwards, but wheels would push the device along. He received
US Patents 185465 and 195860 for his "aerial machines."
The first patent for air lubrication in Great Britain was
issued to another Swedish engineer, Gustaf de Laval, in 1882
but because the method for retaining the cushion of air was
not yet resolved, de Laval was not successful with his experiments.
British Patent 5841 details a ship built with de Laval's ideas.
Information on this ship can be found on pages 33-34 in the
book Speed and Power of Ships by Admiral D.W. Taylor, published
in 1933.
In 1888, James Walker of Texas was granted US Patent 624271
in which channels along the underside of boats contained air
that would be captured in the adjacent channel as it tried
to escape. US Patent 608757, obtained in 1897 by Culbertson,
includes an idea that led to the first suggestion for sidewall
air cushion vehicles.
Air lubrication
has been applied to many industrial processes and applications,
including railways. The concept of a "sliding railway," a
train that rode on small hoverskirted pads using water under
pressure, was first proposed in 1868 by the French engineer
Monsieur Louis Girard. A working example was operated in 1886
for 900 miles in the LeJouchere Park. After Girard was killed
in the Franco-German war, one of his assistant engineers,
M. Barre, improved upon Girard's ideas and constructed a sliding
railway at London's Crystal Palace in 1891. The London News
hailed the invention as "a marvelous invention … a
singularly original contrivance for enabling trains to run
by means of waterpower at speed hitherto undreamed of …
something which may eclipse the electric motors."
1900 – 1950: The Evolution of Air Cushion Vehicles
Experiments with air cushion vehicles began in earnest after
a suitable power source, the engine, became a reality, and
after imaginations were fostered by the development of the
airplane. As the airplane evolved as a viable vehicle after
the renowned Wright Brothers flight in 1903, more attention
was paid to the fact that additional lift was created if an
airplane flew close to land or water, creating a "funnel effect"
or cushion of air. This became known as ground effect.
Realizing that pressurized air reacts against the surface
of water and enables a vessel to skim over the water rather
than through it, naval architects patented several designs
intended to solve the problem of water resistance, or hydrodynamic
drag. Onboard fans would force compressed air into a chamber
beneath, lubricating the hull with air from stem to stern,
which would raise it slightly above the water.
World War I brought the development of the airplane as a
military weapon which, in turn, fostered technological interest,
and scientists and innovators began exploring the ground effect/air
cushion effect in earnest.
Various forms of air cushion craft began to evolve after
the first working example was demonstrated in 1916. At that
time, Dagobert Muller von Thomamhul, an Austrian engineer,
designed and built an air cushion torpedo boat for the Austrian
Navy, which used fans to pump air beneath the hull to form
a lubricating air cushion. Further development was abandoned
when World War I destroyed the Austrian Navy and the empire.
During this same period of time, there were a number of prolific
inventors of air-lubricated boats. F.W. Schweder obtained
British Patent 4131 in 1906 in which improvements upon De
Laval's ideas were proposed. In 1907 Joseph Clark received
US Patent 989834 for an air vehicle. Charles Theryc of France
proposed yet another rail concept between 1902 and 1915, for
which he received British Patent 5569. These trains rode on
air and many patents were issued that dealt with air edge
seals. Two examples are US Patent 1152451 and British Patent
9011 of 1915. Another French inventor, M.A. Gambin, submitted
British Patent Application 188648 in 1921 for a sidewall-type
air cushion vehicle.
James Porter, a British engineer, received a series of patents
dating from 1908, including British Patent 21216 and US Patent
1016359. In 1913, Porter suggested a machine with ideas very
similar to annular jet air cushion air supply systems, and
received British Patent 975 in 1914, which shows an annular
duct quite similar to those of present day hovercraft.
Also in 1908, Charles Worthington, an American, suggested
a vehicle supported on air but riding in a conduit. A similar
proposal was made in 1913 by A.F. Eells, also an American.
Other early air cushion vehicle inventors in the United States
included F.G. Trask of North Dakota, who patented a sliding
railway in 1922; V.F. Casey of Minneapolis, Minnesota; and
Douglas Kent Warner of Sarasota, Florida.
In 1925, Casey received U.S. Patent 1621625 for the first
air cushion recirculation concept. His design featured a flat-bottomed
vessel with a series of longitudinal air channels open on
the underside by which cushion air could be returned.
Warner, the head of Warner Research Laboratories at Tamiama
Trail, Sarasota, Florida, carried out considerable research
and development on air-cushioned boats in the 1920s and he
held many patents; examples are US Patents 1819216, 2277620
and 2365676. To simplify his designs, which apparently experienced
wave-pumping problems, his machines incorporated the ram wing
concept. In 1929, Warner won boat races in Connecticut by
the use of the trapped air cushion or captured air bubble
principle on his sidehull craft. Warner's craft was the genesis
of the surface effect ship (SES) of today.
A.U. Alcock, an electrical engineer in Perth, Australia,
built a working model air cushion vehicle, which was demonstrated
to the press and government officials in 1912. Alcock called
his invention "Floating Traction," for which he received Australian
Patent 14309. He later demonstrated other models at the Cricklewood
Ice Rink in 1939.
In 1927, K.E. Tsiolkovski, a noted Russian scientist, developed
what today might be called the hovertrain. T.J. Kaario of
Finland built and tested a ground effect machine in 1935,
and received Finnish Patents 18630 and 26122. Other inventors
of air-lubricated boats during this period of history include
J.C. Hansen-Euehammer of Denmark, Henry Clay of London, Great
Britain and C.J. Lake of the United States. There were more
than 100 patents on this subject filed before 1962.
Soon after heavier-than-air flight began, it was discovered
that flying close to the surface, within the width (cord)
of the wing, requires less energy to remain in the air. This
became known as the ground effect phenomenon. Ground effect
is a function of the width of the wing; to take advantage
of the ground effect, any vehicle must fly above the ground
at an altitude less than the distance between the leading
and trailing edge of the wing.
The German Dornier DO-X twelve-engined flying boat proved
the reality of the air cushion ground effect in 1929 by crossing
the Atlantic Ocean entirely in ground effect at low altitude
close to the water. As a result, the aircraft's fuel consumption
decreased. During World War II, aircraft were flown to make
use of air cushion ground effect in order to extend reconnaissance
flight range.
American aviator
Charles Lindbergh is reported to have flown in ground effect
in order to conserve fuel during his historic transatlantic
flight in 1927. The challenge of flying along the wave tops
no doubt also served to stave off boredom during his long
journey!
These and other beginnings formed the foundation for the
various forms of air cushion supported vehicles that later
appeared on the modern scene. Not until the 1950s, however,
was a solution found for the problem that had thwarted all
previous attempts: how to retain the cushion of air beneath
the vessel.
1950 – 1964: The Birth of the Air Cushion Vehicle/Hovercraft
Industry
The successful use of the air cushion effect in World War
II aircraft inspired British, American, Russian and Swiss
engineers to seriously explore innovative ways to apply it.
The many experimental models that emerged prior to the 1950s
were developed as flying boats rather than true air cushion
vehicles, and they were known as ram wings as well as ground
effect machines. The terms air cushion vehicle and hovercraft
were not used until the late 1950s. For a complete diagram
of the many terms by which air cushion vehicles and hovercraft
have been known throughout the years, see Air
Cushion Vehicle Family Tree.
Serious practical development of today's hovercraft began
in the mid-1950s in Great Britain, when Christopher Cockerell,
generally accepted as the inventor of the hovercraft, began
to explore the use of air lubrication to reduce hydrodynamic
drag. Cockerell was a brilliant radio engineer who was retired
from the army and operated a boatyard on the Norfolk Broads.
During his lifetime, Cockerell was granted more than 70 patents
for his inventions, many of them dealing with hovercraft,
and he was knighted for his achievements.
Sir Christopher Cockerell's theory was that instead of using
the plenum chamber – an open-bottomed empty box such
as Thornycroft had devised – if air could instead be
pumped into a narrow tunnel around the perimeter of the underneath
side of the craft, it would flow toward the center, creating
a more effective air cushion. This peripheral jet would allow
the air pressure to build enough to equal the weight of the
craft and, since the air would be trapped, the pressure would
elevate the craft off the surface upon which it traveled.
Cockerell tested his theory with a test model constructed
of two empty cans, an industrial air blower and a pair of
kitchen scales. By inserting a cat food can into a coffee
can, and blowing air through the gap between the two cans,
he showed that it was possible to increase the hoverheight
and to construct a vehicle that could travel on a cushion
of air.
Originally, Cockerell had imitated previous designs that
used fans to force air down from the deck into the chamber
below, which meant that air had to be continually pumped back
in to replace the air that had escaped. He then devised a
new system: he made the hull of the craft concave and angled
air jets from the circumference in toward the center of the
craft to create a continuous air current. This effectively
solved the problems of retaining the air beneath the craft,
kept the air pressure stable and raised the hoverheight.
In 1955, Cockerell built a working model and was issued British
Patent 854211 for a vehicle that was "neither an airplane,
nor a boat, nor a wheeled land craft." Cockerell described
his invention as "a very expensive motorcar tire with a permanent
puncture." He named it the hovercraft, which he registered
as a commercial name, so it was not available for general
use until later when he generously handed the name over to
public domain.
This model, which illustrated his annular peripheral jet
system with inturned jets, led to the birth of the air cushion
vehicle/hovercraft industry. In his efforts to turn his invention
into a commercial product, Cockerell demonstrated it for British
military officials in 1956, who immediately classified it
as secret, effectively halting commercial development for
the next year.
As news filtered in that other countries were pursuing hovercraft
development, the government realized that Britain would sacrifice
its place as the world leader in this emerging technology
if development did not resume. Cockerell was then given permission
to approach the National Research Development Corporation
(NRDC), a government-financed agency who could back further
development if the hovercraft could be freed from the secret
list.
In 1958, Cockerell's invention was removed from the secret
list, permitting hovercraft development for civilian use;
the value of the hovercraft for military use had yet to be
demonstrated. The NRDC then contracted the Westland Aircraft
Company's Saunders-Roe division to build a full-scale research
hovercraft from Cockerell's concept, which was named the Saunders
Roe Nautical One (SR.N1).
On 25 July 1959 - fifty years to the day that Louis Bleriot
made the first crossing of the Dover Strait by airplane -
the world's first man-carrying hovercraft, the SR.N1, crossed
the English Channel from Calais, France to Dover, England.
The press turned out in force, and this amazing new invention
captured the world's attention.
The SR.N1 carried only three passengers. Cockerell traveled
as moveable ballast; Commander Peter Lamb piloted the craft
and John Chaplin served as engineer and additional moveable
ballast. Another mechanic failed to wake up in time and was
left in France. As of 2004, John Chaplin is still living and
resides in Virginia, USA.
Due to its low one-foot hoverheight, the SR.N1 was plagued
by wave impacts greater than one foot. Another British inventor,
C.H. Latimer-Needham, had followed Cockerell's developments.
He realized that the wave clearance problem could be solved
with a rubber skirt to contain the air cushion; a flexible
skirt would collapse temporarily when it impacted waves or
obstacles, then return to its inflated shape.
The introduction
of the flexible hovercraft skirt was a crucial engineering
breakthrough. The skirtless SR.N.1 of 1959 could only operate
on calm seas at low speeds. After the SR.N1 was fitted with
a 4-foot flexible skirt in 1962, it could cope comfortably
with 6-7-foot waves, cross marshland with gullies up to 4
feet deep and clear obstacles over 3 feet high. In addition,
the SR.N1 could now operate at twice its original weight with
no increase in lift power. Just one decade after the introduction
of Cockerell's hovercraft, its descendents, fifty times heavier
and three times as fast, would ferry a third of all passengers
and cars across the English Channel for some thirty years'
duration.
The Development of the Heavy Hovercraft Industry
With the introduction of the flexible skirt, the term air
cushion vehicle was first applied to this new and fascinating
invention, and ACV development was initially very rapid. The
advent of the flexible skirt launched hovercraft technology
and practical usage, and also defined the difference between
hovercraft and all other types of air cushion vehicles. The
flexible skirt fostered the inception of the air cushion vehicle/hovercraft
industry worldwide, from the introduction of 300-ton passenger/car
ferries moving more than two million passengers per year,
to the construction of massive hoverbarges, to amphibious
assault vehicles and LCACs (Landing Craft Air Cushion). SR.N1s
built in the US were first used by the United
States military in the Vietnam War.
In October of 2000, the Princess Margaret and the Princess
Anne, two of the world's largest hovercraft, were retired
after thirty years of ferrying tens of millions of passengers
across the English Channel. The Princess Margaret was featured
in the James Bond Film, Diamonds are Forever. Both Princesses
are now (2004) kept in service operational condition at the
British Hovercraft Museum at Gosport, Great Britain.
The Development of the Light Hovercraft Industry
After the rapid advances of the late 1950s and early 1960s,
the hovercraft industry began to develop into two distinct
categories: heavy (or large) hovercraft and light (or small)
hovercraft. For purposes of definition, size and payload (carrying
capacity) are used to distinguish light hovercraft from heavy
hovercraft. Although the distinction is somewhat arbitrary,
generally a light hovercraft is any vehicle that is wholly
supported on a cushion of air and has an all-up weight that
does not exceed 9.8kN (2,200 lbs.).
The unique mechanical curiosity, called a hovercraft by Sir
Christopher Cockerell, excited the world's attention. Saunders
Roe continued to manufacture heavy hovercraft, and other companies
developed their own versions. But the media attention, particularly
the heavy coverage by the British media, also enlivened the
imaginations of hobbyists and mechanically minded enthusiasts
everywhere.
Cockerell's hovercraft had all the appearance of a safe and
inexpensive new type of flying machine and many saw the hovercraft
as an affordable airplane. Experimenters who managed to construct
a hovercraft that could actually hover soon began to consider
manufacturing them as a business. This became a worldwide
phenomenon and occurred in university laboratories, backyards
and basements.
The evolution of small hovercraft was considerably influenced
by local environments, and shared many similarities to the
development of the sport motorcycle. European hovercraft began
to develop into fast, single engine racing machines suitable
for closed circuit racing, similar to the Café Racer
style motorcycle that also originated in Europe. Hovercraft
in the United States, however, followed a different course,
much like chopper classic street motorcycles. The wide open
spaces and bounty of long rivers in North America inspired
hovercraft that were suited for traveling in a straight line
and cruising with comfort. This difference can still be seen
in today's hovercraft races: the European models excel on
a tight, quick course, where the American models excel on
the straights.
Event though it was relatively easy to construct hovercraft
that would hover, they were still a long way from being workable
and even further from being designs that were capable of forming
the basis of a light hovercraft manufacturing business. Most
entrepreneurial enthusiasts soon lost their zeal. Until 1964,
light hovercraft were still quite crude, despite the major
technical improvements documented in the general and scientific
literature. What then happened in terms of development, starting
with the world's first ground effect machine (hovercraft)
race, was nothing short of amazing.
The World's First Hovercraft Race
In 1964 Canberra, the picturesque capital of Australia, was
about to celebrate the opening of its new man-made Lake Burley
Griffin. As part of the Canberra Day celebrations on Saturday
14 March 1964, the Canberra Branch of the Royal Aeronautical
Society planned and promoted a commemorative hovercraft race.
As N.F. Lamb, Chairman of the Canberra Branch of the RAeS
stated, "The Hovercraft was chosen as a project because success
is possible in this field by one man's personal efforts at
a very limited cost."
There were twelve entries in the world's first hovercraft
race, all of them from Australia. Eleven arrived at the site,
ten participated, and only five actually finished the race.
As journalist Eric Shackle reported, "Ten mostly backyard-built
mechanical hares and tortoises competed in the world’s
first hovercraft race … One of the amphibious hares
sank, three had to be towed ashore, and a tortoise was first
of only five to cross the finish line. The 10th failed to
start."
More than 30,000 spectators attended the event, and it received
extensive media coverage. Flight International magazine, London,
reported in its special supplement on air cushion vehicles:
March 14, 1964, may become a famous date in ACV history,
for on that day, at Canberra, the world's first competitive
hovercraft trials took place. They attracted 11 amateur
entries from all over Australia, ten of which were actual
starters. An analogy may be drawn between the Canberra trials
of 1964 and the Rheims air meeting of 1909: both mark the
beginning of competitive development in their respective
fields, with relatively primitive machines conceived by
enthusiastic experimenters. Personal ACVs stand now as aeroplanes
stood then, though enjoying the benefit of over 50 years'
development of reliable and lightweight engines.
The event was a remarkable success, considering that Australia
was remote from the technical developments occurring at the
time in Europe and the participants were largely isolated
with one another with little technical support or assistance.
It was well summarized by N.F. Lamb, who was also an official
at the race: "The trials were an outstanding success. They
illustrated the ingenuity of the individual to allocate sufficient
time and a little money to have a worthwhile hobby and make
a first class machine. The ACV races have helped sustain a
personal interest in aeronautics, which is extremely difficult,
considering the high cost of aeroplanes."
The resultant interest generated by the world's first hovercraft
race can be considered the initial stages of the light hovercraft
industry.
Light Hovercraft Development in Australia
The "individual enthusiast" phase of the history of light
hovercraft had already begun in Australia prior to 1964. Harold
Clisby, an early enthusiast, owned an engineering company
near Adelaide in South Australia, specializing in small air
compressors. During the 1960s he developed a simple single-fan
hovercraft with a 30 hp engine; it weighed about 230 lbs,
was 7 feet in diameter, and could hover 2 ½ inches
above the ground.
Another early experimenter, Chris Fitzgerald of Melbourne,
was originally inspired by the television news broadcasts
about the SR.N1 crossing of the English Channel. He began
building model hovercraft with a group of friends, among them
Rob Wilson, Arthur Boyd, Dennis Markham, Sam Ciliauro, Bernard
Sutcher, Peter Kolf, and Eddy Thomas, who called themselves
Hovercraft Research Organization.
Through his involvement in the Royal Australian Air Force
Cadet Air Training Corps, Fitzgerald became a cadet instructor
and formed a group within the Air Training Corps to experiment
with rockets, gliders and hovercraft. The group met on weekends
and established a workshop in one of the members' backyards.
Through Arthur Boyd, the group met David Atkins, as well
as an American design student studying for his Master's Degree
at Melbourne University who was interested in doing a study
of hovercraft. Through him, the group became involved with
the Mechanical Engineering School at Melbourne University
in 1962 and changed their name to Australian Air Cushion Vehicles
Development. At the same time, Chris Fitzgerald became employed
as a Technical Assistant with the Aeronautical Research Laboratories
in Melbourne, working full time on hovercraft-related experiments.
When the group learned that the Canberra Branch of the Royal
Aeronautical Society was inviting all hovercraft groups to
participate in the world's first hovercraft race, they decided
to enter the experimental hovercraft being developed at Melbourne
University. Their hovercraft, however, was plagued by mechanical
failure at the race and did not place. After the race, it
carried on as a useful research machine until it was cannibalized
and the remains were burned around 1972 in Hastings, Victoria.
The group built a series of experimental test models and
in 1966 moved their enterprise to the Fitzgerald family business
location in Melbourne. In 1969, they built a workshop in Hastings
near the mudflats and adjacent to the western port seashore.
As a result of these activities and the publicity they generated,
Chris Fitzgerald received a Rotary Foundation Award in 1969
that enabled him to travel the world for two years in order
to research the state of hovercraft development in numerous
countries. During this time he studied aeronautical engineering
at Farnborough Technical School in England and worked as an
intern at British Hovercraft for several months.
Upon his return to Australia, the group changed its name
and incorporated Neoteric Engineering Affiliates Pty. Ltd.
A new design was initiated and a prototype, called the Neova,
was developed, which gave the company a salable product. The
company's first income was derived from the sale of an information
package and do-it-yourself plans and instructions.
Because the Neova incorporated a number of technological
improvements, a plan was formulated to sell these innovations
to the new hovercraft manufacturers beginning to be established
throughout the world. To facilitate the project, Chris Fitzgerald
moved to Terre Haute, Indiana, USA in 1975 to establish the
company’s headquarters.
By mid-1976, it was evident that a hovercraft manufacturing
market for the company's technology did not exist, so the
plan was modified to establish a manufacturing base in Terre
Haute to initially sell hovercraft kit components. This evolved
into an operation that manufactured and sold the entire vehicle:
Neoteric Hovercraft, Inc., the world's original light hovercraft
manufacturer.
Light Hovercraft Development in North America
Even though Sir Christopher Cockerell of Great Britain is
generally accepted as the inventor of the hovercraft, there
exists some controversy over whether the first hovercraft
was actually developed in Great Britain or in the United States.
During the 1950s and early 1960s, at the same time as Sir
Christopher Cockerell's achievements in Great Britain, an
American inventor was following a similar path. Dr. William
Bertelsen, a general practitioner in Illinois with an engineering
background, had been seeking a practical method of alternative
travel that would allow him to make house calls to his rural
patients regardless of the weather.
Dr. Bertelsen first piloted his "flying aeromobile" in 1958,
eight months earlier than Christopher Cockerell's first flight,
and he filed United States Patents around the same time Cockerell
Filed British Patents. Popular Science magazine featured Bertelsen's
invention as the front-page story in its July 1959 issue.
Dr. William Bertelsen founded Aeromobile, Inc., still in operation
today, and continued to innovate and promote air cushion vehicles.
In 1996, Dr. Bertelsen and his creations were filmed by the
Discovery Channel as part of their Extreme Machines program.
A great transportation inventor and visionary, Dr. Bertelsen
was the recipient of the 2002 World Hovercraft Excellence
Award.
The geographical environment also influenced hovercraft development
in North America. In contrast with their British counterparts,
enthusiasts were scattered across great distances. Since both
the United States and Canada abounded in ideal hovercraft
operating terrain, with vast river systems, enthusiasts were
not as prone to get together to share selected sites, as was
the case in Europe.
Communication between enthusiasts was sporadic, typically
duplicating those of British publications. An Indiana USA
enthusiast, Jan Eglen, formed the National Association of
Air Cushion Vehicle Enthusiasts and published a newsletter
called The Kestral. Eglen resigned in 1973 and another enthusiast,
Rod McKeighan, transferred the club to Michigan and changed
its name to the American Hovercraft Association.
The Association was in disarray in 1975 when Chris Fitzgerald
moved his operation from Australia to Terre Haute, Indiana
USA, where he had become acquainted with Jan Eglen during
his Rotary Foundation world study tour. In 1976, Fitzgerald
established and organized the Hoverclub of America, Inc.,
which has since become the largest hovercraft club in the
world.
During the late 1960s and early 1970s, many attempts were
made at commercialization. Several hovercraft manufacturers
collectively produced approximately 3,000 hovercraft, which
were sold through dealers. Unfortunately, manufacturers drifted
away from their initial attempts to qualify dealers. Their
hovercraft, therefore, often fell short of customer expectations
and a great many hovercraft manufacturers did not succeed.
Nevertheless, a few American hovercraft manufacturers have
survived. Two of the most well known are Neoteric Hovercraft,
Inc. and Universal Hovercraft.
In 1976, Robert Windt formed Universal Hovercraft in Cordova,
Illinois USA. The company limited its sales to plans, propellers
and fans, and along with Neoteric Hovercraft, Inc. has survived
over the decades since their beginnings. Today, approximately
90% of all homebuilt hovercraft in the Hoverclub of America
are Universal Hovercraft designs. In 2003 Chris Fitzgerald
established DiscoverHover, a not-for-profit worldwide school
hovercraft program in which students can build a hovercraft
and compete in established hovercraft racing events. The free
hovercraft plans provided by DiscoverHover are updated versions
of Windt's Universal Hovercraft plans.
Light Hovercraft Development in Great Britain
In the early 1960s, the United Kingdom had an active group
of light hovercraft experimenters. Outstanding among these
was Jeff Harding, a mechanical engineer. In 1965 he proposed
that an organization should be formed and a race meeting should
be held so that individual enthusiasts would have the opportunity
to compare ideas and to compete.
Europe's first amateur hovercraft rally took place at Apethorpe
Hall, Northants. Lord Brassey, the owner of Apethorpe Hall,
was quite interested in hovercraft. This was the beginning
of the Hoverclub of Great Britain.
The winner of the race was Dan Reece. Reece had been the
only British competitor in the world's first hovercraft race
in Canberra in 1964. Reece went on to become the designer
for Hover Air, Ltd., a company formed by Lord Brassey in 1966.
Although the company eventually failed, it produced more than
100 Hoverhawk hovercraft, which were sold worldwide.
In the development of light hovercraft, Great Britain had
the distinct geographical advantage of being a small country;
enthusiasts lived within easy driving distance of each other
and could meet frequently to compare and exchange ideas about
their new machines. Great Britain, however, suffered a disadvantage
in comparison to other nations, in that there were very few
suitable areas for operating hovercraft. Most waterways and
canals had incredibly low speed limits, such as 5 km/h (3
mph) and were crowded by fisherman. Although coastal regions
were suitable for cruising hovercraft, the salt water meant
high maintenance for the craft.
As a result,
British Hoverclub members were forced to seek out suitable
private estates and regional government lands for their rally
activities. Many of these locations were subsequently developed
into a national circuit for hovercraft racing, with the better
courses located on the grounds of stately homes. Regulations,
safety rules, points scoring, and classification were developed
as courses were established. Regular rallies, hover-ins and
especially competitive trials set the stage for development
in the following decade. No other nation was so well equipped
for the evolution of the sport of light hovercraft racing
than Great Britain.
Technical Trends in Light Hovercraft
Engines
One of the first questions asked about hovercraft is, "What
kind of engine do they have?" Engines are a natural fascination
for anyone with a mechanical bent. The availability of suitable
lightweight engines has contributed much to the development
of light hovercraft.
Early designers used engines that were readily available
in their respective countries. Great Britain offered a wide
variety of small, lightweight, two-cycle engines. A few builders
used aluminum block automobile engines. American builders
tended to use chainsaw, lawnmower, snowmobile and air- and
liquid-cooled automobile engines.
The power-to-weight ratio of an automobile engine is such
that a fairly large machine is required just to carry the
engine; they also take up a great amount of space. Early hovercraft
designers and builders put an inordinate effort into adapting
engines and trying to persuade transmission and fan systems
to stay intact. During the late 1960s, since the United Kingdom
was well equipped with engines suitable for hovercraft, British
designers and builders were able to concentrate on operating
and testing hovercraft. This yet another reason why light
hovercraft evolved more rapidly in the United Kingdom during
that period than in any other nation.
The 1970s were the golden years of the snowmobile in America.
In 1971, North American sales soared to nearly half a million
units. Engine manufacturers, primarily in Japan, were developing
snowmobile engines with a power-to-weight ratio suitable for
hovercraft. Reliability, dependability and ease of starting
were improved with the introduction of capacitor discharge
ignitions, better materials and manufacturing tolerances,
and high performance resonance exhaust systems. These engines
began to find their way into hovercraft toward the end of
the decade. At the same time, trail bikes began to increase
in popularity and their engines, as well as those of go-karts,
were also adapted for use in hovercraft.
Fans and Propellers
As with engines, fans and propellers also fascinate hovercraft
enthusiasts, in fact, they represent a starting point for
many a would-be hovercraft builder. In the early days, much
of the hovercraft theory that abounded dealt with fans and
propellers. With decades of hindsight, what works best is
well known and most builders use commercially available fans.
Some of the heavier and larger light hovercraft use centrifugal
fans for lift, similar to those found in home heating and
air conditioning units. The axial flow fan, however, which
can be found everywhere for cooling, venting and circulating
air, has been found to be particularly suitable for hovercraft
because it efficiently moves large volumes of air at low pressures.
All amphibious light hovercraft are propelled by either fans
or propellers. The quantity of static thrust available to
accelerate a hovercraft is important. One measure of performance
is thrust efficiency, or the ratio of thrust per unit of power.
Air devices are notoriously inefficient when compared to tracked
vehicles or even water propellers. The highest efficiency
static thrust air devices are helicopter rotors. Next on the
efficiency scale comes propellers, followed by ducted axial
flow fans.
Safety considerations now dictate that a propeller must be
enclosed. A properly constructed wire cage is heavy and does
nothing for the appearance of a hovercraft, so most designers
prefer to enclose propellers in ducts. Since the late 1980s,
although both open and ducted propellers dominate the American
do-it-yourself market, ducted thrust fans are found on the
vast majority of light hovercraft in Great Britain and throughout
the rest of Europe. The ducted fan's universal appeal has
much to do with safety considerations as well as aesthetic
considerations.
Power Transmissions
Many types of power transmission have been employed in light
hovercraft over the years, but the most common is the toothed
timing belt. A more refined version is the HTD belt, which
can be found on most of the larger commercially manufactured
light hovercraft. Practically all hovercraft today are directly
coupled, except for the heaviest models in which various types
of clutches are utilized.
Controls
Larger hovercraft sometimes employ skirt-shift controls,
which move the inner skirt attachments to change the air cushion's
center of pressure and enable the craft to roll or pitch.
Such complications are unnecessary on lighter, smaller hovercraft.
Pilots and passengers in light hovercraft move about to adjust
trim as desired. This method, referred to as kinesthetic control,
is extremely important in small racing hovercraft. The pilot
must constantly shift his/her weight about to assist the craft
in operation while accelerating, decelerating or banking into
turns in order to prevent it from nose-diving into the water
("plowing in") or becoming airborne.
All light hovercraft are fitted with vertical rudder blades,
which are mounted in the fan or propeller slipstream, and
controlled through a steering wheel, joystick, or bicycle-style
handlebar. Some craft have horizontal elevators for longitudinal
trim. These are especially useful for hovercraft in which
the driver cannot readily move about.
When a hovercraft lift engine is separate from the thrust
engine, precise control over the air cushion is possible.
Such control helps to reduce dust and spray, minimizes skirt
drag, and makes it possible to adjust the skirt drag for braking.
This configuration also makes stationary hovering possible
(hovering in place without forward motion).
Neoteric Hovercraft, Inc. in the United States, owns the
patent for reverse thrust buckets, which not only improve
control, but also allows Neoteric models the distinction of
being the only hovercraft manufactured with the effective
capability of braking, backing up and hovering in place.
Skirts
The flexible skirt has had a profound effect on the practicality
of hovercraft and are essentially the base technology of hovercraft.
Most of today's skirt know-how was invented in Great Britain
during the mid-1960s. In the United States, the majority of
homebuilt hovercraft tended to use the non-flow bag skirt,
the simplest of skirts and the most rugged. However, bag skirts
have a tendency to bounce. British hovercraft started out
using bag skirts in the late 1960s, but by the 1980s most
were using segmented (finger) skirts constructed of neoprene-coated
nylon, which is superior to most other fabrics as hovercraft
skirt material.
Structures
The selection of building materials for hovercraft followed
a natural course. The first builders began by using wood,
which is still popular today. The majority of American homebuilt
hovercraft are made of wood. Some early builders used fabric-covered
structures, fiberglass (requiring expensive molds) and aluminum.
Some of the larger passenger-carrying hovercraft are aluminum;
others are composite fiberglass with a "foam sandwich" construction.
It
is not difficult to make light hovercraft structurally sound;
over the years there have been few examples of structural
failures. Structural stiffness in light hovercraft is not
critical because the structure is supported evenly by the
cushion pressure. Even the crudest hovercraft will work; masterful
craftsmanship and design are not critical to their successful
operation.
Today, most manufactured light hovercraft are constructed
from chopmat fiberglass. The hull is constructed on a mold
and then sandwiched between a urethane core and a fiberglass
body.
The Future of the Hovercraft
The hovercraft, no longer considered an obscure, impractical
vehicle, is in operation today throughout the world for a
great variety of purposes, including leisure sport and racing,
search and rescue, ice fishing, hunting, surveying, flood
control, environmental projects, agriculture, icebreaking,
water transportation, education and a myriad of other purposes.
The hovercraft industry, however, is still a wide-open area
for research and potential breakthroughs. Technically, light
hovercraft are poised to continue the advances developed during
the last few decades.
Small, light hovercraft have the potential for becoming primary
transport vehicles in many undeveloped areas. They can be
easily constructed onsite, and their versatility suggests
worldwide applications.
As the number of light hovercraft continues to increase throughout
the world, new applications will be found. Because hovercraft
are not as limited as snowmobiles geographically, their use
for racing, cruising, hunting and commercial applications
are likely to eventually exceed that of the snowmobile. Light
hovercraft should become a significant new vehicle in the
marine industry; their concept represents one of the few breakthroughs
in marine transportation since the hydrofoil or the very first
boat.
The future of light hovercraft for sport, recreation and
racing should be assured. Hovercraft racing has, not surprisingly,
become an established and growing international sport. Light
hovercraft make spectacular and unusually safe racing vehicles,
and are inexpensive compared to wheeled racing vehicles. Natural
tracks for hovercraft races exist in nearly every city in
the world, and a first-class hovercraft race needs little
more than some water and adjacent land, ice or snow.
The hovercraft has come a long way from the "flying machines"
of ancient Greece and Sir Christopher Cockerell's tin cans.
In the present day, hovercraft are attracting reawakened attention,
primarily because technological developments have led to greater
reliability and ease of operation. The last forty years of
development, in particular, have taken hovercraft technology
from the domain of great inventors and put it into the hands
of the public, from large corporations and the military to
young schoolchildren.
Anyone of any age who has ever dreamed of flying can now
experience that dream. Hovercraft kits are available for the
do-it-yourselfer and, even though there are still few hovercraft
manufacturers compared, for instance, to automobile manufacturers,
personal hovercraft can be purchased for less than the price
of a good motorcycle. Hoverclubs for private hovercraft enthusiasts
have been established in most major nations, and hoverclub
rallies and World Racing events attract growing numbers of
participants and spectators each year. Hovercraft are featured
in mainstream entertainment, such as James Bond films and
Junkyard Wars. Worldwide school hovercraft programs, such
as www.DiscoverHover.org, are taking this fascinating technology
into mainstream education.
The history of the hovercraft continues to be written. Today
and in the future, however, that history is being written
not only by inventors, engineers and movie studios. The history
of the hovercraft is now being written by your neighbors building
a hovercraft in their garage; by your local fire department
performing rescues; by your child building a hovercraft at
school; and by you. The opportunities may be slim for you
to go down in history as the inventor of a new vehicle or
as an Olympics winner. In contrast, hovercraft today and tomorrow
are very much an equal opportunity, available to everyone.
If you've ever wanted to fly, if you've ever wanted to race,
if you've ever wanted to become a part of history, now is
your time.
References:
The British Hovercraft Museum Trust, an online
encyclopedia describing the history of hovercraft;
www.hovercraft-museum.org
The History of Air Cushion Vehicles (from
1716); Kalerghi-McLeavy Publications, 1963; Leslie Herbert
Hayward, author.
History of Hovercraft – Pioneering
Vessels and People; U.S. Hovercraft Society; David Lavis,
Editor
Hovercraft Technology, Economics and Applications;
Elsevier, 1989; Joseph R. Amyot, editor; Christopher Fitzgerald,
contributor
The Speed and Power of Ships: A Manual of
Marine Propulsion; US Government Printing Office, 1933: Admiral
David W. Taylor, author.
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