Software and Systems Engineering Standards: Verification and Validation of Sy...
HOVERCRAFT / AIR CAUSHION VEHICAL
1. HOVERCRAFT
A SEMINAR REPORT
Submitted by
NIPRANCH SHAH
( 10ME001073)
In partial fulfillment for the award of the degree
of
BACHELOR OF TECHNOLOGY
IN
MECHANICAL ENGINEERING
DEPARTMENT OF MECHANICAL ENGINEERING
SIR PADAMPAT SINGHANIA UNIVERSITY, UDAIPUR-313601
MAY 2014
2. TABLE OF CONTENTS
CH. NO. TITLE PAGE NO.
ACKNOWLEDGEMENT i
LIST OF FIGURES ii
ABSTRACT iii
1. INTRODUCTION 1
2. HISTORY 3
3. CONSTRUCTION FEATURES OF HOVERCRAFT 6
4. HOVERCRAFT OPERATION 16
5. AERODYNAMICS 17
6. WORKING PRINCIPLE OF HOVERCRAFT 18
7. ADVANTAGES OF HOVERCRAFT 21
8. DISADVANTAGES OF HOVERCRAFT 21
9. APPLICATIONS OF HOVERCRAFT 22
10. SOME APPLICATIONS OF HOVERCRAFT 23
11. CONCLUSION 26
12. REFRENCE 27
3. SIR PADAMPAT SINGHANIA UNIVERSITY
UDAIPUR - 313 601
BONAFIDE CERTIFICATE
Certified that this project report “HOVERCRAFT” is the bonafide work of
NIPRANCH SHAH (10ME001073) who carried out the seminar work under my
supervision.
MR. NAVEEN KUMAR MR.LAKSHMI PRASAD
HEAD OF THE DEPARTMENT SUPERVISOR
Mechanical Engineering Department Mechanical Engineering Department
Sir Padampat Singhania University, Sir Padampat Singhania University
Udaipur Udaipur
4. i
ACKNOWLEDGEMENT
It gives me immense pleasure to express my deepest sense of gratitude and sincere
thanks to my highly respected and esteemed guide MR. LAKSHMI PRASAD
Department of Mechanical, SPSU Udaipur, for their valuable guidance,
encouragement and help for completing this work. Their useful suggestions for this
whole work and co-operative behavior are sincerely acknowledged.
I also wish to express my gratitude to MR.NAVEEN KUMAR, H.O.D. (Mechanical
Engineering) for his kind hearted support. I am also grateful to my teacher Mr.
PAWAN GUPTA for their constant support and guidance.
I also wish to express my indebtedness to my parents as well as my family member
whose blessings and support always helped me to face the challenges ahead.
At the end I would like to express my sincere thanks to all my friends and others who
helped me directly or indirectly during this project work.
NIPRANCH SHAH
(10ME001073)
5. ii
LIST OF FIGURES
S.no. Name of Figure Page.no.
1 A Hovercraft 1
2 A Hoverlloyd craft on the pad at Pegwell Bay Hoverport, 1973 4
3 Constructional Features 6
4 Lift fan in hovercraft 7
5 Thrust fan in hovercraft 8
6 Open Plenum vs. Momentum Curtain 9
7 Hovercraft as a lifeboat 11
8 Hovercraft engine 13
9 Air box in hovercraft 14
10 Rudders in hovercraft 15
11 Detailed view of hovercraft 16
12 Air flow in hovercraft 18
13 Personal use hovercraft 24
14 Lifeboat hovercraft 24
15 Passenger hovercraft 24
16 Racing hovercraft 25
17 Military hovercraft 25
6. iii
ABSTRACT
The air cushion vehicle or “HOVERCRAFT”, as it is popularly known is
the newest vehicle in today‘s transport scene. As well as being new, this vehicle is
different from other more conventional, terrestrial vehicle in that it requires no surface
contact for traction and it is able to move freely over a variety of surface while
supported continuously on a self-generated cushion of air. Though the concept is new,
the rate of development of hovercraft has been outstandingly faster than that of any
other mode of transport.
Modern Hovercrafts are used for many applications where people and
equipment need to travel at speed over water but be able load and unload on land. For
example they are used as passenger or freight carriers, as recreational machines and
even use as warships. Hovercrafts are very exciting to fly and feeling of effortlessly
traveling from land to water and back again is unique.
A hovercraft or air-cushion vehicle (ACV) is a craft designed to travel
over any smooth surface supported by a cushion of slow moving, high-pressure air,
ejected downwards against the surface below, and contained within a "skirt."
Hovercrafts are used throughout the world as a method of specialized
transport wherever there is the need to travel over multiple types of surfaces. Because
they are supported by a cushion of air, hovercraft are unique among all forms of ground
transportation in their ability to travel equally well over land, ice, and water. Small
hovercraft are often used in physical activity, combustion, or passenger service, while
giant hovercraft have been built for civilian and military applications to transport cars,
tanks, and large equipment into difficult or hostile environments and terrain.
7. 1
1. INTRODUCTION
Vehicles designed to travel close to but above ground or water. These vehicles
are supported in various ways. Some of them have a specially designed wing that will
lift them just off the surface over which they travel when they have reached a sufficient
horizontal speed (the ground effect).Hovercraft is such a vehicle.
Basically hovercraft is a vehicle that,
1. Drive like a car but
2. Flies like a plane.
3. It can hover over or move across land or water surfaces while being held off
from the surfaces by a cushion of air.
8. 2
4. Float like a boat.
A hovercraft, also known as an air-cushion vehicle or ACV, is a craft capable of
travelling over land, water, mud or ice and other surfaces both at speed and when
stationary. Hovercrafts are hybrid vessels operated by a pilot as an aircraft rather than
a captain as a marine vessel. Hovercrafts are usually supported by fans that force air
down under the vehicle to create lift, Air propellers, water propellers, or water jets
usually provide forward propulsion. Air-cushion vehicles can attain higher speeds than
can either ships or most land vehicles and use much less power than helicopters of the
same weight.
Hovercraft is a transportation vehicle that rides slightly above the earth’s
surface. The air is continuously forced under the vehicle by a fan, generating the
cushion that greatly reduces friction between the moving vehicle and surface. The air
is delivered through ducts and injected at the periphery of the vehicle in a downward
and inward direction. This type of vehicle can equally ride over ice, water, marsh, or
relatively level land
They operate by creating a cushion of high-pressure air between the hull of the
vessel and the surface below. Typically this cushion is contained within a flexible
"skirt". They typically hover at heights between 200 mm and 600 mm above any
surface and operate above 20 knots and can clear gradients up to 20 degrees.
The first practical design for hovercraft derived from a British invention in the
1950s to 1960s. They are now used throughout the world as specialized transports in
disaster relief, coastguard, military and survey applications as well as for sport or
passenger service. Very large versions have been used to transport hundreds of people
and vehicles across the English Channel whilst others have military applications used
to transport tanks, soldiers and large equipment in hostile environments and terrain.
9. 3
2. HISTORY
There have been many attempts to understand the principles of high air pressure below
hulls and wings. To a great extent, the majority of these can be termed "ground effect"
or "water effect" vehicles rather than hovercraft. The principal difference is that a
hovercraft can lift itself while still, whereas the majority of other designs require
forward motion to create lift. These active-motion "surface effect vehicles" are known
in specific cases as ekranoplan and hydrofoils.
The first mention in the historical record of the concepts behind surface-effect vehicles
that used the term hovering was by Swedish scientist Emanuel Swedenborg in 1716.
In 1915 Austrian Dagobert Müller (1880–1956) built the world's first "water effect"
vehicle. Shaped like a section of a large aerofoil (this creates a low pressure area above
the wing much like an aircraft), the craft was propelled by four aero engines driving
two submerged marine propellers, with a fifth engine that blew air under the front of
the craft to increase the air pressure under it. Only when in motion could the craft trap
air under the front, increasing lift. The vessel also required a depth of water to operate
and could not transition to land or other surfaces. Designed as a fast torpedo boat, the
Versuchsgleitboot had a top speed over 32 knots (59 km/h). It was thoroughly tested
and even armed with torpedoes and machine guns for operation in the Adriatic. It never
saw actual combat, however, and as the war progressed it was eventually scrapped due
to lack of interest and perceived need, and its engines returned to the Air Force.
The theoretical grounds for motion over an air layer were constructed by Konstantin
Eduardovich Tsiolkovskii in 1926 and 1927.
10. 4
(A Hoverlloyd craft on the pad at Pegwell Bay Hoverport, 1973)
In 1929, Andrew Kucher of Ford began experimenting with the "Levapad" concept,
metal disks with pressurized air blown through a hole in the center. Levapads do not
offer stability on their own, several must be used together to support a load above them.
Lacking a skirt, the pads had to remain very close to the running surface. He initially
imagined these being used in place of casters and wheels in factories and warehouses
where the concrete floors offered the smoothness required for operation. By the 1950s,
Ford showed a number of toy models of cars using the system, but mainly proposed its
use as a replacement for wheels on trains, with the Levapads running close to the
surface of existing rails.
11. 5
In 1931, Finnish aero engineer Toivo J. Kaario began designing a developed version
of a vessel using an air cushion and built a prototype Pintaliitäjä (Surface Soarer), in
1937. Kaario's design included the modern features of a lift engine blowing air into a
flexible envelope for lift. Kaario never received funding to build his design, however.
Kaario's efforts were followed closely in the Soviet Union by Vladimir Levkov, who
returned to the solid-sided design of the Versuchsgleitboot. Levkov designed and built
a number of similar craft during the 1930s, and his L-5 fast-attack boat reached 70
knots (130 km/h) in testing. However, the start of World War II put an end to Levkov's
development work.
During World War II, an engineer in the United States of America, Charles Fletcher,
invented a walled air cushion vehicle. Because the project was classified by the U.S.
government, Fletcher could not file a patent.
In the early 1950s the British inventor Christopher Cockerell began to experiment with
such vehicles, and in 1955 he obtained a patent for a vehicle that was "neither an
airplane, nor a boat, nor a wheeled land craft." He had a boat builder produce a two-
foot prototype, which he demonstrated to the military in 1956 without arousing
interest. Cockerell persevered, and in 1959 a commercially built one-person
Hovercraft crossed the English Channel. In 1962 a British vehicle became the first to
go into active service.
12. 6
2. CONSTRUCTIONAL FEATURES OF HOVERCRAFT
1. Radar: apparatus that detects objects through the use of microwaves.
2. Pylon: supporting post.
3. Dynamic propeller: two-bladed apparatus that provides motion.
4. Fin: steering device.
5. Rudder: apparatus that prevents drift.
6. Lift-fan air intake: opening to allow air to enter.
7. Main level drive gear box: compartment that contains and protects the gear
mechanism.
8. Skirt finger: part of the flexible skirt.
9. Passenger entrance: opening on the side wall that provides access to the
passenger cabin.
10. Flexible skirt: lower flexible part.
11. Bow door ramp: opening at the front.
12. Control deck: cubicle from which a hovercraft is operated.
13. 7
1. LIFTING FAN
(LIFT FAN IN HOVERCRAFT)
The volume of air needed is very large and a propeller is designed to be most efficient
in open air like on an aircraft. Also the fan needs to force air into the chamber below
the craft so creating a specific pressure under the craft. Propellers again are not efficient
in applications when an air backpressure will be applied to the propeller blades as they
rotate. Because of this the lifting fan on most Hovercraft uses what is known as a
centrifugal fan. This is a fan in which two discs and fitted together and looks rather
like a doughnut with angled slats at their edges.
When the assembly is rotated at high-speed air is sucked into the center hole in the fan
and the slats force it out at the edges. The advantages of the fan are twofold. They
operate efficiently in an environment when backpressure is high and they will move
larger volumes of air for a given rotation speed than a propeller with the same speed
and power input. The lifting fan is coupled via a gearbox to the engine. The engine
also drives the propeller on the craft, which provides thrust for forward motion of the
Hovercraft.
14. 8
2. THRUST PROPELLERS
(THRUST FAN IN HOVERCRAFT)
The propeller used to drive the hovercraft along is usually an aircraft type with variable
pitch blades. Its speed of rotation must remain fixed to that of the engine and the lift
fan. This is because the amount of lift air required dictates the engine speed to drives
the lift fan. In turn the amount of propulsion, which the propellers provide, must be
obtained by varying the propeller pitch and not its rate of rotation. This system is
termed 'integrated lift/propulsion'. A Hovercraft having more than one lift fan and
propeller generally has a separate engine for each fan-and propeller unit.
The propellers used on hovercraft can vary from four-bladed versions and about nine
feet in diameter on the smaller craft to the four propellers on the SRN4 cross-Channel
hovercraft. These are four-bladed and nineteen feet in diameter! On the SRN 4 the
pylons on which they are mounted can be rotated to change the direction of thrust. On
smaller craft, rudders like on aircraft, are used for direction control.
15. 9
3. MOMENTUM CURTAIN
When early models were built and analysis was done on the airflow using the plenum
chamber type of hovercraft it showed that there were problems with stability. In
addition the craft would require enormous power to maintain a reasonable hover
height. Stability of the hovercraft on its cushion of air remained a real problem despite
some design efforts and a new approach was needed. To solve these problems, a
plenum chamber with a momentum curtain was developed by Sir Christopher
Cockerall.
(Open Plenum vs. Momentum Curtain)
Cockerell used the idea of pumped air under a hull (this then becoming a plenum, i.e.
the opposite of a vacuum) and improved upon it further. Simply pumping air between
a hull and the ground wasted a lot of energy in terms of leakage of air around the edges
16. 10
of the hull. Cockerell discovered that by means of generating a wall (curtain) of high-
speed downward-directed air around the edges of a hull, that less air leaked out from
the sides (due to the momentum of the high-speed air molecules), and thus a greater
pressure could be attained beneath the hull. So, with the same input power, a greater
amount of lift could be developed, and the hull could be lifted higher above the surface,
reducing friction and increasing clearance. This theory was tried, tested and developed
throughout the 1950s and 1960s until it was finally realized in full-scale in the SR-N1
hovercraft.
17. 11
4. HOVERCRAFT SKIRT
(Hovercraft skirt of a Hovercraft lifeboat)
Despite the momentum curtain being very effective the hover height was still too low
unless great, and uneconomical, power was used. Simple obstacles such as small
waves, or tide-formed ridges of shingle on a beach, could prove to be too much for the
hover height of the craft. These problems led to the development of the 'skirt'.
The skirt is a shaped, flexible strip fitted below the bottom edges of the plenum
chamber slot. As the hovercraft lifts, the skirt extends below it to retain a much deeper
cushion of air. The development of the skirt enables a hovercraft to maintain its normal
operating speed through large waves and also allows it to pass over rocks, ridges and
gullies.
18. 12
The skirt of a hovercraft is one of its most design sensitive parts. The design must be
just right or an uncomfortable ride for passengers or damage to the craft and the skirts
results. Also, excessive wear of the skirt can occur if its edges are flapping up and
down on the surface of the water. The skirt material has to be light flexible and durable
all at the same time.
For the skirt to meet all of its requirements the design and use of new materials has
slowly evolved. The current skirts use ‘fingers at the lower edge of the skirt envelope
which can be unbolted and replaced. By doing this there is a quick and easy way to
counter the effects of wear without having to replace the whole skirt structure. A
shocking example of the costs is the replacement of the skirt assembly on the SRN 4’s
which used to cross the English Channel from the UK to France. The replacement cost
for a set of skirts for this craft is over 5 million US Dollars.
19. 13
5. THE ENGINE
(diesel engine of a hovercraft)
The SRN 1 and other early hovercrafts used piston type engines and gas turbines. This
type of engine is smaller and lighter for a given horsepower and has been used
extensively in turbo prop aircraft.
The engine has a main shaft on which is mounted a compressor and a turbine. A starter
motor is connected to one end of the shaft and the other end is connected to the lift fan
and propeller gearboxes. Both compressor and turbine look like fans with a large
number of blades.
When the engine is started, the compressor compresses air from the engine intakes and
pushes it into combustion chambers mounted around the engine. Fuel is squirted into
the combustion chambers and ignited. The compressed air then rapidly expands as it
is heated and forces its way out through the turbine to the exhaust. As the gas pressure
rises, the turbine speeds up, thereby driving the compressor faster. The engine speed
increases until it reaches the engine's normal operating speed.
However, the use of these engines results in a very high level of engine noise outside
the craft. Also uses marine diesel engines that are much quieter and fuel efficient.
20. 14
6. AIR BOX
(Air box in hovercraft)
The box-like structure at the rear of the hovercraft, right behind the propeller, the box-
like structure is called an air box. The air box takes about 10% of the air being pushed
backward by the propeller and forces it downward, underneath the hovercraft. There
are three small ducts cut into the base of the hovercraft, underneath the air box. Two
of these ducts lead into the skirt, which is basically a bag that goes all the way around
the perimeter of the craft, while the third duct leads directly underneath the hovercraft.
21. 15
7. RUDDERS
When the hovercraft is finally able to move it will most definitely require steering
capabilities. This is achieved through the use of rudders. These rudders can be
controlled by a variety of devices including computers. The rudders must be well
weighed out in order to avoid weighing down your hovercraft and also well shaped in
order to move air as efficiently as possible.
Rudders cannot be too heavy otherwise they will weigh down the craft because they
are located very close to the motor. The shape of the rudder dictates how well it will
be able to move air.
22. 16
4. HOVERCRAFT OPERATION
Piloting a hovercraft is an interesting proposition. Since very little of it actually touches
the ground, there isn't much friction, making it very difficult to steer and also very
susceptible to strong winds. Imagine trying to drive around on top of an air-hockey
puck! We've discovered that the best way to drive it is treat it like a jet ski, i.e. leaning
back and forth and steering very carefully. It is also possible to do a 360-degree turn
without stopping, which is quite a sight.
23. 17
5. AERODYNAMICS
Aerodynamics is defined as the branch of fluid physics that studies the forces exerted
by air or other gases in motion. Examples include the airflow around bodies moving at
speed through the atmosphere (such as land vehicles, bullets, rockets, and aircraft), the
behavior of gas in engines and furnaces, air conditioning of buildings, the deposition
of snow, the operation of air-cushion vehicles (hovercraft), wind loads on buildings
and bridges, bird and insect flight, musical wind instruments, and meteorology. For
maximum efficiency, the aim is usually to design the shape of an object to produce a
streamlined flow, with a minimum of turbulence in the moving air. The behavior of
aerosols or the pollution of the atmosphere by foreign particles are other aspects of
aerodynamics.
24. 18
6. WORKING PRINCIPLE OF HOVERCRAFT
Hovercrafts work on the two main principles of lift and propulsion. When dealing with
a hovercraft, the existence of lift is imperative for the proper function of the vehicle.
Lift is an essential factor because it is that which allows the craft to ride on a cushion
of air several inches off the ground. This process, the process of attaining lift begins
by directing airflow under the craft.
25. 19
In order to quarantine the air under the air cushion, a skirt is required. This is done in
order to create pressure under the hovercraft which forces the vehicle off the ground.
Attaining the proper amount of airflow is imperative for the maintenance of the crafts
stability. If too much airflow is directed under the craft, it will then hover too high
above the ground, resulting in the hovercraft to tip. Not enough lift will cause the craft
to remain on the ground which defeats the very purpose of the hovercraft altogether.
The source of the airflow which propels the craft of the ground is a fan. The fan can
be used for lift and thrust. It can be dedicated to lift or thrust or even both
simultaneously. In either case the passage where the air flows through to reach the air
cushion affects the stability of the hovercraft. This passage is a hole located on the base
of the craft. Another vital component is the motor. The motor is usually located in the
rear of the vehicle and is the heaviest of the components. Due to the weight of the
motor, extra pressure is required under the area where the motor is positioned in order
to attain hovering capabilities.
It is different from other vehicles of its category is that very little force is required for
it to move. Propulsion is that which makes the craft move. The source of this effect is
the fan, which is used to move the air for propulsion. The fan produces more than
enough force for the hovercraft to move. Hovercrafts have no contact with the ground;
therefore any resistance the ground may produce under other circumstances is now
non-existent for the craft. As explained above, the propulsion of the craft requires a
fan but a normal fan is not sufficient. This is because a normal fan does not blow air
straight back. Instead it spins the air in a spiral shape. Therefore engineers decided to
use turbines or stationary blades, that un-spin the air. When air does not spin more of
its kinetic energy can be used for translation and less is required for rotation.
26. 20
The shape of the body also affects the stability of the hovercraft. The larger the area of
the base, the more stable it will be. Wider base implies greater stability. Longer and
narrower shapes increase speed but decrease stability. Most hovercrafts have rounded
ends, and offer both stability and speed.
The skirt is another vital component. The common skirt is known as a bag skirt. It is
comprised of a bag that covers the bottom of the base and has holes in it to allow air
to escape and push the craft off the ground. Each part of the skirt inflates independently
which makes repairs much easier and improves stability. Unfortunately, the more
stable a skirt, the slower it will go.
When the hovercraft is finally able to move it will most definitely require steering
capabilities. This is achieved through the use of rudders. These rudders can be
controlled by a variety of devices including computers. Rudders cannot be too heavy
otherwise they will weigh down the craft because they are located very close to the
motor. The shape of the rudder dictates how well it will be able to move air.
27. 21
7. ADVANTAGES OF HOVERCRAFT
1. Can carry a relative size payload.
2. Can be launched from ship (ex: interception, deploying troops to shore from a
carrier, travel where larger/mother vessels cannot).
3. Travel over any surface.
4. Shortcutting routes.
5. Travel Rivers up as fast as down, irrespective of the current.
6. Travel in dry water-beds.
7. No collision with debris, logs etc.
8. Access to 75% of coastal area instead of only 5% with conventional vessels.
9. Hovercrafts are very fuel efficient (CO² friendly) as Hovercraft do not have to
plough through the water but "fly" above the surface. At maximum speed fuel
consumption of a Hovercraft is approx. 70% less than of a fast patrol boat with
similar payload capacity.
10. No turbulence or impact in water as no propeller churns up the water so sea life
remains untouched.
11. Travel in dry water-beds independent from harbors, piers and jetties.
8. DISADVANTAGES OF HOVERCRAFT
1. They move a lot of air and can be relatively loud.
2. Steep grades can be issue.
3. Potential of skirt damage/puncture.
4. Not exactly agile (e.g.: cornering).
5. The Hovercraft is bulky and its high speed makes it difficult to control while on
land.
28. 22
9. APPLICATIONS OF HOVERCRAFT
1. Downdraft associated with helicopters, & a fraction of the cost to purchase,
operate & maintain. Rescuers can reach floods, mud, and sand & ice victims
without exposing rescuers to life threatening danger.
2. Distribution of famine or flood aid support craft. Relief work (United Nations).
3. Civil emergency & infrastructure support
4. Oil industry survey, exploration & pipeline patrol.
5. Electrical Power-line patrol & safety.
6. Remote mining access support vehicle.
7. River, lake & port geological surveys.
8. Mud & riverbed sampling.
9. Environmental projects & clean-up operations.
10. Airport bird scaring/support/rescue services.
11. Coastal civil engineering & bridge construction & repair/maintenance.
12. Transport, service & safety craft for river & low tide coastal work where 24-
hour access is vital for staff safety.
13. Fish farm & low tide access.
14. Leisure & family fun. Rental Operations, Corporate entertainment. Education,
schools. Summer fetes & shows.
15. Access to Riverside, lakeside & island properties. Hovercraft travel over mud,
sand & ice. Hovercrafts are not restricted by tide, or fast running water. Or shallow
water, or submerged rocks, coral, or marine life.
16. Super Yacht Tenders
17. Filming & TV work. Store sales & advertising (Harrods).
18. It can be used on fast flowing water e.g. flooded rivers as current has little Effect
on craft when hovering. This means the pilots able to maintain speed and direction
or even remain stationary, maintaining position to carry out Rescues etc. without
29. 23
fighting the water current. Can be launched onto rivers and floodwater without use
of a slipway Providing a reasonably low bank can be accessed. No need to back a
trailer down into the water. The hovercraft can be flown (or reversed) in. Hovercraft
can be operated over underwater obstructions such as fences, Walls and debris
without hindrance and there is no propeller to foul. No propeller in the water means
less risk to casualties in the water or crew when working close to the craft. Extreme
maneuverability and controlled reverse capability as well as the ability to stop
quickly means this type of hovercraft can be operated in Confined spaces such as
narrow streets and flooded caravan sites. Hovercraft can be used on mixed surfaces
where boats cannot be effective.
32. 26
11. CONCLUSION
The hovercraft is in operation today throughout the world for a variety of purposes and
its use is growing giving raise to new and improved designs resulting in greater
applications.
With its safety and adaptability it can become one of the most important and
economical means of transport in the future
Hovercrafts are generally simple mechanisms in theory. Yet the process from theory
to manifestation is not as easy as it may seem. A plethora of problems exist and must
be faced in order to attain a well-functioning hovercraft. The plans and designs must
be flawless. One must take under consideration the weight and the shape of each
component in order to avoid problems such as instability and dysfunction. This is a
marvelous machine which greatly cuts down the friction which in turn helps it to attain
greater speed and more stability. Varieties of problems and factors have to be taken
into account in designing and constructing a hovercraft. The difficulties involved in
maintaining stability and functional competency has limited the application to only
transportation or for military purpose. The cost involved in the developing of a
hovercraft is also another impediment to the widespread use of this machine.
.
