University of Guyana Faculty of Technology Department of Civil
Engineering
University of GuyanaFaculty of Technology Department Of Civil
EngineeringHovercraftAs modes of transportation have evolved over
the years, finding more efficient and economic ways of movement
have been the chief goals of developers. It is from this evolution
that the hovercraft arose.
Outline Of PresentationIntroductionHistoryModelsElements of a
Typical hovercraftDesign ConfigurationsOperation of the
HovercraftDesign ConsiderationsUse of the HovercraftEnvironmental
ImpactHovercraft in GuyanaConclusion
INTRODUCTIONWhat is a Hovercraft?
A hovercraft is an amphibious vehicle that can move with equal
ease on both land and water or any other terrain. It is also known
as an air cushion vehicle.INTRODUCTION
Hovercraft on landHovercraft on waterHISTORY1716 Emmanuel
Swedenborg (Swedish Designer & Philosopher)He first
conceptualized the idea of supporting a vehicle on a cushion of air
but his project was short lived and his craft never built. Mid
1870s Sir John Thornycroft (British Engineer)He developed the air
cushion effect idea further by building and testing a number of
models but no applications were found since the technology to
implement the concept did not exist at the time.1952 Sir
Christopher Cockerell (British Engineering)He invented the
hovercraft. He found the missing link that everyone else missed.
Developed the hovercraft principle further and got his idea
patented in 1955. With diligent work he was able to bring his idea
to reality with the first commercial hovercraft in 1959. From there
on the idea took with numerous developments with the vehicle.
ModelsBritish Aircraft manufacturer Saunders RoeSRN1The first
practical model to be made. It was powered by one (piston) engine,
driven by expelled air and could carry little more than its own
weight and two men.
The SRN1 During Trials in 1959ModelsSRN1
ModelsOther developments led to larger and more efficient
hovercrafts which can carry passengers such as the SRN2 to
SRN6.
SRN4ModelsOther developments led to larger and more efficient
hovercrafts which can carry passengers such as the SRN2 to
SRN6.
SRN6ModelsVickers VA-3This was the first true passenger carrying
hovercraft.
ModelsMany companies continued the development of the
hovercraft.British Hovercraft Corporation (Saunders Roe &
Vickers) UK Cushion CraftHovermarine
ELEMENTS OF A TYPICAL HOVERCRAFTHullThis is where the driver
operates the hovercraft and passengers or cargo are located. It is
the main body of the hovercraft which acts as the base for
attaching of the other parts.
ELEMENTS OF A TYPICAL HOVERCRAFTLifting SystemThis consist of a
centrifugal fan attached to a motor or an engine, which provides
air for the cavity underneath the craft (called the plenum chamber)
and also for filling the skirts.
ELEMENTS OF A TYPICAL HOVERCRAFTThrust SystemThis consists of
propeller or ducted fan that moves air from in front of the craft
and accelerates it out the back. This accelerated mass of air then
generates thrust which pushes the craft forwards.
ELEMENTS OF A TYPICAL HOVERCRAFTSkirtThis is the flexible wall
that is attached all around the bottom of the craft. The skirts
prevents the pressurized air from escaping from the plenum
chamber.
ELEMENTS OF A TYPICAL HOVERCRAFTEngineA typical hovercraft
typically uses one engine but larger sizes can use more sometimes
up to six engines. They usually utilized the typical marine engines
since they are quieter and fuel efficient.
ELEMENTS OF A TYPICAL HOVERCRAFTControl SystemThis consists of a
set of rudders that steer the craft by directing the air from the
thrust system toward either left or right which consequently steers
the craft.
ELEMENTS OF A TYPICAL HOVERCRAFTControl System
ELEMENTS OF A TYPICAL HOVERCRAFTAir BoxThis is a box like
structure at the rear of the hovercraft located behind the
propeller. It diverts some of the thrust air underneath the
hovercraft.
Design ConfigurationsThey can be designed with one or more
engines. One is used for driving the lift fan and the other used
for driving the thrust fans.
Some Hovercraft use the principle of ducting to allow one engine
to perform both lift and propulsion by directing some of the air to
the skirt and the rest of the air is passed out of the back for
thrust.
OPERATION OF THE HOVERCRAFTPrinciple of Operation
OPERATION OF THE HOVERCRAFTPrinciple of Operation
OPERATION OF THE HOVERCRAFTThe lift fan pushes a large volume of
air under the hovercraft which is prevented from escaping by the
skirt.As the fan continues to force air into this cushion, the
pressure under the hovercraft increases. When the pressure under
the hovercraft exceeds the weight of the hovercraft, the hovercraft
begins to rise off the ground this can be around 6 to 105 depending
on the size of the craft.Eventually the hovercraft raises high
enough to lift the skirt off the ground.Air begins to escape
through the gap between the ground and the skirt (called the
hovergap).At some point the hovercraft reaches equilibrium point at
which the amount of air being forced into the cushion can not
exceed the amount of air escaping through the hovergap.At this
point the hovercraft is hovering at its maximum hover height.The
hover height and hovergap which result at this stage can, with
certain limits, be adjusted through the design process.Fans mounted
on top creates thrust air which is used to propel the hovercraft
forward and moving the thrust air with rudders controls hovercraft
direction.
OPERATION OF THE HOVERCRAFTBrakes & SteeringSteeringSteering
is accomplished by use of the rudders. The rudders are placed at
the back of the craft in the direction of the thrust air flow. As
the direction of the rudders are changed so is the direction of the
craft.
BrakesHovercraft have no braking system. Simply reduce power
until the craft no longer hovers. Thrust reversers can be used.
OPERATION OF THE HOVERCRAFTFuel ConsumptionThis will depend on
the speed and other conditions which the craft is driven under. But
it uses less gas as compared to cars and boats under the same
condition. Hovercraft speed range is about 30-75 miles per hour. A
typical gasoline car averages 3.2 gallons per hour whereas an
average hovercraft gets about 2.8 gallons per hour.
OPERATION OF THE HOVERCRAFTSafetyThey have not been any major
accident involving hovercrafts. Only the occasional break down due
to lack of maintenance. Based upon information the hovercraft seems
to be one of the safest means of transportation.DESIGN
CONSIDERATIONSCarrying CapacityPressure = Force/AreaA bigger
hovercraft, one with a bigger overall area can carry more weight
than a smaller hovercraft with a fan the same size. Therefore, the
surface area should be kept as large as possible reducing the
pressure needed.Aerodynamic DragThis is the force that the thrust
must overcome. The drag can be reduced by reducing the frontal area
of the craft.
DESIGN CONSIDERATIONSThrustThe propellers used must be able to
overcome the aerodynamic drag.SkirtsDepends on the usage of the
hovercraft.Stability The location of the various components and
loadings so as not to overload any particular area which may make
the craft unstable.
Use of the HovercraftPersonal Use
Use of the HovercraftSearch & RescueThe hovercraft can
travel on virtually all terrain
Hovercraft life boatUse of the HovercraftSearch & RescueThe
hovercraft can travel on virtually all terrain
Hovercraft being used for a rescue operationUse of the
HovercraftMass TransportationPassenger ferries (goods,
vehicles)
Passenger-carrying hovercraft, off shore from ita AirportUse of
the HovercraftMass Transportation
The Hovertravel service between the Isle of Wight and mainland
England is currently the only public hovercraft service in the
United KingdomUse of the HovercraftRecreational PurposesSporting
activities
A Formula 1 racing hovercraftUse of the HovercraftResearch &
Military uses
A U.S. Navy Landing Craft Air Cushion, an example of a military
hovercraftENVIRONMENTAL IMPACTThe air cushion enables a hovercraft
to operate over environmentally sensitive areas such as muskeg or
mudflats without disturbing the surface. The ground pressure
exerted even by a fully loaded hovercraft is so low that the craft
can pass over bird eggs without breaking them. The lack of
disturbance on water minimizes the potential for bank erosion and
does not disturb swimmers or canoeists. Unlike many boats, engine
exhaust fumes are not directed into the water and poisonous
anti-fouling compounds are not required on hovercraft.They require
no docking mechanisms and can land safely on virtually any kind of
shore.Hovercraft in GuyanaCan Hovercrafts replace speed boats?Given
that:Can travel over the surface of the water without concern for
the depth or hidden obstaclesCan travel against the current of a
river with no reduction in speedThey are unaffected by small waves
and offer a comfortable smooth rideHave sufficient cushion height
to pass right over a person in waterCan come right up to the shore
even if there is no water
Hovercraft in Guyana
CONCLUSIONThe 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.
THANK U!
