1. The Skirt - The skirt traps air underneath the
craft. The skirt is made up of several individual pieces
called segments. Each skirt segment is attached to the craft's hull by
batons on the outer edge and by plastic cable ties on the hull's underside. They are attached
in this way so that they create a tight seal to prevent air loss and so that
they can mold and fit to the terrain the hovercraft is passing over.
Using segmented skirts also allows for individual replacement should it be
necessary. Skirts can take a lot of punishment. Should a skirt
become snagged on something, it is designed to break the plastic cable ties holding it in place
rather than tearing the skirt segment. If the wire ties break, the hovercraft's
air cushion will still be maintained since the neighboring segments will billow
out to fill the new gap. In an unusual situation where a hovercraft might
lose many skirts, it will still be able to hover. It is always recommended to
keep your skirt in the best condition possible to experience optimum
performance.
2. Steering - Viper Hovercraft use a motorcycle type handle
bar for steering. Turn right, the craft turns right. Turn left, the craft
turns left. The handle bar is connected by cabling to the rudders on the rear
of the craft. The air that is used for thrust passes over the rudders to provide
the directional control.
3. Seat - The seating is arranged on the craft's center line (inline) .This is to
allow for proper hovercraft trim. This prevents the craft from leaning to one side
or the other while carrying its operator and passengers.
4. Engine - Viper Hovercraft use the same engines used in light aviation aircraft. To be
used in aviation, these engines must be reliable or they wouldn't even be a
consideration. When properly maintained, these engines can run for hundreds
of hours before needing a overhaul.
5. Transmission - The power from the engine is transmitted to the fan by
a belt and pulley system. A small pulley is mounted to the engine's crank
shaft. A large pulley is connected to the fan shaft via a flexible
coupling. A timing belt is routed
from the pulley on the crankshaft to the fan pulley, thereby turning the fan.
6. Fan - The hovercraft's fan is made of plastic composite fan
blades and a aluminum hub. Viper Hovercraft
uses an integrated design, which means that one fan provides both thrust and lift.
7. Fan Duct - The fan duct also provides protection from
the rotating fan. In the unlikely event of the
craft rolling over, the fan duct also acts similar to a roll bar.
8. Rudders - Rudders are used to channel the thrust air either
left, right or straight ahead. The purpose of the rudders is to turn the
hovercraft. Experienced hovercraft pilots use both the rudders and leaning to
help the craft turn.
9. Elevators - Elevators are used to channel the thrust air either up, down or
straight ahead. The elevators are controlled at the cockpit by the operator. The
purpose of the elevators is to manually control the trim of the Hovercraft.
10. Splitter Plate - This plate splits the air that has passed
through the fan. The splitter plate is positioned behind the fan is set at
one quarter of the duct's opening. One quarter of the air is split under
the hovercraft for lift, while the remaining three quarters are diverted out the
back to give you thrust. The air that is used for lift passes under the splitter plate (the dividing
point separating lift and thrust air) and through the craft's hollow inner hull.
The air exits the inner hull through holes throughout the craft's perimeter,
each aligned with a skirt segment. This escaping air billows the skirt
segments and pressurizes the space between the ground and the craft's bottom
hull.
Viper Hovercraft can operate on mixed terrain including water, sand, gravel, mud, salt flats, snow,
ice, concrete and bitumen. No jetties or landing pads
are needed as the hovercraft can hover directly from the water up a sloping
surface such as a beach, bank or ramp. Viper Hovercraft can
operate in debris littered waterways where conventional vessels experience
difficulty. On land Viper Hovercraft can
operate over dykes and up banks providing there is a slope at the bottom. Viper
Hovercraft can operate in wind conditions of up to 25 knots, 500mm waves and 1.5m swell
at reduced speed
Hovercraft cannot operate over any surface which does not seal in the air
cushion. This includes cattle grids, small trees, small bushes and scrub. Operation may be limited on certain types of
stiff grasses and small plant due to air leakage through the foliage as the
stiffness of the plant may be sufficient to hold the hovercraft skirt away from
the ground surface. Do not consider buying a hovercraft if you can use a more conventional vehicle/vessel.
This is dependent upon a number of factors including the size of the craft, engine, load, surface,
environmental conditions and skill of the operator. Sometimes increasing the
engine power does not increase the maximum speed because the speed is limited by
the stability of the skirt system. As the hovercraft moves forward through the
air it encounters air resistance which exerts a pressure on the skirt at the
front. When the pressure approaches the same as the cushion pressure, the skirt
starts to loose structural stability and therefore becomes unstable. Typically a
high speed design will operate at a higher cushion pressure and conversely a low
pressure design will not be able to achieve high speeds. In all design
situations there is a trade off between many factors. Designing for high speed
alone would produce a hovercraft that was difficult to handle at low speeds and
may never be able to get over hump speed due to large wave making resistance
formed by a high cushion pressure.
Hovercraft do float but there are many small hovercraft which do not float well. Cheaply made hovercraft rely
on the displacement of the cockpit or hull to remain afloat, much like a small boat. These designs have a open plenum
chamber which allows water to enter drain holes located under the hull, relying on the cockpit shape to remain
buoyant.
If the cockpit is swamped with water, the hovercraft will sink. These designs may incorporate blocks of foam attached to the
cockpit sides, but in most cases, the foam buoyancy capacity is less than
adequate to support the hovercraft and/or the occupants.
Viper Hovercraft incorporate enclosed foam filled compartments which
surround the entire hovercraft. If the cockpit is fully swamped, the hovercraft will remain level and
afloat
as the buoyancy capacity is greater than the total weight of the hovercraft and payload.
Each country has its own licensing requirements and should be ascertained from the relevant
marine or air operators' authority. In Australia this is controlled by the
Department of Transport, Marine Division, such as NSW Services if you live in NSW. For private operation, an
ordinary boat license is required with a limit on craft size of up to 12 meters
length. For commercial operation, a coxswain's license is required which is
endorsed by the Australian Maritime Safety Authority after training on the specific
hovercraft (or commercial vessel) is undertaken by a recognized training authority. Further information
for commercial hovercraft requirements and commercial license
requirements can be found on the following link
www.amsa.gov.au.
If you have any questions relating to commercial hovercraft, survey or licensing, please refer to the AMSA.
Learning to operate a hovercraft has much the same level of difficulty as
learning to drive a car. Under guided instruction, a typical person can
learn the basics of operating a small hovercraft within a hour. To
become proficient at operating a hovercraft on a undulating surface will
take up to 3 hours. To become proficient at operating a hovercraft on
most surfaces and weather conditions will take up 20 hours. To be come
fully proficient will only happen with time and experience. Viper
Hovercraft can provide training.
Recreational Hovercraft Insurance for Australian Viper Hovercraft
Owners, other personal hovercraft and Hovercraft Club Members. Contact: Carl
Parrilla
Email: cparrilla@iaa.net.au or
phone: +61 407 881 634
Level 31, 100 Miller St
North Sydney NSW 2060
Website: www.insuranceadviser.net
For any vehicle to operate economically, the drag or resistance to motion, must be kept to a
minimum. On water, the majority of drag arises from the motion of the vessels
hull through the water; therefore we can reduce drag and consequentially
propulsive power by minimizing hull contact. The hovercraft achieves this by
using low-pressure air to form an air cushion underneath it, thus actually
lifting the hull clear of the water. In addition, by using air propulsion to
generate forward movement, the hovercraft becomes amphibious, and able to
traverse land, soft terrain or water.
Being amphibious, the hovercraft can use direct routes across sandbanks, marshes and flats, with
no loss of speed or comfort. Environmentally disruptive channel dredging
becomes unnecessary, whilst rivers and tidal estuaries present no problem for
the passage of the vessel. Previously inaccessible areas may be accessed
economically with little or no impact on their environment.
Hovercraft do not damage the
shore environment, such as beaches, mudflats and vegetation due to the hovercraft's low pressure footprint. For example, the average
human being when standing on a beach exerts a pressure of some 3lbs per square
inch underfoot, rising to 25lbs per square inch when walking. The average
hovercraft by comparison, exerts a pressure of approximately 1/3lb per square
inch on the surface regardless of speed. This "footprint pressure is less than
that of a seagull standing on one leg!
Hovercraft create virtually no under water noise, just atmospheric noise levels that would be
typical of a diesel truck or bus. The fact that there are no underwater
protrusions or propellers eliminates the usual thrashing noise signature
associated with conventional propeller driven craft, as well as negating any
possible seabed erosion when operating in shallow waters. It therefore
becomes obvious that fish and other marine life are in no way affected. This has been confirmed by independent scientific tests. The major noise
factor with any hovercraft is the propeller noise, which in any case is largely
directional in characteristic. Viper Hovercraft propulsion systems have been designed to
minimize
atmospheric noise.
There is no exhaust discharge into the water as with most conventional watercraft, thus
eliminating the pollution of the marine environment by oil and fuel particles,
particularly prevalent with outboard motor usage. The low friction with the surface, and subsequently low power requirements, the
hovercraft is in itself a fuel-efficient mode of transport, thus lessening the
pollution of the atmosphere even more.
The wake created
by the passage of a hovercraft is minimal, ensuring that riverbank erosion and
damage to foreshore by the waves created is virtually nil. A study in the
United Kingdom concluded that the passage of hovercraft over inter-tidal areas
caused no damage to sea grasses or invertebrates. It was also noted that bird
life rapidly adjusted to the presence of hovercraft. This has been confirmed on
the Gold Coast in Australia, where a commercial operator passed over the same
area of beach many times a day for more than four years without any affect to
the 'Yabbie' population actually living in the sands directly under the flight
path.
Some may ask, if a hovercraft is so simple, why is it expensive compared
to a Jet ski or a small boat? Well, for starters, hovercraft are not mass produced and not many
hovercraft are made world wide per year. Most, if not all Hovercraft are hand made
in small numbers, so production
costs, parts and running costs are higher than mass producers. In addition to this, the components
required to build a good design, such as light weight engines, precision drive
system components and high end fiberglass, carbon and Kevlar composites, come at a considerable cost.
Composites have been the life blood of Viper Hovercraft since the beginning.
We are constantly innovating, testing and improving our techniques as well as refining the production,
mechanical properties, and minimizing weight of our hovercraft designs.
Our team of in-house experts are proficient in all facets of composite construction.
What is a composite ?
A composite is defined as a structure containing two or more components, (in the case of
fiber reinforced composites this is the fiber and a resin).
A composite containing two types of fiber, e.g.. carbon and glass, is known as a hybrid composite.
A composite containing layers of fiber over both sides of ridged foam is a foam
composite sandwich.
Composites are broadly known as reinforced plastics. Specifically, composites are a reinforcing
fiber in a polymer matrix.
Most commonly, the reinforcing fiber is fiberglass, although high strength
fibers such as aramid and carbon are used in advanced applications.
The polymer matrix is a thermoset resin, with polyester, vinyl ester, and epoxy resins most often the choice of matrix.
Specialized resins, such as, phenolic; polyurethane and silicone are used for specific applications.
The benefits of composites:
High Strength: Composite materials can be designed to meet the specific strength requirements of an application.
A distinct advantage of composites, over other materials, is the ability to use many combinations of resins and reinforcements,
and therefore custom tailor the mechanical and physical properties of a structure.
Lightweight: Composites offer materials that can be designed for both lightweight and high strength.
In fact, composites are used to produce the highest strength-to-weight ratio structures known to man.
Corrosion Resistance: Composites provide long-term resistance to severe chemical and temperature environments.
Composites are the material of choice for out-door exposure, chemical handling applications and severe environment service.
Design Flexibility: Composites have an advantage over other materials because they can be
molded into complex
shapes at relatively low cost. The flexibility offers designers a broad range of design freedom, which is the hallmark of composite achievement.
Durability: Composite structures have an exceedingly long life span and exceptional fatigue properties.
Coupled with low maintenance requirements, the longevity of composites is a benefit in critical applications.
In a half-century of composite development, well-designed composite structures have yet to wear-out.
What is a composite
In the 1950’s, Sir Christopher Cockerel invented the first commercial hovercraft.
He constructed his first model to prove the concept of the design from two coffee tins and a hair dryer.
With the aid of this small working model Mr Cockerell convinced the British Ministry of Supply that his idea was practicable.
In 1956 he filed for a patent for his idea, and in 1958 the National Research and Development Corporation took over the project.
The NRDC ordered an experimental craft, the SR-N1, from Saunders Roe (Aviation) in the autumn of 1958.
The first flight of the SR-N1 took place at Cowes, on the Isle of Wight, on June 11, 1959.
The worlds First Hovercraft race was actually held on Lake Burley Griffin, Canberra, Australia in March of 1964.
The event was organized by the Canberra branch of the Royal Aeronautical Society.
The race was part of an aquatic festival and attracted over 25,000 thousand spectators.
This is an indication of the kind of public interest which can be aroused.
The main 'efficiency' race took place over a 1.6 mile course with competitors handicapped according to power, time and hover height.
Altogether, Fourteen hovercraft were in attendance but only Ten competed.
The race was not without incident. Most of the entrants found steering to be a problem,
causing many of the spectators to be splashed with water and dust.
When the engine of one craft failed, both the craft and driver disappeared beneath the surface of the lake.
The driver was eventually rescued.
