Our craft Lady Bernie excels in rough seas. Normal sea conditions in
Perth include south west winds of 20-25 knots with swells up to 3m and
1m breaking waves. Normal cruise in these conditions is at 20-25 Kts
with or across the wind.
Our craft has never broached. In swells over 4.5m, I demonstrate 360
degree spins down the face of the swell. Our craft has been airborne up
to 10 ft on many occasions. Re-entry into the water is cushioned by the
skirt with the hull seldom impacting on the sea, a feature of our skirt
With engine speeds above 2300 Rpm, all passengers can stand at the
edge of one side deck without the craft listing. List progressively
increases as engine Rpm is reduced to 500 Rpm.
Maneuverability is demonstrated by turning and stopping the craft in
less than two hovercraft lengths. This craft always leans into the turn,
a feature caused by the skirt design. Cruising under narrow bridges or
docking at jetties present no problems as a combination of varying Rpm
and a selection of forward and reverse thrust and rudder are used for
In commercial operations, the maximum recommended sea states is Force
Six. Operations outlined above have been for demonstration purposes by
our test captain and should never be attempted with fare paying
Passenger transfers at sea with other marine craft is best with both
vessels cruising at 5-10 Knots with the starboard or port skirt of the
hovercraft pressed hard against the hull of the other vessel. Both craft
tend to move up and down in tandem allowing passengers to be transferred
safely without fear of falling between the vessels. Such transfers must
be with the assistance of crews of both vessels. Our skirt design allows
substantial starboard or port side impact against other vessels, the
hard structure of the hull protected by the variable pressurised chamber
Passenger transfers to and from jetties are as per normal marine
Passenger transfers to and from beaches should be with the craft in
the water at the shore line with the engine at slightly above idle with
the skirt slightly inflated. This eliminates skirt and propeller wear
caused by sand and stone erosion thus reduces running costs.
The craft should be moored in the water or on especially prepared
level ground. This method eliminates skirt and propeller wear thus
ensuring many years of service from the craft. It should be noted our
craft are designed as marine hovercraft used for open ocean operations
thus do not use land operation fingered skirts which have proven to be
unsuitable for rough water use world wide. Fingered skirts for extended
land operations may be added to our skirt to allow extended land
operations per client requirements. All skirts are individually
replaceable at low cost.
Modular Power Unit.
The engine is mounted on anti vibration engine mounts with a constant
velocity (CV) shaft bolted to the engine flywheel with another CV
coupled to the centrifugal lift fan shaft thus eliminating 93% of engine
The lift fan shaft pulley drives a four blade 7 ft diameter
pitch-in-motion propeller, at a 3:1 reduction using a poly vee belt. An
engine speed of 2500 Rpm gives a propeller speed of 830 Rpm. This low
speed propeller design creates low sound signatures, requiring little
maintenance with a long service life.
Many passengers have been observed on the outside decks, carrying on
a Conversation at full speed. The propeller is manufactured from steel,
wood, and kevlar and has both forward and reverse thrust. It is
protected by a guard, which holds the three rudders in place. Plastic
covered galvanised steel mesh prevents passengers or cargo from touching
the propeller. These components are secured to rubber mounts, which are
bolted the frame.
The frame is secured the hull via four neoprene anti-vibration mounts
thus eliminating vibration from the hull. By undoing four bolts and
unplugging the electrical systems these modular power units are
interchangeable among all models in less than one hour. This feature
helps in mass production, reduces maintenance and down time.
Extra Modular power units are recommended when zero down time is a
The hull is manufactured from marine grade aluminium plate, 1.2m
wide, 8m long 2mm thick. This plate is bent longitudinally. The bent
plate is then welded longitudinally by an automatic welding process.
The skirt is made of hyperon nylon neoprene and is a special variable
pressurised chamber type designed and manufactured by Australian
Hovercraft Pty Ltd. This skirt was designed to operate in rough sea
conditions with a design life of 4,000 hours. Our current craft has
shown no skirt wear over a two year testing program with no skirt
maintenance. This design allows the hovercraft to travel high speeds in
very short seas.
Cruising speeds of 10 knots or more creates waves of 3mm inch,
causing no erosion to river banks. The propeller at cruising speed is
800 Rpm or less creates a low frequency sound that dissipates over a
short distance. Tests done with dolphins, sea lions, and birds at
nesting colonies have proven our hovercraft can get twice as close to
the animals as a boat of the same size (with an outboard motor) before
the behaviour of these animals' changes. Passengers often stay on the
bow, side decks or rear deck while the craft is moving and have been
unconcerned with the sound levels. The skirt design allows people
standing in waist deep water to have the hovercraft pass over the top of
them at 5 knots without injury. A diver 5 ft under the water cannot hear
the craft pass over them.
This craft is registered as a pleasure craft but can be built to full