Lady Bernie

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Lady Bernie during her 2 years sea trial - she handles
choppy / rough waters over reefs with very little spray.
   
Beach to Shallows            Oop's - Swimmers!          Stable & List FREE
   
Panoramic Views          Free to move about!          Easily Trailerable
 

Performance 

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 design. 

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 exact positioning. 

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 passengers aboard. 

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 skirt. 

Passenger transfers to and from jetties are as per normal marine craft. 

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 vibration. 

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 priority.

 Hull. 

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. 

Skirt 

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. 

Environment 

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. 

Survey 

This craft is registered as a pleasure craft but can be built to full survey.

 

 

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Last Modified: July 04, 2005

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