Tuesday, 18 December 2012

Above the waterline propeller system debut

New Zealand based marine propulsion research and development company Contrapel Ltd has released details of its new propulsion system for boats.
The system is claimed to be capable of making future boats more economical, manoeuvrable, safer, stronger and better for the environment.
Shown to an enthusiastic marine industry for the first time at the recent Auckland On Water Boat Show, the Contrapel Hybrid Drive carries out all the functions of both propellers and waterjets with none of the drawbacks of either.
“The Contrapel technology is a propeller system working above the waterline, said Contrapel founder and managing director Barry Davies. “Externally it resembles a traditional waterjet, however internally the method for developing thrust has much more in common with conventional propeller systems.”
The Contrapel drive uses a pair of contra-rotating, fully enclosed hybrid propellers, capable of operating above the water line. The mode of operation of the hybrid propellers is to accelerate the water from out of the intake (pick-up) duct and then discharge it through the outlet, requiring only enough backpressure downstream from the propellers to keep the system primed. This contrasts with the traditional jet, which does not accelerate the water until further downstream in the nozzle section, which requires the generation of high pressure.
The Contrapel Hybrid propellers produce lift in a similar way to open water propellers, by using slippage. The use of hybrid propellers enables the mass component for each revolution be maximized and the plume velocity to be minimized. This contrasts with the low mass per impeller revolution and high-plume velocities present in conventional high speed waterjet designs.

According to Contrapel’s own on-water tests, the higher efficiency of the new system provides many improvements compared with boats that are equipped with traditional jet drive installations. These include improved thrust at low and mid speeds; better fuel economy at low and mid speeds due to improved control; the drive is highly survivable and operable in extreme conditions, including brown and black-water environments; it will lower global marine carbon footprint; and produces significantly lower noise and vibration levels.
The rotating speeds of the hybrid propellers are also very low, which generates the lower noise and also little wake turbulence. The Contrapel Hybrid Drive boasts ‘propeller-like’ thrusts at all speeds, but unlike propellers the Contrapel Hybrid Drive propellers are enclosed in a stainless steel tube that is screened to ensure objects cannot be ingested. This means that animal life, people and fragile seascapes are protected from damage.
Currently tested in 190mm, 270mm and 330mm diameter configurations, the Contrapel Hybrid Drive is able to suit a variety of marine propulsion applications and, it is claimed, will work on smaller leisure craft through to military vessels, shipping, workboats, dredgers and even for underwater submarines.
New Zealand’s Stabicraft Marine has been involved in the development of the Contrapel Hybrid Dive and, in conjunction with Contrapel Ltd, has fitted two Contrapel 330 units to a 10.2m Supercab rescue vessel.
Powered by twin Volvo-Penta D6 435 hp engines, the Stabicraft 10.2m weighs eight tonnes and carries 750 litres of fuel. It can achieve a fast cruise of 29.7 knots at 3,030rpm and reach a top speed of 37knots at 3,500rpm.

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