World's first above-water propeller system

Kiwi company claims a first with a new jet/prop hybrid drive

Marine propulsion research & development company Contrapel Ltd has released details of its new propulsion system for boats. It claims the hybrid jet/prop drive is ready to make 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 is about to change boaters’ perceptions of jet drives and conventional propellers, it claims.

And not before time. The high-speed propeller was invented over 170 years ago, while water-jets have struggled to make significant inroads despite 60 years of development.

The new Contrapel Hybrid Drive claims to perform all the desirable functions of both propellers and water-jets with none of their drawbacks.

“The Contrapel technology is a propeller system working above the waterline. Externally it resembles a traditional water-jet, however internally the method for developing thrust has much more in common with conventional propeller systems,” says Contrapel founder and Managing Director, Barry Davies.

The Contrapel drive uses a pair of contra-rotating, fully enclosed hybrid propellers, capable of operating above the waterline. The props accelerate water from an intake or pick-up and then discharge it through the outlet, but require 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 and requires the generation of high pressure.

The hybrid propellers produces lift in a similar way to open-water propellers by using slippage, says Contrapel, enabling the mass component for each revolution to be maximised yet the plume velocity to be minimised. This contrasts with the low-mass per impeller revolution and high-plume velocities present in conventional high-speed water-jet designs.

According to Contrapel’s own on-water tests, the higher efficiency of the new system provides the following improvements compared with boats that are equipped with traditional jet drive installations:

- Vastly improved thrust at low and mid speeds

- Better fuel economy at low and mid speeds due to vastly improved control

- Highly survivable and operable in extreme conditions, including brown and black-water environments

- Will lower global marine carbon footprint

- Significantly lower noise and vibration levels

“Unlike the propeller, it’s a complete solution for the entire global industry, since it’s scalable to all sizes and works equally well above or below the water line,” Davies says.

The rotating speeds of the hybrid propellers are also very low, which generates low noise and little wake turbulence.

While the Contrapel Hybrid Drive is said to provide “propeller-like” thrusts at all speeds, its propellers are enclosed in a stainless steel tube that is screened to ensure objects cannot be ingested. This means that marine life and human appendages are protected from damage.

“Outboards, sterndrives, surface piercers, shaft drives, etc, are a liability when operating in unknown and shallow waters -- one strike and the craft is out of action,” Davies says.

“Exposed propellers are a danger to civilians and trained operators in the water and are extremely vulnerable to propeller strike with floating objects. But Contrapel eliminates all of those risks and liabilities,” claims Davies.

Where the Contrapel Hybrid Drive is also said to excel is with its benefits over high-speed water-jets. The system has a high tolerance to wear caused by small particles in the water, equating to minimal performance loss due to damage or wear.

Currently tested in 190mm, 270mm and 330mm diameter configurations, the Contrapel Hybrid Drive suits a variety of marine propulsion applications, and will work on smaller leisure craft right through to military vessels, shipping, work boats, dredging vessels and will even work for underwater submarines.

One of the world’s leading boat manufacturers, New Zealand’s Stabicraft Marine has been involved in the development of the Contrapel Hybrid Dive, and in conjunction with Contrapel Ltd it has fitted two Contrapel 330 units to a 10.2m Supercab rescue vessel.

Powered by twin Volvo-Penta D6 435hp engines, the Stabicraft 10.2m weighs eight tonnes and carries 750 litres of fuel. It can achieve a fast cruise of 29.7 knots @ 3030rpm and reach a top speed of 37 knots @ 3500rpm. See www.contrapel.com.

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World's first above-water propeller system

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