Rolls-Royce notes increased interest in Azipulls
By IBI Magazine/David Foxwell
Rolls-Royce says it is seeing a significant level of interest in its innovative Azipull propulsor from the superyacht industry. Since its first application in ferry propulsion in 2004, the Azipull azimuth thruster from Rolls-Royce has been welcomed into several markets, with well over 100 units now in service.
The Azipull thruster takes the mechanical elements of a gear-driven azimuth thruster and puts them into a quite different hydrodynamic package. A pulling propeller - CP or FP - is mounted ahead of the leg, which is a hydrodynamically optimised streamlined unit incorporating the gear house and a lower fin. The leg/housing/fin combination recovers swirl energy from the propeller slipstream which would normally be wasted, converting it into additional forward thrust. At the same time the underwater unit has more rudder effect than a conventional azimuth thruster, improving the steering ability of many hullforms. This can also save energy since less thrust vectoring is needed to keep a steady course. Azipull thrusters are attractive not only for their efficiency but because their rudder effect can provide effective steering for hull forms which are in themselves not particularly stable.
The latest application field for Azipull thrusters is in passenger vessel propulsion, and the superyacht market is also beginning to show interest, said the company, noting that prosperous times have produced owners who want yachts from 50m (164ft) and up, for their own pleasure or for charter.
"There has been a tendency to concentrate on visual appearance, comfort and style, quite naturally, while below the waterline solutions remain very traditional," said Rolls-Royce. However, noted the company, particularly for faster displacement yachts with service speeds up to 24kt, Azipull-based propulsion systems can be effective.
The thrusters can be used in a variety of mechanical and diesel electric transmissions, giving freedom in positioning the machinery and opening the way for different accommodation layouts. Where a yacht makes long voyages and then requires good manoeuvring capabilities, Azipull thrusters can provide an ideal solution.
The cost aspect of reduced fuel consumption may not be as important in the superyacht market as in some other markets, but lower emissions because of better propulsion efficiency are increasingly a factor, as are reduced noise and vibration.
(16 November 2006)
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