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May 2005

Article selected from our quarterly magazine dedicated to the largest and most luxurious boats with information, interviews, technical articles, images and yachting news



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Article by
Angelo Colombo


The propulsion systems in nautical field has been always object of studying and testing, resulting time after time in new advanced and efficient projects and elements in order to determine the lift force. Indeed, among the various reachable tasks due to even more efficient systems there is a meaningful improvement in performance.

A conventional system assisted by shaft transmission and immersed props, may offer high performances though limits due to physical laws which can be overcome only with the help of other different systems like surface drives. The first surface propeller system has been put on the market by "Arneson Drive", so - called from the name of its inventor Howard Arneson, who first developed it as hobby after three years of projecting and testing.

Since about 1980 this propulsion system has been step by step up dated up to today's end configuration. In 1992 one of the most important international firms involved in developing and manufacturing propulsion systems, the "Twin Disc", thought it right to acquire royalties in order to produce Arneson drives and put them on the market. Today this company manufactures 18 models divided into two different versions able to be adapted to a large number of crafts and engines thanks to their features while ensuring always very high performances.

One of the most important secrets of this prop system consists in reducing the cavitation effect brought about by immersed props and resulting in better hydrodynamic efficiency, in noiselessness, in less damage to the props and less vibrations. Another important feature is its trimming and manoeuvring ability due to its propulsive elements being always able to perform high level manoeuvring even in rough seas.

The tacking effect achieved by surface drives is nearly double by comparison with that obtained from the effect of a rudder blade abaft an immersed prop. Most people think this system does not like manoeuvres at low speed and on a short sea, but it is sufficient to consider that is possible to trim the drives up to using them as immersed props to understand that to make used to this system.

The "Twin Disc" new systems ensure all the features having made the surface drives world - widely famous for their performances; at the same time they do not need extra - maintenance as well as they are suitable to work hard since they consist of few parts. Much shipyards have entrusted the best performing propulsion of their vessels to the Twin Disc surface drives; Pershing, Tecnomar, Maltese for its Magnum yachts, "Baia" and "Pisa" yards stand out among them.

For further information please contact: Twin Disc Inc.; U.S.A - 53404, Racine - Wisconsin; phone number: +1 262 638 4000; fax: +1 262 638 4482; web site: