About Twin Disc Water Jets

On February 96, Twin Disc Incorporated signed a licensing agreement with Doen Marine PTY Ltd of Melbourne AUSTRALIA to manufacture and market Doen’s line of water jets.

Doen Marine of Australia are among the pioneers of water jet propulsion. For more than 25 years they have been designing and manufacturing water jet units for use throughout the world.

The current product range is comprised of more than fifteen model sizes and caters for engines from 30 Hp up to 2000Hp marine diesels.

Thanks to the agreement Doen Jets will be manufactured by Twin Disc and distributed throughout its extensive worldwide distribution network..

Head office for European Middle Eastern and African markets has been established in Capezzano Pianore(LU) Italy.

Please send all the inquires concerning water jet propulsion systems to the following address:

TWIN DISC srl
MARINE PROPULSION DIVISION
Zona Industriale Le Bocchette, 92
55040 Capezzano Pianore(LU) Italy
Phone +39 0584 969696
Fax +39 0584 969692
E-mail : info@twindiscpropulsion.com

WATER JET PROPULSION SYSTEMS

Written reference is made to water jet propulsion as far back as the 17Th Century. In fact in this period there are two patents granted that suggest the use of a jet of water to propel ships.

The theory of water jet propulsion was subsequently investigated and discussed by Frenchman Daniel Bernoulli in 1753. Bernoulli suggested that a stream of water could be used to propel a boat and conducted some experimentation to confirm the principle of water jet propulsion.

While the theory may have existed we did not see practical examples until the mid twentieth century when there was the technology and sufficient understanding of the system.

A water jet system works in the same way that rockets, jet airplanes do. It is Newton’s third law, “for every action there is an equal and opposite re-action”, that simply explain the phenomenon. A jet of water is expelled from the rear of the boat. The reaction of this action is to propel the boat forward.

The water jet itself (the propulsor) is essentially a water pump. This pump is consequently mounted into the vessel with an intake opening flush with the hull bottom ad a discharge nozzle exiting through the transom (back) of the hull. The pump is driven by conventional petro or diesel engines with some very large horsepower water jets even using gas turbine.

Some misunderstandings that people commonly have is that the exit jet must strike the water or that the thrust will be greater if the water jet strikes the water. This is most definitely not the case and the essel would be propelled even if the water jet exited into the air.

Water jet systems are generally regarded as non conventional, used in high speed application (+25 Knots), but the fact of the matter is that, if correctly selected and installed, they can and do provide a visible alternative to the conventional propeller and can achieve overall efficiencies that are better than conventional propellers.