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Tug boat having an inclined shaft Disclosure Number: IPCOM000240973D
Publication Date: 2015-Mar-16
Document File: 5 page(s) / 233K

Publishing Venue

The Prior Art Database

Related People

Lauri Tiainen: INVENTOR


It is proposed that the shaft of the tugboat's propulsion unit (such as azimuthing propulsion unit) has an inclined shaft. In this way the thrust can be oriented under the ship to be assisted. Another advantage is that the wake resistance of the tugboat hull can be reduced.

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A tugboat is a boat that maneuvers vessels by towing or pushing them in a crowded harbour or a narrow canal, for instance. Typically tug boats are equipped with mechanical azimuth thrusters, but other propulsion arrangements are also common.

Current tug boat designs, and propulsion arrangements, are suboptimal in view of towing efficiency.


In the following, reference is made to accompanying drawings, where

Figure 1 shows a current art tug boat arrangement;

Figure 2 shows another current tug boat arrangement; and

Figure 3 shows an embodiment of a tug boat arrangement according to the improvement.

Detailed description

The embodiments relate to a towing tugboat arrangement. The tugboat arrangement comprises a tug hull and a propulsion unit fixedly arranged to the tug hull. The propulsion unit may be an azimuthing propulsion unit, for instance, which can be operated in a plurality of rotary orientations. In some embodiments, the azimuthing propulsion unit may be rotated 360 degrees thus enabling pulling and pushing operation modes of the propulsion unit. In the embodiments, the propulsion unit is arranged substantially to the rear of the tug, close to the transom of the boat. However, the propulsion unit can equally well be at the fore of the tug.

Figure 1 illustrates typical tugboat 100 arrangement. The tugboat comprises a tug hull 102 and a propulsion unit 110 fixed to the hull for providing thrust power for the tug. There is also shown a vessel 120 to be towed by the tugboat 100. The tugboat may be connected to the vessel by one or more pulling wires for delivering the pulling force of the tugboat to the vessel.

In Figure 1, the propulsion unit is arranged such that the thrust 122 effected by the propeller 112 of the propulsion unit 110 is directed upwards thus hitting the ship 120 to be assisted. A great deal of the pulling force is thus lost as the thrust from the propulsion unit tends to hinder the travel of the ship to be pulled. The loss of thrust may be even more than 50 % depending the distance between the tug 100 and the assisted ship 120.

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Figure 2 shows another disadvantage associated with the current solution of Figure 1. Typically with high power, the tug boat will have huge wake resistance at the stern of the tug. This wake will push the ship stern down and increase the resistance even more. The thrust direction when being as shown in Figure 1 makes the situation even worse.

Figure 3 shows an embodiment of a tug boat 300 according to the improvement. There is also shown a wire/rope 324 fixed to the tug and a ship 320 to be assisted.

The tug boat 300 comprises a propulsion unit 310. The propulsion unit may be an azimuthing propulsion unit or a mechanical thruster, for instance. In the case of the azimuthing propulsion unit, there is provided a strut 314 that is arr...