NL2004687C2

NL2004687C2 - Vessel.

Info

Publication number: NL2004687C2
Application number: NL2004687A
Authority: NL
Inventors: Baldo Aloysius Maria Dielen
Original assignee: Baldo Dielen Assessoria Ltda
Priority date: 2010-05-07
Filing date: 2010-05-07
Publication date: 2011-11-08
Also published as: ES2541009T3; DK2704946T3; HK1195891A1; CA2870686A1; EP2704946B1; WO2011139154A2; PT2704946E; WO2011139154A3; CY1116515T1; PL2704946T3; EP2704946A2

Description

P29956NL00/GEW/YGR

Vessel

The present invention relates to a vessel, especially a tug vessel, comprising a towing device and a hull, wherein the towing device comprises: a towline; a tow point where the vessel exerts a force, especially a horizontal force, onto the towline when applying a tensile force to an object by means of the towline, the tow point being provided on the vessel; and a first 5 propulsion system and a second propulsion system.

Such a vessel is known from NL-1,023,447. Figure 2 of NL-1,023,447 shows a tug vessel with a towing device. The towing device (30) is arranged in the mid section of the vessel and consists of a circular guiding ring (31, 32), a towline (22) and a towing hook (33) where the towline applies force onto the vessel when applying a tensile force to a towed 10 object by means of the towline. The towing hook (33) is mounted on the guiding ring (31, 32) and moveable along the guiding ring. As can be seen in figure 2d, the vessel has two propulsions systems in the form of conventional fixed screws. Both propulsion systems are arranged at the stern part of the vessel. According to NL-1,023,447 it is anticipated - see page 4 lines 31-34 - that these screw propulsions can be of the type having screw blades 15 adjustable with respect to the fixed screw shaft so that they are continuously adjustable from forward to backward propulsion. Further NL-1,023,447 mentions - see page 8 line 10-11 -that also other propulsion systems like Voith Schneider propulsions can be used.

When it is required to exert maximum force on a towed object both propulsions of the vessel of NL-1,023,447 are required and are - both - directed in a direction essentially 20 parallel to the length direction of the vessel so that the vessel has maximum stability against capsizing. In case both propulsions would be directed in a same direction essentially transverse to the vessel of NL-1,023,447, this automatically results in turning of the vessel around the towing point or centre of mass of the vessel so that this situation can not be maintained. When towing in transverse direction of the vessel, the propulsions of NL-25 1,023,447 will be directed in different directions so that one on the propulsions is actually pulling and the other is directed in opposite direction to prevent rotation of the vessel around the towing point/centre of mass of the vessel.

The present invention has as its object to improve the vessel according to the preamble of claim 1.

30 This object is according to the invention achieved by providing a vessel comprising a towing device and a hull, wherein the towing device comprises: • a towline; 2 • a tow point - such as a fairlead, a bitt, or a tow hook - where the vessel exerts a force, especially a horizontal force, onto the towline when applying a tensile force to an object by means of the towline, the tow point being provided on the vessel; • a first propulsion system and a second propulsion system; 5 characterized, in that the first propulsion system and second propulsion system each comprise an omni-directional propulsion device; and in that, viewed in longitudinal direction of the vessel,0 the tow point is arranged in between the first omni-directional propulsion device and the second omni-directional propulsion device.

It is to be noted, that the vessel according to the invention can be used for tugging -10 in which case the vessel is, viewed in transport direction of the towed object, ahead of the object - as well as for assisting in manoeuvring an object - in which case the vessel might, viewed in transport direction of the towed object, behind the towed object. Further, the term ‘omni-directional propulsion device’ is in the field of vessel propulsion a well defined term. This term stands for a propulsion device which can be adjusted for providing thrust in any 15 desired direction within a range of 360° around a central axis. Well known examples of such ‘omni-directional propulsion device’ are so called “Voith-Schneider” propulsion devices and so called “azimuthal” propulsion devices. The term tow point is well known from tug vessels.

It is the point where the vessel, when attached to a towed object and during towing, exerts onto the towline effectively the horizontal force which is about equal to the horizontal 20 component of the tensile force of the towline. It is noted that this does not mean that the towline (also called towing cable) extends horizontally. Although the towed/assisted object, which is in general a vessel (but in this application called an object), as well as the tug (in this application called a vessel) will obviously move in a horizontal plane, the towline is hardly ever horizontal, in particular when assisting vessels in port. Towline angles are then typically 25 20-45 degrees.

The configuration according to the invention has two omni-directional propulsion devices with in between the towing point and/or the centre of buoyancy of the vessel. This allows both omni-directional propulsion devices being used simultaneously for propulsion in the same direction irrespective of the position of the vessel with respect to the extension 30 direction of the towline. Consequently the maximum available propulsion power can also be used when the towline extends transverse to the length direction of the vessel. The two omni-directional propulsion devices being provided at opposed sides of the towing point and/or centre of buoyancy of the vessel, prevents the length axis of the vessel from rotating with respect to the towline. This improves the manoeuvrability of the vessel and improves the 35 ability of the vessel in assisting in manoeuvring an object as especially in this case the transverse orientation of the vessel with respect to the towline is advantageous. When the vessel is transverse to the towline and the object pulls the vessel as the vessel is, viewed in 3 transport direction of the towed object, behind the towed object, a transversely oriented vessel will experience a much larger resistance from the water than a vessel having its length direction in the same direction as the direction of extension of the towline.

According to a further embodiment of the invention, the first and second omni-5 directional propulsion device are provided in the vertical longitudinal sectional plane of the vessel. This means that the first and second omni-directional propulsion devices are each provided in or close to (which means within 10% of the width of the vessel) the vertical longitudinal sectional plane of the vessel. This arrangement allows for a slender hull with fine entrances at bow and stern. The slender hull will be more energy efficient, have better 10 seakeeping characteristics and can reach higher speeds than a wider hull.

According to a further embodiment of the invention, the tow point is provided in the vertical longitudinal sectional plane of the vessel. This means that the tow point is provided in or close to (which means within 20% of the width of the vessel) the vertical longitudinal sectional plane of the vessel. This arrangement allows the towline and towing winch being 15 stored in the centre of the vessel, which is advantageous with respect to the weight distribution of the vessel.

In order to improve the stability of the vessel and, as a result, to improve towage performance, the hull comprises, according to a further embodiment: a main hull; and a left and right side hull provided at the left respectively right longitudinal side of the main hull; 20 wherein the side hulls are arranged for providing additional buoyancy counteracting capsizing and/or wherein the side hulls are arranged to increase stability, and as a result also maximum towing forces, without requiring (substantial) increase of water displacement. Such side hulls can be of basically two types. The first type of side hull is the so called sponson type. A sponson is a bulge formed onto the main hull. With the sponson type, there is no gap 25 between the main hull and side hull through which water could flow. In case the side hulls are of the sponson type, the main hull and side hulls form so to say one integral hull. The second type of side hull is the so called outrigger type. An outrigger is sometimes also called an ‘ama’ (plural ‘amas’). In case of two side hulls of the outrigger type, this results in a kind of trimaran. An outrigger is a floating body carried by one or more carriers, like beams or other 30 structures, at a distance from the main hull so that, between the main hull and side hull a gap results through which water can flow. The advantage of applying a side hull of the outrigger type is that a high degree of stability can be obtained with a narrow main hull of low displacement (when compared with typical mono-hull type tugs of similar stability and towage performance). Furthermore, propulsion efficiency, indirect towage performance and course 35 stability are increased. The advantages of a side hull of the sponson type (when compared woth normal ‘monohuN’ tugs) are essentially the same as those of the outrigger type, although their effectiveness is less pronounced.

4

For improved stability against capsizing, the draught of the main hull is, according to a further embodiment of the invention, larger than the draught of the side hulls. According to a further elaboration of this embodiment, the draught of the side hulls is larger than zero, such as 5 to 10 % of the draught if the main hull.

5 In order to ensure that the side hulls become effective at relative small heeling of the vessel, the draught of the main hull is, according to a further embodiment of the invention, at least 25%, especially at least 50%, larger than the draught of the side hulls.

In order to provide, on the one hand, low water resistance when the vessel runs at cruising speed without towing an object and to provide, on the other hand, good stability 10 against capsizing when towing an object with a towline extending transversely to the vessel, the water displacement of the side hulls is according to a further embodiment, when the vessel is in horizontal condition, at most 20% of the total water displacement of the vessel, especially at most 15% of the total water displacement of the vessel, such as at most 12% or at most 10% of the total water displacement of the vessel. The term ‘horizontal condition of 15 the vessel’ means the condition in which the heeling is zero degrees.

In order to increase lateral resistance and towline forces of the vessel in transverse direction under influence of a towing load and to improve course stability of the vessel, the hull, especially the main hull, is according to a further embodiment of the invention, provided with at least one keel. According to a further elaboration of this embodiment of the invention, 20 the hull, especially the main hull, is provided with two keels which are mutually parallel. In order to avoid dry dock structures when the vessel is on shore, the two keels have, according to a further embodiment of the invention, a draught larger than or equal to the draught of the first and second omni-directional propulsion device and are arranged to support the vessel onto the keels when on shore. This arrangement allows placing the vessel directly on shore 25 without damaging the omni-directional propulsion devices.

According to a further embodiment of the invention, the first and second propulsion system are arranged to provide the vessel a continuous bollard pull of at least 300 kN (= 30 t BP), preferably at least 450 kN (= 45 t BP), such as at least 650 kN (= 651 BP).

According to a further embodiment of the invention, said continuous bollard pull is at 30 most 1500 kN (= 150 t BP).

Unlike in ground vehicles, the statement of installed horsepower is not sufficient to understand how strong a tug vessel is. This because other factors, like transmission losses, propulsion type, efficiency of the propulsion system, have an influence as well. Therefore, in the field of tug vessels bollard pull values (BP) are used. In general these values are stated 35 in tons. The bollard pull value represents the maximum pulling force that a vessel can exert on another vessel or object. The bollard pull values as used in this application are so called continuous bollard pull values (sometimes also called steady or sustained bollard pull 5 values). These are determined by practical trial in still water having a depth of at least 20 m. The vessel is connected by a cable to the fixed world, for example a bollard, and a load cell (dynamometer) provided in or on the cable measures the tensile force in the cable at maximum thrust of the vessel. The (continuous) bollard pull value is the tensile force which 5 can be measured during a period of 5 to 10 minutes after the initial peak value has disappeared. Various test procedures to determine bollard pull are in existence. For reference, the procedures as described by the major Classification Societies can be utilized ( Rules for Building and Classing Steel Vessels under 90 meters, American Bureau of Shipping, Part 5, Chapter 8, Appendix 2, Guidelines for Bollard Pull tests; or, Rules for Ships, 10 Det Norske Veritas, Part 5, Chapter 7, Section 2, Appendix A, Bollard Pull testing Procedure or Bollard Pull Certification Procedures, Lloyd’s Register of Shipping, Guidance Information).

According to a further embodiment of the invention, the first and second propulsion system are arranged for providing equal propulsion forces when operated at maximum power. Taking into account that according to the invention the first and second propulsion 15 system can, under all towing conditions, be operated to provide propulsion in the same direction, this means that the towing vessel can exert maximum pushing and pulling forces in all directions (i.e. 360 degrees in horizontal plane). For example, when pushing sideways against an object, full bollard pull force is available. While the fender contact area sideways is large, the chances of damage to the object are reduced when pushing sideways. Also, 20 when assisting objects ‘under way’ the propulsion forces can at all times be directed in the ideal direction, thereby maximizing towline forces and/or increasing fuel economy.

According to a further embodiment of the invention, the vessel comprises a further propulsion, which further propulsion has a maximum power of at most 30%, such as at most 20%, of the sum of the maximum power of the first propulsion system and second propulsion 25 system. In mathematical form this means: “Maximum power of further propulsion < 0.3 x (maximum power of first propulsion system + maximum power of second propulsion system)”.

For example, as envisaged by the inventor, the further propulsion can consist of a left and right propulsion unit, each having a maximum power of 170 kW, i.e. the further propulsion 30 has a maximum power of 2x170 kW. The first and second propulsion system can each have a power of 2000 kW, i.e. the sum of their maximum powers is 4000 kW. In this example the maximum power of the further propulsion thus is 8,5% of the sum of the maximum power of the first and second propulsion system.

This further propulsion is primarily intended for cruising operation (such as transits, 35 mobilizations) and standby without towing any object. This configuration allows the further propulsion being used during cruising whilst the first and second propulsion system, which are primarily intended for towing operation of the vessel, can be turned off. Realizing that the 6 first and second propulsion system are primarily designed for towing operation and that their propulsion power is for cruising operation far oversized, it will be clear that the energy efficiency of the first and second propulsion system will be very low (inefficient) with respect to a further propulsion which is primarily designed for cruising operation. This configuration 5 thus allows very efficient usage of fuels. According to a further elaboration of this embodiment, the further propulsion is arranged for driving a generator and/or for driving one or more towing winches directly or indirectly via for example a generator generating electric power for operating said winch and optionally providing electric power for other systems as well.

10 According to a further embodiment of the invention, the further propulsion comprises 2 propulsion elements, which are both provided at the same distance from the stern of the vessel and at opposing sides of the vertical longitudinal sectional plane of the vessel. This allows arrangement of the further propulsion system without hindering the first and second propulsion systems in their operation, allows for easy manoeuvring of the vessel and ensures 15 good water flow to the propulsion elements.

Vessel according to one of the preceding clauses, wherein the vessel is provided with a so called articulated barge coupling system. So called articulated barge couplings are known from the prior art, also in relation to vessels. Such couplings are intended for coupling a vessel to a barge which is to be manipulated by the vessel.

20 According to a further embodiment of the invention, the towline extends from the tow point to the object to which the towline is attached. According to a further aspect of the invention, the invention also relates to an assembly of a vessel according to the invention and an object, the towline extends from the tow point to the object to which the towline is attached.

25 According to a further embodiment of the invention, the tow point is, measured from the stern of the vessel, provided at a distance of 20% to 50 % of the length of the vessel, preferably at a distance of 30% to 50% of the length of the vessel, more preferably at a distance of about 40% to 45% of the length of the vessel. This means that the tow point is arranged close to the rotating point of the underwater body of the vessel. This allows easy 30 positioning of the vessel with respect to the towline.

According to the invention, the tow point can be formed by a bitt or a tow hook, which both actually attach the towline to the vessel at the location of the tow point.

According to a further embodiment of the invention, the towing device further comprises a fairlead for guiding the towline, wherein the fairlead forms the tow point. This 35 allows the towline to be attached to the vessel in another more practical location.

According to another further embodiment of the invention, the towing device further comprises: a towing winch mounted on the vessel for winding and unwinding the towline; and 7 a fairlead for guiding the towline towards the towing winch. Here the fairlead provides guidance for the towline in order to ensure it is properly received on the winch. The winch allows the length of the tow part of the towline to be adjusted depending from circumstances.

According to a further embodiment of the invention, the towing winch is provided at 5 the vertical longitudinal sectional plane of the vessel. This provides a symmetric weight distribution over the vessel.

According to a further embodiment of the invention, the towing winch is, measured from the stern of the vessel, provided at a distance of 20% to 60 % of the length of the vessel, preferably provided at a distance of 30% to 60 % of the length of the vessel, more 10 preferably at a distance of about 40% to 50% of the length of the vessel. This provides a symmetric weight distribution over the vessel.

According to a further embodiment of the invention, the vessel is a tug vessel.

According to a further embodiment of the invention, the towing device further comprises a, guiding arc mounted on the vessel, wherein, viewed in vertical direction, the 15 guiding arc is provided above the deck and wherein the guiding arc extends along the deck, which guiding arc is arranged for guiding the towline along the deck while swinging the vessel with respect to the towline while applying a tensile force to an object. This guiding arc allows the towline to swivel with respect to the vessel. Although this guiding arc can be in accordance with known prior art like disclosed in NL-1,023,447, it is according to this 20 invention preferred to arrange this guiding arc in accordance with the non-published earlier NL-application NL-2003746, titled ‘vessel’ and filed on November 3, 2009 in the name of ‘Baldo Dielen Assessoria LTDA’, Brasil. All teaching of the guiding arc in NL-2003746 is hereby incorporated by reference.

25 Below, the invention will be further explained with reference to the drawings. These drawings are all of schematic nature. In these drawings:

Figure 1 shows a first embodiment of the invention in a perspective view;

Figure 2 shows a second embodiment of the invention in a perspective view from above; 30 Figure 3 shows the second embodiment of figure 2 in a perspective view from below;

Figure 4 shows the second embodiment of figures 2 and 3 in a bottom view;

Figure 5 shows a third embodiment of the invention in a bottom view;

Figure 6 shows a fourth embodiment of the invention in a bottom view;

Figure 7 shows a fifth embodiment of the invention in a perspective view from below; 35 Figure 8 shows the fifth embodiment of figure 7 in a perspective view from above, when used for pushing or pulling a barge;

Figure 9 shows a side view of figure 8; 8

Figure 10 shows a schematic diagram of the effective pulling force of various types of vessels;

Figure 11 shows schematically the forces during indirect towing of a prior art vessel (Fig. 11 A) and of a vessel according to the invention (Fig. 11B); and 5 Figure 12 shows schematically a prior art vessel (Fig. 12A) and a vessel according to the invention (Fig. 12B) during assisting a vessel object in a channel.

In the description below, different embodiments of the vessel are indicated by different reference numbers, but same or similar parts of these embodiments are indicated 10 with the same reference number or sign.

Figure 1 shows a first embodiment 10 of the vessel according to the invention. The vessel 10 comprises a main hull 61 (without side hulls as are present in the other embodiments). The main hull 61 has a length direction L and a transverse direction T (see figure 2) extending horizontally, transverse to the longitudinal direction. On the deck 84 there 15 is indicated an imaginary longitudinally deck centre line 81 extending in longitudinal direction and defining the longitudinally centre of the deck. The so called ‘vertical longitudinal sectional plane’ of the vessel is defined by the longitudinally deck centre line 81 and a vertical through the longitudinally deck centre line 81.

The vessel 10 further comprises two omni-directional propulsion devices 71 and 72, 20 which in all shown embodiments 10, 20, 30, 40, 50 are a so called azimuthal propulsion device. It is however noted that in all embodiments of the invention, the omni-directional propulsion device can also be of a different type, like a Voith-Schneider propulsion device. A characteristic of a omni-directional propulsion device is that the direction of the thrusting force generated by the omni-directional propulsion device can be adjusted to be directed in 25 any desired direction essentially perpendicular to the vertical axis 85 as indicated in figure 1, i.e. the propulsion direction can be rotated (as indicated with arrow R in figure 4) around a vertical axis 85. In case of a azimuthal propulsion device, the thrusting propeller (which rotates around a horizontal axis for thrusting action) is actually rotated around the vertical axis 85. As will be realized, it is for the invention not required that the vertical axis 85 extends 30 exactly vertical.

The vessel according to the invention further has a so called towing point 65 defining the position where the towline 64 acts in horizontal direction on the vessel. According to the invention, this towing point 65 is positioned, viewed in longitudinal direction of the vessel 10, in between the first omni-directional propulsion device 71 (further called ODPD) and the 35 second ODPD 72. As follows from figure 1, it is not required that the towing point 65 is arranged at the same vertical height as the ODPDs 71 and 72. In general the towing point 65 will, viewed in vertical direction, be arranged higher than the ODPDs 71,72. Although it is 9 preferred that both the ODPDs 71,72 as well as the towing point are arranged in the vertical longitudinal sectional plane (as shown in all figures), it is not required that these are all arranged in the vertical longitudinal sectional plane, neither is it required that these are arranged in one plane parallel to the vertical longitudinal sectional plane. It is for example 5 very well conceivable that the towing point as arranged at a side of the main hull, whilst the ODPDs 71 and 72 are arranged in or around the vertical longitudinal sectional plane.

Figures 2-4 show a second embodiment 20 of the vessel according to the invention. The main differences between the vessel 20 and 10 are the following: • on deck 84 of the main hull 61 there is provided a guiding arc 69 for guiding the towline 10 64 so that it can rotate around the tow point 65. For details and advantages of this guiding arc 69, reference is made to the earlier mentioned NL-2003746 of applicant, which is fully incorporated into this application by reference. As will be understood, this guiding arc 69 can also be applied with the embodiment 10 of figure 1. Further, it is to be noted that it is also conceivable to leave this guiding arc away from the embodiment 20 15 as well as from the embodiments 30, 40, 50 (to be discussed below); • The vessel 20 provided with two side hulls 62 in the form of so called outriggers 62. These outriggers 62 are carried by transverse carriers 75 (see figure 4) so that there is a gap 86 between the main hull 61 and side hulls 62. When in water, water can pass through this gap 86. Above water level, the gap might be closed, for example by the 20 carrier.

• The vessel 20 is provided with two keels 66 on the main hull 61. As will be clear also embodiment 10 could be provided with two keel (or one keel arranged centrally, like in embodiment 30 and 40, to e discussed below). Further it will be clear that also more keels as well as one keel or no keel are conceivable with the embodiment 20 (as well as 25 with the other embodiments 30, 40, 50 to be discussed below).

• The vessel 20 is provided with a further propulsion 73 consisting of two propulsion elements 74, each provided on one side of the vessel. These serve for thrusting the vessel during transit (i.e. when no load is towed). As will e clear also embodiment 10 can e provided with such an additional propulsion. Further it will be clear that the additional 30 propulsion 73, 74 can also be left away from the embodiment 20 as well as the other embodiments 30, 40 and 50 (discussed below).

In figure 2, reference number 82 indicates the water line of the main hull 61 and reference number 83 indicates the water line of the side hull 62. It can be seen that the draught D1 of the main hull is larger than the draught D2 of the side hull 62. In this 35 embodiment the draught D1 is about 150% of the draught D2, i.e. 1.5 times larger. Further it can be seen that the draught D4 of the keels 66 is larger than the draught D3 of the ODPDs 10 71, 72, so that when on shore the vessel 20 can stand on the keels 66 without damaging the ODPDs 71, 72.

Figure 5 shows a third embodiment 30 of the vessel according to the invention. The main differences between the vessel 30 and vessel 20 is that vessel 30 has only one central 5 keel 66 whilst vessel 20 has two keels 66 spaced apart. As will e clear, the vessel 30 can in addition be provided with two keels 66 spaced apart, like shown in figures 2-4. Further all remarks made in relation to vessel 10 concerning leaving away parts of the vessel, apply to the third embodiment 30 as well.

Figure 6 shows a fourth embodiment 40 of the vessel according to the invention. The 10 main differences between the vessel 40 and vessel 30 is that vessel 40 has side hulls in the form of so called sponsons 63, whilst vessel 30 has side hulls in the form of so called outriggers 62. Each sponson 63 is formed onto and against a side of main hull 61 so that there no gap between the sponson 63 and main hull 61. As will be clear, the remarks concerning leaving away of the vessel 20 or vessel 30 (as well as concerning adding parts to 15 said vessels 20, 30) apply to vessel 40 as well.

Figure 7 shows a fifth embodiment 50 of the vessel according to the invention. The main differences between the vessel 50 and vessel 40 is that vessel 50 has two keels whilst vessel 40 has one keel. As will be clear, the remarks concerning leaving away parts of the vessel 20 or vessel 30 or vessel 40 (as well as concerning adding parts to said vessels 20, 20 30, 49) apply to vessel 50 as well.

Figures 8 and 9 show an assembly of, one the one hand, a vessel 50 provided with a so called articulated barge coupling system and, on the other hand, a barge 70. As will be clear the vessel 50 can be replaced by any other vessel 10, 20, 30 or 40.

Figures 10-12 give an impression of the advantages of the vessel according to the 25 invention over prior art tug vessels.

Figure 10 shows a schematic diagram of the effective pulling force of various types of vessels. Reference number 90 indicates schematically the positioning of the vessel; graph 91a indicates the effective pulling force of a Voith-Schneider tug having two Voith-Schneider devices arranged in the stern part of the vessel (like the configuration of the vessel 100 30 shown in figures 11A and 12A); graph 91 b indicates the effective pulling force of an ASD tug (ASD=Azimuthal Stern Drive) as indicated with 100 in figures 11A and 12A; graph 91c indicates the effective pulling force of a so called tractor tug; and graph 92 indicates the effective pulling force of a vessel according to the invention.

In the diagram of figure 10, it is assumed that all vessels have the same installed 35 power of 100 ppu (=propulsion power unit). Taking into account Voith-Schneider devices have a lower efficiency, the graph 91a for a Voith-Schneider tug shows considerable lower values (a maximum of 75 ppu against a maximum of about 100 ppu for the others).

11

Assuming the vessel is, in figure 10, oriented with its back (stern) facing to the left, its front facing to the right, its left side (port side) facing upwards and its right side (starboard side) facing downwards, the towline is rotated over 360° around the vertical through the tow point and the bollard pull force is determined for each rotation angle. As one can see from graph 5 92, the bollard pull force of a vessel according to the invention is about 100 in all directions (circular graph 92). However, the bollard pull force for the prior art vessels decreases very considerable when the towline is rotated from a direction parallel to the length direction of the vessel towards a direction perpendicular to the length direction of the vessel, see the about perpendicular/oval graphs 91a, 91b and 91c. The advantages of the vessel according to the 10 invention over the prior art vessels, are evident and speak for them selves.

Figure 11 shows schematically the forces during indirect towing of a prior art vessel (Fig. 11 A) and of a vessel according to the invention (Fig. 11B). Indirect towing means that, viewed in the direction X in which the towed vessel object 60 moves, the towing vessel 100 (an ASD tug according to the prior art) or 50 (according to the invention) is behind the towed 15 vessel object 60 in order to keep the towed vessel object 60 in its course by exerting pulling forces on the stern of the towed vessel object 60. The prior art towing vessel 100 and invented towing vessel 50 are compared under similar circumstances. The angle 3 between the length direction of the towing vessel 50,100 and the direction of movement X of the towed vessel object 60 is in both cases the same. Further the angle y between the towline 20 and the line perpendicular to the length direction of the towed vessel object 60 is in both cases the same. Also the maximum bollard pull force of the towing vessels 50,100 is the same (for the ASD tug 100 this maximum bollard pull force is in the length direction of the ASD tug 100), i.e. both towing vessels 50,100 have comparable power. As follows clearly from comparison of figures 11A and 11B, the invented towing vessel can exert a 25 considerable larger towing force FT on the towline than the prior art ASD tug. This appears to be due to the fact that the thrusting forces P1 and P2 of the MDPDs 71 and 72 of the invented towing vessel are directed essentially transverse to the direction X of movement of the towed vessel object 60, whilst the thrusting forces P1 and P2 of the MDPDs 171 and 172 of the ASD tug 100 are directed essentially in the direction X of movement of the towed 30 vessel object 60. The advantages of the vessel according to the invention over the prior art vessels, are evident and speak for them selves.

Figure 12 shows schematically a prior art vessel (Fig. 12A) and a vessel according to the invention (Fig. 12B) during assisting a vessel object in a channel. As follows clearly from comparison of figures 12A and 12B, the invented towing vessel 50 requires in case of towing 35 action in transverse directions much less space than a prior art ASD tug 100. This means that the invented towing vessel 50 can assist a towed vessel object through much smaller 12 channels (the bank of which is indicated with 101) than a prior art ASD tug vessel 100. Evidently this is also advantageous in crowded waters.

Although a vessel 50 is shown in figures 11B and 12B, it will be clear that this vessel 50 can be replaced by any other embodiment of a vessel according to the invention, like a 5 vessel 10, 20, 30 or 40.

It is to be noted that within the scope of the claims, many variants of the invention are conceivable. For example: the first propulsion system can according to the invention also comprise two (or more) of said first omni-directional propulsion devices, which in case of two of said first omni-directional propulsion devices could according to the invention be arranged 10 symmetrically with respect to the vertical longitudinal sectional plane of the vessel; and/or the second propulsion system can according to the invention also comprise two (or more) of said second omni-directional propulsion devices, which in case of two of said second omnidirectional propulsion devices could according to the invention be arranged symmetrically with respect to the vertical longitudinal sectional plane of the vessel.

15

List of used reference numbers/siqns 10 vessel 20 vessel 20 30 vessel 40 vessel 50 vessel 60 object 61 main hull 25 62 side hull of outrigger type/outrigger 63 side hull of sponson type/sponson 64 towline 65 tow point 66 keel 30 67 stern 68 articulated barge coupling system 69 guiding arc 70 barge 71 first propulsion system/first omni-directional propulsion device (the aft 35 unit) 72 second propulsion system/ second omni-directional propulsion device (the forward unit) 13 73 further propulsion 74 propulsion element 75 transverse carrier 81 longitudinal deck centre line 5 82 water line of main hull 83 water line of side hull 84 deck 85 vertical rotation axis of omni-directional propulsion device 86 gap 10 90 schematic representation of a tug vessel 91 a-c effective pulling force of prior art vessels 92 effective pulling force of vessel according to the invention 100 prior art vessel 171 (first) propulsion system of prior art vessel 15 172 (second) propulsion system of prior art vessel D1 draught of main hull D2 draught of side hull D3 draught of first/second propulsion device 20 D4 draught of keel L longitudinal direction of vessel P1 thrust direction of first propulsion device P2 thrust direction of second propulsion device R rotation of omni-directional propulsion device 25 T transverse direction of vessel X direction of movement of towed object

Claims

Vessel (10, 20, 30, 40, 50) comprising a towing device and a hull (61,62, 63), the towing device comprising: • a towing wire (64); • a towing point (65) provided on the vessel where the vessel (10, 20, 30, 40, 50), when exerting a pulling force on an object (60) by means of the towing wire (64), force (, in the particularly horizontal force) on the drag wire (64); A first propulsion system (71) and a second propulsion system (72); characterized in that the first propulsion system and second propulsion system each comprise an omni-directional propulsion device (71,72); and that, viewed in the longitudinal direction of the vessel, the towing point (65) is located between the first omni-directional propulsion device (71) and second omni-directional propulsion device (72). 15

The vessel (10, 20, 30, 40, 50) of claim 1, wherein the first and second omni-directional propulsion device (71, 72) are provided in the vertical longitudinal longitudinal plane of the vessel.

Vessel (10, 20, 30, 40, 50) according to any one of the preceding claims, wherein the towing point (65) is provided in the vertical longitudinal longitudinal plane of the vessel.

4. Vessel (10, 20, 30, 40, 50) as claimed in any of the foregoing claims, wherein each omni-directional propulsion device (71,72) comprises a propulsion device selected from the group: a Voith-Schneider propulsion device or an azimuthal propulsion device.

Vessel (10, 20, 30, 40, 50) according to any one of the preceding claims, wherein the hull comprises: • a main hull (61); and 30. a left and a right side hull (62, 63) provided on the left and right longitudinal sides of the main hull (61), respectively.

The vessel (10, 20, 30, 40, 50) of claim 5, wherein the draft (D1) of the main hull (61) is greater than the draft (D2) of the side hulls (62, 63).

Vessel (10, 20, 30, 40, 50) according to claim 6, wherein the draft (D1) of the main hull (61) is at least 25%, in particular at least 50%, greater than the draft (D2) of the side hulls (62, 63). 5

Vessel (10, 20, 30, 40, 50) as claimed in any of the claims 5-7, wherein, in the horizontal position of the vessel, the water displacement of the side hulls (62, 63) is at most 20% of the total water displacement of the vessel (10, 20, 30, 40, 50) is, in particular, at most 15% of the total water displacement of the vessel, such as at most 12% of the total water displacement of the vessel. 10

Vessel (40, 50) according to any of claims 5-8, wherein each side hull comprises a sponson (63) formed on the main hull (61).

Vessel (20, 30) according to any of claims 5-8, wherein each side hull comprises an outrigger (62) attached to the main hull (61) by one or more cross-members (75).

11. A vessel according to any one of the preceding claims, wherein the hull (61) is provided with at least one keel (66). 20

The vessel (20, 50) of claim 11, wherein the hull (61) is provided with two parallel keels (66).

13. Vessel (20, 50) according to claim 12, wherein the keels (66) have a draft (D4) greater than or equal to the draft (D3) of the first and second omni-directional propulsion device (71, 72) and are arranged to be able to land the vessel on shore.

14. Vessel (10, 20, 30, 40, 50) as claimed in any of the foregoing claims, wherein the first and second propulsion system (71, 72) are adapted to provide the vessel with a continuous pole pull (continuous bollard pull) of at least 300 kN (≤ 30 t BP), preferably at least 450 kN (= 451 BP), such as at least 650 kN (= 651 BP).

Vessel (10, 20, 30, 40, 50) according to claim 14, wherein said continuous bollard pull is at most 1500 kN (= 1501 BP). 35

Vessel (10, 20, 30, 40, 50) as claimed in any of the foregoing claims, wherein the first and second propulsion system are adapted to provide substantially equal propulsive forces. 5

Vessel (10, 20, 30, 40, 50) according to any one of the preceding claims, wherein the vessel comprises a further propulsion (73), which further propulsion (73) has a maximum power of no more than 30%, such as not more than 20% of the sum of the maximum power of the first propulsion system (71) and the second propulsion system (72). 10

Vessel (10, 20, 30, 40, 50) according to claim 17, wherein the further propulsion (73) comprises two propulsion elements which are provided at, for each, an equal distance from the rear of the vessel and on either side of the vertical median longitudinal plane of the vessel. 15

Vessel (50) according to one of the preceding claims, wherein the vessel is provided with an articulated barge coupling system.

Vessel (10, 20, 30, 40, 50) according to claim one of the preceding claims, wherein the towing wire (64) extends from the towing point (65) to the object (60) to which the towing wire (64) is attached .

A vessel (10, 20, 30, 40, 50) according to any one of the preceding claims, wherein the towing point (65) is located at a distance of 20% to 50% of the length measured from the rear of the vessel of the vessel, preferably at a distance of 30% to 50% of the length of the vessel, more preferably at a distance of about 40% to 45% of the length of the vessel.

Vessel (10, 20, 30, 40, 50) as claimed in any of the foregoing claims, wherein the towing device further comprises a wire guide for guiding the towing wire, and wherein the wire guide forms the towing point (65).

A vessel (10, 20, 30, 40, 50) according to any one of the preceding claims, wherein the towing device further comprises: 35. a towing winch mounted on the vessel for winding and unwinding the towing wire; and • a wire guide for guiding the tow wire to the tow winch.

The vessel (10, 20, 30, 40, 50) of claim 23, wherein the tow winch is provided in the vertical center longitudinal plane of the vessel.

Vessel (10, 20, 30, 40, 50) according to one of the claims, wherein the towing winch is placed on, measured from the rear (67) of the vessel, a distance of 20% to 60% of the length of the vessel, preferably at a distance of 30% to 60% of the length of the vessel, more preferably at a distance of about 40% to 50% of the length of the vessel. 10

Vessel (10, 20, 30, 40, 50) according to one of the preceding claims, wherein the vessel is a tugboat.

27. A vessel (10, 20, 30, 40, 50) as claimed in any of the foregoing claims, wherein the towing device further comprises a guide bow (69) mounted on the vessel, viewed in vertical direction, extending along the vessel, extending along the deck (84) and which is adapted to guide the towing wire (64) along the deck (84) when, during towing, the vessel is pivoted relative to the towing wire.