NL2003746C2

NL2003746C2 - VESSEL.

Info

Publication number: NL2003746C2
Application number: NL2003746A
Authority: NL
Inventors: Baldo Aloysius Maria Dielen
Original assignee: Baldo Dielen Assessoria Ltda
Priority date: 2009-11-03
Filing date: 2009-11-03
Publication date: 2011-05-04

Description

P29967NL00/YGR Title: Vessel

The present invention relates to a vessel, especially as a tug vessel, comprising a deck and a towing device, wherein the towing device comprises: a towing cable; a tow point where the towing cable applies force onto the vessel when applying a tensile force to an object by means of the towing cable, the towing point being provided on the vessel; and a 5 guiding arc mounted on the vessel above the deck, wherein the guiding arc extends along the deck. The towing cable has a tow part, which is defined as that part of the towing cable which extends from the tow point to the object when applying a tensile force to the object by means of the towing cable.

Such a vessel is known from NL-1,023,447. Figure 2 of NL-1,023,447 shows a tug 10 vessel with a towing device. The towing device (30) consists of a circular guiding ring (31,32), a towing cable (22) and a towing hook (33) where the towing cable applies force onto the vessel when applying a tensile force to a towed object by means of the towing cable. The towing hook (33) is mounted on the guiding ring (31,32) and moveable along the guiding ring. When during towing the position of the longitudinal direction of the vessel with 15 respect to the direction of the towing cable is changed, the towing hook, i.e. the point where the vessel applies towing force to the towing cable - can be displaced along the guiding ring. In case the towing cable extends transverse to the longitudinal direction of the vessel, this allows to prevent heeling of the vessel by moving the towing hook to that side of the vessel facing the towed object. Disadvantage of this construction is that due to the large 20 towing forces the guiding ring and moveable towing hook are susceptible to wear which results in malfunctioning. Due to the large towing forces, the guiding ring and towing hook must be designed very robust/solid in order to be able to withstand the large forces. The same applies for the vessel which must support the guiding ring. The weight of the vessel thus increases and the construction becomes complex. Further, when a winch is provided 25 the rail will be of much heavier construction as the winch is heavy. A winch provided on the guiding ring thus makes all these disadvantages even more disadvantageous.

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

[claim 1] This object is according to the invention achieved by providing a vessel 30 according to claim 1, i.e. a vessel, such as a tug vessel, comprising a deck and a towing device, wherein the towing device comprises: • a towing cable; -2- • a tow point - such as a fairlead, a bitt, or a tow hook - where the towing cable exerts horizontal force onto the vessel when applying a tensile force to an object by means of the towing cable, the towing point being provided on the vessel; • a guiding arc mounted on the vessel above the deck, wherein the guiding arc 5 extends along the deck; wherein the towing cable has a tow part, which is defined as that part of the towing cable which extends from the tow point to the object when applying a tensile force to the object by means of the towing cable; wherein the tow point is provided at the vertical longitudinal sectional plane of the vessel and 10 defines a vertical swivel axis for the tow part of the towing cable; wherein, viewed in a direction parallel to the deck, the guiding arc is arranged at a distance from the tow point - which distance is preferably larger than 1 m, more preferably larger than 2 m-; and wherein the guiding arc is arranged for guiding the tow part of the towing cable along the 15 deck while swinging the tow part of the towing cable around the swivel axis and for being subjected to an upward force applied by the tow part of the towing cable to the guiding arc while applying a tensile force to an object.

According to the invention the guiding arc extends above and along the deck. The guiding arc thus can extend parallel to the deck as well as under an angle of say up to 20° -20 30°, or more.

According to the invention, the tow point defines a vertical swivel axis for the tow part of the towing cable, i.e. the tow part - which in towing operation extends from the tow point up to the towed object - can swing around this swivel axis when the relative position of the longitudinal axis of the vessel with respect to the length direction of the towing cable 25 changes. According to the invention, this tow point is provided at the vertical longitudinal sectional plane of the vessel, i.e. 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. With respect to the tow point, it is noted that this is the point where the towing cable exerts a horizontal force on the vessel during towing.

30 As the towing cable is, in upward direction, supported - i.e. prevented from moving in upward direction - by the guiding arc at a distance from the tow point, the guiding arc will be subjected to an upward force applied by the tow part of the towing cable when a tensile force is applied to an object. This upward force will counteract heeling of the vessel towards the object. On the contrary, this upward force will cause raising of the side of the vessel 35 facing the object - called raising effect -.

Further advantages of the guiding arc supporting the towing cable according to the invention are amongst others the following: the so called tow line forces are effectively -3- increased, there are no parts moving along the guiding arc which might become jammed, the construction is lighter, large winches can be used. A final important advantage is that due to the vertical swivel axis of the towing cable being arranged at the tow point, the towing cable can instantaneously follow each movement of the towing cable with respect to the 5 vessel.

[claim 2] According to a further embodiment of the invention the guiding arc is essentially symmetrically with respect to the vertical longitudinal sectional plane of the vessel. This provides that the raising effect is independent from which longitudinal side of the vessel faces the object.

10 [claim 3] According another further embodiment of the invention, the guiding arc has lower side, which lower side faces the deck and forms a guiding surface for sideways displacement of the tow part of the towing cable when the tow part of the towing cable swings around the swivel axis. This provides an elegant, simple and reliable construction. An intermediate support attaching the tow part of the towing cable to the guiding arc is not 15 required. The tow part will so to say by itself find support against the lower side of the guiding arc when the towing cable exerts a tensile force to the object.

[claim 4] According to another further embodiment of the invention, the guiding surface extends uninterrupted along the entire guiding arc. This ensures that the tow part of the towing cable can move uninterrupted along the entire guiding arc.

20 [claim 5] According to a further embodiment of the invention, the distance between the tow point and the guiding arc is at least 1m, preferably at least 3 m, such as at least 6 m. With such a distance the upward force effects a raising moment sufficient to prevent heeling of the vessel reliably.

[claim 6] According to a further embodiment of the invention, the tow point defines, with 25 respect to the deck, a maximum tow point height for the place where the tow part of the towing cable applies force - in horizontal direction - to the vessel; wherein the guiding arc is provided at an arc height above the deck; wherein the arc height (H) is larger than the maximum tow point height (Y); wherein the arc height (H) is larger than the maximum tow point height (Y); and wherein the difference between the arc height (H) and the maximum 30 tow point height (Y) is: at most 4 m, preferably at most 3 m; and/or at least 0 m, preferably at least 1 m, such as about 2 m.or more. Taking into account that in general the towing cable of a tug vessel is mounted to the object at a vertical level substantially higher than the vessel - at least higher than the tow point of the vessel -, such differences difference between the arc height (H) and the maximum tow point height (Y) ensure that the ‘raising effect’ 35 counteracting heeling is so to say available as from the start of the towing operation. The smaller said distance is, the better the ‘raising effect’ is ensured for objects at larger distance from the vessel.

-4- [claim 7] According to a further embodiment of the vessel according to the invention, the guiding arc is provided at an arc height above the deck, and said arc height is: • at most 4 m, preferably at most 3m; and/or 5 • at least 0 m, preferably at least 1 m, such as about 2m or more.

On the one hand a guiding arc arranged at an height of at most 4 m, preferably at most 3 m, ensures a good raising effect when the towing point is located above deck. On the other hand a guiding arc at an height of at least 0 m, preferably 1 m or more, would ensure sufficient raising effect when the towing point is located at or near deck level.

10 [claim 8] The tow point is typically at an height of 80 to 150 cm above deck when the winch foundation is placed on deck It is preferred however to have the tow point as low as possible above the deck, preferably it will lie exactly on the deck, To achieve this, the winch foundation could be located below deck level or a fairlead or bitt could be placed at deck level to guide the towing wire at deck level. According to a further embodiment of the 15 invention, the tow point is provided at 0 to 150 cm above deck level, preferably at an height of 0 to 80 cm, such as at an height of about 0 to 20 cm, above deck level.

According to an embodiment of the invention, the tow point thus can be arranged at about deck level (0-20 cm above deck level) with the guiding arc 0 cm to 100 cm above the deck level.

20 [Claim 9] According to a further embodiment of the invention, wherein the guiding arc extends, with respect to the tow point, along an arc angle of at least 90°, preferably along an arc angle of at least 130°, more preferably along an arc angle of at least 180°. The larger the arc angle, the larger the freedom of operation when towing.

[claim 10] According to a further embodiment of the invention, the guiding arc extends, 25 with respect to the fairlead, along an arc angle of at most 270°, preferably along an arc angle of at most 240°. This allows deck space for superstructures, accommodations for personell, etcetera.

[claim 11 ] According to a further embodiment of the invention, the vessel has a continuous bollard pull of at least 300 kN (= 30 t BP), preferably at least 450 kN (= 451 BP), 30 such as at least 650 kN (= 65 t BP).

[claim 12] According to a further embodiment of the invention, the vessel has a continuous bollard pull of at 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, 35 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 in tons. The bollard pull value represents the maximum pulling force that a vessel can exert -5- 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 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 5 (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 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 ( 10 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, 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) 15 [claim 13] According to a further embodiment of the invention, the towing cable extends from the tow point, along the deck, and underneath the guiding arc. During towing operation, the towing cable continues to extend outboard from the guiding arc to the object to which the guiding cable is attached.

[claim 15] According to a further embodiment of the invention, the tow point is provided 20 at a distance of 30% to 50 % of the length of the vessel, 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 under water body of the vessel. This allows easy positioning of the vessel with respect to the towing cable.

According to the invention, the tow point can be formed by a bitt or a tow hook, which 25 both actually attach the towing cable to the vessel at the location of the tow point.

[claim 16] According to a further embodiment of the invention, the towing device further comprises a fairlead for guiding the towing cable, wherein the fairlead forms the tow point. This allows the towing cable to be attached to the vessel in another more practical location, [claim 17] According to another further embodiment of the invention, the towing device 30 further comprises: a towing winch mounted on the vessel for winding and unwinding the towing cable; and a fairlead for guiding the towing cable towards the towing winch. Here the fairlead provides guidance for the towing cable in order to ensure it is properly received on the winch. The winch allows the length of the tow part of the towing cable to be adjusted depending from circumstances.

35 [claim 18] According to a further embodiment of the invention, the towing winch is provided at the vertical longitudinal sectional plane of the vessel. This provides a symmetric weight distribution over the vessel.

-6- [claim 19] According to a further embodiment of the invention, the towing winch is, measured from the stern of the vessel, provided at a distance of 30% to 60 % of the length of the vessel, preferably at a distance of about 40% to 50% of the length of the vessel. This provides a symmetric weight distribution over the vessel.

5 [claim 20] According to a further embodiment of the invention, the fairlead comprises 2 rotatable rollers, wherein the rollers are arranged mutually parallel with the longitudinal axes essentially transverse to the deck, and wherein, viewed in a direction parallel to the deck, a gap is provided between the rollers, the gap having width larger than or equal to the thickness of the towing cable. Such a fairlead wioth rotatable rollers reduces, if not 10 eliminates, friction between the towing cable and the fair lead. Further the rollers prevent sharp bents being formed in the towing cable.

[claim 21] According to a further embodiment of the invention, the gap plane defined by the gap extends essentially perpendicular to the longitudinal direction of the vessel. This allows the tow part of the towing cable to swing equally well to the port side of the vessel 15 and to the starboard side of the vessel.

[claim 22] According to a further embodiment of the invention, the vessel is a tug vessel, [claim 23] According to a further embodiment of the invention, the guiding arc is arranged to absorb shocks acting in vertical direction on the guiding arc as a result of shock loads on the towing cable. During towing operations, shock loads on the towing cable 20 frequently occur as the towing cable will not be taut permanently but the towing cable will tauten frequently due to for example the action of waves, elastic properties of the towing cable, the towing vessel changing from passive accompanying or attending operation to active towing or guiding operation as action is required. The result of tautening of the towing cable is that thetowing cable is subject to high shock loads, which can be as high as 4 to 6 25 times the Bollard Pull of the vessel . In order to reduce these shocks, the guiding arc is arranged to absorb shocks acting in vertical direction. In this respect it is to be noted that a guiding arc which is rigidly connected at its ends to the vessel and in between these ends unsupported extending in a horizontal plane will - in accordance with the invention - act as a shock absorber as it will, due to vertical shocks, elastically flex upward/downward.

30 [claim 24] According to a further embodiment of the invention the vessel comprises at least one shock absorber acting in vertical direction, one end of the shock absorber being mounted to the vessel and the other end of the shock absorber being mounted to the guiding arc. A separate or additional shock absorber improves the shock absorbing properties of the guiding arc.

35 [claim 25] According to a further embodiment of the invention wherein the vessel comprises at least one shock absorber, it is advantageous when both ends of the guiding arc are supported in hinging manner on a support. Such support allowing hinging of the -7- guiding arc around an axis parallel to the deck, prevents the guiding arc from being deformed by shock loads acting on the guiding arc. The at least one shock absorber can than be arranged above the guiding arc so that the underside of the guiding arc stays free for unhindered movement of the towing cable.

5 [claim 26] According to a further preferred embodiment of the invention, it is advantageous when rigid extensions are provided at both ends of the guiding arc, wherein the extensions are rigidly attached to the guiding arc, extend from the guiding arc beyond the supports up to the shock absorber, and are attached to the shock absorber. This allows the at least one shock absorber -in this case at least one at each end of the guiding arc - to 10 be provided lower than the guiding arc outside the span of the guiding arc so that on the one hand the towing cable can move unhindered along the entire span of the guiding arc and on the other hand easier construction and saving of constructional space in vertical direction is possible.

15 Below, the invention will be further explained with reference to the drawings. In these drawings:

Figure 1 shows a very schematic perspective top view on a vessel according to the invention;

Figure 2 shows the same view as figure 1, but with a focus on dimensions of the vessel; 20 Figure 3 shows a very schematic representation of the forces acting on a vessel according to the invention, wherein the vessel is seen from the heck; and

Figure 4 shows highly schematic as a detail the support of the guiding arc on the vessel.

Figure 1 shows a vessel 10 according to the invention. This vessel 10 comprises a deck 11 25 and towing device. The deck has a back part 5 on which the towing device is provided and a front part 6. The towing device comprises a winch 3, a fairlead 14, a towing cable 2 and a guiding arc 1.

The ends 27 of the guiding arc 1 are supported on the vessel 10 by supports 24. In figure 1 30 these supports are vertical columns projecting from the deck 11. However, it will be understood that these supports can also be of different type, for example it is also conceivable that the ends 27 of the guiding arc is supported by a superstructure on the front part 6 of the deck, like an accommodation for personnel. In between the ends 27 of the guiding arc 1, the guiding arc 1 is free of obstacles, at least at the underside of it, so that the 35 towing cable 2 can move unhindered along - the underside of - the guiding arc 1, as will be described more detailed below.

-8-

The towing cable 2 can be wound up and unwound from the winch depending on the length needed. Starting from the winch 3 the towing cable 2 extends to the fairlead 14, passes through the fairlead 14, extends along the deck 11, passes underneath the guiding arc 1, and continues extending outboard to the object 8 onto which the towing cable exerts a 5 tensile force. The part of the towing cable 2 extending from the fairlead 14 up to the object 8 is called the ‘tow part 12’ (of the towing cable 2). From the guiding arc 1 outboard to the object, the towing part in general extends in a slanting upward direction as the object 8 - at least the point where the towing cable is fixed to the object - lies in general at a vertical level which is higher than the vertical level of the guiding arc. Thus the towing part 2 will contact 10 the lower side 9 of the guiding arc 1, which lower side faces the deck.

When the positioning of the vessel 10 with respect to the object 8 changes, the tow part 12 of the towing cable 2 swings around the vertical swivel axis 7 defined by the fairlead 14. The guiding arc 1 serves in this respect as a guide for the tow part 2. For example, the tow part 15 can swing an angle y from a first position indicated in figure 1 with the solid line to a second position shown as dashed line in figure 1. The (mathematical) projection of the tow part 2 on a horizontal plane is essentially a straight line. Also during swinging of the straight part 2 around the vertical swivel axis, the projection of the tow part 2 on a horizontal plane will essentially be a straight line.

20

The fairlead 14 comprises two rotatable rollers 15 which are arranged mutually parallel with their longitudinal axes perpendicular to the deck 11. The rollers 15 are spaced apart to provide a gap 16 in between. The width Z of this gap 16 is sufficient to allow the towing cable to pass through between the rollers 15. The width Z of the gap 16 is thus larger than 25 or equal to the thickness of the towing cable 2. As the rollers 15 are rotatable, slippage of the towing cable 2 over the rollers is prevented.

The fairlead 14 serves to guide the towing cable 2 correctly onto or from the winch 3. It is however also conceivable that there are arranged one or more cable guides between the 30 fairlead and the winch. It is also conceivable that there is arranged a clamping device on the winch or between the fairlead and the winch in order to clamp the towing cable for relieving the winch. Instead of a fairlead, a bitt, a clamp or a tow hook can be provided as well according to the invention. In case of a bitt or tow hook, the towing cable will be fixed to the vessel by the bitt or tow hook. In all cases - fairead, bitt, tow hook or otherwise - there is a 35 tow point 4 which defines a vertical swivel axis 7 for the tow part 12 of the towing cable 2 , on the one hand, and where the towing cable 2 exerts a horizontal force FH - also called heeling force - onto the vessel 10, on the other hand.

-9-

Taking into account that the fairlead 14 allows some vertical movement of the towing cable in the gap 16 between the rollers, there is, with respect to the deck 11, a maximum tow point height Y for the place where the tow part 12 of the towing cable 2 leaves the tow point 4.

5 Further, the guiding arc is arranged at an arc height H above the deck. In order to ensure good raising properties in case of heeling of the vessel, the arc height H, i.e. the vertical distance between the guiding arc 1 and the deck 11, is at most 4 m. The raising properties are improved by lowering the arc height H with respect to the deck. In order to allow personnel to pass underneath the guiding arc 1 and/or towing cable resting against the 10 lower side 9 of the guiding arc 1, the arc height H is preferably at least 1 m. In order to allow this personnel to pass easily underneath the guiding arc 1 and/or underneath said towing cable 2, the arc height is preferably about 2 m or more.

The guiding arc 1 is provided at a distance X of at least 1 m from the tow point 4. The 15 guiding arc 2 can have a continuous curvature, i.e. extend along a fixed radius with respect to a centre point - like the tow point 4-, but in practise the curvature does not have to be continuous. Taking into account that the distance from the tow point 4 to the stern 13 of the vessel is, in the shown embodiment, substantially larger than the distance from the tow point 4 to the sides 17 of the vessel 10, the vessel will be substantially less sensitive to trimming 20 (=heeling around the transverse axis 19) of the vessel than to heeling around the longitudinal axis transverse axis 18. Therefore, the distance from the tow point 4 to the guiding arc as measured in the direction of the stern, might be smaller than the distance from the tow point to the guiding arc as measured in the transverse direction of the vessel (i.e. parallel to transverse axis 19). Further, as can be seen in figures 1 and 2 the end parts 25 of the guiding arc 1 can be essentially straight. It is also conceivable that the guiding arc is essentially U-shaped with a central straight part extending in transverse direction of the vessel and two straight leg parts joining the central straight part with a sharply end connection.

30 Referring to figure 2 the guiding arc 1 extends over an arc angle 8, which in the shown embodiment is about 270°.

Further referring to figure 2, some indicative measures of the shown embodiment are as follows: 35 • D indicates the largest width of the guiding arc, which in this indicative embodiment is about 5 m; -10- • L indicates the length of the vessel, which is in this indicative embodiment is about 25-40 m; • H indicates the height of the guide arc, which is in this indicative embodiment is about 2 m; 5 • Y indicates the tow point height, which is in this indicative embodiment is about 1 m; • B indicates the width of the vessel, which is in this indicative embodiment is about 10-15 m; • L4 indicates the distance from the stern of the vessel to the fairlead, which is in this indicative embodiment is about 40%-45% of L m; 10 • L3 indicates the distance from the stern of the vessel to the winch, which is in this indicative embodiment is about 20 m; • L1 indicates the distance from the fairlead to the whinch, which is in this indicative embodiment is about 3 m; and • L2 indicates the distance - in length direction of the vessel - from the fairlead to the 15 end of the guiding arc, which is in this indicative embodiment is about 2 m.

Figure 3 shows a schematic representation of forces acting on the vessel according to the invention, when a tensile force is exerted on an object 8. The vessel 10 is shown in a heeled position with respect to the water level 20. The tow part of towing cable 2 exerts a tensile 20 force F to the object 8. This tensile force F is made up of 2 components, a horizontal force Fh, also called heeling force, acting in transverse direction on the vessel and a vertical force Fr- also called righting force - acting in vertical direction on the vessel. The tow point 4 is the point of application of the horizontal force FH. The underside 9 of the guiding arc 1 is the point of application of the vertical force FR. As this horizontal force FH acts on the vessel at a 25 level higher than the centre of buoyancy 21/centre of gravity 22 of the vessel 10 and because the vessel experiences in side ward direction a resistance from the water (force LCR), the horizontal force FH will cause a heeling of the vessel 10. As shown in figure 3, the tow part 4 of the towing cable 2 exerts at the point of contact 23 with the guiding arc 1 an upward vertical force FR on the guiding arc 1. This vertical force FR - also called righting 30 force - counteracts heeling of the vessel 10.

The guiding arc will in general be made from steel or another metal alloy or other material common for these kind of structures in vessels. As shown in figure 1, the ends 27 of the guiding arc 1 can be rigidly connected to the supports 24 by, for example, forming the 35 supports 24 as an integral part of the the guiding arc or in different manner. Taking into account the inherent flexibility of the guiding arc 1 in vertical direction (the guiding arc will be -11 - able to flex around a horizontal axis in vertical direction) in reaction to transverse (i.e. vertical) forces, the guiding arc 1 will be able to absorb shocks exerted by the towing cable when the towing cable is tightened. This shock absorbing can be improved by providing one or more shock absorbers 26, see for example in figure 4 which shows schematically a 5 cylinder piston unit which can be filled with gas (or liquid) for shock absorbing. In order to prevent the guiding arc from being deformed by shocks or to prevent the attachment of the guiding arc to the support 24 becoming damaged it is advantageous to attach the ends 27 of the guiding arc 1 by means of a hinge 28 to the supports and to use additional shock absorbers 26 for absorbing shocks. Taking into account that the towing cable 2 moves along 10 the underside of the guiding arc 1, the upper side of the guiding arc 1 is available for attaching one or more shock absorbers 26. Referring to figure 4 it is however preferred to provide the ends 27 of the guiding arc with extensions 25 projecting beyond the hinge 28 and to provide one or more shock absorbers 26 between each extension 25 and the vessel 10, preferably the deck 11 of the vessel.

15

The invention can be further described by the next following clauses.

1] Vessel (10), such as a tug vessel, comprising a deck (11) and a towing device, wherein the towing device comprises: • a towing cable (2); 20 • a tow point (4) - such as a fairlead, a bitt, or a tow hook - where the towing cable (2) exerts horizontal force onto the vessel (10) when applying a tensile force to an object (8) by means of the towing cable (2), the tow point (4) being provided on the vessel (10); • a guiding arc (1) mounted on the vessel (10), wherein, viewed in vertical direction, 25 the guiding arc is arranged above the deck (11), and wherein the guiding arc (1) extends along the deck (11); wherein the towing cable (2) has a tow part (12), which is defined as that part of the towing cable (2) which extends from the tow point (4) to the object (8) when applying a tensile force to the object (8) by means of the towing cable (2); 30 characterised, in that the tow point (4) is provided at the vertical longitudinal sectional plane of the vessel (10) and defines a vertical swivel axis (7) for the tow part (12) of the towing cable (2); in that, viewed in a direction parallel to the deck (11), the guiding arc (1) is arranged at a distance (X) from the tow point (4), which distance (X) is preferably larger than 1 m, more 35 preferably larger than 2 m; and in that the guiding arc (1) is arranged for guiding the tow part (12) of the towing cable (2) along the deck (11) while swinging the tow part (12) of the towing cable (2) around the - 12- swivel axis (7) and for supporting the tow part (12) of the towing cable (2) in upward direction while applying a tensile force to an object (8).

2] Vessel (10) according to clause 1, wherein the guiding arc (1) is essentially symmetrically with respect to the vertical longitudinal sectional plane of the vessel (10).

5 3] Vessel (10) according to one of the preceding clauses, wherein the guiding arc (1) has lower side (9), which lower side (9) faces the deck (11) and forms a guiding surface for sideways displacement of the tow part (12) of the towing cable (2) when the tow part (12) of the towing cable (2) swings around the swivel axis (7).

4] Vessel (10) according to clause 3, wherein the guiding surface extends uninterrupted 10 along the entire guiding arc (1).

5] Vessel (10) according to one of the preceding clauses, wherein the distance (X) between the tow point (4) and the guiding arc (1) is at least 1 m, preferably at least 3 m, such as at least 6 m.

6] Vessel (10) according to one of the preceding clauses, wherein the tow point (4) 15 defines, with respect to the deck (11), a maximum tow point height (Y) for the place where the tow part (12) of the towing cable (2) applies force to the vessel (10); wherein the guiding arc (1) is provided at an arc height (H) above the deck (11); wherein the arc height (H) is larger than, or equal to the maximum tow point height (Y); and wherein the difference between the arc height (H) and the maximum tow point height (Y) is: 20 • at most 4 m, preferably at most 3 m; and/or • at least 0 m, preferably at least 1 m, such as about 2 m or more.

7] Vessel according to one of the preceding clauses, wherein the guiding arc (1) is provided at an arc height (H) above the deck (11), and wherein said arc height (H) is: 25 • at most 4 m, preferably at most 3m; and/or • at least 0- m, preferably at least 1 m, such as about 2 m or more.

8] Vessel according to one of the preceding clauses, wherein the tow point (4) is provided at an height of 0 to 150 cm above the deck, preferably at an height of 0 to 80 cm, 30 such as at an height of about 0 to 20 cm, above the deck.

9] Vessel (10) according to one of the preceding clauses, wherein the guiding arc (1) extends, with respect to the tow point (4), along an arc angle (3) of at least 90°, preferably along an arc angle (8) of at least 130°, more preferably along an arc angle (8) of at least 180°.

35 10] Vessel (10) according to one of the preceding clauses, wherein the guiding arc (1) extends, with respect to the fairlead, along an arc angle (8) of at most 270°, preferably along an arc angle (3) of at most 240°.

-13- 11] Vessel (10) according to one of the preceding clauses, wherein the vessel (10) has a 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).

12] Vessel (10) according to clause 9, wherein the vessel (10) has a continuous bollard 5 pull of at most 1500 kN (= 150 t BP).

13] Vessel (10) according to one of the preceding clauses, wherein the towing cable (2) extends from the tow point (4), along the deck (11), and underneath the guiding arc (1).

14] Vessel (10) according to clause 11, wherein the towing cable (2) extends outboard from the guiding arc (1) to the object (8) to which the guiding cable (2) is attached.

10 15] Vessel (10) according to one of the preceding clauses, wherein, measured from the stern (13) of the vessel (10), the tow point (4) is provided at a distance (L4) of 30% to 50 % of the length (L) of the vessel (10), preferably at a distance (L4) of about 40% to 45% of the length of the vessel (10).

16] Vessel (10) according to one of the preceding clauses, wherein the towing device 15 further comprises a fairlead (14) for guiding the towing cable (2), and wherein the fairlead (14) forms the tow point (4).

17] Vessel (10) according to one of the preceding clauses, wherein the towing device further comprises: • a towing winch (3) mounted on the vessel (10) for winding and unwinding the towing 20 cable (2); and • a fairlead (14) for guiding the towing cable (2) towards the towing winch (3).

18] Vessel (10) according to clause 17, wherein the towing winch (3) is provided at the vertical longitudinal sectional plane of the vessel (10).

19] Vessel (10) according to one of clauses 17-18, wherein, measured from the stern 25 (13) of the vessel (10), the towing winch is provided at a distance (L3) of 30% to 60 % of the length (L) of the vessel (10), preferably at a distance (L3) of about 40% to 50% of the length (L) of the vessel (10).

20] Vessel (10) according to one of the clauses 16-19, wherein the fairlead comprises 2 rotatable rollers (15), wherein the rollers (15) are arranged mutually parallel with their 30 longitudinal axes essentially transverse to the deck (11), and wherein, viewed in a direction parallel to the deck (11), a gap (16) is provided between the rollers (15), the gap (16) having a width (Z) larger than or equal to the thickness of the towing cable (2).

21] Vessel (10) according to clause 20, wherein the gap plane defined by the gap (16) extends essentially perpendicular to the longitudinal direction (L) of the vessel (10).

35 22] Vessel (10) according to one of the preceding clauses, wherein the vessel (10) is a tug vessel (10).

- 14- 23] Vessel (10) according to one of the preceding clauses, wherein the guiding arc (1) is arranged to absorb shocks acting in vertical direction on the guiding arc (1) as a result of shock loads on the towing cable (2).

24] Vessel (10) according clause 23, further comprising at least one shock absorber 5 acting in vertical direction, one end of the shock absorber (26) being mounted to the vessel and the other end of the shock absorber being mounted to the guiding arc (1).

25] Vessel according to clause 24, wherein both ends (27) of the guiding arc (1) are supported in hinging manner on a support (24).

26] Vessel according to claim 25, wherein rigid extensions (25) are provided at both ends 10 (27) of the guiding arc (1), wherein the extensions (25) are rigidly attached to the guiding arc (1), extend from the guiding arc (1) beyond the supports (24) up to the shock absorber (26), and are attached to the shock absorber (26).

It will be clear to the skilled man that within the scope determined by the claims, many variants of the invention are conceivable. For example, within the scope of the claims, the 15 towing cable can be made of any suitable material and/or structure like steel, rope, fibre etcetera.

Further it is to be noted, that when the vessel according to the invention is at a sufficient large distance from the object towed, the towing cable will sag and possibly touch the water 20 or hang in the water. In this situation the towing cable will not exert a vertically upward force on the guiding arc. Depending on the construction, the towing cable might not touch the guiding arc at all in this situation. This does however not mean that the vessel is not according to the invention because when the towing vessel is near enough to the towed object, the towing cable will exert a vertical upward force on the guiding arc. The vessel 25 according to the invention is especially very useful in situations when the vessel is relatively close to the towed object, like in harbours and on canals or rivers. Further it is to be noted, that the vessel according to the invention can be used for tugging - 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 30 direction of the towed object, behind the towed object.

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List of used reference numbers/signs 1 guiding arc 2 towing cable 3 winch 4 tow point 5 back part of deck 6 front part of deck 7 swivel axis 8 object 9 lower side of guiding arc 10 vessel 11 deck 12 tow part of towing cable 13 stern 14 fairlead 15 roller 16 gap 17 side of vessel 18 longitudinal axis of vessel 19 transverse axis of vessel 20 water level 21 centre of buoyancy 22 centre of gravity 23 point of contact between guiding arc and tow part of towing cable 24 support for guiding arc 25 extension of guiding arc 26 shock absorber 27 end of guiding arc 28 hinge

Ar distance between forces B and FR Ah distance between forces FH and LCR

B buoyancy force G gravity force F tensile force

Fr vertical component of tensile force, righting force -16-

Fh horizontal component of tensile force, heeling force H arc height L length of vessel L1 distance in length direction of vessel between winch and fairlead L2 distance in length direction of vessel between fairlead and ends of guiding arc L3 distance in length direction of vessel between stern and winch L4 distance in length direction of vessel between stern and fairlead LCR water resistance force X distance from tow point to guiding arc Y tow point height Z width of gap a angle of tensile force with respect to horizontal 3 arc angle Y swing angle of tow part

Claims

A vessel (10) comprising a deck (11) and a towing device, the towing device comprising: • a towing wire (2); • a towing point (4) provided on the vessel (10) where the towing wire (2), when exerting a pulling force on an object (8) by means of the towing wire (2), exerts horizontal force on the vessel (10); • a guide arc (1) mounted on the vessel (10), viewed in vertical direction, above the deck (11), which arch extends along the deck (11); wherein the towing wire (2) has a pulling portion (12) defined as the portion 10 of the towing wire (2) which, upon exerting a pulling force on an object (8) by means of the towing wire (2), extends from the drag point (4) to the object (8); characterized in that the towing point (4) is provided in the vertical longitudinal longitudinal plane of the vessel (10) and defines a vertical pivot axis (7) for the towing portion (12) of the towing wire (2); That, viewed in a direction parallel to the deck (11), the guide arch (1) is arranged at a distance (X) from the towing point (4); that the guide arc (1) is arranged to guide the pull section (12) of the towing wire (2) along the deck (11) when pivoting said pull section (12) around the pivot axis (7) and, when exerting a tensile force on the object (8), to support the pulling part (12) of the towing wire (2) in an upward direction.

Vessel (10) according to claim 1, wherein the guide arch (1) is essentially symmetrical with respect to the vertical longitudinal plane of the vessel (10). 25

Vessel (10) as claimed in any of the foregoing claims, wherein the underside (9) of the guide arch (1) facing the deck (11) forms a guide surface for lateral displacement of the pulling section (12) of the towing wire (2) at pivoting the pull section (12) around the pivot axis (7). 30

Vessel (10) according to claim 3, wherein the guiding surface extends continuously along the entire guiding arc (1).

5. Vessel (10) according to one of the preceding claims, wherein the distance (X) between the towing point (4) and the guide arch (1) is at least 1 m, preferably at least 3 m, such as at least 6 m. -18-

Vessel (10) according to one of the preceding claims, wherein the towing point (4), relative to the deck (11), determines a maximum towing height (Y) for the place where the towing section (12) of the towing wire ( 2) engages the vessel (10); wherein the guide arc (1) is provided at an arc height (H) above the deck (11), the arc height (H) being greater than or equal to the maximum towing point height (Y); and wherein the difference between the arc height (H) and the maximum towing point height (Y): is at most 4 m, preferably at most 3 m; and / or 10. is at least 0 m, preferably at least 1 m, such as 2 m or more.

Vessel according to any one of the preceding claims, wherein the guide bow (1) is provided at a bow height (H) above the deck (11), and wherein this bow height (H): • at most 4 m, preferably is 3 m at most; 15 and / or • is at least 0 m, preferably at least 1 m, such as 2 m or more.

A vessel according to any one of the preceding claims, wherein the towing point (4) is located at a height of 0 to 150 cm above the deck, preferably at a height of 0 to 80 cm, such as at a height of about 0-20 cm .

Vessel (10) according to one of the preceding claims, wherein the guide arc (1), viewed with respect to the towing point (4), extends over an arc angle ((B) of at least 90 °, preferably over an arc angle ( P) of at least 130 °, more preferably over an arc angle (P) of at least 180 °.

Vessel (10) according to one of the preceding claims, wherein the guide arc (1), viewed with respect to the towing point (4), extends over an arc angle (P) of at most 270 °, preferably at most 240 °. 30

Vessel (10) according to one of the preceding claims, wherein the vessel (10) has a continuous pile pulling force (continuous bollard pull) of at least 300 kN («30 t BP), preferably at least 450 kN (= 451 BP), such as at least 650 kN (65 651 BP). 35

Vessel (10) according to claim 11, wherein the vessel (10) has a continuous pile pulling force (continuous bollard pull) of at most 1500 kN (= = 150 t BP). -19-

A vessel (10) according to any one of the preceding claims, wherein the towing wire (2) extends from the towing point (4), along the deck (11), and along the guide arch (1).

A vessel (10) according to claim 13, wherein the towing wire (2) extends outboard 5 from the guide arc (1) to the object (8) to which the towing wire (2) is attached.

Vessel (10) as claimed in any of the foregoing claims, wherein the towing point (4) is located at a distance (L4) of 30% to 50%, measured from the rear (13) of the vessel (10) length (L) of the vessel (10), preferably at a distance (L4) of about 40% to 45% of the length (L) of the vessel (10).

Vessel (10) as claimed in any of the foregoing claims, wherein the towing device further comprises a wire guide (14) for guiding the towing wire (2), and wherein the wire guide (14) forms the towing point (4).

Vessel (10) according to any one of the preceding claims 1-15, wherein the towing device further comprises: • a towing winch (3) mounted on the vessel (10) for winding and unwinding the towing wire (2); and • a wire guide (14) for guiding the tow wire (2) to the tow winch (3).

Vessel (10) according to claim 17, wherein the towing winch (3) is provided in the vertical middle longitudinal plane of the vessel (10). 25

Vessel (10) according to any of claims 17-18, wherein the towing winch (3) is placed on a distance (L3) of 30% to 60%, measured from the rear (13) of the vessel (10) from the length (L) of the vessel (10), preferably at a distance (L3) of about 40% to 50% of the length (L) of the vessel (10). Vessel (10) as claimed in any of the claims 16-19, wherein the wire guide (14) comprises two rotatable rollers (15), the rollers (15) being arranged mutually parallel with their longitudinal center lines substantially transverse to the deck ( 11), and wherein, viewed in a direction parallel to the deck (11), a gap (16) is left between the rollers (14) with a width (Z) greater than or equal to the thickness of the drag wire (2) ).

-20-

Vessel (10) according to claim 20, wherein the slit surface tensioned by the slit (16) extends substantially perpendicular to the longitudinal direction (L) of the vessel (10).

Vessel (10) according to any one of the preceding claims, wherein the vessel (10) is a tugboat.

Vessel as claimed in any of the foregoing claims, wherein the guide arc (1) is designed to absorb shock absorbing forces acting on the guide arc in the vertical direction as a result of shock loads on the towing wire. 10

A vessel according to claim 23, further comprising at least one shock absorber (26) operating in vertical direction, one end of which is attached to the vessel and the other end of which is attached to the guide arc (1). 15

Vessel according to claim 24, wherein the two ends (27) of the guide arch (1) are hingedly supported on a support (24).

Vessel according to claim 25, wherein at the ends (27) of the guide arc (1) extensions (25) are provided, which are rigidly connected to the guide arc (1), which extend beyond the supports from the guide arc (26) (24) extend to a said shock absorber (26) and are attached thereto.