NZ734320B2

NZ734320B2 - Tugboat provided with a carrousel-type towing system

Info

Publication number: NZ734320B2
Application number: NZ734320A
Authority: NZ
Inventors: Cornelis Levinus Muller
Original assignee: Nova Patent Bv
Filing date: 2016-02-02
Publication date: 2023-11-28

Abstract

The invention relates to a tugboat (1), comprising a single hull (2), a deck (3) and a towing system (4) having a base (5) connected to the deck, the base having a centre point (CP), and a cart (6) that is moveable over the base over 360°, wherein the cart comprises a powered winch (7), wherein two propulsion units (12) are provided, capable of providing thrust over 360° in a horizontal plane, wherein the propulsion units are aligned in the longitudinal direction, wherein the distance between the propulsion units is at least 10% of a length (L) of the tugboat in the longitudinal direction, wherein the tugboat is configured such that during towing the vertical distance between the centre point and the waterline (Hcp) divided by the vertical distance between the centre of thrust of the propulsion units and the waterline (Hp) is 0,3 - 1,5. The problems to be solved are the excess thrust needed and the high likelihood of rolling or capsizing with the current systems. The invention solves this by improving the placement of the propulsion units which improves counterforces.

Description

t provided with a carrousel-type towing system Field of the invention id="p-1" id="p-1" id="p-1" id="p-1" id="p-1"

[0001] The present invention relates to a tugboat with a carrousel-type towing system.

Background of the invention Such a t is known from for instance applicant.

A disadvantage of the known carrousel-type tugboat is that the propulsion forces are not positioned in the most optimal way to control the tugboat’s heading during towing.

Another disadvantage is that a lot of engine thrust is needed to control the tugboat’s g.

It is therefore an object of the present invention to provide a tugboat with a carrousel-type towing system that allows the most optimal control of the t and to utilize the power of the carrousel-type tugboat to its full extent.

It is a further object of the invention to provide a tugboat having a carrousel-type towing construction, wherein the amount of engine thrust needed to te the desired amount of towing force is decreased.

Summary of the ion In a first aspect, the present invention provides a t having a longitudinal direction and comprising a single elongated hull, a deck and a carrousel-type towing system having a circular base connected to the deck, the base having a centre point, the towing system further comprising a cart that is moveable over the base over 360o, wherein the cart comprises a powered winch during use provided with a tug cable for towing vessels, wherein a propulsion system is connected to the hull, for providing a propulsive force in a body of water, the propulsion system comprising two propulsion units each arranged below the hull’s draft and capable of providing thrust over 360o in a plane below the hull’s draft and perpendicular to the tugboat’s vertical plane of ry, said vertical plane of symmetry extending in the longitudinal direction of the t, wherein the propulsion units are positioned in the vertical plane of symmetry and are aligned in the longitudinal direction, n one of the propulsion units is positioned in front of the centre point and the other one is positioned behind the centre point when seen along the longitudinal direction, and the distance between the sion units is at least 10% of a length of the tugboat in the longitudinal direction, wherein the tugboat is ured in such a way that during towing the vertical distance between the centre point and the waterline d by the vertical distance between the centre of thrust of the propulsion units and the waterline is 0,3 – 1,5. Hereto, the t according to the invention is characterized in that the propulsion system comprises two propulsion units (12) each capable of providing thrust over 360 o in a plane perpendicular to a vertical plane of symmetry (13) extending in a udinal direction (X) of the tugboat, wherein the propulsion units are positioned in the vertical plane of symmetry and are aligned in the longitudinal direction, wherein one of the propulsion units is positioned in front of the centre point and the other one is positioned behind the centre point and the distance between the propulsion units is at least 10% of a length (L) of the tugboat in the longitudinal direction, wherein the tugboat is configured in such a way that during towing the al distance between the centre point and the waterline (Hcp ) divided by the vertical distance between the centre of thrust of the sion units and the waterline (H p) is 0,3 – 1,5. Preferably the ratio is 0,6 – 1,1.

These combined features, and in particular the described values, allow the power of the carrousel-type tug system to be fully utilized and less engine thrust is needed to generate sufficiently large towing forces. The resistance of the hull itself can be advantageously used to create a counterforce opposed to the pulling force of the tug cable and thus tension in the tug cable can be sed to huge values t needing a lot of engine thrust. This is particularly relevant when pulling in a direction perpendicular to the longitudinal direction of the tugboat. The applicant has found that the stated values for Hp provide optimal stability to the tugboat. For values larger than 1,5 applicant has found that the tugboat gets ed too much above the waterline, causing the positive effect on ity to be almost fully negated. The vertical distance between the centre point and the waterline (Hcp ) can for instance be 1,5 – 4,5 m. The vertical dis tance between the centre of thrust of the propulsion units and the waterline (Hp) can for example be 3 – 5 m.

Having one of the propulsion units positioned in front of the centre point and the other one positioned behind the centre point, wherein the distance between the propulsion units is at least 10%, preferably at least 20% or more preferably at least 30%, of a length (L) of the vessel in the longitudinal direction, allows for tion of s acting around a vertical axis of the vessel with only minimal amounts of engine thrust. id="p-10" id="p-10" id="p-10" id="p-10" id="p-10"

[0010] During tests, the applicant has achieved the ing surprisingly positive results with the configuration according to the invention: - At a speed of 10 knots, with only 2825 kW of propulsive power installed, a steering force of 161t has been achieved; - At a speed of 10 knots, with only 2014 kW of propulsive power installed, a bracking force of 144t has been achieved; and - At a speed of 10 knots, with only 1045 kW of propulsive power installed, a braking force of 136t combined with a ng force of 75t has been achieved; The multiplication factor of dynamic forces (at speed 10 knots; 161 t) relative to static force (static pull and function of used power; 2825 kW = 40 t static pull) is approximately 4, which is unheard of.

This means that a r hull can be used, but the tugboat is still able to generate the high dynamic forces that are required during escort assistance.

Another embodiment relates to an entioned tugboat, wherein the propulsion units comprise one or more Voith Schneider Propellers (VSP’s). Such VSP’s are particularly useful for generating sideways forces, especially when towing at large towing .

Another embodiment s to an aforementioned tugboat, wherein the propulsion units comprise one or more azimuth thrusters. Such thrusters can also be advantageously used to generate sideways forces.

The invention also relates to a method of operating a t as bed above, comprising the steps of: - configuring the tugboat to attain such a draft du ring towing that the vertical distance between the centre point and the waterline (Hcp ) divided by the vertical distance between the centre of thrust of the propulsion units and the waterline (Hp) is 0,3 – 1,5. - connecting the tug cable to a vessel to be towed and maneuvering the tugboat in such a way that the tug cable extends at an angle of 45 - 90o to the longitudinal direction of the vessel, - operating the powered winch such that the tug cab le is under tension, wherein a hydrodynamic resistance force created by the submerged hull is used to se the tension of the tug cable, - using the propulsion units to correct the orienta tion of the t with t to the vessel to be towed. id="p-16" id="p-16" id="p-16" id="p-16" id="p-16"

[0016] Such a method advantageously s the hydrodynamic resistance force created by the submerged hull to increase the tension of the tug cable, without needing a lot of thrust from the propulsion units to achieve this.

Preferably, the orientation of the tugboat is corrected with the propulsion units in such a way, that the tug cable remains at an angle of 45 - 90o to the longitudinal direction of the tugboat, such that the hydrodynamic resistance of the hull (both for withstanding moments as well as withstanding movement due to the tension in the tug cable) stays relatively high. id="p-18" id="p-18" id="p-18" id="p-18" id="p-18"

[0018] More preferably, the orientation of the tugboat is ted with the sion units in such a way, that the tug cable remains at an angle of about 90o to the longitudinal direction of the tugboat. In this way, the hydrodynamic resistance of the hull in sideways direction remains as high as reasonably possible.

Brief description of the drawings An embodiment of a tugboat according to the invention will by way of nonlimiting example be described in detail with reference to the accompanying gs. In the drawings: Figure 1 shows a side view of a tugboat according to the invention; Figure 2 shows a front view of the tugboat according to figure 1; and Figure 3 shows a top view of the tugboat according to ?gures 1 and 2.

Detailed description of the invention Figures 1-3 will be sed in conjunction. Figure 1 shows a tugboat 1, comprising a single hull 2, a deck 3 and a towing system 4 having a circular or oval base 5 connected to the deck 3. The base 5 has a centre point CP. A cart 6 is moveable over the base 5 over 360°, wherein the cart 6 comprises a powered winch 7 during use ed with a tug cable 8 for towing vessels 9. A propulsion system 10 is connected to the lower side of the hull 2 for providing a propulsive force P in a body of water 11.

According to the invention, the sion system 10 comprises two propulsion units 12 each capable of providing a thrust or propulsive force P over 3600 in a plane perpendicular to a vertical plane of symmetry 13 that extends in a udinal direction X of the tugboat 1 (see ?gures 2 and 3). The maximum hull width Wmax can for instance be 8 — 14 m. The maximum hull height HmaX can be, for instance, 2,5 — 7 m.

The propulsion units 12 are positioned in the vertical plane of symmetry 13 and are aligned in the longitudinal direction X. One of the propulsion units 12 is positioned in front of the centre point CP and the other one is positioned behind the centre point CP and the distance between the propulsion units 12 is at least 10% of a length L of the tugboat 1 in the longitudinal direction X. The t 1 is con?gured in such a way that during towing the vertical distance between the centre point and the waterline Hep divided by the vertical distance between the centre of thrust of the propulsion units and the waterline Hp is 0,3 — 1,5. Preferably the ratio is 0,6 — 1,1, even more preferably around 0,95. The change of hull 2 draft Hdraft and thus of the stated distances Hop and Hp may be achieved by adapting the design or weight of the tugboat 1 or by using t tanks or the like.

The vertical distance between the centre point CP and the waterline Hep can for instance be 1,5 — 4,5 m. The vertical distance between the centre of thrust of the propulsion units and the waterline Hp can for example be 3 — 5 m.

The tugboat 1 may have propulsion units 12 in the form of Voith Schneider Propellers. The tugboat l as shown has propulsion units 12 comprising a pair of h thrusters.

Thus, the invention has been described by reference to the embodiments discussed above. It will be recognized that these embodiments are susceptible to s modi?cations and alternative forms well known to those of skill in the art without departing from the spirit and scope of the invention. Accordingly, although speci?c embodiments have been described, these are es only and are not limiting upon the scope of the invention.

List of reference numerals 1. Tugboat 2. Single hull 3. Deck 4. Towing system . Base 6. Cart 7. Winch 8. Tug cable 9. Vessel to be towed . sion system 11. Body of water 12. Propulsion unit 13. Vertical plane of symmetry 14. Waterline CP = centre point X = longitudinal direction L = length of the vessel HmaX = maximum hull height Hdraft = hull draft Hep = al distance between centre point and waterline Hp = vertical distance between the centre of thrust of the propulsion units and the waterline Hmax = maximum hull height Wmax = maximum hull width = tension exerted by tug cable on tugboat P = propulsive force exerted by propulsion unit on tugboat

Claims

1. Tugboat having a longitudinal direction and comprising a single ted hull, a deck and a carrousel-type towing system having a circular base connected to the deck, the base 5 having a centre point, the towing system further comprising a cart that is moveable over the base over 360o, wherein the cart comprises a powered winch during use provided with a tug cable for towing vessels, wherein a propulsion system is connected to the hull, for providing a propulsive force in a body of water, the propulsion system comprising two propulsion units each arranged below the hull’s draft and capable of providing thrust over 360o in a plane below 10 the hull’s draft and perpendicular to the tugboat’s vertical plane of symmetry, said vertical plane of symmetry extending in the longitudinal ion of the tugboat, wherein the propulsion units are positioned in the vertical plane of symmetry and are aligned in the longitudinal ion, wherein one of the propulsion units is positioned in front of the centre point and the other one is positioned behind the centre point when seen along the longitudinal direction, and the 15 distance between the propulsion units is at least 10% of a length of the tugboat in the longitudinal ion, wherein the tugboat is configured in such a way that during towing the vertical distance between the centre point and the waterline divided by the vertical distance between the centre of thrust of the propulsion units and the waterline is 0,3 – 1,5. 20

2. t according to claim 1, wherein the propulsion units comprise one or more Voith Schneider Propellers.

3. Tugboat ing to claim 1 or 2, wherein the propulsion units comprise one or more azimuth thrusters.

4. Tugboat according to any one of the preceding claims, wherein one of the propulsion units is positioned in front of the centre point and the base and the other one is oned behind the centre point and the base when seen along the longitudinal direction. 30

5. Tugboat ing to any one of the preceding claims, wherein the vertical distance between the centre point and the waterline is in the range of 1,5 – 4,5 m, and wherein the vertical distance between the centre of thrust of the propulsion units and the waterline is in the range of 3 – 5 m.

6. Tugboat according to any one of the preceding claims, wherein the tugboat is configured in such a way that during towing the vertical distance between the centre point and the waterline divided by the vertical distance n the centre of thrust of the propulsion units and the waterline is 0,6 – 1,1.

7. Tugboat according to any one of the preceding claims, wherein the distance between the propulsion units is at least 30% of the length of the vessel in the longitudinal direction.

8. Method of operating a tugboat according to any one of the ing claims, comprising 10 the steps of: - configuring the tugboat to attain such a draft du ring towing that the al distance between the centre point and the waterline divided by the vertical distance between the centre of thrust of the propulsion units and the waterline is 0,3 – 1,5. - ting the tug cable to a vessel to be towed and maneuvering the tugboat in such a 15 way that the tug cable extends at an angle of 45 - 90 o to the longitudinal direction of the vessel, - operating the powered winch such that the tug cab le is under tension, wherein a ynamic resistance force d by the submerged hull is used to increase the tension of the tug cable, - using the propulsion units to correct the a tion of the tugboat with respect to the 20 vessel to be towed.

9. Method according to claim 8, wherein the orientation of the tugboat is corrected with the propulsion units in such a way, that the tug cable remains at an angle of 45 - 90 o to the longitudinal direction of the tugboat.

10. Method according to claim 9, wherein the orientation of the tugboat is corrected with the propulsion units in such a way, that the tug cable remains at an angle of about 90o to the longitudinal direction of the tugboat. 30

11. A tugboat ing to claim 1, substantially as herein bed or exemplified with reference to the accompanying drawings.

12. A method according to claim 8, substantially as herein bed or exemplified with reference to the accompanying drawings.