DK177448B1

DK177448B1 - A moulding for mounting at the edge of a bow thruster tunnel of a boat and use of a moulding

Info

Publication number: DK177448B1
Application number: DKPA201200404A
Authority: DK
Inventors: Henrik Peter Lund
Original assignee: Henrik Peter Lund
Priority date: 2012-06-15
Filing date: 2012-06-15
Publication date: 2013-06-10

Abstract

Disclosed is a moulding (1) for mounting at the edge of a thruster tunnel (2) of a boat (3). The moulding (1) comprises a front surface (4) formed to create a substantially laminar flow over the front surface (4), and wherein the height (H) of the moulding (I) decreases from a middle area (5) of the moulding (1) towards both sides (6) of the moulding (1).

Description

i DK 177448 B1

A MOULDING FOR MOUNTING AT THE EDGE OF A BOW THRUSTER TUNNEL OF A BOAT

and Use of a moulding

Field of the invention 5 The invention relates to a moulding for mounting at the edge of a bow thruster tunnel of a boat and use of a moulding.

Background of the invention A bow thruster - also known as a bow propeller or a tunnel thruster - is known as a 10 transversal propulsion device built into the bow of a ship or boat, to make it more manoeuvrable. Bow thrusters make docking easier, since they allow the captain to turn the vessel to port or starboard side, without using the main propulsion mechanism which requires some forward motion for turning. Large ships might have multiple bow thrusters.

15 A bow thruster comprises an impeller mounted in a tunnel extending across the bow of the ship below the waterline. The impeller in the tunnel can create thrust in either direction which makes the ship turn. Most tunnel thrusters are driven by electric motors, but some are hydraulically powered. The bow thrusters may allow the ship to 20 dock without the assistance of tugboats, saving the costs of such service.

However since the bow is tapering towards the front, the tunnel thrusters will increase the vessel's resistance to forward motion through the water, due to drag caused by the rear edge of the tunnel being wider than the front edge.

25

From KR 20110036148 A it is known to chamfer the tunnel edges but this solution is not very efficient. From JP 2011218959 A it is therefore known to provide injection nozzle along the front edge of the tunnel to inject water and thereby deflect the water flow across the bow thruster tunnel. But this system requires a dedicated injection 30 pump and complicated pipework.

2 DK 177448 B1

An object of the invention is therefore to provide for an advantageous technique for reducing drag generated by a bow thruster tunnel.

The invention 5 The invention provides for a moulding for mounting at the edge of a thruster tunnel of a boat. The moulding comprises a front surface formed to create a substantially laminar flow over the front surface, and wherein the height of the moulding decreases from a middle area of the moulding towards both sides of the moulding.

10 Forming the moulding with a front surface that creates a substantially laminar flow of water over the front surface is advantageous in that the water flow hereby is deflected so it does not hit the back edge of the tunnel and creates drag. However, no matter how streamlined the moulding is formed it will at least to some extent create drag itself and to reduce this it is advantageous that the height of the moulding 15 decreases from the middle area towards both sides of the moulding so that the moulding is highest where the drag problem is the greatest and then decreases as the problem is reduced.

It should also be noted that forming the moulding as a separate part attached to the 20 hull of the sea vessel is advantageous in that the moulding can be manufactured at a separate and specialised plant hereby reducing cost and labour. And if the ship ever collides with anything the moulding could get ripped off but it would be easy and inexpensive to reconnect it or even replace it - at least compared to repairing the bow thruster tunnel or the hull.

25

By the term “boat” is to be understood any kind of ship, liner, dinghy, yawl, skiff, cruiser, submarine or any other form of seafaring vessel.

DK 177448 B1 3

In an aspect of the invention, said front surface is formed to create a laminar flow over said front surface by making the height of said moulding increase from a front edge of said moulding towards a back edge of said moulding.

5 Making the height of the moulding increase, in the direction of the flow of the water passing the moulding during normal use on a ship, is advantageous in that the moulding hereby is provided with a streamlined shape which will reduce the drag of the moulding.

10 In an aspect of the invention, said moulding is formed with an open shape and thus extending only along a tunnel front edge of said edge of said thruster tunnel or along a part of said tunnel front edge.

In an embodiment of the invention the moulding could extent all the way along the | 15 entire 180° long front edge of the tunnel and it could even extend a little along the back edge of the tunnel such as up to 10°, up to 20° or even up to 30° at both sides of the moulding hereby making the moulding extend a total 200°, 220° or 240° around the tunnel edge. However, in another embodiment of the invention the moulding could also be shorter than the entire 180° extend of the front edge of the tunnel. It 20 could e.g. only constitute 160°, 140° or even less of the extent of the front edge of the tunnel preferably symmetrically arranged.

The terms “front” and “back” does in this connection refer to the direction during normal forward travel of the boat. I.e. the front is the part of the edge facing the bow 25 end of the ship and the back is the part of the edge facing the stem end of the ship.

Forming the moulding with an open shape so it only extends along some of the tunnel edge is advantageous in that drag of the moulding is hereby reduced and in that material can be saved hereby reducing the cost of the moulding.

30 DK 177448 B1 4

In an aspect of the invention, said moulding is formed with a closed shape and thus extending along the entire edge of said bow thruster tunnel.

Forming the moulding so that it encircles the tunnel opening is advantageous in that 5 it enables that the moulding can be attached more securely to the hull of the ship, hereby extending the life of the moulding. Further it advantageous in that that profile or the back part of the moulding will further work to secure a laminar flow across the tunnel.

10 In an aspect of the invention, said moulding is formed by a flexible material such as natural or synthetic rubber.

Forming the moulding in a flexible material is advantageous in that it enables that the moulding easily can be formed to fit the shape of the hull along the edge of the ship.

15 Furthermore, a flexible material also reduces the risk of the moulding or the hull being damaged in case of a collision.

In an aspect of the invention, a metal strip is incorporated in said moulding.

20 Incorporating a metal strip in the moulding, either in the surface of the moulding -preferably the bottom surface of the moulding - or fully enclosed inside the moulding is advantageous, in that it enables that the moulding can be permanently deformed into a specific shape before being mounted in the ship hull. This will simplify the fitting process. Furthermore, the metal strip will increase the strength of 25 the moulding. The metal strip may be produced from a soft plate that will make the moulding pliable to the shape of a particular hull for easy of mounting.

It should be noted that by the term “metal strip” is to be understood any kind of rod, stick, wire, plate or other suited for the above mentioned purposes.

30 5 DK 177448 B1

In an aspect of the invention, said metal strip comprises connection holes for connecting said moulding to a hull of said boat.

A metal strip enables secure fixation and it is therefore advantageous to provide the 5 metal strip with connection holes.

In an aspect of the invention, said moulding is provided with a substantially flat bottom surface. Optionally with grooves intended to secure fastening adhesive or other means of fastening to the hull with or without the added support by other 10 mechanical connecting means.

Providing the moulding with a substantially flat bottom surface is advantageous in that it enables secure connection to the ship hull.

15 In an aspect of the invention, a back surface of said moulding extends substantially perpendicularly from said bottom surface.

Making the back surface of the moulding extent substantially perpendicularly from the bottom surface of the moulding and thereby from the hull surface is advantageous 20 in that it provides for an efficient flow separation of the moulding, hereby reducing the creation of turbulence and thereby reducing drag.

The invention Anther provides for the use of a moulding according to any of the preceding claims for deflecting water flow across a bow thruster tunnel of a boat.

25

Using the above mentioned moulding for deflecting the water flowing across a thruster tunnel of a boat is advantageous in that given the shape of the moulding it will reduce the drag of the tunnel and it will protect the tunnel edge against collisions which is advantageous in that the moulding is much easier and cheaper to replace 30 that having to repair the hull, the tunnel or the tunnel edge.

DK 177448 B1 6

Figures

The invention will be described in the following with reference to the figures in which 5 fig· 1 · illustrates the water flow across a cross section through a known thruster tunnel, as seen from above, fig- 2 illustrates the water flow across a cross section through a 10 thruster tunnel comprising a moulding according to the present invention, as seen from above, fig. 3 illustrates a half moon shaped moulding mounted on the front edge of a thruster tunnel, as seen from the side, 15 fig- 4 illustrates a moulding encircling a bow thruster tunnel, as seen from the side, with a metal strip visible, fig. 5 illustrates a cross section through a first embodiment of a 20 moulding, as seen from the top, fig. 6 illustrates a cross section through a second embodiment of a moulding, as seen from the top, 25 fig. 7 illustrates a cross section through a third embodiment of a moulding, as seen from the top, and fig. 8 illustrates a cross section through a fourth embodiment of a moulding, as seen from the top.

30 7 DK 177448 B1

Detailed description

Fig. 1 illustrates the water flow across a cross section through a known bow thruster tunnel 2, as seen from above.

5 In this illustration only a section of the boat 3 is shown. The illustrated section is part of the bow of a ship 3 comprising a transverse bow thruster tunnel 2 extending from one side surface to the other side surface enabling that water can be moved from one side of the ship 3 to the other though the tunnel 2 by means of e.g. a propeller (not shown) arranged in the tunnel 2.

10

As illustrated by the arrow, the water flowing along the hull of a boat 3 traveling forward during normal operation will tend to hit the rear edge of the tunnel 2 hereby creating drag.

15 Fig. 2 illustrates the water flow across a cross section through a bow thruster tunnel 2 comprising a moulding 1 according to the present invention, as seen from above.

By providing the front edge 9 of the tunnel 2 with a moulding according to the present invention the water flow is deflected over the back edge of the tunnel 2 20 hereby reducing drag.

As illustrated the cylindrical shape of the bow thruster tunnel 2 and the tapering, hydrodynamic shape of the bow of a ship 3 entails that the back edge of the tunnel 2 extends “higher” than the front edge 9 at the present cross section which is 25 substantially horizontally through the centre of the tunnel 2. Thus, the “height” difference between the front edge 9 and the back edge - and thereby the drag problem decreases towards a vertical section through the tunnel 2.

8 DK 177448 B1

Therefore, the moulding 1 is advantageously shaped so that the height H of the moulding 1 decreases from the middle of the moulding 1 - through which the present cross section is made - and towards the sides 6 of the moulding 1.

5 In this embodiment of the invention the bottom surface 12 of the moulding is attached to the hull of the ship 3 by means of adhesive.

Fig. 3 illustrates a half moon shaped moulding 1 mounted on the front edge 9 of a bow thruster tunnel 2, as seen from the side.

10

As explained previously the drag problem of the tunnel 2 is greatest along a substantially horizontal line through the centre of the tunnel 2 and the water flow will therefore have to be deflected the most along this line. Thus, to ensure a stable laminar flow across the moulding 1, the width W of the moulding 1 is 15 advantageously greater at the middle area 5 than at the sides 6 of the moulding 1, hereby ensuring that the size of the moulding 1 decreases as the need for deflecting the water flow is decreased towards the sides 6. This reduces drag originating from the moulding 1 and reduces the size and cost of the moulding 1.

20 In this embodiment of the invention the moulding 1 is made from rubber but in another embodiment of the invention the moulding 1 could be made from another flexible material such as soft plastic or it could be made from a more rigid material such as hard plastic, metal, glass fiber reinforced resin or any combination thereof.

25 Fig. 4 illustrates a moulding 1 encircling a bow thruster tunnel 2, as seen from the side.

No matter how streamlined the moulding 1 is designed it will still extend from the otherwise smooth side surface of the ship 3 and will therefore by heavily strained by 30 the water flow and prone to collision. In this embodiment of the invention the 9 DK 177448 B1 moulding 1 therefore extends all the way around the tunnel 2 opening to ensure _ large contact surface - and thereby strong adhesion - when the moulding 1 is connected to the hull by means of adhesives. Furthermore, this moulding design will also ensure that the entire tunnel edge is protected by the moulding 1.

5

In this embodiment of the invention the moulding 1 is made from a flexible material and is furthermore provided with a metal strip 10 to ensure that the flexible moulding can maintain a specific shape during mounting of the moulding 1 and afterwards.

10 In this embodiment of the invention the metal strip 10 is incorporated in the bottom surface 12 of the moulding 1 but in another construction the strip 10 could be integrated inside the moulding I.

In this embodiment of the invention the metal strip 10 is provided with a plurality of 15 connection holes 11 ensuring that the moulding 1 can be connected to the hull of the ship 3 by means of connection means such as bolts, screws, rivets or other. In this embodiment of the invention the connection holes 11 are holes enabling that the moulding 1 can be attached by means of connection means extending into or through the hull. In another embodiment the connection holes 11 could also be formed as 20 through bores.

In this embodiment of the invention the moulding 1 is attached to the ship 3 by means of both adhesive and the connection means engaging the connection holes 11 but in another embodiment the moulding 1 could be connected only by means of the 25 connection holes 11 or only by using an adhesive material.

Fig. 5-8 illustrate cross sections through four different embodiments of a moulding 1.

The moulding 1 can comprise a multitude of more or less complex combination of different surface contours and the present embodiments disclosed in figs. 5-8 are 30 only a fraction of the possible embodiments and the contour of the front surface 4 of 10 DK 177448 B1 the different moulding embodiments can be combined with other of the disclosed back surfaces 13 of the mouldings 1.

Preferably the back surface 13 extends substantially perpendicular from the bottom 5 surface 12 as shown in figs. 5-8 and the height H of the front surface 4 is gradually increasing from the front edge 7 towards the back edge 8 to create a substantial laminar flow of the water past the moulding 1 in that the water flowing past the moulding 1 will gradually be deflected away from the hull surface and over the back edge of the underlying tunnel 2. Preferably the choise of section profile will be 10 designed not to inflict on the performance of the thruster.

The invention has been exemplified above with reference to specific examples of mouldings 1, bow thruster tunnels 2, boats 3 and other. However, it should be understood that the invention is not limited to the particular examples described 15 above but may be designed and altered in a multitude of varieties within the scope of the invention as specified in the claims.

DK 177448 B1 η

List 1. Moulding 2. Bow thruster tunnel 5 3. Boat 4. Front surface of moulding 5. Middle area o f moulding 6. Side of moulding 7. Front edge of moulding 10 8. Back edge of moulding 9. Tunnel front edge 10. Metal strip 11. Connection holes 12. Bottom surface of moulding 15 13. Back surface of mouldi ng H. Height W. Width w..

Claims

A bow thruster tunnel profile strip (1) for mounting at the edge of a bow thruster tunnel (2) by a boat (3), said profile strip (1) comprising a front surface (4) designed to create a substantially laminar flow above said front face (4), and the height (H) of profile list (1) decreases from a middle region (5) of said profile list (1) in the direction of both sides (6) of said profile list (1).

A profile strip (1) according to claim 1, wherein the front surface (4) is designed to create a laminar flow over said front surface (4) by increasing the height (H) of the profile strip (1) from a leading edge (7) of said profile list (1) against a trailing edge (8) of said profile list (1).

A profile strip (1) according to claim 1 or 2, wherein said profile strip (1) is formed with an open shape and thus extends only along a front edge (9) of said arch of said bow thruster tunnel (2) or along a portion of said tunnel leading edge (9).

The profile strip (1) according to any one of the preceding claims, wherein the profile strip (1) is formed in a closed form and thus extends along the entire edge of said bow thruster tunnel (2).

A profile molding (1) according to any of the preceding claims, wherein the molding molding (1) is formed of a flexible material such as natural or synthetic rubber.

A profile list (1) according to any one of the preceding claims, wherein a metal strip (10) is incorporated into said profile list (1).

A profile strip (1) according to claim 6, wherein said metal strip (10) comprises connecting holes (11) for connecting the profile strip (1) to a hull of said boat (3). 30 2 DK 177448 B1

A profile list (1) according to any one of the preceding claims, wherein the profile list (1) is provided with a substantially flat bottom surface (12).

A profile strip (1) according to claim 8, wherein a rear surface (13) of said profile strip (1) 5 extends substantially perpendicular from said bottom surface (12).

Use of a profile list (1) according to any of the preceding claims for deflecting the flow of water over a bow thruster tunnel (2) by a seagoing vessel (3).