WO1998054052A1

WO1998054052A1 - Propulsion and steering arrangements of ships

Info

Publication number: WO1998054052A1
Application number: PCT/GB1998/001539
Authority: WO
Inventors: Allan Bentley
Original assignee: Hamworthy Marine Technology Ltd.
Priority date: 1997-05-28
Filing date: 1998-05-27
Publication date: 1998-12-03
Also published as: AU7665298A

Abstract

A ship with twin propellers (16, 17) is provided with twin Schilling rudders (2, 3) i.e. a respective rudder (2, 3) for each propeller (16, 17). Each rudder (2, 3) is pivotably mounted by a respective shaft (6, 7), has a bulbous nose portion (11), a waisted mid-portion (12) and a flared tail (13). The flared tail flares outwardly substantially only on the inner side of each rudder i.e. the side which faces the other rudder of the pair. Each rudder (2, 3) has an upper plate (14) and a lower plate with the plates much more extensive on the inner side than on the outer side, the plates being aligned with streamlines from the respective propeller (16, 17) and the lower plate having a downwardly angled portion on the inner side.

Description

PROPULSION AND STEERING ARRANGEMENTS OF SHIPS

The invention relates to propulsion and steering arrangements of ships. The Schilling rudder has been known for over twenty years, particularly from patent specification GB 1 519 243. This patent specification describes a rudder arrangement for a ship comprising two balanced rudders or two semi-balanced rudders (the distinguishing factor for a semi-balanced rudder being the inclusion of a rudder horn fixed to the ships hull) disposed in the propulsive current from a propeller or a respective propeller of the ship, the axis of rotation of the rudders being disposed at the same distance from and on opposite sides of a centreline of the propulsive current which occurs when the rudders are in a zero deflection position. Each of the rudders comprises a profiled element having a centreline extending in the zero deflection position parallel to the longitudinal axis of the ship, a cross section asymmetrical about the centreline and having a relatively wide streamlined nose portion and a relatively slim tail portion, the contour of the outer face of each profiled element, that is to say the face which in the zero deflection position is remote from the centreline of the propulsive current, contiguous with a convex length formed by the nose portion being concave such that, at the slim tail portion the contour of the outer face diverges rearwardly from the centreline of the profiled element at an angle of between 2 and 10 degrees of the contour of the inner face of each profiled element, that is to say the face which in the zero deflection position is adjacent the centreline of the propulsive current being, rearwardly of the nose portion, substantially rectilinear. Thus a Schilling rudder has a generally bulbous forward portion, a narrowed portion to the rear of the pivot axis and a slim tail portion the faces of which diverge.

Previous proposals for use of Schilling rudders have comprised either two rudders in the propulsive current of a single propeller or two rudders in each of the propulsive currents from twin propellers, an arrangement common in cruise and ferry ship sectors. It has also been proposed on twin rudder single propeller ships that the twin rudders should not be symmetrical but rather that the waisting and the tail section be reduced on the inner facing side of each rudder, that is to say on each of the two facing sides of a pair of rudders.

According to the invention there is provided a propulsion and steering arrangement of a ship comprising two propellers arranged side-by-side at the stern of the ship and a respective rudder for each propeller, the rudders each having a bulbous forward portion, in which bulbous portion a pivot arrangement is provided; a waisted portion to the rear of the pivot arrangement; and a fish tail at the rear end provided only on the inner side of the rudder that is to say the side thereof adjacent the other rudder, each rudder having a top plate and a bottom plate, such top and bottom plates being handed so that at least at the tail section of the rudder they are more extensive at the inner side than at the outer side, the top and bottom plates are generally aligned with the flow streamlines from the respective propellers and each rudder is rotated through a small angle about a rudder stock centreline by which it is pivoted with the trailing edge turned inboard to align the rudder at a neutral angle.

The top plates may be spaced downwardly from the uppermost extremities of the rudders on which they are provided.

Each rudder may include intermediate plates handed so that at least at the tail section of the rudder they are more extensive at the inner side than at the outer side, generally aligned with the flow streamlines and positioned around the uppermost position of the propeller blade tips, and/or one positioned generally in line with the bottom of a rudder horn of the ship's hull.

Thus the ship may have twin propulsion means comprising twin engines, twin screws and a twin rudder arrangement provided as a mechanism to introduce built-in redundancy in the ship design. Such redundancy is intended to mitigate the loss of main engine power, which may be catastrophic for a single screw vessel. The ship may incorporate a centreline bulkhead totally to separate the main machinery spaces into a port engine room and a starboard engine room. This design feature can enhance the safety of the vessel, its crew and contents and essentially provides a propulsion fallback position.

Twin screw design can also provide an inherent increase in manoeuvrability. By using the twin Schilling rudders, performance at slow speed can be significantly improved and can include dynamic positioning. High lift Schilling rudders provided in one piece can provide simple, reliable, yet highly effective means for direction control.

Providing the fish tail only on the inner side of each of the rudders can reflect established ship operational procedures. Handing the top and bottom rudder plates by reducing drag can reduce impact upon the ships propulsive efficiency.

Aligning the top and bottom plates with the flow streamlines can optimize the spacial position of the top and bottom plates. Particularly the top and bottom plates can be aligned at a pitch angle to match the flow streamlines behind the moving hull and rotating propeller. A similar alignment can be applied to the intermediate plates if provided. The effect of the rudders upon the propulsive efficiency of the ship, can be minimized by rotating the port and starboard rudders through a small angle about the rudder stock centreline with the trailing edge turned inboard. The angle may for example be two degrees.

The invention is diagrammatically illustrated by way of example in the accompanying drawings, in which:

Figure 1 is a schematic view from the stern of a pair of rudders and propulsion means of a first embodiment of a propulsion and steering arrangement of a ship according to the invention;

Figure 2 is a plan view of the twin rudders of Figure 1 ; Figure 3 is a side view corresponding to Figure 1 and showing schematically the propulsion means also;

Figure 4 is an enlarged view corresponding to Figure 3 showing the starboard rudder of a pair of rudders of a second embodiment of a propulsion and steering arrangement according to the invention; Figure 5 is a plan view corresponding to Figure 4;

Figure 6 is a sectional view on line VI- VI of Figure 4;

Figure 7 is a view from the rear of the rudder of Figure 4;

Figure 8 is a schematic view from the stern of a pair of rudders and propulsion means of a third embodiment of a propulsion and steering arrangement for a ship according to the invention;

Figure 9 is a plan view of the twin rudders of Figure 8; Figure 10 is a side view corresponding to Figure 8 and showing schematically the propulsion means also;

Figure 11 is an enlarged view corresponding to Figure 10 showing the starboard rudder of a pair of rudders of a fourth embodiment of a propulsion and steering arrangement according to the invention;

Figure 12 is a plan view corresponding to Figure 11;

Figure 13 is a sectional view on line XIII-XIII of Figure 11;

Figure 14 is a view from the rear of the rudder of Figure 11 ;

Figure 15 is a schematic view from the stern of a pair of rudders and propulsion means of a fifth embodiment of a propulsion and steering arrangement for a ship according to the invention;

Figure 16 is a plan view of the twin rudders of Figure 15;

Figure 17 is a side view corresponding to Figure 15 and showing schematically the propulsion means also; Figure 18 is an enlarged view corresponding to Figure 17 showing the starboard rudder of a pair of rudders of a sixth embodiment of a propulsion and steering arrangement according to the invention;

Figure 19 is a plan view corresponding to Figure 18;

Figure 20 is a sectional view on line XX-XX of Figure 18; and Figure 21 is a view from the rear of the rudder of Figure 18.

Referring to the drawings, the hull 1 of a ship mounts a port rudder 2 and a starboard rudder 3 each by means of spaced bearings 4 and 5 which mount respective shafts 6 and 7 for the rudders 2 and 3 , each of these shafts 6 and 7 being secured to the respective rudder 2, 3 by hydraulic nuts with only the nut 7a being shown, and projecting into a steerage flat 8 in which means 9 and 10 are provided for rotating the shafts 6 and 7 respectively. Each of the rudders 2,3 cooperates with a respective one of twin propellers 16, 17, the rudder being positioned within the propeller slipstream.

As can be seen in Figure 2 and in more detail in Figures 4 to 6, the rudder

3 is handed and is a Schilling rudder, that is to say it comprises a forward bulbous nose portion 11, a waisted mid-portion 12 and a flared tail 13. The rudder 3 shown is the starboard rudder, the port rudder 2 is oppositely handed but otherwise identical. It will be seen that the flared tail portion 13 flares outwardly substantially only on the side of the rudder which faces towards the other rudder of the pair, that is to say on its inner side.

The rudder 3 has an upper plate 14 and a lower plate 15. As can be seen from Figures 1 , 2, 5 and 6, the plates 14 and 15 are provided to be much more extensive on the inner side of the rudder 3 than on the outer side and further the planes of the plates 14 and 15 are aligned with the streamlines from the respective propeller 17 shown in Figure 3. Further the lower plate 15 has a downwardly angled portion 15a on the inner side of the rudder 3. Referring to Figures 8 to 14 of the drawings, the hull 21 of a ship mounts a port rudder 22 and a starboard rudder 23 each by means of single and/or multiple bearings 24 and/or 25 which mount respective shafts 26 and 27 for the rudders 22 and 23, each of these shafts 26 and 27 being secured to the respective rudder 22, 23 by hydraulic nuts with only the nut 27a being shown, and projecting into a steering flat 28 in which means 29 and 30 are provided for rotating the shafts 26 and 27 respectively. Each of the rudders 22, 23 cooperates with a respective one of twin propellers 36,37, the rudder being positioned within the propeller slipstream.

As can be seen in Figure 9 and in more detail in Figures 11 to 13, the rudder 23 is handed and is a Schilling rudder, that is to say it comprises a forward bulbous nose portion 31, a waisted mid-portion 32 and a flared tail 33. The rudder 23 shown is the starboard rudder, the port rudder 22 is oppositely handed but otherwise identical. It will be seen that the flared tail portion 33 flares outwardly substantially only on the side of the rudder which faces towards the other rudder of the pair, that is to say on its inner side. The rudder 23 has an upper plate 34 and a lower plate 35. As can be seen from Figures 8, 9, 12 and 13, the plates 34 and 35 are provided to be much more extensive on the inner side of the rudder 23 than on the outer side and further the planes of the plates 34 and 35 are aligned with the streamlines from the respective propeller 37 shown in Figure 10. Further the lower plate 35 has a downwardly angled portion 35a on the inner side of the rudder 23. Intermediate plates 40 can also be included generally aligned with the streamlines emanating from the respective propeller 37 uppermost tip position.

Referring to Figures 15 to 21 of the drawings, the hull 51 of a ship mounts a port rudder 52 and a starboard rudder 53 each by means of a single and/or multiple bearings 54 and/or 55 which mount respective shafts 56 and 57 for the rudders 52 and 53, each of these shafts 56 and 57 being secured to the respective rudder 52,53 by hydraulic nuts with only the nut 57a being shown, and projecting into a steering flat 58 in which means 59 and 60 are provided for rotating the shafts 56 and 57 respectively. In the case of a semi-balanced rudder an additional mount is effected by means of a bearing 69 located in the lower part of a fixed rudder horn 68 and pintle hinging. Each of the rudders 52, 53 co-operates with a respective one of twin propellers 66, 67, the rudder being positioned within the propeller slipstream.

The rudder 53 has an upper plate 64 and a lower plate 65. As can be seen from Figures 15, 16, 19 and 20, the plates 64 and 65 are provided to be much more extensive on the inner side of the rudder 53 than on the outer side and further the planes of the plates 64 and 65 are aligned with the streamlines from the respective propeller 67 shown in Figure 17. Further the lower plate 65 has a downwardly angled portion 65a on the inner side of the rudder 53. Intermediate plates 80 can also be included generally aligned with the streamlines emanating from the respective propeller 67 uppermost tip position. In the case of a semi-balanced rudder, an intermediate plate 81 can be included generally aligned with the bottom of the rudder horn 68.

Claims

1. A propulsion and steering arrangement of a ship comprising two propellers arranged side-by-side at the stern of the ship and a respective rudder for each propeller, the rudders each having a bulbous forward portion, in which bulbous portion a pivot arrangement is provided; a waisted portion to the rear of the pivot arrangement; and a fish tail at the rear end provided only on the inner side of the rudder that is to say the side thereof adjacent the other rudder, each rudder having a top plate and a bottom plate, such top and bottom plates being handed so that at least at the tail section of the rudder they are more extensive at the inner side than at the outer side, the top and bottom plates are generally aligned with the flow streamlines from the respective propellers and each rudder is rotated through a small angle about a rudder stock centreline by which it is pivoted with the trailing edge turned inboard to align the rudder at a neutral angle.

2. A propulsion and steering arrangement according to claim 1 , including, on each rudder, intermediate plates handed so that at least at the tail section of the rudder they are more extensive at the inner side than at the outer side, generally aligned with the flow streamlines and positioned around the uppermost position of the propeller blade tips.

3. A propulsion and steering arrangement according to claim 1 or claim 2, including, on each rudder, an intermediate plate positioned generally in line with the bottom of a rudder horn of the ship's hull.

4. A propulsion and steering arrangement according to any one of claims 1 to 3, in which the ship has twin engines with a centreline bulkhead totally to separate main machinery spaces into a port engine room and a starboard engine room.

5. A propulsion and steering arrangement according to claim 2 or claim 3, in which the intermediate plates are aligned at pitch angles to match flow streamlines behind the hull when moving and the propellers when rotating.

6. A propulsion and steering arrangement according to any one of claims 1 to 5, in which multiple bearings are provided for mounting each rudder.

7. A propulsion and steering arrangement according to any one of claims 1 to 6, in which each rudder is a spade rudder supported on multiple spaced bearings from a main shaft.

8. A propulsion and steering arrangement according to any one of claims 1 to 6, in which each rudder is a semi spade rudder supported on multiple bearings from a horn of the ship by pintle hinging.