WO1996007585A1

WO1996007585A1 - Improvements relating to ship's rudders

Info

Publication number: WO1996007585A1
Application number: PCT/GB1995/002044
Authority: WO
Inventors: Allan Bentley
Original assignee: Hamworthy Industramar Limited
Priority date: 1994-09-02
Filing date: 1995-08-30
Publication date: 1996-03-14
Also published as: AU3391795A; GB9417681D0

Abstract

A ship's rudder comprises a fixed streamlined support (1) to extend from the sternframe of a ship to about the level of a propeller shaft of the ship and a rudder blade (3) mounted on a rudder stock extending substantially normal to a keel of the ship and cooperating with a submerged bearing at the lower end of the support so as pivotally to mount the rudder blade (3) on the support (2), the rudder blade (3) having a streamlined symmetrical high lift profile, below the level of the support a front streamlined portion with a flank angle of at least 5° and up to about 15° and flanks (3a) forming tangents to the rudder stock, a tail portion in the form of a wedge (4) with a flank angle of at least 3° up to about 10° to act as a race stream deflector and a central streamlined portion fairing the front streamlined portion of the tail portion, the rudder stock and rudder pintle defining the pivot axis of the rudder and lying to the rear of the greatest thickness of the rudder profile.

Description

IMPROVEMENTS RELATTNO TO SHIP'S RUDDERS

The invention relates to ship's rudders.

Patent Specification GB-A-1 426 412 described a rudder for a boat, known as the Schilling rudder, which rudder departed radically from rudders which were known previously, particularly by having a pivot axis spaced rearwardly from a leading edge, by having a streamlined symmetrical high-lift profile, a front portion of which had a flank angle of about 15° and a tail portion of which had a flank angle of about 10°. Used either singly or in pairs in the race-stream of a propeller, such rudders on relatively small boats were very effective in enhancing manoeuvrability.

According to the invention a ship's rudder, for a ship having a stemframe, a propeller shaft and a keel, comprises a streamlined support to be provided integral with the stemframe and extending down to about the level of the propeller shaft and a rudder blade having a rudder stock extending substantially normal to the keel and a rudder pintle in alignment with the rudder stock to cooperate with a submerged bearing at the lower end of the support so as pivotally to mount the rudder blade on and with respect to the support, wherein the rudder blade has a streamlined symmetrical high-lift profile; below the level of the lower end of the support the rudder blade has a front streamlined portion with a flank angle of about 15° but in any event at least 5° and flanks forming tangents to the rudder stock; the rudder stock and the rudder pintle define the pivot axis of the rudder and lie to the rear of the greatest thickness of the rudder profile; and the rudder blade has a tail portion generally in the form of a wedge with a flank angle of about 10° but in any event at least 3° to act as a race-stream deflector and a central streamlined portion fairing the front streamlined portion to the tail portion.

Preferably above the level of the lower end of the support the rudder has flanks forming tangents to the rudder stock and a tail portion corresponding to the tail portion of the lower portion of the rudder blade.

Advantageously the rudder includes upper and lower deflection plates and a scissor plate. The scissor plate is provided at the junction of the support and the lower part of the rudder blade and acts or act in similar manner to end plates, that is to say to hold water flow onto the rudder blade and support thus preventing spillover from the pressure side and loss reduction of lateral turning force. Rudder angles can be up to 70° compared to conventional rudder angles of 35°.

The support is faired into the general rudder blade profile and section. The support reduces the forces acting on the main rudder stock, bearings and steering gear to permit a reduction in overall scantling requirements.

The support can be arranged to enable both the propeller and shaft to be drawn without hindrance.

A rudder according to the invention can have an effective hydrodynamic rudder angle in excess of that applied physically by the steering gear; a higher lift-side force component than a rudder of conventional section; can exhibit delay in the onset of rudder stall in conjunction with a higher lift-curve slope, can give improved course keeping with reduction or elimination of rudder hunting compared to other rudder forms; and can permit reduction of rudder stock diameter and consequent blade section thickness compared to a fully hung rudder of similar parameters, thus reducing rudder resistance/drag as a result of reduced blade thickness/chord length ratios.

Thus the invention permits an upsizing of a rudder of the kind shown in the specification of British Patent 1 426 412 (the Schilling rudder) from one suitable for inland or coastal shipping to ocean-going shipping. It permits the integration of a high-lift profile rudder into a very large vessel.

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

Figure 1 is a schematic perspective view from the forward port side of a ship's rudder according to the invention shown both in a mid-ships position and in a 45° position, up to 70° rudder angle can be achieved for the hard over position; Figure 2 is a side elevation of the rudder from the starboard side; Figure 3a is a plan view at the level HI of Figure 2 showing the rudder in the mid-ships position in full lines and in 70° hard over port position in dotted lines; Figure 3b is a view similar to Figure 3a but at level H5 of Figure 2; Figures 4a, 4b, 4c and 4d respectively show half sections of the symmetrical rudder blade of the rudder at levels HI, H3, H4 and H5 of Figure 2; Figures 5a, 5b and 5c respectively show the details of horizontal plates at levels H2, H4 and H5 of Figure 2;

Figure 6 shows a plan view for a mdder according to the invention illustrating angles and radii; and Figure 7 is a view corresponding to Figure 2 but showing the structural arrangement of the mdder.

Referring to the drawings a ship's mdder has a support or horn 1 the upper end of which will be mounted integrally on a ship's stemframe. Pivotally mounted on the support 1 about an axis 2, indicated in Figure 2, is a mdder blade 3. The mdder blade 3 has a streamlined high-lift profile with a divergent trailing edge 4, it also has a lower slipstream deflector plate 5, as shown in Figure 1, and upper slipstream deflecting plates 6, one on the port side and one on the starboard side. The support 1 has an upper slipstream deflector plate 7 around its forward edge. A scissor plate 9 is provided at the upper edge of the front part of the mdder blade 3. The mdder is intended to cooperate with a ship's propeller 10, shown in Figure

2, which is rotatable about an axis 11 with the lower edge of the propeller 10 generally corresponding to the level of the lower edge of the mdder blade 3.

It can be seen from Figures 3a and 3b that at an upper level HI indicated in Figure 2, the combined overall sectional shape of the support 1 and the mdder blade 3 in the mid-ships position is similar to that at the lower edge of the mdder blade 3 at level H5 indicated in Figure 2. Thus at the level H5 the mdder blade 3 has a forward streamlined portion with flanks 3a forming tangents to a mdder stock 3b_ around the pivot axis 2 and the divergent trailing edge tail portion 4. The portion between the flanks 3a and the tail portion 4 fairs the front streamlined portion into the tail portion.

Figures 4a to 4d show the particular dimensions and thus define the shape in section of a typically sized mdder blade 3 at the various levels HI to H5.

Figures 5a to 5c show respectively the dimensions of the upper slipstream deflector plate 6 and the support slipstream deflector plate 7, the scissor plate 9 and the lower slipstream deflector plate 5, again for a typical sized mdder.

The range of possible movement of the mdder can be seen from Figure 6. Figure 7 shows the skeleton of the mdder 3 with skin plates removed to show internal details. The skeleton comprises shaped horizontal plates 13 which define the shape of the mdder and vertical webs 14 to maintain the plates 13 in aligned spaced relation. The mdder stock 3b passes through a main bearing 16 in the stemframe 7 of the ship and has a downwardly projecting tapered portion 18 which is gripped by a hydraulic nut 19 of the mdder 3. A mdder pintle 20 is engaged from above into a submerged bearing 21 of the support 1 and a downwardly projecting tapered portion 22 is gripped by a hydraulic nut 23 of the mdder 3.

Claims

1. A ship's mdder, for a ship having a stemframe, a propeller shaft and a keel, comprising a streamlined support (1) to be provided integral with the stemframe and extending down to about the level of the propeller shaft and a mdder blade (3) having a mdder stock (3b_) extending substantially normal to the keel and a mdder pintle (20) in alignment with the mdder stock (3b_) to cooperate with a submerged bearing (19, 21) at the lower end of the support (1) so as pivotally to mount the mdder blade (3) on and with respect to the support (1), wherein the mdder blade (3) has a streamlined symmetrical high-lift profile; below the level of the lower end of the support (1) the mdder blade (3) has a front streamlined portion with a flank angle of about 15° but in any event at least 5° and flanks (3a) forming tangents to the mdder stock (15); the mdder stock (3b_) and the mdder pintle (20) define the pivot axis (2) of the mdder and lie to the rear of the greatest thickness of the mdder profile; and the mdder blade (3) has a tail portion (4) generally in the form of a wedge with a flank angle of about 10° but in any event at least 3° to act as a race-stream deflector and a central streamlined portion fairing the front streamlined portion to the tail portion (4).

2. A ship's mdder according to claim 1, wherein, above the level of the lower end of the support (1), the mdder has forward flanks (3a) forming tangents to the mdder stock (3h) and a tail portion (4) corresponding to the tail portion (4) of the lower portion of the mdder blade (3).

3. A ship's mdder according to claim 1 or claim 2, wherein the mdder includes upper and lower deflection plates (7, 5) and a scissor plate (9).

4. A ship's mdder according to claim 3, wherein the scissor plate (9) is provide at the junction of the support (1) and the lower part of the mdder blade (3) and acts in similar manner to an end plate (7, 5), that is to say to hold water flow onto the mdder blade (3) and the support (1) thus preventing spillover from the pressure side and loss reduction of lateral turning force.

5. A ship's mdder according t any one of claims 1 to 4, with a maximum angle of 70°.

6. A ship's mdder according to any one of claims 1 to 5, wherein the support is faired into the general mdder blade profile and section and thereby reduces the forces acting on the main mdder stock (3b), bearing (19, 21) and steering gear to permit a reduction in overall scantling requirements.

7. A ship's mdder according to any one of claims 1 to 6, wherein the support (1) is arranged to enable both the propeller (10) and shaft to be drawn without hindrance.