High performance rudder for ships

A high performance full spade rudder for ships includes a rudder blade, a rudder trunk and a rudder post. The rudder blade widens from the leading edge to a central area which constitutes the widest point of the rudder profile. The rudder blade profile tapers from the central area to a narrow rear area and widens again from the rear area to the trailing edge. A bearing is placed in an inner longitudinal bore of the rudder trunk for bearing the rudder post, wherein the bearing penetrates with its free end into a recess, taper or the like in the rudder blade. No bearing is provided between the rudder blade and the rudder trunk. The bearing for the rudder post is placed in the rudder trunk in the area of the free end of the rudder trunk.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a high performance rudder for ships which is configured as a fully balanced or respectively a full spade rudder and has a rudder blade, a rudder trunk and a rudder post, wherein the rudder blade comprises a leading edge and a trailing edge.

2. Description of the Related Art

Such rudders are known from the prior art. When mounted in a ship, the rudder is normally placed behind a propeller provided on the hull of the ship with respect to the direction of motion of the ship, wherein the leading edge of the rudder blade is turned to the propeller and the trailing edge is turned away from the propeller. When mounted, the leading edge and the trailing edge are normally oriented substantially vertically.

High performance rudders, also known as high lift rudders, are rudders which generate a high dynamic lift and thus have a particularly good rudder effect. In particular, rudders which have a K2-factor of 1.4 or higher are considered to be high performance rudders. The rate of this K2-factor depends particularly on the form of the profile. The K2-factor is a factor which is used for determining the rudder power according to the following formula:
CR=132·A·v2·K1·K2·K3·Kt[N]v=speedK1=factor depending on the side ratio of the rudder surfaceK2=factor depending on the type of the rudder profileK3=factor depending on the rudder arrangementK4=factor depending on thrust loading factor

For the purposes of this invention, the term “rigid rudder” is to be understood to denote a rudder blade which consists of a single rigid body and which has no actuatable or movable parts such as for example an actuatable fin or the like.

SUMMARY OF THE INVENTION

The object of this invention is to provide a high performance rudder of the type mentioned above for which good maneuverability properties can be achieved with a rigid rudder blade without movable parts, and which can simultaneously be subject to high stresses, in particular to bending moments, and which can thus also be used for very big ships.

This object is achieved with a high performance rudder of the type mentioned above which in the introduction has in a cross-sectional view a rudder blade profile which widens from the preferably rounded-off configured leading edge in rudder longitudinal direction to a central area, which constitutes the widest point of the rudder profile, with a first flank angle, which tapers from the central area to a rear area, which constitutes the narrowest point of the rudder profile, with a second flank angle, and which widens again in particular as a fishtail from the rear area to the preferably straight-lined configured trailing edge. Moreover, the rudder trunk of the rudder is provided as a cantilever with a central inner longitudinal bore for receiving the rudder post and is configured penetrating into the rudder blade, wherein a bearing is placed in the inner longitudinal bore of the rudder trunk for bearing the rudder post, the bearing penetrating with its free end into a recess, taper or the like in the rudder post, wherein the rudder post is guided with an end area out of the rudder trunk and is connected with this end area with the rudder blade, wherein no bearing is provided between the rudder blade and the rudder trunk and wherein the inner bearing for bearing the rudder post is placed in the rudder trunk in the area of the free end of the rudder trunk. Correspondingly, the invention consists of the cooperation of a particularly configured rudder profile with a special rudder bearing arrangement. Due to the specially configured rudder profile, the flow and maneuverability properties of the high performance rudder are greatly improved. First, the preferably rounded-off configured front leading edge guarantees that there are good flow properties for the leading edge for all rudder positions or angles. Due to the fishtail-type extension from the rear area to the preferably straight-lined configured rear trailing edge and due to the widening of this area respectively, the flow is accelerated even more in this area and the lift is increased even more in the rear area of the rudder. On the whole, due to the special configuration of the profile, the directional stability, due to a reduction of crabbing, as well as the ship control properties are considerably improved. With the rudder according to the invention, rudder angles up to respectively 70° to the starboard and to the port side are possible. Besides a straight-lined configuration, the trailing edge can also be configured convex or even multiple convex, for example bi-convex.

Due to the special bearing arrangement for this rudder profile, there results the advantage that the rudder trunk penetrates into the rudder blade and the rudder post is positioned in the end area of the rudder trunk in a taper or the like of the rudder blade by means of a bearing. No further bearing of the rudder blade is necessary on the outer wall surface of the rudder trunk. Thus, the lower main bearing, also called neck bearing, can be positioned in the vicinity of the lift centre of the rudder and not, as is the case for conventional bearing arrangements, above the rudder blade. The stresses and bending moments which act onto the rudder blade are thus considerably reduced. In particular, contrary to conventional rudders, no bending moments or only slight ones act onto the rudder post since it is supported in its lower area introduced in the rudder blade in the rudder trunk. Due to this, the circumference of the rudder post as well as the width of the rudder blade itself can have smaller dimensions than conventional high performance rudders. Consequently, rudder constructions of the high performance rudder according to the invention are also possible for very big ships, i.e. with very big dimensions. Moreover, the production costs are thus reduced compared to conventional rudders since less material is used. The reduction of the rudder width is particularly advantageous for rudders with the profile according to the invention since they have, due to their profile shape, increased lift forces which act onto the rudder blade so that the rudder blade must be dimensioned anyway thicker or wider than this is the case for rudders with other profiles and they have thus a relatively high drag which is reduced due to the reduction of the rudder width. Therefore, a use of such profiled rudders would not be possible for big ships without the bearing arrangement according to the invention.

According to a preferred embodiment of the invention, the rudder according to the invention is provided in a ship which comprises a propeller assigned to the rudder and placed on a drivable propeller spindle. Furthermore, the connection of the rudder post with the rudder blade is disposed above the propeller spindle middle. This being, it is advantageous that, for replacing the propeller spindle, the rudder post does not need to be removed out of the rudder trunk after having taken off the rudder blade, since the connection of the rudder post with the rudder blade is situated above the propeller spindle middle and the rudder post is connected in its end area with the rudder post, in particular by means of a press-fit.

Furthermore, it can be appropriate to configure the rudder profile symmetrical so that there are the same lift conditions on the starboard side as well as on the port side. Such an embodiment is advantageous for the course keeping characteristics of a ship.

In a further preferred embodiment, the trailing edge which is, when mounted, normally turned away from the ship propeller, has two superimposed trailing edge sections which are placed laterally offset to each other. The indication that the trailing edge sections are placed superimposed refers to the mounted state of the rudder blade in which usually a section is placed above the other. Generally speaking, both trailing edge sections are thus placed adjacent to each other. Preferably, they are separated by a separation line or plane which extends substantially horizontally, when the rudder is mounted. Due to the offset arrangement, the one trailing edge section is offset to the port or starboard side and the other trailing edge section to the starboard or port side. Thus, an offset surface is respectively created on each trailing edge section in the area in which both trailing edge sections are adjacent to each other, this offset surface normally protruding or projecting laterally respectively over the other trailing edge section. The configuration of this embodiment results in a (90°) edge on each side in the transition area between the two trailing edge sections which runs into one of the offset surfaces. A further (90°) edge is created on the inner side of the offset surfaces.

In a further embodiment, a transition area which constitutes a continuous transition between the two offset trailing edge sections can be provided between the two trailing edge sections so that no offset surface or edge or the like is produced. Due to the offset or twisted arrangement of the trailing edge sections, the sections adapt themselves to the spin produced by the propeller so that an energy recuperation can be achieved which results in a reduction of the fuel consumption with a constant power output.

Particularly preferably for this embodiment the trailing edge sections are configured in a cross-sectional view with the shape of a half, longitudinally divided fishtail. This being, the tip of the fishtail of the one trailing edge section projects to the port side and of the other trailing edge section to the starboard side. In other words, both fishtail sections are disposed mirror-inverted in a top view onto the rudder profile. A particularly high energy recuperation can be achieved by such a configuration.

Tests of the applicant showed that it is particularly advantageous if the first flank angle is from 5° to 25°, preferably from 10° to 20°, particularly preferably from 12° to 16°. This configuration results in a particularly streamlined profile of the rudder blade which positively influences the lift of the rudder. In conventional rudders, the first flank angles are considerably greater than those of this very invention since the rudder blade body must be wider in order to be able to absorb the occurring loads, in particular for big ships. Due to the configuration of the high performance rudder according to the invention, such a wide embodiment is not necessary and smaller flank angles which result in a thinner rudder blade can be used.

According to a further preferred embodiment, the second flank angle is from 5° to 17°, preferably from 8° to 13°, particularly preferably 11°. In a similar manner as for the first flank angle, the second flank angle for this very invention can also be flatter or smaller than for conventional comparable rudders known from the prior art.

Preferably, the width ratio of the width of the trailing edge to the width of the central area is from 0.3 to 0.5, preferably from 0.35 to 0.45, particularly preferably from 0.38 to 0.43. The central area characterizes the widest or the thickest area of the rudder profile. Due to the rudder bearing arrangement according to the invention, it is possible to achieve such width ratios between the widest spot and the width of the rear trailing edge. For rudders known from the prior art, the width ratios are considerably smaller, i.e. the central and widest area of the rudder profile is, for prior art rudders, considerably bigger compared to the width of the rear trailing edge. This is due to the fact that for prior art rudders the rudder post must be configured extremely wide and the rudder blade must be reinforced in order to be able to absorb the loads acting thereon, in particular for big rudders for big ships since the rudder trunk does not penetrate into the rudder blade and thus substantially bigger loads act onto the rudder post. This is why, for rudders known from the prior art, maximal width ratios of 0.25 are possible (see for example DE 2 303 299 A1), which increases the material required and thus the manufacturing costs. Moreover, the drag of these rudders is higher.

Moreover, the length ratio of the distance from the rudder post middle to the front leading edge with respect to the overall length of the rudder is from 0.25 to 0.45, preferably from 0.35 to 0.43, particularly preferably from 0.38 to 0.42. Such an arrangement of the rudder post with respect to the overall length of the rudder improves globally the flow profile of the rudder. In particular a ratio of 0.4 results in a particularly optimal flow balancing of the rudder. Moreover, the rudder post is placed preferably in the central area of the rudder, i.e. at its widest or thickest spot. Thus, the pivotal point of the rudder is situated in the central area, i.e. in the area of the biggest profile thickness. Such an arrangement is only possible due to the special slim profile configuration in connection with the special rudder bearing arrangement according to the invention. Due to the arrangement of the rudder post in the area of the biggest profile thickness, it is possible to guide the rudder trunk and the rudder post into the rudder blade.

According to a further preferred embodiment of the invention, the ratio of the propeller diameter to the height of the rudder blade is from 0.8 to 0.95, preferably from 0.82 to 0.9, particularly preferably from 0.85 to 0.87. Thus, it is guaranteed that the propeller jet can flow against the whole profile of the rudder blade and that thus a maximal lift is achieved. Due to the configuration according to the invention, it is possible to provide comparatively high rudder blades since the bearing takes place inside the rudder blade and the bending moment loads are thus much lower compared to rudder blades that are supported further above. Insofar the height of the rudder blade can be bigger than for rudders known from the prior art.

Preferably, the rudder profile has a substantially straight-lined or a substantially convex curved course between the central area (the widest spot of the rudder profile) and the rear are (the narrowest spot of the rudder profile). In this way an optimal conformation can be achieved with respect to the flow properties of the rudder.

DETAILED DESCRIPTION OF THE INVENTION

InFIGS. 1 and 2a, a rudder arrangement which comprises a rudder100with a rudder blade10and a propeller30is illustrated. The propeller30is connected with the hull of a ship (which is not depicted here).40designates a rudder post and50a rudder trunk surrounding the rudder post40. The propeller30is assigned to the rudder blade10. The rudder blade10is connected with the hull60of a ship by means of the rudder post40. The rudder blade10has a front leading edge13turned to the propeller30and a rear trailing edge18turned away from the propeller30.

The rudder blade10has a preferably cylindrical taper11. The taper11is formed to receive the free end51of the rudder trunk50.

The rudder trunk50is provided as a cantilever girder with a central inner longitudinal bore52for receiving the rudder post40for the rudder blade10so that it has approximately the shape of a tube. Moreover, the rudder trunk50is configured penetrating into the rudder blade10. In its inner longitudinal bore52, the rudder trunk50has a bearing53for bearing the rudder post40, wherein this bearing53is placed in the lower end area51of the rudder trunk50. The rudder post40is guided out of the rudder trunk50or out of the bearing53with its free end41. This free end41of the rudder post40which is projecting from the rudder trunk50is fixedly connected with the rudder blade10by means of a press-fit, wherein, however, a connection is provided here which makes possible a release of the rudder blade10from the rudder post40, when the propeller spindle has to be replaced. This being, the connection of the rudder post40with the rudder blade10in the area41is situated above the propeller spindle middle31(seeFIG. 1) so that for the removal of the propeller spindle only the rudder blade10has to be removed from the rudder post40while on the other hand an extraction of the rudder post40out of the rudder trunk50is not necessary since the free lower end51of the rudder trunk50as well as the free lower end41of the rudder post40are situated above the propeller spindle middle31. A lock nut42is provided for locking the assembly between the free end41of the rudder post40and the rudder blade10. The area of the rudder blade10which surrounds the free end41is configured as a forged piece made of wrought iron and is also designated as a “hub”.

For this embodiment shown inFIGS. 1 and 2a, only a single inner bearing53is provided for the bearing of the rudder post40in the rudder trunk50; there is no further bearing for the rudder blade10on the outer wall of the rudder trunk50.

FIG. 2bshows the profile of the rudder blade10along an intersection line12. It can clearly be recognized that the rudder blade10in the profile view has a rounded off front leading edge13. From the leading edge13, the profile of the rudder blade10widens with a first flank angle α to a central area14which constitutes the widest point of the profile or of the rudder blade10. The first flank angle α is constituted by a tangent15on the widening area between the front leading edge13and the central area14and the intersection line12, wherein the latter simultaneously constitutes the longitudinal axis of the profile of the rudder blade10. From the central area13, the profile of the rudder blade10tapers again to a rear area16which constitutes the narrowest point of the rudder profile. The taper takes places with a second flank angle β which is formed by a tangent17and the intersection plane12. From the rear area16, the profile widens again to its end which is formed by a rear trailing edge18which is configured straight-lined. In this very case, this widening is configured on both sides in a central area with respect to the rudder blade height so that the rudder profile widens like a fishtail. In the upper and lower area of the rudder blade, the widening is configured on one side which results in half a fishtail. The one widening is provided on the port side and the other widening on the starboard side. Basically the widening can also be configured like a fishtail or one-sided like half a fishtail over the whole rudder blade height.

FIG. 4ashows a perspective view of a rudder profile which corresponds to the profile of the rudder ofFIGS. 2aand2b. Accordingly, the cross-sectional views ofFIG. 4acoincide with the cross-sectional view ofFIG. 2b. As can be recognized fromFIG. 4a, the rudder blade10is configured twisted in its rear area, i.e. the trailing edge18is divided into two trailing edge sections18a,18bwhich are placed superimposed. Both trailing edge sections18a,18bhave approximately the same length and are divided by a horizontally extending separating line or separating plane placed in the middle of the rudder blade10. They are placed offset to each other, wherein the upper trailing edge section18ais offset to the port side, this being considered in the direction of motion of the ship, and the lower trailing edge section18bto the starboard side. This results in a port-sided widening18awith the shape of a half fishtail in the end area of the rudder blade in the upper cross-sectional view and a mirror-inverted starboard-sided widening18bin the lower cross-sectional view. In the central cross-sectional view, both half fishtail-shaped trailing edge sections18a,18bare represented superimposed and thus constitute, put together, a full fishtail. Due to the offset arrangement of the trailing edge sections18a,18bto each other, an offset surface19in the area in which both trailing edge sections18a,18bare adjacent to each other is formed on each side of the rudder blade. The offset surface19is formed by the area of the upper edge area of the trailing edge section18bor of the lower edge area of the trailing edge section18awhich protrudes laterally.

FIG. 4bshows a similar embodiment of a rudder profile with two trailing edge sections18a,18bwhich are also placed offset to each other, wherein a transition area20is provided between these two trailing edge sections18a,18b. This transition area20extends obliquely with respect to a vertical axis and connects both trailing edge sections18a,18bwith each other so that a continuous transition without edges or offset surfaces or the like is created. Thus, also a closed flow profile is formed in the area of the trailing edge18. The cross-sectional views of the rudder profile ofFIG. 4bare similar to those ofFIG. 4aorFIG. 2b.

FIG. 4cshows a further perspective view of a further rudder profile. For this rudder profile, the trailing edge18is configured continuous, i.e. it does not have any sections which are offset to each other. Accordingly, a fishtail-like widening from the rear area16to the trailing edge18in the upper area as well as in the lower area is recognizable from the cross-sectional views of this profile. Basically the course of the profiles fromFIG. 4ato4cis similar to the course fromFIG. 2bwith respect to the widening of the profile with a first flank angle α and the taper of the profile with a second flank angle β.

FIG. 3ashows schematically a rudder blade10of a full spade or also called fully balanced rudder from the prior art. This rudder blade10is connected with a rudder post40with the hull of a ship (which is not illustrated here), wherein the rudder post40is fixedly connected in the upper area of the rudder blade10with the rudder blade. The rudder post40is positioned with a first upper bearing70and a second lower bearing71, wherein the second lower bearing is placed directly above the rudder blade10.

A full spade rudder with a rudder blade10according to this very invention is schematically illustrated inFIG. 3b, the rudder post40of which is positioned in its upper area with an upper bearing70and with a bearing53which is placed in the lower area of the rudder post in the rudder blade10. The rudder post40penetrates here into the rudder which is not the case with the prior art ofFIG. 3a. The rudder trunk is not depicted here for reasons of clarity. Thus, the lower bearing53of the rudder inFIG. 3bfor the embodiment according to the invention is placed closer to the lift centre of the rudder blade10than this is the case for the rudder of the prior art according toFIG. 3a. Accordingly, for the rudder ofFIG. 3b, there results another moment curve with respect to that ofFIG. 3a, wherein the calculation is based in both cases on an equally big constant uniform load as the stress acting on the rudder blade10. ForFIG. 3a, the maximal moment Mboccurs in the area of the upper bearing71while for the rudder according toFIG. 3bit occurs in the area of the lower bearing53which is disposed inside the rudder blade10. The maximum moment MbforFIG. 3bis also much lower than forFIG. 3a(approximately 50% less). This is due to the fact that the leverage with which the load pRacts onto the rudder blade10for the arrangement ofFIG. 3bis much lower than for the arrangement ofFIG. 3a. Thus, it is possible to use the rudder arrangement according toFIG. 3bfor much bigger ships than this is the case for the arrangement ofFIG. 3a.

FIG. 5shows respectively a half of two rudder profiles10,10′ which are placed above each other. The rudder profile10which is characterized with a thicker line corresponds to the profile of a rudder according to the invention while the profile10′ corresponds to a rudder as it is known from the prior art. The rudder profiles10,10′ are divided longitudinally by an intersection line12, wherein the intersection line12corresponds simultaneously to the longitudinal axis of the rudder profiles. The other halves of the rudder profiles10,10′ are configured mirror-inverted and are omitted for reasons of clarity. The illustration ofFIG. 5is only a schematic illustration for illustrating the differences between the profile according to the invention10and the profile10′ known by the prior art and is not made to correct scale.

The profile10according to the invention widens from the rounded off configured leading edge13in rudder longitudinal direction with a first flank angle α to a central area14. From there, the profile tapers again with a flank angle β to the rear area16. The rear area16constitutes the narrowest point of the rudder profile, whereas the central area14constitutes the widest point of the rudder profile. From the rear area16, the profile widens again with the shape of a fishtail to the trailing edge18. The rudder trunk50with the rudder post placed therein is provided in the central area14of the rudder profile. The pivotal point43of the rudder profile and the rudder post centre respectively is situated in the area of the thickest profile point14. The distance between the pivotal point or the thickest profile point and the front leading edge13is indicated by the letter “a” and corresponds to approximately 40% of the overall length of the rudder.

Contrary to this, the profile10′ known from the prior art widens from the leading edge13with a much bigger flank angle α′. Thus, the area of the thickest profile thickness14′ is much closer to the front leading edge13than it is the case for the profile10according to this very invention. The distance between the central area14′ of the profile10′ and the leading edge13is indicated by the letter b and corresponds to approximately 20% of the overall length of the rudder profile10′. The rudder profile10′ tapers from the central area14′ with a flank angle β′ to the rear area16, wherein the flank angle β′ is also bigger than the flank angle β. In the area between the central area14′ and the rear area16, the profile10′ forms a concave curve, whereas the profile course of the profile10is slightly convex between the central area14and the rear area16. Due to the configuration of the rudder profile10according to the invention, it is possible to provide a rudder trunk50which penetrates deeply into the rudder blade10. For the profile10′ known from the prior art, this would not be possible since there would not be enough space for the rudder trunk50in the area of the pivotal point43. Furthermore, the profile10′ is wider in its central area14′ than the profile10in its central area14so that there is a higher drag for the profile10′ than for the profile10.