Flap rudder and rudder system for watercraft

Abstract

In order to provide a rudder for watercraft, in particular ships, which has a flap and thus good manoeuvrability and at the same time can be designed with low strength such that the rudder can be produced at lower cost and with improved flow properties, a rudder (100) is proposed having a rudder blade (10), the rudder (100) having a flap (11) which is arranged pivotably on the rudder blade (10), wherein a maximum height (H2) of the flap (11) is less than a maximum height (H1) of the rudder blade (10), and wherein the flap (11) is arranged parallel to a rudder stock (22) of the rudder (100) with respect to a longitudinal extent (L) of the flap (11), the rudder blade having an upper rudder blade section (20) and a lower rudder blade section (21), characterized in that the upper rudder blade section (20) and the lower rudder blade section (21) are designed such that they have different lift coefficients, the lift coefficient of the upper rudder blade section (20) being greater than the lift coefficient of the lower rudder blade section (21).

Description

[0001] Fin rudders and rudder systems for watercraft

[0002] The present invention relates to a rudder for watercraft, in particular ships. Furthermore, the present invention relates to a rudder system.

[0003] State of the art

[0004] Watercraft, especially ships, have a rudder, usually located at the stern, to change direction. Particularly on medium-sized or large vessels, such as container ships, oil tankers, tugboats, ferries, large yachts, or passenger ships, the rudder is preferably a cantilever rudder. Cantilever rudders are characterized by having a solid rudder blade that is supported only in its upper portion. The rudder blade is attached to the hull via a rudder shaft, which typically extends into and is connected to the rudder blade.

[0005] On ships requiring high rudder force or excellent maneuverability, the rudder may be a so-called fin rudder. In such rudders, a fin is positioned at the trailing edge of the rudder blade, facing downstream, and this fin can pivot to allow for large rudder angles. The fin is often hinged to the rudder blade, meaning that when the rudder blade is deflected, the fin also deflects, with the deflection angle of the fin typically being greater than that of the rudder blade.

[0006] Compared to a rudder without fins, a fin rudder requires a significantly higher lift factor for the relevant rudder force when calculating its strength. The lift factor of a fin rudder can be as high as 1.7, while for a rudder without fins, a factor of only 1.1 is typically used. This higher lift factor necessitates that fin rudders be designed with considerably greater strength. To achieve this increased strength, for example, a greater rudder profile thickness is selected, or the rudder is constructed from solid materials and / or with correspondingly strong components. This is disadvantageous in terms of cost, and it also negatively impacts the rudder's performance and hydrodynamic characteristics, as the increased profile thickness can, for instance, generate greater drag.

[0007] Description of the invention: Problem, solution, advantages

[0008] The present invention aims to provide a rudder that incorporates a fin, thus offering good maneuverability, while simultaneously being designed with low strength, thereby reducing costs and improving flow characteristics. Furthermore, the present invention aims to provide a system comprising a first rudder and a second rudder, achieving the aforementioned advantages.

[0009] To solve the problem, a rudder for watercraft, in particular ships, is proposed, comprising a rudder blade, wherein the rudder has a fin which is pivotably arranged on the rudder blade. The maximum height of the fin is less than the maximum height of the rudder blade. The fin is arranged substantially parallel to a rudder shaft of the rudder with respect to its longitudinal extent. The rudder blade has an upper rudder blade section and a lower rudder blade section. The upper and lower rudder blade sections are designed such that they have different lift coefficients, with the lift coefficient of the upper rudder blade section being greater than the lift coefficient of the lower rudder blade section.

[0010] The lift coefficient is a dimensionless value representing the dynamic lift of the rudder blade in the respective rudder blade sections. The magnitude of the lift coefficient can be determined, in particular, by the shape of the rudder blade airfoil. For example, the rudder blade can have NACA airfoils in the upper and / or lower rudder blade sections, and the lift coefficient can be determined by the shape of the NACA airfoil.

[0011] Preferably, the rudder blade has asymmetrical rudder blade profiles with respect to the flow direction, particularly with respect to the profile chord, especially along its entire longitudinal extent.

[0012] The rudder blade profile is preferably formed in the area of ​​the rudder blade where the fin is arranged by the profile of the rudder blade and the profile of the fin.

[0013] The fin is arranged at the trailing edge of the rudder blade and pivotably attached to it. The trailing edge of the rudder blade is the rearmost end of the rudder blade when viewed in the direction of flow. In rudders without a fin, the trailing edge is usually straight. According to the present invention, the trailing edge can have different shapes, the shape of which generally depends on the design of the fin. Here, "direction of flow" refers to the undisturbed main flow direction along the longitudinal axis of the vessel when traveling straight ahead.

[0014] In a side view of the rudder blade, the trailing edge is preferably stepped and extends along the entire longitudinal extent of the rudder blade from a lower end to an upper end. The terms "top" and "bottom" refer to the installed state of the rudder blade on the watercraft. In particular, the rudder blade has exactly one continuous trailing edge, which preferably comprises differently shaped but continuous sections.

[0015] Due to the preferably stepped design of the trailing edge, the rudder blade preferably has an L-shape in a side view. The L-shape of the rudder blade is preferably achieved by a lower rudder blade section that is wider compared to the upper rudder blade section. The width refers to the shortest distance between the trailing edge and the leading edge of the rudder blade opposite the trailing edge in the respective rudder blade section. The width can be constant along the longitudinal extent of the respective rudder blade sections or it can change along the longitudinal extent, decreasing in each rudder blade section from the upper end to the lower end. However, the width in the upper rudder blade section is always smaller than the width in the lower rudder blade section at every position along the longitudinal extent of the rudder blade.

[0016] Preferably, the part of the rudder formed by the rudder blade and the fin is designed such that the rudder tapers downwards in its installed state. This is advantageous because only the area, particularly the upper part, of the rudder blade where the fin is located needs to be designed with higher strength, while lower strengths can be applied to the other, particularly the lower, part of the rudder. The rudder blade is preferably designed to follow the shape of the fin, so that the combined shape of the fin and the rudder blade, viewed from the side, resembles the shape of a rudder without a fin.

[0017] The differently sized rudder blade sections result in a stepped shape at the trailing edge of the rudder blade. In a side view of the rudder blade, the trailing edge is therefore not continuous or running along a straight line as with conventional rudder blades known from the prior art, but rather it is formed by three interconnected trailing edge sections, with the lowermost section being flush with the trailing edge of the fin in a side view.

[0018] The fin is preferably arranged in the uppermost section of the trailing edge of the rudder blade. A middle section of the trailing edge of the rudder blade preferably connects the lowermost and the uppermost sections of the trailing edge of the rudder blade.

[0019] The fin is preferably connected to the watercraft by means of a connection system to an upper part of the rudder in the area of ​​the rudder tube. The connection system preferably allows the fin to be rotatably or pivotably attached to the watercraft. Preferably, the connection system includes a steering mechanism by means of which the fin can be deflected. Preferably, the fin is articulated with respect to the rudder blade. Preferably, the fin is additionally connected to the rudder blade by means of a hinge system.

[0020] The height of the rudder blade or fin refers to the maximum height of the rudder blade or fin along its longitudinal axis in relation to the rudder's installed position on the vessel (the longitudinal axis then roughly corresponds to a vertical direction). In the installed state, the height is measured along this longitudinal axis. Specifically, the height refers to the maximum distance between two points on the respective upper and lower edges of the rudder blade or fin through which a vertical line passes. The height of the rudder blade and fin can therefore vary along the direction of the current. Preferably, the lower edge of the rudder blade and the lower edge of the fin, as well as the upper edge of the rudder blade and the upper edge of the fin, are arranged parallel to each other.Preferably, the fin has a square, or more preferably rectangular, shape when viewed from the side of the rudder. The shape of the fin can deviate slightly from the rectangular shape, for example, by having the shape of a parallelogram or a trapezoid.

[0021] The fin preferably extends from the upper edge of the rudder blade to approximately the height of the rudder blade through which the propeller axis of a propeller located in front of the ship passes. Preferably, the maximum width of the fin, viewed in the direction of flow, is about one quarter to one third of the maximum distance between the leading edge of the rudder blade and the trailing edge of the fin.

[0022] The rudder preferably has, with respect to its longitudinal extent (vertical direction), a first area or rudder blade section in which the fin is arranged, and a second area or rudder blade section in which no fin is arranged. When installed, the first area is preferably located above the second area. Because the fin extends only over a portion of the rudder, it is advantageously possible, according to the invention, to design only the first area, in which the fin is arranged, with higher strength. Lower strengths can be assumed for the second area, in which no fin is arranged. This advantageously allows the entire rudder blade to be designed, for example, with different materials or in a different construction, leading to cost reductions and / or enabling the second area to be designed with a narrower profile.This allows the flow characteristics to be optimized to their advantage.

[0023] Preferably, the rudder has exactly one fin.

[0024] Preferably, the rudder is designed as a fully floating rudder.

[0025] Preferably, the fin is connected to the rudder blade by a forced hinge. In particular, the angle of attack of the rudder blade is always less than or equal to the angle of attack of the fin.

[0026] Preferably, the rudder blade has at least one airfoil profile in the form of a wing profile, comprising at least one suction side and at least one pressure side. The asymmetrical rudder blade profiles are formed by providing at least one suction side and at least one pressure side on the rudder blade.

[0027] The rudder blade profile refers to the shape of the rudder blade's cross-sectional area in the direction of flow. The shape of the cross-section can remain constant along the rudder blade's longitudinal extent, while the size of the cross-sectional area can vary, becoming smaller or larger. However, in some embodiments, the size of the rudder blade's cross-sectional area can also remain constant when viewed along its longitudinal extent, i.e., its height. Therefore, if the rudder blade has the same shape but different sizes at two different positions along its longitudinal extent when viewed in cross-section, the rudder blade profile is nevertheless the same at these two positions. Preferably, the rudder blade profile corresponds to a NACA airfoil, in particular an asymmetric NACA airfoil.In the area of ​​the rudder blade where the fin is located, the airfoil is formed by the combined profile of the fin and the rudder blade. Specifically, the transition between the fin and the rudder blade is designed such that, when considering the combined profile of both components, it resembles an airfoil. Accordingly, the suction and pressure surfaces in this section of the rudder blade are formed by portions of the fin's side surface and portions of the rudder blade's side surface.

[0028] Preferably, the rudder blade has an upper rudder blade section and a lower rudder blade section. Preferably, the rudder blade consists only of the upper and the lower rudder blade sections and has no further rudder blade section.

[0029] Preferably, the rudder blade profiles in the upper rudder blade section are designed differently along the entire longitudinal extent of the upper rudder blade section compared to the rudder blade profiles in the lower rudder blade section along the entire longitudinal extent of the lower rudder blade section.

[0030] Preferably, the rudder blade has a first profile in the lower section and a second profile in the upper section. In this embodiment, only the first profile is found in the lower section and only the second profile in the upper section. The cross-sectional shape of the rudder blade remains constant along its longitudinal extent in each section. However, the size or area of ​​the rudder blade's cross-section can preferably vary along its longitudinal extent.

[0031] Preferably, the profiles in the upper and lower rudder blade sections are asymmetrically designed over the entire longitudinal extent of the respective section. Asymmetrical profiles are defined as profiles that do not have an axis of symmetry. In particular, the profile centerline and / or the profile chord do not form an axis of symmetry.

[0032] Preferably, the fin is arranged on the upper section of the rudder blade. In particular, the fin is arranged on the trailing edge of the upper section of the rudder blade. Preferably, the fin extends over the entire longitudinal extent of the upper section of the rudder blade.

[0033] Preferably, the fin extends exclusively along the upper part of the rudder blade.

[0034] Preferably, the lower rudder blade section has at least one side surface which is concave, at least in part, with respect to the flow direction. This side surface is preferably concave along its entire longitudinal extent, at least in part. The side surface of the lower rudder blade section opposite the concave surface is preferably, and in particular entirely, convex with respect to the flow direction. Preferably, the at least one side surface has, in addition to the concave area, a convex area, with the convex area being located in front of the concave area when viewed in the flow direction. The rudder is therefore preferably designed as a so-called "fishtail" rudder, with the lower rudder blade section being designed as a fishtail rudder only on one side, and more preferably exclusively on one side.

[0035] The side surface, which is at least partially concave, preferably forms a printing surface.

[0036] Preferably, the lower rudder blade section has the previously described design as a half-sided "fishtail" rudder, while the upper rudder blade section is designed as a rudder having a NACA profile, preferably as an asymmetrical, particularly preferably as a twisted rudder.

[0037] Preferably, a section of the leading edge, i.e., the so-called leading edge, of the upper rudder blade section and / or a section of the lower rudder blade section is completely offset to port or starboard relative to the rudder's longitudinal centerline. The rudder blade can therefore be twisted. Preferably, a region of the rudder blade profile located behind the point of the rudder blade with the greatest profile thickness, viewed in the direction of flow, is symmetrically designed, and the longitudinal centerline is the axis of symmetry of this symmetrically designed region.

[0038] Preferably, the leading edge is offset to starboard or port along the entire longitudinal extent of the leading edge in the respective rudder blade section, both in the upper and / or lower section.

[0039] Preferably, the upper rudder blade section, when installed on the watercraft, can be arranged above the propeller axis of a propeller located upstream of the rudder blade, or is preferably arranged above it. Preferably, the lower rudder blade section is arranged below the propeller axis, with the propeller axis preferably defining the transition between the upper and lower rudder blade sections.

[0040] The rudder may preferably have a Costa bulb. If the rudder has a Costa bulb, it is preferably arranged in a region between the upper and lower rudder blade sections.

[0041] Preferably, the upper and lower sections of the rudder blade each have a suction side. The suction sides of the upper and lower sections are preferably located on opposite surfaces of the rudder blade. Alternatively, the suction side of the upper and lower sections are located on the same side of the rudder blade.

[0042] Preferably, the upper rudder blade section and the lower rudder blade section each have a pressure side. Preferably, the pressure side of the upper rudder blade section and the pressure side of the lower rudder blade section are arranged on opposite sides of the rudder blade, or preferably, the pressure side of the upper rudder blade section and the pressure side of the lower rudder blade section are arranged on the same side of the rudder blade.

[0043] In the respective rudder blade sections, the pressure side and the suction side are arranged on opposite surfaces of the rudder blade. Preferably, the rudder blade profile, or all rudder blade profiles along the longitudinal extent of the rudder blade, which are arranged in the lower rudder blade section, correspond to a mirror image of the rudder blade profile(s) of the upper rudder blade section with respect to the profile chord.

[0044] Preferably, the rudder has a smaller maximum profile thickness in the lower section than in the upper section. In particular, the cross-sectional area of ​​the rudder blade can decrease from top to bottom when viewed in the direction of flow. Preferably, the cross-sectional area of ​​the rudder blade decreases in the direction of flow such that it decreases continuously from top to bottom. This results in a tapered shape of the rudder blade in a side view.

[0045] Preferably, the rudder blade has a single airfoil profile in its upper section. Preferably, the airfoil thickness in its upper section is 22% to 32%, more preferably 25% to 30%, and most preferably 26.5% to 28.5% of the airfoil chord length.

[0046] Preferably, the rudder blade has a single airfoil profile in its lower section. Preferably, the airfoil thickness in its lower section is 10% to 18%, more preferably 12% to 16%, and most preferably 13.5% to 15% of the airfoil chord length.

[0047] Preferably, the lower rudder blade section can be bent or angled at least partially or completely towards one side of the rudder.

[0048] In a state installed on the ship and with the rudder in a neutral position, the upper rudder blade section is preferably oriented substantially vertically when viewed in the direction of flow. The lower rudder blade section, located below the upper rudder blade section, is preferably not oriented vertically, but rather at an angle to the upper rudder blade section or the vertical. In other words, the lower rudder blade section is at an angle to an imaginary, vertically downward-pointing extension of the upper rudder blade section. In particular, a large portion of the lower rudder blade section is located laterally to this imaginary extension of the upper rudder blade section. The lower rudder blade section is, in particular, curved or angled towards the port or starboard side of the ship.

[0049] Therefore, the angle between the upper rudder blade section and the lower rudder blade section is preferably that angle at which a longitudinal axis of the lower rudder blade section is relative to the longitudinal axis of the upper rudder blade section.

[0050] Furthermore, it can be provided that the angle is between 5° and 35°, preferably between 10° and 30°, particularly preferably between 15° and 25°, most preferably 20°.

[0051] The preferred angular ranges, particularly in the case of a twin-propeller vessel, ensure, firstly, that the turbulence resulting from the influence of the ship's hull on the propeller wake is sufficiently reduced. Secondly, the vertical component of the lift force of the lower rudder blade section is so low in these preferred angular ranges that the stability of the ship's position in the water is not adversely affected. It is preferable to provide a transition zone between the upper and lower rudder blade sections, wherein the transition zone is partially arc-shaped, partially annular, or wedge-shaped.

[0052] The lower rudder blade section can be angled or curved towards one side of the rudder. In a curved design, the lower rudder blade section has a continuous or variable curvature towards one side of the rudder. In an angled design, both the upper and lower rudder blade sections are essentially straight, and the rudder has a kink at the transition between the upper and lower rudder blade sections.

[0053] Due to the lower rudder blade section being bent or angled to one side of the rudder, turbulence in the propeller wake is reduced, particularly when the rudder according to the invention is used on a twin-propeller vessel. Since, on a twin-propeller vessel, the lateral arrangement of each propeller next to the hull results in a one-sided influence on the flowing water, especially the propeller wake, the rudder according to the invention, with exactly one lower rudder blade section bent or angled to one side of the rudder per rudder, is particularly suitable for reducing turbulence.

[0054] Furthermore, reducing turbulence in the flowing water, particularly in the propeller wake, increases the rudder's efficiency, allowing it to be shorter compared to conventional rudders. It also enables the use of a thinner rudder. These measures result in reduced drag and lower manufacturing costs.

[0055] Preferably, the upper rudder blade section and / or the lower rudder blade section are essentially straight. In particular, the upper rudder blade section and / or the lower rudder blade section are not curved or S-shaped.

[0056] It is advantageous for the rudder to have no auxiliary or stabilizing rudders, and / or for the lower rudder blade section to be neither an auxiliary nor a stabilizing rudder. The lower rudder blade section is thus not an auxiliary or stabilizing rudder. In particular, with the exception of its curved or angled design or orientation relative to the upper rudder blade section, the lower rudder blade section is preferably designed like a conventional lower rudder blade section and has essentially the same dimensions. In contrast, auxiliary and stabilizing rudders are significantly smaller and serve less to change the course of a ship than to stabilize the ship's position in the water.

[0057] It is further preferably possible that the lower rudder blade section is at an angle to the upper rudder blade section. The angle between the lower and upper rudder blade sections can be determined on both sides of the rudder between the rudder's side walls located on the respective side.

[0058] Preferably, the rudder blade has symmetrical profiles with respect to the flow direction in its lower section, particularly along its entire longitudinal extent. In this case, the lower section is especially angled or curved.

[0059] Preferably, the rudder blade has an upper rudder blade section and a lower rudder blade section, wherein the rudder blade in the upper rudder blade section, in particular substantially along the entire longitudinal extent of the upper rudder blade section, has asymmetrical rudder blade profiles with respect to the flow direction.

[0060] Preferably, the rudder blade has symmetrical rudder blade profiles only in the lower rudder blade section and asymmetrical rudder blade sections only in the upper rudder blade section.

[0061] Alternatively, the lower rudder blade section can have both symmetrical and asymmetrical rudder blade profiles. The same can apply to the upper rudder blade section. Furthermore, the lower rudder blade section can have only symmetrical rudder blade profiles, and the upper rudder blade section can have both symmetrical and asymmetrical rudder blade profiles. It is also possible for the upper rudder blade section to have only asymmetrical rudder blade profiles, while the lower rudder blade section can have both symmetrical and asymmetrical rudder blade profiles.

[0062] Preferably, a trailing edge of the lower rudder blade section and a trailing edge of the fin are arranged flush with the rudder in a side view, so that in a view of the side surface of the rudder blade the rudder blade has a substantially L-shaped form.

[0063] Preferably, the rudder blade has a protective layer, particularly in the area of ​​a leading edge and / or on a pressure side. This protective layer serves to protect the rudder from cavitation damage. The protective layer is preferably applied to the pressure side, as the effect of cavitation is more pronounced there.

[0064] Preferably, the maximum width of the fin corresponds to 20% to 40%, more preferably to 25% to 35%, and most preferably to 30% of the maximum width of the rudder blade when viewed in the direction of the flow. Additionally or alternatively, the maximum width of the fin corresponds to a maximum of 45% of the maximum width of the rudder blade when viewed in the direction of the flow. The width of the fin is measured with the rudder installed, along a portion of the fin parallel to the direction of the flow.

[0065] Preferably, the rudder is a fully suspended rudder.

[0066] Furthermore, the invention relates to a rowing system comprising a first rudder and a second rudder. The first rudder and the second rudder each have a rudder blade, each rudder blade having a fin which is pivotably arranged on the rudder blade. The maximum height of the fins of the first and second rudders is in each case less than the maximum height of the rudder blades of the first rudder and the second rudder, respectively. The fins are arranged parallel to a rudder shaft of the respective rudder with respect to their longitudinal extent.

[0067] Such a rudder system is preferably used for a watercraft with a twin-screw propulsion system. Furthermore, the rudder system can be used for all other types of vessels, especially vessels with only one screw.

[0068] Preferably, the rudder blades of the first rudder and the second rudder have asymmetrical profiles along their entire longitudinal extent with respect to the flow direction. In the area of ​​the rudder blades where the fin is located, the rudder blade profiles are formed by the profile of the rudder blade and the profile of the fin. The first rudder and the second rudder preferably each have an upper rudder blade section and a lower rudder blade section. Preferably, the rudder blade profiles in the upper and lower rudder blade sections are designed differently for each rudder.

[0069] Preferably, the upper and lower rudder blade sections of the first and second rudders each have a pressure side. The pressure side of the upper and lower rudder blade sections is located on opposite or identical surfaces of the rudder blades of the first and second rudders. Additionally or alternatively, the upper and lower rudder blade sections of the first and second rudders each have a suction side, wherein the suction sides of the upper and lower rudder blade sections are located on opposite or identical surfaces of the rudder blades of the first and second rudders.

[0070] Brief description of the characters

[0071] The present invention is explained in more detail below with reference to the figures. The figures show:

[0072] Figure 1: an embodiment of the rudder according to the invention in a side view,

[0073] Figure 2: another embodiment of the rudder according to the invention in a side view with a rudder blade tapering downwards,

[0074] Figure 3: a perspective view of the rudder from Figure 2,

[0075] Figure 4: a view from below of the lower edge of the rudder blade of another embodiment of a rudder according to the invention,

[0076] Figure 5: a view from below of the lower edge of the rudder blade of a further embodiment of a rudder according to the invention,

[0077] Figure 6: a bottom view of a rudder system according to the invention, and

[0078] Figure 7: Views of a leading edge (a) and a trailing edge (b) of a rudder according to a further embodiment, Figure 8: Views of a bottom (a) and a top (b) of the rudder shown in Figure 7,

[0079] Figure 9: Views of a leading edge (a) and a trailing edge (b) of a rudder according to a further embodiment, and

[0080] Figure 10: Views of a bottom (a) and a top (b) of the rudder shown in Figure 9.

[0081] Figure 1 shows a side view of an embodiment of the rudder 100 according to the invention. The rudder 100 has a rudder blade 10, which is mounted on the hull of the watercraft (not shown) by means of a rudder shaft 22. The rudder shaft 22 extends completely along the longitudinal extent L of the rudder blade 10. The rudder blade 10 has a leading edge 12 and a trailing edge 13. The trailing edge 13 of the rudder blade 10 is composed of three sections 13a, 13b, and 13c. Sections 13a and 13c of the trailing edge 13 of the rudder blade 10 run parallel to the rudder shaft 22. Section 13b of the trailing edge of the rudder blade connects the two sections 13a and 13c. The three sections 13a, 13b, and 13c of the trailing edge 13 of the rudder blade 10 therefore have a stepped shape in the side view. Due to this stepped design of the trailing edge 13 of the rudder blade 10, the rudder blade 10 has an L-shape in side view.

[0082] A fin 11 is pivotably mounted on the rudder blade 10. The axis of rotation of the fin 11 runs parallel to the axis of rotation of the rudder 100, i.e., parallel to the rudder shaft 22. The fin 11 is located in a cutout in the rudder blade 10, which is formed by sections 13a and 13b of the trailing edge 13 of the rudder blade 10. In side view, the shape of the rudder blade 10 and the fin 11 together therefore corresponds to the shape of a conventional rudder without a fin. The fin has a trailing edge 25 which, in side view, is flush with section 13c of the trailing edge 13 of the rudder blade 10.

[0083] The fin 11 is connected to the rudder tube or the watercraft by means of a connecting device 18. Preferably, the fin 11 is controlled via the connecting device 18. Furthermore, the fin 11 is attached to the rudder blade 10 by a hinge system 19. The hinge system 19 is arranged between section 13a of the trailing edge 13 of the rudder blade 10 and the fin 11.

[0084] The rudder blade 10 has a height Hl, which, relative to the installed state of the rudder 100 on the watercraft, extends from a lower edge 14 to an upper edge 15. The fin 11 has a height H2, which extends from a lower edge 16 to an upper edge 17 of the fin 11. The heights Hl and H2 represent the maximum height of the fin and the rudder blade 10, respectively. The height Hl is always greater than the height H2, so the rudder blade 10 has a first upper rudder blade section 20, on which the fin 11 is arranged, and a second rudder blade section 21, on which no fin is arranged. The upper and lower rudder blade sections 20, 21 are separated by an imaginary plane in which the propeller axis 26 of a propeller (not shown) runs.

[0085] Because a fin 11 is arranged only in the upper rudder blade section 20, different strengths can be assigned to the upper rudder blade section 20 and the lower rudder blade section 21. In particular, a lower strength can be advantageously assigned to the lower rudder blade section 21. For example, the lower rudder blade section 21 can be designed as a hollow profile and / or as a "fishtail" profile or S-shaped profile.

[0086] Figure 2 shows another embodiment of the rudder 100 in a side view. The rudder blade 10 has a fin 11, which is arranged at the trailing edge 13 of the rudder blade 10. The rudder blade 10 is designed such that it tapers from top to bottom along its longitudinal extent L. This means that the width of the rudder blade 10 decreases continuously from top to bottom, starting from a maximum width Bl. The rudder blade 10 and the fin 11 are designed analogously to the embodiment according to Figure 1 such that the rudder blade 10 has the shape of a rudder blade without a fin in a side view. This means, in particular, that the trailing edge 25 of the fin is flush with section 13c of the trailing edge 25 of the rudder blade 10, wherein, in this embodiment, section 13a and the trailing edge 25 of the rudder blade run obliquely to a rudder shaft 22 (not shown), which is vertical in the installed state.Fin 11 is designed to conform to the tapered shape of the overall rudder blade. Therefore, the width of fin 11 also decreases from a maximum width B2 in the upper region of fin 11 to a minimum width in the lower region along the lower edge 16 of fin 11.

[0087] Figure 3 shows a perspective view of the rudder blade 10 according to the embodiment shown in Figure 2. This perspective view reveals that the rudder blade has a pressure side 23 and a suction side 24. The pressure side 23 and the suction side 24 each extend over the entire side surfaces of the upper rudder blade section 20 and the lower rudder blade section 21, as well as over the side surfaces of the fin 11. The pressure side 23 and the suction side 24 result in asymmetrical profiles of the rudder blade 10 along its entire height Hl. In the lower rudder blade section 21, the rudder blade profile is formed solely by the profile of the rudder blade 10. In the upper rudder blade section 20, the profile is composed of the profile of the rudder blade 10 and the profile of the fin 11, which together form a complete profile of the rudder blade 10 in this area.

[0088] Figure 4 shows a bottom view of the lower edge 14 of the rudder blade 10 of a rudder 100 in a further embodiment. The rudder blade 10 has an upper rudder blade section 20 and a lower rudder blade section 21. The rudder blade 10 has a pressure side 23 and a suction side 24 opposite the pressure side 23, the pressure side 23 extending completely over one side of the rudder blade 10. The suction side 24 extends completely over the side of the rudder blade 10 opposite the pressure side 23. The pressure side 23 and suction side 24 thus extend over the upper rudder blade section 20 and the lower rudder blade section 21.

[0089] Furthermore, Figure 4 shows that the rudder blade profile in the upper rudder blade section 20 is formed by the profile of the rudder blade 10 in this section and by the profile of the fin 11. In the lower rudder blade section 21, the rudder blade profile is formed solely by the profile of the rudder blade 10.

[0090] Figure 5 shows a bottom view of the lower edge 14 of another embodiment of the rudder blade 10. The rudder blade 10 has an upper rudder blade section 20 and a lower rudder blade section 21, as well as a pressure side 23 and a suction side 24, the arrangement of the pressure side 23 and suction side 24 being identical to the embodiment according to Figure 4. In the lower rudder blade section 21, the rudder blade profile is designed such that on the side surface section of the lower rudder blade section 21, which is designed as the pressure side 23, a rearward area of ​​the side surface, viewed in the direction of flow, is formed as a concave area TI. Thus, the rudder blade 10 has the shape of a Schilling rudder or "fishtail" rudder on one side in the lower rudder blade section 21.

[0091] Figure 6 shows a bottom view of a rudder system 200 according to the invention. The rudder system 200 comprises a first rudder 100a and a second rudder 100b, which, when installed on the watercraft, are arranged side by side in the direction of flow, with the first rudder 100a on the port side and the second rudder 100b on the starboard side. A propeller 28, 29 is assigned to each of the first rudder 100a and the second rudder 100b. The propellers 28, 29 rotate outwards from the top. The terms "inside" and "outside" refer to the installation state of the rudder system on the watercraft, with the outside being the port side for the first rudder 100a and the starboard side for the second rudder 100b.

[0092] The first rudder 100a and the second rudder 100b each have an upper rudder blade section 20 and a lower rudder blade section 21.

[0093] The first rudder 100a has a pressure side 23 and a suction side 24 in the lower rudder blade section 21, wherein the pressure side 23 is located on the outside and the suction side 24 on the inside of the rudder blade 10. The first rudder 100a also has a pressure side 23 and a suction side 24 in the upper rudder blade section 20, wherein in this rudder blade section the pressure side 23 is located on the inside and the suction side 24 on the outside of the rudder blade 10.

[0094] The second rudder 100b is a mirror image of the first rudder 100a along a mirror axis that runs parallel to the rotation axes of the propellers 28, 29, midway between the first rudder 100a and the second rudder 100b. Accordingly, the second rudder 100b also has a pressure side 23 on the outside and a suction side 24 on the inside of the lower rudder blade section 21. In the upper rudder blade section 20, the second rudder 100b has a suction side 24 on the outside and a pressure side 23 on the inside.

[0095] Figure 7 shows two views of a rudder 100 according to a further embodiment with an alternative configuration of the rudder blade profiles. Figure 7a shows a view of a leading edge 12 of the rudder 100 and Figure 7b shows a view of a trailing edge 13 of the rudder 100. Analogous to the previously described embodiment, the rudder 100 comprises an upper rudder blade section 20 and a lower rudder blade section 21. A fin is arranged in the upper rudder blade section 20 in the region of the trailing edge 13.

[0096] Figure 8a shows a view of the underside of the rudder 100 from Figure 7. Figure 8b shows a view of the upper side of the rudder 100 from Figure 7. As can be seen in Figure 8a, the lower rudder blade section 21 has symmetrical rudder blade profiles 30. In contrast, the upper rudder blade section 20 has asymmetrical rudder blade profiles 31, as shown in Figure 8b.

[0097] Figures 9 and 10 show another embodiment of a rudder 100. Figures 9a and 9b show a view of the front and rear of the rudder 100. In this embodiment, the rudder 100 has an upper and a lower rudder blade section 20, 21, wherein the lower rudder blade section 21 is arranged at an angle W to the upper rudder blade section 20. The angle W refers to an angle between a first longitudinal axis LA of the upper rudder blade section 20 and a second longitudinal axis LB of the lower rudder blade section 21. In the region of the transition between the upper rudder blade section 20 and the lower rudder blade section 21, a kink is formed in the rudder blade. For this purpose, a wedge-shaped element is arranged between the component forming the upper rudder blade section 20 and the component forming the lower rudder blade section 21. A fin 11 is arranged in the upper rudder blade section 20.The fin 11 extends exclusively in the upper rudder blade section 20. Figure 10 shows a view of the upper and lower surfaces of the rudder 100 from Figure 9. Figure 10a shows a view of the lower surface of the rudder 100, where it can be seen that the lower rudder blade section 21 comprises symmetrical rudder blade profiles 30. Figure 10b shows a view of the upper surface of the rudder 100, where the upper rudder blade section 20 has asymmetrical rudder blade profiles 31.

[0098] Reference symbol list:

[0099] 100, 100a, 100b oars

[0100] 200 rowing system

[0101] 10 rudder blade

[0102] 11 fin

[0103] 12 Leading edge of the rudder blade

[0104] 13 Trailing edge of the rudder blade

[0105] 13a, 13b, 13c Sections of the trailing edge

[0106] 14 Lower edge of the rudder blade

[0107] 15 Top edge of the rudder shaft

[0108] 16 Lower edge of the fin

[0109] 17 Top edge of the fin

[0110] 18 Connecting device

[0111] 19 hinge system

[0112] 20 upper rudder blade section

[0113] 21 lower rudder blade section

[0114] 22 Rudder shaft

[0115] 23 printed page

[0116] 24 Suction side

[0117] 25 Trailing edge of the fin

[0118] 26 Propeller axle

[0119] 27 concave areas

[0120] 28, 29 Propeller

[0121] 30 symmetrical rudder blade profile

[0122] 31 asymmetric rudder blade profile

[0123] L Longitudinal extent

[0124] LA first longitudinal axis

[0125] LB second longitudinal axis

[0126] Bl maximum width of the rudder blade B2 maximum width of the fin

[0127] Maximum height of the rudder blade

[0128] H2 maximum height of the fin

[0129] W angle

Claims

Claims 1. Rudder (100) for watercraft, in particular ships, comprising a rudder blade (10), wherein the rudder (100) has a fin (11) which is pivotably arranged on the rudder blade (10), wherein a maximum height (H2) of the fin (11) is less than a maximum height (Hl) of the rudder blade (10) and wherein the fin (11) is arranged parallel to a rudder shaft (22) of the rudder (100) with respect to a longitudinal extent (L) of the fin (11), wherein the rudder blade has an upper rudder blade section (20) and a lower rudder blade section (21), characterized in that the upper rudder blade section (20) and the lower rudder blade section (21) are designed such that they have different buoyancy coefficients, wherein the buoyancy coefficient of the upper rudder blade section (20) is greater than the buoyancy coefficient of the lower rudder blade section (21).

2. Rudder (100) according to claim 1, wherein the rudder blade profile in the region of the rudder blade (10) in which the fin (11) is arranged is formed by the profile of the rudder blade (10) and the profile of the fin (11), and / or wherein the rudder blade, in particular substantially along its entire longitudinal extent, has asymmetrical rudder blade profiles with respect to the flow direction.

3. Rudder (100) according to one of the preceding claims, wherein the rudder blade (10) is designed such that it has at least one rudder blade profile in the form of an airfoil profile comprising at least one suction side (24) and at least one pressure side (23).

4. Rudder (100) according to one of the preceding claims, wherein the rudder blade profiles are preferably designed differently in the upper rudder blade section (20) along the entire longitudinal extent (L) of the upper rudder blade section (20) compared with the rudder blade profiles in the lower rudder blade section (21) along the entire longitudinal extent (L) of the lower rudder blade section (21).

5. Rudder (100) according to one of the preceding claims, wherein the fin (11) is arranged on the upper rudder blade section (20) and wherein the fin (11) extends over the entire longitudinal extent of the upper rudder blade section (20) and / or wherein the fin (11) extends exclusively along the upper rudder blade section (20).

6. Rudder (100) according to one of the preceding claims, wherein the lower rudder blade section (21) has at least one side surface which is at least partially concave with respect to the direction of flow.

7. Rudder (100) according to one of the preceding claims, wherein a section of a leading edge (12) of the upper rudder blade section (20) and / or a section of a leading edge (12) of the lower rudder blade section (21) is completely offset to port or to starboard relative to a central longitudinal line of the rudder (100).

8. Rudder (100) according to one of the preceding claims, wherein the upper rudder blade section (20) in the state of the rudder (100) being installed on the watercraft can be arranged above a propeller axis (26) of a propeller arranged upstream of the rudder blade on the watercraft and wherein the lower rudder blade section (21) can be arranged below the propeller axis (26), wherein preferably a transition between the upper rudder blade section (20) and the lower rudder blade section (21) runs substantially along the propeller axis (26).

9. Rudder (100) according to one of the preceding claims, wherein the upper rudder blade section (20) and the lower rudder blade section (21) each have a suction side (24) and wherein the suction sides (24) of the upper rudder blade section (20) and the lower rudder blade section (21) are arranged on opposite side surfaces of the rudder blade (10) or wherein the suction side (24) of the upper rudder blade section (20) and the suction side (24) of the lower rudder blade section (21) are arranged on the same side of the rudder blade (10), and wherein the upper rudder blade section (20) and the lower rudder blade section (21) each have a pressure side (23) and wherein the pressure side (23) of the upper rudder blade section (20) and the lower rudder blade section (21) are arranged on opposite side surfaces of the rudder blade (10) or wherein the pressure side (23) of the upper rudder blade section (20) and the pressure side (23) of the lower rudder blade section (21) are arranged on the same side of the rudder blade (10).

10. Rudder (100) according to one of the preceding claims, wherein the rudder (100) has a lower maximum profile thickness in the lower rudder blade section (21) than in the upper rudder blade section (20), and / or wherein the rudder blade (100) has a maximum profile thickness of 22% to 32%, preferably 25% to 30% and particularly preferably 26.5% to 28.5% of the profile chord length in the upper rudder blade section (20), and / or wherein the rudder blade (10) has a maximum profile thickness of 10% to 18%, preferably 12% to 16% and particularly preferably 13.5% to 15% of the profile chord length in the lower rudder blade section (21).

11. Rudder (100) according to one of the preceding claims, wherein the lower rudder blade section (21) is at least partially or completely bent or angled to one side of the rudder, and / or wherein the rudder blade in the lower rudder blade section (21), in particular substantially along the entire longitudinal extent (L) of the lower rudder blade section (21), has symmetrical rudder blade profiles with respect to the flow direction, and / or wherein the rudder blade in the upper rudder blade section (20), in particular substantially along the entire longitudinal extent (L) of the upper rudder blade section (20), has asymmetrical rudder blade profiles with respect to the flow direction.

12. Rudder (100) according to one of the preceding claims, wherein a trailing edge (13) of the lower rudder blade section (21) and a trailing edge (25) of the fin are arranged flush with the rudder (100) in a side view, such that in a side view of the rudder (100) the rudder blade (10) has a substantially L-shaped form. TI 13. Rudder (100) according to one of the preceding claims, wherein the rudder blade (10), in particular in the region of a leading edge (12) of the rudder blade and / or in the region of a pressure side (23), has a protective layer and / or wherein the rudder (100) is a fully floating rudder, and / or wherein the maximum width (B2) of the fin (11) in a direction along an extension of the rudder blade (10) parallel to the flow direction corresponds to 20% to 40%, preferably 25% to 35% and particularly preferably 30% of the maximum width (Bl) of the rudder blade (10) viewed in the flow direction, and / or wherein the maximum width (B2) of the fin (11) corresponds to a maximum of 45% of the maximum width (Bl) of the rudder blade (10) viewed in the flow direction.

14. Rudder system (200) comprising a first rudder (100a) and a second rudder (100b), wherein the first rudder (100a) and the second rudder (100b) each have a rudder blade (10), wherein each rudder blade (10) has a fin (11) which is pivotably arranged on the rudder blade (10), wherein a maximum height (H2) of the fins (11) of the first and second rudders (100a, 100b) is each less than a maximum height (Hl) of the rudder blade (10) of the first rudder (100a) and of the second rudder (100b), respectively, and wherein the fins (11) are each arranged parallel to a rudder shaft (22) of the respective rudder (100a, 100b) with respect to a longitudinal extent (L) of the fins (11).

15. Rudder system (200) according to claim 14, wherein the rudder blades (10) of the first rudder (100a) and the second rudder (100b) have asymmetrical profiles with respect to the flow direction along their respective entire longitudinal extent (L), wherein the rudder blade profiles in the region of the rudder blades (10) in which the fin (11) is arranged are each formed by the profile of the rudder blade (10) and the profile of the fin (11), and / or wherein the first rudder (100a) and the second rudder (100b) each have an upper rudder blade section (20) and a lower rudder blade section (21), and wherein for each of the first rudder (100a) and the second rudder (100b), the rudder blade profiles in the upper rudder blade section (20) and in the lower rudder blade section (21) are configured differently, wherein preferably the upper rudder blade section (20) and the lower rudder blade section (21) of the first rudder (100a) and the second rudder (100b) each have a pressure side (23) and wherein the pressure side (23) of the upper rudder blade section (20) and the lower rudder blade section (21) are arranged on opposite or on the same side surfaces of the rudder blade (10) of the first rudder (100a) and the second rudder (100b) and / or wherein the upper rudder blade section (20) and the lower rudder blade section (21) of the first rudder (100a) and the second rudder (100b) each have a suction side (24) and wherein the suction sides (24) of the upper rudder blade section (20) and the lower rudder blade section (21) are arranged on opposite or on the same side surfaces of the rudder blade (10) of the first rudder (100a) and the second rudder (100b) are arranged.

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