Abstract:
The invention relates to an arrangement for multi screw vessels, in particular twin screw vessels, with external propeller shafts, as well as to a method for producing such an arrangement. The arrangement according to the invention is in particular suitable for a drive system of an above-mentioned multi screw vessel and to improve the energy efficiency thereof.

Description:
FIELD OF INVENTION 
     The invention relates to an arrangement for multi screw vessels, in particular twin screw vessels, with external propeller shafts, as well as to a method for producing such an arrangement. The arrangement according to the invention is in particular suitable for a drive system of an afore-mentioned multi screw vessel and to improve the energy efficiency thereof. 
     BACKGROUND OF THE INVENTION 
     Several devices are known from the prior art for reducing the drive power requirement of single screw vessels. EP 2 100 808 A1 is mentioned in an exemplary manner here. 
     In the case of normal single screw vessels, the propeller shaft of the vessel&#39;s propeller runs inside the vessel&#39;s hull. In the case of these vessels, only the end of the propeller shaft protrudes from the vessel&#39;s hull, wherein the ship screw is attached to the protruding end of the propeller shaft. In contrast, several types of vessels are equipped as multi screw vessels, that is, with at least two ship screws or at least two ship propellers, respectively. In particular, twin screw vessels are known, which have two ship screws or ship propellers, respectively. A vessel type, which can often be found in the case of multi screw vessels, is a multi screw vessel with exterior propeller shafts. In the case of this vessel type, the at least two propeller shafts are arranged at least partially outside of the vessel&#39;s hull. In the case of this vessel type normally a significant part of the respective propeller shafts is arranged externally. For example, the propeller shaft can also be arranged externally at least 1 m, preferably also at least 3 m, often at a length of 5 m or more. Usually the external section of the propeller shafts is thereby only sheathed by a pipe or the like and is spatially spaced apart from the vessel&#39;s hull. Usually each external part of the propeller shafts is supported via a shaft bracket, wherein the shaft bracket is connected to the vessel&#39;s hull via shaft bracket arms. The shaft bracket is normally arranged at the end region of the propeller shafts, so that the propeller of the vessel is attached to the propeller shaft in longitudinal direction of the propeller shaft, just behind the shaft bracket. Often each external propeller shaft is supported by means of exactly one shaft bracket. 
     Devices for improving the energy efficiency or for reducing the drive power requirement, respectively, are not known for such a vessel type of a multi screw vessel with external propeller shafts. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is the object of the present invention to specify an arrangement for multi screw vessels with external propeller shafts, by means of which the drive power requirement of these multi screw vessels can be reduced. 
     This object is solved by means of an arrangement for multi screw vessels, in particular twin screw vessels, with external propeller shafts, comprising at least two shaft brackets for supporting the propeller shafts, wherein each of the at least two shaft brackets has at least one shaft bracket arm, preferably at least two shaft bracket arms, for fastening the respective shaft bracket to the multi screw vessel, as well as at least two devices for reducing the drive power requirement of the multi screw vessels, wherein each device is assigned to a shaft bracket, and wherein each of the at least two devices comprises at least one hydrofoil. In the case of the arrangement, at least one shaft bracket arm of each shaft bracket is furthermore formed as a hydrofoil of the device, wherein, in addition to the shaft bracket arms, no further hydrofoils are provided, or each of the at least two devices of the arrangement comprises a fore-nozzle, wherein, in the case of each of the at least two devices, at least one fin each is provided, which is formed as a hydrofoil of the device, wherein the at least one fin is arranged in the interior of the fore-nozzle and/or on the outside of the fore-nozzle. 
     The shaft brackets are arranged on the external (that is, located outside of the hull) part of the respective propeller shaft, so as to brace or mount, respectively, and/or to seat the latter. Each shaft bracket is connected to the vessel&#39;s hull via one, preferably via two or more shaft bracket arms. The shaft bracket arms have the function of a support strut, via which the forces, which act on the shaft bracket, are transferred to the hull. 
     The at least two devices for reducing the drive power requirement of the multi screw vessels each comprise at least one hydrofoil, preferably a plurality of hydrofoils. On principle, the at least one hydrofoil can be formed by every object or every device which has a hydrofoil profile. The at least one hydrofoil of the devices is provided for influencing the propeller inflow, so that a higher energy efficiency can be reached. Preferably, the at least one hydrofoil is a stator with a hydrofoil profile, that is, a stationary element with a hydrofoil profile. In the present context the embodiment with a hydrofoil profile refers to a cross sectional view of the at least one hydrofoil. Preferably, the at least one hydrofoil has a hydrofoil profile throughout, that is, in particular across its entire longitudinal extension. It is also possible, however, for the at least one hydrofoil, viewed in the longitudinal direction thereof, to have a hydrofoil profile only in parts or in sections. Advantageously, the at least one hydrofoil is formed so as to be elongate, that is, with a significantly greater length than width. The at least one hydrofoil is to be formed or arranged in such a manner that a most advantageous propeller inflow is reached, which leads to an improved energy efficiency or to a reduced drive power requirement, respectively. In particular, this can be attained in that the at least one hydrofoil generates a pre-twist in the propeller inflow (at a suitable location). 
     The devices assigned to a shaft bracket each are conveniently arranged in the region of or on the shaft bracket, and/or are formed so as to be integrated with the shaft bracket or parts of the shaft bracket and/or so as to interact with the shaft bracket or parts of the shaft bracket. Viewed in the travel direction of the vessel, the devices assigned to the respective shaft bracket are in particular arranged at the height of the shaft bracket. Viewed in the longitudinal direction of the vessel, the device is in particular arranged so as not to protrude beyond the shaft bracket, in particular so as not to protrude in the direction of the vessel&#39;s propeller. 
     In a first embodiment alternative of the arrangement according to the invention, at least one of the shaft bracket arms of each shaft bracket is formed as a hydrofoil and forms the at least one hydrofoil of the device. Preferably, a plurality of the, in particular at least two, shaft bracket arms, more preferably all of the shaft bracket arms of each shaft bracket are formed as hydrofoils. This means that the at least one shaft bracket arm has a hydrofoil profile, at least in sections. In addition to the shaft bracket arms formed as hydrofoils it is furthermore provided for the device not to have any further hydrofoils, which are not shaft bracket arms. In this case it is advantageous that the already present shaft bracket arms only have to be redesigned as hydrofoils and that no additional hydrofoils need to be provided. Accordingly, the shaft bracket arms fulfill their normal support function with reference to the shaft bracket and, additionally, a guide function as a result of their hydrofoil profile. One end of the shaft bracket arms is connected to the shaft bracket and the other end is connected, in particular fixedly, to the vessel&#39;s hull. If the at least one shaft bracket arm is formed as a hydrofoil only in sections, it is advantageous, if at least the region of the shaft bracket arm facing the shaft bracket is formed as a hydrofoil. In the case of this alternative, the devices can consist exclusively of the at least one shaft bracket arm, which is formed as a hydrofoil, or can furthermore also comprise further components. 
     In a second alternative of the arrangement, each of the at least two devices comprises a fore-nozzle. The fore-nozzle is arranged upstream of the respective propeller in travel direction of the multi screw vessel. The term “in travel direction” is to be understood here as the forwards travel direction of a multi screw vessel. In contrast to Kort nozzles or rudder propellers, e.g., no propeller is arranged inside the fore-nozzle. The fore-nozzle is furthermore arranged so as to be spaced apart from the propeller. Advantageously, the fore-nozzle is formed in such a manner that the water flow flowing through said fore-nozzle is at least partially, preferably completely, guided to the propeller, which is arranged downstream. Usually the fore-nozzle will have a tubular shape. On principle, however, any other cross sectional shape, for example an angular cross sectional shape, is also possible. The fore-nozzle can be formed in one piece or integrally, respectively, or can be pieced together from a plurality of individual parts to form a fore-nozzle, wherein the individual parts are preferably connected, in particular welded, to one another or to other components of the device and/or of the arrangement. Preferably, at least a partial region of the fore-nozzle is arranged above the propeller shaft and/or below the propeller shaft of the vessel&#39;s propeller. 
     On principle, it is possible for the fore-nozzle to comprise only a partial section of a nozzle or of a nozzle ring (e.g. a ¼ nozzle ring, a ⅓ nozzle ring, a ½ nozzle ring, a ⅔ nozzle ring, a ¾ nozzle ring, etc.). In the case of such an embodiment, the fore-nozzle is formed so as to be open, viewed across the circumference. Preferably, however, the fore-nozzle is formed so as to be closed, viewed in circumferential direction. For this purpose, the nozzle can be formed so as to be continuous by 360° in circumferential direction. In the case of a fore-nozzle, which is formed in several parts, in particular also in the case of a closed nozzle circumference, the individual parts of the fore-nozzle can furthermore be connected to parts of the arrangement and/or of the device, so that these connection parts then form a part of the nozzle circumference. In the case of a fore-nozzle, which is open viewed across the circumference, the fore-nozzle can be formed so that at least ¾ of the total circumference is closed, so that at least ⅔ of the total circumference is closed, so that at least ½ of the total circumference is closed, so that at least ⅓ of the total circumference is closed or so that at least ¼ of the total circumference is closed. 
     The wall of the fore-nozzle forms an inner region, which is enclosed by the nozzle jacket or the nozzle wall at a fore-nozzle each, which is theoretically closed on the water inlet and water outlet opening. A fore-nozzle, which is closed across the circumference, as well as a fore-nozzle, which is partially open, viewed across the circumference, hereby form an inner region. In the case of the nozzle, which is partially open viewed across the circumference, the end region is enclosed in circumferential direction by the jacket of the fore-nozzle as well as by a theoretical plane between the two end points of the nozzle jacket in circumferential direction. 
     The at least one fin, which is formed as a hydrofoil, is arranged in the interior of the fore-nozzle, that is, in the inner region of the fore-nozzle, and/or on the outside of the fore-nozzle. Preferably, the at least one fin is fixedly connected to the fore-nozzle. It is also possible for at least one fin to be arranged on the inside and for at least one fin to simultaneously be arranged on the outside of the fore-nozzle. Two fins can also be arranged in such a manner that one fin is arranged inside the fore-nozzle and the other fin is arranged outside of the fore-nozzle, wherein, each viewed in their longitudinal direction, they are arranged downstream from one another and both are fastened to the nozzle jacket, so that a single total fin results as a whole. The at least one fin can also be arranged on the inside as well as on the outside, for example, when the fin passes through the fore-nozzle jacket. If the at least one fin is arranged on the outside of the fore-nozzle, it is advantageously fastened to the fore-nozzle, in particular with one of its ends, and is formed as a free end on its other end. If the at least one fin is arranged in the inner region of the fore-nozzle, said fin is advantageously fastened to the nozzle jacket with one end. Advantageously, the other end is fastened to the shaft bracket. On principle, however, this end could also be formed as a free end. On principle, a reverse embodiment would also be possible, in the case of which one end of the at least one fin is arranged on the shaft bracket and the other end is arranged in the interior of the fore-nozzle and is formed as a free end. The at least one fin has a hydrofoil profile and is preferably formed in the manner of a guide fin, that is, it preferably has an expansion, which is in particular significantly longer in the direction of its longitudinal axis than in the direction of its transverse axis. 
     In the case of the second embodiment alternative of the arrangement according to the invention, one or a plurality of the shaft bracket arms can also have a hydrofoil profile, in addition to the hydrofoil, which is formed as at least one fin. In particular, all shaft bracket arms can have a hydrofoil profile. 
     In the case of the first embodiment alternative of the arrangement according to the invention, in the case of which no further hydrofoils except for the shaft bracket arms are provided, a fore-nozzle or also a partial section of a fore-nozzle can be provided, as well. The fore-nozzle is then advantageously fastened to one or a plurality of the shaft bracket arms. 
     In the case of the two embodiment alternatives according to the invention, the at least one hydrofoil can be arranged in the interior of the fore-nozzle or on the outside of the fore-nozzle or both. It is also possible for hydrofoils to be arranged only in the interior of the fore-nozzle or only on the outside of the fore-nozzle. The at least one hydrofoil can have a hydrofoil profile throughout, that is, across its entire length. It is furthermore possible for the hydrofoil profile to only be partially present with regard to the longitudinal direction. If the at least one hydrofoil is formed as a shaft bracket arm, for example, the shaft bracket arm can have a hydrofoil profile in a partial section, whereas a further section can be formed without a hydrofoil profile, for example as a normal support with a round, rectangular or other (cross sectional) profile. 
     The fore-nozzle can be formed concentrically or coaxially with the propeller shaft. That is, the axis of rotation of the fore-nozzle can be located on the axis of the propeller shaft. On principle, however, the axis of rotation of the fore-nozzle can also be displaced as compared to the propeller axis, in particular to the top, to the right, to the left, to the bottom or a combination of two of these displacement directions. The axis of rotation of the fore-nozzle can also be oriented so as to be tilted as compared to the axis of the propeller shaft. 
     The fore-nozzle profile, that is, the profile of the nozzle jacket, preferably has a maximum thickness in the range of between 2% and 20%, preferably of between 5% and 15%, particularly preferably of between 9% and 12% of the maximum length of the fore-nozzle profile. Preferably, the fore-nozzle profile furthermore has a maximum length of between 5% and 60%, preferably of between 20% and 40%, more preferably of between 25% and 30% of the fore-nozzle diameter. The fore-nozzle can furthermore be formed so as to be rotationally symmetrical or also rotationally asymmetrical. In the case of rotationally asymmetric fore-nozzles, the maximum distance between two points on the trailing edge of the fore-nozzle, which are located farthest away from one another, is to be used instead of the diameter for determining the above-mentioned ranges. In particular, the outer diameter of the fore-nozzle is to be used for the consideration at hand. 
     The devices are each preferably arranged at a slight distance to the propeller. In particular, the maximum distance between the device and the respective assigned propeller is preferably maximally 50%, more preferably maximally 30%, most preferably maximally 20% of the propeller diameter. 
     If every device has at least two shaft bracket arms, these two shaft bracket arms are preferably arranged relative to one another at an angular distance of between 30° and 120°, preferably of between 50° and 100°, more preferably of between 60° and 80°, viewed in circumferential direction about the propeller shaft. If provision is made for three shaft bracket arms, the distance between the further shaft bracket arm and the closest one of the at least two shaft bracket arms is preferably between 30° and 90°, more preferably between 50° and 70°. 
     The fore-nozzle, the shaft bracket arms, the shaft brackets and/or the fins can preferably be made completely or partially of metal, in particular of steel. In the alternative or in addition, the use of other materials, for example ceramics or, in particular high-strength and/or fiber-reinforced plastics, is possible. 
     The at least two devices can be formed identically or also differently, the latter in particular in the case of an asymmetric hull of the multi screw vessel. 
     The drive power requirement of multi screw vessels is reduced in an advantageous manner by means of the arrangement according to the invention. By assigning the devices for reducing the drive power requirement of the multi screw vessels to one shaft bracket each, it is ensured that they can be sufficiently fastened and are simultaneously arranged in such a manner that the propeller inflow is optimized fluidically in such a manner that a higher drive energy yield is reached and that a smaller drive power requirement is thus at hand. The embodiment of the shaft bracket arms as hydrofoils is advantageous insofar as the shaft bracket arms must be provided in any event for supporting or fastening the shaft bracket and can thus fulfill two functions, namely the support function on the one hand and the hydrofoil function on the other hand, which is to create a pre-twist in the propeller inflow. As a result of providing a fore-nozzle, it is attained that the propeller inflow is accelerated and/or homogenized at least area by area, whereby the drive power requirement is also reduced. The fore-nozzle furthermore supports the hydrofoils, which are fastened thereto and which are formed as fins. 
     In the case of a preferred embodiment, the at least one shaft bracket arm, preferably the at least two shaft bracket arms, of a shaft bracket are each arranged so as to be integrated in one of the at least two devices, which are assigned to the respective shaft bracket. In the context at hand, “integrated” means that the at least one shaft bracket arm or the at least two shaft bracket arms, respectively, are each part of a device for reducing the drive power requirement. In one embodiment, the device can consist exclusively of the shaft bracket arms, namely when the latter are formed as a hydrofoil profile and if no further hydrofoils are provided. In other embodiments, the shaft bracket arms can be one of a plurality of parts of the device, wherein the shaft bracket arms are then preferably formed integrative with the other parts of the device, that is, they are in particular fixedly connected thereto and form a unit. In a preferred embodiment, provision can be made for exactly two, exactly three or exactly four shaft bracket arms for each shaft bracket. Accordingly, provision can preferably be made for two to four shaft bracket arms for each shaft bracket or preferably for two to three shaft bracket arms for each shaft bracket. Advantageously, each of the at least two shaft brackets has the same number of shaft bracket arms. More preferably, the shaft bracket arms of the at least two shaft brackets are formed identically with regard to their position and/or design and/or dimensioning, in particular length, thickness, diameter, etc. In the alternative, a different embodiment of the shaft bracket arms of the at least two shaft brackets is also preferred with regard to their position and/or design and/or dimensioning, in particular length, thickness, diameter, etc., in particular in the case of multi screw vessels with an asymmetric hull. Advantageously, the shaft bracket arms are formed in the manner of elongate support struts, which run essentially in a straight line. 
     Advantageously, the at least two devices are each fastened to a shaft bracket. If the device comprises a shaft bracket arm, said device can be fastened to the shaft bracket, for example via the shaft bracket arm. In the alternative or in addition, the device can be fastened to the shaft bracket by at least one fin, which belongs to it. If the device further comprises a fore-nozzle, the latter can be fastened to the shaft bracket via a shaft bracket arm and/or a fin. On principle, the fore-nozzle could also be fastened directly to the shaft bracket. This ensures that the forces acting on the device can be transferred to the vessel&#39;s hull via the shaft bracket. 
     It is further preferred for the at least two devices to each be fastened to the half of a respective shaft bracket facing the propeller, in particular to the end region thereof facing the propeller. The shaft bracket is often formed in the manner of an elongate sleeve, in which the propeller shaft is mounted. By arranging the device in the half of the shaft bracket facing the propeller, a distance between device and propeller, which is as small as possible, is reached. In the context at hand, the term “shaft bracket half” is to be understood such that the halves are formed by a line or plane which theoretically runs at right angles to the propeller shaft axis. 
     It is further preferred for the fore-nozzle to be fastened to at least one shaft bracket arm, preferably to a plurality of shaft bracket arms. Particularly preferably, the fore-nozzle is fastened to all shaft bracket arms. In particular, the fore-nozzle can be fastened to exactly two shaft bracket arms or to exactly three shaft bracket arms or also to exactly four shaft bracket arms for each device. A stable arrangement of the fore-nozzle is reached through this. Provision can in particular be made for the fore-nozzle to be formed in a plurality of parts, wherein, for example, one part of the fore-nozzle is fastened between two shaft bracket arms, and further parts of the fore-nozzle are fastened to the respective other sides of the shaft bracket arms. Viewed in travel direction of the vessel, the shaft bracket arms can be formed so as to be integrated completely in the nozzle jacket, so that they are enclosed completely by the nozzle jacket in the contact point or in the fastening region, respectively. On principle, it would also be possible for the shaft bracket arms, viewed in travel direction of the vessel, to protrude only partially into the nozzle jacket. 
     In one embodiment, it is preferred for each device to comprise exactly three shaft bracket arms. In particular, this is preferred in the case of the first alternative embodiment of the arrangement, in the case of which a shaft bracket arm is formed as at least one hydrofoil and in addition to the shaft bracket arms no further hydrofoils are provided. Here it is further preferred for the angular distance between the first, in particular the lowermost shaft bracket arm, and the second, in particular central shaft bracket arm, to be in the range of between 30° and 90°, more preferably of between 50° and 70°, and for the angular distance between the second, in particular central, and the third, in particular upper shaft bracket arm, to be in the range of between 30° and 90°, more preferably of between 50° and 70°. 
     In a further preferred embodiment according to the second embodiment alternative of the arrangement according to the invention, in the case of which provision is made for at least one fin, which is formed as a hydrofoil, and for a fore-nozzle, provision is made for between two and ten fins, more preferably for between three and seven fins, most preferably for between three or four fins. In this case, the fins can be fastened only on the inside of the fore-nozzle or only on the outside of the fore-nozzle or both on the inside as well as on the outside. The internal fins are preferably fastened to the shaft bracket and to the inside of the fore-nozzle. More preferably, in this embodiment a total of three or four fins and two shaft bracket arms are provided, wherein in the case of this consideration, a fin, which probably has a part located inside the fore-nozzle as well as a part located outside the fore-nozzle, but which is located in a line and is thus a total fin and which is formed as a guide fin acting as a unit, is each considered to be a fin. Particularly preferred is an embodiment, in which two fins have parts located on the inside as well as on the outside, two shaft bracket arms are provided and additionally one or two further fins located only inside the fore-nozzle are provided. 
     It is furthermore preferred for the at least one hydrofoil of the arrangement to have an angle of attack and/or for the at least one hydrofoil to be formed to be twisted and thus has an angle of twist. The angle of twist can be constant or also varying. Depending on the attack direction, the angle of attack can be positive or negative. The angle of attack range details specified below are thus to be understood as value, that is, they can be positive or negative, depending on the direction of the attack. More preferably, the angle of attack is formed in the range of between &gt;0° and 40°, preferably of between &gt;0° and 25°, more preferably of between 3° and 20° Viewed across the length of the at least one hydrofoil, the angle of attack can be formed so as to vary or so as to be constant, wherein, in the first alternative, at least the angle of attack is then preferably within one of the above-mentioned ranges at one point of the hydrofoil. If a plurality of hydrofoils is provided, the angles of attack of all of the hydrofoils can be identical or can also differ from one another. Compared to one another, the degree of twist of the hydrofoils can also be identical or different. The hydrofoil, which has at least one angle of attack and/or which is twisted, can in particular be a fin and/or a shaft bracket arm. In the case at hand, the angle of attack, often also referred to as angle of inflow, is to be understood to be the angle between the direction of the inflowing fluid (here in particular water) and the axis of the profile of the hydrofoil in the respective hydrofoil cross section. Accordingly, said angle of attack specifies a measure for the size of the attack of the hydrofoil profile for the inflow. If the at least one hydrofoil is formed so as to be twisted or wound, this angle of attack will vary inevitably, viewed across the length of the hydrofoil. Viewed across the length of the at least one hydrofoil, it is in particular also possible for only a partial region to have an angle of attack and for a different region to be formed without an angle of attack or with an angle of attack of 0°, respectively. In the case of a device, one or a plurality of hydrofoils can also have an angle of attack and one or a plurality of hydrofoils can simultaneously not have an angle of attack (that is, an angle of attack of 0°). 
     If the at least one hydrofoil has an angle of attack and/or if it is formed so as to be twisted, it is further preferred for the angle of attack and/or the degree of twist of the at least one hydrofoil in the region of the at least one hydrofoil which faces the shaft bracket to be larger or smaller than in the remainder of the at least one hydrofoil. Advantageously, a larger or also a smaller pre-twist is created through this, in particular in the region of the propeller inflow, in which it is particularly advantageous with regard to the drive efficiency. The region of the at least one hydrofoil facing the shaft bracket can in particular be the region with which the at least one hydrofoil adjoins the shaft bracket. For example, this can also be a region which extends across maximally 40% of the total length of the hydrofoil, in particular maximally across 20%, more preferably across maximally 10%, most preferably across maximally 5% from the end of the hydrofoil facing the shaft bracket. In the alternative, the region of the at least one hydrofoil facing the shaft bracket can have a length which corresponds to a length of up to 50%, preferably of up to 20%, more preferably of up to 10%, most preferably of up to 5%, of the propeller diameter. If the angle of attack varies within the region facing the shaft bracket, that is, if it is not constant, the maximum value is to be used for the purposes at hand. In the present case, the term “degree of twist” is to be understood as the size of the difference between the largest and the smallest angle of twist within a certain region of the at least one hydrofoil, viewed in longitudinal direction. For example, the region used for this purpose can have a predetermined length, in particular a length of between 1% and 20%, preferably of between 5% and 10%, of the total length of the at least one hydrofoil. 
     In a further preferred embodiment, provision is made for the at least one hydrofoil, which can in particular be formed as a shaft bracket arm or as a fin, to be capable of having different profile thicknesses and/or profile lengths, viewed in the longitudinal direction thereof. It is preferred here, in particular, for the region of the at least one hydrofoil facing the shaft bracket, to have a larger profile thickness than the remainder of the at least one hydrofoil. In the alternative or in addition, it is preferred for the profile of the at least one hydrofoil to taper from its end facing the shaft bracket to its end facing away from the shaft bracket with reference to its profile thickness and/or with reference to its profile length. For the present embodiment, the region of the at least one hydrofoil facing the shaft bracket thereby is to be defined in the same manner as for the preceding embodiment, so that the definition can be applied analogously here. The profile length corresponds to the distance between the front nose region of the profile and the trailing edge of the profile in cross sectional view and thus runs along the chord. The profile thickness refers to the maximum thickness of the profile. This embodiment is also advantageous insofar as the pre-twist, which is induced by means of the at least one hydrofoil, makes the propeller inflow to be even more drive-efficient. 
     Viewed in travel direction of the vessel, the shaft bracket arms can have a larger expansion or width than the fore-nozzle and/or the fins. Viewed in travel direction of the vessel, the shaft bracket arm can in particular have a larger length than the fore-nozzle in the region, in which the fore-nozzle is connected to said shaft bracket arm. In such a case, the shaft bracket arm protrudes beyond the fore-nozzle on both sides, viewed in travel direction of the vessel. Preferably viewed in travel direction of the vessel, the at least one fin has a smaller or maximally an identical expansion as compared to the fore-nozzle, in particular in the region in which the fin is fastened to the fore-nozzle. 
     It is further preferred for the arrangement to comprise at least two propellers, which are operatively connected to the propeller shafts, as well as at least two rudders, wherein each of the at least two rudders is assigned to one of the at least two propellers. Preferably, the at least two rudders further have a propulsion bulb each, which is arranged at a slight distance downstream from the hub of the respective propeller. In the present context, “operatively connected” means that the respective propeller shaft drives the operatively connected propeller. On principle, propulsion bulbs are known from the prior art and are often formed in such a manner that they interact with the propeller hub such that the hub vortex inducted by the propeller hub is reduced. On the part of applicant, it was determined that the arrangement according to the invention operates in a particularly drive-efficient manner, if rudders with propulsion bulbs are each arranged downstream from the propellers. The efficiency of the drive power requirement can be improved further, if so-called twisted rudders are provided, in the case of which partial regions of the rudder blade are offset against one another. Propulsion bulbs are often also called “bulbs”. 
     The object on which the invention is based is also solved by means of a multi screw vessel, in particular a twin screw vessel, with external propeller shafts, which comprises an arrangement as described above in any of the embodiment alternatives or preferred embodiments, respectively, as described above. 
     The invention furthermore relates to a method for producing an arrangement for multi screw vessels, in particular twin screw vessels, with external propeller shafts. In the case of the above-mentioned method, the object on which the invention is based is solved in that provision is made for at least two devices for reducing the drive power requirement of the vessels, wherein each device comprises a fore-nozzle and at least one hydrofoil, wherein the at least one hydrofoil is arranged in the interior of the fore-nozzle and/or on the outside of the fore-nozzle, wherein the at least two devices are each arranged on and fastened to a shaft bracket of a propeller shaft of the multi screw vessel in such a manner that at least one shaft bracket arm, preferably at least two shaft bracket arms, of a shaft bracket are arranged so as to be integrated in one of the at least two devices. The arrangement is preferably formed in one of the embodiment alternatives or preferred embodiments, respectively, as described above. The components used in the method, in particular the devices, the at least one hydrofoil, the fore-nozzle, the shaft bracket, the propeller shaft and the shaft bracket arms can preferably be formed in one of the embodiments as described above. 
     The following steps are carried out in a further development of the method:
         a) providing at least two shaft bracket arms, which are each formed as a hydrofoil, and fastening the at least two shaft bracket arms with one shaft bracket arm end region to a shaft bracket, and with the other shaft bracket arm end region to the vessel&#39;s hull,   b) providing a fore-nozzle, which is open or closed across the circumference, wherein the fore-nozzle comprises at least two nozzle segments,   c) arranging a first nozzle segment between the at least two shaft bracket arms,   d) fastening each of the two end regions of the first nozzle segment to a first side of adjacent shaft bracket arms of the at least two shaft bracket arms, and   e) fastening at least one end region of a second nozzle segment to a second side of one of the at least two shaft bracket arms.       

     As a result of this production method, the device and in particular the fore-nozzle of the device is connected to the shaft bracket arms in an integrative manner. This is attained in particular by providing at least two nozzle segments, wherein the first nozzle segment is fastened between two shaft bracket arms, and the other nozzle segment is fastened to a different, second side, of one of the at least two shaft bracket arms. With both end regions, the second nozzle segment can preferably each be fastened to a second side of the at least two shaft bracket arms, thus resulting in a closed nozzle arrangement as a whole. The nozzle segments are thereby preferably formed in the manner of annular segments, which together form a closed or partially closed fore-nozzle. The at least two nozzle segments are provided separately from one another and are each separately fastened to the shaft bracket arms. The above-mentioned steps a) to e) can also take place in a different time sequence. Preferably, they take place in the time sequence as specified by the numbering. Advantageously, the at least two shaft bracket arms are fastened to the same shaft bracket or support the same shaft bracket, respectively. The end regions of a respective shaft bracket arm are arranged diametrically to one another, that is, on opposite sides of the shaft bracket arm. The terms “first side” and “second side” of the adjacent shaft bracket arms in particular refer to the side surfaces of the shaft bracket arms. In particular, they can be arranged opposite one another. The fastening can preferably be established by means of welding. 
     It is furthermore preferred for the following steps to be provided additionally:
         a1) providing fins which are formed as hydrofoils and fastening the fins to the shaft bracket with one end region,   b1) if applicable, providing through holes in one or a plurality of the nozzle segments, leading the fins through the through holes, and fastening the fins to the respective nozzle segment, and   b2) if applicable, fastening one or a plurality of fins to the exterior of one or a plurality of nozzle segments.       

     The above-mentioned steps a1), b1) and b2) can each be carried out in a different, in a suitable time sequence. With reference to step b1), some or also all fins can be guided through holes in the nozzle segments. 
     The invention furthermore relates to a further method for producing an arrangement for multi screw vessels, in particular twin screw vessels, with external propeller shafts. In the case of this method, the object on which the invention is based is solved by providing at least two devices for reducing the drive power requirement of the vessels, wherein each device comprises at least one hydrofoil, wherein the at least two devices are each arranged and fastened to a shaft bracket of a propeller shaft of the multi screw vessel, wherein at least three shaft bracket arms, preferably exactly three shaft bracket arms are provided for each shaft bracket, which are each connected to the hull of the multi screw vessel with their one end, and which are fastened to the shaft bracket with their other end, wherein the at least three shaft bracket arms are each formed as hydrofoils of the device, wherein no further hydrofoils are provided in addition to the shaft bracket arms, wherein preferably at each device a fore-nozzle is provided, which, together with the at least three shaft bracket arms, which are formed as hydrofoils, each forms a device, and wherein, according to an embodiment alternative or a preferred embodiment, respectively, the arrangement is preferably formed as described above. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Preferred exemplary embodiments of the invention will be explained below by means of the figures. Schematically: 
         FIGS. 1 to 7  show schematic views onto a twin screw vessel from the rear, each with a different embodiment of the arrangement without illustration of the propellers and the rudders; 
         FIG. 8A  shows a side view of a partial region of a twin screw vessel with an arrangement, a propeller and a rudder; 
         FIG. 8B  shows the embodiment according to  8 A from a perspective view at an incline from the front; 
         FIG. 9A  shows the embodiment according to  FIG. 8A  with a rudder with a propulsion bulb; 
         FIG. 9B  shows the embodiment according to  FIG. 9A  from a perspective view at an incline from the front; 
         FIG. 10A  shows a perspective view of a shaft bracket with fins and shaft bracket arms fastened thereto; and 
         FIG. 10B  shows the view from  FIG. 10A  comprising only one shaft bracket arm and without fins. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the case of different embodiments, the same components will also be labeled with the same reference numerals below. 
       FIGS. 1 to 7  each show a view from the rear onto a twin screw vessel, wherein provision is made in each figure for a different embodiment of the arrangement according to the invention on the twin screw vessel. For the sake of clarity, the vessel&#39;s propellers as well as the rudders arranged downstream from the vessel&#39;s propellers, have been omitted in  FIGS. 1 to 7 . 
       FIG. 1  shows a twin screw vessel with a hull  50 , wherein the twin screw vessel is provided with an arrangement  100  according to the invention. The arrangement  100  comprises two shaft brackets  10 , in which propeller shafts  12  are mounted. The propeller shafts  12  are at least partially located outside of the hull  50 . Accordingly, the shaft brackets  10  are also located outside of the hull  50 . The shaft brackets  10  sheath the propeller shaft  12  and support the latter. The hull  50  has a central web  51 , which protrudes downwards. Provision is made on each side of this central web  51  for a shaft bracket  10 , which supports a propeller shaft  12 . 
     Each of the two shaft brackets  10  is fixedly connected to the hull  50  via two shaft bracket arms  11   a  and  11   b . Accordingly, the shaft bracket arms  11   a  and  11   b  are each fixedly connected to the hull  50  with one end and to the shaft bracket  10  with their other, opposite end. As a whole,  FIG. 1  thus illustrates four shaft bracket arms  11   a ,  11   b.    
     A device  20  for reducing the drive power requirement of the twin screw vessel is assigned to each shaft bracket  10 . Each of the devices  20  thereby comprises a fore-nozzle  30  as well as four fins  40   a ,  40   b ,  40   c ,  40   d . The fins  40   a ,  40   b ,  40   c ,  40   d  each comprise an inner part  401  as well as an outer part  402 . The inner part  401  of the fins  40   a ,  40   b ,  40   c ,  40   d  thereby runs from the shaft bracket  10  to the fore-nozzle  30 , and the outer part  402  of the fins  40   a ,  40   b ,  40   c ,  40   d  runs from the fore-nozzle  30  to a free end  403  of the fins  40   a ,  40   b ,  40   c ,  40   d . The fins  40   a ,  40   b ,  40   c ,  40   d  are fixedly connected to the shaft bracket  10  with their respective inner part  401 . Likewise, the fins  40   a ,  40   b ,  40   c ,  40   d  are fixedly connected to the fore-nozzle  30 . The fins  40   a ,  40   b ,  40   c ,  40   d  can thereby be guided through the nozzle jacket through a recess (not illustrated here) in the fore-nozzle  30  and can be fixedly connected to the fore-nozzle  30 , e.g. by means of welding, in the region of the recess. In the case of this embodiment, the fins  40   a ,  40   b ,  40   c ,  40   d  consist of a single, continuous guide fin. In an alternative embodiment, the fins  40   a ,  40   b ,  40   c ,  40   d  can be formed in two parts, wherein one part is formed as inner part  401  between the fore-nozzle  30 , in particular the inside of the nozzle jacket, and the shaft bracket  10 , and the other part is arranged as outer part  402  of the fins  40   a ,  40   b ,  40   c ,  40   d  on the fore-nozzle  30 , in particular on the outer jacket of the fore-nozzle  30 , with one end. All of the fins  40   a ,  40   b ,  40   c ,  40   d  have a hydrofoil profile. The length of the individual fins  40   a ,  40   b ,  40   c ,  40   d  can be identical to one another or different from one another. The angular distances α of the individual fins  40   a ,  40   b ,  40   c ,  40   d  can also be identical or different among one another. 
     The fore-nozzles  30  from the arrangement according to  FIG. 1  have a circular cross section and are thus formed rotationally symmetrically. The fore-nozzle  30  has individual sections  30   a ,  30   b ,  30   c ,  30   d ,  30   e ,  30   f , which are each arranged between two fins  40   a ,  40   b ,  40   c ,  40   d , two shaft bracket arms  11   a ,  11   b  or one fin  40   a ,  40   b ,  40   c ,  40   d  and one shaft bracket arm  11   a ,  11   b . The individual fore-nozzle sections  30   a ,  30   b ,  30   c ,  30   d ,  30   e ,  30   f  can be separate components or can also be formed in one piece, either partially or completely. In particular, the section  30   a , which is arranged between the two shaft bracket arms  11   a ,  11   b , can be formed as a detached, separate section, and thus as an independent nozzle segment, and the remaining fore-nozzle sections  30   b  to  30   f  can be formed as an individual, cohesive component. The section  30   b  is arranged between the shaft bracket arm  11   b  and the fin  40   d , the fore-nozzle section  30   c  is arranged between the fin  40   d  and the fin  40   c , the fore-nozzle section  30   d  is arranged between the fin  40   c  and the fin  40   b , the fore-nozzle section  30   e  is arranged between the fin  40   b  and the fin  40   a , and the fore-nozzle section  30   f  is arranged between the fin  40   a  and the shaft bracket arm  11   a  and is fastened to each of hem. 
     The shaft bracket arms  11   a  and  11   b  are also provided with a hydrofoil profile. In particular the inner part  111  of the shaft bracket arms  11   a ,  11   b  is thereby provided with a hydrofoil profile. The inner part  111  is that part of the shaft bracket arms  11   a ,  11   b , which is arranged inside, that is, in the interior of the fore-nozzle  30 . On principle, however, the outer parts  112  of the shaft bracket arms  11   a ,  11   b , that is, the parts of the shaft bracket arms  11   a ,  11   b , which are arranged outside of the fore-nozzle  30 , can be equipped with a hydrofoil profile, at least in part, but also completely without a hydrofoil profile. 
     All of the shaft bracket arms  11   a ,  11   b  as well as all of the fins  40   a ,  40   b ,  40   c ,  40   d  extend radially from the shaft bracket  10  to the outside. The fore-nozzle  30  is arranged concentrically with the shaft bracket  10  or with the propeller shaft  12 , that is, the axis of rotation of the fore-nozzle  30  is located on the axis of the shaft bracket  10  or on the axis of the propeller shaft  12 , respectively. The two devices  20 , which are each located on the starboard side and on the portside of the central web  51 , are symmetrical to one another with respect to a vertical axis  511 , which is preferably arranged in the center of the vessel with respect to the transverse direction of the vessel, which, in the example at hand, is formed by the central axis of the central web  51 . In particular, the fins and shaft bracket arms are arranged symmetrically to one another with respect to the vertical axis  511 . The device  20  is held on the hull  50  by means of the two shaft bracket arms  11   a ,  11   b . Forces acting on the devices  20  are thus also transferred to the hull  50  via the shaft bracket arms  11   a ,  11   b.    
       FIG. 2  shows a similar embodiment as compared to the embodiment from  FIG. 1 . In contrast,  FIG. 2  has only two fins  40   a ,  40   b , for each device  20 , instead of four fins. Apart from that, the arrangement  100  from  FIG. 2  is formed so as to be identical to the arrangement from  FIG. 1 . To get to the embodiment of  FIG. 2 , the fins  40   b  and  40   d  would need to be omitted in each device  20  in  FIG. 1 . Accordingly, the fins  40   a  and  40   b  of  FIG. 2  are fins, which have an inner part  401  as well as an outer part  402 . As compared to the embodiment from  FIG. 1 , the shaft bracket arms  11   a ,  11   b  are unchanged, as well. In particular, the angular distance β between the shaft bracket arms is also identical as compared to the embodiment from  FIG. 1 . In this embodiment, as in the embodiment from  FIG. 1 , all of the fins  40   a ,  40   b  each also have a hydrofoil profile across their entire length. 
     The embodiment according to  FIG. 3  is similar to the embodiment according to  FIG. 1 , wherein, in contrast to the embodiment from  FIG. 1 , the fins  40   c  and  40   d  in  FIG. 3  each only have an inner part  401 . That is, the fins  40   c ,  40   d  run from the shaft bracket  10  to the fore-nozzle  30 , whereas the fins  40   a ,  40   b  run from the shaft bracket  10  to the fore-nozzle  30  and protrude outwards beyond the latter. In particular, the fins  40   a ,  40   b  have an inner part  401  as well as an outer part  402 , whereas the fins  40   c  and  40   d  only have an inner part  401 . The angular distances α of the fins  40   a ,  40   b ,  40   c ,  40   d  among one another and to the shaft bracket arms  11   a ,  11   b  are identical to those from  FIG. 1 . Likewise, the angular distance β between the shaft bracket arms  11   a ,  11   b  is identical as compared to  FIG. 1 . 
       FIG. 4  shows an embodiment, which is similar to the illustration from  FIG. 1 . In contrast to the embodiment alternative from  FIG. 1 , in the embodiment alternative according to  FIG. 4  only an outer part  402  is provided in the case of fin  40   a . All other fins  40   b ,  40   c ,  40   d  have an inner part  401  as well as an outer part  402 . The fin  40   a  thus starts at the fore-nozzle  30  and runs all the way to its free end  403 . Apart from that, the positioning of the fins as well as of the shaft bracket arms  11   a ,  11   b  is identical with the embodiment from  FIG. 1 . 
     The embodiment according to  FIG. 5  is also similar to that from  FIG. 1 . In contrast to the embodiment alternative from  FIG. 1 , the embodiment alternative according to  FIG. 5  only has three fins, namely the fins  40   a ,  40   b  and  40   c . As compared to the embodiment from  FIG. 1 , the fin  40   c  would need to be omitted in  FIG. 1 , so as to get to the fin arrangement from  FIG. 5 . Accordingly, the fins  40   a ,  40   b  and  40   c  from  FIG. 5  each have an inner part  401  as well as an outer part  402 . In the case of the embodiment alternative of  FIG. 5 , a further difference to the embodiment alternative of  FIG. 1  is that the fore-nozzle  30  is not formed so as to be closed across its circumference. In the case of the other above-mentioned alternatives of  FIG. 1  to  FIG. 4 , the fore-nozzle  30  is formed so as to be completely closed across the circumference. According to  FIG. 5 , no fore-nozzle segment or no nozzle jacket, respectively, runs between the fin  40   c  and the fin  40   b . A lower region of the fore-nozzle  30 , which is smaller than half of the (imaginary) total nozzle circumference, is thus formed so as to be open. This open embodiment of the fore-nozzle can also be combined with other embodiment alternatives of the fins and/or of the shaft bracket arms. 
     The fore-nozzle  30  thus consists only of the fore-nozzle sections  30   a  located between the shaft bracket arms  11   a  and  11   b , the fore-nozzle section  30   b  located between the shaft bracket arm  11   b  and the fin  40   c , the fore-nozzle section  30   c  located between the fin  40   b  and the fin  40   a , and the fore-nozzle section  30   d  located between the fin  40   a  and the shaft bracket arm  11   a . All other embodiment features, in particular the arrangement of the fins  40   a ,  40   b ,  40   c  provided in  FIG. 5  and of the shaft bracket arms  11   a ,  11   b , are identical as compared to the embodiment from  FIG. 1 . 
     Just like in  FIG. 1 , the device  20  in the case of the embodiment alternative of  FIG. 6  comprises two shaft bracket arms  11   a ,  11   b . In the case of  FIG. 6 , the difference to the embodiment alternative of the arrangement  100  according to  FIG. 1  is that only a single fin  40   a  is provided and that a fore-nozzle  30  in the form of the nozzle section  30   a , which forms a single nozzle segment, is provided only between the fin  40   a  and the shaft bracket arm  11   a . Apart from that, no further fore-nozzle segments or fore-nozzle sections are provided. The fin  40   a  has an inner part  401 , which runs from the shaft bracket  10  to the fore-nozzle  30 , and an outer part  402 , which runs from the fore-nozzle  30  to a free end  403 . 
     The above-mentioned exemplary embodiments fall under the second embodiment alternative of the arrangement according to the invention, which is described in the description above, in the case of which the device comprises a fore-nozzle and at least one fin each, which is formed as a hydrofoil. In contrast, the embodiment alternative described below, which is illustrated in  FIG. 7 , falls under the first embodiment alternative of the arrangement according to the invention, which is described in the description above, in the case of which at least one shaft bracket arm is formed as a hydrofoil of the device, and wherein no further hydrofoils are provided, in particular no further hydrofoils, which are formed as fins, in addition to the shaft bracket arm. 
     Just as is shown in  FIGS. 1 to 6 ,  FIG. 7  shows a rear view onto a hull  50  with a central web  51 , on both sides of which a shaft bracket  10  each with a propeller shaft  12  mounted therein is provided. The shaft brackets  10  as well as three shaft bracket arms  11   a ,  11   b ,  11   c  each form a device  20  for reducing the drive power requirement of a twin screw vessel. The shaft brackets  10  are fixedly connected to the hull  50  via the shaft bracket arms  11   a ,  11   b ,  11   c . The shaft bracket arms  11   a ,  11   b ,  11   c  stick out radially from the shaft bracket  10  and are fastened to the shaft bracket  10  with one end and to the hull  50  with the other end. In the embodiment at hand, all three shaft bracket arms  11   a ,  11   b ,  11   c  are provided with a hydrofoil profile, that is, all of them represent a hydrofoil of the device  20 . Beyond that, no further hydrofoils are provided, in particular no fins. In this embodiment, no fore-nozzle is provided, either. The shaft bracket arms  11   a ,  11   b ,  11   c  as well as the shaft brackets  10  can be formed according to the embodiments from  FIGS. 1 to 6 . In the case of an embodiment according to  FIG. 7 , a symmetry of the two devices  20  with respect to the vertical axis  511  is at hand. Fundamentally, a symmetrical, in particular an axially symmetrical embodiment (viewed with respect to a vertical axis) of the two devices is preferred, regardless of a certain embodiment, because, viewed in longitudinal direction, the two vessel hull halves are on principle formed symmetrically in the case of most of the twin screw vessels. 
       FIGS. 8A and 8B  show a device  20  in a side view ( FIG. 8A ) as well as in a perspective view ( FIG. 8B ) at an incline from the front. The device  20  is formed similarly to the device from  FIG. 3 , that is, with two shaft bracket arms, a nozzle ring  30 , which is closed completely across the circumference, two fins  40   a ,  40   b , which have an inner part  401  as well as an outer part  402 , as well as two further fins  40   c ,  40   d , which only have an inner part  401 . The device  20  furthermore has a shaft bracket  10 , in which a propeller shaft  12  is mounted. The shaft bracket has a rear end  101  as well as a front end  102 . As can be seen in  FIG. 8A , the device  20  or in particular the fore-nozzle  30 , respectively, is arranged significantly closer to the rear end  101  than to the front end  102 . Viewed in their transverse expansion in travel direction of the vessel, the fins  40   a ,  40   b ,  40   c ,  40   d  are slightly shorter than the fore-nozzle  30 , so that a piece of the fore-nozzle protrudes beyond each fin in the contact region between fins  40   a ,  40   b ,  40   c ,  40   d  and the fore-nozzle  30  in the front and in the rear direction. In contrast, viewed in travel direction of the vessel, the shaft bracket arms  11   a ,  11   b  are longer than the fore-nozzle, so that the shaft bracket arms  11   a ,  11   b  stick out forwards and backwards beyond the fore-nozzle (see in particular  FIG. 8A ). The fore-nozzle  30  from the illustration of  FIGS. 8A and 8B  consists of three separate nozzle segments  301 ,  302 ,  303 , which are combined to form a circumferentially closed nozzle ring  30 . The nozzle segment  301  is arranged between the shaft bracket arms  11   a  and  11   b  and is fastened thereto. With its one side, the nozzle segment  302  is connected to the shaft bracket arm  11   b  and with its other end it is connected to the further nozzle segment  303  on the joint  304 . On the joint  304 , the nozzle segment  303  is connected to the nozzle segment  302  and to the shaft bracket arm  11   a  with its other end. 
     Viewed in travel direction of the vessel, downstream from the device  20 , a propeller  13  is provided, which is driven by the propeller shaft  12 . The propeller  13  directly adjoins the rear end  101  of the shaft bracket  10 . The fore-nozzle  30  has a smaller diameter than the propeller  13 . For example, the diameter of the fore-nozzle can be less than 90%, preferably less than 75%, more preferably less than 60% of the propeller diameter. The fins, in particular the fins  40   a ,  40   b  (with inner and outer part  401 ,  402 ), have a smaller length than half of the propeller diameter. Viewed further downstream from the propeller  13  in travel direction of the vessel, a rudder  60  is provided. A skeg  52 , which is fixedly connected to the hull  50 , follows above the rudder  60 . As can in particular be seen in  FIG. 8A , the propeller  13  or the propeller hub thereof, respectively, is arranged at a certain distance d 1  to the rudder  60 . 
     The embodiment according to  FIGS. 9A and 9B  is configured similarly to the embodiment from  FIGS. 8A and 8B . In particular, the device  20  and the corresponding components, shaft bracket arms  11   a ,  11   b , shaft bracket  10 , fore-nozzle  30  as well as fins  40   a ,  40   b ,  40   c ,  40   d  are formed identically. The only difference between the embodiments according to  FIGS. 9A and 9B  on the one side and between  FIGS. 8A and 8B  on the other side is that in the case of the embodiment according to  FIGS. 9A and 9B , the rudder  60  has a propulsion bulb  61 . The distance d 2  between the leading edge  611  of the propulsion bulb  61  and the propeller hub  131  is significantly smaller than the distance d 1  in the embodiment according to  FIGS. 8A and 8B  without a propulsion bulb. 
       FIGS. 10A and 10B  show an enlarged, perspective view of a shaft bracket  10 . In the case of the illustration in  FIG. 10A , two shaft bracket arms  11   a ,  11   b  as well as four fins  40   a ,  40   b ,  40   c  and  40   d  are illustrated, which are each fastened to the shaft bracket  10  with one of their ends. For the sake of clarity, further component parts or components, respectively, of the device have been omitted. In particular, a fore-nozzle has been omitted in the present illustration. The illustrations of  FIG. 10A  and  FIG. 10 b    are perspective illustrations, wherein regions of the individual components, which are not visible, are illustrated with dashed lines.  FIG. 10B  shows the same view as  FIG. 10A , wherein  FIG. 10B  only shows the shaft bracket  10   a  as well as the shaft bracket arm  11   a , and wherein, for the sake of clarity, the further shaft bracket arm  11   b  as well as the fins  40   a ,  40   b ,  40   c ,  40   d  have been omitted. It can be seen from the view of  FIG. 10A  that the fins each have a hydrofoil profile with a rounded suction side  404  as well as a flat or flatter pressure side  405 . It can also be seen that the shaft bracket arms  11   a ,  11   b  have a rounder or more curved suction side  113  as well as a flatter or flat pressure side  114 . It can further be seen that the fins  40   a ,  40   b ,  40   c ,  40   d  as well as the shaft bracket arms  11   a ,  11   b  are formed so as to be entwined or twisted, respectively. It can further be seen that the shaft bracket arms  11   a ,  11   b  as well as the fins  40   a ,  40   b    40   c ,  40   d  have an angle of attack as compared to the flow direction of the water  14 . The angle of attack γ is thereby formed by the angle between the chord  115  of the shaft bracket arm profile or of the chord  406  of the fin profile, respectively, on the one side and the water flow direction  14  on the other side.