FI127797B

FI127797B - Propulsion bracket

Info

Publication number: FI127797B
Application number: FI20175051A
Authority: FI
Inventors: Oskar Levander
Original assignee: Rolls Royce Marine As
Priority date: 2017-01-20
Filing date: 2017-01-20
Publication date: 2019-02-28
Also published as: FI20175051L

Abstract

Various aspects provide for a bracket configured to couple first and second propeller apparatus. A bracket may increase the stiffness of a propulsion apparatus. A bracket may be angled to form a truss with the hull. A bracket may comprise one or more pitched portions. A pitched portion may be located proximate to a propeller (e.g., ahead of or behind the propeller) and have a pitch configured to generate an anti-swirl thrust with respect to a swirl thrust generated by the proximate propeller. The anti-swirl thrust may counterbalance the swirl thrust, increasing the relative fraction of motive thrust to nonmotive thrust.

Description

PROPULSION BRACKET

20175051 prh 06 -11- 2018

BACKGROUND

1. Technical Field [0001] The present invention relates generally to marine propulsion, and more particularly to mounting propulsion systems, such as propellers.

2. Description of Related Art [0002] A desire to combine improved performance with reduced environmental impact and lower cost requires a range of technology improvements. In shipping, a propulsion 10 system typically comprises a propeller or similar vaned apparatus, driven by an engine or motor to generate thrust. As the propeller rotates, a portion of the propulsion energy is converted into useful motive thrust (e.g., forward thrust or backward thrust). A portion of the energy is typically converted into non-motive thrust, such as swirl thrust, eddies, and the like. It is typically desirable to reduce non-motive thrust and maximize motive thrust.

[0003] Technology directed toward improving efficiency, reducing emissions, and the like often add to production costs and may reduce reliability. However, an increasing focus on reducing environmental impact raises the importance of energy efficiency. As such, an apparatus that increases efficiency without decreasing reliability is desirable. Cost of implementation is often a barrier. Technology that provides a more cost-effective solution may enable the commercialization of technology that might otherwise be economically undesired by the market.

[0004] A pre-swirl stator may improve efficiency, as described in On the Design and Analysis of Pre-Swirl Stators for Single and Twin Screw Ships. (Zondervan, Gert-Jan et. al., Second Int.'l Symp. on Marine Propulsors, smp'll, Hamburg, Germany, June 2011), 25 incorporated by reference herein.

SUMMARY [0005] The invention is described in the claims. A ship may comprise one or more mounts and/or brackets configured to couple propulsion apparatus, such as propeller apparatus, to each other and/or to various parts of the ship. A mount and/or bracket may be disposed ahead of a propeller or behind the propeller. A ship may have a beam greater than 5 meters, including greater than 8 meters. The ship may have a hull, a first propeller apparatus, and a second propeller apparatus. A first apparatus may comprise a first propeller with a first rotation direction and having a first hub and a first mount coupling the first propeller to the hull. A second apparatus may comprise a second propeller with a second rotation direction and having a second hub and a second mount coupling the second propeller to the hull. The rotation directions may be the same or different. A propeller may be coupled to the ship with a mount (e.g., via a hub or shroud of the propeller).

[0006] A bracket (e.g., a first bracket) may couple the first propeller to the second propeller, particularly by at least one of the first and second mounts, the first and second hubs, and the hub of one propeller to the mount of another propeller. In some cases, a bracket couples a propeller apparatus directly to the hull. A bracket may be disposed ahead of and/or aft of a propeller. A ship may comprise a rudder. A propeller may be disposed ahead of the rudder or aft of the rudder. In an embodiment, a rudder is disposed directly aft of a propeller.

[0007] A ship may comprise a skeg, which may be integrated with a mount or may be separate from a mount. A bracket may couple a propeller apparatus to the skeg, particularly via a hub of the propeller. A ship may have a skeg coupled to two or more propellers. A first bracket may couple a first propeller to a skeg, particularly via a first hub. A second bracket may couple a second propeller to the skeg, particularly via the second hub.

[0008] A mount and/or bracket may comprise one or more pitched portions. A pitched portion may be shaped to generate an anti-swirl thrust with respect to a corresponding swirl thrust generated by the local propeller pitch angle proximate to the pitched portion of the mount/bracket. This shape may include an angle of the pitched portion and/or a camber of the pitched portion. In some cases, a mount and/or bracket has a first pitched portion proximate to (e.g., directly in front of or directly behind) a first propeller, and a second pitched portion proximate to a second propeller.

[0009] A camber and/or an angle of the pitched portion with respect to water flowing past the pitched portion may be chosen according to an expected set of operating conditions (e.g., ship speed, propeller rotation speed, flow volume, and the like). Typically, increasing a camber or an angle of the pitched portion (to increase anti-swirl thrust) increases hydrodynamic drag. As such, a camber, angle, and/or combination thereof may be chosen that optimizes the tradeoff between an increased camber/angle (decreasing the non-motive swirl thrust, but increasing drag) and decreased camber/angle (less anti-swirl thrust, but lower drag).

[0010] A ship may comprise three or more propellers (e.g., coupled by two or more brackets). In some embodiments, a ship comprises at least first, second, and third propeller apparatus. The first and second apparatus may be coupled by a first bracket. The second and third apparatus may be coupled by a second bracket. In some cases, a propeller (e.g., the second propeller) may be coupled to the ship via a skeg. Other apparatus may be coupled to the skeg and/or other parts of the propeller apparatus.

[0011] Additional mounts and/or brackets may comprise their own respective pitched portions. A third bracket may comprise its own respective pitched portion/s). In some cases, a third pitched portion proximate to the second propeller is shaped to generate an antiswirl thrust opposite the corresponding swirl thrust of the second propeller, and a fourth pitched portion proximate to the third propeller is shaped to generate an anti-swirl thrust opposite the corresponding swirl thrust of the third propeller.

[0012] A ship may have at least three propellers coupled by at least two brackets via a skeg (e.g., mounting the middle propeller). For first, second, and third propeller apparatus, the second mount may comprise the skeg. The first bracket may couple the first propeller to the skeg, particularly via the first hub. The second bracket may couple the third propeller to the skeg, particularly via the third hub.

[0013] In a particular embodiment, a ship comprises first, second, and third propeller apparatus, each having an associated propeller, hub, and mount. The mount of the second (e.g., centrally located) propeller comprises a skeg. A first bracket couples the first hub of the first propeller to the skeg, and a second bracket couples the third hub of the third propeller to the skeg. One or more of the brackets may have one or more pitched portions. For example, the first bracket may have first and second pitched portions shaped to generate antiswirl thrusts to counteract the swirl thrusts generated by the first and second propellers, respectively. The second bracket may have third and fourth pitched portions, shaped to generate anti-swirl thrusts to counteract the swirl thrusts generated by the second and third propellers, respectively.

[0014] A propeller may comprise a large area propeller (LAP). An LAP may have a diameter that is greater than 60%, including greater than 80%, including greater than 90%, including greater than 100% of a draft of the ship. A large area propeller may increase efficiency (e.g., by imparting equivalent thrust at lower rpm as compared to a smaller radius propeller).

[0015] In some embodiments, two or more brackets (e.g., each having a corresponding pitched portion) couple a propeller apparatus to the hull. Mounts and/or brackets may be angled (e.g., joined at angles other than 90 degrees) to form a truss structure.

BRIEF DESCRIPTION OF THE DRAWINGS [0016] FIGS. 1A and IB schematically illustrate a bracket, according to some embodiments.

[0017] FIGS. 2A and 2B schematically illustrate brackets having pitched portions, according to some embodiments.

[0018] FIGS. 3A and 3B schematically illustrates an exemplary propeller and associated pitched portion of a proximate bracket and/or mount, according to some embodiments.

[0019] FIG. 4 is a schematic illustration of a portion of a ship having three propellers, according to some embodiments.

[0020] FIG. 5 is a schematic illustration of a portion of a ship having three propellers, according to some embodiments.

[0021] FIG. 6 is a schematic illustration of a view of the starboard side of a ship, according to some embodiments.

[0022] FIG. 7 schematically illustrates an embodiment having one propeller, according to some embodiments.

[0023] FIGS. 8A and 8B illustrate a portion of a ship having three propellers, according to some embodiments.

DETAILED DESCRIPTION [0024] A ship may comprise a propeller and its associated apparatus. A propeller apparatus may locate and/or drive the propeller, and may include a hub around which the propeller rotates. A propeller apparatus may include a shroud around the propeller (e.g., with a rim drive). The propeller apparatus may comprise a mount and/or skeg coupling the propeller to a hull of the ship. The mount may be integrated with and/or connected to the hub and/or shroud, such that the mount locates the propeller at a particular location with respect to the hull. A propeller/hub combination may comprise a so-called pod configuration.

[0025] A ship may have two or more propellers and one or more brackets. A pair of propeller apparatus may be coupled by a bracket. A bracket may couple a propeller apparatus (e.g., a hub, mount, shroud, or other part of the propeller apparatus) to a hull, a skeg, and/or to another propeller apparatus. The bracket may provide for horizontal stabilization and/or stiffness of the propeller apparatus. A bracket may horizontally connect two propeller apparatus, such that horizontal loads may be transferred between the propeller apparatus. A bracket may be located ahead of or aft of a propeller. A bracket may connect a propeller apparatus to a skeg (e.g., via a hub, shroud, or mount of the propeller).

[0026] A bracket may comprise a pitched portion having a specific hydrodynamic orientation. A pitched portion may comprise a blade having an angle that, during propulsion, imparts an anti-swirl thrust to water passing by the pitched portion. A pitched portion may have a camber that imparts an anti-swirl thrust. The anti-swirl thrust is typically directed opposite an expected swirl thrust generated by the propeller close to (e.g., just ahead of or just behind) the pitched portion. By counteracting the propeller's swirl thrust with the pitched portion's anti-swirl thrust, the net non-motive thrust of the propeller may be reduced.

[0027] FIGS. 1A and IB schematically illustrate a bracket, according to some embodiments. FIG. 1A illustrates a ship 100 having two propellers in a co-rotating configuration. FIG. IB illustrates a ship 101 having two propellers in a counter-rotating configuration. Additional propellers and brackets may be added.

[0028] A ship may have a hull 110 having a beam 101. In some implementations, the beam may be greater than 5 meters, greater than 8 meters, or even greater than 12 meters. A ship may have two or more propellers 120,122, which in some implementations are located by and driven around respective hubs 130,132. Mounts 140,142 may attach the respective propellers 120,122 to the ship (e.g., via their hubs or shrouds, as the case may be). A mount may comprise an axle, bearing, and/or other drive mechanism to rotate the propeller.

[0029] In exemplary ship 100, mounts 140 and 142 are canted by an angle 410 with respect to the hull. For some ships an angle 410 may generally be less than or greater than zero degrees (e.g., 2-30 degrees, including 5-20 degrees), such that lateral forces may be transferred from the propeller to the hull with a reduced bending moment on the mount. In exemplary ship 101 (FIG. IB), mounts 140 and 142 are substantially orthogonal to the hull surface, with an equivalent of angle 410 at zero degrees.

[0030] Although hub-driven propellers are illustrated in this example, a rim-driven propeller may comprise a shroud that drives and locates the propeller. The shroud may be similarly implemented with a bracket, mutatis mutandis.

[0031] A first propeller 120 may have a first rotation direction 150. A second propeller 122 may have a second rotation direction 152. Rotation directions 150,152 may be the same, forming a co-rotating pair of propellers, as in FIG. 1A. Rotation directions 150,152 may be opposite, forming a counter-rotating pair of propellers, as in FIG. IB.

[0032] Typically, mounts 140,142 locate the propellers vertically and horizontally with respect to the ship. As viewed in cross section (longitudinally), a mount may comprise a substantially triangular cross section, which may reduce lateral movement of the propeller/hub). However, mounts 140,142 may be substantially longer in the vertical direction than they are wide, particularly when propeller diameter increases (e.g., to over 50%, or even over 80% of a draft of the ship). This length may reduce lateral stiffness of the mount. A decrease in stiffness of the mount may be mitigated by an increased angle 410, and vice versa.

[0033] A bracket 160 may couple and/or connect the propellers, typically via their respective hubs or shrouds. Bracket 160 may provide for the transmission of horizontal forces between the propeller apparatus, increasing the aggregate horizontal stiffness of the propulsion system. In some embodiments, the hull, mounts, propellers, and bracket may be designed to form a truss structure (particularly with nonzero angles 410). A truss structure may increase stiffness of the propulsion system while reducing weight and hydrodynamic resistance. By forming a truss structure with the hull, the truss members (mounts 140,142 and bracket 160) may be made thinner (reducing drag) yet still locate the propellers with a desired tolerance.

[0034] Whereas unconnected propellers might require that each individual mount 140,142 meet a required location and stiffness tolerance, an apparatus comprising two or more propellers coupled by one or more brackets 160 may have lower weight and reduced hydrodynamic resistance, yet still provide the required mechanical properties. By connecting the apparatus of the propellers with bracket 160, the mechanical and hydrodynamic performance of the propellers may be optimized in combination.

[0035] FIG. IB illustrates a skeg, according to some embodiments. A ship may comprise one or more skegs 141. A skeg may include a stiff, thick (over 30 cm, including over 80cm) steel structure, typically oriented longitudinally, and often centrally located with respect to port and starboard. A skeg may comprise a structural steel backbone that reinforces the ship. In some implementations, a propeller apparatus is coupled to a skeg (e.g., via a bracket). In FIG. IB, a first bracket 160 connects propeller 120 to skeg 141 (in this case, via hub 130) and a second bracket 160' connects propeller 122 to skeg 141 (in this case, via hub 132). A mount and skeg may be integrated. Two propeller apparatus may be coupled by a single bracket. Two propeller apparatus may be coupled by multiple brackets.

[0036] FIGS. 2A and 2B schematically illustrate brackets having pitched portions, according to some embodiments. FIG. 2A illustrates a ship 200 having a co-rotating pair of propellers. In FIG. 2A, the propeller apparatus in ship 200 include shrouds 131 around the propellers (which do not include rim-drives; in some cases a shroud may comprise a rim-drive to drive the propeller). An optional center skeg 141 is shown.

[0037] FIG. 2B illustrates a ship 201 having a counter-rotating pair of propellers. In FIG. 2B, the propellers are mounted to the hull via skegs 141 and 143.

[0038] A pitched portion may comprise a shape (e.g., a blade), an angle, a camber, and/or a curvature chosen to deflect water flowing past the portion in a direction that reduces the net non-motive thrust of the propulsion system. Typically, a pitched portion is shaped and disposed proximate to a corresponding part of the propeller (having a shape that generates a swirl thrust) and the pitched portion is correspondingly shaped to generate a complementary anti-swirl thrust.

[0039] A pitched portion may be located immediately ahead of or behind a propeller. According to an expected swirl thrust generated by the propeller (as it passes ahead of or behind the pitched portion), the pitched portion may be designed to generate an anti-swirl thrust to counterbalance the proximate swirl thrust.

[0040] A bracket 260 may comprise one or more pitched portions. In FIGS. 2A and 2B, the brackets have pitched portions associated with each respective propeller. A bracket may have a pitched portion for only one of the propellers. In FIGS. 2A and 2B, a first pitched portion 270 proximate to the first propeller 120 may be configured to generate a first anti-swirl thrust 280. A second pitched portion 272 proximate to the second propeller 122 may be configured to generate a second anti-swirl thrust 282. Inasmuch as the relevant interacting flow fields are relatively localized, the configuration each pitched portion is chosen according to the rotation, angle, shape, speed, and other design factors of the propeller with which the pitched portion interacts.

[0041] FIGS. 3A and 3B schematically illustrate an exemplary propeller and associated pitched portions of a proximate bracket/mount, according to some embodiments. FIG. 3A illustrates anti-swirl generated via an angle of the pitched portion. FIG. 3B illustrates anti-swirl generated via a camber of the pitched portion. FIGS. 3A and 3B are schematic for illustrative simplicity. A typical propeller may have a propeller pitch angle and/or camber that varies with radius (e.g., to yield a constant advance). A typical propeller will generally not be absolutely planar. A propeller pitch angle may vary from about 30-70 degrees at the root of the blade to below 25 degrees (e.g., about 5-20 degrees) at the tip of the blade. FIGS. 3A and 3B show simplified sections for illustrative ease.

[0042] A propeller 120 may have a propeller pitch angle 310 (including a variation in pitch over radial distance, and/or a variable pitch propeller) chosen according to various propulsion parameters, such as ship size, hull shape, propulsion power, propeller size, rotation speed, and the like.

[0043] A mount and/or bracket typically has at least some nonplanarity (e.g., a foil shape). Typically, a pitched portion has an angle and camber that are combined to yield a desired amount of anti-swirl thrust without creating excess drag. Pitched portion 270/272 of a bracket/mount may have an angle 320 (FIG. 3A) and/or camber 330 (FIG. 3B) that is chosen in combination with various propeller parameters (e.g., propeller pitch angle 310). A larger camber or angle 320 increases anti-swirl thrust, but also increases drag. Typical computational methods (finite element analysis and/or computational fluid dynamics simulations) may be used to choose an appropriate angle/camber according to (inter alia) local propeller shape and pitch angle 310, that reduces nonmotive thrust (thus increasing motive thrust) yet does not overly drag.

[0044] The respective aft 302 and fore 304 directions of the ship are shown. In this example, the pitched portion 270/272 of (in this case) bracket 260 (FIG. 2A/B) is disposed ahead of propeller 120, and propeller 120 moves upward for forward motion.

[0045] During forward steaming, propeller 120 typically generates a swirl thrust 151. The pitched portion 270/272 of the bracket (and/or mount) may generate a corresponding anti-swirl thrust 280/282, which may negate at least a portion of the swirl thrust 151, resulting in a lower net swirl thrust 151' downstream of the propeller. As a result, the flow stream behind the propeller may have a relatively reduced swirl component (than it would have without the pitched portion generating anti-swirl thrust). Anti-swirl thrust may be generated via an appropriate choice of angle 320 (FIG. 3A) and/or camber 330 (FIG. 3B), which may be chosen according to the expected local swirl thrust generated by the propeller. In some embodiments, angle and camber are combined to generate anti-swirl thrust. Angle and/or camber may vary radially (e.g., to match the local anti-swirl thrust to the corresponding local swirl thrust generated by the propeller). An angle 320 of a pitched portion may be between about 40 degrees and about 90 degrees. An exemplary camber 330 (e.g., an upper camber, FIG. 3B) may be between about 10% and 30%, including about 15% to about 25%, of a chord 340.

[0046] Typically, angle 320 varies inversely with propeller pitch angle 310. For example, a propeller may have a propeller pitch angle 310 that varies from about 30-70 degrees, including 35-60 degrees (e.g., 40 - 55 degrees) at the hub to below 25 degrees, including below 10 degrees, including about 5-20 degrees at the tip. An exemplary angle 320 (at a particular radius) may be calculated by subtracting propeller pitch angle 310 at that radius from 90 degrees (e.g., within 10% of this angle, including within 5% of this angle). For example, angle 320 may vary from about 65 to 20 degrees, (including 60 to 30 degrees) proximate to the hub of propeller 120 to about 85-65 degrees proximate to the tip of propeller 120.

[0047] Typically, at a given radius, the angle/camber is chosen such that the antiswirl thrust counteracts the locally generated swirl thrust of the propeller (at that particular propeller pitch angle) without unduly increasing drag.

[0048] FIG. 4 is a schematic illustration of a portion of a ship having three propellers, according to some embodiments. A ship with three propellers may comprise a corotating pair and/or a counter-rotating pair of propellers. In this example, ship 400 has three propellers 120,122, and 124 that rotate in the same direction (150,152,154, respectively). In this example, hub 132 is mounted via a mount comprising a skeg 131, respective hubs 130 (propeller 120) and 132 (propeller 122) are connected by bracket 160, and respective hubs of propellers 132 and 134 are connected by bracket 460.

[0049] By coupling the propeller apparatus to form a truss structure, the shape and orientation of the propeller mounts may be improved. In FIG. 4, mounts 140 and 144 are canted to form an angle 410 that is greater than zero degrees. The distance between the structural centers of mounts 140 and 144 may be greater than or less than the distance between the centers of propellers 120 and 124. Such a structure may enable the use of thinner, more hydrodynamic mounts, yet still provide the required stiffness for effective propeller mounting. Canted mounts may also be implemented with embodiments other than shown in FIG. 4.

[0050] FIG. 5 is a schematic illustration of a portion of a ship having three propellers, according to some embodiments. In this example, propellers 120 and 122 rotate in the same direction (150,152, respectively) and propeller 124 rotates in the opposite direction (154, respectively). Propellers 120/122 form a co-rotating pair, and propellers 122/124 form a counter-rotating pair.

[0051] A ship having three propellers may have a bracket having a pitched portion and a bracket without a pitched portion. In this example, both brackets have pitched portions, and each bracket has pitched portions for both of its respective propellers. Bracket 260 connects hubs 130 and 132, and has respective pitched portions 270 and 272 proximate to propellers 120 and 122, respectively. Bracket 560 connects hubs 132 and 134, and has respective pitched portions 274 (proximate to propeller 122) and 276 (proximate to propeller 124).

[0052] A ship may comprise an integrated mount and skeg, as illustrated in FIGS. 2B, 4 and 5, in which a propeller is coupled to the hull via a skeg. A ship may comprise a central skeg and propeller, with outer propellers 130 and 134 coupled to the skeg via their respective brackets. A ship may comprise one or more outer skegs coupling respective propeller(s) to the hull (e.g., a twin skeg configuration).

[0053] FIG. 6 is a schematic illustration of a view of the starboard side of a ship, according to some embodiments. In this example, ship 600 comprises a propeller 120 ahead of a rudder 620. Rudder 620 may be disposed ahead of transom 610 of the ship, such that both the rudder and propeller are substantially beneath the aft portion of the ship. In this example, a bracket 260 is disposed ahead of propeller 120. In some implementations, a propeller may have a diameter that is greater than 50%, greater than 80%, greater than 90%, or even greater than 100% of the draft 601 of the ship.

[0054] FIG. 7 illustrates an embodiment having one propeller, according to some embodiments. A ship 700 may comprise a propeller 120 coupled to a hull 110 via a mount 140. In this example, the propeller comprises a hub 130. In some implementations, a propeller may comprise a shroud (e.g., with a rim drive) that locates and drives the propeller.

[0055] A first bracket 260 and second bracket 262 may stabilize the propeller. In this example, brackets 260, 262, mount 140, and hull 110 form a truss. Bracket 260 has a pitched portion 270 configured to generate an anti-swirl thrust. Bracket 262 has a pitched portion 272 configured to generate an anti-swirl thrust.

[0056] FIGS. 8A and 8B illustrates portions of a ship having three propellers, according to some embodiments. FIG. 8A is a schematic perspective illustration of a lower portion of the ship. FIG. 8B is a schematic illustration of a plan view of a portion of the ship bottom, looking upward. Exemplary ship 800 has three propellers - starboard, center, and port, of which the center propeller is mounted in a skeg.

[0057] In this example, starboard propeller 120 and center propeller 122 rotate in the same direction (150 and 152, respectively), and port propeller 124 rotates in the opposite direction. In this example, central hub 132 is integrated with skeg 141, starboard propeller 120 is coupled to the hull via a first mount 140 and a second mount 140', and port propeller 124 is coupled to the hull via a first mount 144 and a second mount 144'. The first and second mounts may be canted against each other. For example, first mounts 140/144 may contact the hull closer to their respective sides of the hull than the corresponding hubs to which they're mounted. Second mounts 1407144' may contact the hull farther from their respective sides (closer together) than their corresponding hubs. In some cases, a first mount is canted and a second mount is substantially orthogonal to the hull.

[0058] These exemplary propellers are coupled via brackets 260 (hub 130 to hub 132) and 560 (hub 132 to hub 134). Each of brackets 260 and 560 comprises pitched portions configured to generate an anti-swirl thrust proximate to its respective propeller. In this example, the port and starboard propellers comprise rudders. The center propeller may have a 5 rudder. A mount (e.g., 140,144) proximate to a propeller may include a pitched portion having an angle and/or camber configured to generate an anti-swirl thrust with respect to the swirl thrust generated by the propeller.

[0059] Various features described herein may be implemented independently and/or in combination with each other. An explicit combination of features does not preclude 10 the omission of any of these features from other embodiments. The above description is illustrative and not restrictive. Many variations of the invention will become apparent to those of skill in the art upon review of this disclosure. The scope of the invention should, therefore, be determined not with reference to the above description, but instead should be determined with reference to the appended claims along with their full scope of equivalents.

Claims

A vessel (100,101, 200, 201, 400, 500, 600, 800) having a hull (110) and a single width (101) greater than 5 meters, the vessel comprising a propulsion bracket configured to reduce the non-propelling vortex force, comprising :

A first propeller (120) having a first hub (130) and a first bracket (140) connecting the first propeller (120) to the hull (110), the first propeller (120) having a first direction of rotation (150), a second propeller (122) having a second hub (132) and a second bracket (142) connecting the second propeller (122) to the hull (110), the second

The propeller (122) has a second direction of rotation (152), characterized in that the vessel further comprises:

a third propeller (124) having a third hub (134) and a third bracket (144) connecting the third propeller (124) to the hull (110), the third propeller (120) having a third direction of rotation (154),

A first bracket (260) coupling the first propeller to the second propeller, the first bracket having:

a first angled portion (270) adjacent the first propeller and formed to generate a first vortex counterforce (280) opposed to a first vortex force generated by the first propeller; and

A second angled portion (272) adjacent to the second propeller and formed to generate a second vortex-resisting force (282) opposed to a second vortex force generated by the second propeller, and a second bracket (560) coupling the third propeller to the second propeller, the second bracket having:

A third angled portion (274) adjacent to the second propeller (122) and formed to generate a third vortex counterforce (284) opposite to the second vortex force generated by the second propeller (122), and a fourth angled portion (276) ) when the third propeller (124) and

Is formed to generate a fourth vortex-resisting force (286) which is opposite to the third vortex force generated by the third propeller (124).

The vessel of claim 1, wherein:

the first and second propellers (120,122) are coupled via the first bracket connecting the first and second brackets (140,142), and the second and third propellers (122,124) are coupled via the second bracket connecting the second and the third bracket (142,144).

The vessel of claim 1, wherein:

the first and second propellers (120,122) are coupled via the first bracket connecting the first and second hubs (130,132), and the second and third propellers (122,124) are coupled via the second bracket connecting the second and the third hub (132,134).

The vessel of claim 1, wherein:

the first and second propellers (120,122) are coupled via the first bracket connecting the hub of one of the first and second propellers to the bracket of the second of the first and second propellers, and the second and third propellers (122,124 ) are coupled via the second bracket, which connects the hub of one of the second and third propellers to the bracket of the other of the second and third propellers.

Vessel according to any of the claims 1 to 4, wherein at least one angled portion has an angle (320) which is within +/- 10% of an angle calculated by subtracting a propeller inclination angle (310) for the propeller adjacent this angled portion. from 90 degrees.

Vessel according to any of the claims 1-5, wherein:

the second bracket (142) comprises a sheath (141), the first bracket (160, 260) remains the first propeller (120) with the sheath (141), and the second bracket (360,460) connects the third propeller (124) to the sheath (141).

The vessel of claim 6, wherein:

the first bracket (160, 260) connects the first propeller (120) to the sheath (141) via the first hub (130), and the second bracket (360,460) connects the third propeller (124) to the sheath (141) via the third the hub (134).

Vessel according to any of the claims 1 to 7, further comprising a rudder (620) arranged in front of or behind at least one propeller.

A vessel as claimed in any of claims 1-8, wherein a propeller plane for at least one propeller (120, 122,124), in relation to a forward direction of the vessel, is at or in front of a transom (610) of the vessel.

The vessel of claim 9, wherein the propeller plane of the first and third propellers (120,124) is in front of the propeller plane of the second propeller (122).

Vessel according to any of the preceding claims 1-10, wherein:

the first propeller (120) is connected to the hull via at least two mounts (140,140 ') which are inclined towards each other, the third propeller (124) is connected to the hull via at least two mounts (144,144') which are inclined to each other, the second the bracket (142) comprises a sheath (141), and the vessel further comprises a first rudder disposed behind the first propeller and a second rudder disposed behind the third propeller.

A vessel according to any of the claims 1-11, wherein the second propeller 5 has a diameter greater than 80% of a depth of the vessel.

The vessel of claim 12, wherein the diameter is greater than 90% of the depth.

Vessel according to any of the claims 1-13, wherein at least one angled portion

10 comprises an angle (320) which, in relation to the adjacent propeller, varies from: about 65 to 20 degrees close to the hub of the propeller concerned, to about 85 to 65 degrees close to the tip of the affected propeller.

Vessel according to any of the claims 1-14, wherein at least one angled portion

15 includes a camber angle that provides the vortex counteracting force.