Domestic vessel

Abstract

To provide a domestic vessel loaded with a large propeller and a main engine with great output, and having improved steering.SOLUTION: A groove 10 having a shape in which a rising bottom portion T is scooped out in a longitudinal direction of a hull is provided, and a propeller 6 and a rudder 7 are arranged in this order from a bow side directly below the groove 10. A bottom surface 10a of the groove 10 approaches a draft WL side from the rising bottom portion T with a starting end located on a bow side of the propeller 6, and terminates by approaching the rising bottom portion T on a stern 1b side while straddling over the propeller 6 and the rudder 7. The propeller 6 is arranged directly below a position where the bottom surface 10a is most raised toward the draft WL side. A width of the groove 10 gradually becomes narrower from a position of the rudder 7 toward the stern 1b.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to coastal merchant ships that navigate in shallow waters, and in particular to coastal ships that accommodate large diameter propellers. [Background technology]

[0002] Patent Document 1 discloses a stern shape that allows for the accommodation of a large-diameter propeller to improve the propulsion efficiency of a vessel. According to this document, the stern shape has a wide area below the waterline, and the bottom of the vessel gradually rises toward the bow from there to the point where the propeller's maximum diameter is reached. The bottom gradually slopes downward from the propeller. Patent Document 2 discloses a technique for providing a wedge on the bottom of the stern. According to this document, the wedge is used to raise the stern. Furthermore, Patent Document 3 discloses a stern structure for a high-speed vessel that reduces wave-making resistance by accelerating the flow at the stern and streamlining the water flow behind the propeller. According to this document, a pair of fins are provided on the stern side on both sides of the extension line passing through the propeller shaft, accelerating the water flow discharged from the stern. Finally, Patent Document 4 discloses a trimaran with a polka-dot-shaped cutout in the bottom only in the propeller area (see Figure 5 of this document). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Utility Model Application Publication No. 56-4997 [Patent Document 2] Japanese Patent Application Publication No. 9-52591 [Patent Document 3] Japanese Patent Application Laid-Open No. 2006-51895 [Patent Document 4] Japanese Patent Application Publication No. 2023-128975 Summary of the Invention [Problem to be solved by the invention]

[0004] The technology of Patent Document 1 has a shape that gradually descends from the position of the propeller to the stern, which makes it possible to achieve the wedge effect shown in Patent Document 2. However, with the technology of Patent Document 1, the bottom of the ship gradually rises from the stern toward the bow, and is highest around the propeller, so it is necessary to provide fins facing into the water on both sides of the propeller to prevent air from flowing in from the sides.

[0005] The technology in Patent Document 1 aims to use a large propeller, but a shape in which the bottom of the ship at the position of the propeller is raised compared to the stern reduces buoyancy and stability, so there is a limit to the size of the main engine that can be installed.

[0006] The technology of Patent Document 3 does not have a shape in which the entire bottom of the vessel is hollowed out like Patent Document 1, and therefore cannot accommodate a large-diameter propeller. On the other hand, a pair of fins provided on the stern side sandwich the water flow discharged from the stern end on both sides to accelerate it, but the shape of the upper part of the stern end approaches the waterline as it moves towards the stern.

[0007] According to the technology of Patent Document 4, the bottom of the vessel is partially hollowed out only at the position of the propeller, ensuring buoyancy and making it suitable for mounting a large main engine. In addition, the polka-dot-shaped hollowed-out bottom of the vessel creates a wedge effect.

[0008] However, when a ship navigates in shallow waters, the distance between the ship's bottom and the seabed becomes smaller, causing the water flow to become faster only under the ship's bottom. This results in increased resistance, a decrease in speed, and poor steering effectiveness.

[0009] The present invention has been made in response to the above-mentioned conventional circumstances, and its object is to provide a coastal vessel that can be equipped with a large propeller and a main engine with high output, and that has improved steering effectiveness. [Means for solving the problem]

[0010] In order to achieve the above object, a transom-stern hull is provided, which has a bow bottom section that extends horizontally in a straight line from the bow to the middle of the hull, and a raised bottom section that is gradually shallower as it extends from the bow bottom section toward the stern, and a propeller and a rudder are provided within the raised bottom section, A groove is provided in the longitudinal direction of the hull, the bottom of the ascending vessel being hollowed out, The propeller and the rudder are arranged directly below the groove in this order from the bow side, The bottom surface of the groove starts on the bow side of the propeller, approaches the waterline from the rising bottom of the ship, straddles the propeller and the rudder, and ends by approaching the rising bottom of the ship at the stern side, and the propeller is located directly below the position where the bottom surface rises most in the waterline direction, The width of the groove is characterized by gradually narrowing from the position of the rudder to the stern. [Effects of the Invention]

[0011] In the coastal vessel of the present invention, the rudder is located midway along the groove that narrows from the propeller position to the stern, and since the rudder is located midway along this narrowing, it is possible to improve steering effectiveness, and therefore prevent a decrease in rudder effectiveness even when operating around shallow islands. [Brief explanation of the drawings]

[0012] [Figure 1] 1A and 1B show a coastal vessel according to the present embodiment, with FIG. 1A being a side view and FIG. 1B being a bottom view. [Figure 2] 2A and 2B are diagrams showing cross-sectional positions of the coastal vessel in FIG. 3, where FIG. 2A is a cross-sectional view at the y0 position, FIG. 2B is a cross-sectional view at the y1 position (skeg position), and FIG. 2C is a diagram with a portion covering the propeller removed. [Figure 3] 3A is a rear view (position x0), and FIGS. 3B to 3F are X cross sections at x1 to x5, respectively. [Figure 4]4A and 4B are diagrams showing the operation of the coastal vessel of this embodiment, in which FIG. 4A is a bottom view and FIG. 4B is a view showing the water flow at the bottom of the vessel as seen from the side of the skeg. [Figure 5] 1 shows a coastal vessel according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] [Example 1] Figure 1 shows a coastal vessel 1 of this embodiment, with Figure 1A being a side view and Figure 1B being a bottom view. The coastal vessel 1 is a two-engine, two-screw, two-rudder vessel with two parallel propellers 6, each equipped with a rudder. Vehicles can be carried on the upper deck 2, and a ramp door 3 is installed at the bow 1a.

[0014] An arc-shaped water flow plate 9 is installed where a line extending perpendicularly downward from the bow 1a intersects with a line extending horizontally from the bottom 1c (forward bottom F, described below). Installing the water flow plate 9 increases the length of the ship, allowing it to push through waves from the left and right. The bow 1a is also equipped with a thruster 4. The bottom 1c has a forward bottom F that extends horizontally in a straight line from the bow 1a to the middle of the hull toward the stern 1b, and a raised bottom T that gradually becomes shallower as it extends from the forward bottom F toward the stern. A propeller 6 and a rudder 7 are installed within the area of ​​the raised bottom T. When viewed from the side, the shape of the stern 1b of the coastal vessel 1, known as the transom stern, is not oval, but rather has a sharply cut-off shape at the stern end.

[0015] Furthermore, since the coastal vessel 1 is intended to sail to islands with shallow water depths, it has a hull bottom structure that allows the vessel's draft WL to be shallow. The rising vessel bottom T is provided with two grooves 10 that are hollowed out in the lengthwise direction of the hull. The reason for hollowing out the rising vessel bottom T with the grooves 10 is to limit the buoyancy loss to the grooves 10, thereby making the submerged area of ​​the rising vessel bottom T as large as possible and increasing buoyancy. One propeller 6 and one rudder 7 are arranged in each groove 10, starting from the bow 1a.

[0016] The bottom surface 10a of each groove 10 begins closer to the bow 1a than the propeller 6 and extends from the rising ship bottom T toward the draft WL, straddling the propeller 6 and rudder 7 and terminating at the stern 1b, approaching the rising ship bottom T. Directly above the propeller 6, the bottom surface 10a of the groove 10 is separated from the ship bottom 1c up to the position of the draft WL. The groove 10 is dome-shaped, rising from the rising ship bottom T from its beginning to its end and then descending. The propeller 6 is accommodated directly below the position where the bottom surface 10a rises most in the direction of the draft WL. The presence of the rising ship bottom T on both sides of each groove 10, which is below the draft WL, ensures buoyancy, allowing the draft WL of the coastal ship 1 to be shallower.

[0017] The width of each groove 10 at the propeller 6 is wider than the width at the stern 1b. When the water current created by the rotation of each propeller 6 passes through the groove 10, just as the water current increases as the river narrows, narrowing the width of the groove 10 at the stern 1b accelerates the water current and increases thrust. In other words, smooth sailing is possible without increasing engine output, thereby reducing fuel consumption. From the position of the propeller 6 to just before the rudder 7, the width of each groove 10 is the same or slightly widens toward the stern, but from the rudder 7 to the stern 1b, the width gradually narrows. The rudder 7, located at the position where the width of the groove 10 narrows, controls the direction of the water current as it begins to accelerate, improving steering effectiveness.

[0018] 2A is a cross-sectional view at the y0 position, FIG. 2B is a cross-sectional view at the y1 position (the position of the skeg 5), and FIG. 2C is a view in which the arm 5a of the skeg 5 covering the propeller 6 has been partially removed.

[0019] In Figure 2A, the groove 10 starts at position x5, closer to the bow 1a than the propeller, and moves from the bottom 1c toward the draft WL, passing over the propeller 6 and rudder 7, before approaching the bottom 1c at the stern 1b, reaching terminal position x0. Five sampled locations from start position x5 to terminal position x0 are shown as positions x1 to x4. Terminal position x0 corresponds to the rear of the coastal vessel 1 as seen from the stern 1b. The bottom surface 10a of the groove 10 begins to rise from start position x5, moving closer to the draft WL than the bottom 1c, and reaches the draft WL at a position (x3) directly above the propeller 6. It then descends away from the draft WL toward terminal position x0.

[0020] In Figure 2B, the propeller 6 is attached to the tip of the rotating shaft 6a of the main engine 6b via the skeg 5. The shaft 7b of the rudder 7 is located at a position (x2) on the stern 1b side of the propeller 6. The upper end of the shaft 7b is supported by a bearing 7d provided at the bottom of the groove, and the lower end of the shaft 7b is supported by a bearing 7c provided on an arm 5a extended from the skeg 5. At position (x2), the draft WL is located within the vertical length range of the bearing 7d, reducing the intrusion of water into the wheelhouse 1d via the bearing 7d.

[0021] The bottom surface 10a of the groove 10 gradually descends from the draft WL from the propeller position x3 to the terminal position x0 of the stern 1b.

[0022] In FIG. 2C, the width of the groove 10 gradually narrows in the range from the position x2 of the rudder 7 to the terminal position x0 of the stern 1b.

[0023] The shape of the groove 10 will be explained for each position x0-x5 in Figure 2 using the cross-sectional views in Figure 3. At the terminal position x0 of the stern 1b, the width of the groove 10 is width h0. The bottom surface 10a of the groove 10 is located a distance d0 deeper than the draft WL. The distance d0 approximately coincides with the depth of the ship's bottom 1c from the draft WL. At position x1, the width of the groove 10 is width h1, which is wider than width h0. The bottom surface 10a of the groove 10 is located below the draft WL by a distance d1, which is shallower than the distance d0. The depth of the ship's bottom 1c from the draft WL is the same as at the terminal position x0.

[0024] At position x2, the width of groove 10 is width h2, which is wider than width h1. The bottom surface 10a of groove 10 is below the draft WL by a distance d2, which is shorter than distance d1. The depth of the ship bottom 1c from the draft WL is deeper than at position x1.

[0025] At position x3, the width of groove 10 is width h3, which is narrower than width h2. The distance d3 from the draft WL to bottom surface 10a of groove 10 is shorter than distance d2, and bottom surface 10a is located approximately at the draft WL (slightly below the draft WL). The depth of the ship's bottom is deeper than position x2.

[0026] At position x4, the width of groove 10 is width h4, which is narrower than width h3. The bottom surface 10a of groove 10 is a distance d4 below the draft WL, which is a distance d3. The depth of the ship bottom 1c is deeper than at position x3.

[0027] At the starting position x5, the width of the groove 10 is h5, which is narrower than the width h4. The bottom surface 10a of the groove 10 is located deeper than the distance d4, at a distance d5 below the draft WL. The depth of the ship bottom 1c is even deeper than the position x4.

[0028] In the above embodiment, the width of the groove 10 is set to width h3, which is narrower than width h2, at position x3 directly above the propeller 6, and is gradually narrower from width h2 to width h0, ultimately reducing the width by approximately 20%. On the other hand, the groove 10 may be set to have the maximum width at position x3 directly above the propeller 6, and the width h0 may be narrowed to approximately half of that width at the terminal position x0 of the stern 1b.

[0029] Figure 4 shows the operation of coastal vessel 1. Figure 4A shows the bottom view, and Figure 4B shows the water flow on the bottom 1c of the vessel from the side of skeg 5. When the water flow created by the rotation of propeller 6 passes through the narrowing groove toward the stern, thrust is increased. The rudder 7 is located midway along groove 10, which narrows from the propeller 6 to the stern 1b. Positioning the rudder 7 midway improves steering effectiveness. This prevents a decrease in the effectiveness of the rudder 7, even when operating around shallow islands. Furthermore, because the bottom 10a of groove 10 is deeper than the draft WL from position x3 directly above propeller 6 to terminal position x0 of the stern 1b, the stern 1b can be raised, reducing resistance.

[0030] According to this embodiment, at position x3 of the propeller 6, the bottom surface 10a of the groove 10 is located approximately at the waterline WL (slightly below the waterline WL), allowing the diameter of the propeller 6 to be large. Furthermore, the buoyancy of the ship's bottom 1c other than the area scooped out by the groove 10 is ensured by the transom stern hull, making it possible to mount a main engine 6b with a large output. Furthermore, because both sides of the groove 10 are surrounded by the ship's bottom 1c that is deeper than the waterline WL, there is no need to attach fins or the like to prevent air from entering from outside.

[0031] [Example 2] In the previous embodiment, the width of the groove 10 gradually narrows from the position x2 of the shaft 7b of the rudder 7 to the start position x5 of the groove 10, which is forward of the position x2. This is intended to reduce the possibility that a swirling flow caused by the rotation of the propeller 6 will also be generated in front of the propeller 6 and hit the skeg 5, causing vibration. However, this narrows the width of the water flow entering the propeller 6. In the second embodiment, the width of the groove 10 gradually widens from the position x2 of the shaft 7b of the rudder 7 to the start position x5 of the groove 10, which is forward of the position x2.

[0032] FIG. 5 shows the bottom 1c' of a coastal vessel 1' according to a second embodiment. In this embodiment, the width of the groove 10 at the starting position x5 of the groove 10 is width hx. Width hx is larger than width h2 at position x2 of the shaft 7b of the rudder 7 and width h3 at position x3 directly above the propeller 6. This embodiment has the advantage of being able to increase the water flow taken in by the propeller 6. Note that in this embodiment, the same reference symbols are used for components corresponding to those in the previous embodiments.

[0033] In the above embodiment, the cross-sectional shape of the groove 10 is illustrated as a polygon, but it may be an arc. In the above embodiment, the terminal position x0 of the groove 10 coincides with the stern 1b, but the terminal position x0 may be set at a position just before the stern 1b. Also, although a two-engine, two-screw, two-rudder ship has been shown as the coastal vessel 1, the invention can also be applied to a one-screw, one-rudder ship. [Explanation of symbols]

[0034] 1 Domestic vessel 1' domestic vessel 1a Bow 1b stern 1c Ship bottom 1c' bottom of the ship 1d Wheelhouse 2 Upper Deck 3 Ramp Door 4 thrusters 5 Skeg 5a Arm 6 propellers 6a Rotation axis 6b Main engine 7 Rudder 7b axis 9 Water flow board 10 grooves 10a Bottom

Claims

1. A transom-stern hull has a bow bottom section that extends horizontally in a straight line from the bow to the middle of the hull, and a raised bottom section that continues from the bow bottom section and gradually becomes shallower as it goes towards the stern, and a propeller and a rudder are installed within the raised bottom section. A groove is provided in the longitudinal direction of the hull, the bottom of the ascending vessel being hollowed out, The propeller and the rudder are arranged directly below the groove in this order from the bow side, The bottom surface of the groove starts on the bow side of the propeller, approaches the waterline from the rising bottom of the ship, straddles the propeller and the rudder, and ends by approaching the rising bottom of the ship at the stern side, and the propeller is located directly below the position where the bottom surface rises most in the waterline direction, The width of the groove gradually narrows from the position of the rudder toward the stern of the ship.

2. 2. The coastal vessel according to claim 1, wherein the width of the groove narrows from the position of the propeller toward the bow.

3. 2. The coastal vessel of claim 1, wherein the rudder bearing mounted in said groove has a draft within its vertical length range.

4. 2. The coastal vessel of claim 1, wherein a curved water flow plate is installed at the intersection of a line extending downward at a right angle from the bow and a line extending horizontally from the bottom of the bow.

Images