Rear fin device for catamarans

Abstract

To provide a rear end fin device for a catamaran capable of reducing main engine horsepower necessary for propulsion of the catamaran by alleviating various eddy currents and reducing resistance.SOLUTION: The catamaran is respectively provided with a rear end fin projecting backward from a bottom surface of a transom of right and left single barrel vessels and a rectifying fin projecting downward from a bottom surface of the rear end fin. Further, in the transom of the single barrel vessels, a plurality of rear end fins projecting downward from a bottom surface position and a plurality of rectifying fins projecting downward from bottom surfaces of respective rear end fins are respectively provided in between the twin hull.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an aft fin device for an energy saving device of a catamaran. [Background technology]

[0002] Catamarans, which are constructed by arranging two slender monohulls, each narrow relative to its length, side by side, have been put into practical use in various forms, including different monohull shapes and different widths between the catamarans. However, this application will describe the hull shapes of catamarans and monohulls, focusing on the hull shapes described below, as follows, with reference to Figures 1 to 3. Figure 1 is a plan view from above at the load waterline (LWL), Figure 2 shows a cross section taken along the arrows II-II of Figure 1, and Figure 3 shows an enlarged cross section taken along the arrows III-III of Figure 1. The left-hand monohull 1 and the right-hand monohull 2 ​​are connected and secured symmetrically about the centerline CL3 by a deck 3 extending from the bow to the stern above the load waterline (LWL). Furthermore, as shown in Figure 1, the left-hand monohull 1 is asymmetrically configured from the bow end FE1 to the stern end AE1 about the centerline CL1. That is, on the port side, in the plane of the load waterline (LWL), the width gradually increases in a curved shape from the bow end FE1 toward the rear relative to the centerline CL1, reaching a maximum width B1 near the central part SS5, and from there toward the rear the width gradually narrows in a curved shape, and the stern end AE1 has a longitudinal shape 4 similar to a normal hull shape connected to the transom 10. On the other hand, on the starboard side in the load waterline (LWL) plane, the maximum width B2 on the starboard side relative to the centerline CL1 is configured to be narrower to about half the maximum width B1 on the port side, and the width gradually widens in a curved manner from the bow end FE1 toward the rear, reaching maximum width B2 near the midpoint between the bow perpendicular FP and SS5, and then gradually narrows in a curved manner toward the rear up to near SS5, and then gradually widens in a curved manner toward the rear, reaching a width of about maximum width B2 near the midpoint between SS5 and the aft perpendicular AP, and then gradually narrows in a curved manner toward the rear, and the ship is connected to the transom 10 at the aft end AE1. In this way, from the bow end FE1 to the aft end AE1, the starboard side width has a longitudinal shape 5 that has repeated curved projections and depressions relative to the centerline CL1, and the port and starboard sides are configured differently relative to the centerline CL1, resulting in an asymmetrical configuration. Similarly, on the LWL plane of the right-side monohull 2, the port and starboard sides have shapes 6 and 7 interchanged with those of the left-side monohull 1, and are configured asymmetrically with respect to the centerline CL2, with the same shape in the longitudinal direction.FIG. 3 also shows the cross-sectional shape of the centerline CL1 of the rear half of the hull of the left-hand monohull 1. A hull bottom 8 is provided in a generally straight line, rising rearward from a position aft of SS5 toward the stern end AE1 from the baseline BL, and is fixed to a transom 10. The right-hand monohull 2, although not shown, also has a hull bottom 9 in a similar shape to the above, and is fixed to a transom 11. In the figure, CL1 represents the centerline of the left-hand monohull 1, FE1 represents the bow end of the monohull 1, and AE1 represents the stern end of the monohull 1. Similarly, CL2 represents the centerline of the right-hand monohull 2, FE2 represents the bow end of the monohull 2, and AE2 represents the stern end of the monohull 2. Furthermore, CL3 represents the centerline of the catamaran, FP represents the bow perpendicular, AP represents the stern perpendicular, and SS5 represents the midpoint between the bow perpendicular FP and the stern perpendicular AP. Additionally, the port side of the left monohull 1 and the starboard side of the right monohull 2 ​​are indicated by arrows as "outside," and the opposite side is indicated by arrows as "catamaran." Note that, for ease of explanation, in this specification, the port side of the left monohull 1 and the starboard side of the right monohull 2 ​​will be referred to as "outside," and the opposite side will be referred to as "catamaran," in line with the above. [Patent documents] Patent No. 4365644

[0003] When the above catamaran is traveling at a high speed where the Froude number Fn of the speed function is 0.32 or more, vortices are generated behind the aft ends of the left and right monohulls. Furthermore, vortices are generated between the left and right monohulls, and these vortices join in the center area aft of the catamarans to form a highly vortical vortex. As a result, the generation of these vortices increases resistance, and the main engine horsepower required to propel the catamaran increases. The Froude number Fn, a ship's speed function that indicates ship speed, is expressed by the following formula: Fn=Vs / (g·L)0.5, where Vs is the ship speed, g is the acceleration of gravity, and L is the ship length. DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0004] As mentioned above, when a catamaran is traveling at a high speed where the Froude number Fn of the speed function is 0.32 or more, vortices are generated behind the aft ends of the left and right monohulls. Furthermore, vortices are generated between the left and right monohulls, and these vortices join in the central area behind the catamarans to form a highly vortical vortex. As a result, there is a problem in that the generation of these vortices increases resistance, and the main engine horsepower required to propel the catamaran increases. Means to be solved by the invention

[0005] The present application has been proposed in consideration of the problems of the above-mentioned conventional ships, and in a catamaran consisting of two monohulls, a structure is proposed in which the outer hull is formed from the center line of the left and right monohulls along the outer hull shape on the outer side and between the two monohulls. 1st The rear end fins are provided so as to protrude rearward from the bottom surface of the transom, and the 1st Protruding downward from the bottom of the rear fin 1st A plurality of flow straightening fins are provided on the monohull, and the flow straightening fins project rearward from the intersection of the transom and the bottom of the vessel on the centerline of the monohull. Second Aft end fins are provided between the twin hulls, and the plurality of Second Protruding downward from the bottom of the rear fin Second The invention is characterized by the provision of flow straightening fins.

[0006] When a catamaran equipped with the above-described multiple aft fins and straightening fins is sailing at high speeds where the ship speed function Fn is 0.32 or greater, the aft fins and straightening fins protruding rearward from the transoms of the left and right monohulls act to mitigate vortices generated behind the aft ends of the left and right monohulls. Furthermore, the aft fins located between the catamarans mitigate vortices generated between the catamarans, and the straightening fins protruding downward from the bottom surfaces of the aft fins mitigate the merging of vortices in the central area aft between the catamarans, thereby mitigating high-vorticity vortices. As a result, the mitigation of the various vortices reduces resistance and the main engine horsepower required to propel the catamaran. BEST MODE FOR CARRYING OUT THE INVENTION

[0007] An embodiment of the present invention will be described with reference to Figs. 4 to 10. First, referring to Figs. 4, 5 and 6, the left monohull 1 is provided with a transom 10. 1st Rear end fins 12a, 12b and 1st The flow straightening fin 13 will be explained. As shown in FIG. 4, from the intersection A1 of the bottom 8 and the transom 10 on the center line CL1, 1st The rear end fin 12a protrudes rearward, and as shown in Figures 5 and 6, the length of the rearward protrusion along the outer plate 4 of the width direction shape on the outside is the same from point a to point b, but gradually becomes shorter from point b, and is joined to the outer plate 4 at point c. 1st The length of the trailing end fin 12b that protrudes rearward from point a along the outer plating 5 of the spanwise shape on the twin hull side gradually decreases, and the trailing end fin 12b is joined to the outer plating 5 at point d. 1st The rear end fins 12a, 12b are installed with an appropriate rearward protruding length and an appropriate rearward downward angle α relative to the load waterline (LWL). 1st The rear end fin 12a has a shape that follows the shape of the outer skin of the transom. 1st The aft end fin 12b has a shape that conforms to the outer plate shape of the twin hull side. 1st The rear end fins 12a and 12b are projected downward from the bottom surface where they are joined to an appropriate depth. 1st The right monohull 2 ​​also has a similar configuration to the above, with straightening fins 13 extending from the intersection A2 of the bottom 9 and the transom 11 along the shapes of the outer shell 6 and the outer shell 7 on the catamaran side. 1st The rear end fin 14a and the first rear end fin 14b are provided on the center line CL2. 1st The rear end fin 14a and the 1st The rear end fin 14b protrudes downward from the bottom surface to which it is joined. 1st Next, a straightening fin 15 is provided between the left and right monohulls 1 and 2. SecondThe rear fin will be explained with reference to Figures 7 to 10. Brackets 16, 17 are installed in the center of the rear surface of the transom 10 of the left monohull 1 and the transom 11 of the right monohull 2 ​​in the shapes shown in Figures 4 and 7, respectively, and a beam 18 is installed on the upper surface of the brackets across the catamarans. As shown in Figures 7 and 8, at the lower ends of flat plates 25 and 26 hanging down from the beam 18, Second A rear end fin 19 is provided. Second The rear end fin 20 is provided at the lower end of the flat plates 29, 30, and the second rear end fin 21 is provided at the lower end of the flat plates 29, 30, respectively. Second The leading edges of the aft end fins 19, 20, 21 are provided to project rearward at an appropriate length in the longitudinal direction in accordance with the longitudinal and depth directions of the points A1 and A2, as shown in Figures 9 and 10, and at an appropriate aft downward angle θ with respect to the load waterline LWL as shown in Figure 9. Second The longitudinal positions, depth positions, and rearward downward angle θ of the rear end fins 19, 20, 21 are appropriately determined depending on the hull shape of the monohull and the spacing between the catamarans, so-called differences in the shape of the catamaran. Second It has approximately the same length as the rear end fin 19 and protrudes downward at an appropriate depth from the bottom surface in the width direction center. Second A straightening fin 22 is provided. Second From the bottom of the rear end fin 20 Second The straightening fin 23 is located on the right side of the monohull 2. Second From the bottom of the rear end fin 21 Second The fins 24 are provided on each side of the fuselage. Second The flow straightening fin 23 is provided on the center line CL3 of the catamaran, and the flow straightening fin 23 is provided on the center line CL3 of the monohull 1, 2. Second The flow straightening fins 22 and SecondThe straightening fins 24 are provided at an appropriate angle and open rearward. As mentioned above, in this embodiment, the second aft fins provided between the twin hulls are divided into three parts, but the second aft fins are not divided across the entire twin hull, and are provided symmetrically from the center line CL3 with a shape that changes depending on the front-rear position as well as the length, depth, and rearward angle. Second It is hung down from the bottom of the rear fin. Second The number of rectifying fins and their spacing may also be appropriately determined, and the depth of their downward projection and rearward opening angle may also be appropriately determined.

[0008] In a catamaran equipped with the various aft-end fins and various straightening fins of the present embodiment as described above, when the Froude number Fn of the ship speed function is 0.32 or more, the following fins are provided on the transoms of the left and right monohulls 1 and 2. 1st The action of the rear end fins 12a, 12b, 14a, 14b and the action of the first straightening fins 13, 15 act synergistically to reduce vortexes generated behind the left and right monohulls 1, 2. The second The action of the trailing end fins 19, 20, 21 reduces the vortex flow generated between the twin hulls, and further Second A plurality of rear end fins 19, 20, and 21 are provided on the bottom surface thereof. Second The action of the flow control fins 22, 23, 24 reduces the merging of vortices behind the catamaran, and this synergistic effect reduces the highly vortical vortices behind the catamaran. These actions reduce all vortices generated behind the catamaran, thereby reducing resistance and reducing the main engine horsepower required for the catamaran to sail.

[0009] As described above, the present application is an effective energy-saving device for ships that has a relatively simple configuration as an aft-end fin device targeted at catamarans, but it can also be applied as an effective energy-saving device for ships that can achieve similar effects, such as on twin-stern ships that have two stern forms in the rear half of the hull. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a plan view of a catamaran at the load waterline level. [Figure 2] FIG. 2 is an enlarged view of a cross section taken along the line II-II in FIG. [Figure 3] FIG. 2 is an enlarged view of a cross section taken along the line III-III in FIG. [Figure 4] FIG. 4 is an enlarged view of a cross section taken along the line IV-IV in FIG. [Figure 5] FIG. 5 is an enlarged view of a cross section taken along the line VV in FIG. 4. [Figure 6] 6 is a view taken along the line VI-VI in FIG. 5. [Figure 7] This is a cross-sectional view of monohulls 1 and 2 and a catamaran, equivalent to the VII-VII cross-section in Figure 4. [Figure 8] FIG. 8 is a cross-sectional view taken along the line VIII-VIII in FIG. 7. [Figure 9] 9 is a cross-sectional view taken along the line IX-IX in FIG. 7. [Figure 10] FIG. 8 is a view taken along the arrows XX in FIG. 7. Symbol Explanation

[0011] 1. Monohull 2. Monohull 3 deck 4. Outer shell of monohull 1 5. Outer shell of the catamaran side of monohull 1 6. Outer shell of monohull 2 7. Outer shell of the catamaran side of monohull 2 8. Ship's Bottom 9. Ship's Bottom 10 Transom 11 Transom CL1 Monohull 1 centerline CL2 Monohull 2 ​​centerline CL3 Catamaran Centerline FE1 Monohull 1 bow end AE1 Monohull 1 stern end FE2 Monohull 2 ​​bow end AE2 Monohull 2 ​​stern end B1 Maximum width between center line CL1 and outer panel 4 B2 Maximum width between center line CL1 and outer panel 5 LWL Load line AP Aft Perpendicular FP Fore Perpendicular SS5 Midpoint between the forward perpendicular FP and the aft perpendicular AP BL baseline 12a 1st Rear fin 12b 1st Rear fin 13 1st Straightening fins 14a 1st Rear fin 14b 1st Rear fin 15 1st Straightening fins 16 Angle iron 17 Angle iron 18 Beam 19 Second Rear fin 20 Second Rear fin twenty one Second Rear fin twenty two Second Straightening fins twenty three Second Straightening fins twenty four Second Straightening fins 25 flat plate 26 flat plate 27 flat plate 28 flat plate 29 flat plate 30 flat plate

Claims

[Claim 1] In a catamaran consisting of two monohulls, a first aft fin is provided that projects rearward from the bottom of the transom from the center line of the left and right monohulls and follows the shape of the outer plating on the side between the catamarans, and a first straightening fin is provided that projects downward from the bottom of the first aft fin on the center line, and a plurality of second aft fins are provided between the catamarans that project rearward from the intersection of the transom and the bottom of the hull on the center line of the monohulls, and a second straightening fin is provided that projects downward from the bottom of the plurality of second aft fins.

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