JP2017012190A - High-lift otter board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an otter board capable of improving greatly fishnet-expanding force of a trawl net.SOLUTION: An otter board has a curvature plate 2. The curvature plate 2 is formed in a shape curved in a curvature direction corresponding to an expansion direction of a net opening in a towage state, from a front side end on the front side in a towage direction in the towage state toward a rear side end on the rear side in the towage direction in the towage state. The curvature plate 2 has a top plate 5 and a bottom plate 7 formed thereon.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a high lift otter board, and more particularly to a high lift otter board suitable for expanding a trawl net.

  In the trawl fishing method using the trawl net, which is known as a kind of the trawl fishing method, it is important to appropriately expand the trawl net from the viewpoint of increasing the catch rate and maintaining the quality of the fish being caught, For this reason, conventionally, in the trawl fishing method, an otter board has been adopted as means for expanding the trawl net.

  In general, the otter board is arranged between the trawler and the trawl, and is connected to the trawler via a warp drawn from the trawler, and is connected to the trawl via the otter pennant. As it is towed by a trawler in a connected state, the net mouth of the trawl net is deployed.

  Here, conventionally, in an otter board, a resistance that hinders the trawl net of the trawl net due to a vortex called a wing tip vortex generated at the end of the otter board during towing and separation of the flow at the front edge of the back of the otter board It has been a problem to increase.

  In order to solve this problem, for example, otter boards as shown in Patent Document 1 and Patent Document 2 have been proposed so far.

  That is, in Patent Document 1, vortex reduction is achieved by providing a water flow plate at the upper and lower ends of the otter board main body.

  Moreover, in patent document 2, the vortex reduction is aimed at by providing the rectifying fin which became wide gradually toward the back of the advancing direction in an otter board main body at the front edge of the back surface in a vertical otter board main body.

Japanese Utility Model Publication No. 50-071489 Japanese Utility Model Publication No. 61-193766

  However, in the otter board shown in Patent Document 1 and Patent Document 2, an increase in the force for expanding the trawl network cannot be obtained.

  Therefore, the present invention has been made in view of such points, and can greatly improve the network expansion power of the trawl net. In addition, even if the area of the otter board is reduced, It is an object of the present invention to provide an otter board capable of obtaining a similar or higher network expansion power.

  In order to achieve the above-described object, an otter board according to the present invention is towed together with the trawl net by the trawler in a state of being connected to the trawler and the trawl net so that the net opening of the trawl net is developed. It is a force otter board, and has only one curved plate that moves in the direction of deployment of the net mouth with towing by the trawler, and the curved plate is a front side that is the front side in the towing direction in the towing state. Formed in a shape that curves in a curving direction corresponding to the deployment direction of the net mouth from the end toward the rear end that is the rear side of the towing direction in the towing state, the high lift otter board is In the towing state of the curved plate, the upper end that is vertically upward extends in the bending direction and the direction against the upper end. A top plate formed in such a manner and a lower end portion which is a vertically lower side in a towing state of the curved plate, and extends in the bending direction and a direction against the lower end portion with respect to the lower end portion And a bottom plate formed as described above.

  And according to such a structure, a network expansion force can be increased by the increase in the pressure difference of an edge part, leaving the blade tip vortex of an edge part by both a top plate and a bottom plate.

  In the otter board according to the present invention, in the first embodiment, the curved plate, the top plate, and the bottom plate are formed symmetrically about the center line in the front-rear direction of the towing direction as the target axis. It is characterized by that.

  By forming the planar shapes of the curved plate, the top plate, and the bottom plate symmetrically back and forth as in the second embodiment, the net expansion force can be further improved as compared with the conventional otter board.

  Further, in the otter board according to the present invention, in the first or second form, the top plate and the bottom plate each have a constant extension width in the bending direction in the entire range from the front side to the rear side of the curved plate. It is characterized by being formed.

  As in the third embodiment, the top plate and the bottom plate are each formed so that the extending width in the bending direction is constant in the entire range from the front side to the rear side of the curved plate. The network expansion power can be further improved.

  In the otter board according to the present invention, in any one of the first to third embodiments, the top plate and the bottom plate are extended in a direction against the bending direction with the front end portion of the bending plate. It is formed so as to be parallel to a straight line connecting the rear end.

  The extending state in the direction against the bending direction is formed so as to be parallel to a straight line connecting the front end and the rear end of the bending plate, or the extending width in the bending direction. However, due to the effects of both the top plate and the bottom plate that are uniformly formed in the entire range from the front side to the rear side of the curved plate, it is possible to further improve the net spreading power over the conventional otter board.

  According to the otter board according to the present invention, the net expansion force of the trawl net can be greatly improved.

The block diagram which shows embodiment of the otter board which concerns on this invention Plan view of FIG. AA sectional view of FIG. Bottom view of FIG. The figure which shows the towing state of the otter board and trawl net | network by a trawler in embodiment of the otter board which concerns on this invention In the embodiment of the otter board according to the present invention, a graph showing the test results of the network expansion characteristics The perspective view which shows an example of the bi-leaf type otter board as a comparative example as embodiment of the otter board which concerns on this invention In the embodiment of the otter board according to the present invention, a graph showing the test result of the performance evaluation test

  Embodiments of an otter board according to the present invention will be described below with reference to FIGS.

  The otter board in the present embodiment is formed so as to expand the net mouth of the trawl net by being towed together with the trawl net by the trawl ship as being connected to the trawl ship and the trawl net.

  That is, FIGS. 1 to 4 show a port side otter board connected to the port side of the trawler as the otter board 1 in this embodiment, and this otter board 1 is accompanied by towing by the trawler. It has a curved plate 2 that can be moved in the direction of deployment of the net opening of the trawl net. The curved plate 2 has a rear end portion (FIG. 1 to FIG. 1) that is a rear side in the towing direction in the towing state from a front end portion (a right end portion in FIGS. 1 to 4) that is the front side in the towing direction in the towing state. As shown in FIG. 4, a planar shape that curves in a bending direction (upward in FIGS. 1 to 3 and downward in FIG. 4) corresponding to the unfolding direction of the net mouth of the trawl net is circular. It is formed in the shape to exhibit. Here, “corresponding to the deployment direction of the net opening” means that the curved plate 2 is bent in the bending direction, so that the curved plate 2 is expanded in the net opening direction by water pressure acting on the bending plate 2 during towing. This means that there is a correspondence relationship between the direction of bending and the direction of net opening.

  The curved plate 2 may be formed of a metal such as aluminum, for example.

  Further, as shown in FIG. 3, the surface 2 a (the upper surface in FIG. 3) on the bending direction side of the bending plate 2 covers a region in a predetermined range on the front side (the right side in FIG. 3) on the surface 2 a on the bending direction side. A bulging structure 4 having a bulging surface 3 that bulges toward the bending direction side from this region is formed.

  More specifically, the bulging structure 4 is curved from the front end portion (right end portion in FIG. 3) on the front surface 2a of the curved plate 2 as a region of the predetermined range. It forms in the area | region over the intermediate position with the edge part (left edge part in FIG. 3) of the rear side in the surface 2a of a direction side.

  Further, the bulging surface 3 has a region in a certain range on the front side (right side in FIG. 3) from the front end (right end portion in FIG. 3) side of the bulging surface 3 to the rear end portion (see FIG. 3). 3 is formed in an arcuate curved surface 3a that curves in the bulging direction (upper right direction in FIG. 3) toward the left end portion in FIG. Furthermore, the bulging surface 3 is formed with a portion other than the portion in the predetermined range on the front side, that is, a portion in the fixed range on the rear side (left side in FIG. 3) on the flat surface 3b. Furthermore, the plane 3b is formed so that its surface normal is parallel to the bending direction of the bending plate 2. Note that where the boundary position between the curved surface 3a and the flat surface 3b is taken can be variously changed according to the concept. For example, the chord direction of the curved plate 2 with respect to the rear end portion of the curved surface 3a ( The position in the horizontal direction in FIG. 3 may be a position that is 1/4 of the length in the chord direction of the curved plate 2 as measured from the front end of the curved plate 2.

  Furthermore, as shown in FIG. 3, the bulging structure 4 is a curved plate-like plate fixed on the region of the predetermined range of the surface 2 a on the bending direction side of the bending plate 2 via both front and rear ends. It is comprised by the shaped member. This plate-like member may be made of a metal such as aluminum. In this case, when the curved plate 2 is formed of metal, the plate-like member may be stably fixed to the curved plate 2 by welding.

  Further, the dimensions in the height direction (the vertical direction in FIG. 1 and the vertical direction in the drawing in FIG. 2) of the bulging structure 4 and the bulging surface 3 may be the same as the dimensions of the curved plate 2 in the height direction, Alternatively, it may be shorter than the dimension of the curved plate 2 in the height direction.

  And according to such a structure, the eddy which generate | occur | produces in an otter board by the rectification | straightening effect | action of the bulging structure 4 can fully be reduced, and the network expansion force of a trawl network can fully be improved. In addition, the formation region of the bulging structure 4 can be a preferable region for reducing the generation of vortices, and the shape of the bulging surface 3 can be a preferable shape for reducing the generation of vortices. . Furthermore, the bulging structure can be easily formed.

  In addition to the above-described configuration, the otter board 1 in the present embodiment further includes an upper end portion (upper end portion in FIG. 1) that is vertically upward in the towing state of the curved plate 2, as shown in FIGS. 1 and 2. In FIG. 2, a plate-like top plate 5 that is orthogonal to the curved plate 2 is formed on the front side of the drawing. Here, as shown in FIG. 2, the top plate 5 is in the bending direction (upward direction in FIG. 2) and the opposite direction (downward direction in FIG. 2) with respect to the upper end portion of the bending plate 2. The overall planar shape is formed in a substantially bowl shape so as to extend.

  Further, as shown in FIG. 2, the portion corresponding to the region of the predetermined range in the top plate 5, that is, the front half of the top plate 5 (the right half in FIG. 2) extends in the bending direction. The width is equal to or greater than the width of the portion of the top plate 5 other than the portion corresponding to the region in the predetermined range, that is, the extending width in the bending direction of the rear half of the top plate 5 (the left half in FIG. 2). It is said that. As shown in FIG. 2, the front half of the top plate 5 has an end on the bending direction side that has a shape along the bulging surface 3 and is closer to the bending direction than the bulging surface 3. It has been extended. Further, as shown in FIG. 2, the rear half of the top plate 5 has a shape in which the end in the bending direction is along the rear half of the surface 2 a of the curved plate 2. . Further, the end portion (the lower end portion in FIG. 2) of the top plate 5 that opposes the bending direction forms a string of the bending plate 2 in FIG. The top plate 5 may be made of the same material as the curved plate 2.

  According to such a structure, generation | occurrence | production of a vortex can further be reduced by the rectification | straightening effect | action of the top plate 5, and the network expansion force of a trawl net | network can be improved more.

  In addition to the above configuration, the otter board 1 according to the present embodiment is further provided with a lower end portion (lower end in FIG. 1) that is a vertically lower side in the towing state of the curved plate 2, as shown in FIGS. 1 and 4. 2, a plate-like bottom plate 7 that is orthogonal to the curved plate 2 is formed at the end of the paper surface side in FIG. 2, and this bottom plate 7 is the top plate 5 shown in FIGS. 1 and 2. And the planar shape are the same.

  That is, the bottom plate 7 extends in the bending direction (downward direction in FIG. 4) and the opposite direction (upward direction in FIG. 4) with respect to the lower end of the bending plate 2, The overall planar shape is formed in a substantially bowl shape. Furthermore, as shown in FIG. 4, the extension width in the bending direction of the portion corresponding to the region of the predetermined range in the bottom plate 7, that is, the front half portion (the right half portion in FIG. 4) of the bottom plate 7 is The width of the bottom plate 7 other than the portion corresponding to the region in the predetermined range, that is, the rear half of the bottom plate 7 (the left half in FIG. 4) is greater than or equal to the extending width in the bending direction. . Further, as shown in FIG. 4, the front half of the bottom plate 7 has an end on the bending direction side that has a shape along the bulging surface 3 and extends further to the bending direction side than the bulging surface 3. Has been issued. As shown in FIG. 4, the rear half of the bottom plate 7 has a shape in which the end in the bending direction is along the rear half of the surface 2 a of the curved plate 2. Further, the end portion (upper end portion in FIG. 4) of the bottom plate 7 on the side opposite to the bending direction forms a chord of the curved plate 2 in FIG. Further, the bottom plate 7 may be formed of the same material as the curved plate 2.

  By the combination of the bulging structure 4 and the rectifying action of the top plate 5 and the bottom plate 7 described above, the net expansion force of the trawl net can be greatly improved.

  As another configuration, as shown in FIG. 1 and FIG. 3, the curved plate 2 is a surface 2 b on the direction side that opposes the surface 2 a on the curved direction side, and the upper end and the lower side of the curved plate 2. A middle plate 8 parallel to the top plate 5 and the bottom plate 7 is formed at a position slightly above the intermediate position with the end portion so as to extend in a direction against the bending direction. As shown in FIG. 3, the intermediate plate 8 has a plate-like warp mounting portion 10 that is orthogonal to the intermediate plate 8 and has an inclination that goes in a direction against the bending direction toward the front side. The warp mounting portion 10 is formed with a plurality of (three in FIG. 1) through-holes 11 for mounting the warp so as to be spaced apart from each other at a predetermined interval. Yes. The through hole 11 serves as a saddle point of the otter board 1 during towing. The position of the through hole 11 in the chord direction of the curved plate 2 is the length of the curved plate 2 in the chord direction ( That is, it is preferable that the length of the curved plate 2 is 30% to 40% as measured from the front end of the curved plate 2 with respect to the total length of the curved plate 2.

  Further, as shown in FIG. 2, a plurality of (five in FIG. 2) penetrations for attaching otter pennts are provided on the edge portion on the curved direction side in the rear half of the top plate 5. The holes 12 are formed along the arcs of the curved plate 2 at a predetermined interval. As shown in FIG. 2, a reinforcing plate 13 may be provided on the lower surface of the top plate 5, and the through hole 12 may penetrate the reinforcing plate 13.

  Furthermore, as shown in FIG. 4, a plurality (five in FIG. 4) through-holes for attaching otter pendents also on the edge portion on the curved direction side in the rear half of the bottom plate 7 14 are drilled at predetermined intervals along the arc of the curved plate 2.

  Furthermore, as shown in FIG. 1, on the upper surface of the bottom plate 7, a plate-shaped weight steel 15 for allowing the otter board 1 to sink in the sea is detachably disposed.

  The otter board 1 of this embodiment is connected to the trawler 17 by attaching a warp 18 fed from the port side of the trawler 17 to the through hole 11 as shown in FIG. By attaching the otter pennant 22 connected to the through holes 12 and 14 to be connected to the trawl net 20, it is towed by the trawler 17. As shown in FIG. 5, between the otter pennant 22 and the trawl net 20, a hand rope 21 and a relay member 23 made of a shackle for relaying the otter pennant 22 and the hand rope 21 are interposed. Yes.

  Further, as shown in FIG. 5, during towing, the port side otter board 1 of the present embodiment and the starboard side otter board 1 ′ having a vertically symmetrical shape in FIGS. 2 to 4 are fed out from the starboard side. While being connected to the trawler 17 via the warp 18, it is towed by the trawler 17 as being connected to the trawl network 20 via the otter penent 22 and the hand rope 21.

  Then, by the towing by the trawler 17, the port side otter board 1 is moved in the left direction (the left direction toward the towing direction), which is the development direction of the trawl net opening 25 by the port side otter board 1. Is moved to the left.

  Further, the starboard side otter board 1 'moves the net mouth 25 in the right direction by moving in the right direction which is the developing direction of the net mouth 25 of the trawl net by the starboard side otter board 1'. It has become.

  Next, as an example of the present invention, test results of a performance evaluation test performed on the otter board 1 of the present embodiment will be described.

  In this example, as two types of otter boards of the present invention, a model of the otter board 1 (including the bulging structure 4, the top plate 5 and the bottom plate 7) of the above-described embodiment, and the top plate 5 and a model having only the bottom plate 7 are created to examine the net expansion force (lift force) characteristics, and thereafter, a comparison test with a conventional otter board using the actual otter board 1 of the above-described embodiment (performance) Evaluation test) was performed.

  Here, in the net expansion force characteristic test, first, the otter board model of the present invention was attached to a six-component force meter in a circulating water tank, and the lift applied to the model in flowing water was measured. Fig. 6 shows the relationship between the angle of attack to the flow (the angle formed with the mesh screen direction) and the lift coefficient as a result of this network expansion characteristic test. FIG. 6 shows a test in which a reticulation force characteristic test similar to the two types of otter board models of the present invention was performed on the model of the conventional multi-leaf type otter board 27 shown in FIG. An example of the results is also shown.

The netting power of the otter board is defined as the lift of the following equation.
L = (1/2) CLρSV2 (1)
However, L in Formula (1) is a network expansion force (lift) [N]. Further, CL in the equation (1) is a lift coefficient [dimensionless amount], and this lift coefficient can be regarded as a coefficient unique to the otter board. Furthermore, ρ in the equation (1) is the density of water [kg / m ³ ]. Furthermore, S in the equation (1) is the projected area [m2] of the otter board, and this projected area S can be regarded as a value proportional to the surface area of the curved plate. Further, V in the equation (1) is a flow velocity [m / s], and this flow velocity can be regarded as the same as the towing speed of the otter board by the trawler.

  That is, the net expansion force of the trawl net is proportional to the lift coefficient and also proportional to the area of the curved plate.

  The lift coefficient of the otter board according to the present invention is considerably larger than that of the conventional biplane otter board.

  Further, as shown in FIG. 6, the otter board of the present invention has a sufficient effect even when the bulging structure 7 is not provided (only the top plate 5 and the bottom plate 7). In addition, if the bulging structure 7 is provided, the greatest effect can be obtained.

  Next, in the present embodiment, as a comparative test, the otter board of the present embodiment is compared with the conventional multi-leaf otter board 27 shown in FIG. A performance evaluation test with 1 (all provided with the bulging structure 4, the top plate 5 and the bottom plate 7) was carried out with the actual product. 7 is a port side otter board, and the starboard side otter board has a shape symmetrical to that shown in FIG.

  Here, the otter board 27 shown in FIG. 7 has two curved plates 28, and these curved plates 28 are arranged to face each other at a predetermined interval in the bending direction. The end of the curved plate 28 on the front side in FIG. 7 is a front end that is the front side in the towing direction in the towing state, and the end on the back side of the drawing is towed in the towing state. The rear end is the rear side of the direction. Further, a top plate 29 having an outer shape along the curved surfaces of the two curved plates 28 is fixed to the upper ends of the two curved plates 28 in FIG. Further, a bottom plate 30 having an outer shape along the curved surfaces of the two curved plates 28 is fixed to the lower ends of the two curved plates 28 in FIG. Further, upper and lower middle plates 31 and 32 are fixed between the curved surfaces of the curved plates 28 facing each other. Further, a plate-like warp mounting portion 34 is formed at the front ends of the middle plates 31 and 32, and a through hole 35 for mounting the warp 18 (see FIG. 5) is formed in the warp mounting portion 34. It is installed. Furthermore, a pair of plate-like pendant attachment portions 36 are formed at the rear ends of the middle plates 31 and 32, and the otter pennant 22 (see FIG. 5) is attached to these pennant attachment portions 36. For this purpose, a through hole 37 is formed. Similar to the otter board 1 shown in FIG. 5, the otter board 27 of this comparative example is connected to the trawler 17 by attaching a warp 18 fed from the port side of the trawler 17 to the through-hole 35 and is connected to the trawler 17. The otter penetrant 22 connected to the net 20 is attached to the through-hole 37 so that it is towed by the trawler 17 as being connected to the trawl net 20.

  In the performance evaluation test, the otter board 1 of the present embodiment and the otter board 27 of the comparative example are both made of stainless steel.

Furthermore, in this performance evaluation test, the otter board 1 of the present embodiment is configured such that the dimension in the height direction (vertical direction in FIG. 1) of the curved plate 2 is the dimension in the chord direction (lateral direction in FIG. 1) of the curved plate 2. The aspect ratio of the curved plate 2 which is the value obtained by dividing the value is 1. Specifically, the dimension in the height direction and the dimension in the chord direction of the curved plate 2 were both 1000 [mm]. The projected area of the bending plate 2 of the otter board 1 in the bending direction is 1.0 [m ² ]. Further, the position in the chord direction of the curved plate 2 with respect to the rear end portion of the curved surface 3 a on the bulging surface 3 is measured from the front end portion of the curved plate 2 with respect to the length of the curved plate 2 in the chord direction. The position is set to a length of 1/4, and the position of the through hole 11 in the chord direction of the curved plate 2 is measured from the front end of the curved plate 2 to be 325 [mm]. Set to position.

In this performance evaluation test, the otter board 27 of the comparative example has an aspect ratio of 2 for the two curved plates 28. Specifically, both the curved plates 28 have a height dimension of 1200 [mm] and a chord dimension of 600 [mm]. The total value of the projected areas in the bending direction of the two bending plates 28 of the otter board 27 is 1.44 [m ² ].

  Next, specific contents of this performance evaluation test will be described. In this embodiment, as shown in FIG. 5, the towing speed (knot) and the port side and starboard side otters when towing the otter board 1 (the same applies to the otter board 27 of the comparative example) together with the trawl net 20 are also shown. A performance evaluation test was conducted to examine the relationship between the left and right distances between the boards 1 and 1 '(hereinafter referred to as the otter board distance) [m].

  In the performance evaluation test, the length of the warp 18 was 100 [m], and the diameter of the warp 18 was 12 [mm].

  Next, the test result of the performance evaluation test is shown in FIG.

  As shown in FIG. 8, it was found that the otter board 1 of the present embodiment has a larger otter board interval value corresponding to the towing speed than the otter board 27 of the comparative example. Here, as the value of the otter board interval is larger, the net opening 25 of the trawl net 20 is more easily developed to the left and right. Therefore, the otter board 1 of this embodiment is wider than the otter board 27 of the comparative example. It can be said that the net power is large and suitable for expanding the trawl net 20. In general, a biplane otter board is more suitable for expanding the network than a otter board having a single curved plate, but the otter board 1 of this embodiment is more suitable than the biplane otter board 27. The better results were obtained in the performance evaluation test because the otter board 1 in the present embodiment sufficiently suppressed the generation of the separation vortex by the bulging surface 3, and the top plate 5 and the bottom plate 7. It is estimated that this is a comprehensive effect.

  Here, the otter board 1 in this embodiment has a lift coefficient of about 1.6 times that of a conventional otter board in which the bulging structure 4, the top plate 5 and the bottom plate 7 are excluded from the otter board 1. I know that. This indicates that the otter board 1 of the present embodiment requires a smaller area of the curved plate of the otter board required to obtain a predetermined network expansion force than the conventional otter board. .

  Therefore, according to the present embodiment, in addition to improving the net spreading power, it is possible to further reduce the size of the otter board. As a result, the fishing gear can be easily operated on the deck of the trawler, so that the operation efficiency can be improved and the operation efficiency can be reduced. It is possible to save labor and contribute to the improvement of fishery management. Further, the otter board can be manufactured at low cost by reducing the raw material of the otter board, and the cost can be reduced.

  In addition, this invention is not limited to such a structure, A various change is possible as needed.

  For example, although the otter board 1 in the above-described embodiment includes all of the bulging structure 4, the top plate 5, and the bottom plate 7, the present invention is not limited to such a configuration, and the bulging structure 4, at least one of the top plate 5 and the bottom plate 7 may be provided. For example, as shown in FIG. 6, only the top plate 5 and the bottom plate 7 may be provided, or the bulging structure 4 may be provided. You may make it provide only.

DESCRIPTION OF SYMBOLS 1 Otter board 2 Curved plate 2a Curve direction side surface 3 Swelling surface 4 Swelling structure 5 Top plate 7 Bottom plate

Claims (4)

A high lift otter board that unfolds the net mouth of the trawl net by being towed with the trawl net by the trawl ship as being connected to the trawl ship and the trawl net,
Having only one curved plate that moves in the direction of deployment of the net mouth with towing by the trawler,
The curved plate extends in a curved direction corresponding to the unfolding direction of the net mouth from the front end that is the front side in the towing direction in the towing state toward the rear end that is the rear side in the towing direction in the towing state. Formed into a curved shape,
The high lift otter board is
A top plate formed so as to extend in the curved direction and a direction against the upper end portion on the upper end portion that is vertically upward in the towing state in the curved plate;
A bottom plate formed at a lower end which is a vertically lower side in the towing state of the curved plate so as to extend in the bending direction and a direction against the lower end with respect to the lower end; High lift otter board characterized by that. 2. The high lift otter board according to claim 1, wherein each of the curved plate, the top plate, and the bottom plate has a plane shape that is symmetrical with respect to a center line in the front-rear direction of the towing direction. The top plate and the bottom plate are each formed so that the extending width in the bending direction is constant in the entire range from the front side to the rear side of the curved plate. High lift otter board. The top plate and the bottom plate are formed such that an extending state in a direction against the bending direction is parallel to a straight line connecting a front end and a rear end of the curved plate. The high lift otter board according to any one of claims 1 to 3.

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