JP2007022408A - Turbulence inhibiting shape fin of surfboard - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To inhibit the water flowing turbulence of a fin by setting a turbulence inhibiting attachment to the fin of a surfboard. <P>SOLUTION: A fin attachment 11 is integrally fastened to the fin 10. Right and left surface profile part 12 at the middle part of the plate-like fin extends from the fin attachment 11 over the lower and rear flat surface. A right and left surface profile part 13 near a front ridge extends backward symmetrically to the right and to the left from the front ridge 15a of the right and left surface profile part 12 at the middle part of the fin to the rear part in a curved surface, and is smoothly and integrally jointed to the right and left surface profile part 12 at the middle part of the fin. A right and left surface profile part 14 at a rear ridge extends forward symmetrically to the right and to the left from the rear ridge 14a of the right and left surface profile part 12 at the middle part of the fin in the parabolic surface or curved surface, and smoothly and integrally jointed to the right and left surface shape part 11 at the middle part of the fin. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

      The present invention relates generally to surfboards, and more particularly to fins attached thereto. In particular, the present invention relates to a fin having a shape that suppresses turbulent water flow that occurs during surfing.

    A surfboard is a play equipment or sport equipment for riding waves. And how to use it is to find the wave undulation from the sea off the sea, lying on the surfboard in the stomach, getting up when accelerated by the arm and pushed by the wave undulation, along the whole body or the direction of the wave breaking It ’s something to slip. Occasionally, it can be enjoyed by moving up and down and left and right using the slope created by the waves. Thus, the shape of the surfboard varies, and changes depending on the size and shape of the wave, or how to make a vertical movement (large movement, small movement, etc.) relative to the slope of the sea urchin. And all surfboards have fins for stability, acceleration and control. The fin is shaped like a fish fin, and is attached to the rear of the portion of the plate-shaped surfboard that contacts the sea surface and extends downward.

    The number of fins is also varied, with one in the middle and three left and right fins in addition to the mainstream, but only two on the left and right, and additional fins on the left and right of the three fins There are five things added. The purpose of attaching the fins is stability during surfing and control during undulation of the waves. And you can enjoy changing the size and shape of the fins according to the shape of the surfboard and how you enjoy the waves.

    In the past, fins were robbed on surfboards (with a shape that lays on a putty, recreating the roots of fish fins), but recently detachable ones have become mainstream. The reason for this is that in order to surf according to each person, the fins with different shapes are replaced for convenience of carrying when traveling and so on.

    However, with the current system, a corner is created on the bonding surface between the fin and the board by design, and a swirl occurs in that part, smooth water flow, a force that prevents movement, and during acceleration and turn control Causes stall, blurring, and skidding. In addition, if roving is applied to the removable fin, there is a problem in terms of cost. Currently there are no roving detachable fins.

    Therefore, the point that we focused on this time is to eliminate the negative factors caused by the surfboard and fins being mounted in an unnatural form and to maximize the characteristics of the original surfboard and fins. What I came up with was to attach it to the current detachable fin using the attachment method. By attaching this attachment, we are paying attention to whether it is possible to eliminate the elements that hinder water and maximize the speed and make it easier to control.

    Most surfers currently want to use a roving fin-on system (installed), but they are often used in situations where the surfboard is carried or replaced with a fin that matches the wave. So use a removable system (removable).

    As described above, a fin for controlling the direction of travel of the surfboard for enjoying surfing on the coast is mounted on the bottom of the rear part of the surfboard. The shape, size, and number of fins are selected in consideration of the surfer's preference and the viewpoint of sports science.

By the way, the fin of the surfboard is produced using a minimum area of a single flat plate from the viewpoint of simplicity of the manufacturing process and manufacturing cost. Therefore, the fins have conventionally been flat plate-shaped. Therefore, the turbulent flow of the seawater resulting from the flat plate shape has occurred. Therefore, a filing application for a fin attachment having a streamlined bulge shape for preventing turbulent flow was filed on September 14, 2004 as described in Patent Document 1 below.
Japanese Patent Application No. 2004-266980 Surf Style 2001 Co., Ltd. NALU Co., Ltd.

    In other words, when an object such as a surfboard travels after draining water, not only the direct resistance of water but also turbulence such as vortex flow occurs in various places, and the vortex force works in the form of pulling back the object against its traveling direction, Swirl also occurs in the horizontal direction. Accordingly, the conventional fin F of the conventional surfboard S as shown in the right side view (the left side is the traveling direction) shown in FIG. 1A and the front view shown in B (the dashed line in the figure is a virtual line indicating the center). A turbulent flow (a line indicated by an arrow in FIG. 1) was generated which hinders smooth operation and gives instability. In order to prevent this, it is necessary to produce fins having a shape that does not generate turbulence. However, the above-mentioned invention was invented because it was difficult to process the fins in that way from the beginning because it was difficult to simplify the production and to reduce the cost. That is, a conventional fin is used as it is, and an attachment having a shape that suppresses the turbulent flow is attached to a location where a turbulent flow such as a spiral of the fin is generated. However, subsequent studies have shown that the fin itself can be reasonably machined without the use of such attachments.

    In order to solve the above problems, the surfboard-suppressing shape fin of the surfboard according to the present invention has a right side view (the left side is a traveling direction) shown in FIG. 2A and a front view (one-dot chain line in the drawing). Is a shape along the natural flow of the water flow (the line indicated by the arrow in FIG. 2) so that the fin F itself suppresses the turbulent flow of the water flow, as shown in FIG. It is.

Below, the concrete structure of the turbulent flow suppression shape fin of the surfboard concerning this invention is described in detail. First, the configuration of the invention described in claim 1 of the present invention will be described. The present invention is a single fin of a surfboard and consists of the following. that is:
First, there is a fin mounting part to the surfboard. Next, there are left and right surface shape portions in the center of the flat fin. The central left and right surface shape portions of the flat fin extend from the fin mounting portion to the lower and rear planes. And there exists a front ridgeline vicinity left-right surface shape part. The left and right surface shape portions in the vicinity of the front ridge line extend from the front ridge line at the front of the center left and right surface shape portion of the fin to the left and right symmetrically in the shape of a parabola or a curved surface. It is smoothly connected to the left and right surface shape portions of the central portion.

    Furthermore, there are left and right surface shape portions near the rear ridge line. The left and right surface shape portions in the vicinity of the rear ridge line extend from the rear ridge line at the rear of the center left and right surface shape portion of the fin to the left and right symmetrically in the shape of a parabola or a curved surface. It is smoothly connected to the left and right surface shape portions of the central portion. Finally, there are skirt-type left and right surface shape parts. This skirt-type left and right surface shape part is provided in the upper part of the left and right surface shape part near the front ridge line in front of the center left and right surface shape part of the fin, and gently at the upper end of the front ridge line. The skirt ridgeline that is connected to the skirt part extends from the connection point of the skirt part ridgeline toward the tip contact point to the above surfboard in a parabolic or curvilinear shape spreading toward the front, while the skirt part ridgeline extends from the skirt part ridgeline to the surfboard. It spreads in the shape of a parabola or a curved surface in the form of a symmetric parabola toward both side surfaces in contact.

    Next, the structure of the invention described in claim 2 of the turbulent flow suppression shape fin of the surfboard according to the present invention will be described. Thus, the invention of claim 2 is a surface shape portion of a pair of two or more split pair fins of a surfboard composed of right and left symmetrical fins and consists of the following. that is:

In the right fin;
First, there is a right fin mounting part. Next, there is a right surface shape portion at the center of the right fin. The right surface shape portion of the center portion of the right fin has a flat plate shape extending from the right fin mounting portion to the lower and rear planes. And there is a right surface shape portion near the front ridgeline. The right surface shape portion near the front ridge line extends rearward from the right fin front ridge line at the front of the center right surface shape portion of the right fin to the shape of a parabola or curved surface, The fin is gently connected to the right surface shape portion of the center portion of the fin.

Further, there is a right surface shape portion near the rear ridgeline. The right surface shape portion near the rear ridge line extends from the right fin rear ridge line at the rear of the right surface shape portion of the center portion of the right fin to the front of the parabolic surface or the curved surface of the center of the right fin. It is smoothly connected to the right surface shape part. Finally, there is a skirt-type right surface shape part. This skirt-type right surface shape part is provided in the upper part of the right surface shape part near the front ridge line in front of the center right surface shape part of the right fin, and the upper end of the right fin front ridge line. The ridge line of the right fin skirt part that is gently connected extends from the connection point of the right fin skirt part ridge line toward the tip contact point to the surfboard in the form of a parabola or a curve that spreads forward. On the other hand, this spreads from the ridgeline of the right fin skirt part to a parabolic surface or a curved surface toward the surface contacting the surfboard. and,
There is a right fin inner surface part. This right fin inner surface portion is in a flat state with no undulation over the entire inner surface of the right fin. As well as:

In the left fin;
First, there is a left fin mounting part. Next, there is a left surface shape portion at the center of the left fin. The central left surface shape portion of the left fin is a flat plate extending from the left fin mounting portion to the lower and rear planes. And there is a left surface shape portion near the front ridgeline. The left surface shape portion in the vicinity of the front ridge line extends from the left fin front ridge line at the front of the center left surface shape portion of the left fin to a rear surface of a parabola or a curved surface. It is smoothly connected to the left surface shape portion of the central portion of the fin.

Further, there is a left surface shape portion near the rear ridge line. The left surface shape portion in the vicinity of the rear ridge line extends from the left fin rear ridge line at the rear portion of the left surface shape portion of the central portion of the left fin to the front of the parabolic surface or the curved surface of the center of the left fin. It is smoothly connected to the left surface shape part. Finally, there is a skirt-type left surface shape part. This skirt-type left surface shape portion is provided in the upper portion of the left surface shape portion near the front ridge line in front of the central left surface shape portion of the left fin, and the upper end of the left fin front ridge line. The ridge line of the left fin skirt part that is gently connected extends from the connection point of the left fin skirt part ridge line to the front end contact point to the surfboard in a parabolic shape or curved shape that spreads forward. On the other hand, this spreads in the shape of a parabola or a curved surface from the ridgeline of the left fin skirt portion toward the surface contacting the surfboard. ,further:
There is a left fin inner surface portion. This left fin inner surface portion is in a flat state with no undulation over the entire inner surface of the left fin.

    Finally, the configuration of the invention described in claim 3 of the present invention will be described. The present invention is the turbulent flow-suppressing shape fin for the surfboard, which is provided so as to straddle the two-part paired fin according to claim 2 on the left and right of the single fin according to claim 1 described above. Therefore, the description of the invention of claims 1 and 2 is incorporated herein.

    The turbulent flow suppressing shape fin of the surfboard according to the present invention has been made as described above. Therefore, the above problems have been solved and the following great effects have been produced. That is, by providing a turbulent flow suppression attachment to the fin of the surfboard, the turbulent flow of the fin can be suppressed.

    The purpose of suppressing the turbulent flow generated in the fin of the surfboard was made into a fin shaped to suppress the turbulent flow having a shape that does not generate a turbulent flow such as a conventional fin swirl.

    Hereinafter, a turbulent flow suppressing shape fin of a surfboard according to the present invention will be described in detail with reference to the accompanying drawings using a specific embodiment thereof. First, an example in which one single fin 10 of the first embodiment which is the embodiment of claim 1 is used will be described. This is based on the right side view and the front view shown in FIG. However, the technical content of the present invention is a curve representing the surface shape of the fin for controlling the turbulent flow of water generated in the fin of the surfboard. Therefore, the section of each curve portion does not appear as a solid line. For this purpose, FIG. 3 is shown in which each part is divided by virtual lines for explanation. Therefore, description will be made below with reference to FIG. In the right side view shown in A of FIG. 3, the left side is the forward direction in the traveling direction, and the one-dot chain line in the center of the front view shown in B is a virtual line indicating a ridge line. In the case of an acute angle, it becomes a solid line. Therefore, since the left side view with respect to FIG. 3 is symmetric with FIG. 3, FIG. 3 is used and omitted.

This is a single surfboard S fin 10. The fins 10 are symmetrical in shape, and each part has the following shape and is integrally formed (see FIGS. 2 to 6 below). that is:
First, the fin mounting portion 11 is fixedly integrated with the single fin 10 of the present invention. Next, there is a center portion left and right surface shape portion 12 of the flat fin. The flat left and right surface shape portions 12 of the flat fin extend from the fin mounting portion 11 to the lower and rear planes. In FIG. 3, there are apparently left and right surface shape portions 13 in the vicinity of the front ridge line that are apparently divided by a one-dot chain line (see also FIG. 6). The left and right surface shape portion 13 near the front ridge line extends from the front ridge line 13a of the center left and right surface shape portion 12 of the fin to the left and right symmetrically in the shape of a parabola or a curved surface. The left and right surface shape portions 12 of the central portion are smoothly and integrally coupled.

    Further, there is a left and right surface shape portion 14 (see also FIG. 6) in the vicinity of the rear ridge line that is also apparently divided by a one-dot chain line. The left and right surface shape portions 14 in the vicinity of the rear ridge line extend from the rear ridge line 14a of the center left and right surface shape portion 12 of the fin in the left-right symmetry to the front surface of a parabola or a curved surface. It is connected to the central part left and right surface shape part 12 smoothly and integrally.

    Finally, there is also a skirt-type left and right surface shape portion 15 that is apparently divided by a one-dot chain line in FIGS. 3 and 4 (FIG. 4 which is an enlarged view of this portion of FIG. 3 and a cross-sectional view of each portion thereof) See also FIG. 5 which is an end view). This skirt-type left and right surface shape portion 15 is provided in the upper portion of the front and rear ridge line vicinity right and left surface shape portions 13 in front of the center left and right surface shape portion 12 of the fin, and its front ridge line 13a. A skirt portion ridge line 15a that gently and integrally joins the upper end of the skirt portion extends in a parabolic shape or curved shape that spreads forward from the connection point of the skirt portion ridge line 15a toward the tip contact point S1 to the surfboard S. . On the other hand, the skirt surface 15b extends from the skirt portion ridge line 15a toward the both side surfaces S2 in contact with the surfboard S in the shape of a parabolic surface or a curved surface.

    Therefore, in FIG. 4, which is an enlarged view of this part of FIG. 3, in order to clarify the skirt surface 15b, its respective cross sections, AA ′ line, BB ′ line, and CC ′ line, respectively. It was shown in A, B, and C of FIG. In this way, the skirt surface 15b has an integral shape in which the cross-sectional end views are three-dimensionally connected with a gentle curve like the obstacle skirt on the lower front surface of the top car of the super high-speed train. It is what is doing.

    Next, an embodiment of the invention described in claim 2 of the turbulent flow suppression shape fin of the surfboard according to the present invention will be described. Note that. In the invention of claim 2, the left and right definitions are problematic. That is, since the present invention relates to a surfboard, the determination of the left and right is usually based on the direction of travel. However, the description of the embodiments of the present invention is impossible without the drawings for explanation. In the description of the drawing, since the drawing is based on the drafting method, the right and left definitions are “right” on the right hand side and “left” on the left hand side based on the front view. Therefore, if the right and left names are not decided, it will be confusing. Therefore, in the present invention, since the description is based on the drawings of the embodiments, the left and right expressions according to the drawing method are used.

    Thus, the embodiment of the invention of claim 2 is a two-part paired fin comprising a pair of right and left symmetrical fins R10 and L10 as shown in FIGS. The two-divided pair fins are composed of several pairs of fins in some embodiments. Therefore, the surface shape portion of the fin has a shape in which the single fin 10 described in claim 1 is thickened by dividing it into two in the longitudinal direction and in the longitudinal direction. It consists of the following integrated fins: that is:

At the right fin R10;
First, there are two right fin mounting portions R11. Next, there is a right surface shape portion R12 at the center of the right fin (see FIG. 8). The right surface shape portion R12 at the center of the right fin is a flat plate extending from the right fin mounting portion R11 to the lower and rear planes. And there exists front surface ridgeline right surface shape part R13 (refer also FIG. 12). This front ridge line vicinity right surface shape part R13 extends from the right fin front ridge line R13a at the front of the center right surface shape part R12 of the right fin to the rear in a parabolic or curved surface. The right fin is smoothly coupled to the center right surface shape portion R12.

Further, there is a right surface shape portion R14 near the rear ridge line (see also FIG. 12). This rear ridge line vicinity right surface shape part R14 extends from the right fin rear ridge line R14a at the rear of the center right surface shape part R12 of the right fin forward to a parabolic surface or a curved surface. The right fin is smoothly coupled to the center right surface shape portion R12. Finally, there is a skirt type right surface shape portion R15. The skirt-type right surface shape portion R15 is provided in the upper portion of the right surface shape portion R13 near the front ridge line in front of the center right surface shape portion R12 of the right fin, and the front portion of the right fin. A right fin skirt portion ridge line R15a that gently connects to the upper end of the ridge line R13a is a parabola or curved shape that spreads forward from the connection point of the right fin skirt portion ridge line R15a toward the tip contact point S1 to the surfboard S. It is something that is growing. On the other hand, this extends from the right fin skirt ridge line R15a toward the surface S2 contacting the surfboard S in a parabolic or curved surface. and,
There is a right fin inner surface portion R16 (see FIGS. 9 and 12). The right fin inner surface portion R16 is in a flat state having no undulation over the entire inner surface of the right fin R10. As well as:

At the left fin L10;
First, there are two left fin mounting portions L11. Next, there is a central left surface shape portion L12 of the left fin (see FIG. 10). The left-surface shape portion L12 at the center of the left fin has a flat plate shape extending from the left fin mounting portion L11 to the lower and rear planes. Then, there is a left surface shape portion L13 near the front ridgeline (see also FIG. 12). This front ridge line vicinity left surface shape portion L13 extends from the left fin front ridge line L13a at the front of the center left surface shape portion L12 of the left fin to a rear surface of a parabola or a curved surface, The left fin is gently coupled to the left surface shape portion L12 at the center.

Further, there is a left surface shape portion L14 near the rear ridge line (see also FIG. 12). This rear ridge line vicinity left surface shape portion L14 extends from the left fin rear ridge line L14a at the rear of the center left surface shape portion L12 of the left fin forward to a parabolic surface or a curved surface. The left fin is smoothly coupled to the left surface shape portion 12 of the central portion. Finally, there is a skirt-type left surface shape portion L15. This skirt type left surface shape portion L15 is provided in the upper portion of the left surface shape portion L13 near the front ridge line in front of the center left surface shape portion L12 of the left fin, and the front portion of the left fin A left fin skirt portion ridge line L15a that gently joins the upper end of the ridge line L13a has a parabolic or curved shape that spreads forward from the joining point of the left fin skirt portion ridge line L15a toward the tip contact point S1 to the surfboard S. It is something that is growing. On the other hand, this extends from the left fin skirt portion ridge line L15a toward the surface S2 contacting the surfboard s in a parabolic or curved surface. ,further:
There is a left fin inner surface portion L16 (see FIG. 11 and FIG. 12). This left fin inner surface portion L16 is in a flat state with no undulation over the entire inner surface of the left fin L10.

    Finally, an embodiment of the invention described in claim 3 of the present invention will be described. The present invention provides a turbulent flow restraining shape for a surfboard in which a right fin D10 and a left fin L10 that form a two-part paired fin according to claim 2 are provided to the left and right of the single fin 10 according to claim 1 above. It is a fin. Accordingly, the description of the embodiments of the first and second aspects of the present invention is incorporated herein.

    By suppressing the turbulence generated in the surfboard fins, a better surfboard competition is developed.

It is explanatory drawing of the turbulent flow which arises in the fin of the conventional surfboard, Comprising: The A shows the right side view, The B shows the front view. It is one Example of the turbulent flow suppression shape fin of the surfboard concerning this invention, Comprising: The A shows the right view, The B shows the front view. It is explanatory drawing which divided the shape part of the surface of the thing of FIG. 2 apparently, Comprising: The A shows the right side view, The B shows the front view. FIG. 4 shows a partially enlarged view of A in FIG. 3. FIG. 5 is an end view of a cross section taken along lines A-A ′, B-B ′, and C-C ′ of FIG. 4. FIG. 3 is an end view taken along the line D-D ′ of FIG. 2. It is a front view of the other Example of the turbulent flow suppression shape fin of the surfboard concerning this invention. The right side view of the right fin part of the thing of FIG. 7 is shown, and the shape part of the surface is divided into apparent division for description. FIG. 8 is a left side view of the right fin portion of FIG. 7. The left side view of the left fin part of the thing of FIG. 7 is shown, and the shape part of the surface is divided into apparent division for description. FIG. 8 is a right side view of the left fin portion of FIG. 7. FIG. 8 is an end view taken along line E-E ′ of FIG. 7.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Fin 11 Fin mounting part 12 Fin center part right and left surface shape part 13 Front ridge line vicinity Right and left surface shape part
13a Front ridge line 14 Rear ridge line vicinity Left and right surface shape part
14a Rear edge 15 Skirt type left and right surface shape part
15a Skirt ridgeline
15b Skirt surface S Surfboard S2 Tip contact point S1 Both sides R10 Right fin R11 Right fin mounting portion R12 Right fin central portion right surface shape portion R13 Front ridge line right surface shape portion R13a Right fin front ridge line R14 Rear ridge line right surface Shape part R14a Right fin rear ridge line R15 Skirt type right surface shape part R15a Right fin skirt part ridge line R16 Right fin inner surface part L10 Left fin L11 Left fin mounting part L12 Center part left surface shape part L13 Left fin vicinity left surface Shape part L13a Left fin front ridge line L14 Near rear ridge line Left surface shape part L14a Left fin rear ridge line L15 Skirt type left surface shape part L15a Left fin skirt part ridge line L16 Left fin inner surface part

Claims (3)

  These are the surface shape portions of a single fin of the following surfboard, which are: a fin mounting portion, a flat fin-shaped central left and right surface shape portion extending from the fin mounting portion to the lower and rear planes, and the central portion of the fin Near the front ridge line that extends from the front ridge line at the front of the left and right surface shape parts to the left and right symmetrically in the shape of a parabola or a curved surface and is smoothly connected to the left and right surface shape parts of the central part of the fin Left and right surface shape part, center part of the above fins Left and right surface shape part at the rear of the rear ridge line in the left and right symmetrically extending in the shape of a parabola or a curved surface to the left and right surface shape parts of the center part of the fin Provided in the upper part of the left and right surface shape part near the front ridge line in front of the center left and right surface shape part of the center part left and right surface shape part near the rear ridge line that is gently coupled The skirt ridge line that gently connects to the upper edge of the front ridge line extends in a parabolic or curvilinear shape that spreads forward from the connection point of the skirt ridge line toward the tip contact point to the surfboard. On the other hand, it is characterized by comprising a skirt-type left and right surface shape part spreading from the ridge part of the skirt part to the both sides contacting the above surfboard in the shape of a symmetrical parabola or a curved surface. Surfboard shape fins for surfboards. The surface shape part of a pair of two or more bipartite pairs of surfboards consisting of the following symmetrical right and left fins:
In the right fin;
The right fin mounting part, the right surface shape part of the center part of the flat plate-like right fin extending from the right fin mounting part to the lower and rear planes, the right fin front in front of the right surface shape part of the center part of the right fin The right surface shape part near the front ridge line, which extends in the shape of a parabola or curved surface backward from the part ridge line and is gently joined to the right surface shape part of the center part of the right fin, the center part of the right fin The right surface near the rear ridge line that extends forward from the rear ridge line of the right fin at the rear of the right surface shape portion into a parabolic or curved surface shape and is smoothly connected to the right surface shape portion of the center portion of the right fin. It is provided at the upper part of the right surface shape part near the front ridge line in front of the shape part and the center right surface shape part of the center part of the right fin, and gently connects to the upper end of the right fin front ridge line. Right fin The ridge line of the cart part extends from the connecting point of the ridge line of the right fin skirt part toward the tip contact point to the surfboard, and extends in a parabolic or curved shape toward the front, while the ridge line of the right fin skirt part extends to the surfboard. A skirt-type right surface shape portion extending in a parabolic or curvilinear shape toward the contacting surface, and a right fin inner surface portion in a flat state without undulation over the entire inner surface of the right fin; and :
In the left fin;
Left fin mounting portion, left surface shape portion of the center portion of the flat plate-like left fin extending from the left fin mounting portion to the lower and rear planes, the front of the left fin in front of the left surface shape portion of the central portion of the left fin The left surface shape part near the front ridge line, which extends from the ridge line to the rear side of the parabola or the curved surface, and is gently joined to the left surface shape part of the center part of the left fin, the center part of the left fin The left surface near the rear ridge line that extends forward from the rear ridge line of the left fin at the rear of the left surface shape part into a parabolic surface or a curved surface, and is smoothly connected to the left surface shape part of the center part of the left fin. It is provided at the upper part of the left surface shape portion near the front ridge line in front of the shape portion and the left surface shape portion at the center portion of the left fin, and gently joins the upper end of the left fin front ridge line. Left fin The ridge line of the cart part extends from the connecting point of the ridge line of the left fin skirt part toward the tip contact point to the surfboard, and extends in a parabolic or curved shape toward the front, while the ridge line of the left fin skirt part extends to the surfboard. A skirt-type left surface shape portion extending in the shape of a parabola or a curved surface toward the contact surface, and the left fin inner surface portion in a flat state without undulations extending over the entire inner surface of the left fin,
Surfboard turbulent flow-suppressing shape fin, characterized by comprising.   A turbulent flow of a surfboard comprising the single fin according to claim 1 and the one or more pairs of two-divided fins according to claim 2 provided across the left and right of the single fin. Deterrent shape fin.

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