JPH05185986A - Reaction fin device for marine vessel - Google Patents

Abstract

PURPOSE:To provide a reaction fin for an economic marine vessel of simple structure and high performance at low cost. CONSTITUTION:A reaction fin device for marine vessel is provided with reaction fins 7a, 7f extended relatively longer than a propeller shaft 5a, intermediate reaction fins 7b, 7e shorter than the upper reaction fins 7a, 7f while extended below the upper reaction fins 7a, 7f, and lower reaction fins 7c, 7d. At the time of forward propulsion, the setting angle of the reaction fin of a gunwale side where a propeller wing is lowered, is defined larger than that of an opposite gunwale, while an interval between the front end of the propeller and the rear end of the reaction fin is defined 15%-25% of a diameter DP of the propeller at a position approximately 35% away from the diameter DP of the propeller from the core of the propeller shaft 5a, and the length of a gunwale wing CF of the reaction fin at the same point is defined 10%-20% of DP.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reaction fin device for ships.

[0002]

2. Description of the Related Art In a conventional reaction fin used for improving the propulsive performance of a ship, as shown in the side view of FIG. 15 and the front view of FIG. When turning clockwise, thrust is generated in the forward direction.) Bossing 3a is fixedly provided to stern frame 2a provided at the rear end of hull 1, and propeller shaft 5a rotatably penetrates the interior thereof. , The propeller 5 is fitted to the rear end of the propeller shaft 5
The front end of a is connected to a main engine of an inboard device (not shown). The fin boss 7B is fixed so as to surround the bossing 3a, and reaction fins (hereinafter, referred to as fins) 7a to 7f are radially provided on the fin boss 7B so as to project from the fins 7a to 7f.
Is twisted so that the flow of water is directed in the direction opposite to the forward rotation direction of the propeller 5 (the rotation direction in which the propeller 5 rotates and thrust is generated in the forward direction). On the other hand, rudder horn 2
Is fixedly provided on the upper part of the stern frame 2a,
The rudder 3 is attached to the rudder horn 2 with a pintle (not shown). In a ship provided with such reaction fins, when the propeller 5 rotates forward and the hull 1 is traveling forward, the flow of water in the stern part of the fins 7a ...
By the action of 7f, it is bent in the direction opposite to the rotation direction of the propeller 5 and fed into the propeller 5. As a result, the rotational flow generated behind the propeller 5 is reduced, so that the propeller propelling efficiency is improved. In general, when the propeller rotates, a rotating flow in the same direction as the rotating direction of the propeller is generated behind the propeller, and this rotating flow is not used for propulsion of the hull, so that the propeller propelling efficiency is reduced by the amount of energy generated by the propeller. Therefore, if the rotational flow is reduced, the propeller propulsion efficiency is improved accordingly. The fins 7a to 7f have the same span (length in the radial direction), the broken line circle is an imaginary circle centered on the propeller shaft center, and these fins rotate in the direction opposite to the rotation direction of the screw propeller. Is attached to the fin boss 7B at an angle with respect to the traveling direction.

[0003]

FIG. 17 shows the flow velocity distribution flowing into the reaction fins. In FIG. 17, the solid line 4 shows the constant velocity line in the traveling direction of the ship, and the numerical value represents the ratio to the ship speed. ing. Arrow 6 indicates the flow velocity component in the hull cross section,
The arrow indicates the flow direction, and the length indicates the magnitude of the flow velocity.
The chain line is an imaginary semicircle that is drawn to show the size of the propeller. The fins are provided so as to project radially from the propeller shaft center 8, but the radial direction of the fins changes in the radial direction, so the twist angle of the fins should be changed in the radial direction in order to make the fins effective. Is desirable,
There are disadvantages such as increased manufacturing cost and increased drag due to thicker fins. Therefore, in the conventional fin, the twist angle of the fin is constant in the longitudinal direction of the span according to the average flow direction. Therefore, the vicinity of the tips of the fins does not have an optimum twist angle with respect to the flow direction, and the flow velocity is high, so that a large drag force is generated. Also,
The effect of improving the propulsion efficiency by the reaction fin is the amount obtained by subtracting the propulsive energy generated by the drag of the fin itself from the rotational flow reduction energy reduced by the rotational flow created by the fin. Here, the rotational flow created by the fins and the drag force of the fins themselves are closely related to the mounting angle of the fins, and if the mounting angle of the fins becomes excessive, the rotational flow generation will increase, but the drag force of the fins will increase significantly. Therefore, the effect of improving propulsion efficiency is not so good. On the other hand, if the fin mounting angle is too small, the drag of the fin itself is also reduced, but the generation of the rotational flow is significantly reduced. Therefore, it goes without saying that there is an optimum fin mounting angle, but in the case of a conventional reaction fin, this point is taken into consideration and a propeller is installed as shown in FIG. 16 (B) and FIG. 18 to FIG. During forward rotation, the mounting angle θe of the fins on the port side where the propeller blades descend (the angle between the front surface of the fins and the propeller shaft center) is set larger than the mounting angle θf of the fins on the opposite side. However, subsequent research and studies have revealed that such mounting angles are not necessarily optimal angles of attack. FIG. 20 is a propeller position flow field distribution map of a fertilizer ship, and shows the measurement results when there is no propeller and reaction fins. In the case of such a ship, even fins on the same port side are below the propeller shaft. Fins 7c and 7d (FIG. 16 (B)) are the other fins 7a,
At the same mounting angle as 7b, 7e, and 7f, it becomes too large, and the effect of improving propulsion efficiency is not so great.

The present invention has been proposed in view of the above circumstances, and an object thereof is to provide an economical reaction fin for a ship having a simple structure, low cost, and high performance.

[0005]

To this end, the first aspect of the present invention is as follows.
Is a series of reactions that extend almost radially around the propeller shaft on the upstream side of the screw propeller in order to impart a rotational flow in the direction opposite to the propeller rotation direction to the flow entering the propulsion screw propeller at the stern. In a device provided with fins, a relatively long upper reaction fin overhanging above the propeller shaft, and a middle reaction fin overhanging sequentially below the upper reaction fin and sequentially shorter than the upper reaction fin. ， It is characterized by having a lower reaction fin.

According to a second aspect of the present invention, in order to impart a rotational flow in a direction opposite to the propeller rotation direction to the flow flowing into the propulsion screw propeller at the stern part, the propeller shaft is radially extended on the upstream side of the screw propeller. In the device provided with a plurality of reaction fins that have been taken out, the mounting angle of the reaction fin on the port side where the propeller blade descends during forward rotation is set to be larger than the mounting angle of the reaction fin on the port side.

According to a third aspect of the present invention, in order to impart a rotational flow in a direction opposite to the propeller rotation direction to the flow flowing into the propulsion screw propeller in the stern, the propeller shaft is radially extended around the propeller shaft upstream of the propeller shaft. In a device equipped with a plurality of reaction fins that have been ejected, the mounting angle of the reaction fins that are respectively projected below the level of the propeller shaft at the same port in sequence are below the mounting angle of the reaction fins that are projected above. It is characterized by being made smaller in order.

According to a fourth aspect of the present invention, in order to impart a rotational flow in a direction opposite to the propeller rotation direction to the flow flowing into the propulsion screw propeller at the stern, the propeller shaft is radially extended upstream of the screw propeller. In the device provided with a plurality of reaction fins that are ejected, the distance l _O between the leading edge of the propeller and the trailing edge of the reaction fin is set at a position apart from the axial center of the propeller by about 35% of the propeller diameter D _P. 15% of propeller diameter D _P
It is characterized in that it is selected in the range of up to 25%.

According to a fifth aspect of the present invention, in order to impart a rotational flow in a direction opposite to the propeller rotation direction to the flow flowing into the propulsion screw propeller at the stern part, the propeller shaft is radially extended on the upstream side of the screw propeller. In a device equipped with a plurality of reaction fins that have been ejected, the chord length C _F of the reaction fin is set to 10% of the propeller diameter D _P on an arc that is about 35% of the propeller diameter D _{P from} the axis of the propeller. -20%.

According to a sixth aspect of the present invention, in order to impart a rotational flow in a direction opposite to the propeller rotation direction to the flow flowing into the propulsion screw propeller in the stern, the propeller shaft is radially extended on the upstream side of the screw propeller. In a device equipped with a plurality of reaction fins that have been taken out, when the forward rotation is performed, the mounting angle of the reaction fin on the port side where the propeller blade descends is set to be larger than the mounting angle of the reaction fin on the port side, and at the same port. The mounting angles of the reaction fins projecting downwardly from the level of the propeller shaft are successively reduced to the mounting angles of the reaction fins projecting upward, and the distance l _O of claim 4 and the mounting angle of claim 5 of claim 5. It is characterized by having a chord length C _F.

According to a seventh aspect of the present invention, in order to impart a rotational flow in a direction opposite to the propeller rotation direction to the flow flowing into the propulsion screw propeller at the stern part, the propeller shaft is provided with a substantially radial extension on the upstream side of the screw propeller. In a device equipped with a plurality of reaction fins that have been extended, a relatively long upper reaction fin that is extended above the propeller shaft and a lower reaction fin that is sequentially extended below the upper reaction fin and that is higher than the upper reaction fin. Is characterized in that it comprises a middle reaction fin and a lower reaction fin which are sequentially shorter, and further comprises claim 6.

[0012]

According to the structure of claim 1, in the relatively short fin below the propeller shaft having a relatively high flow velocity, the merit due to the generation of the reverse rotational flow can be made more than the demerit due to the increase in the drag force. Greatly improves propulsion performance in cooperation with relatively long fins.

According to the second and third aspects of the present invention, the plurality of fins having different water depth positions are mounted at angles substantially corresponding to the water flow, so that each fin maximizes its rotational flow generation. In addition, the drag of the fin itself can be minimized.

According to the fourth aspect, at a position away approximately 35% of propeller shaft sincerely propeller diameter D _P, 15 the spacing l _O of the trailing edge of the leading and reaction fin propeller of propeller diameter D _P By selecting in the range of 25% to 25%, the most effective propulsion efficiency can be obtained as compared with the case without the reaction fin (broken line), as shown by the solid line in FIG.

According to the fifth aspect, on about 35% away arc of propeller shaft sincerely propeller diameter D _P, 10 a chord length C _F of the reaction fin propeller diameter D _P
% To 20%, the solid line (B) in FIG.
As shown in (A), the required horsepower reduction amount due to the improvement in propulsion efficiency by the reaction fin exceeds the required horsepower increase amount due to the reaction fin resistance, and is substantially uniform over a considerable range C _F / D _P of the chord length of the reaction fin. A significant improvement in propulsion performance can be seen.

According to the structure of claim 6, during forward rotation,
The reaction fin mounting angle on the port side where the propeller blade descends is set to be larger than the mounting angle of the reaction fin on the opposite side, and the reaction fins that are sequentially extended below the propeller shaft level are mounted on each same port. 5. The corners are successively reduced below the mounting angle of the reaction fins projecting upward, and the distance l _{O of} claim 4 is increased.
Further, by providing the chord length C _F of claim 5, a more effective propulsion efficiency of the ship can be obtained by the synergistic effect of claims 2, 3, 4 and 5.

According to the seventh aspect of the present invention, a relatively long upper reaction fin overhanging to a level above the propeller shaft, a lower reaction fin below the upper reaction fin, and a lower reaction fin than the upper reaction fin. By including the short middle reaction fin and the lower reaction fin, and by providing the sixth aspect, the synergistic effects of the first and sixth aspects can further enhance the propulsion efficiency of the ship.

[0018]

1 is a side view showing a first embodiment of the present invention, and FIG. 2 is a rear view taken along the line II-II of FIG. Three
Is a performance comparison diagram of the present invention and a conventional reaction fin,
FIG. 4 is a front view showing a second embodiment of the present invention, FIGS.
7, FIG. 8, FIG. 9 and FIG. 10 are respectively V-V and VI- of FIG.
FIG. 6 is a sectional view taken along line VI, VII-VII, VIII-VIII, IX-IX, XX.

First, in the first embodiment shown in FIGS. 1 and 2, the fins 7 projecting above the propeller shaft are provided.
a and 7f are relatively long, the fins 7c and 7d projecting at the lower level of the propeller shaft have relatively short spans, and the reaction fins 7b and 7e projecting at the same level as the propeller shaft have the reaction fins 7a. , 7c, an intermediate length. The upper and lower reaction fins and propeller blades are shown in actual length (overall length) instead of projected length from the side (also in FIGS. 11, 13 and 15).

According to such a construction, as shown in FIG. 17, the flow at the position where the fins are installed shows that the flow velocity in the traveling direction of the ship is below the propeller shaft center 8 in a region about the same as the propeller radius. While it is 90% or more of the ship speed, it gradually decreases above the propeller axis. Therefore, below the propeller shaft where the flow velocity is relatively high, the relatively short fins 7c and 7d can make the merit of the reverse rotational flow generation more than the demerit of the drag increase. The propulsion performance can be greatly improved in cooperation with the shaku fins 7b and 7e. By the way, according to such a reaction fin, as shown by the solid line in FIG. 3, the same boat speed can be obtained with a considerably smaller required horsepower than the conventional reaction fin (broken line). In FIG. 2, the fin 7f
Is the longest fin, fins 7a and 7e are equal length fins which are slightly shorter than this, and fins 7b and 7d are fins 7a and 7e.
The fins 7c may be the shortest fins, and the fins 7c may be slightly shorter than e.
It has substantially the same effect as the structure of.

Next, the second embodiment shown in FIG. 4 will be described. The fins 10a to 10f are fins of equal length radially provided on the fin boss 7B, respectively.
f is provided with a twist at a mounting angle θ so as to direct the flow of water in the direction opposite to the forward rotation direction of the propeller 5.

Here, the port fins 10a, 10b, 10c are
As shown in FIGS. 5, 7, and 9, respectively, the mounting angle θc of the lower fin 10c is smaller than the mounting angle θb of the middle fin 10b, and the mounting angle θb of the middle fin 10b is the upper fin 10.
It is made slightly smaller than the mounting angle θa of a, and the mounting angle of each fin has a relationship of θa>θb> θc. On the other hand, the starboard fins 10d, 10e, and 10f are as shown in FIGS. 10, 8 and 6, respectively, and the mounting angle θd of the lower fin 10d is smaller than the mounting angle θe of the middle fin 10e.
The mounting angle θe of e is made slightly smaller than the mounting angle θf of the upper fin 10f, and θf> θe between the mounting angles of the fins.
There is a relation of> θd.

Now, when the hull 1 is traveling forward, the flow of water in the stern is bent by the action of the fins 10a to 10f in the direction opposite to the direction of rotation of the propeller 5 and sent into the propeller 5. Therefore, the rotational flow generated behind the propeller 5 is reduced, and the propeller propulsion efficiency is improved. First, in the case of a fertilizer boat having a propeller position flow field as shown in FIG. 20, the flow direction angle with respect to the line parallel to the propeller axis at the fin mounting position is as follows: the central fins 10b and 10e of the propeller shaft and the upper fin 10a. The lower fins 10c and 10d are smaller than the former, but the mounting angle of the lower fins 10c and 10d is smaller than that of the middle fin 10.
Since the fins 10a to 10f are made smaller than the fins 10a and 10f and the upper fins 10a and 10f, the mounting angles of the fins 10a to 10f are not too large or too small, and the optimum angle of attack (the angle between the front surface of the fin and the flow) is maintained. Therefore, the best effect of propulsion efficiency improvement can be obtained.

That is, according to the second embodiment, the mounting angles of the plurality of fins at different water depth positions are set substantially corresponding to the water flow, so that each fin maximizes the generation of the rotational flow. At the same time, the drag of itself can be minimized.

According to the fin having a structure in which the first embodiment and the second embodiment are combined, the synergistic effect of both embodiments can be obtained.

FIG. 11 is a side view showing a third embodiment of the present invention and a rear view showing its reaction fins, FIG.
2 is a diagram showing the relationship between l _O / D _P and the required horsepower in FIG. 11, FIG. 13 is a side view showing the fourth embodiment of the present invention and a cross-sectional view of the reaction fin taken along the line XIII-XIII, and FIG. 13 is a diagram showing the relationship between C _F / D _P and required horsepower in FIG.

First, in the third embodiment shown in FIGS. 11 to 12, the front edge of the propeller 5 and the fins 7a to 7f are located on an arc 35% of the propeller diameter D _P from the center SC of the propeller shaft 4. The distance l _O from the trailing edge is within 10% to 40% of the propeller diameter D _P. That is, l _O / D _P
= 0.1 to 0.4. When the hull provided with such reaction fins is propelled forward by the propeller 5 being rotated by a main engine (not shown), the water flow is changed in the direction opposite to the rotation direction of the propeller 5 by the action of the fins 7a to 7f. And flow into the propeller 5. As a result, the rotational flow generated behind the propeller 5 is reduced, and the propeller efficiency is improved. With reaction fins, in general, resistance of itself occurs, so the horsepower required for the hull to sail needs to be deducted from the increase in propeller efficiency due to reaction fins. In the case of the reaction fin of this embodiment, the required horsepower is as shown by the solid line in FIG.
The hull can sail at a lower value than without fins (dashed line).

In the third embodiment, l _O / D
_{If P} is selected in the range of 15% to 25% of D _P , the most effective propulsion efficiency can be obtained.

Next, in the fourth embodiment shown in FIG.
It is a cross-sectional view of the fins 7a to 7f in an arc shape which is 35% of the propeller diameter D _P away from the center SCL of the propeller shaft 4, and the cord length C _{F at} this position is the XI thereof.
As shown in the partial cross-sectional view of II-XIII, the propeller diameter D _P
25% or less, for example, 10% to 20%. When the hull 1 provided with such reaction fins is propelled forward by the propeller 5 being rotated by a main engine (not shown), the water flow is reverse to the direction of rotation of the propeller 5 by the action of the fins 7a to 7f. Is changed to and flows into the propeller 5. As a result, the rotational flow generated behind the propeller 5 is reduced, so that the propeller propelling efficiency is improved.
In that case, there is a close correlation between the chord length C _F of the fins 7a to 7f and the propulsion efficiency. As shown in FIG. 14, C _F / D _P is the horizontal axis and the required horsepower due to the fin resistance is The increase amount is the curve B, and the required horsepower reduction amount due to the improvement in the propulsion efficiency of the reaction fin is the curve A. According to this C _F (35% of the propeller diameter or, 0.35D _P code length of the fins on the circular arc) the ratio of the D _P C _F / D _P
Is less than 0.25, especially C _F / D _P is 10% to 20% of D _P
In this case, the required horsepower reduction amount due to the improvement in the reaction fin propulsion efficiency exceeds the required horsepower increase amount due to the fin resistance, and the propulsion performance improvement effect is obtained over the entire range where (BA) is on the horsepower reduction side.

As described in the fourth embodiment, C
_F / D _P is 10% to 20%, and as described in the third embodiment, l _O / D _P is 15% to 25%, and as described in the second embodiment, During forward rotation, make the mounting angle of the reaction fin on the port side from which the propeller blade descends larger than that on the port side, and mount the reaction fins that are sequentially overhanged below the propeller shaft level on each same port. If the corners are successively made smaller than those of the reaction fins protruding upward, the synergistic effect of combining the second, third, and fourth embodiments makes it possible to obtain more efficient propulsion efficiency.

Further, in addition to the above, as described in the first embodiment, if the middle reaction fin is slightly shorter than the upper reaction fin and the lower reaction fin is slightly shorter than the middle reaction fin, these Due to the synergistic effect of combining the embodiments of 1, 2, 3, and 4, more efficient propulsion efficiency can be obtained.

[0032]

In summary, according to the present invention, each claim 1
With the structure of 7, each of the reaction fins for a ship has a simple structure, low cost, and high performance, and is economical.
The present invention is extremely useful in industry.

[Brief description of drawings]

FIG. 1 is a side view showing a first embodiment of the present invention.

FIG. 2 is a rear view taken along the line II-II of FIG.

FIG. 3 is a performance comparison diagram of the present invention and a conventional reaction fin.

FIG. 4 is a front view showing a second embodiment of the present invention.

5 is a sectional view taken along line VV of FIG.

6 is a sectional view taken along line VI-VI of FIG.

7 is a sectional view taken along line VII-VII of FIG.

8 is a sectional view taken along line VIII-VIII of FIG.

9 is a sectional view taken along line IX-IX in FIG.

10 is a cross-sectional view taken along line XX of FIG.

FIG. 11 is a side view showing a third embodiment of the present invention and a rear view showing reaction fins thereof.

FIG. 12 is a diagram showing a relationship between l _O / D _P and required horsepower in FIG. 11.

FIG. 13 is a side view showing a fourth embodiment of the present invention and a sectional view taken along the line XIII-XIII of the reaction fin thereof.

FIG. 14 is a diagram showing the relationship between C _F / D _P and the required horsepower in FIG.

FIG. 15 is a side view showing a right-handed propeller ship equipped with a known reaction fin.

16 is a rear view taken along the arrow XVI-XVI in FIG.

FIG. 17 is a distribution diagram of a flow field flowing into the reaction fin of FIG. 15 (A).

FIG. 18 is a sectional view taken along the line XVIII-XVIII in FIG.

FIG. 19 is a cross-sectional view taken along arrow XVIIII-XVIIII of FIG.

FIG. 20 is a distribution diagram of a propeller position flow field of a model fertilizer ship.

[Explanation of symbols]

1 hull 2 rudder horn (rudder post) 2a stern frame 3 rudder 3a bossing 4 constant velocity line in the direction of travel 5 propeller 5a propeller shaft 6 flow velocity component in the hull cross section 7, 7a to 7f reaction fins 7B fin boss 8 propeller Shaft center 10, 10a to 10f Reaction fin (fin) C _F Chord length of reaction fin D _P Propeller diameter l _O Distance between front edge of propeller and rear edge of reaction fin

Claims (7)

[Claims] 1. In order to give a rotational flow in the direction opposite to the propeller rotation direction to the flow flowing into the propulsion screw propeller at the stern part, the propeller shaft is radially extended around the propeller shaft upstream of the propeller shaft. In a device provided with a plurality of reaction fins, a relatively long upper reaction fin overhanging above the propeller shaft and a relatively long upper reaction fin, which are sequentially overhanging below the upper reaction fin and sequentially shorter than the upper reaction fin. A reaction fin device for ships characterized by having a central reaction fin and a lower reaction fin. 2. In order to impart a rotational flow in a direction opposite to the propeller rotation direction to the flow flowing into the propulsion screw propeller at the stern part, the propeller shaft is radially extended around the propeller shaft upstream of the propeller shaft. In a device provided with a plurality of reaction fins, a reaction fin for a ship characterized by setting a mounting angle of a reaction fin on a port side where a propeller blade descends at a time larger than a mounting angle of a reaction fin on an opposite port during forward rotation. apparatus. 3. In order to give a rotational flow in the direction opposite to the propeller rotation direction to the flow flowing into the propulsion screw propeller at the stern, the propeller shaft is radially extended around the propeller shaft upstream of the propeller propeller. In a device equipped with multiple reaction fins, the mounting angle of the reaction fins, which are respectively projected below the level of the propeller shaft on the same side, are successively reduced to less than the mounting angle of the reaction fins projected above. A reaction fin device for a ship, which is characterized in that 4. In order to give a rotational flow in a direction opposite to the propeller rotation direction to the flow flowing into the propulsion screw propeller at the stern part, the propeller shaft is radially extended around the propeller shaft on the upstream side of the screw propeller. In an apparatus equipped with a plurality of reaction fins, the distance l _O between the leading edge of the propeller and the trailing edge of the reaction fin at a position apart from the axial center of the propeller by about 35% of the propeller diameter D _{P is} the propeller diameter D _{P. A} reaction fin device for ships characterized by being selected in the range of 15% to 25% of _P. 5. In order to give a rotational flow in a direction opposite to the propeller rotation direction to the flow flowing into the propulsion screw propeller at the stern part, the propeller shaft is radially extended around the propeller shaft upstream of the propeller shaft. in apparatus provided with a plurality of reaction fin 10% to 20% of the wing chord length C _F the propeller diameter D _P of the reaction fin on about 35% away arc of axial center propeller diameter D _P of the propeller The reaction fin device for a ship, which is characterized in that 6. In order to give a rotational flow in a direction opposite to the propeller rotation direction to the flow flowing into the propulsion screw propeller at the stern, the propeller shaft is radially extended around the propeller shaft upstream of the propeller shaft. In a device equipped with multiple reaction fins, during forward rotation, the mounting angle of the reaction fin on the port side where the propeller blade descends is set to be larger than the mounting angle of the reaction fin on the opposite side, and the propeller shaft is The mounting angles of the reaction fins projecting downward from the level are successively reduced to less than the mounting angles of the reaction fin projecting upward, and the interval l _O of claim 4 and the chord length of claim 5 A reaction fin device for ships, which is equipped with C _F. 7. The propeller shaft is provided with a radial projection about the propeller shaft upstream of the screw propeller to impart a rotational flow in a direction opposite to the propeller rotation direction to the flow flowing into the propulsion screw propeller at the stern. In a device provided with a plurality of reaction fins, a relatively long upper reaction fin overhanging above the propeller shaft and a relatively long upper reaction fin, which are sequentially overhanging below the upper reaction fin and sequentially shorter than the upper reaction fin. A reaction fin device for a ship, comprising a middle reaction fin and a lower reaction fin, and further comprising claim 6.