Patent Description:
In a marine vessel having a thin body and a high service speed such as a research ship, a school ship, and a cable-laying ship, the flow velocity at the stern is high when the marine vessel sails in a service speed range. At this time, the negative pressure at the stern increases, and the sinking amount of the stern increases. Accordingly, the stern is enlarged in terms of the resistance of the ship, and the overall resistance of the ship rapidly increases. This tendency is particularly noticeable in high-speed vessels having a Froude number of <NUM> or greater, for example.

As a stern shape effective for reducing the resistance of a ship sailing in a service speed range, Patent Document <NUM> discloses a structure in which an additional member having a triangular cross section is provided at a stern end of an existing transom stern. The additional member protrudes from the stern end toward a rear side in a travel direction and is inclined so as to be positioned downward toward the rear side. The additional member changes a flow field at the stern to suppress wave breaking and wave making, thereby reducing wave-making resistance of the ship.

However, in a marine vessel including an opening for lowering, and lifting and housing, an investigation and monitoring instrument, an underwater sailing body, a small boat, or a fishing net at an end portion on a stern side, the additional member described in Patent Document <NUM> cannot be installed below the opening because the additional member interferes with an investigation and monitoring instrument or other component during lowering and lifting. Accordingly, in the case of a marine vessel including an opening for lowering, and lifting and housing, an investigation and monitoring instrument or other component at an end portion on a stern side, there remains a problem that the wave-making resistance of the ship cannot be sufficiently reduced.

The present disclosure has been made to solve the problem described above, and an object of the present disclosure is to provide a marine vessel that has a function for lowering, and lifting and housing, an investigation and monitoring instrument, an underwater sailing body, a small boat, a fishing net, or the like at an end portion on a stern side, and that is capable of reducing wave-making resistance of a ship.

In order to solve the problem described above, a marine vessel according to claim <NUM> is provided.

According to a marine vessel of the present disclosure, it is possible to provide a marine vessel that has a function for lowering, and lifting and housing, an investigation and monitoring instrument, an underwater sailing body, a small boat, a fishing net, or the like at an end portion on a stern side, and that is capable of reducing wave-making resistance of a ship.

Hereinafter, a marine vessel according to an embodiment of the present disclosure will be described with reference to the drawings. In the present embodiment, as an example of a marine vessel, a marine vessel having a thin body and a high service speed such as a research ship, a school ship, and a cable-laying ship will be described.

As illustrated in <FIG>, a marine vessel <NUM> is a marine vessel <NUM> that has a transom stern structure and is formed in a long and thin shape in a travel direction D1.

Hereinafter, a front side of the marine vessel <NUM> in the travel direction D1 may be referred to as a "bow side", and a rear side thereof in the travel direction D1 may be referred to as a "stern side". A direction that is orthogonal to the travel direction D1 of the marine vessel <NUM> along a horizontal plane may be referred to as a ship width direction D2.

The marine vessel <NUM> is a displacement-type marine vessel. As illustrated in <FIG> and <FIG>, the marine vessel <NUM> includes a ship <NUM>, a center skeg <NUM>, a propeller <NUM>, a rudder <NUM>, a stern door <NUM>, and a stern appendage <NUM>.

The ship <NUM> is a structure that floats on a water surface by generating buoyancy. The ship <NUM> includes a broadside <NUM>, a ship bottom <NUM>, an upper deck <NUM>, and a stern end <NUM>.

A pair of the broadsides <NUM> are disposed facing each other in the ship width direction D2. The ship bottom <NUM> connects lower portions of the pair of the broadsides <NUM>. In a side view, an end portion of the ship bottom <NUM> on the stern side is slightly inclined so as to be positioned upward toward the stern side. The upper deck <NUM> is provided across upper portions of the pair of the broadsides <NUM>. An upper structure such as a bridge (not illustrated) is installed at the upper deck <NUM>. The stern end <NUM> is provided across end portions of the pair of the broadsides <NUM> on the stern side.

The broadsides <NUM>, the ship bottom <NUM>, the upper deck <NUM>, and the stern end <NUM> give the ship <NUM> a box shape.

The center skeg <NUM> and the propeller <NUM> are provided at the ship bottom <NUM>.

The center skeg <NUM> is formed in a plate shape. The center skeg <NUM> is disposed along a ship bottom center line C that passes through an intermediate portion of the ship bottom <NUM> in the ship width direction D2 and extends along the travel direction D1. The center skeg <NUM> is provided closer to the stern side of the ship <NUM>.

The propeller <NUM> is provided on the stern side of the center skeg <NUM> and on a front side of the stern end <NUM> in the travel direction D1. Two of the propellers <NUM> are disposed facing each other in the ship width direction D2 across the ship bottom center line C. Each of the propellers <NUM> is connected to the ship bottom <NUM> via a propeller shaft <NUM>. The propeller shaft <NUM> extends from a leading end of the propeller <NUM> in the travel direction D1 through to the inside of the ship bottom <NUM>. A leading end portion of the propeller shaft <NUM> is connected to a motor (not illustrated) provided inside the ship bottom <NUM>. A trailing end portion of the propeller shaft <NUM> is rotatably supported by a shaft bracket <NUM>. The shaft bracket <NUM> includes a strut <NUM> and a tubular support part <NUM>. The strut <NUM> extends downward from the ship bottom <NUM>. The tubular support part <NUM> is formed in a tubular shape extending in the travel direction D1. The propeller shaft <NUM> is inserted into the tubular support part <NUM>. The tubular support part <NUM> rotatably supports the propeller shaft <NUM>. The propeller <NUM> is connected to a trailing end portion of the propeller shaft <NUM> on a rear side of the shaft bracket <NUM>. The propeller <NUM> is driven to rotate integrally with the propeller shaft <NUM> by a driving force of the motor (not illustrated) inside the ship bottom <NUM>. Rotation of the propeller <NUM> causes a propulsive force in the marine vessel <NUM>.

Note that the marine vessel <NUM> may include a single-shaft stern and one propeller <NUM> instead of the center skeg <NUM> and the two propellers <NUM>.

The rudder <NUM> is provided on the stern side of the center skeg <NUM> and on a front side of the stern end <NUM> in the travel direction D1. A pair of rudders <NUM> are provided facing each other in the ship width direction D2 across the ship bottom center line C. Each of the rudders <NUM> is provided on an outer side in the ship width direction D2 as compared to the propeller <NUM> that is positioned on the same side as the rudder <NUM> relative to the ship bottom center line C in the ship width direction D2. More specifically, the rudder <NUM> is installed on an outer side of an extension line of the rotation center line of the corresponding propeller <NUM> in the ship width direction D2. The rudder <NUM> is mounted at the ship bottom <NUM> via a rudder post <NUM>. The rudder post <NUM> protrudes downward from the ship bottom <NUM>. The front portion of an upper end of the rudder <NUM> is connected to a lower end of the rudder post <NUM>. The angle of the rudder <NUM> around the rudder post <NUM> is configured to be variable.

Hereinafter, a perpendicular line passing through an intersection of a load water line WL and a bow 1a of the marine vessel <NUM> and extending in a vertical direction is referred to as a foremost perpendicular line F. , and a perpendicular line passing through a center axis of the rudder post <NUM> and extending in the vertical direction is referred to as an aftermost perpendicular line A. A distance in the travel direction D1 between the foremost perpendicular line F. and the aftermost perpendicular line A. is referred to as an inter-perpendicular length Lpp. A distance between the foremost perpendicular line F. and a perpendicular line passing through an intersection of a trailing end portion of the stern of the marine vessel <NUM> (in the present embodiment, a flap <NUM> to be described later) and the load water line WL and extending in the vertical direction is referred to as a water line length Lwl.

As illustrated in <FIG>, a housing portion <NUM> is provided inside the ship <NUM> on the stern side. In <FIG>, illustration of the propellers <NUM> and the rudders <NUM> is omitted.

For example, a small boat SB is lifted and housed in the housing portion <NUM>. The housing portion <NUM> is used as, for example, a dock for housing the small boat SB. Note that the housing portion <NUM> may house, for example, an investigation and monitoring instrument, an underwater sailing body, a fishing net, and the like apart from the small boat SB. The housing portion <NUM> includes a slope <NUM> at a lower portion thereof. In a side view, the slope <NUM> is inclined so as to be positioned downward toward the stern side. The slope <NUM> serves as a so-called ramp for guiding the small boat SB into the ship <NUM>.

As illustrated in <FIG>, the stern end <NUM> is the stern end <NUM> of a so-called transom stern formed in a rectangular shape. Hereinafter, an end face of the stern end <NUM> on the rear side in the travel direction D1 may be referred to as a stern end face <NUM>.

The stern end face <NUM> is formed rising from an end portion of the ship <NUM> on the stern side. The stern end face <NUM> is slightly inclined relative to a vertical plane so as to be positioned closer to the bow side toward the bottom of the stern end face <NUM>. A stern opening <NUM> is formed in the stern end face <NUM>.

The stern opening <NUM> opens toward the stern side. The stern opening <NUM> allows the housing portion <NUM> to communicate with an external space. The stern opening <NUM> includes an upper opening <NUM> and a lower opening <NUM>. The upper opening <NUM> is formed in a rectangular shape in a front view. An upper end of the upper opening <NUM> extends in the ship width direction D2. The lower opening <NUM> is connected to a lower end of the upper opening <NUM> and extends from the lower end of the upper opening <NUM> to a lower end of the stern end face <NUM>. The lower opening <NUM> is formed in a trapezoidal shape having a width tapering toward the bottom of the lower opening <NUM> in a front view. A lower end of the lower opening <NUM> is connected to an end portion of the slope <NUM> on the stern side.

Hereinafter, side ends of the lower opening <NUM> facing each other in the ship width direction D2 may be referred to as lower side ends 12a.

A stern door <NUM> is provided at the stern opening <NUM>.

The stern door <NUM> can open and close the stern opening <NUM>. The stern door <NUM> is attached to an upper end of the stern opening <NUM> so as to be rotatable around the upper end. Accordingly, the stern door <NUM> is rotatable between a closed position P1 at which the stern opening <NUM> is closed and an open position P2 at which the stern opening <NUM> is open. The stern door <NUM> is positioned in the stern opening <NUM> at the closed position P1. A rear surface of the stern door <NUM> is substantially flush with the stern end face <NUM> at the closed position P1. The stern door <NUM> prevents waves from entering the housing portion <NUM> at the closed position P1. The stern door <NUM> is connected to the upper end of the stern opening <NUM> and is positioned on the stern side of the stern opening <NUM> at the open position P2.

The stern appendage <NUM> is provided at an end portion of the marine vessel <NUM> on the stern side. The stern appendage <NUM> includes a flap <NUM> and a wedge <NUM>.

The flap <NUM> is provided at the stern end face <NUM>. A pair of flaps <NUM> are provided separated from each other in the ship width direction D2 while avoiding the stern opening <NUM>. The pair of flaps <NUM> are formed in the same shape.

The flap <NUM> protrudes from the stern end face <NUM> toward the stern side. The flap <NUM> extends in the ship width direction D2. The flap <NUM> is provided such that the position in the ship width direction D2 of an end portion of the flap <NUM> on an inner side in the ship width direction D2 overlaps with the position in the ship width direction D2 of the stern opening <NUM>. The flap <NUM> is formed in a triangular cross-sectional shape that becomes smaller in height in the vertical direction toward the stern side in a side view. The flap <NUM> includes an upper flap surface <NUM> and a lower flap surface <NUM>.

The upper flap surface <NUM> is inclined so as to be positioned downward toward the stern side. The upper flap surface <NUM> includes a first upper surface 53a and a second upper surface 53b.

The first upper surface 53a is a portion of the upper flap surface <NUM> of which the position in the ship width direction D2 overlaps with the position in the ship width direction D2 of the stern opening <NUM>. The first upper surface 53a is formed in a planar shape along the lower side end 12a of the stern opening <NUM>.

The second upper surface 53b is connected to the first upper surface 53a and extends outward from the first upper surface 53a in the ship width direction D2. The second upper surface 53b is formed in a curved surface shape so as to be positioned downward toward the outer side in the ship width direction D2.

The lower flap surface <NUM> extends to the stern side and is continuous from the ship bottom <NUM>. The lower flap surface <NUM> extends in a region at or below a lower end of the stern end face <NUM>. In the present embodiment, the lower flap surface <NUM> is formed in a planar shape so as to be positioned downward toward the stern side.

Of the flap <NUM> described above, a portion including the second upper surface 53b is formed so that the thickness in the vertical direction becomes greater toward an inner side in the ship width direction D2.

Here, a height from a base line BL of the ship bottom <NUM> to a lower end of the flap <NUM> in the vertical direction is H1, and a height from the base line BL of the ship bottom <NUM> to the load water line WL in the vertical direction is H2. Also, a length of the flap <NUM> in the travel direction D1 is L1.

In the marine vessel <NUM> according to the present embodiment, a Froude number Fn of a designed speed is <NUM> or greater and <NUM> or less.

In particular, when the marine vessel <NUM> is a displacement-type marine vessel, the inter-perpendicular length Lpp is <NUM> or greater and <NUM> or less, and the Froude number Fn of a designed speed is <NUM> or greater and <NUM> or less, the height H1 from the base line BL of the ship bottom <NUM> to the lower end of the flap <NUM> is preferably set to be <NUM>% or greater and <NUM>% or less of the height H2 from the base line BL of the ship bottom <NUM> to the load water line WL, and the length L1 of the flap <NUM> in the travel direction D1 is preferably set to be <NUM>% or greater and <NUM>% or less of the inter-perpendicular length Lpp.

The wedge <NUM> is provided at an end portion of the ship bottom <NUM> on the stern side. The wedge <NUM> is provided without protruding on the stern side of the stern end face <NUM>. The wedges <NUM> protrudes downward from the ship bottom <NUM>. The wedge <NUM> is provided between the pair of flaps <NUM> in the ship width direction D2. The wedge <NUM> extends in the ship width direction D2. The wedge <NUM> is provided such that the positions in the ship width direction D2 of end portions of the wedge <NUM> on outer sides in the ship width direction D2 overlap with the positions in the ship width direction D2 of an end portion of the respective flaps <NUM> on an inner side in the ship width direction D2. That is, end portions of the wedge <NUM> on outer sides in the ship width direction D2 overlap with an end portion of the respective flaps <NUM> on an inner side in the ship width direction D2. The wedge <NUM> is formed in a symmetrical shape with respect to the ship bottom center line C. The wedge <NUM> is formed in a triangular cross-sectional shape having a height reducing in the vertical direction toward the bow side in a side view. The wedge <NUM> includes a rear wedge surface <NUM> and a lower wedge surface <NUM>.

The rear wedge surface <NUM> is formed along the stern end face <NUM>. The rear wedge surface <NUM> is slightly inclined with respect to a vertical plane so as to be positioned closer to the bow side toward the bottom of the rear wedge surface <NUM> in a side view. The rear wedge surface <NUM> is formed in a trapezoidal shape having a width narrowing toward the bottom of the rear wedge surface <NUM> in a front view.

The lower wedge surface <NUM> is smoothly connected to the ship bottom <NUM>. The lower wedge surface <NUM> includes a first lower surface 56a and a second lower surface 56b.

The first lower surface 56a is a portion of the lower wedge surface <NUM> that is positioned on inner sides of the pair of flaps <NUM> in the ship width direction D2. The first lower surface 56a is formed in a planar shape extending from the ship bottom <NUM> to the stern side so as to be positioned downward toward the stern side in a side view. The first lower surface 56a connects the ship bottom <NUM> and a lower end of the rear wedge surface <NUM>.

A pair of second lower surfaces 56b are provided on outer sides of the first lower surface 56a in the ship width direction D2. Each of the second lower surfaces 56b extends from a side end of the first lower surface 56a on an outer side in the ship width direction D2 farther toward the outer side in the ship width direction D2. The second lower surface 56b smoothly connects the side end of the first lower surface 56a on the outer side in the ship width direction D2 and the ship bottom <NUM>. A trailing end of the second lower surface 56b on the stern side is connected to a side end of the rear wedge surface <NUM> on an outer side in the ship width direction D2. The second lower surface 56b is formed in a planar shape so as to come closer to the ship bottom <NUM> toward an outer side in the ship width direction D2. Also, the second lower surface 56b is formed in a triangular shape so that the dimension in the travel direction D1 becomes smaller toward an outer side in the ship width direction D2 in a plan view.

The marine vessel <NUM> according to the present embodiment achieves the following operational effects.

In the present embodiment, the marine vessel <NUM> includes, at the stern end face <NUM>, the pair of flaps <NUM> separated from each other in the ship width direction D2 while avoiding the stern opening <NUM>.

According to the present embodiment, the marine vessel <NUM> can lower, and lift and house, an investigation and monitoring instrument, an underwater sailing body, a small boat SB, a fishing net, and the like at an end portion of the marine vessel <NUM> on the stern side via the stern opening <NUM>. Furthermore, the marine vessel <NUM> can suppress wave making around the stern by the flaps <NUM> without causing interference between the flaps <NUM> and an investigation and monitoring instrument or similar component. Accordingly, it is possible to reduce wave-making resistance at the stern and improve fuel economy performance. Furthermore, the improved fuel economy performance can reduce transportation costs.

In the present embodiment, the flap <NUM> includes the lower flap surface <NUM> extending to the stern side and continuous from the ship bottom <NUM>. The lower flap surface <NUM> extends in a region at or below a lower end of the stern end face <NUM>.

According to the present embodiment, the marine vessel <NUM> can suppress wave making around the stern by the flaps <NUM>. This makes it possible to further reduce wave-making resistance at the stern and further improve fuel economy performance.

In the present embodiment, the wedge <NUM> is provided at an end portion of the ship bottom <NUM> on the stern side between the pair of flaps <NUM> in the ship width direction D2.

According to the present embodiment, the marine vessel <NUM> can further suppress wave making around the stern by the flaps <NUM> and the wedge <NUM>. This makes it possible to further reduce wave-making resistance at the stern and further improve fuel economy performance.

In the present embodiment, the positions in the ship width direction D2 of end portions of the wedge <NUM> on outer sides in the ship width direction D2 overlap with the positions in the ship width direction D2 of an end portion of the respective flaps <NUM> on an inner side in the ship width direction D2.

According to the present embodiment, a flow passing between each of the flaps <NUM> and the wedge <NUM> can be suppressed. This makes it possible to further reduce wave-making resistance at the stern and further improve fuel economy performance.

Also, by using the flaps <NUM> and the wedge <NUM> in combination, the water line length Lwl can be increased by the length of the flaps <NUM> as compared to a case where only the wedge <NUM> is provided throughout the ship bottom <NUM> in the ship width direction D2. This makes it possible to further reduce wave-making resistance at the stern and further improve fuel economy performance.

In the present embodiment, the wedge <NUM> includes the lower wedge surface <NUM> smoothly connected to the ship bottom <NUM>.

According to the present embodiment, the generation of flow separation at end portions of the wedge <NUM> on the ship width direction D2 can be suppressed. This makes it possible to further reduce wave-making resistance at the stern and further improve fuel economy performance.

In the present embodiment, a Froude number Fn of a designed speed of the marine vessel <NUM> is <NUM> or greater and <NUM> or less.

According to the present embodiment, the effect of reducing wave making around the stern by the stern appendage <NUM> such as the flaps <NUM> and the wedge <NUM> can be more favorably achieved.

In particular, the effect of reducing wave-making resistance by the flaps <NUM> and the wedge <NUM> is most effectively achieved when the marine vessel <NUM> is a displacement-type marine vessel, the inter-perpendicular length Lpp is <NUM> or greater and <NUM> or less, the Froude number Fn of a designed speed is <NUM> or greater and <NUM> or less, and the marine vessel <NUM> includes the center skeg <NUM> and two propellers <NUM> or the marine vessel <NUM> includes a single-shaft stern and one propeller <NUM>. Furthermore, the effect of reducing wave-making resistance by the flaps <NUM> and the wedge <NUM> is further favorably achieved when the height H1 from the base line BL of the ship bottom <NUM> to the lower end of the flap <NUM> is set to be <NUM>% or greater and <NUM>% or less of the height H2 from the base line BL of the ship bottom <NUM> to the load water line WL, and the length L1 of the flap <NUM> in the travel direction D1 is set to be <NUM>% or greater and <NUM>% or less of the inter-perpendicular length Lpp.

The effect of reducing wave-making resistance is more favorably achieved when a vertex angle that is an angle between the ship bottom center line C (see <FIG>) of the ship bottom <NUM> and a leading end of the lower flap surface <NUM> is set to be equal to or less than a vertex angle that is an angle between the ship bottom center line C of the ship bottom <NUM> and a leading end of the lower wedge surface <NUM>. Furthermore, the effect of reducing wave-making resistance is most effectively achieved when the vertex angle between the ship bottom center line C of the ship bottom <NUM> and the leading end of the lower flap surface <NUM> is <NUM> degrees or greater and <NUM> degrees or less and the vertex angle between the ship bottom center line C of the ship bottom <NUM> and the leading end of the lower wedge surface <NUM> is <NUM> degrees or greater and <NUM> degrees or less.

In the present embodiment, the marine vessel <NUM> includes the stern door <NUM> that opens and closes the stern opening <NUM>.

According to the present embodiment, for example, when following waves are received from the stern side during sailing, an increase in resistance that may occur in the waves can be suppressed by disposing the stern door <NUM> at the closed position P1. This makes it possible to further reduce wave-making resistance at the stern.

In the present embodiment, a portion of the flap <NUM> including the second upper surface 53b is formed so that the thickness in the vertical direction becomes greater toward an inner side in the ship width direction D2.

According to the present embodiment, the strength of the flap <NUM> can be ensured to such a degree that the flap <NUM> can sufficiently withstand wave making around the stern.

Next, a result of a water tank test in which the effect of the above-described stern appendage <NUM> according to the present embodiment was confirmed will be described with reference to <FIG>. In <FIG>, the horizontal axis represents Froude number Fn, and the vertical axis represents the residual resistance coefficient Cr. Here, the residual resistance coefficient Cr is a coefficient indicating a magnitude of residual resistance, and the residual resistance contains viscous pressure resistance and wave-making resistance.

The solid line in the drawing indicates the water tank test result of a comparative example (the marine vessel <NUM> without the stern appendage <NUM>), and the dashed line indicates the water tank test result of the marine vessel <NUM> including the stern appendage <NUM> according to the present embodiment.

As the test results, the transitions of the residual resistance coefficient Cr relative to the Froude number Fn in a range of <NUM> or greater to <NUM> or less is shown in <FIG>. In each of the test results shown in <FIG>, the residual resistance coefficient Cr transitions in a range of <NUM> or greater to <NUM> or less.

As shown in <FIG>, it can be easily understood that, while the transition of the residual resistance coefficient Cr relative to the Froude number Fn of the marine vessel <NUM> including the stern appendage <NUM> according to the present embodiment is substantially the same in form as that of the residual resistance coefficient Cr of the comparative example, the residual resistance coefficient Cr of the marine vessel <NUM> including the stern appendage <NUM> is lower than that of the comparative example in a range in which the Froude number Fn is larger than <NUM>. In particular, a reduction ratio of the residual resistance coefficient Cr is large in a range in which the Froude number Fn is around <NUM>. When the Froude number Fn is <NUM>, the residual resistance coefficient Cr is reduced by <NUM>% from the comparative example.

As described above, the wave-making resistance can be reduced by disposing the stern appendage <NUM> according to the present embodiment at the stern. That is, according to the marine vessel <NUM> including the stern appendage <NUM> according to the present embodiment, it is possible to mainly suppress the wave-making resistance contained in the residual resistance and improve fuel economy performance. The effect of reducing wave-making resistance by the stern appendage <NUM> is indicated by the reduction in the residual resistance coefficient Cr in the test result shown in <FIG>. Thus, it can be said that the reduction in wave-making resistance by the stern appendage <NUM> is particularly favorably achieved in a range in which the Froude number Fn is around <NUM>.

Next, a modification example will be described with reference to <FIG>.

As in the modification example illustrated in <FIG>, positions in the ship width direction D2 of both end portions of the wedge <NUM> on outer sides in the ship width direction D2 need not overlap with the positions of the respective flaps <NUM> in the ship width direction D2. In the present modification example, each of both end portions of the wedge <NUM> on outer sides in the ship width direction D2 is formed in a planar shape substantially perpendicular to the ship bottom <NUM>.

An embodiment according to the present disclosure has been described in detail with reference to the drawings. However, the specific configuration of the present disclosure is not limited to this embodiment. Design change without departing from the main gist of the present disclosure or the like is also included.

Note that, in the embodiment described above, the marine vessel <NUM> is a displacement-type marine vessel, but the present invention is not limited thereto. The marine vessel <NUM> may be a planning-type marine vessel.

Note that, in the embodiment described above, the lower opening <NUM> of the stern opening <NUM> extends to the lower end of the stern end face <NUM>, but the present invention is not limited thereto. The lower end of the lower opening <NUM> may be positioned above the lower end of the stern end face <NUM>, or the lower opening <NUM> may extend to a position at which the lower end of the lower opening <NUM> overlaps with the wedge <NUM>. When the lower opening <NUM> extends to the position at which the lower end of the lower opening <NUM> overlaps with the wedge <NUM>, the small boat SB or the like can be lifted and housed more easily than when the range of the lower opening <NUM> is delimited at or above the lower end of the stern end face <NUM>.

Note that, in the embodiment described above, a case where the stern opening <NUM> is provided with the stern door <NUM> has been described, but the present invention is not limited thereto. The stern opening <NUM> need not be provided with the stern door <NUM>. In this case, the marine vessel <NUM> is, for example, a fishing ship or a research ship, and the slope <NUM> connects the lower end of the stern opening <NUM> and the upper surface of the upper deck <NUM>. In the marine vessel <NUM>, a fishing net, an investigation and monitoring instrument, or the like can be lowered, and lifted and housed, through the slope <NUM> and the stern opening <NUM>.

Note that, in the embodiment described above, the lower flap surface <NUM> is inclined so as to be positioned downward toward the stern side, but the present invention is not limited thereto. The lower flap surface <NUM> may be provided along a horizontal plane.

Note that, in the embodiment described above, the rudder <NUM> is installed on an outer side of an extension line of the rotation center line of the corresponding propeller <NUM> in the ship width direction D2, but the present invention is not limited thereto. The rudder <NUM> may be disposed on the extension line of the rotation center line of the propeller <NUM>.

The marine vessel <NUM> according to each embodiment of the present disclosure is understood as follows, for example.

According to the present aspect, the marine vessel <NUM> can lower, and lift and house an investigation and monitoring instrument, an underwater sailing body, a small boat SB, a fishing net, or the like at an end portion on the stern side via the stern opening <NUM>. Furthermore, the marine vessel <NUM> can suppress wave making around the stern by the flaps <NUM> without causing interference between the flaps <NUM> and an investigation and monitoring instrument, or the like.

(<NUM>) A marine vessel <NUM> according to a second aspect is the marine vessel <NUM> according to (<NUM>) above, wherein each of the flaps <NUM> includes a lower flap surface <NUM> extending to the stern side and continuous from the ship bottom <NUM>, and the lower flap surface <NUM> may extend in a region at or below a lower end of the stern end face <NUM>.

According to the present aspect, the marine vessel <NUM> can suppress wave making around the stern by the flaps <NUM>.

(<NUM>) A marine vessel <NUM> according to a third aspect is the marine vessel <NUM> according to (<NUM>) or (<NUM>) above, wherein a wedge <NUM> may be provided at an end portion of the ship bottom <NUM> on the stern side between the pair of flaps <NUM> in the ship width direction D2.

According to the present aspect, the marine vessel <NUM> can further suppress wave making around the stern by the flaps <NUM> and the wedge <NUM>.

(<NUM>) A marine vessel <NUM> according to a fourth aspect is the marine vessel <NUM> according to (<NUM>) above, wherein positions in the ship width direction D2 of end portions of the wedge <NUM> on outer sides in the ship width direction D2 may overlap with positions in the ship width direction D2 of an end portion of the respective flaps <NUM> on an inner side in the ship width direction D2.

According to the present aspect, a flow passing between each of the flaps <NUM> and the wedge <NUM> can be suppressed.

(<NUM>) A marine vessel <NUM> according to a fifth aspect is the marine vessel <NUM> according to (<NUM>) or (<NUM>) above, wherein the wedge <NUM> may include a lower wedge surface <NUM> smoothly connected to the ship bottom <NUM>.

According to the present aspect, the generation of flow separation at end portions of the wedge <NUM> on the ship width direction D2 can be suppressed.

(<NUM>) A marine vessel <NUM> according to a sixth aspect is the marine vessel <NUM> according to any one of (<NUM>) to (<NUM>) above, wherein a Froude number Fn of a designed speed may be <NUM> or greater and <NUM> or less.

Claim 1:
A marine vessel (<NUM>) comprising:
a ship (<NUM>);
a pair of flaps (<NUM>); and
a wedge (<NUM>) provided at an end portion of a ship bottom (<NUM>) on a stern side between the pair of flaps (<NUM>) in a ship width direction (D2),
the ship (<NUM>) including:
the ship bottom (<NUM>),
a stern end face (<NUM>) rising from an end portion of the ship bottom (<NUM>) on the stern side, and
a stern opening (<NUM>) formed in the stern end face (<NUM>),
the pair of flaps (<NUM>) being provided, at the stern end face (<NUM>), separated from each other in the ship width direction (D2) while avoiding the stern opening (<NUM>), wherein
positions in the ship width direction (D2) of end portions of the wedge (<NUM>) on outer sides in the ship width direction (D2) overlap with positions in the ship width direction (D2) of an end portion of the respective flaps on an inner side in the ship width direction (D2), and
the wedge (<NUM>) includes a lower wedge surface (<NUM>) smoothly connected to the ship bottom (<NUM>),
wherein
the lower wedge surface (<NUM>) includes a first lower surface (56a) and a pair of second lower surfaces (56b),
the first lower surface (56a) is formed in a planar shape extending from the ship bottom (<NUM>) to the stern side so as to be positioned downward toward the stern side in a side view, wherein
the pair of second lower surfaces (56b) are provided on outer sides of the first lower surface (56a) in the ship width direction (D2), the pair of second lower surfaces (56b) smoothly connect the side end of the first lower surface (56a) on the outer side in the ship width direction (D2) and the ship bottom (<NUM>), and wherein
the pair of second lower surfaces (56b) are formed in a triangular shape so that the dimension in the travel direction (D1) becomes smaller toward an outer side in the ship width direction (D2) in a plan view.