Method for designing and modeling the profile of a ship stern flow guide fin
By employing the three-view method and segmented design approach, the standardization issues of two-dimensional design and three-dimensional modeling of guide fins were resolved, enabling rapid and concise expression and modeling of guide fin shapes. This method is applicable to various stern configurations and improves design efficiency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2026-04-02
- Publication Date
- 2026-07-31
AI Technical Summary
In the existing technology, the two-dimensional design and drawing of the stern guide fin of a ship lacks a standardized and parameterized process, making it difficult to accurately identify the smoothness of the three-dimensional shape, resulting in manufacturing difficulties. Furthermore, when modifying parameters, it is necessary to make significant adjustments to the associated parameters, which is a large workload.
The three-dimensional view method is adopted, and the cross-sectional features of the guide section, duct section and rudder platform section are drawn. Combined with the addition of longitudinal curves in three-dimensional space, a cross-shaped three-dimensional surface is formed. The guide fins are designed in sections to adapt to different stern shapes, providing a standardized parametric design process.
It enables rapid generation of 2D drawings and 3D modeling of guide fins, improving design efficiency, facilitating modifications, and is applicable to various stern forms, adapting to different stern appendage design requirements.
Smart Images
Figure CN121959760B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of marine technology, and in particular to a method for designing and modeling the shape of a stern guide fin on a ship. Background Technology
[0002] Ships with ducted propellers are currently widely used in various engineering vessels and other types of ships. Due to the upward stern shape of conventional ships, the rudder and the duct of the ducted propeller cannot be directly connected to the main hull. Therefore, various types of ship appendages have emerged, such as bosses, supports, tunnels, or guide fins.
[0003] For specially shaped guide fins, due to their relatively large size and extension from the tip of the duct to above the rudder, their three-dimensional shape cannot be obtained using simple two-dimensional contours through methods such as stretching, sweeping, and rotation. Instead, they are composed of multiple complex curved surfaces. The two-dimensional design and drawing of such complex guide fins relies heavily on the designer's experience, involving manual drawing based on the three-dimensional correspondence of three-dimensional views. The shapes are relatively simple, often using straight lines for transitions. Different designers have different understandings and requirements for guide fin shapes, and the shapes of the sterns of different ships vary, with numerous types of rudder and ducted propeller ducts. Therefore, the guide fins for each type of ship require individual design, and the methods for representing guide fin shapes are neither standardized nor fixed. Furthermore, since most guide fin designs remain at the two-dimensional drawing stage, it is difficult to identify whether the three-dimensional shape is smooth, which poses challenges to the lofting work during the shipyard manufacturing phase. Currently, there is no standardized or parametric design process for this type of complex-shaped guide fin, and it is impossible to directly complete the 3D model of this shape. Furthermore, due to the complexity of the shape of the guide fin, many parameters need to be defined, and once some parameters need to be modified, it often involves changes in related parameters, resulting in a large amount of modification work.
[0004] Therefore, there is an urgent need to design a method for drawing and modeling the shape of the stern guide fin of a ship in order to solve the above technical problems. Summary of the Invention
[0005] The purpose of this invention is to propose a method for designing and modeling the shape of a ship's stern guide fin. This method can be used to design smooth two-dimensional drawings of the guide fin and quickly complete the modeling of its three-dimensional shape by using a standardized process of parametric design for different ship stern shapes and the size and position of the guide ducts and rudders used.
[0006] To achieve this objective, the present invention adopts the following technical solution:
[0007] This invention provides a method for designing and modeling the shape of a stern guide fin on a ship. The guide fin includes a guide section, a duct section, and a rudder platform section connected in sequence. The duct section connects the duct to the main hull, and the rudder platform section connects the rudder to the main hull. The method includes the following steps:
[0008] The stern profile of the ship is expressed in the three-dimensional view. Then, the stern rib profile is imported into the stern view of the three-dimensional view. The stern outline is imported into the side and top views of the three-dimensional view. The outlines of the rudder and duct are imported into the three-dimensional view.
[0009] The cross-sectional features of the guide section, duct section, and rudder platform section are obtained, and each cross-sectional line is drawn in two dimensions on the three-dimensional view. The cross-sectional lines of the guide section include the center line and outline of the inner steel pipe, the center line and outline of the outer steel pipe, the outer oblique tangent line of the guide section, the inner oblique tangent line of the guide section, the arc section of the channel, and the top intersection line of the guide section. The cross-sectional lines of the duct section include the top intersection line of the duct section, the outer oblique tangent line of the duct section, and the inner oblique tangent line of the duct section. The cross-sectional lines of the rudder platform section include the center line and outline of the stern steel pipe, the top intersection line of the rudder platform section, the outer oblique tangent line of the rudder platform section, the inner oblique tangent line of the rudder platform section, and the outline of the rudder platform section.
[0010] Based on the coordinates of the control points of each cross section, draw each cross section in three-dimensional space;
[0011] Based on the shape characteristics of the guide fins, longitudinal curves are added in three-dimensional space to connect the various cross sections, thereby forming a three-dimensional surface with an interlaced grid.
[0012] Optionally, an inner steel pipe is provided on the inner side of the guide section, and an outer steel pipe is provided on the outer side of the guide section. The front ends of the inner steel pipe and the outer steel pipe are inserted into the hull of the main ship, and the rear ends of the inner steel pipe and the outer steel pipe are inserted into the front end of the guide pipe.
[0013] The diameter d1 of the inner steel pipe and the diameter d2 of the outer steel pipe are determined according to the size of the conduit, and both d1 and d2 are smaller than the thickness of the front end of the conduit.
[0014] The X-coordinates of the rear end centers of the inner and outer steel pipes are consistent with the front end position of the conduit. The Y and Z coordinates of the rear end centers of the inner and outer steel pipes should be ensured that the circular cross-sections of the inner and outer steel pipes are within the thickness range of the front end of the conduit.
[0015] The positions of the center of the front end of the inner steel pipe and the center of the front end of the outer steel pipe should be such that the front ends of the inner steel pipe and the outer steel pipe are completely submerged within the main hull, and the X coordinates of the center of the front end of the inner steel pipe and the center of the front end of the outer steel pipe are the same, with the one closer to the bow being the reference.
[0016] Based on the coordinate positions of the front end center of the inner steel pipe, the rear end center of the inner steel pipe, the front end center of the outer steel pipe, the rear end center of the outer steel pipe, and the diameters of the outer steel pipe and the inner steel pipe, draw the center line and outline of the inner steel pipe, the center line and outline of the outer steel pipe, and the cross section lines at each rib position in the three-way view.
[0017] The cross-sections of the inclined inner and outer steel pipes are simplified to perfect circles.
[0018] Optionally, straight steel plates are provided on both sides of the guide section to connect the inner steel pipe, the outer steel pipe and the main hull together, so as to form the outer oblique line and the inner oblique line of the guide section on each cross section line of the stern view;
[0019] The outer oblique tangent of the guide section is a straight line segment, which forms a first angle α with the vertical direction. The bottom end of the outer oblique tangent of the guide section is tangent to the outer steel pipe. The top end of the outer oblique tangent of the guide section extends to a first height H, that is, the top point of the outer oblique tangent of the guide section intersects with the main hull at the top intersection point of the guide section.
[0020] The inner oblique tangent of the guide section is a straight line segment, which forms a second angle β with the vertical direction. The bottom end of the inner oblique tangent of the guide section is tangent to the inner steel pipe, and the top end of the inner oblique tangent of the guide section extends to the first height H, that is, the top point of the inner oblique tangent of the guide section intersects with the main hull at the top intersection point of the guide section.
[0021] The first height H is greater than the lowest point of the ship's stern plate, and the first included angle α and the second included angle β may be the same or different.
[0022] Optionally, a guide channel leader is set according to the stern hull shape and the direction of water flow. The perpendicular bisector of the line connecting the centers of the inner steel pipe and the outer steel pipe is drawn. The perpendicular bisector intersects the guide channel leader at a point, which is the center of the channel arc segment. An arc segment tangent to the inner steel pipe and the outer steel pipe is drawn with the center of the channel arc segment as the center. This is the channel arc segment.
[0023] At certain rib locations, the arc segment of the channel intersects with the main hull to form an intersection point, which is the intersection point of the outer side of the arc segment and the intersection point of the inner side of the arc segment.
[0024] Optionally, the coordinates of the inner top intersection point of the guide section, the outer top intersection point of the guide section, the inner intersection point of the channel arc section, and the outer intersection point of the channel arc section on each cross section line in the stern view are respectively mapped to the side view and the top view, and then smoothly connected in sequence to form the top intersection line of the guide section, which is the intersection line between the guide section and the main hull.
[0025] The outer intersection point of the channel arc segment is obtained based on the center and outline of the main hull, the outer steel pipe, the center and outline of the inner steel pipe, and the guide channel lead line.
[0026] The inner intersection point of the arc segment of the channel is obtained based on the center and outline of the main hull, the outer steel pipe, the center and outline of the inner steel pipe, and the guide line of the channel.
[0027] The outer top intersection point of the guide section is obtained based on the centerline and outline of the main hull and the outer steel pipe, as well as the straight steel plates set on both sides of the guide section.
[0028] The inner top intersection point of the guide section is obtained based on the centerline and outline of the main hull and the inner steel pipe, as well as the straight steel plates set on both sides of the guide section.
[0029] Optionally, the top intersection line of the guide segment in any view can be smoothly extended backward to the rear end of the catheter, connecting with and being tangent to the top intersection line of the guide segment, thus forming the top intersection line of the catheter segment, and corresponding to the other two views.
[0030] Optionally, in the cross-sectional lines of each rib in the stern view, through the point on each cross-sectional line where the top intersection line of the catheter segment is located, draw the outer oblique line and the inner oblique line of the catheter segment, which form a first preset angle with the vertical direction. The bottom end of the outer oblique line and the bottom end of the inner oblique line of the catheter segment are submerged in the catheter, and the top end of the outer oblique line and the top end of the inner oblique line of the catheter segment extend to a first height H.
[0031] Optionally, the diameter and position of the stern steel pipe are determined according to the characteristics of the ship type. The stern steel pipe is placed at or in front of the stern end plate of the ship. Based on the inclination angle of the inner oblique tangent line of the guide section, the outer oblique tangent line of the guide section, the inner oblique tangent line of the guide section, and the outer oblique tangent line of the guide section, the stern steel pipe is designed to be placed at an inclination.
[0032] Based on the position and size of the rudder, determine the height H_rp of the rudder platform section, which is the height of the bottom end of the stern steel pipe. Determine the diameter of the stern steel pipe, the coordinates of the top end of the stern steel pipe, and the coordinates of the bottom end of the stern steel pipe. Draw the center line and outline of the stern steel pipe in the three-way view.
[0033] Optionally, the top intersection line of the guide tube segment in any view can be smoothly extended backward to the stern steel pipe, connecting and tangent to the top of the stern steel pipe, thus forming the top intersection line of the rudder platform segment, which corresponds to the other two views.
[0034] Optionally, in the cross-sectional lines of each rib in the stern view, through the point on each cross-sectional line where the top intersection line of the rudder platform segment intersects, draw the outer oblique line and the inner oblique line of the rudder platform segment, which form a second preset angle with the vertical direction. The bottom end of the outer oblique line and the bottom end of the inner oblique line of the rudder platform segment extend to the height H_rp of the rudder platform segment, and the top end of the outer oblique line and the top end of the inner oblique line of the rudder platform segment extend to the first height H.
[0035] By sequentially and smoothly connecting the bottom ends of the inner oblique tangent line of the rudder platform segment and the bottom ends of the outer oblique tangent line of the rudder platform segment, the projection of the outline of the rudder platform segment in the stern view is obtained;
[0036] Based on each rib, the bottom coordinates of the outer oblique tangent line of the rudder platform section and the bottom coordinates of the inner oblique tangent line of the rudder platform section are drawn and smoothly connected in the side view and top view.
[0037] The beneficial effects of the present invention include at least the following:
[0038] This invention provides a method for designing and modeling the shape of a ship's stern guide fin. Based on the different shape characteristics of the fore and aft parts of the guide fin, the guide fin is divided into three sections—fore, middle, and aft—by two thick dashed lines, representing the front and rear ends of the duct. These sections are the guide section, the duct section, and the rudder platform section, respectively. The guide section is located in front of the duct. The duct section is located above the duct to connect the duct to the main hull. The rudder platform section is located behind the duct and above the rudder to connect the rudder to the main hull.
[0039] The method for drawing and modeling the shape of the stern guide fin of a ship includes the following steps: expressing the shape of the stern of the ship in three-dimensional views, then importing the stern rib shape lines into the stern view of the three-dimensional views, importing the stern outline into the side view and top view of the three-dimensional views, and importing the outline of the rudder and guide tube into the three-dimensional views. The cross-sectional features of the guide section, duct section, and rudder platform section are obtained, and each cross-sectional line is drawn in two dimensions on the three-dimensional view. The cross-sectional lines of the guide section include the centerline and outline of the inner steel pipe, the centerline and outline of the outer steel pipe, the outer oblique tangent of the guide section, the inner oblique tangent of the guide section, the arc section of the channel, and the top intersection line of the guide section. The cross-sectional lines of the duct section include the top intersection line of the duct section, the outer oblique tangent of the duct section, and the inner oblique tangent of the duct section. The cross-sectional lines of the rudder platform section include the centerline and outline of the stern steel pipe, the top intersection line of the rudder platform section, the outer oblique tangent of the rudder platform section, the inner oblique tangent of the rudder platform section, and the outline of the rudder platform section. According to the control point coordinates of each cross-sectional line, each cross-sectional line is drawn in three-dimensional space. According to the shape characteristics of the guide fin, longitudinal curves are added in three-dimensional space to connect each cross-sectional line, thereby forming a three-dimensional surface with a crisscrossing grid.
[0040] This method extracts key parameters for depicting the cross-sections and similarly designed cross-sections based on the main shape characteristics of the guide section, duct section, and rudder platform section of the guide fin. It proposes a unified method for drawing various cross-sections based on these parameters, thus completing the two-dimensional representation of the guide fin in three-dimensional views. Simultaneously, it extracts or calculates the three-dimensional coordinates of each control point based on the two-dimensional cross-sections of the guide fin, and represents a series of cross-sections in three-dimensional space based on these coordinates. Finally, based on the shape characteristics of the guide fin, longitudinal curves are added in three-dimensional space to connect the various cross-sections, ultimately forming a crisscrossing grid, thereby creating the three-dimensional surface of the guide fin. This method divides the complex shape of the guide fin into three parts: the guide section, the duct section, and the rudder platform section. Each part can be used independently to accommodate the design needs of various stern appendages on different ships. This method incorporates standardized and parameterized shapes of appendages, including bosses and channels, and can be applied to various similar ship appendage shapes through parameter adjustments. It is also applicable to various stern configurations, including but not limited to twin-stern, twin-stern-fin, and single-stern stern configurations for ships with ducted straight-shaft propellers. Furthermore, this method proposes a standardized linear description method for each segment of the guide fin, enabling rapid and concise definition of the cross-sectional shape of the guide fin under different shape characteristics. This facilitates the generation of shape lines in 2D drawings using programming and other methods, and allows for rapid 3D modeling of the guide fin shape, significantly improving the efficiency of design and modeling, and simplifying the modification of drawings and models. Attached Figure Description
[0041] Figure 1 This is a side view of the guide fin provided in an embodiment of the present invention;
[0042] Figure 2 This is a top view of the guide fin provided in an embodiment of the present invention;
[0043] Figure 3 This is a stern view of the guide fin provided in an embodiment of the present invention;
[0044] Figure 4 This is a side view drawing of the center line and outline of the outer steel pipe and the center line and outline of the inner steel pipe provided in the embodiment of the present invention.
[0045] Figure 5 This is a top view drawing of the center line and outline of the outer steel pipe and the center line and outline of the inner steel pipe provided in the embodiments of the present invention.
[0046] Figure 6 This is the drawing of the center line and outline of the outer steel pipe and the center line and outline of the inner steel pipe in the stern view provided in the embodiment of the present invention;
[0047] Figure 7This is a drawing of the guide channel lead wire provided in the embodiment of the present invention;
[0048] Figure 8 This refers to the drawing of the outer oblique tangent line and the inner oblique tangent line of the guide section provided in the embodiments of the present invention;
[0049] Figure 9 This is the design of the arc segment of the channel provided in the embodiment of the present invention;
[0050] Figure 10 This is a side view drawing of the top intersection line of the guide section provided in an embodiment of the present invention;
[0051] Figure 11 This is a top view drawing of the guide section top intersection line provided in the embodiment of the present invention;
[0052] Figure 12 This is the drawing of the top intersection line of the guide section in the stern view provided in the embodiment of the present invention;
[0053] Figure 13 This is a side view drawing of the apex intersection line of the catheter segment provided in an embodiment of the present invention;
[0054] Figure 14 This is a top view drawing of the apex intersection line of the catheter segment provided in an embodiment of the present invention;
[0055] Figure 15 This is the drawing of the apex intersection line of the catheter segment in the stern view provided in the embodiment of the present invention;
[0056] Figure 16 This is the drawing of the oblique tangent line on the outer side and the oblique tangent line on the inner side of the catheter segment in the stern view provided in the embodiment of the present invention;
[0057] Figure 17 This is a side view drawing of the center line and outline of the stern steel pipe provided in the embodiment of the present invention;
[0058] Figure 18 This is a top view drawing of the center line and outline of the stern steel pipe provided in the embodiment of the present invention;
[0059] Figure 19 This is the drawing of the center line and outline of the stern steel pipe provided in the embodiment of the present invention in the stern view;
[0060] Figure 20 This is a side view drawing of the top intersection line of the rudder platform segment provided in an embodiment of the present invention;
[0061] Figure 21 This is a top view drawing of the rudder platform segment top intersection line provided in the embodiment of the present invention;
[0062] Figure 22This is the drawing of the top intersection line of the rudder platform section in the stern view provided in the embodiment of the present invention;
[0063] Figure 23 This is the drawing of the outer oblique tangent line and the inner oblique tangent line of the rudder platform section in the stern view provided in the embodiment of the present invention;
[0064] Figure 24 This is the drawing of the outer oblique tangent line and the inner oblique tangent line of the rudder platform segment in the side view provided in the embodiment of the present invention;
[0065] Figure 25 This is the top view drawing of the outer oblique tangent line and the inner oblique tangent line of the rudder platform segment provided in the embodiment of the present invention;
[0066] Figure 26 This is a schematic diagram of the coordinates of the control points of the cross section of the guide section provided in an embodiment of the present invention;
[0067] Figure 27 This is another schematic diagram of the coordinates of the control points of the cross section of the guide section provided in this embodiment of the invention;
[0068] Figure 28 This is a schematic diagram of the coordinates of the control points of the transverse section of the catheter segment provided in an embodiment of the present invention;
[0069] Figure 29 This is a schematic diagram of the coordinates of the control points of the cross section of the rudder platform provided in an embodiment of the present invention;
[0070] Figure 30 This is another schematic diagram of the coordinates of the control points of the cross section of the rudder platform provided in this embodiment of the invention;
[0071] Figure 31 This is a schematic diagram of the cross sections of the guide fins provided in the embodiments of the present invention in three-dimensional space;
[0072] Figure 32 This is a schematic diagram in three-dimensional space of the cross sections and longitudinal curves of the guide fins provided in the embodiments of the present invention;
[0073] Figure 33 This is a three-dimensional surface view of the guide fin provided in the embodiment of the present invention;
[0074] Figure 34 This is a flowchart illustrating the method for designing and modeling the shape of the stern guide fin of a ship provided in an embodiment of the present invention.
[0075] Figure Labels
[0076] 1. Guide fin; 2. Main hull; 3. Rudder; 4. Duct; 11. Guide section; 12. Duct section; 13. Rudder platform section;
[0077] 111. Outer steel pipe; 1111. Rear center of the outer steel pipe; 1112. Front center of the outer steel pipe;
[0078] 112. Inner steel pipe; 1121. Rear center of the inner steel pipe; 1122. Front center of the inner steel pipe;
[0079] 113. Outer oblique tangent of the guide section; 1131. Top point of the outer oblique tangent of the guide section; 1132. Top intersection point of the outer guide section;
[0080] 114. Inner oblique tangent of the guide section; 1141. Top point of the inner oblique tangent of the guide section; 1142. Top intersection point of the inner guide section;
[0081] 115. Circular arc segment of the channel; 1151. Outer intersection point of the circular arc segment of the channel; 1152. Inner intersection point of the circular arc segment of the channel; 1153. Channel guide line of the guide section; 1154. Center of the circular arc segment of the channel; 1155. Perpendicular bisector;
[0082] 116. Top intersection line of the guide section;
[0083] 121. Top intersection line of catheter segment; 122. Oblique tangent line on the outer side of catheter segment; 123. Oblique tangent line on the inner side of catheter segment;
[0084] 131. Stern steel pipe; 1311. Top of stern steel pipe; 1312. Bottom of stern steel pipe; 132. Top intersection line of rudder platform section; 133. Outer oblique tangent line of rudder platform section; 134. Inner oblique tangent line of rudder platform section; 135. Outline of rudder platform section; 136. Bottom horizontal platform. Detailed Implementation
[0085] To make the technical problems solved by the present invention, the technical solutions adopted, and the technical effects achieved clearer, the technical solutions of the present invention will be further described below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention. Furthermore, it should be noted that, for ease of description, only the parts related to the present invention are shown in the accompanying drawings, not all of them.
[0086] In the description of this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.
[0087] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.
[0088] In the description of this embodiment, the terms "upper," "lower," "left," and "right," etc., refer to the orientation or positional relationship shown in the accompanying drawings. They are used only for ease of description and simplification of operation, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention. In addition, the terms "first" and "second" are used only for distinction in description and have no special meaning.
[0089] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.
[0090] like Figures 1 to 3 As shown, the front and rear sections of the guide fin 1 have different shapes. The guide fin 1 is divided into three sections—front, middle, and rear—by two thick dashed lines, representing the front and rear ends of the duct 4. These are the guide section 11, the duct section 12, and the rudder platform section 13, respectively. The guide section 11 is located in front of the duct 4. The duct section 12 is located above the duct 4, connecting the duct 4 to the main hull 2. The rudder platform section 13 is located behind the duct 4 and above the rudder 3, connecting the rudder 3 to the main hull 2. Specifically, the inner and outer sides of the guide section 11 are each supported by a steel pipe. The front end of the steel pipe is inserted into the main hull 2, and the rear end of the steel pipe is inserted into the front end of the duct 4 of the duct propeller. The tail of the rudder platform section 13 is also supported by a steel pipe. The upper end of the steel pipe is inserted into the main hull 2, and the lower end is flush with the bottom horizontal platform 136 of the rudder platform section 13 of the guide fin 1. The bottom horizontal platform 136 of the rudder platform section 13 of the guide fin 1 is a horizontal, streamlined platform, and its lower end is connected to the rudder 3.
[0091] Based on the above-described design of the guide fin 1, this embodiment provides a method for drawing and modeling the shape of a ship's stern guide fin, including the following steps:
[0092] The stern lines are represented in the three-view diagram. Then, the stern rib lines are imported into the stern view, the stern outline is imported into the side and top views, and the outlines of rudder 3 and duct 4 are imported into the three-view diagram. That is... Figure 34As shown, the pre-design preparation includes importing the stern profile and stern rib profile, and importing the profiles of rudder 3 and duct 4.
[0093] Obtain the cross-sectional features of the guide section 11, the duct section 12, and the rudder platform section 13, and draw each cross-sectional line in two dimensions on the three-dimensional view.
[0094] The cross-section of the guide section 11 includes the centerline and outline of the inner steel pipe 112, the centerline and outline of the outer steel pipe 111, the outer oblique tangent line 113 of the guide section, the inner oblique tangent line 114 of the guide section, the arc section of the channel 115, and the top intersection line 116 of the guide section; that is... Figure 34 As shown, the guide section 11 includes the inner and outer steel pipes of the guide section 11, the inner and outer oblique tangents of the guide section 11, the channel arc segment 115 of the guide section 11, and the top intersection line 116 of the guide section. The inner and outer steel pipes of the guide section 11 are collectively referred to as the center line and outline of the inner steel pipe 112 and the center line and outline of the outer steel pipe 111. The inner and outer oblique tangents of the guide section 11 are collectively referred to as the inner oblique tangent line 114 and the outer oblique tangent line 113 of the guide section.
[0095] The cross-section of catheter segment 12 includes the apical intersection line 121, the lateral oblique tangent line 122, and the medial oblique tangent line 123; that is... Figure 34 As shown, the duct segment 12 includes the top intersection line 121 and the inner and outer oblique tangent lines of the duct segment 12. The inner and outer oblique tangent lines of the duct segment 12 are collectively referred to as the inner oblique tangent line 123 and the outer oblique tangent line 122.
[0096] The cross-section of the rudder platform section 13 includes the centerline and outline of the stern steel pipe 131, the top intersection line 132 of the rudder platform section, the outer oblique tangent line 133 of the rudder platform section, the inner oblique tangent line 134 of the rudder platform section, and the outline line 135 of the rudder platform section; that is... Figure 34 As shown, the rudder platform section 13 includes the stern steel pipe 131, the top intersection line 132, the inner and outer oblique tangent lines of the rudder platform section 13, and the outline line 135. The inner and outer oblique tangent lines of the rudder platform section 13 are collectively referred to as the inner oblique tangent line 134 and the outer oblique tangent line 133.
[0097] Based on the coordinates of the control points of each cross section, the cross sections are drawn in three-dimensional space. According to the shape characteristics of guide fin 1, longitudinal curves are added in three-dimensional space to connect the cross sections, thus forming a three-dimensional surface with an interlaced grid. Figure 34 As shown, establishing a three-dimensional model includes obtaining the coordinates of the cross section control points of the guide fin 1, establishing each cross section of the guide fin 1 in three-dimensional space, adding longitudinal curves, and forming the three-dimensional surface of the guide fin 1.
[0098] The method provided in this embodiment extracts the main shape features of the cross-sections of the guide section 11, guide section 12, and rudder platform section 13 of the guide fin 1, extracts the main parameters for depicting the cross-sections and similarly designed cross-sections, and proposes a unified method for drawing various cross-sections based on these main parameters. This completes the two-dimensional representation of the guide fin 1 in three-dimensional views. Simultaneously, it extracts or calculates the three-dimensional coordinates of each control point based on the two-dimensional cross-sections of the guide fin 1, and represents a series of cross-sections in three-dimensional space based on the three-dimensional coordinates. Finally, based on the shape features of the guide fin 1, longitudinal curves are added in three-dimensional space to connect the various cross-sections, ultimately forming a crisscrossing grid, thus forming the three-dimensional surface of the guide fin 1. This method divides the complex shape of the guide fin 1 into three parts: the guide section 11, the guide section 12, and the rudder platform section 13. Each part can be used independently to meet the needs of various stern appendage designs on different ships. This method incorporates the shapes of appendages with similar functions, such as bosses and channels, and is standardized and parameterized. By adjusting the design parameters, it can be applied to various similar ship appendage shapes and various stern forms, including but not limited to straight-shaft propeller-driven ships with ducts 4, such as twin-stern, twin-stern-fin, and single-stern stern forms. Furthermore, this method proposes a standardized linear description method for each segment of the guide fin 1, which can quickly and concisely define the cross-sectional shape of the guide fin 1 under different shape characteristics. This facilitates the generation of shape lines in two-dimensional drawings through programming and other means, and also facilitates rapid three-dimensional modeling of the shape of the guide fin 1, greatly improving the efficiency of design and modeling, and simplifying the modification of drawings and models.
[0099] Optionally, such as Figures 1 to 3 As shown, an inner steel pipe 112 is provided on the inner side of the guide section 11, and an outer steel pipe 111 is provided on the outer side of the guide section 11. The front ends of the inner steel pipe 112 and the outer steel pipe 111 are inserted into the main hull 2, and the rear ends of the inner steel pipe 112 and the outer steel pipe 111 are inserted into the front end of the duct 4 of the propeller.
[0100] Reference Figures 4 to 6The drawing of the centerline and outline of the inner steel pipe 112 and the centerline and outline of the outer steel pipe 111 includes the following steps: Determine the diameter d1 of the inner steel pipe 112 and the diameter d2 of the outer steel pipe 111 according to the dimensions of the conduit 4, where d1 and d2 are both smaller than the thickness of the front end of the conduit 4; The X-coordinates of the rear end center 1121 of the inner steel pipe and the rear end center 1111 of the outer steel pipe are consistent with the position of the front end of the conduit 4; The Y-coordinates and Z-coordinates of the rear end center 1121 of the inner steel pipe and the rear end center 1111 of the outer steel pipe should be ensured; The circular cross-sections of the inner steel pipe 112 and the outer steel pipe 111 are within the thickness range of the front end of the conduit 4; The positions of the front end center 1122 of the inner steel pipe and the front end center 1112 of the outer steel pipe should be ensured. The front ends of the inner steel pipe 112 and the outer steel pipe 111 are completely submerged within the main hull 2, and the X coordinates of the center of the front end of the inner steel pipe 1122 and the center of the front end of the outer steel pipe 1112 are the same, with the one closer to the bow being used as the reference. Based on the coordinate positions of the center of the front end of the inner steel pipe 1122, the center of the rear end of the inner steel pipe 1121, the center of the front end of the outer steel pipe 1112, the center of the rear end of the outer steel pipe 1111, and the diameters of the outer steel pipe 111 and the inner steel pipe 112, the center line and outline of the inner steel pipe 112, the center line and outline of the outer steel pipe 111, and the cross section lines at each rib are drawn in the three-way view. Among them, the cross section lines of the inclined inner steel pipe 112 and the outer steel pipe 111 are simplified to perfect circles.
[0101] Reference Figures 7 to 9 The drawing of the inner oblique tangent line 114 and the outer oblique tangent line 113 of the guide section includes the following steps: On both sides of the guide section 11, straight steel plates are set to connect the inner steel pipe 112 and the outer steel pipe 111 to the main hull 2, so as to form the outer oblique tangent line 113 and the inner oblique tangent line 114 of the guide section on each cross section line of the stern view.
[0102] Among them, the outer oblique tangent 113 of the guide section is a straight line segment, which forms a first angle α with the vertical direction. The bottom end of the outer oblique tangent 113 of the guide section is tangent to the outer steel pipe 111, and the top end of the outer oblique tangent 113 of the guide section extends to the first height H. That is, the top point 1131 of the outer oblique tangent of the guide section intersects the main hull 2 at the top intersection point 1132 of the outer oblique tangent of the guide section.
[0103] The inner oblique tangent 114 of the guide section is a straight line segment, forming a second angle β with the vertical direction. The bottom end of the inner oblique tangent 114 of the guide section is tangent to the inner steel pipe 112, and the top end of the inner oblique tangent 114 of the guide section extends to the first height H. That is, the top point 1141 of the inner oblique tangent of the guide section intersects with the main hull 2 at the top intersection point 1142 of the inner side of the guide section.
[0104] The first height H is greater than the lowest point of the ship's stern plate, and the first included angle α and the second included angle β may be the same or different.
[0105] Reference Figure 7 and Figure 8 The design of the channel arc segment 115 of the guide section 11 includes the following steps: Based on the stern hull shape and the direction of the water flow, a guide section channel leader line 1153 is set. A perpendicular bisector 1155 is drawn from the line connecting the centers of the inner steel pipe 112 and the outer steel pipe 111. The perpendicular bisector 1155 intersects the guide section channel leader line 1153 at a single point, which is the center 1154 of the channel arc segment. Using the center 1154 as the center, an arc segment tangent to the inner steel pipe 112 and the outer steel pipe 111 is drawn; this is the channel arc segment 115. In each cross section of the guide section 11, the channel arc segment 115 is an arc segment, with both ends tangent to the inner steel pipe 112 and the outer steel pipe 111, respectively. Therefore, a guide section channel leader line 1153 is designed to control the direction of the guide section 11 channel. The guide channel lead line 1153 is the direction line that gathers the water flow in front of the propeller to the center of the propeller. It is based on the guide channel lead line 1153 that the center line or axis of the arc segment 115 of the channel can be further determined. For example, Figure 7 For a stern profile with double tail fins, a center line of the tail fin naturally appears, and the water flow will flow backward along both sides of the tail fin. The center line of the tail fin can then be used as the guide line 1153 of the flow channel.
[0106] Reference Figure 9 At some of the ribs, the arc segment 115 of the channel intersects with the main hull 2 to form an intersection point, namely the outer intersection point 1151 of the arc segment of the channel and the inner intersection point 1152 of the arc segment of the channel.
[0107] Reference Figures 10 to 12 The drawing of the top intersection line 116 of the guide section includes the following steps: Based on the coordinate positions of the inner top intersection point 1142, outer top intersection point 1132, inner intersection point 1152, and outer intersection point 1151 of the channel arc section on each cross section line in the stern view, these coordinates are mapped to the side view and top view respectively, and then smoothly connected sequentially to form the top intersection line 116 of the guide section, which is the intersection line between the guide section 11 and the main hull 2. In this embodiment, the top intersection line 116 of the guide section is... Figures 10 to 12 The thick solid line in the middle.
[0108] In specific implementation, the outer intersection point 1151 of the channel arc section is obtained based on the center and outline of the main hull 2, the outer steel pipe 111, the center and outline of the inner steel pipe 112, and the channel guide line 1153 set thereon; the inner intersection point 1152 of the channel arc section is obtained based on the center and outline of the main hull 2, the outer steel pipe 111, the inner steel pipe 112, and the channel guide line 1153 set thereon; the outer top intersection point 1132 of the channel guide section is obtained based on the center line and outline of the main hull 2, the outer steel pipe 111, and the straight steel plates set on both sides of the channel guide section 11; the inner top intersection point 1142 of the channel guide section is obtained based on the center line and outline of the main hull 2, the inner steel pipe 112, and the straight steel plates set on both sides of the channel guide section 11.
[0109] Reference Figures 13 to 15 The drawing of the catheter segment top intersection line 121 includes the following steps: selecting the guide segment top intersection line 116 in any view and smoothly extending it to the rear end of the catheter 4, connecting and tangent to the guide segment top intersection line 116, thus forming the catheter segment top intersection line 121, and corresponding it to the other two views. In this embodiment, the catheter segment top intersection line 121 is... Figures 13 to 15 The thick solid line in the middle.
[0110] Reference Figure 16 The drawing of the inner oblique tangent 123 and the outer oblique tangent 122 of the duct segment includes the following steps: In the cross section of each rib in the stern view, through the point on each cross section of the top intersection line 121 of the duct segment, draw the outer oblique tangent 122 and the inner oblique tangent 123 of the duct segment, which form a first preset angle with the vertical direction. The bottom end of the outer oblique tangent 122 and the bottom end of the inner oblique tangent 123 of the duct segment are submerged in the duct 4, and the top end of the outer oblique tangent 122 and the top end of the inner oblique tangent 123 of the duct segment extend to a first height H.
[0111] Reference Figures 17 to 19 The drawing of the centerline and outline of the stern steel pipe 131 includes the following steps: Determine the diameter and position of the stern steel pipe 131 according to the ship's characteristics. The stern steel pipe 131 is placed at or in front of the stern endplate. Based on the inclination angles of the inner oblique tangent line 114 of the guide section, the outer oblique tangent line 113 of the guide section, the inner oblique tangent line 123 of the guide section, and the outer oblique tangent line 122 of the guide section, the stern steel pipe 131 is designed to be placed at an angle. Based on the position and size of the rudder 3, determine the height H_rp of the rudder platform section 13, i.e., the height of the bottom end 1312 of the stern steel pipe. Determine the diameter of the stern steel pipe 131, the coordinates of the top end 1311 of the stern steel pipe, and the coordinates of the bottom end 1312 of the stern steel pipe. Draw the centerline and outline of the stern steel pipe 131 in the three-way view. In this embodiment, the centerline and outline of the stern steel pipe 131 are... Figures 17 to 19 The thick solid line in the middle.
[0112] The height H_rp of the rudder platform section 13 should be as small as possible, i.e., as close as possible to the upper edge of the rudder 3, while ensuring that the guide fin 1 and the rudder 3 do not physically interfere with each other and that the installation is feasible. Generally, the height H_rp of the rudder platform section 13 should not exceed 1.15 times the height of the upper edge of the rudder 3.
[0113] Reference Figures 20 to 22 The drawing of the top intersection line 132 of the rudder platform section includes the following steps: Selecting the top intersection line 121 of the guide tube section in any view, extending it smoothly backward to the stern steel pipe 131, connecting and tangent to the top end 1311 of the stern steel pipe, thus forming the top intersection line 132 of the rudder platform section, and mapping the top intersection line 132 of the rudder platform section to the other two views. In this embodiment, the top intersection line 132 of the rudder platform section is... Figures 20 to 22 The thick solid line in the middle.
[0114] Reference Figure 23 The drawing of the outer oblique tangent line 133 and the inner oblique tangent line 134 of the rudder platform section includes the following steps: In the cross section lines of each rib in the stern view, through the point on each cross section line of the top intersection line 132 of the rudder platform section, draw the outer oblique tangent line 133 and the inner oblique tangent line 134 of the rudder platform section, which form a second preset angle with the vertical direction. The bottom end of the outer oblique tangent line 133 and the bottom end of the inner oblique tangent line 134 of the rudder platform section extend to the height H_rp of the rudder platform section 13, and the top end of the outer oblique tangent line 133 and the top end of the inner oblique tangent line 134 of the rudder platform section extend to the first height H. The bottom end of the inner oblique tangent line 134 and the bottom end of the outer oblique tangent line 133 of the rudder platform section are connected smoothly in sequence to obtain the projection of the rudder platform section outline line 135 in the stern view; the rudder platform section outline line 135 is the outline of the bottom horizontal platform 136.
[0115] Reference Figure 24 and Figure 25 Based on each rib, the bottom coordinates of the outer oblique tangent line 133 of the rudder platform section and the bottom coordinates of the inner oblique tangent line 134 of the rudder platform section are drawn and smoothly connected in the side view and top view.
[0116] Based on the shape characteristics of each cross section of the guide section 11, guide section 12, and rudder platform section 13, the coordinates of the control points of each cross section are read from the completed two-dimensional drawings.
[0117] Among them, reference Figure 26 and Figure 27The process of reading the control point coordinates of each cross section of the guide section 11 includes the following steps: For the guide section 11, its cross section shape can be represented by two straight line segments and three circular arc segments, and this method is universal. Tangents are drawn between adjacent line segments and extended, so that its shape can be uniquely determined using only five coordinates (points A, B, C, D, E) and three radii (R1, R2, R3). The cross section shape of the guide section 11 is similar to a "W" shape. The lower sides are the inner and outer steel pipe cross section circles of the guide section 11, the middle groove is a circular arc segment tangent to the two cross section circles, and the two sides are straight line segments at a certain angle, also tangent to the two cross section circles. This cross section shape is uniquely defined by five coordinates and three radii.
[0118] Reference Figure 28 The steps to read the control point coordinates of each cross section of the catheter segment 12 are as follows: For the catheter segment 12, its cross section shape can be represented by two straight line segments and one circular arc segment, and it has universality. Its shape can be uniquely determined by only five coordinates (points F, G, J, K, O) and one radius (R4).
[0119] Reference Figure 29 and Figure 30 The process of reading the control point coordinates of each cross section of the rudder platform segment 13 includes the following steps: For the rudder platform segment 13, its cross section shape can be represented by 3 straight line segments and has universality. Its shape can be uniquely determined by only 4 point coordinates (points P, Q, S, T).
[0120] Reference Figure 31 The steps to establish the cross sections of the guide fin 1 in three-dimensional space include: establishing each cross section in three-dimensional space according to the coordinate position of the read control point.
[0121] Reference Figure 32 Add multiple vertically oriented curves that intersect with each cross section line.
[0122] Reference Figure 33 This forms the three-dimensional surface of the guide fin 1. In the three-dimensional modeling, the guide fin 1 is not limited to the part that actually protrudes outside the main hull 2, but extends the two sides upward to a first height H. The first height H is not lower than the height of the lowest point of the stern plate. A part of the surface of the guide fin 1 obtained by the three-dimensional modeling extends into the interior of the main hull 2.
[0123] The above embodiments merely illustrate the basic principles and characteristics of the present invention. The present invention is not limited to the above embodiments. Various changes and modifications can be made to the present invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.
Claims
1. A method for designing and modeling the shape of a stern guide fin of a ship, wherein the guide fin (1) comprises a guide section (11), a duct section (12), and a rudder platform section (13) connected in sequence, the duct section (12) connecting the duct (4) and the main hull (2), and the rudder platform section (13) connecting the rudder (3) and the main hull (2), characterized in that, Includes the following steps: The stern profile of the ship is expressed in the three-way view. The stern rib profile is then imported into the stern view of the three-way view. The stern outline is imported into the side view and top view of the three-way view. The outlines of the rudder (3) and the guide tube (4) are imported into the three-way view. Obtain the cross-sectional features of the guide section (11), the guide pipe section (12), and the rudder platform section (13), and draw each cross-section in two dimensions on the three-dimensional view; the cross-section of the guide section (11) includes the center line and outline of the inner steel pipe (112), the center line and outline of the outer steel pipe (111), the outer oblique line (113) of the guide section, the inner oblique line (114) of the guide section, the arc section (115) of the channel, and the guide section. Top intersection line (116); the cross section of the guide tube section (12) includes the top intersection line (121), the outer oblique tangent line (122), and the inner oblique tangent line (123); the cross section of the rudder platform section (13) includes the center line and outline of the stern steel pipe (131), the top intersection line (132), the outer oblique tangent line (133), the inner oblique tangent line (134), and the outline line (135) of the rudder platform section; Based on the coordinates of the control points of each cross section, draw each cross section in three-dimensional space; Based on the shape characteristics of the guide fin (1), longitudinal curves are added in three-dimensional space to connect the various cross sections, thereby forming a three-dimensional surface with a grid of intersecting lines.
2. The method of fairing and modeling a ship's stern flow fin according to claim 1, characterized in that, The inner steel pipe (112) is provided on the inner side of the guide section (11), and the outer steel pipe (111) is provided on the outer side of the guide section (11). The front ends of the inner steel pipe (112) and the outer steel pipe (111) are inserted into the main hull (2), and the rear ends of the inner steel pipe (112) and the outer steel pipe (111) are inserted into the front end of the guide pipe (4). The diameter d1 of the inner steel pipe (112) and the diameter d2 of the outer steel pipe (111) are determined according to the size of the conduit (4). Both d1 and d2 are smaller than the thickness of the front end of the conduit (4). The X coordinates of the rear end center (1121) of the inner steel pipe and the rear end center (1111) of the outer steel pipe are consistent with the front end position of the conduit (4). The Y and Z coordinates of the rear end center (1121) of the inner steel pipe and the rear end center (1111) of the outer steel pipe should be guaranteed. The circular cross sections of the inner steel pipe (112) and the outer steel pipe (111) are within the thickness range of the front end of the conduit (4). The positions of the center of the front end of the inner steel pipe (1122) and the center of the front end of the outer steel pipe (1112) should be such that the front ends of the inner steel pipe (112) and the outer steel pipe (111) are completely submerged within the main hull (2), and the X coordinates of the center of the front end of the inner steel pipe (1122) and the center of the front end of the outer steel pipe (1112) are the same, with the one closer to the bow being the standard; Based on the coordinate positions of the center of the front end (1122), the center of the rear end (1121), the center of the front end (1112), and the center of the rear end (1111) of the outer steel pipe, as well as the diameters of the outer steel pipe (111) and the inner steel pipe (112), draw the center line and outline of the inner steel pipe (112), the center line and outline of the outer steel pipe (111), and the cross section lines at each rib position in the three-way view. The cross-sections of the inclined inner steel pipe (112) and the outer steel pipe (111) are simplified to perfect circles.
3. The method of fairing and modeling a ship's stern flow fin according to claim 1, wherein, On both sides of the guide section (11), straight steel plates are provided to connect the inner steel pipe (112), the outer steel pipe (111) and the main hull (2) together, so as to form the outer oblique line (113) and the inner oblique line (114) of the guide section on each cross section line of the stern view. The outer oblique tangent (113) of the guide section is a straight line segment, forming a first angle α with the vertical direction. The bottom end of the outer oblique tangent (113) of the guide section is tangent to the outer steel pipe (111). The top end of the outer oblique tangent (113) of the guide section extends to a first height H, that is, the top point (1131) of the outer oblique tangent of the guide section intersects with the main hull (2) at the top intersection point (1132) of the guide section. The inner oblique tangent (114) of the guide section is a straight line segment, forming a second angle β with the vertical direction. The bottom end of the inner oblique tangent (114) of the guide section is tangent to the inner steel pipe (112). The top end of the inner oblique tangent (114) of the guide section extends to the first height H, that is, the top point (1141) of the inner oblique tangent of the guide section intersects with the main hull (2) at the top intersection point (1142) of the guide section. The first height H is greater than the lowest point of the ship's stern plate, and the first included angle α and the second included angle β may be the same or different.
4. The method of fairing and modeling a ship's stern flow fin according to claim 1, wherein, According to the stern hull shape and the direction of water flow, set the guide channel lead line (1153), draw the perpendicular bisector (1155) of the line connecting the centers of the inner steel pipe (112) and the outer steel pipe (111), the perpendicular bisector (1155) intersects the guide channel lead line (1153) at a point which is the center of the channel arc segment (1154), and draw an arc segment tangent to the inner steel pipe (112) and the outer steel pipe (111) with the center of the channel arc segment (1154) as the center, which is the channel arc segment (115). At some rib locations, the arc segment (115) of the channel intersects with the main hull (2) to form an intersection point, namely the outer intersection point (1151) of the arc segment of the channel and the inner intersection point (1152) of the arc segment of the channel.
5. The method of fairing and modeling a ship's stern flow fin according to claim 1, wherein, Based on the coordinates of the inner top intersection point (1142), outer top intersection point (1132), inner intersection point (1152), and outer intersection point (1151) of the channel arc section on each cross section line in the stern view, respectively, they are mapped to the side view and top view, and then smoothly connected in sequence to form the top intersection line (116) of the guide section, which is the intersection line between the guide section (11) and the main hull (2); The outer intersection point (1151) of the channel arc segment is obtained based on the center and outline of the main hull (2), the outer steel pipe (111), the center and outline of the inner steel pipe (112), and the channel guide line (1153) of the flow guide section. The inner intersection point (1152) of the channel arc segment is obtained based on the center and outline of the main hull (2), the outer steel pipe (111), the center and outline of the inner steel pipe (112), and the channel guide line (1153) of the flow guide section. The outer top intersection point (1132) of the guide section is obtained based on the center line and outline of the main hull (2), the outer steel pipe (111), and the straight steel plates set on both sides of the guide section (11); The inner top intersection point (1142) of the guide section is obtained based on the center line and outline of the main hull (2), the inner steel pipe (112), and the straight steel plates set on both sides of the guide section (11).
6. The method of designing and modeling the external shape of a ship's stern flow guide fin according to any one of claims 1 or 5, characterized in that, Select any view and extend the top intersection line (116) of the guide segment smoothly backward to the rear end of the catheter (4), connect with and be tangent to the top intersection line (116) of the guide segment to form the top intersection line (121) of the catheter segment, and correspond to the other two views.
7. The method of fairing and modeling a ship's stern flow directing fin according to claim 6, wherein, In the cross-section of each rib in the stern view, through the point on each cross-section of the top intersection line (121) of the catheter segment, draw the oblique line (122) on the outer side of the catheter segment and the oblique line (123) on the inner side of the catheter segment. They form a first preset angle with the vertical direction. The bottom end of the oblique line (122) on the outer side of the catheter segment and the bottom end of the oblique line (123) on the inner side of the catheter segment are submerged in the catheter (4). The top end of the oblique line (122) on the outer side of the catheter segment and the top end of the oblique line (123) on the inner side of the catheter segment extend to a first height H.
8. The method of fairing and modeling a ship's stern flow directing fin according to claim 7, wherein, The diameter and position of the stern steel pipe (131) are determined according to the characteristics of the ship type. The stern steel pipe (131) is placed at or in front of the stern end plate of the ship. According to the inclination angle of the inner oblique tangent line (114) of the guide section, the outer oblique tangent line (113) of the guide section, the inner oblique tangent line (123) of the guide section and the outer oblique tangent line (122) of the guide section, the stern steel pipe (131) is designed to be placed at an inclination. Based on the position and size of the rudder (3), determine the height H_rp of the rudder platform section (13), i.e. the height of the bottom end (1312) of the stern steel pipe, determine the diameter of the stern steel pipe (131), the coordinates of the top end (1311) of the stern steel pipe, and the coordinates of the bottom end (1312) of the stern steel pipe, and draw the center line and outline of the stern steel pipe (131) in the three-way view.
9. The method of fairing and modeling a ship's stern flow fin according to claim 6, wherein, Select any view and extend the top intersection line (121) of the duct segment smoothly backward to the stern steel pipe (131), connecting and tangent to the top end (1311) of the stern steel pipe, thus forming the top intersection line (132) of the rudder platform segment, which corresponds to the other two views.
10. The method of fairing and modeling a ship's stern flow directing fin according to claim 9, wherein, In the cross section of each rib in the stern view, through the point on each cross section of the top intersection line (132) of the rudder platform segment, draw the outer oblique line (133) and the inner oblique line (134) of the rudder platform segment, which form a second preset angle with the vertical direction. The bottom end of the outer oblique line (133) and the bottom end of the inner oblique line (134) of the rudder platform segment extend to the height H_rp of the rudder platform segment (13). The top end of the outer oblique line (133) and the top end of the inner oblique line (134) of the rudder platform segment extend to the first height H. By sequentially and smoothly connecting the bottom end of the inner oblique tangent line (134) of the rudder platform segment and the bottom end of the outer oblique tangent line (133) of the rudder platform segment, the projection of the outline line (135) of the rudder platform segment in the stern view is obtained. According to each rib, the bottom coordinates of the outer oblique line (133) of the rudder platform section and the bottom coordinates of the inner oblique line (134) of the rudder platform section are drawn and smoothly connected in the side view and top view.