Outer plate fairing method for asymmetric tail shaft

Abstract

The invention discloses an outer plate fairing method for an asymmetric tail shaft. The method comprises the steps that the diameter of the tail end face of an outlet of the asymmetric tail shaft in a molded line graph and a theoretical line of a tail column steel casting are determined; a middle longitudinal section line in the molded line graph is deviated outwards by the thickness of the outer plate, the molded line within the range of the steel casting is smoothened, and a new middle longitudinal section line is generated; the method comprises the following steps of: firstly, making a vertical line of a middle longitudinal theoretical line at one point in a ship body, cutting out a section of the oblique section line, connecting a curve by using a spline curve, outwards shifting the curve by the thickness of an outer plate to obtain a curve as an outer skin line, making a vertical line of the oblique section line by using an intersection point of the outer skin line and the longitudinal section line, the point is the outer skin point of the oblique section line, and the rest can be done in the same way, a plurality of oblique section lines are made, the outer skin points are obtained, the outer skin points are connected through a spline curve, and the curve is the outer skin line; a guarantee is provided for on-site assembly of the tail casting and the outer plate.

Description

Technical Field

[0001] The invention belongs to the technical field of shipbuilding, and in particular relates to a method for smoothing an outer plate of an asymmetric tail shaft. Background Art

[0002] In the design of some tail castings, after receiving the drawings from the detailed design company, they were sent directly to the steel casting manufacturer without lofting or rough lofting after a simple size comparison, resulting in a large size error between the steel casting and the hull outer plate, resulting in uneven joints between the steel casting and the main hull outer plate, making on-site assembly difficult and inefficient. Especially for double-propeller and double-rudder ships, the centerline of the tail shaft is asymmetrical left and right. If the previous design method is used, on-site construction will be more difficult, increasing the on-site adjustment and repair cycle, and the construction cycle will also be relatively extended. Summary of the invention

[0003] In view of the above problems, the purpose of the present invention is to provide a method for smoothing the outer plate of an asymmetric tail shaft, which improves the layout accuracy by obliquely sectioning the longitudinal section line, makes the intersection of the outer plate skin line and the tail shaft casting smooth, reduces the construction difficulty, and improves the on-site assembly cycle.

[0004] The present invention adopts the following technical solutions to realize the present invention: A method for smoothing the outer plate of an asymmetric tail shaft comprises the following steps: S1. According to the tail end face size of the hull rough machining drawing and the oblique section of the asymmetric tail shaft centerline, determine the diameter of the tail end face at the asymmetric tail shaft outlet in the line drawing and the theoretical line of the tail column steel casting; S2. According to the detailed drawing of the hull structure, determine the position of the joint between the steel casting and the hull outer plate, determine the outer plate thickness of the joint with the asymmetric stern steel casting, offset the middle longitudinal section line in the line drawing outward by the outer plate thickness, the outer surface line of the steel casting is inconsistent with the theoretical line of the hull, and there is a linear transition, the line transitions from the theoretical line of the stern steel casting to the outer surface of the hull outer plate; smooth the lines within the range of the steel casting to generate a new middle longitudinal section line; S3. Cut out the longitudinal section line and make it smooth according to the method of oblique sectioning longitudinal section line. First, make a perpendicular line to the mid-longitudinal theoretical line at a point inside the hull, cut out the section of this oblique section line, connect it with a spline curve to form a curve. The curve is offset outward by the thickness of the outer plate. The obtained curve is the outer skin line. The intersection of the outer skin line and the longitudinal section line is made into a perpendicular line of the oblique section line. The point obtained is the outer skin point of this oblique section line. Similarly, make several oblique section lines to obtain the outer skin points. The outer skin points are connected with a spline curve. This curve is the outer skin line. S4. Use the three-item smoothing method to verify whether the modified line drawing is smooth. Use the newly generated longitudinal outer skin line to cut out the outer skin line of the transverse section and the waterline section to see whether the cut section is smooth. If not, modify the uneven curve into a smooth transition curve, and then adjust the other two curves according to the three-item smoothing method until the inner and outer skins are three-item smooth respectively.

[0005] Furthermore, when the line shape within the steel casting is smoothed in step S2 to generate a new mid-longitudinal section line, the line shape adjustment should be completed within the range of the stern casting. If it exceeds the range of the steel casting, it will affect the main hull structure size.

[0006] Furthermore, when the longitudinal sectioning lines are obliquely cut in step S3, the spacing between the oblique sectioning lines is controlled to be 200 mm to 300 mm, and the spacing is adjusted according to the curvature of the line. The denser oblique sectioning lines can be closer to the actual shape of the outer skin thickness of the hull shell, thereby improving the lofting accuracy.

[0007] The beneficial technical effects of the present invention are: The present invention can make the regenerated outer plate curve closer to the actual shape of the hull outer plate thickness by obliquely sectioning the longitudinal section line, thereby providing a strong guarantee for the assembly accuracy of the on-site tail casting and the outer plate. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 A schematic diagram of a transverse cross-sectional line view of an outer plate of an asymmetric tail shaft provided by an embodiment of the present invention; Figure 2 A schematic diagram of the diameter of the tail end face at the outlet of the asymmetric tail shaft and the theoretical line of the tail pillar steel casting and the range of the tail pillar steel casting provided by an embodiment of the present invention; Figure 3 A schematic diagram of a point in the hull with a smooth outer plate of an asymmetric tail shaft provided by an embodiment of the present invention being a perpendicular line to the mid-longitudinal theoretical line; Figure 4 A schematic diagram of the outer plate theoretical line and the outer skin line obtained by fairing the outer plate of the asymmetric tail shaft provided by an embodiment of the present invention; Figure 5 A schematic diagram of the longitudinal outer skin line and longitudinal outer skin point obtained by fairing the outer plate of the asymmetric tail shaft provided by an embodiment of the present invention; Figure 6 A schematic diagram of oblique section lines of several levels near the line shape that needs to be adjusted for the smoothing of the asymmetric tail shaft outer plate provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0009] The invention discloses a method for smoothing the outer plate of an asymmetric tail shaft, comprising the following steps: S1. According to the rough machining drawing of the hull, the tail end surface size and the oblique section of the asymmetric tail shaft centerline (see attached Figure 1 ), determine the diameter of the tail end face at the asymmetric tail shaft outlet in the profile diagram and the theoretical line of the tail column casting (see Appendix Figure 2 ); S2. According to the detailed drawing of the hull structure, determine the position of the joint between the steel casting and the hull outer plate, determine the outer plate thickness at the joint with the asymmetric stern column steel casting, offset the middle longitudinal section line in the line drawing outward by the outer plate thickness (the outer plate thickness of the middle longitudinal section is closest to the actual thickness of the hull), the outer surface line of the steel casting is inconsistent with the theoretical line of the hull, and there is a linear transition, which transitions from the theoretical line of the stern column steel casting to the outer surface of the hull outer plate; smooth the lines within the range of the steel casting to generate a new middle longitudinal section line; S3. Cut out the longitudinal section line according to the method of oblique longitudinal section line and make it smooth. First, make a perpendicular line to the mid-longitudinal theoretical line at a point inside the hull (this is because the vertical oblique section line is closest to the actual thickness of the hull outer plate) (see attached Figure 3 ), cut out the section of this oblique section line, connect it with a spline curve, and deviate the curve outwards by the thickness of the outer plate. The resulting curve is the outer skin line (see Appendix Figure 4 ), use the intersection of the outer skin line and the longitudinal section line as a perpendicular line to the oblique section line, and this point is the outer skin point of the oblique section line (see attached Figure 5 ), and so on, make several oblique sections to obtain the outer skin points, and connect the outer skin points with a spline curve. This curve is the outer skin line; S4. Use the three-item smoothing method to verify whether the modified line drawing is smooth. Use the newly generated longitudinal skin line to cut out the skin lines of the transverse section and the waterline section to see whether the cut section is smooth (the curve is a smooth transition curve without abrupt changes). If it is not smooth, modify the uneven curve (for example, the transverse section line is not smooth) into a smooth transition curve, and then adjust the other two curves (longitudinal section line and waterline) according to the three-item smoothing method (if the skin is adjusted, the theoretical line also needs to be adjusted accordingly) until the inner skin and outer skin are smooth in three aspects respectively.

[0010] Among them, in step S2, when the line within the range of the steel casting is smoothed and a new mid-longitudinal section line is generated, the line adjustment should end within the range of the stern casting. If it exceeds the range of the steel casting, it will affect the main hull structure size (see Appendix Figure 2 ).

[0011] When the longitudinal section line is obliquely cut in step S3, the spacing between the oblique section lines is controlled to be 200 mm to 300 mm, and the spacing is adjusted according to the curvature of the line (see attached Figure 6 ), the denser oblique section lines can be closer to the actual shape of the thickness of the hull outer skin and improve the lofting accuracy.

[0012] So far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

Claims

1. A method for smoothing the outer plate of an asymmetric tail shaft, characterized in that: The steps include: S1. According to the tail end face size of the hull rough machining drawing and the oblique section of the asymmetric tail shaft centerline, determine the diameter of the tail end face at the asymmetric tail shaft outlet in the line drawing and the theoretical line of the tail column steel casting; S2. According to the detailed drawing of the hull structure, determine the position of the joint between the steel casting and the hull outer plate, determine the outer plate thickness of the joint with the asymmetric stern steel casting, offset the middle longitudinal section line in the line drawing outward by the outer plate thickness, the outer surface line of the steel casting is inconsistent with the theoretical line of the hull, and there is a linear transition, the line transitions from the theoretical line of the stern steel casting to the outer surface of the hull outer plate; smooth the lines within the range of the steel casting to generate a new middle longitudinal section line; S3. Cut out the longitudinal section line and make it smooth according to the method of oblique sectioning longitudinal section line. First, make a perpendicular line to the mid-longitudinal theoretical line at a point inside the hull, cut out the section of this oblique section line, connect it with a spline curve to form a curve. The curve is offset outward by the thickness of the outer plate. The obtained curve is the outer skin line. The intersection of the outer skin line and the longitudinal section line is made into a perpendicular line of the oblique section line. The point obtained is the outer skin point of this oblique section line. Similarly, make several oblique section lines to obtain the outer skin points. The outer skin points are connected with a spline curve. This curve is the outer skin line. S4. Use the three-item smoothing method to verify whether the modified line drawing is smooth. Use the newly generated longitudinal outer skin line to cut out the outer skin line of the transverse section and the waterline section to see whether the cut section is smooth. If not, modify the uneven curve into a smooth transition curve, and then adjust the other two curves according to the three-item smoothing method until the inner and outer skins are three-item smooth respectively.

2. The outer plate smoothing method of an asymmetric tail shaft according to claim 1, characterized in that: In step S2, when the line shape within the range of the steel casting is smoothed and a new mid-longitudinal section line is generated, the line shape adjustment should be completed within the range of the stern casting. If it exceeds the range of the steel casting, it will affect the main hull structure size.

3. The outer plate smoothing method of an asymmetric tail shaft according to claim 1, characterized in that: When the longitudinal section line is obliquely cut in step S3, the spacing between the oblique section lines is controlled to be 200 mm to 300 mm.

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