DESC:FIELD OF INVENTION:

[1] The present invention generally relates to warships as well as commercial ships. More particularly, the present invention relates to an improved method for sighting keel and draught marking in a ship.

BACKGROUND OF THE INVENTION:

[2] In warships as well as commercial ships, a keel is provided for the purpose of counterbalancing to prevent sideways overturning of the ship. Generally, the keel is a solid structural part at the very bottom of the ship, running longitudinally along the center bottom of the hull. It is made of metal, wood or any other solid material.

[3] The draught, also spelled as draft, is the vertical distance between the water level and the keel, which is significant in determining the minimum depth of the water in which the ship can navigate. Hence, the hull of the ship is provided with the horizontal lines, called as markings, at each of its sides.

[4] Traditionally, draught marking is conducted one or two month prior to launching of ship. The first step is to carry out keel sighting to identify the lowest point of keel throughout the length of the vessel. This lowest point of keel is considered as global reference zero point for draught marking. The draught marks on the side shell are marked as per Design – Outfit drawing, based on this global reference zero point. The traditional method of draught marking is illustrated in Figure 1.

[5] The traditional approach considers the keel deflection obtained through keel sighting, which is carried out just prior to the installation of the draught mark. However, the vessel may not be completely outfitted at the slipway. At such instant, there is a possibility of the load acting on the hull, which may be different from the actual lightship weight distribution. Additionally, action-reaction forces due to lightship weight (downward force) and dock blocks (upward force) impact the deflection of the keel while the ship is in slipway. Further, the deflection of the completely outfitted ship post waterborne is different from the deflection experienced by the ship at slipway.

[6] Further, if two sister ship’s draught marks are marked at different stages of ship construction; the ship weights will be different and hence the keel deflection obtained through keel sighting will be different. This may lead to different draught marks for sister vessels.

[7] To resolve the issue of accurately marking the draught lines, the present invention proposes a new method.

SUMMARY OF THE INVENTION:

[8] It is an object of the invention to describe a method to accurately detail the draught markings.
[9] It is a further object of the invention to describe an improved method by which the draught marking may be made even if the ship is partially outfitted.

[10] The present invention pertains to an improved method of keel sighting and draught marking, addressing common challenges faced by traditional approaches.

[11] In an aspect, the method for sighting of keel and draught marking in ships comprising steps of determining a geometrical mean of the keel plate thickness across the length of a ship, transferring the geometrical mean of the keel plate from aft and fore of the block to a fixed pillar outside ship upon placement of the first block on the slipway and extrapolating along the length of a ship on both sides while considering the slope of the slipway.

[12] In an aspect, the geometrical mean of the keel plate thickness is calculated by measuring the thickness at multiple points along the length of the ship and determining the average thickness.

BRIEF DESCRIPTION OF DRAWINGS:

[13] The invention has other advantages and features which will be more readily apparent from the following detailed description of the invention and the appended claims, when taken in conjunction with the accompanying drawings, in which:
Figure 1 illustrates the known method of draught marking.
Figure 2 illustrates the improved method.

DETAILED DESCRIPTION OF THE INVENTION:

[14] While the invention has been disclosed with reference to certain embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the invention. In addition, many modifications may be made to adapt to a particular situation or material to the teachings of the invention without departing from its scope.
[15] Throughout the specification and claims, the following terms take the meanings explicitly associated herein unless the context clearly dictates otherwise. The meaning of "a", "an", and "the" include plural references. The meaning of "in" includes "in" and "on." Referring to the drawings, like numbers indicate like parts throughout the views. Additionally, a reference to the singular includes a reference to the plural unless otherwise stated or inconsistent with the disclosure herein.
[16] The figures and protocols have been represented where appropriate by conventional representations in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having benefit of the description herein.

[17] Certain wordings appear in the specification have defined meaning. The expressions “keel” and “draught (draft) marking” are defined in the Background of the Invention. “Ship” or “vessel” are similar words, which can be used interchangeably. Both the words include warship, commercial ship or any other ship. “Slipway” is an inclined solid surface from which the ship is moved into or out of the water. “Outfitting” concerning a ship is a process of ship construction.

[18] The present invention discloses an improved method for sighting keel and draught marking.

[19] Fig.1 illustrates the traditional method for draught marking.

[20] Fig.2 illustrates the improved method for sighting of keel and draught marking in ships. The method comprises of determining a geometrical mean of the keel plate 11 thickness across the length of a ship 10, transferring the geometrical mean of the keel plate 11 from aft 10A and fore 10B of the block to a fixed pillar 12 outside ship 10 upon placement of the first block on the slipway and extrapolating along the length of a ship 10 on both sides while considering the slope of the slipway.

[21] In an embodiment, the geometrical mean of the keel plate 11 thickness across the length of the ship is calculated by using the following equation:

S (ti x li)
Sli

Where, ti = thickness of keel plate
li= length of the keel plate with thickness ti

[22] In an embodiment, the improved method described is adapted to place the draught marks independent of the keel deflection, which is unavoidable as the ship construction progresses.

[23] Although a particular exemplary embodiment of the invention has been disclosed in detail for illustrative purposes, it will be recognized by those skilled in the art that variations or modifications of the disclosed invention, including the rearrangement in the configurations of the parts, changes in steps and their sequences may be possible. Accordingly, the invention is intended to embrace all such alternatives, modifications, and variations as may fall within the spirit and scope of the present invention.

[24] The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching.

ADVANTAGES OF THE INVENTION:

[25] The present invention provides a method for sighting keel and draught marking in ships that achieves a systematic approach for sighting of keel and draught marking, reducing the time required for these crucial tasks.
[26] The present invention provides a method for sighting keel and draught marking in ships that reduces errors, rework, and the need for modifications.
[27] The present invention provides a method for sighting keel and draught marking in ships that ensures accuracy during construction by distinguishing draught marks from dynamic keel deflection.
[28] The present invention provides a method for sighting keel and draught marking in ships that offers flexibility by allowing draught marks to be placed independently of loading conditions, thereby enhancing the efficiency and precision of the shipbuilding process.
,CLAIMS:1. A method for sighting keel and draught marking in ships, comprising steps of:
determining a geometrical mean of the keel plate 11 thickness across the length of a ship 10;
transferring the geometrical mean of the keel plate 11 from aft 10A and fore 10B of the block to a fixed pillar 12 outside a ship 10 upon placement of the first block on the slipway; and
extrapolating along the length of a ship 10 on both sides while considering the slope of the slipway.
2. The method as claimed in claim 1, wherein the geometrical mean of the keel plate 11 thickness is calculated by measuring the thickness at multiple points along the length of the ship 10 and determining the average thickness.