LOADLINES OF A VESSEL
The below shown diagram shows the port and starboard side loadlines of a cargo ship. To see the port side loadlines, cover up the right 1/3 of the sketch. To see the starboard side loadlines, cover up the left 1/3 of the sketch.
The WNA loadline is only required by vessels less than 100 metres in length, trading in the North Atlantic during the winter season.
All the lines are 25 mm thick, are cut into the shell plating and are painted white or yellow on a dark background or black on a light background. The upper edge of each loadline indicates its exact level. The top of the deck line indicates where the top of the freeboard deck would meet the outer side of the shell plating, if produced.
Directly below the deck line is the Plimsoll mark (or loadline disc) and the vertical distance between them is called the Statutory Summer Freeboard. The centre of the roadline disc is at the middle of the upper edge of its 25 mm thick, painted, diametric line. The deck line and the Plimsoll mark are situated exactly amidships.
Exactly 540 mm forward of the disc is a vertical line 25mm thick with horizontal lines, measuring 230 mm x 25 mm, on each side of it. On its forward side the lines are marked S, T and W (also WNA if applicable) The lines on the after side are marked F and TF. The upper edge of the line marked S is in line with the horizontal line of the Plimsoll mark.
In summer zones, the ship can load up to this line in salt water. The vertical distance between the upper edges of S and T (and also between S and W) is 1/48 of the summer draft of the vessel. The WNA mark, if applicable, is situated exactly 50 mm below the W mark (measured between their upper edges). The vertical distance between the upper edges of the lines marked S and F, and also between T and TF, is the FWA of the ship.
Ref : Captain Damley website and Ship stability at Operational Level by Capt H Subramaniam
