Section 6 Definitions

6.1.1 Rule length, L, is the distance, in metres, on the deepest load waterline from the forward side of the stem or rake plating to the after side of the aftermost rudder post, or to the centre of the aftermost rudder stock if there is no rudder post. L is to be not less than 96 per cent, and need not be greater than 97 per cent, of the extreme length on the deepest load waterline. In ships with unusual stern arrangements the Rule length, L, will be specially considered.

6.1.2 Amidships is to be taken as the middle of the Rule length, L, measuring from the forward side of the stem or rake plating.

6.1.3 Breadth, B, is the greatest moulded breadth, in metres.

6.1.4 Depth, D, is measured at the middle of the length, L, from top of keel to top of the deck beam at side on the uppermost continuous deck, or as defined in appropriate Chapters. When a rounded gunwale is arranged, the depth, D, is to be measured to the continuation of the moulded deck line, in metres.

6.1.5 Draught, T, is the maximum draught, measured from top of keel, in metres.

6.1.6 The block coefficient, C _b, is the moulded block coefficient at draught, T, corresponding to deepest load waterline, based on Rule length, L, and moulded breadth, B, as follows:

6.1.7 Length between perpendiculars, L _pp, is the distance, in metres, on the deepest load waterline from the fore side of the stem to the after side of the aftermost rudder post, or to the centre of the aftermost rudder stock if there is no rudder post. In ships with unusual stern arrangements the length, L _pp, will be specially considered. The forward perpendicular, F.P., is the perpendicular at the intersection of the deepest load waterline with the fore side of the stem or rake plating. The after perpendicular, A.P., is the perpendicular at the intersection of the deepest load waterline with the after side of the rudder post. For ships without a rudder post, A.P. is the perpendicular at the intersection of the waterline with the centreline of the aftermost rudder stock.

6.2.1 A passenger ship is a ship which carries more than 12 passengers.

6.3.1 For hull reference purposes, the ship is divided into 21 equally spaced stations where Station 0 is the after perpendicular, Station 20 is the forward perpendicular, and Station 10 is mid – L _pp.

6.4.1 Unless otherwise stated, the co-ordinate system is as shown in Figure 1.6.1 Co-ordinate system, i.e. a right-hand co-ordinate system with the X axis positive forward, the Y axis positive to port and the Z axis positive upwards. Angular motions are considered positive in a clockwise direction about the X, Y or Z axes.

Figure 1.6.1 Co-ordinate system