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Chapter 21 Bilging and
permeability
Bilging amidships compartments
When a vessel ¯oats in still water it displaces its own weight of water. Figure 21.1(a) shows a box-shaped vessel ¯oating at the waterline WL. The weight of the vessel (W) is considered to act downwards through G, the centre of gravity. The force of buoyancy is also equal to W and acts upwards through B, the centre of buoyancy. b W.
Now let an empty compartment amidships be holed below the waterline to such an extent that the water may ¯ow freely into and out of the compartment. A vessel holed in this way is said to be `bilged'.
Figure 21.1(b) shows the vessel in the bilged condition. The buoyancy provided by the bilged compartment is lost. The draft has increased and the vessel now ¯oats at the waterline W1L1, where it is again displacing its own
Fig. 21.1(a)
