Page 45 - statbility for masters and mates

Chapter 5
Effect of density on
draft and displacement
Effect of change of density when the displacement is constant
When a ship moves from water of one density to water of another density, without there being a change in her mass, the draft will change. This will happen because the ship must displace the same mass of water in each case. Since the density of the water has changed, the volume of water displaced must also change. This can be seen from the formula:
Mass Volume Density
If the density of the water increases, then the volume of water displaced
must decrease to keep the mass of water displaced constant, and vice versa.
The effect on box-shaped vessels
New mass of water displaced Old mass of water displaced ; New volume new density Old volume Old density
or
New volume Old density Old volume New density
But volume L B draft ; L B New draft Old density L B Old draft New density
New draft Old density Old draft New density
Example 1
A box-shaped vessel ¯oats at a mean draft of 2.1 metres, in dock water of density 1020 kg per cu. m. Find the mean draft for the same mass displacement