Paragraph 9

An example shall be included in such information to show the corrections applied to the transverse metacentric height and righting levers (GZ) for the effects of the free surfaces of liquids in tanks and shall be calculated and taken into account as follows:—

(i)

the metacentric height in metres shall be reduced by an amount equal to the total of the free surface functions for each tank divided by the vessel's displacement in tonnes. For each tank the free surface function is given by:—

1.025 \times pi

p = specific gravity of the liquid;
i = transverse moment of inertia of the surface

(i.e. \frac{{LB}_{3}}{12}

L = length and B = breadth of the surface of metres);

i.e. correction = \frac{σpi}{Displacement}

(ii)

the righting lever (GZ) curves shall be corrected by either:—

(a)

adding the free surface correction calculated under (i) above to the value in metres of the calculated height of centre of gravity of the vessel above the datum; or

(b)

making direct calculations of the heeling moment due to the liquid surface being inclined at the selected angle of heel where such calculations take proper account of the position of liquid surface in relation to the geometric configuration of the tank. The correction to the righting lever (GZ) at any selected angle of heel shall then be the summation of the individual heeling moments of the tanks considered, divided by the vessel's displacement.