Location of Free Surface
The free surface effect is independent of the
location of the free surface within the ship. A free
surface with a certain length and breadth will, at any
given angle of heel, cause the same reduction in GM
(and, therefore, the same loss of stability) no matter
where it is in the ship—forward or aft, high or low, on
the centerline or off the centerline.
Depth of Loose Water
The free surface effect of a given area of loose
water at a given angle of heel does NOT depend upon
the depth of the loose water in the tank or compartment,
unless the loose water is shallow enough or deep
enough to cause the effect known as “pocketing” of the
free surface. Pocketing occurs when the free surface of
the liquid comes in contact with the deck or the