What is the effect on the KG if an empty compartment below a watertight flat is bilged?

When an empty compartment below a watertight flat is bilged, the effect on the center of gravity of the vessel, represented by KG, remains unchanged. This is because the bilged compartment does not introduce any additional weight or change the distribution of weight within the vessel; it is still essentially an empty space that was already accounted for in the stability calculations.

The watertight flat, which separates the bilged compartment from the water, means that any water entering would not affect the overall weight distribution or the position of the center of gravity since the compartment is devoid of weight-bearing cargo or equipment. Therefore, even if the water fills the bilged compartment, its presence does not affect the overall weight above the watertight flat and thus does not shift the KG.

In summary, since the bilging process does not introduce or remove weight in a way that influences the vessel's stability or center of gravity, KG remains unchanged, affirming the understanding of stability in terms of weight distribution within the vessel's design.