Vertical center of gravity (VCG)

The vertical center of gravity VCG, written KG as a height above keel, is the vertical position of the ship’s mass centroid and the dominant variable in stability, since GM = KM minus KG. It is found by summing the vertical weight moments of lightship and every deadweight item and dividing by total weight, then adding the free-surface correction for slack tanks, which raises the effective KG. The lightship KG is fixed by the inclining experiment and never measured again directly. Raising cargo or adding topweight increases KG, cuts GM, and can drive the ship to a negative GM and angle of loll. KG is the loading-controlled half of every GM calculation.