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→Centre of Gravity
The righting moment is a force generated by the righting arm (GZ). The righting arm is the transverse distance between the centre of gravity (CG) and the centre of buoyancy (CB) [28]. Hopefully this will become clearer as you read on.
=== Centre of Gravity ===
The centre of gravity (CG) is the point inside the hull where the downward force of gravity equals the weight of the boat, i.e., its displacement. It is the midpoint of the mass. Keeping weight low in the hull lowers the CG. A low CG increases stiffness, i.e., resistance to heeling and capsizing. That’s why engines are mounted low, ballast is put in the keel; and heavy superstructures or loads on deck are bad. Makes you wonder about dinghies on the boat deck.
=== Centre of Buoyancy ===
The centre of buoyancy is a counteracting force to gravity. It is the midpoint of the underwater volume of the boat, i.e., it is the centre point of the geometric shape of the hull. It is on the centre line of the hull, usually amidships with a vertical height just a bit more than half the draft.