What happens to the effective KG of a ship when filling an empty double bottom tank?

When an empty double bottom tank is filled, it has a significant impact on the center of gravity (KG) of the ship. Filling the tank adds weight low in the hull, causing the effective KG to increase. This is because the weight of the liquid in the tank is added at a relatively low vertical center of gravity compared to the ship's overall center of gravity.

As the KG increases, the metacentric height (GM) decreases, which indicates a reduction in the ship's stability. A lower GM suggests that the ship will be less able to right itself after being heeled over by external forces. Additionally, if the filling of the tank is uneven or the distribution of fluid is not symmetrical, it can lead to a list, or sideways tilt, which further affects the stability and handling of the vessel.

In summary, filling the double bottom tank raises the effective KG, decreases GM, and can potentially cause a list, all of which affect the overall stability of the ship. Understanding this relationship is crucial for maintaining safe and effective vessel operations.