Question 81Safety & Environmental - 1st Asst/Chief

The correct answer is C) Tanks which are 40% full. Tanks that are 40% full will have the greatest adverse effect on a vessel's stability due to liquid free surface. This is because at 40% fill level, the liquid in the tank has the maximum ability to shift back and forth, creating a significant free surface effect that reduces the vessel's righting arm and stability. Tanks that are pressed up (full) or completely empty do not have the same destabilizing free surface effect. The other options, A) tanks which have been pressed up to full capacity and D) tanks which have been completely emptied, do not have the same degree of liquid free surface as the 40% fill level, and therefore do not have as great an adverse impact on the vessel's stability.