Which statement about ballast placement and stability is true?

• A. Lowering ballast in the hull increases GM and improves stability.
• B. Ballast placement has no effect on stability.
• C. Moving ballast high in the hull greatly improves stability.
• D. Ballast only affects draft, not stability.

Answer: (C)

Stability is governed by the height of the center of gravity relative to the buoyancy forces, described by the metacentric height GM. When ballast is placed lower in the hull, the weight is moved down, lowering the center of gravity (KG). This increase in GM makes the vessel more resistant to initial tipping and restores itself more effectively when tilted, so stability improves.

Placing ballast high raises the center of gravity, which reduces GM and the restoring moment, so stability actually decreases rather than improves. Ballast distribution affects stability, not just draft, so where you put ballast matters for how the ship sits upright in conditions that cause heeling.

So the true idea is that lowering ballast in the hull increases GM and improves stability.