How does adding ballast low in the hull affect stability and trim?

• A. Lowers the center of gravity, increases GM, improves stability; can alter trim depending on placement.
• B. Raises the center of gravity, reduces GM, worsens stability.
• C. Has no effect on stability but increases speed.
• D. Only affects trim, not stability.

Answer: (A)

Lowering the center of gravity with ballast increases stability. When you add ballast low in the hull, the weight moves downward, pulling the center of gravity G downward. This makes the metacentric height GM larger, so the boat develops a stronger righting moment for small heels and resists turning over more effectively.

Trim, the boat’s forward/backward tilt, is affected by how that ballast is distributed fore and aft. If the ballast is placed symmetrically, trim changes little. If it’s biased toward the bow or stern, it will tilt accordingly—forward ballast tends to lower the bow, aft ballast tends to lower the stern.

So, ballast low in the hull primarily improves stability by lowering G and increasing GM, and it can alter trim depending on where the ballast is placed.