🔍 Key Concepts

• Free surface effect and how it impacts a vessel’s transverse stability (GM) • Relationship between displacement (ship size/weight) and the moment of inertia of the free surface • How free surface correction is applied: it depends on the free surface, not on the cargo weight

💭 Think About

• Think about what happens to the righting arm (GZ) and metacentric height (GM) when free surface is present in partially filled tanks. • Consider whether a larger, heavier ship with the same tank breadth and filling condition would feel the same, more, or less reduction in GM from that same free surface. • Ask yourself: does the free surface moment grow at the same rate as the ship’s displacement, or faster/slower, as ships get bigger?

✅ Before You Answer

• Recall that free surface correction (FSC) is proportional to the moment of inertia of the free liquid surface divided by displacement. • Verify whether increasing displacement (with similar tank geometry) makes the ratio in the FSC formula larger, smaller, or unchanged. • Confirm whether the question is asking about the effect per unit displacement (how badly GM is reduced) rather than just the absolute size of the ship.