free surface effect

nautical science

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Last updated

June 26, 2026

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The "free surface effect" in nautical science refers to a hazard that occurs when flooding water enters a damaged hull and is unconfined. This water runs to the lowest point, worsening the ship's heel (sideways inclination). This effect is particularly problematic in ships with large, uninterrupted interior spaces, such as ferries, where bulkheads are limited. The free surface effect can exacerbate heeling angles and is a significant consideration in damage stability calculations to ensure a ship can survive moderate damage and sink slowly without capsizing.1

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Damage buoyancy and stability
…damage stability is the “free surface effect.” Water that is unconfined—as flooding water that enters a damaged hull is likely to be—runs to the lowest reachable point, thus exacerbating the heel that caused the low point. Such a hazard is difficult to avoid in ships that must have interior…
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…damage stability is the “free surface effect.” Water that is unconfined—as flooding water that enters a damaged hull is likely to be—runs to the lowest reachable point, thus exacerbating the heel that caused the low point. Such a hazard is difficult to avoid in ships that must have interior…
Read More