OUPV & 100-Ton Master · Stability
The 'free surface effect' aboard a small vessel refers to the loss of stability caused by:
- ALiquid in a partially filled tank or bilge shifting as the vessel rolls✓ Correct
- BPassengers standing on deck
- CFuel being burned during a voyage
- DWind on the superstructure
Explanation
A partially filled (slack) tank or flooded bilge lets liquid surge to the low side as the vessel heels, moving the center of gravity outboard and reducing the righting arm. Free surface is minimized by keeping tanks pressed up or empty and dewatering bilges.
Authority: Stability principles; 46 CFR Subchapter S
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