Deck General · Free Surface Effect
Free surface effect (FSE) is caused by:
- AWater on the weather deck draining to the low side
- BA liquid in a slack (partially filled) tank shifting when the vessel heels, creating a virtual rise of G✓ Correct
- CThe movement of B toward the low side when the vessel heels
- DAir spaces trapped beneath the waterline reducing buoyancy
Explanation
When a vessel heels, a free surface in a slack tank allows the liquid to flow to the low side. This shift produces a heeling moment that acts as if G has risen. The effective GM is reduced by the free surface correction: GM_eff = GM_solid - FSC.
Authority: Stability & Trim (USCG deck topic)
Practice the full Deck General bank
Free spaced-repetition quizzing across 2190 USCG exam questions — it schedules your reviews so the ones you miss come back until they stick.
Related Deck General questions
- Free Surface Effect
The free surface correction (FSC) for a tank depends on:
- Free Surface Effect
To minimize free surface effect in a fuel tank, the BEST practice is to:
- Free Surface Effect
A vessel has a calculated GM of 2.0 feet. The total free surface correction for all slack tanks is 0.8 feet. What is the effective GM?
- Free Surface Effect
Free surface effect is GREATEST when a tank is:
- Free Surface Effect
A vessel has two identical slack fuel tanks side by side. Installing a centerline watertight division in each tank (creating four narrower tanks) will reduce the total free surface effect by approximately:
- Stability Definitions
Displacement is best defined as: