Heel is a vessel’s temporary sideways tilt, caused by an external force acting on the ship — and critically, it corrects itself once that force is removed, which is exactly what distinguishes it from list.
Heel vs List: The Key Distinction
- Heel — temporary, caused by an external force (turning, wind, waves); disappears once the force stops
- List — sustained, caused by an underlying weight imbalance (uneven cargo, flooding); persists until the actual cause is corrected
Confusing the two matters practically: a vessel heeling during a turn is normal and expected; a vessel listing at anchor with no external force acting on it indicates a genuine underlying problem requiring investigation.
Main Causes of Heel
- Turning — as a vessel turns, centrifugal force acting through the center of gravity, combined with the hydrodynamic forces on the turning hull, causes the vessel to heel toward the outside of the turn
- Wind — sustained wind pressure on a vessel’s above-water surface area can cause heel, especially beam-on to strong wind
- Wave action — rolling motion from waves produces continuously changing heel angles as part of normal seakeeping
Why Turning Causes Heel
When a ship turns, the rudder force and the vessel’s own turning motion create a combination of forces that push the hull to heel outward from the direction of the turn — a real, physical, momentary effect of the turning dynamics, not a stability defect.
Heel From Wind
Strong wind acting on a vessel’s exposed side can cause heel, especially at higher speeds or when beam-on to strong wind — again, temporary, correcting once the wind effect changes or the vessel’s heading changes.
Why Understanding Heel Matters for Stability Assessment
A vessel’s GZ curve (righting arm across a range of heel angles) is the fundamental tool for assessing how a ship responds to heel at any given angle — a vessel with adequate stability generates increasing righting force as heel increases (up to a point), which is exactly what allows it to return upright once the external force causing the heel is removed.
Angle of Loll: When “Heel” Signals a Real Problem
If a vessel with negative or very low GM adopts a stable tilt to one side even with no external force acting — this is angle of loll, a genuinely dangerous condition distinct from both normal heel and list, requiring immediate correction of the underlying stability deficiency.
Exam Relevance
The heel/list distinction, turning-induced heel, and its relationship to GZ curve assessment are core, frequently-tested Ship Stability topics in deck officer competency exams.