Lessons
List from a wing-tank transfer
List: tan θ = (weight × distance moved) ÷ (displacement × fluid GM) — the distance is tank centre to tank centre, and the GM is always the fluid one.
The rule
- Fluid GM = KM − KG − free surface correction.
- Heeling moment = weight × the distance it travels, tank centre to tank centre.
- tan θ = heeling moment ÷ (displacement × fluid GM).
- Solid GM makes the list look smaller than it is — always use the fluid GM.
Worked example
| Displacement | 96400 t |
| KM at this draft | 12.62 m |
| KG in this condition | 9.57 m |
| Total free surface correction | 0.2 m |
| Weight transferred | 420 t |
| Distance between the two tank centres | 21 m |
- Fluid GM = 12.62 − 9.57 − 0.2 = 2.85 m
- Heeling moment = 420 × 21 = 8820 t·m
- tan θ = 8820 ÷ (96400 × 2.85) = 8820 ÷ 274740 = 0.0321
- List θ = 1.84°
Common mistake
Taking half the 21 m — centreline out to a single wing tank — as the lever.
The lever is how far the weight actually travels: port wing to starboard wing is the full 21 m, so halving it roughly halves the list you predict.