Estimate effective GM from an observed natural rolling period using the Weiss/IMO formula - no inclining test required.
Formula
$$ GM = \frac{4 \pi^2 (C \cdot B)^2}{g \cdot T^2} $$
Symbol legend
| Symbol | Meaning | Unit | Source |
|---|---|---|---|
| $B$ | Ship beam at waterline | m | ship particulars |
| $T$ | Natural rolling period | s | timed observation |
| $C$ | Empirical roll factor (≈0.373) | - | IMO Res A.749(18) |
| $g$ | Gravitational acceleration | m/s² | 9.81 |
| $GM$ | Metacentric height | m | result |
Sources
- IMO Res A.749(18) - IS Code Part B §3.2.
- Derrett & Barrass Ch.16.