10°/10° Zig-zag Overshoot Check
First and second overshoot angles in a 10°/10° zig-zag manoeuvre per IMO MSC.137(76): first overshoot ≤ 10° for L/V < 10 s, ≤ (5 + L/2V)° otherwise; second overshoot ≤ 25°.
First-overshoot limit
18.9°
First overshoot
PASS
Second overshoot
PASS (≤ 25°)
Formula, assumptions, and limits
$$\alpha_1 \leq \begin{cases} 10^\circ & L/V < 10 \\ 5 + L/2V & 10 \leq L/V < 30 \end{cases}, \quad \alpha_2 \leq 25^\circ$$
Zig-zag reveals yaw-checking and course-keeping. Slow-and-long ships (L/V > 30) get a 20° cap instead of a formula. Also run a 20°/20° zig-zag - first overshoot must stay ≤ 25° on that one.
Symbol legend
| Symbol | Meaning | Unit | Source |
|---|---|---|---|
| $L$ | LBP | m | particulars |
| $V$ | Speed through water | m/s | log at trial |
| $\alpha_1, \alpha_2$ | Observed first / second overshoot | ° | sea trial gyro record |
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