Deck Officer Toolkit

Rule of twelfths — semi-diurnal approximation: 1/12, 2/12, 3/12, 3/12, 2/12, 1/12 per hour. Indicative only; real tides follow the published tables for the port.

Radius ≈ cable out (shackles × 27.5 m) + LOA + hawse-to-bridge offset. Doesn't include yawing on wind/tide — leave additional room.

Error = true bearing − observed compass bearing, E positive/W negative. For gyro error and deviation work, apply with variation to find compass error — an observational aid only.

Inclusive day count between sign-on and sign-off — the raw figure administrations total for CoC qualifying service; each flag's own rules on eligible service still apply.