Single Anchor — Principles of Good Practice
When anchoring on a single anchor the cable must be able to swing without obstruction through a full circle. Scope is the governing factor: in normal holding ground and settled conditions a 4:1 ratio of cable to depth (charted depth plus height of hawsepipe at water) is workable; in deteriorating weather or poor holding ground 6:1 or more is required. Always verify depth, tidal range, swing circle, and that the resulting swinging room is clear of other vessels, shoals, and navigational hazards before letting go.
The anchor should be walked out to the seabed — not dropped from the hawsepipe — so the flukes land correctly and cable does not pile on top of them. Once on the seabed, the vessel is put astern to lay the cable along the ground and set the anchor. Tautening of the cable and the vessel checking her sternway confirms the anchor has held. Transits or a position fix should be taken immediately to detect dragging.
Scope and bearing to the anchor should be logged. A watch must maintain an anchor watch, monitoring position continuously.
Use of a Second Anchor — When and Why
A second anchor is deployed for four distinct purposes; the examiner will expect you to distinguish them clearly.
1. Increasing holding power (Moor) — both anchors deployed in line ahead, cables at roughly 180° apart. The full strain comes alternately on each. Used when the seabed area is limited or holding ground is poor.
2. Limiting swing (Open Moor / Fore-and-aft) — the two anchors are laid ahead and astern, constraining the vessel to a shorter arc. Used in confined anchorages, channels, or where tidal streams run predictably in one axis.
3. Riding to two anchors in a V (Hammerlock / Open Moor ahead) — both anchors laid at an angle (typically 30–60°) ahead. Increases holding power and reduces snubbing in a heavy swell. The angle should be kept modest; a wide angle reduces the resultant holding force significantly.
4. Emergency or dragging — a second anchor let go urgently to check dragging or to reduce speed of dragging toward a hazard.
Kedge vs Bower
A kedge is a lighter anchor used for warping, pulling off a grounding, or holding a particular heading in a current. It is not a substitute for the bower when windage and displacement require the full bower's holding capacity.
Command Considerations
As Master you must assess: holding ground quality (chart notes, echo sounder trace, local knowledge), depth and tidal range across the full intended stay, swing room for all vessels present, proximity of submarine cables and pipelines, weather forecast for the entire stay, and a contingency if the vessel drags. These assessments and the decision to anchor must be documented.