Why the technique exists
A vessel manoeuvring in a confined or congested anchorage — or approaching a berth in a strong tideway — cannot always rely on engine power alone to control speed and swing. Dropping an anchor and allowing the cable to render slowly under friction, rather than bringing the vessel to a stop, gives the Master a controllable braking and pivoting force that the engine cannot replicate. The anchor does not hold the vessel; it restrains it. That distinction governs every decision.
The principle
When an anchor is let go and the cable is surged (rendered) rather than held, the friction of cable on the seabed creates a retarding force along the ship's fore-and-aft line whilst the bow is held broadly in position. The stern can be worked with the engine and rudder against this restrained pivot point. The effect is a controlled, predictable swing that is independent of tidal set. The technique is therefore most valuable when:
- Speed must be checked over a short distance without excessive astern power
- A precise swing in a confined turning area is required
- A strong fair tide would otherwise carry the vessel past her berth before she can be stopped
- Engine failure has reduced or removed stopping capability
Application: entering a berth or anchorage under command
The Master should brief the anchor party before arrival and confirm holding ground, water depth and cable scope available. The approach is made at reduced speed with the anchor ready for immediate letting go — cleared away, compressor ready, brake on.
At the chosen moment the anchor is let go and cable is surged. The key control inputs are:
- Rate of surge — releasing cable slowly maintains high friction and maximum braking; easing it freely reduces friction and allows the vessel to continue moving.
- Engine and rudder — used together to control the swing around the restrained bow.
- Cable length on the bottom — more cable gives more friction and holds the bow more firmly; the Master must be aware of the swinging circle generated.
Once manoeuvre is complete the cable is either brought up to short stay and weighed, or the vessel is secured with the anchor as a breast or spring to a berth.
Command considerations
The Master must assess holding ground before committing — soft mud or foul ground can cause the anchor to drag rather than render the required resistance, negating the technique entirely. In a tidal stream the anchor should normally be let go on the up-tide bow to maintain control. Cable party communications must be unambiguous: 'surge', 'hold', 'walk back' all mean different things and confusion at a critical moment removes the technique's advantage.
An anchor used in this way is working under dynamic loading; the Master must be satisfied that the windlass brake is capable of holding the expected load and that no structural limits are exceeded.