Anchor Dragging in a Blustery Bay
You are anchored for the night in a sheltered bay in a 12 m cruising yacht. The forecast is for the wind to veer from SE 10 kn to SW 25 kn overnight. You anchored in 8 m of water at 18:00 using a 35 m length of chain and a 15 kg anchor, with a scope of about 4:1. At 23:00 the wind has veered as forecast and is now SW 25 kn with gusts to 30 kn. You notice the yacht is lying differently to the other anchored boats nearby, and a check of two shore transits shows you have moved about 40 m downwind since 21:00. The anchor alarm has not sounded. The holding ground is sand.
1. Diagnose what is happening and explain why the anchor alarm has not sounded.
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Diagnosis: The change in lying direction and the 40 m downwind movement against shore transits indicate the anchor is dragging. The wind veered from SE to SW and increased to 25–30 kn; the yacht has swung to the new wind and the anchor has lost its set, possibly because it was set in one direction and the veer pulled it out.
Why the alarm did not sound: The alarm is set to a radius around the anchor position, typically based on GPS. A 40 m movement may be within the alarm radius if it was set generously (e.g. 50–70 m), or the alarm may be based on a waypoint at the anchor drop position with a radius that the yacht has not yet exceeded. GPS drift and the fact that the yacht swung on her chain before dragging can also mask the movement. The alarm is a back-up, not a primary watch - visual transits are the reliable check.
Immediate concern: 40 m of movement in 2 hours in a veering 25–30 kn wind on sand is a clear drag. The situation will worsen as the wind builds.
2. Set out your actions from the moment you confirm the drag, in sequence, including how you would re-anchor.
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Immediate actions:
- Confirm and alert: Confirm the drag with a second transit check and note the rate. Wake the crew, life jackets on, brief them.
- Start the engine: Have it running and in gear-ready state before weighing anchor, so you have control if the anchor breaks out suddenly.
- Weigh anchor carefully: Motor slowly up to the anchor to take the strain off the chain, then weigh. Do not drive over the chain.
- Assess: Once clear, decide whether to re-anchor in the same bay or move. With SW 25–30 kn forecast to continue, choose a new spot with better shelter from the SW and good sand holding.
Re-anchoring:
- Choose a spot with clear swinging room and no other boats close downwind.
- Lower the anchor, then lay out chain to a scope of at least 5:1 (in 8 m, that is about 40 m of chain), more if conditions allow.
- Set the anchor by motoring slowly astern at about 1,500 rpm until the chain comes taut and the yacht stops, then hold for a minute to confirm it is biting. Take transits and note them.
- Re-set the anchor alarm to a tight radius around the new position (e.g. 25–30 m) and keep a visual transit watch through the night, with an anchor watch rota.
If the anchor will not hold: Move to a different bay or stand off under power until daylight rather than risk a lee shore.