What is the issue?Some holding grounds are very difficult to get a purchase upon and if the anchor cannot be made to set, the location will have to be abandoned unless alternatives are available.
Why address this?Anchoring techniques that enable you to get a purchase where others can find none, opens additional berthing opportunities and helps one sleep more comfortably at night.
How to address this?In situations where poor holding is experienced a 'sentinel', also known as a 'kellet', might make the difference.
Photo: Michael Harpur
A sentinel is a weight placed at a point along the rode to increase the chain's catenary so that the angle of pull upon the anchor moves towards the horizontal. The increased catenary and lowering of the effective pull angle helps the anchor dig in and stay in place.
A sentinel works by placing a leverage point on the chain. For instance, at the recommended anchoring scope of 5:1, it takes a horizontal force of almost 5x the pull to lift the sentinel off the seabed. Depending on conditions the deploying of a sentinel can almost double the holding power of the anchor whilst halving its workload.
Photo: Michael Harpur
A sentinel is particularly effective when used in conjunction with a nylon rode where the effects of the sentinel's weight is multiplied. When used with lines it can reduce the chance of the rode becoming cut or entangled by passing boats or, in shifting currents, reduce its likelihood to get entangled in your own rudder or keel.
Unfortunately, a sentinel can only be used in moderate winds or current. We have tried ours in a storm and found it useless as the chain is 'bar tight' with loaded up. In these conditions, it just sits on the bow tight rode and has zero effect. It also complicates anchor deployment and retrieval so we only used it when we needed it to solve a particular problem.
Our experience of the sentinel largely came about by having one, pictured above, come with our vessel. You can experiment with the effects of a sentinel by improvising with a SCUBA dive belt, a balled up section of chain or by sending down a durable bag full of rocks.
With thanks to:Michael Harpur, Yacht Obsession.
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