Managing your anchor

Alan Lucas says knowing your anchor effectively is as important as any other part of boat-handling.

A dragging anchor in good-holding ground is no stranger to those who unquestioningly obey the mantra of 3:1 scope (cable length to depth of water). This ratio can be okay in deep water where weight of cable produces a heavy catenary, but such things are less evident in the shallower depths favoured by recreational sailors (Diagram 1).

When dropping anchor there is no such thing as ‘standard scope’, it being dependent on type of ground, prevailing winds, weather forecasts and available swinging room. If an anchorage is crowded and you must use it, lay out as much cable as possible related to space available and, if necessary, compliment its holding power with a weight run down the cable to improve its catenary. The weight can be a commercial unit or a second anchor lowered on rope and attached to the main cable by an oversize shackle tied off just above the low tide level (Diagram 2).

In a commodious anchorage, economising on scope makes no sense whatsoever. The cable belongs in the water rather than in its locker as useless, unwanted ballast. A minimum scope of 5:1 – or even 10:1 if circumstances so dictate, should be the rough rule. To facilitate this, mark your chain every few metres with coloured cable ties.

Cleaning the cable

During strong winds over mud, cable accumulates less mud thanks to the self-rinsing action of gusts and lulls. During calm weather, when the cable lies almost dormant on the bottom, things get pretty messy when it is winched home. For this reason, cleaning cable after strong, gusty winds is easier than after a flat calm, but this is no excuse for frugality of scope in fair weather because calms have the nasty habit of producing storm cells while you’re ashore.

As for washing off, there are ways to ease the burden: For example, if your chain is stainless steel, its smooth surface will accumulate less mud in a given period of time than galvanised chain. That’s the good news: the bad news is that stainless chain costs four times that of galvanised steel and it work-hardens under changing stress levels. Furthermore, it is very susceptible to electrolysis if left too long in the water. (I have seen stainless chain links lose their welds completely [Diagram 3] after a few months underwater.)

On average, galvanised chain is the best choice and a deck hose eases the burden of washing off, or a dedicated water blast outlet might be fitted just below the anchor roller (Diagram 4). Otherwise, a person with a galvanised bucket and lanyard will find washing off tiring but cheap.

To extend the periods between re-galvanising and to reduce mud’s tenacity, dry chain can be periodically sprayed with silicone in its locker. Alternatives such as fish-oil, Lanoline and WD40 show promise in this regard but are not as slippery or as long- lasting as silicone.

A natural way to reduce wash-off time when weighing anchor is to start the process an hour or so early by shortening up every 10-15 minutes (weather and sea room allowing). This lifts the chain incrementally out of the mud to allow a natural washing process to take place. When the cable is vertical with the anchor about to break out, go astern rather than ahead to break it out then keep going astern dragging the remaining cable and anchor through the water whilst slowly winching it in. The beauty of breaking out astern rather than ahead is that you don’t over-ride your cable and cause damage to anti-fouling and lower topsides (Diagram 5).

And talking of over-riding your cable, this is common in wind-against-tide anchorages when deep-keel yachts suffer the most for the way they sail across and around their anchor to the constantly varying forces. Whether the cable is rope or chain, it regularly ranges aft beneath the hull where it scrapes the anti-fouling and lower topside paint. If you have a centreboard, lift it up to encourage the vessel to respond more to wind than current. Otherwise, reduce the damage by trying different rudder angles to discourage the most damaging angle of attack.

The above scenario is better or worse according to two things: anchor roller outreach and shape of stem. The modern, almost vertical stem is the worst off, the least amount of ranging causing the cable to gouge the topsides and scrape the anti-fouling paint. Its anchor sprit needs to be as long as possible, leverage and foredeck strength being limiting factors.

A forward-angled stem needs only a short anchor sprit or, if very raked, no sprit at all. But regardless of anchor roller outreach, damage in a bad windward-tide anchorage is only minimised, never prevented entirely.

Dredging and kedging

Anchor management in general goes way beyond the basic functions of the hardware involved and the holding of a vessel in one place. It includes manoeuvre-assistance, dredging (or ‘drudging’) anchor being one classic example.

When departing a berth – and presuming there are no submarine cables – dredging anchor is a means of controlling the bow of a vessel as she backs out in a beam wind that may blow the bow off in the wrong direction as she clears into the channel. To offset this, after singling up lines drop the anchor to the bottom and pay out about one third the depth, then secure the cable. Now warp her astern until negative tension is on the anchor cable then start reversing out as lines are let go. The anchor does not dig in, but its resistance forces the bow to track in a truer, more predictable line, fenders over both sides insuring against things going pear-shaped (Diagram 6).

A classic anchor management tool is that of kedging an engineless vessel out of a difficult berth or anchorage. There are many variations on the theme, but basically it works like this: A sheet anchor and its cable, with its inboard end attached to the mother ship, is lowered into the dinghy then rowed out to a chosen point beyond the berth or anchorage, its cable running out over the stern. At the end of its cable the anchor is dropped then used to haul the mother ship into the stream where she temporarily swings to the sheet anchor while sail is set and she gets under way.
If more distance-off is needed, the process of kedging-off is repeated as often as necessary (Diagram 7).

The sheet anchor is best on rope cable and chain trace to facilitate its easier handling into and out of the dinghy, and it can be smaller than the main bower because the manoeuvre should only be carried out during fair weather:
Patience – it should always be remembered – is a vital element when anchors become the alternative to engines.

In the days of sail-dependence, anchor management reached extraordinary heights, such as running the bower anchor over the stern under reduced sail to bring hundreds of tons of cumbersome ship to a halt before being bridled beam-to-wind for purposes of enemy engagement or berthing in congested ports. Even in today’s world of powerful engines, azimuth drives and bow thrusters, failures occur, leaving it to the good old faithful anchor to rescue a rapidly deteriorating situation. Learning its good management is no less important than any other aspect of boat handling.