Tranduction française de "Anchoring process" extrait de "The ANCHORING
Anchoring process extracted from The Complete Course by agreement
of Longbow Sail Training
Most yachts spend most of their working life moored in a marina. However there are many occasions when it is either just pleasant to drop an anchor and get away from other yachts or it is vital for safety to be able to anchor.
An anchor can be thought of as just a ’hook’ which is lowered to the sea bed and (hopefully) catches into the bottom and keeps the yacht secure. There are many types of anchor and each has advantages and disadvantages. A yacht should carry at least two - the main or BOWER anchor and a second lighter KEDGE anchor.
When coming to anchor, thought needs to be given to the process. It is not adequate to drop the anchor and cable over the side in one mass or the cable may fall on the anchor and foul it. Make sure that the cable is marked to indicate how much has been lowered.
A mark every 5 meters is sufficient and can be either painted (on chain) or lengths of line or cloth can be threaded through a rope cable or tied to chain. If using an anchor winch, keep a watch for the markings as the cable runs out.
If the cable is to be lowered by hand without a winch, pull the required amount out of the cable locker and flake it out on deck to make sure that it will run out without fouling. Check that it is correctly cleated by the fall so that it can be release under load.
There are two basic types of anchor winches The rotary winch is operated by any winch handle. To unlock and drop the anchor, the top (1) is turned anticlockwise and clockwise to raise. The other type uses a lever rocked back and forth to ratchet the chain in and a clutch to unlock to lower. The chain is fed to the chain locker via the navel pipe (5). Both can be hydraulically or electrically powered.
Note the eye spliced in the starboard bow mooring warp (3) and cleated rope, (2). The ropes are protected where they pass through the fairleads by polyethylene tubes (4).
To decide how much cable is required to be veered several factors have to be taken into account :
For an all chain cable the minimum scope required is 4 times the depth. For a rope cable 6 times the depth is recommended. With a rope cable there should be 5 to 10 metres of chain attached to the anchor to provide weight to keep the shank of the anchor as close to the bottom as possible and to minimize chafe.
In either case this is the minimum recommendation and if the holding is poor or there is a strong wind or tide (much) more cable must be veered. Where rope is used for an anchor cable, nylon is recommended because of its ability to stretch and this absorbs any snatching. When the yacht surges about it reduces the jerking as the yacht reaches the end of her scope. The weight of the chain itself lessens the snatch as the yacht has to ’pick up’ the curve of the chain as she moves backwards.
2. How long it is planned to stay ? The depth is measured on arrival and used to calculate the scope needed. That scope is usually adequate if the stay is for only an hour or so. However if staying over the next high tide and it is not near high tide on anchoring, calculate how much scope is needed at high tide and veer this amount. Similarly, if the plan is to stay for low water, make sure that when the tide falls there will still be enough water to float.
Calculate how much cable is needed and flake it out on deck. The helmsman will head the yacht in the direction that she will eventually come to rest and slow down. As she comes to stop, the helmsman will call out ’Stand by’ to warn the anchor crew to get ready. The yacht should gather a little sternway and then the helmsman calls ’Let go’. (Call out only as loudly as needed for the foredeck crew to hear, not the whole anchorage !!!!)
Let the anchor fall into the water followed by enough cable for it to reach the bottom. Snub the cable at this point but not sufficiently to stop the yacht going astern. Then let the anchor pull the cable out as the yacht goes astern. When the scope decided upon has run out, snub the cable and the yacht will jerk to a stop and dig the anchor in. If under power at this point, a half power burst astern will set the anchor and make it hold firmly.
Many anchor winch manufacturers recommend that when anchored the weight of the cable is not left on the winch. One way of achieving this is to lift the cable from the winch and make fast on a cleat.
A more elegant way is to use a mooring warp and tie a rolling hitch onto the cable and make the warp fast. Ease out a meter or so more chain and the warp will take the weight.
A yacht moving round a chain cable can sometimes be noisy as the chain moves over the roller. Using a warp will quieten the chain.
If the anchor does not dig in, the cable vibrates as it drags over the bottom and this will be felt on the cable. The anchor must be hoisted in and the whole process repeated. If the holding is poor, do not be surprised if it takes several attempts to set. An anchor can drag at any time and the longer it has remained set, usually the firmer it is holding.
For the first half hour or so after anchoring, it is wise to keep a watch to make sure the yacht is not dragging. This is done by taking either three bearings or transits and noting them in the log. A quick check can be made by finding a transit abeam of the yacht and looking along it every few minutes. If it is not exactly lined up, check the bearings.
Note there will be some movement as the yacht swings at anchor but will be small and will come back on to the bearings every swing.
In the UK and many other parts of the world, mooring alongside a pontoon or quay is normal. In the Mediterranean and some other places, it is the custom to moor stern or bows to the quay - either is acceptable.
The yacht is easier to handle going bows to. This gives more privacy in the cockpit but it is more difficult to get ashore over the bow. Mooring stern to often presents boat handling problems especially in strong cross winds. It also allows easy access ashore when made fast.
A gang plank is a necessity and there are many expensive ready made examples available but a 2m x 40 cms wooden plank will do almost as well. A couple of holes drilled one end for lanyards to keep it secure, and some padding to stop it damaging the deck is all that is necessary.
Occasionally it is necessary to limit the turning circle as the yacht swings. The bower anchor is laid in the direction of the strongest stream. At least double the scope required is paid out and the kedge anchor is dropped. The bower cable is hauled in until the scope of both anchors is the same. The yacht will then swing in a very tight circle. Alternatively lower the kedge from the stern to prevent the yacht from swinging at all. Use to keep the yacht stationary in a very narrow river or a deep pool in an otherwise shallow area.
When the weather is going to be (or is !!) very bad, a second anchor will increase the holding power significantly. The second anchor can be laid out at about 40° to the first. A swivel would be useful but is difficult to fit without breaking the chain or rope. The kedge anchor can also be set in tandem with the bower anchor. A short length of chain is needed and should be made fast to the bower anchor chain. Both are then lowered and set.
An anchor weight will also help to keep the anchor set by keeping the pull on it horizontal.
As well as deciding how much cable to veer when anchoring, there are several more points to consider. Keep clear of fairways, shipping lanes and ferry routes. Apart from contravening rules, it is just plain dangerous for a small yacht to anchor in the way of much larger vessels and the wash will make it uncomfortable. The holding has been mentioned earlier and in order of holding qualities from good to bad, hard mud is best (provided the anchor digs in the first place) followed by soft mud then sand, shingle and gravel. Sea weed over any bottom will reduce the holding unless the anchor penetrates through it and rock provides unreliable holding. Also check that it is possible to up anchor and get away quickly in a crisis or at night. It is obvious that it is unwise to anchor in the fairway of a major port such as Portsmouth (below) but any fairway should be kept clear.
When staying at anchor for longer than an hour or so, it is vital to understand what the wind is likely to do while the yacht is at anchor. It is sensible to anchor on a weather or windward shore so that if the anchor drags, the yacht will drift seawards rather than ashore.
If the forecast is for a significant wind change, a sheltered anchorage may suddenly become exposed. Check when anchoring that it is possible to get out of the anchorage whatever the wind does. In some places it may be necessary to change anchorage if the wind changes.
The turning or swinging circle of a yacht and others nearby is an important factor when deciding where to anchor. Unless held by two anchors, all yachts will swing to wind and/or tide. Rope cabled yachts will turn in a larger circle than chain cabled yachts (scope is longer !). Lightweight and multihull yachts also have a tendency to ’sail’ round their anchors in a heavy wind and move in a random pattern. When properly anchored make sure that nearby yachts will not be fouled when the tide turns.
In the diagram, the tide is initially the strongest influence and the yachts are tide rode. As the tide slackens, the wind is the dominant force and the yachts become wind rode. Yacht B has a different characteristic from the others and does not swing as fast to the turn of the tide. A collision will result and Yacht B should have been anchored some way away from her current position.
In light weather and tide, it is possible just to pull the anchor up. There must be communication between the foredeck and cockpit to make sure the yacht is brought under control when the anchor is recovered.
If the weather is heavy, and the anchor is difficult to raise, the helmsman either sails or motors towards the anchor. Go at slow speed to avoid running over the anchor cable.
Traditional terminology can be used to tell the helmsman the progress of weighing anchor .
Make sure you are heard !
In a crowded anchorage, it is possible to foul another anchor. Typically this means that the cable has been laid across another and that when weighing, the fluke hooks on the other cable. Old moorings and chains on the sea bottom present similar hazards.
To help get out of such situations, an anchor buoy can be rigged. This is a small buoy attached to the eye on the crown of the anchor by a tripping line. If the anchor fouls, the line can be used to pull it away from the obstruction. The position of the buoy also warns other vessels where the anchor is so that they will avoid fouling it. The tripping line can provide a hazard especially at night to other yachts. An alternative is to rig a tripping line attached to the same place but brought back on board.