An anchor is extremely useful safety equipment usable in both, normal as well as critical operations. They say, “Never go ashore with anchors in your pipes”. This means that the anchor is usable as a last resort towards preventing the ship from grounding. The anchor, in normal operations can be used to; hold the ship in a position; execute a turn in limited area; etc.
The classic use of anchor, of course is during anchoring. To stop the headway, astern movement is given. In olden days, on a general cargo vessel with midship accommodation, after such maneuver, when propeller wash was seen abreast, Master would assume that the vessel had stopped over water and very gradually had started to fall astern. At this instant, he would let go the port anchor. The transverse thrust and gradual falling back would gently, lay the cable on sea bed.
If the propeller and rudder alone are not sufficient to turn particularly if the wind or current is setting the ship down dangerously, then the anchor can be dropped underfoot and a quick swinging can be executed.
Anchor for large vessels:
Large vessels which are medium-powered and are of single-screw type, are unusually sensitive to the effect of wind and are not easily controlled during berthing, the anchor;
- can keep the bow from being driven off;
- can greatly reduce drift or leeway; and
- can allow permitting the use of greater power on the propeller, thus, increasing the effectiveness of the rudder.
Anchor is used in a variety of ways to moor the vessel as a regular practice in different parts of the world. Let’s look at some of them in this article.
The open moor is used in areas where additional holding power is required in very strong tide or winds. The current or headwind or the dominating of the two is stemmed, keeping them on bows. Both the anchors are walked back till just above water level. The bow of the vessel is taken to a position where the windward or upstream anchor is to be dropped. The anchor is let go continuing to move ahead with a minimum headway walking back required number of shackles (approximately 1/3rd of the final length).
Once the second anchor position is reached, it is let go with minimum sternway. The vessel brings to on her weather cable. It gradually grows taut to windward. Bow develops a rapid swing into the stream or wind. The vessel is held on to the first anchor and paid out on the second anchor until both the anchors have even scope. Once both the anchors have even scope, additional shackles can be paid out as required, till the vessel is at the required position. Once the vessel is in the final mooring position, it is necessary to check on both the cables and ensure both the anchors are embedded and holding.
It is also referred to as ordinary moor, dropping moor or straight moor. The tide is stemmed. Vessel is stopped over the ground in a position about 3 to 4 cable lengths upstream. The stern way is obtained either by the effect of the tidal stream or by operating stern propulsion. Since the stern propulsion would be used, port anchor can be dropped. The vessel is allowed to drop astern. As she drops astern by approximately 9 shackles (This is the sum of two cable lengths. Half this length would be picked up soon) she is in the position to drop the second anchor.
The stern way is taken off in time before reaching this spot by use of engines ahead and by checking on the riding cable. The helm is given hard over towards the side away from the dropped anchor. After the second anchor is dropped, the riding cable is hove in and the cable of second anchor is paid out until the vessel is finally brought up. The engines are used ahead or astern as necessary to ease the weight on the cables.
Running or Flying Moor
The tide is stemmed, alternately the wind, if it has stronger influence. In case the two are from slightly different directions, as shown, the weather anchor is let go with engines going dead slow ahead. The engines may be stopped as required, maintaining the headway. The anchor cable is continuously paid up to say 9 shackles (the total of the final shackle lengths). The vessel will tend to stop due to the springing back or slackening of cable. This will be also due wind and tide which were stemmed. Now, the lee anchor is let go and the cable paid out. The slack on the weather anchor cable is picked up as the vessel drops astern. The vessel may need astern propulsion to move astern. Once the vessel has reached the position, (half way between i.e. 4.5 shackles on each cable) the lee anchor becomes the riding cable.
In case of Baltic moor vessel lies alongside in situations of onshore strong winds for average sized merchant ships while the wharf is not so strong. The vessel’s anchor and stern mooring wire rope are not only used to make a controlled approach to the berth but also used later, to hold the vessel in gusty wind conditions.
A 32 mm wire rope is passed form the after lead on poop deck on the offshore side, outside and clear of everything and secured to offshore anchor in a’cockbilled position. The after end of this rope is taken to a winch aft for heaving. The anchor is let go with some headway, with the wharf about a ship’s length off and stem abreast the final midship position. Cable equal to half a ship’s length is surged and then snubbed. The slack of wire rope is hove in. With the vessel tending to become parallel to the berth and onshore wind drifting the vessel alongside, the slack of cable and the wire rope is adjusted.
Ship’s fenders are to be used to prevent any damage. During unberthing the anchor and the stern mooring wire rope can be used to bodily draw the vessel off the quay. Once clear of the quay, engines and the helm can be used to clear the berth safely and get underway.
Mediterranean moor is used where the adequate depth alongside, is just over a limited length. The vessel stays stern on to the jetty with both her anchors lying ahead of her, fine on each bow. Let us take a case of going stern on to a wharf on port side. In calm weather, the maneuver can be done by letting go the offshore (starboard) anchor with slight headway, approximately in a position that is fine on bow of final position. Shortly after this, the port anchor is also let go providing enough slack on it. The starboard cable is veered and the vessel is allowed to round on starboard helm with dead slow ahead propulsion on. With 20o short of final ship’s line, astern propulsion is given. Transverse thrust acting on & the two anchors holding, will allow the vessel to take up the final position.
In many Caribbean ports, anchor is used in a big way to berth. Use of tugs is minimal. In many places, where the moorings are secured to buoys, one of the bower anchors is out with medium to long stay. Anchors are most commonly used for turning and for heaving the vessel off the berth, at the time of casting off. The anchor is also used when a vessel must stay alongside a quay, the strength of which is not enough to safely hold the ship in gusty winds. A typical berthing (coming to port and starboard) could be as follows:
In calm weather, a vessel can be berthed as shown, using the offshore anchor. To come portside to, the starboard anchor is let go with slight headway and starboard helm. If the anchor does not drag, the vessel will nicely turn as the cable is surged. The headline is connected as soon as possible. Astern engines are put before she is parallel to the berth. The starboard swing is controlled by headline.
To come starboard side to, in calm weather, approach at about 700 is made. Port anchor is let go and the vessel is maneuvered ahead with rudder hard over to port. Astern propulsion however will be just after passing the ‘parallel to quay position’. Both, head as well as stern lines will be connected as soon as possible. Where headline will be used to bring the bows in, the stern line will ensure the stern does not swing out due to transverse thrust.
In many ports, it is standard practice to use anchor at berth serving several purposes. Thus, at Aygaz (LPG) Terminal-Yarimca, Turkey, berthing is done with port anchor dropped to 5 schackles in the water. Mooring lines used are 2 headlines forward from starboard bow to a mooring buoy. 2 stern lines are from the port and starboard quarters to mooring buoys. Vessel heads 260° when all fast, as seen in the diagram below.
At Fort de France in Caribbean, the pilot berths the vessel port side alongside against a slight current. The berthing is done, preferably, in the early morning, due to absence of wind. The starboard anchor is dropped to 2 shackles on deck, when the vessel is about three to four cables from the berth and then is slacked away as required. The anchor is not of use for berthing but is for assisting unberthing.
At Tocopilla, Chile, ship is moored port side to on the wharf. Firstly, starboard anchor is dropped and kept slack and is finally slacked to 8 shackles. Two ropes are secured to each buoy. Two spring lines each are secured ashore. All lines are transferred and connected by boat. 14 ropes are used altogether. The berth is not sheltered and experiences swell.
At DTBASA/SE Carmopolis (Brazil), the berth is of a conventional type. A ship is moored with two anchors ahead and synthetic mooring lines to the 6 sea buoys round the ship. The berthing procedure and sequence of giving lines is indicated in the diagram.
At Exmounth (Australia) a straightforward approach from sea on recommended track is made. Reasonable deep water is available on the track. Berth is a ‘T’ head jetty with a face 48.75m in length with mooring and breasting dolphins. Distance between outer dolphins is 320 m. The depth alongside is 12.0 m. Berthing is usually starboard side to. Jetty is approached with bow slightly canted into berth and when approx. 100 m. off jetty, port anchor is let go to 3 shackles on deck and anchor dredged into berth. Forward slip line is sent away as soon as possible by mooring boat and when close enough, other lines are sent by the heaving line. The ideal time to unmoor would be on a flood tide and using the anchor to warp clear of the jetty.
Berthing at Morton (Bahamas) is done with port anchor, 2 shackles in water. Four ropes are sent to dolphins. Anchor remains in water with about 6-8 shackles to assist with departure. The sequence of mooring can be seen in the figure.