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SEAMANSHIP

ANCHORING TO A SINGLE ANCHOR

In calm weather the anchorage is approached at slow speed and the anchor is let go while the ship has either headway or stern way. The cable is laid out, and engines are used to relieve stresses in the cable just before the vessel brings-to. The officer who is anchoring his own sip usually prefers to stop his vessel at the anchorage by going astern. When the propeller wash reaches the ship abeam of the bridge he uses that as a guide that the ship has lost way. The engines are then kept going dead slow astern as the anchor is let go. Engines are stopped almost immediately and the vessel drifts astern laying out her cable, which grows continually ahead. Just before the required scope is out, the engines are touched ahead. Just before the required scope is out, the engines are touched ahead so that the vessel gets her cable as gently as possible. This method ensures the chain being clear of the hull plating at all times.

Many pilots prefer the simpler method of arriving at the anchorage with a little headway on the vessel, letting go the cable, laying it out as the vessel moves slowly ahead, and touching astern just before the required scope is out. With this practice, the cable grows continually astern while it is being rendered and will probably harm the paintwork on the hull. This is rather more serious than it may sound, because often the paint is removed to the bare metal and corrosion sets in rapidly. This is apparent when a vessel dry docks, since there is usually an occasion during a voyage when the cable does grow astern.

In waters up to 20m deep the anchor and cable should be let go on the run, allowing about double the depth (of cable) to run before checking it on the brake. If the cable is snubbed as soon as the anchor touches the bottom the anchor will be dragged along the sea –bed and will be unable to gripe. Further, with the weight of the anchor off the cable, it sometimes happens that when the brake is released the cable will not render itself. This happens when there is a heavy weight of cable abaft the gypsy, leading down into the locker, and when the gypsy is in need of lubrication. By surging the cable initially, the anchor has a chance to embed itself before the cable tightens. There is little risk of a stockless anchor being fouled in this way.

In water of over 20m the anchor should first be walked back to within say 4 or 5 m from the sea- bed, and let go from there. This ensures that the anchor will not damage itself falling a considerable distance on to a hard bottom, and also that the cable will not take charge and run out so rapidly that it becomes extremely difficult to hold it on the brake. This practice therefore considerably lengthens the life of the brake linings.

In very deep anchoring depths, 100m and over, the entire operation of anchoring should be done under power. The gypsy should not be taken out of gear at all, because the heavy weight of cable between sea-bed and hawse pipe will undoubtedly take charge.

In a wind it is better to approach the anchorage heading upwind. The ship is more easily controlled and will make little leeway. If the wind cannot be brought ahead, however, the ship can let go the anchor in the usual way and, using her engines to relieve stresses on the cable, swing head to wind as she brings –to.

The weather anchor should be used so as to avoid nipping the cable round the stem. If the vessel is heading dead into the wind’s eye she should have her head cast off one way or the other before letting go the weather anchor. The cast should not be excessive, because the ship will rapidly seek to lie across the wind and develop a sharp swing to leeward. Correcting helm and bold use of engines should be used if the cast develops into a swing.

In a tideway the vessel should stem the tide and again anchor with headway or sternway, as in clam weather or in a wind. Her helm will be of use even while making no way over the ground due to the tidal stream running past her. If the tidal stream cannot be stemmed the cable should be rapidly laid out slackly across the axis of the stream. As she brings –to in the stream, the bight of the cable dragging across the sea-bed will bring her up to her anchor very gently. When anchoring in a tideway floating objects over side are sometimes used to determine whether the ship still has headway. It should be noted that these objects indicate the ship’s speed relative to the water, and a vessel stemming a stream with stationary floating objects beside her (i.e. pieces of wood, etc.) will have sternway over the ground equal to the rate of the stream. Only when these objects drift astern will the ship be stopped over ground or have headway over it.

When anchoring stemming a stream and also having a wind abeam, the lee anchor should be let go first. As she gets her cable, her stem will then swing to the wind, causing the cable to grow clear. If she uses the weather anchor her cable will continually be foul of the bow plating.

 

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