Before we proceed to the anchorage we have to know well the geographical data of the anchorage area, as well as the way an anchored vessel behaves and what kind of forces are applied on it by the dropped anchors. The charts, the pilots etc, after being updated, have to be red carefully. The most important factors that are taken under consideration for the selection of anchorage are the following:
a) the sea’s depth and the tide’s height in combination with the vessel’s draught.
b) the sea floor’s quality. The mud, the clay, and the sand, are considered to be a high quality sea floor that will securely hold the vessel. On the contrary, the rocks, the shells and the pebbles form a low quality sea floor, which in general is dangerous for anchorage.
c) The anchorage’s position. If the anchorage is protected inside a gulf or a bay, inside a harbour or an open bay.
d) The winds in the area, namely their usual direction and their intensity in the anchorage area. These are data that are given by the nautical aids (the pilots) and have to be taken under consideration. In case of a two-anchors mooring anchorage, their dropping has to be done to the side of the most prevalent wind.
e) The impact of the currents. The width of the tide, the direction and intension of the tidal or non tidal currents.
f) The contiguity with nautical dangers or other vessels and in general the available free space around the anchorage point.
g) The range of the chain. The range of the chain depends on all the aforementioned factors. Empirically speaking, the range of the chain has to be three or four times larger than the sea’s depth.
We approach the anchorage in low speed and cautious steering. Various visible points in the shore (lights, masts, churches, chimneys etc) function as directive points and aids that support the approaching technique.
The ideal approaching to the anchorage position is done when the directive bearing of an object and the variation of another object is used.
The dropping of the anchor
When dropping the anchor, the vessel has to move towards one direction, either ‘ahead’ or ‘astern’ so as the agglomeration of the chain and its engagement with the anchor to be avoided. Usually, when in the north hemisphere, the left anchor is dropped, given that because of the direction of the winds, if it is necessary to drop the second anchor, the chains will not be engaged. In case of bad weather, spare chain is loosened.
In case of wind or current the direction of the anchorage must be opposite to the direction of the current or the wind.
In case of a two-anchor anchorage we first drop the weather anchor and later the other. The distance between the anchors must be equal to the total sum of the wrench minus a wrench.
After the anchorage, for the time the vessel will stay at the anchorage, the vessel’s position must be inspected via visible points of the land with distance and bearing so as a possible change of the anchor’s position to be avoided.
During the mooring, one or both the anchors are dropped. If both the anchors are dropped, the opening between them must be relatively small, so as during the departure to be retracted simultaneously and their range to be sufficient for the protection of the vessel by the lateral wind. A range of approximately 4 shackles is considered to be sufficient. When the movement is astern, the impact of the propeller to the vessel’s turn is influential. Thereby, if possible, the usage of a clockwise propeller is preferable that holds the wharf to the left.
Before the bow reaches across the side of the mooring, the external anchor is dropped and with a ‘slight ahead’ movement one or two shackles are loosened and the second anchor is dropped. The external anchor is hold to the second shackle and the rudder is positioned toward the external anchor. Moving slowly ahead the vessel turns towards the external anchor, while the chain of the other anchor is loosened so as not to block the turn. When the vessel is sufficiently turned, it is maneuvered to go astern while the two anchors are progressively loosened and the stern approaches the anchorage point. If a small opening between the anchors is demanded, then the second anchor is dropped when the vessel is sufficiently turned towards the bow and starts to go astern. When the vessel approaches the wharf, the engines are stopped and she is immobilized while assisted by the anchors. The chains are immediately loosened for about 4 to 6 meters because on the contrary, if stretched, they would force the vessel to move forward. Finally, the vessel is fastened with the aft cable while the range of the chain is adjusted.
If the vessel has two propellers, then it is immediately turned, using the engines, across the anchorage position and then the anchors are dropped one after the other.
If the wind blows towards the wharf, the maneuvering is facilitated because the vessel tends to swing above its anchors while in position to inspect the leeway towards the wharf by using them. If the wind blows from the side of the wharf, the maneuvering becomes more difficult especially when there is only one propeller. Moreover, the maneuvering is facilitated if the wind is parallel to the wharf and comes from the stern.
Usually the aft cables of the moored vessel are fastened crosswise on two bollards on the right and on the left of the stern. When the wind blows from the flanks it is recommended that the both the right and the left aft cables are fastened to the windward bollard, because, in the contrary, only the windward cables will hold the vessel, whereas the leeward cables will be loosened and useless. The above method of securing the vessel via the anchors and the aft cables is known as ‘the Mediterranean moor’.
The most appropriate way for the approach of a quarter fast position is individualized separately for every type of vessel according to its operational characteristics. However, a series of general rules can be applied in the majority of the vessels’ types under the precondition that no winds or currents exist.
Single- Screw Clockwise Vessel
1. Alongside to the port Side
The pier is approached in a 15° to a 20° angle. The bow is directed to a point afore of the point of the vessel’s rotation (practically this is the vessel’s bridge). In order to set back the vessel’s advance, the vessel moves ‘astern’. This movement pushes the stern towards the pier and deflects the bow. At the same time, the appropriate cables are fastened to the shore and quarter fast is done securely.
2. Alongside to the starboard
The pier is approached in a 10° to a 15° angle (that is a smaller angle that the one of the left side) and the bow is directed to the point in which its bridge should be in the quarter fast position. When the bow approaches the to the pier the rudder goes ‘hard to the port’ and the movement ‘ahead’ is executed in order to deflect the vessel’s bow from the pier and bring the stern close to it. Before the vessel reaches its final position, the movement ‘astern’ is executed in order to set back its advance, while at the same time, the cables are fastened, which aids the safe maneuvering.
When the vessel sails in a windy weather in order to alongside and her speed diminishes, her leeway must be taken under consideration as well as the impact of the wind on the ship. It has to be noted that when the vessel’s engines are ‘stopped’ and the rudder is in the middle the vessel tends to turn towards the wind.
3. Alongside with Twin- Screw Ship
When at sail, a twin- screw ship sails in order to alongside the mariners must keep in mind: a) the speed must be the appropriate, so as to allow the vessel to steer. b) The rudder’s power lessens when the vessel’s speed lessens and when at low speeds the power zeroes. c) During the last stage of the alongside maneuvering, only the external propeller must be used in order to set back the vessel’s advance. This procedure is followed because the use of the external propeller produces wakes, which interceded between the vessel’s side and the pier push the stern away from the pier.
The vessel is maneuvered in such a way that during the last stages of the approach it moves in a 15° to 25° angle. The vessels sails to the point in which its rotation point is located (bridge) after the parabola. The engines are stopped in time and when the bow reaches the pier the movement ‘slow astern’ or ‘half astern’ is executed with the external propeller. The produced current from the propeller will push the stern of the vessel towards the pier. When the vessel’s advance sets back the vessel’s engines are hold. When the stern tends fast to the pier the inner propeller goes astern. If the vessel tends slowly to the pier, then the inner propeller is boosted by a ‘ahead’ movement of the external propeller. At the same time the cables are fastened in order to support the maneuvering.