Everyone knows that what is an anchor but most of us don’t know how does a ship anchor work? Anchoring a ship is a very crucial function that a boat or ship has to do in order to stay stable in water. An anchor digs into the seabed to hold a boat in position when the engines are turned off. They provide a safety role by keeping boats out of the surf or off the rocks due to water currents.
Here are some of the reasons why a ship needs to have an anchor:
- When the voyage orders not available
- When the pilot is not available
- An amendment to the passage plan
- When the berth or cargo is not available
- Adverse weather conditions
- Machinery breakdown
- Boarding delay
Let’s see how anchor works
How does a ship anchor work?
The process can be followed for both small boats and ships though with slight variation. The first step is to find the location to anchor the ship. In general, the location is selected by the pilot or captain of the ship. He then informs the crew where exactly the ship must be anchored and the crew anchors as per the direction. The ship must move to the position by reversing the thrust by slowing down which eventually slows down the speed of the vessel and supports to get into a position where it can be anchored easily.
Once the position is set the anchor must be dropped which must reach the sea bed and ensure that the anchor has reached the sea bed before they go for the next process. After dropping the full length of the anchor the ship must go in reverse to make sure that the anchor digs into the sea bed. This reversing process is known as going astern. Which confirms that the ship anchoring is done. This process may take between 15 to 20 minutes that depends on the depth of the water.
To ensure that an anchor set properly applies tension to the rode so the anchor goes through the bottom. This ill be done by fastening the line and apply reverse power. Even if your boat moves, reset the anchor and try again.
Many shippers make only half-hearted attempts to set the anchor by putting the boat in reverse for just a few seconds. To make sure that the anchor is set properly you must put a reasonable strain on the rode for a particular length of time to test the anchor set.
The scope is defined as a ratio of the length of the anchor rode from the anchor shackle and the water depth measured under the bow of the boat from the deck height. It must be about 7:1 which would be a good thing to have. If your boat swings then you need to go for resetting the anchor which is known as anchoring Russian Roulette.
Resetting becomes easy when wind and current come consistently from one direction, but every time it won’t be the same, some perform better some may not under varying angles of pull. An anchor may be dislodged from the seabed if the boat swings so far. Here are four techniques that can alert you when your boat swings:
- It would be good if you set an anchor alarm on your Chartplotter when your boat swings too far from the position where the anchor was actually set.
- Having an electronic compass or autopilot, then set the alert so it alerts you if the ship position changes radically.
- The best thing to handle alarms on your depth sounder set to maximum and minimum alarms to alert you if the water depth changes either away from or towards the shore.
- It would be a good idea to take bearings on outstanding landmarks when you anchor so you can identify the changes in position.
Anchoring Techniques with two anchors
Anchoring Bow and Stern: In tight anchorages, you may be required to restrict your boat’s bias to swing at anchor by dropping one anchor close to the beach and second anchor in the opposite direction, so that you can locate the boat precisely in the anchorage. Even you can also use the tension on one rode to support both anchors.
Two Anchors off the bow: Bob Ogg recommends to set one anchor into wind or current and the other anchor 180° away, then take both lines to the bow of the boat. This will allow the boat to swing around in a relatively small arc which enables the boat to pull against the anchor without causing it to reset when wind or current changes.
- Boaters voyaging to areas where there is a definite type of bottom must carry an anchor that fist for that bottom.
- Two anchors will be best fitted to anchor bow and stern in tight anchorages.
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