Marine Engineering : The Ship & Anchor - A Means to Keep the Ship Stationary

A ship has all the controls and automation but she is quite helpless when it comes to the simple concept of braking. There are no brakes on a ship and an anchor is used to hold it from drifting astray

Introduction

In this article we will learn about the ship anchor chain. First we need to know what an anchor chain means in context of the ship. As you know, when you park your car at night or on a hilly region, you simply apply the hand brakes so that the car doesn't move on its own. Unfortunately there are no brakes on the ship for the simple reason that the ship is floating on water. So when the ship is stopped and its engines are not running, there needs to be a mechanism to ensure that the ship does not drift freely in the sea. Just note that this is only necessary when the ship is stopped in open water. This is not required when the ship is moored at the port, since in such a situation the vessel is bound by heavy ropes.

The mechanism for holding the ship in place is the ship anchor chain. In this article we will learn about the ship anchor chain and how it helps to keep the ship stay at a particular point in water.

Ship Anchor & Chain

Basically the ship anchor chain arrangement consists of two parts - the anchor and the chain. The anchor is nothing but a heavy piece of metal which is normally in the shape of a fork, as you can see in the diagrams below. The exact shape and size of the anchor would vary depending on the size and type of ship. The anchor chain is made out of heavy metal links and it holds the anchor at one end, while the other end is fastened to the ship.

The Sea Anchor

The sea anchor is also an anchor with the only difference that it does not touch the bottom of the ocean but haggles midway between the sea surface and the seabed. The role of the sea anchor is the same as that of the conventional anchor, and is useful in situations where the sea bed is very deep. It is mostly used in smaller marine vessels such as kayaks, boats and smaller yachts.

Anchor Images

How is anchoring carried out?

Coming back to the ship anchor, let us see how an anchor is actually dropped into the sea. Whenever the anchor needs to be dropped in the seabed, the available marine charts of the sea area are used to determine the nature and depth of the sea floor. After the appropriate spot has been selected, the anchor is lowered into the water at a steady pace. A certain length of the anchor chain is kept loose so as to allow a certain movement of the ship depending on weather conditions and experience of the master. Of course the actual process of anchoring is not as simple or easy as described here, and the ship crew might have to try a few times before they find a proper spot. All types of ocean floors are not suitable for anchoring; especially soft mud-floors are least suited for anchoring.

The two adjacent pictures show a real ship anchor. The picture on the left shows a ship being tossed around by wind and the anchor is keeping it in place while the picture at the right shows a ship dropping the anchor near port.

A Common Misconception Cleared

I would like to clear a common misconception at this stage that the weight of the anchor holds the ship in place. This is not correct because the main role of the anchor is to grip the sea bed. The role of securing the ship is performed mainly by the chain rather than the anchor, though the latter has a role to play in that as well.

Once the ship is anchored properly, it is bound to remain in a certain circular area which is defined by the length of loose chain. Of course there are several other factors which need to be considered to ensure that the ship is safe during anchor. For example if there are several other ships in the vicinity, the navigating officers should ensure that the circular movement of one ship does not come in the way of the circular movement of the other ships lest they collide.

Another point you might be thinking is that when the ship is in the middle of the ocean, it may not be possible to anchor because of the depth of the seabed. Actually you are right in thinking along these lines but there is hardly a reason why ship should need to anchor in the deep sea. Even if the engines have to be stopped for some reason in the deep sea, the ship can keep floating without anchoring since there is hardly a soul (ship) in the vicinity.