The role of ANCHOR (in a Ship - illustrated)

The caption sure would mean different things to different people.

NZ High Commissioner to India has apologized to CM Sheila Dikshit for the racist remarks made by an anchor (Paul Henry) in a talk show. There are anchors for TV / Radio show and for the various entertainment programmes who present the show interlaced with glamour. Star News made an initiative to find out budding talents who aspire to become anchors. It was a multistage elimination process to select Star Anchor from amongst thousands of aspirants. The first two selected were awarded Ford Figo car and opportunity to become anchor in Star News.

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The news of Greenpeace activists attaching a survival pod to the anchor chain of Stena Carron off Bressay prompted me to write something on anchor. Purely an attempt by a non-technical person, not a sea-farer to write something solely based on some articles collated and things seen from a distance.

                                                        the survival pod can be seen here.

                                                      greenpeace activist inside the pod

The life near Marine beach has influenced me in many ways – there are days when we sat in beach, enjoyed the sea breeze, discussed everything under the sun. The huge vessels that float on the Bay of Bengal, the fishing trawlers, catamarans all captivated us. One would wonder about the movement of those gigantic floating objects that carry passengers, cargo, oil, containers and more. Though from the sands one can hardly make out the different types or for that matter cargo that was being carried.


Probably it was the fascination for sea and venturing into it would have made people sail without fathoming the depth, the distance or the sustenance of the equipment that they depended on. Men would certainly have ventured into the sea much before the construction of modern day boats and ships. Ships and boats would have developed alongside mankind. We have read of wars where the power at sea had a major role to play. Chozha and Kalinga kings went to Ceylon, Burma and beyond and established their kingdoms over there. In tamil literature there are proverbs and adages of venturing across the sea for gaining riches. Have often wondered why the vessels would be stopped as though the ship contains advanced controls and automation, would not have brakes. When it is required to be held at a place from drifting astray, anchors are used. Here is an amateur attempt to write something on anchor !!


The purpose of anchoring is to secure the vessel and stop drifting due to the actions of wind, wave, tide and currents. A vessel closer to land is secured to a dock, piling, mooring buoy etc.,

                                                 ship anchored mid sea - illustration.

                                                             vessel tied at the port
Anchor is not a machine or equipment. For those who have absolutely no idea, an anchor is a heavy object, often of metal, used to attach the ship to the bottom of body of water at a specific point to keep the ship from drifting (moving). To put it crudely, anchor is like a large rock. When one end of a rope from the boat is tied to the dead weight, it is anchored. But this may not work when there are strong winds and tides act on the boat. A permanent anchor is often termed mooring. The anchor is attached by chain, cable, mooring line. The hole in the vessel’s hull through which the rode passes is called ‘hawsepipe’ as the thick mooring lines are known as hawsers.


Anchors are dropped into sea in the sea bed, it contains a chain (ropes in case of smaller boats) – the extra length would allow movement depending on weather conditions. Of course nothing is as simple as they are written. Legends are agog with stories that in olden days tying people to anchor and throwing them into sea was one method of execution (Recall Kamal being thrown into the sea in the opening scene of Dasavatharam). It is believed that the stones shaped like letter T in Tutankhamen’s tomb could be anchors. Over thousands of years, this developed into rudimentary anchor, and its design improved gradually. It is also a fact that the design of anchor has not changed much over the years.

                                         anchor of Lexa Maersk(courtesy : http://www.menkent.dk/)

The role of anchor can be simply explained by the principle of resistance to the movement force of the vessel. The primary ways of achieving this are the sheer mass and by hooking to the sea bed. Permanent moorings use large masses resting on the seabed. For temporary anchors, this is not practical. These anchors are stored on board and are dropped whenever necessary. The metal flukes on them hook on to the rocks in the bottom or bury themselves in soft bottoms.


On an anchoring run, the ship would lay the anchor together with a length of its iron cables on the seabed. Besides the weight of the anchor, the weight of the huge iron cables connected to the anchor also secure the ship. As extra length of chain is always allowed, the ship would be held to a circular area, the radius of which would be determined by the length of the cable released.

                                          anchor of Lexa Maersk(courtesy : http://www.menkent.dk/)

For an anchor to be effective, the anchor should be strong enough to withstand the strains and rode should be of necessary length. To be effective, the anchors should have sufficient weight for initial penetration, should bury deeply when subjected to horizontal pull, once buried should offer resistance to movement in the direction of pull, should remain rotationally stable even when pulled through the seabed and should break out of the ground easily when pulled upwards.


When the currents are high, the ship could drag the anchor or sever it at some weak link. A ship in water is subjected to wind and water forces and if restrained, it has to oppose these forces. The ship can maintain its position by steaming into the wind or current using energy.  According to the laws of physics, the primary purpose of an anchor is  not to hold the ship, but to hold one end of the chain on the seabed.  Given a chain long enough not to drag, any anchor at its end is entirely superfluous. The anchor occupies a smaller stowage space than the length of chain that it replaces: that is its engineering advantage over chain. As chain length is dropped on the sea bed and as the ship moves, a curve is formed, this is known as catenary.


A stiffly anchored vessel without scope for movement would be battered to pieces by wave action. This is what happens to most vessels that run aground.


In my experience in Kakinada, a claim of a fishing trawler reportedly was reported to have run aground in Hope island off Kakinada. I ventured into the sea in another fishing boat, reached the island and on the other side could see the fishing boat crouched on the sand. The salvage efforts were simple – to remove the sand from the bottom of the boat manually (sounds simple but very difficult to remove wet sand embedded under the weight of the boat against rough waves) dig on the sides, put wooden logs, pull it back to the sea by ropes tethered to another fishing boat, also push the boat manually. They would break and dismantle the engine from its cabin bed first.  This was done more to lighten the boat ; pulling a bare hull from sand to water is relatively easier.  Unfortunately, in this instance, nothing worked.  In a couple of days, all that remained were some planks and the huge fishing trawler had vanished. If none of us had seen it earlier, even the entire episode of running ground and then reduced to planks would have remained a story and we would have doubted the innocent fisherman of creating a story after intentionally breaking the boat for a TL claim.


As the boat stood aground, one side of it is battered by heavy waves and wind and the wooden structure slowly started giving way. In a few hours time, the remnants were only few planks. This could happen to a Ship as well though it is considered structurally much stronger and made of steel rather than wood.


As against a vessel that has run aground and immobilized, the anchor would allow movements of ship in three dimensions of yaw, pitch, roll and drift within design limits. ‘Aweigh’ is an important terminology describing the hanging anchor – not resting on the bottom. An anchor would be on aweigh when it is being hauled up from the bottom and is to be stored.


There are many more principles, types, angle of attack, scope, terminology – not all comprehensible to learners like us. Generally, the anchor and chain require little maintenance. Obviously such heavy weight of anchor and its chain cannot be manually hauled or dropped, there is something known as windlass which consists of cable lifter, mooring drum and warp which rotate and do the anchoring process.


Coming to the opening para, Stena Carron is a specialized vessel build by Samsung designed for exploration, batch drilling, capable of operating in depth of 10000ft of water. It has huge storage capacity of oil, has 6 – 7.4 MW diesel gensets, 6 sets of variable speed propellers, helicopter deck and accommodation of cabins, office, hospital, gym etc., Activists of Greenpeace trying to stop deepwater drilling taking place have attached a survival pod to the anchor chain, providing the campaigners a safe and comfortable haven from which to prolong their protest. Thus an anchor meant to prevent drifting is stopping it from doing its intended activity.

Hope this provided some basic inputs on anchor


Regards – Sampathkumar S
PS : The top two Star Anchor winners were : Akshay Shukla and Meenakshi Kandwal and the photo at the start of this article is that of Ms Kandwal