Ship Anchor

-
Image result for Anchors

A ships anchor is an important component, used to prevent the ship from drifting from its location due to wind and tidal currents. Generally, larger ships having two bow and one stern anchor. Anchors can either be temporary or permanent. Permanent anchors are used in the creation of a mooring, and are rarely moved; a specialist service is normally needed to move or maintain them. Vessels carry one or more temporary anchors, which may be of different designs and weights. The  anchoring  equipment of  a  ship  comprises  the  anchor, anchor  chain  and  the  windlass. Anchor chains are connected to a windlass that can either be of vertical or horizontal design. A vertical windlass is known as a capstan, and we shall describe the operation of the anchor and its components using a capstan.
The capstan has a drive wheel called a gypsy that is notched to suit the forged steel chain links.
The chain is fed from the capstan along the deck of the fo’c’sle head through a pawl and down through a hawsepipe pipe in the deck exiting at the ships bow. From here the chain drops downwards and is connected to the anchor using a shackle whose hardened steel pin passes through a hole drilled in the anchor central shank.
The  modern ship’s anchor  is  called  ‘Stock-less  Bower  anchor  and  is  developed  from  the  primitive  “ stock  Anchor”.


Stockless Anchor
The  modern  Bower  stockless anchor is  in  existence  since  the  days  of  steam  propulsion  and  has  been  developed  to  suit  the  stowing arrangement  in  the  hawse  pipe  of  the  ship  and  with  a  lower  holding  strength  than  the  stock  anchor. The modern  stockless anchor  has  a  holding  strength  of   five  times  its  weight  in  Newtons, whereas  the  ancient or  primitive  stock  anchor  has  a  holding  strength of ten  times  its  weight  in Newtons.  The  reason  for  this  requirement  of  lightness is  that  the  anchor  has  to  be  hauled  quickly (within  30 minutes maximum ),  when  the  weather  deteriorates   during  anchor  stay  and  the  ship  has  to  haul  up  the  anchor  and  proceed  to  sea. A stock  anchor  will take  longer  time  to  haul  up and  therefore  endanger  the  safety  of  the  ship.  In the  worst  condition  it  can  lead  to  capsizing  of  the  ship  especially  if  it  is in  light  condition or  in  the  best  condition  drag  anchor  and  run  aground  ashore. Whereas  in  a sailing ship  the  ship  is  normally  anchored  deep  inside   the  natural  harbour  where the  severity  of  the  sea  condition  does  not  reach. It should  be  understood  that  the    greater  the  holding  force  , the  larger  time  required  to  haul  up  the  anchor.  The  forces acting  on  a  ship riding  anchor  is  described in next blog.

Comments

Post a Comment

Popular posts from this blog

Introduction to Mooring Line

-
Image
The mooring refers to any permanent structure to which a vessel/ship may be secured. Examples include quays, wharfs, jetties, piers, anchor buoys, and mooring buoys. A ship is secured to a mooring to forestall free movement of the ship on the water. An anchor mooring fixes a vessel's position relative to a point on the bottom of a waterway without connecting the vessel to shore. As a verb, mooring refers to the act of attaching a vessel to a mooring. Mooring is often accomplished using thick ropes called mooring lines or hawsers. The lines are fixed to deck fittings on the vessel at one end and to fittings such as bollards, rings, and cleats on the other end. Mooring requires cooperation between people on a pier and on a vessel. Heavy mooring lines are often passed from larger vessels to people on a mooring by smaller, weighted heaving lines. Once a mooring line is attached to a bollard, it is pulled tight. Large ships generally tighten their mooring lines using heavy machin...
Read more

Anchor Size- rigging table

-
Image
After having found the equipment numeral from previous blog , the details regarding sizes and quality  may be obtained from the rigging tables provided in these regulations. From these table , we can find the following information The Equipment Letter Stockless bower anchors number of anchor Mass per anchor (kg) Stud-link chain cables for bower anchors Total length (m) Grade and Diameter (mm) of chain CC1———— low  strength. CC2———–medium strength. CC3———–high strength Towline Minimum length (m) Minimum breaking strength (KN) Mooring Lines Number Length of each mooring ropes (m) Minimum breaking strength (KN)
Read more

Introduction to Towline

-
Image
A tow line is used with a tug (tugboat or towboat) which is a type of vessel that maneuvers other vessels by pushing or pulling them either by direct contact or by means of a tow line. Tugs typically move vessels that either are restricted in their ability to maneuver on their own, such as ships in a crowded harbor or a narrow canal, or those that cannot move by themselves, such as barges, disabled ships, log rafts, or oil platforms. A tow line is the essential link between tug and ship. This applies to tugs operating alongside a vessel in the push-pull mode as well as to towing tugs fastened with a tow line to the bow or stern of a ship, also called `tugs towing on a line‟. Basic towline requirements A towline must fulfil two basic functions, firstly to function as the load-carrying link between tug and ship and secondly to cope with the dynamic loads resulting from the relative motion between tug and ship. This leads to the following basic requirements for towlines for harbo...
Read more