ANCHORS
Admiralty Pattern Anchor :-
Sometimes referred to as a ‘fisherman’s’anchor,this design is still popular within the fishing industry .It has been in use for many years,but because it has difficult stowage characteristics,e.g.cannot be stowed flat with the stock in position,it has been followed by more manageable designs.Once let go,the stock,lying at right-angles to the direction of the arms/flukes,causes a fluke to dig into the sea bed.This leaves the remaining fluke exposed,and the cable may often foul it when the vessel swings.When the anchor is not in use,the forelock in the stock can be unshipped,permitting the stock to be stowed parallel to the shank. The holding power of this anchor is generally considered to be very good indeed.The design is such that the stock is longer and heavier than the arms.This lends itself to the theory that the stock will be dragged flat along the sea bed,causing one of the flukes to bury itself.The angle of the stock would also be expected to turn the flukes in the direction of the sea bed as the anchor strikes the bottom.It is interesting to note that the longer the shank on these anchors the better it holds. The weight of the stock must be equal to 25 per cent of the weight of the anchor itself.Some stocks are designed straight if the weight of the anchor is over 12cwt (610kg),but a bent stock,would be encountered on anchors below this weight. The holding power of this common anchor will be,roughly speaking, three to four times its weight,depending on the nature of the sea bottom. It is unlikely to be seen on board merchant vessels,except possiblyas a kedge anchor.The weight in any event would rarely exceed two tonnes.
The Stockless Anchor :-
This is by far the most popular anchor in general use today,its principal parts .The head of the anchor is secured to the shank by a hinged bolt which allows the arms to form an angle of up to 45°with the shank.Further rotation of the arms are prevented by the head meeting the shank,at the built-in stops.The head of the anchor is comprised of the flukes,the arms,and the crown,which are manufactured from cast steel, whereas the shank is made of cast steel or forged iron.The hinge bolt and the shackle are made of forged iron.The stockless anchor’s greatest advantage is its close stowing properties and is easily housed in the hawse pipe when not in use.It is easily handled for all anchor operations,and made anchor beds (used with the close stowing anchor) obsolete. The overall size of these anchors will vary between individual ship’s needs but the head must be at least three-fifths of the total weight of the anchor. Holding power again varies depending on the nature of the bottom but,as a rule of thumb,it may be considered to be up to three times its own weight. The mariner should be aware that the rotation action of the moving arm may cause the anchor to become choked when on the sea bed so that the arms/flukes are not angled to the full amount and therefore losing the holding power effect.
Admiralty Cast Anchor :-
Used extensively as a bower anchor for warships,this anchor,because of good holding properties,has become very popular with the merchant service .With the increase in size of ships – the large tankers of today,for example – shipowners required an anchor with greater holding power.The AC Type 14,as it was called,was developed in the United Kingdom and has the required properties.Tests showed that it had more than twice the holding power of a conventional stockless anchor of the same weight.With such an obvious advantage,Lloyds Classification Society granted a 25 per cent reduction in regulation weight.The holding properties of this anchor are directly related to the pre-fabricated construction of the fluke area,the angle of which operates up to 35°to the shank.The angle of the flukes is made possible by a similar operation as with the stockless anchor,in which a hinge pin passes through the shank in the crown of the anchor.
CQR :-
the CQR sometimes referred to as a ‘Ploughshare’anchor or,in the United States,just as a plough anchor.It is generally used as a mooring anchor,especially for the smaller type of vessel.Holding power is again dependent on the type of ground that the anchor is bedding into but has been found to be very good.It also has extremely good resistance to drag.Like the Admiralty Pattern,it is difficult to stow.The design has been modified since its invention to incorporate a stock,and is often used as a mooring anchor .The CQR was a British invention by scientist Sir Geoffrey Taylor,who was a man with little boating experience.The design showed that the application of basic principles can sometimes improve on practical experience.Small-boat owners tend to have the choice of two anchors on the market,namely the Danforth and the CQR.Both anchors have reasonable holding power but the Danforth may have a tendency to glide whereas the CQR will not. For easier handling and stowing the Danforth would be more popular, but if it is decided to use an anchor for the job it was meant for,preference is generally given to the CQR
