ANCHOR HOLDING POWER
Anchors have been used for almost as long as there have been boats on open bodies of water. They started as stones with a hole in them through which a cable could be passed; this then relied on the mass to resist movement.
These early models have developed over thousands of years and became steadily more complex with variations from logs filled with lead, large stones with tree roots lashed to them, to the traditional admiralty longshank shape from the 1700s that most would recognise as an anchor today.
However, since the development of this well recognised variant, anchors have continued to evolve into shapes and variants that many would not recognise as a ship’s anchor today. The purpose of all these variation and continued development?… Holding power…
The weight of an anchor drives the complexity and cost of the machinery used to handle it. Similarly, if we consider the oldest and simplest form of anchors, a stone with a rope attached to it, it is easy to imagine that its ability to hold a vessel in position is a function of its weight (or more accurately its submerged weight once buoyancy is considered). So to increase holding power, modern anchors look to rely on more than just their weight, but rather look at ways of getting an ever better grip on the sea bed and many do this by embedding themselves under the sea bed.
This embedment can be achieved by careful design of the anchor flukes so that when they have load applied in a certain direction, the flukes serve to draw the anchor in under the seabed. Other anchors achieve this by suction, where an open ended “can” of large diameter is lowered to the seabed and then water is pumped out causing the anchor to draw itself into the seabed or using inertia of a free fall anchor to penetrate the bed, dart like.
Whatever anchoring system you opt for it must take account of the loads expected of it, the water depth available and the soil conditions of the seabed on location.