Marine Anchor – Used For Boat Berthing Stably
The boat is difficult for berthing when encountering the strong wind. It completely relies on boat anchor. The marine anchor is the main component of the anchoring and mooring system. One end is fixed on the boat with a marine anchor chain, and the other end is a barbed claw shape, throwing to the bottom of water or shore to highly stabilize the boat.
Work Principle Of Marine Anchor
Marine anchor is composited of anchor buckle, anchor bolt, anchor stock, anchor handle, anchor wrist and the symmetrical part on both sides is called anchor fluke which is the most important part of the anchor to grab into the dirt. After the ship is anchored, the anchor is sinking to the bottom of water under the traction of the anchor chain. The plane where the anchor wrist is located is perpendicular to the water bottom with the anchor rod. At this time, the anchor fluke will be in contact with the bottom of the water.
The length of the ship anchor chain is often longer than the depth of the water, so the anchor chain in the water bottom has a lying- flat state. When the ship is disturbed, the anchor chain will be pulled. The anchor in the bottom of the water under the action of the horizontal force. The role of the anchor itself acts on the contact point of the anchor fluke and the water bottom. The two-force synthesis makes an anchor move downward, which is anchoring the process. After that the anchor is pulled into the bottom of the water, which can provide the ability for boat berthing.
The Categories Of Marine Anchor
The factors that should be considered for choosing the marine anchor include easy operation, convenient to store and economic application. The most important factor is the anchor grip. The anchor grip is different because of the anchor type and the submarine soil.
There are many kinds of marine anchors. According to the different structures and uses, the ship anchor can be classified into a stocked anchor, stockless anchor, high holding power anchor and special anchor. The bow anchor adopted by the merchant ship is a stockless anchor, while the stern anchor sometimes adopt a stocked anchor or a Danforth anchor.
1. Stocked anchor
The anchor has the advantages of a simple structure, large holding power to weight ratio and high grip stability, but it has inconvenient anchoring operation and storage with an anchor stock. Therefore, this anchor should not be used as a bow anchor for commercial ships, suitable as a stern anchor, generally used for small boats.
2. Stockless anchor
It is also known as the hall’s anchor and the generally adopted stockless anchors for merchant ship are Hall anchor and Spek anchor. The anchor fluke and anchor rod can rotate at a certain angle and is a stockless type. The holding power to weight ratio is 2.5 to 4 and the maximum is up to 8. The anchor has a simple structure, throwing anchor operation and storage conveniently, so it is suitable for the bow anchor with the widest applications. But it also has the disadvantage of a small anchor grip. The Hall anchor is the earliest used type and the Spek anchor is an improved type of Hall anchor, which has the advantage that its anchor fluke can be naturally upward.
3.High holding power anchor
It is combined with the advantages of a stocked anchor and a stockless anchor. Because of the large gnawing soil of the anchor fluke and the large gripping force, it is suitable for the sandy or soft water bottom. The commonly used HHP anchors are the Martrosov anchor and Danforth anchor which is characterized by the deep gnawing soil, high stability, with large anchor grip. But the strength of the anchor fluke is weak and easy to deform.
It has different shapes, compared to the general anchors, such as single claw anchor, screw anchor and mushroom anchor. It often has special applications, used in a permanent mooring such as a floating tube, a buoy, a lightboat, the floating dock and a floating wharf.
High Performance Marine Anchor – High Holding Power Anchor
The anchor has a large holding power to weight ratio, so it is called a high holding power anchor. The gripping force is more than two times larger than the ordinary stockless anchor of the same weight. There are Martrosov anchor, Danforth Anchor, Schdringer anchor, Staccato anchor, etc.
A high holding power anchor is classified into a stocked anchor and a stockless anchor. Its general feature is that the anchor fluke is wide and long with deep gnawing soil, good stability
1.Stocked high holding power anchor
The typical kinds of this anchor are the Danforth anchor and Steven anchor.
The anchor head is provided with a stabilizer bar to ensure stability, generally suitable for more soft substrates, with inconvenient storage, so this type of HHP anchor is suitable for engineering ships and small ships.
The anchor is also known as swallow anchor and the anchor fluke is rotated about 30 ° back and forth. The holding power to weight ratio is generally greater than 10, mostly used in engineering vessels.
The anchor has a short and large fluke, and the maximum angle of the anchor fluke can be adjusted by the movable wedge mounted on the anchor rod to accommodate a variety of substrates. The holding power to weight ratio is 17 to 34, widely used as a positioning anchor for oil platforms.
2.Stockless high holding power anchor
The stockless HHP anchor is developed by the stock HHP anchor. It has improved the anchor fluke of the stockless anchor. The typical stockless high holding power anchor is the AC-14 anchor developed by the United Kingdom and the Boer anchor developed by the Netherlands.
The AC-14 anchor is a commonly used anchor. The anchor fluke can have an allowable deviation for the left and right corner within 1 degree. AC-14 anchor is a casting anchor with black painting surface treatment. It has the advantages of stable structure, thick and wide flukes, adaptability to various substrates, rapid gnawing, high gripping stability with holding power to weight ratio ranges from 12 to 14. So it is commonly used as the bow anchor in the large ship or ro-ro ship.
The Boer anchor also called TW type anchor or N type anchor. It has smooth and sharp anchor flukes, with the advantages of adapting to a variety of substrates, high stability, convenience for dropping and weighing anchor, easy for storage, suitable for the bow anchor in a large ship and positioning anchor in a workship.
Marine anchor has a high performance for boat berthing stably. The high holding power anchors, which include Danforth anchor, AC-14 anchor, TW type anchor, etc, have the advantages of great gripping force, deep gnawing, high stability, commonly used in a wide variety of ships.