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Anchor Selection Criteria
Because the anchor is the key to effective mooring or anchoring, it is essential to know what to expect from various types. Any anchor's performance is dependent first upon its ability to bite into the bottom through the plowing effect of its flukes and secondly upon its ability to maintain a continuous resistance to drag once it is implanted in the bottom.
Therefore, the optimum design of an anchor is influenced primarily by the specific composition of the ocean floor, which is generally categorized into three groups: mud, sand, and rock or marl. Mud varies the most in consistency and offers little resistance to dragging forces. Sand is almost ideally consistent, and anchors specifically designed for sand bottoms reach excellent holding efficiency. On the other hand, rock or marl is a very poor holding ground, where an anchor's dead weight is its only asset.
An anchor's efficiency is expressed in holding-power ratio, that is, the holding force per anchor weight. The proof test involves applying a static load to the assembled anchor to test its structural design and material properties as related to the holding force.
The holding power of an anchor is affected greatly by the angle of its flukes. In order for the flukes to enter the bottom at an angle that will allow the crown or head to penetrate to a depth producing maximum efficiency, the angle of the fluke to the shaft should approximate 50 degrees in mud bottoms and 30 degrees in sand.
Anchor holding-power is also dependent upon other factors: bottom conditions, duration of drag, the ratio between the length of the mooring line and water depth and dampening effect of the catenary, to name a few.
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Stockless
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Snug-Stowing
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LWT
(Lightweight)
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Danforth
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Stato
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Moorfast
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Boss
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Recommended Applications
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Offshore Rig Mooring
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X
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X
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X
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X
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X
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Supply/Support Vessels
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X
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X
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Pipelay Barges
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X
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X
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Fixed Mooring
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X
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X
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X
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X
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X
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Commercial Ships
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X
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X
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Tugboats
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X
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X
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X
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Supertankers
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X
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Minimum Performance Characteristics
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Mud
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Holding Power Ratio
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3:1
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5:1
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9:1
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9:1
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9:1
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9:1
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32:1
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Depth of Penetration (ft)
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9-10
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17-20
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17-20
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17-20
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17-20
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17-20
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35-40
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Breakout Force Ratio
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2:1
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3:1
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5:1
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5:1
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5:1
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5:1
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6:1
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Fluke-to-Shank Angle (¡ )
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45¡
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43¡
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50¡
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30¡
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50¡
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50¡
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50¡
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Sand
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Holding Power Ratio
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7:1
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14:1
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20:1
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20:1
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20:1
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20:1
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25:1
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Depth of Penetration (ft)
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3
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6-8
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6-8
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6-8
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6-8
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6-8
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10-15
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Breakout Force Ratio
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2.5:1
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6:1
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8:1
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8:1
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8:1
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8:1
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12:1
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Fluke-to-Shank Angle (¡ )
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45¡
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43¡
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30¡
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30¡
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34¡
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34¡
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34¡
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Optional Swivel Shackle
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X
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X
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X
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X
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Padeye for Pendant Buoy Line
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X
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X
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X
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X
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X
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- These recommendations are based on past usage practice. Deviations are acceptable.
- These are minimum values only; actual bottom conditions could increase holding power considerably.
- Swivel shackles can be used to replace anchor shackle, anchor connecting link, and swivel.
¨Baldt, Snug Stowing, LWT, Stato and Moorfast are registered trademarks of Baldt Incorporated.
Danforth is a registered trademark of Rule Industries, Inc.
©1986 Baldt Incorporated. All rights reserved.
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Anchors 
