Small Versus Large Anchors

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The consensus among anchor makers (Fortress, Bruce, Manson, Mantus) is that holding power in soft bottoms increases in approximate proportion with anchor mass; exponents range from 0.92 to 1.0. While there are differences between models and manufacturers, a 35-pound Mantus should hold roughly 18 times more than a 2-pound Mantus, and a Fortress FX-16 should hold four times more than a Guardian G5.

anchors

If we compare our soft mud 2.5-pound Mantus holding result (35 pounds) with the 45-pound Mantus result (750 pounds), the scale-up error is about 20 percent. The same is true for the Guardian/Fortress comparison and the Claw comparison: about 20-percent scale-up error. The drag-in distance to full holding was proportional to the anchors physical size, a trend supported by U.S. Navy testing; Anchors tested at Solomons Island took 30 to 40 feet to develop full hold, while the small anchors took 4 to 10 feet. These are averages; variations between runs were often 50 percent or more, often due to trash in the mud.

Overall, the burying behavior, turning behavior, and relative holding power of the pint-sized anchors in consistent sand and soft mud is consistently proportional to full-size anchors. In other bottoms, especially those that are hard to penetrate, the results are less comparable.

Darrell Nicholson
Darrell Nicholson is editor emeritus of Practical Sailor. He is a longtime liveaboard sailor and has logged tens of thousands of miles in three oceans. A winner of dozens of writing awards in disparate genres, he currently edits Marine Electronics Journal for the National Marine Electronics Association. He holds a U.S. Coast Guard 100-ton Master license and sails his S&S-designed Yankee 30, Opal, out of St. Petersburg, Florida. He can be reached at darrellnicholson.com.