How to Choose and Use the Right Anchor
by Ron Ballanti
Proper anchoring is one of the least understood areas of seamanship. After all, how much could there be to it? You just throw the anchor overboard, wait until it hits bottom and tie it off, right?
Anyone who has spent enough time on private boats has seen the wide variety of problems this kind of simplistic attitude can foster. Just like anything else, proper boat anchoring requires the right equipment, careful thought and practice. Considering the possible consequences of insufficient anchoring (drifting ashore during the night, colliding with other boats), it's definitely worth the effort.
Choosing the Proper Equipment
The first step is selecting the proper ground tackle (the collective term for anchor, line, chain, shackles and swivels) for your vessel and your style of boating. No one anchor does everything perfectly. Each of the popular styles has its own benefits and drawbacks, and each performs best under certain conditions.
Most popular styles are variations of the Danforth, the CQR/Plow anchor and the Bruce anchor. The Kedge anchor – its familiar shape recognizable from insignias, tattoos and large ships – actually has limited applications for West Coast recreational boats.The Danforth – easily identified by its two long, sharp pivoting flukes and long shank – is a good choice for many small to medium-sized boats. It's relatively light and easy to store. The Danforth also digs well into sand and mud bottoms, yet releases easily when pulled from a different direction. A round rod across the crown end prevents the anchor from rotating on the bottom as the flukes bury themselves.
The Danforth's flukes pivot so the shank can be pulled at a more vertical angler, facilitating easier release. It's ideal for fishing, which often requires frequent pulling and re-setting of the anchor in order to move to a new spot or reposition the boat. If you frequently overnight or travel to unfamiliar waters, however, you may want to choose one of the other styles, which hold better in changing conditions.
The CQR or plow anchor features a single plow-shaped fluke that pivots at the end of the shank. This design works well on a variety of bottoms. The shank pivots from side to side, while remaining parallel to the fluke (in the opposite direction of the Danforth). This means the plow anchor can remain buried during moderate changes in wind or current direction. The design also allows for a relatively easy release when the anchor is pulled vertically.
The Bruce anchor was originally designed for offshore gas and oil drilling rigs. The scaled down version of this design is gaining popularity with boaters. This design allows this anchor to hold fast, (even if the direction of pull changes 360 degrees), yet it still comes loose when pulled vertically.
Be sure to select an anchoring system that matches your boat's length, displacement and windage, as well as the type of boating you do. Only top-quality braided nylon anchor line should be used to ensure strength, elasticity and durability. It's also important that the size and length of the anchor line is appropriate for your vessel and specific requirements. Small to medium-sized boats should also use a section (approx. ¾ to one boat length) of galvanized steel chain between the line and the anchor. The weight of the chain lowers the angle of pull and helps the anchor set more effectively. Large vessels equipped with power winches can use all chain, but this adds considerably to weight and cost.
Setting the Anchor
Without a doubt, the most common mistake made when setting anchor is not using sufficient scope. When this occurs, the anchor is much more likely to drag, break free or get fouled. To get a solid hold and dig into the bottom, you need to make the angle of pull as low as possible. The U.S. Power Squadron Course Book uses this analogy: Bury a pickaxe into the soft dirt. Lift up vertically on the handle, and it breaks free relatively easy. Pull at an angle low to the ground, however, and pick actually digs deeper in the soil.
This is the effect of scope – a number that denotes the ratio of anchor line length to the depth of the water. To keep the angle of pull as low as possible, it's necessary to pay out a healthy amount of anchor line. A scope of 5:1 is a good working minimum for normal conditions. If you are anchoring in stormy weather, you should double this amount. What does this mean in practical terms? For example, if you want to anchor in 20 feet of water, you would first need to accurately gauge the speed and direction of wind or current (whichever is stronger), then position your boat well "uphill" from your desired position. Then the captain would use reverse gear to "scope back" approximately 130 feet of anchor line. This accounts for the 5:1 ratio, including an estimated distance of six feet between the surface of the water and the anchor roller. Most dealers offer inexpensive anchor line "marker tabs," that allow you to know how much line you have out.
No matter which style of anchor you choose, it's important to take extra care when anchoring overnight. Remember that winds or currents can shift full-circle, so be sure to position your vessel far enough away from rocks or other vessels. In addition to regular visual checks, use the audible anchor alarm feature on your GPS unit, which will alert you to any major movement.
About the Author: Ron Ballanti is a veteran outdoor writer, boater and angler. He also owns and operates Strike Zone Communications, a marine public relations and marketing agency based in Northridge, California (Phone: 818-349-4608. Fax: 818-709-5524. E-mail: email@example.com).