Anchoring - Introduction & Selection

Introduction

An oversight that is easily made when purchasing a boat, is the importance of selecting a suitable and reliable anchor. Many of us place more emphasis in how we choose a boat, a boat's motor and the design and shape of the hull, which is also as important. One thing many people forget to consider, however, is the anchor. There are several basic types of anchors that are available for use. Each one is designed for a specific purpose.

Anchors work in several ways. Some dig into the seabed, some silt in, and others are heavy enough to simply sit on the seabed. Some anchors hold extremely well in sand or mud, others fare better in shale or rocky bottoms. Some anchors never touch the seabed while others are permanently embedded.

When anchoring, remember that the best holding bottoms are mixtures of mud and sand, mud and clay and firm mud and sand. Gravel or hard sand bottoms will hold well if your specific anchor can penetrate them. Loose sand or gravel or soft mud should be avoided. Don't anchor in deep water, or you'll have to use too much line for the proper scope, which will allow too wide a swing for the boat.

Also, it is a good idea to carry more than one anchor on your vessel. Two anchors can come in handy if you loose one, or in heavy current or in windy situations such as a storm.

When you purchase an anchor, make sure you get the right type for the bottom conditions where you go boating. Most boating stores can help you decide on the type of anchor, but don't be cheap, buy at least 1 good, heavy anchor for each type of bottom you expect to have to anchor on. The most common anchor used in SA waters is by far the Danforth/Fortress Anchor, being one of the best anchors for holding in many different types of bottom compositions.

Should you ever be in a position where you lose your main anchor, to make a temporary anchor, tie some rope to a bucket, and the drag of the bucket in the water will slow you down to a degree, buying you some time.

Another alternative is to use a 6' x 4' tarpaulin, tie each corner to a rope, and the drag generated by the surface area of the tarp in the water will definitely slow you down. This scenario equates to using a make shift sea anchor.

Anchor Selection

Anchor selection should be based on the size and type of your boat and the condition of the bottom where you do most of your boating.

Anchors can be broken down into three general families; the lunch hook, the working anchor and the storm anchor. A lunch hook is an exceptionally light anchor that is set for short daytime stops when crews stays aboard. The working anchor is used for standard overnight anchoring.

It has been suggested that cruising boats should carry two working anchors, one for hard bottoms and one for soft bottoms. A storm anchor is used in heavy weather and can be of any type, as long as it is very heavy. A primary anchor can be set along with a storm anchor on a separate rode if conditions warrant it.

Anchors can be further categorized into burying and nonburying types. Nonburying anchors work by hooking onto rock or thick grass and weeds, and must rehook if the boat swings. Burying anchors, such as the Plow, Danforth/Fortress and Bruce, dig deep into soft bottoms and are designed to hold if the boat changes position. They are usually lighter than nonburying anchors because they dig into the seabed.

Some anchors have a stock to orient the flukes so the anchor will dig in properly. The stock also can keep the anchor from breaking free without resetting if the boat changes position. They should not be used as a working anchor because they must be heavy to be effective (around 25 kg) and usually must be taken apart to stow, but they can be used as a storm anchor.

Anchors, such as the Fortress or Danforth, have a stock at the bottom of the anchor for easier stowage and collapsible stock anchors allow the stock to be folded parallel to the shank.

The Danforth or Fortress, is a burying anchor with wide sharp flukes and a stock. It holds very well under high loads in mud and sand but may be difficult to set in clay, grass, weeds, rock or shell bottoms. It requires more scope than other anchors in order to be effective, and can be stored flat on deck.

Stockless anchors were developed to allow the hook to be stowed in a bow roller. These popular anchors include the Bruce, CQR or Plow.

Fishing

If you are fishing, you don't have to use these techniques since you are constantly there watching, but you might choose to in order to fix your position over a good fishing spot. The best thing to do when anchoring in a slight or choppy swell is to increase the angle as much as possible between the boat, anchor line and anchor, ie let as much rode out as you can. This will cause the anchor to grab the bottom better, and secondly, reduce the effects of sea swell against the boat due to more allowable movement of the boat around the anchor itself.

With today's advanced materials and low cost, there really is no reason that a modern recreational vessel shouldn't be equipped with at least one anchor and adequate rode (anchor line). The anchor should be the right size for the boat, and the rode should be appropriate to the depth of water in which the vessel usually operates. In general terms, the rode should be at least seven times as long as the water is deep, measured from the deck of the boat to the bottom. In heavy weather, extend the rode to at least 10 times the depth of the water.

So, if you expect to hold your boat securely in thirty feet of water, you should expect to pay out at least 210 feet of anchor line. A length of chain between the anchor and the line can give you added holding power. The chain will keep the flukes low where the anchor can set more easily, and won't be victim to abrasion on a rocky or sandy bottom.

You always should lower the anchor slowly over the bow. Never throw the anchor. Make sure one end of the anchor line is connected to the anchor, and the other end secured to something other than your wrist or foot.

It's best to anchor from the bow. This will almost guarantee that the bow of the boat will stay headed into the wind and waves. Anchoring from the stern can create a problem, especially during rough seas, where waves can come over the transom of the boat, allowing for the potential of your boat sinking.

If you're anchoring overnight, or leaving the vessel temporarily without a watch, be sure and check your boat's "swing" radius before settling in. If the wind changes, you don't want your boat swinging into someone else's mooring area or shore. Also, to check whether your anchor is set, visually establish a relative sighting between something on your boat, like a cleat, and some landmark on shore, if possible. Then check every five or ten minutes to see if the landmark has moved relative to your onboard marker.

By checking it frequently for the first half-hour or so, you'll soon know whether any movement is because of normal boat swing, or because you're adrift.