Choosing Your Spot
One of the favorite topics of conversation in a group of cruising sailors is “what type of anchor do you use?”. That is an interesting topic with no right or wrong answer, but what is also very important is “how do you use your anchoring gear?”.
The first step is to decide exactly where to drop the hook once you have arrived at your anchorage. In an unfamiliar anchorage, we think it is important to slowly cruise through the likely looking vacant spots checking the depth gauge, sizing up the spaces between any boats that are already there, and looking for any hazards such as floating buoys, tree stumps, rocks or sandbars. It’s also important to know what wind direction and speed you can expect during your stay and whether or not there is any current flowing through the anchorage. These factors will determine which way your boat will lay relative to the anchor, whether the boat will be affected most by wind or current, and whether the boat will swing in a full circle during the time you are there.
Once you have picked a potential spot, you should be certain that your boat can swing 360° without contacting any obstructions or shoals. You can expect that your neighbors will swing as you do unless they have deployed more than one anchor or are tied to a mooring with a short scope. It is a good idea to ask a neighbor how much scope he is using so you can use a similar amount. That will insure that your boats swing in circles of roughly the same diameter (if you believe his scope to be inadequate, it may be time to look for another spot!). Remember that in light air, a heavy chain rode may not be stretched out. Do not be misled as to where you neighbor’s anchor is located! It might be under his boat.
Professionally installed moorings typically require less scope than an anchored boat. That means that if you anchor behind a boat on a mooring and the wind shifts 180 degrees, your vessel may come into contact with the moored boat since it will swing in a smaller circle. Generally, we do not recommend anchoring close to boats on moorings but with the proliferation of private moorings, it is sometimes unavoidable. Similarly, a boat lying to two anchors may now be held by the second anchor which also limits its swinging circle, possibly causing contact. Of course, you may choose to use two anchors so your boat behaves in a similar fashion.
We believe 4:1 scope is the minimum for all chain rode and 6:1 for mostly rope rode. Scope is the ratio of the rode measured from the waterline (not the bow roller) to the anchor divided by the depth of the water at high tide. Naturally, more scope is recommended as the wind picks up and the conditions deteriorate. We also use the rule of thumb that prescribes 1 lb of anchor weight for 1 foot of boat length as a minimum. More is better if you can handle it.
We recommend dropping your anchor behind and between the two boats in front of your chosen spot. Once you have let out your scope and set your anchor, be sure that any boats behind you are aft of a line across your transom. Do not anchor such that your boat can swing over the anchor of a neighbor. Sometimes, it is hard to judge how far you will swing. Think in terms of boat lengths. For instance, if you are on a forty foot boat and you have 100 feet of scope out, you can estimate the location of your anchor by looking two boats lengths in front of your bow. In an uncrowded anchorage, you can also tie a small float to your anchor with a little more scope than the water depth. The float will indicate the position of your anchor, but be careful it does not get wrapped around your prop and remember that a passing boat could also snag your float, perhaps breaking out your anchor.
You will want to select a location that provides the best protection from any waves or swell entering the anchorage. Anchoring in the lee of the land is no doubt the most comfortable position but watch out for forthcoming wind shifts that might make that land a dangerous lee shore later. For instance if you are expecting a norther which typically come with squalls from the northwest, anchor with that in mind even if that is not the best spot now.
When choosing your spot, you must also be aware of the composition of the bottom. After all, that is what your anchor will be trying to dig into and your security will depend on it. Your chart may give some information about the bottom. Look for symbols meaning sand, mud, coral, soft, sticky, and so on. The sea bottom will determine the preferred anchor to use if you have more than one to choose from. A plow anchor will do well in sand while a danforth type may be better in mud. If you expect the current or wind to change the direction of pull on the anchor, an anchor that resets quickly like a Bruce is preferred.
Once you have chosen your spot, head up into the wind and drop your anchor as the boat is moving slowly backwards with the wind, paying out the rode so that it does not pile up on the anchor. In light air, you can idle the engine in reverse. An anchor cannot dig into the bottom if the chain is tangled up in the flukes. Be sure to “set” the anchor when the rode is paid out. Back down slowly watching to see that the anchor grabs and stops the motion of the boat. Then back down hard (reverse gear at half throttle or more) to make the anchor dig in, using two objects on shore as a range to see that you are not moving. In soft mud, allow the anchor to settle for a while before backing down hard. A rode that jumps under tension is a sure sign of a dragging anchor.
Then review your position to see that you have chosen your spot wisely and that you have plenty of clearance between you and other boats and obstacles. If not, now is the time to up anchor and correct the problem. By carefully choosing your spot, you will be able to have a peaceful, relaxing time on the hook.