Wave Wrap And Angle Anchoring

By Tom Neale

There are certain times when your perfect anchorage unexpectedly turns into something far less than perfect. Your boat starts rolling from side to side. Sometimes it's pronounced, sometimes it's barely noticeable, but it's usually unpleasant or at least annoying. You check the wind direction and see that the bow is pointed right into the wind. So there should be no problem. But you check the surface of the water and see swells, perhaps large, perhaps hardly noticeable, coming at your beam. As they reach your beam they're definitely noticeable in effect if not in appearance. Here's why this may happen and how many experienced people deal with it. This tactic can apply to many different kinds of boating and boats. It may be helpful to you if you're spending a few hours on Sunday afternoon at anchor in your small boat or if you're hanging out in a large cruising boat.

Wave Wrap Big MajorsWave Wrap Big Majors

First, it helps to understand the nature of the problem.

Wave Wrap

Waves coming from open water can actually wrap around an island or what seems to be a great protective point of land. Often that protective barrier may even be very long, giving you a great feeling of security as you snug up far away from open water. But this feeling of security may be false. The result is that even though you're swinging to the wind, the waves are coming at you from the side. They've changed direction from the direction they were traveling out in the open. Several things may cause this.

The contours of the bottom and the shore can play a role. In theory, if waves are traveling in a somewhat straight line and they run into an island or long point of land they should continue to travel in that straight line outside of the protection of that obstruction but stop inside it. In actuality they seldom do. Water is fluid, as we know, and as the wave sweeps past the protruding point some of it wraps around that point, coming inside the protected area.

There are other features that can exacerbate the problem. Wave wrap may particularly be a problem if the open water on the outside is deeper than the relative shallowness of your "protected" harbor and its surroundings. For example: big swells in deep water may hump up as they reach shallow water and this rising may flood around so-called protective land barriers, essentially as waves. Many a boat has been trapped by this phenomenon in bad storms, sometimes with dire consequences. During a wave wrap, your boat may be hanging to the wind, which is probably blowing off the island or point. But the waves may be hitting the boat on the beam, sometimes creating horrible rolling.

Angle Anchoring

People sometimes handle wrap by what I refer to as "angle anchoring," or "cocking your boat." You first set your anchor securely, in good holding bottom, giving perhaps extra scope. If you don't have an all chain rode (something which I prefer) you deploy as much chain as practical between your anchor and the rode leading to your bow roller. You're going to be stressing that gear more than usual, and you're going to be giving extra challenge to its ability to hold in the bottom. Next, you run an "adjusting line" (for lack of a better term) from a strong amidships cleat or even from your stern, up to a point on the anchor line below the bow. It will be important for that cleat to be strong with proper backing and have a good fair lead forward. An amidships cleat should be able to withstand the stress of warping onto or off a dock and thus should be robust, but check it out. Usually an all chain anchor rode is better for this because it's easier to secure the "adjusting line" into it. In this case all you need is a good chain hook at the end of the "adjusting line." If you must connect that "adjusting line" to a rope rode you have to use one of several types of knots in the anchor rode. These may weaken the anchor rode and could become "stuck" if you have too much wind.

Typically the boater will usually attach the "adjusting line" to his anchor rode first, just below the roller. Of course, you have to do this by making the attachment close to the prow so that you can reach it. Then you let out more of the anchor rode so that the "adjusting line" attachment is somewhere down the rode, perhaps even under water. To a certain extent, the effectiveness of your "adjusting line" increases as the point of its attachment to the anchor rode is farther away from the bow. This gives you a broader more flexible triangle. (The three sides of the triangle are your "adjusting line, your rode and your boat.) Then you run the "adjusting line" back outside your stanchions (making sure of a fair lead) to the amidships or aft cleat and experiment with that line, pulling it in or letting it out to get the right angle. You also may want to pull in or let out the anchor rode to help achieve this result. Sometimes a lot of experimentation is needed to find the right length of the anchor rode, the right cleat on your boat, and the right length for the "adjusting line" in order to comfortably cock your boat so that its bow faces into the swell instead of the wind. Also, as wind and waves veer, as they will, you may need to re-cock your boat by lengthening or shortening the "adjusting line."

Possible Problems

As with most "neat tricks" at sea, there are usually potential problems. As mentioned above, these include greater strain on your cleats and more pull on the anchor (perhaps pulling it out). Also you must think it through for your boat and circumstances and plan carefully because the extra stress and activities can lead to safety issues. Start practicing this in rather benign conditions. Another serious problem can be the difficulty of quickly getting away from your anchorage if you're dragging or if another boat is dragging down on you. You may even have to cut the "adjusting line" and sacrifice it. Be sure that it doesn't get into your prop if you do and remember that you may have to disengage it from the anchor rode as you retrieve that rode. If your anchor rode is all chain and you've used a chain hook, this shouldn't be a problem. Chain hooks are inexpensive. But usually, if there's need for hurry or if it's dark, people will simply uncleat the "adjusting line", bring it aboard and leave it attached to the anchor rode, having it come back parallel to the rode, to a spare cleat on the bow. Or, if there is need to retrieve the anchor rode in a hurry and it's tied to the rode, it may make sense to just pull the "adjusting line" in, alongside and with the rode.

This is not the way to ride out a storm, high winds or any extreme conditions. It's simply a way of dealing with a fair weather wrap to make yourself more comfortable. I've used it and I've seen others use it for days at a time, but only when it's safe and convenient.

Good anchorages are getting harder to find these days. But you can still find them and, when you do, a little understanding of the overall situation will help you to enjoy them better. It's always good to know your anchorage, get local knowledge, or at least try to figure out how the waves might behave. 

Tom Neale, a technical and lifestyle writer and liveaboard cruiser. Read more of Tom Neale's articles here.

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— Published: August 2016


Tom's Tips About Ricochets

  • Sometimes the wave wrap will set up a ricochet. This can be miserable and angle anchoring probably isn't going to help.
  • The waves will march into the anchorage (either by wrapping or maybe directly), hit land across the harbor or a shallow channel edge, and bounce off.
  • Then they roll back, to meet the new ones coming in.
  • This can be like a washing machine and nothing is going to make you comfortable, especially if you're caught near the middle.
  • You can't necessarily tell that this is going to happen when you come in to that great anchorage.
  • Ricocheting waves can depend on slight wind shifts and even changes in the tide so there may be no problem with ricochet when you enter the anchorage but plenty of problem later.
  • If you see a steep shore or channel edge opposite from where the waves will enter, you should be forewarned.

See www.tomneale.com

 

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