Does Your Anchorage Rate?

Look for these elements before dropping the hook
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Successful anchoring depends not only on good ground tackle but also the anchorage itself. Most folks have a fair idea of what makes a good anchorage. You need shelter from the elements and room to swing 360 degrees. But what else?

Bottom type is important. I’ve dragged anchor in flat calm because the hook couldn’t get purchase on the ledges below. A firm clay bottom can also be difficult for the anchor to bite into. Mud is usually good, but if it’s too thin, like a loose slurry, the flukes will slip through the substrate like a fork through chowder. Kelp beds are notorious for poor holding, but there are exceptions. One time, we were anchored in kelp on the coast of Tasmania when a sudden blow came up, yet the anchor refused to drag. Instead, 300 feet of chain got yanked out of the locker and we had to dive for it later. I have had mixed results with shell-sand blends. It just depends upon the consistency and the conditions.

Depth is another factor in choosing an anchorage because scope—the ratio of water depth to length of rode—is a key. An anchorage that is too deep will not work, even if it is well protected with good holding. A general rule for scope is 5:1, or 50 feet of rode for every 10 feet of depth, plus the distance from the waterline to the chock.

Tide presents several considerations, especially if the range is significant. Always calculate scope based on the depth at high tide. With a depth of 15 feet at low tide, 75 feet of rode will provide a 5:1 scope. But if there is a 10-foot tidal range, scope will be only 3:1 at high water. You’ll need 125 feet of rode to maintain 5:1 at the top of the tide. A falling tide improves scope, but it also increases the diameter of your swinging circle. Objects that were a comfortable distance away at high tide may be a source of concern at low water. In a crowded anchorage, all other boats will be similarly affected, a reality that can bring you closer than you want to a neighboring boat. Gauge this before dropping the hook.

In places where a bar, ledge or reef provide some protection, consider how high tide may reduce that protection. If sea or swell can lap over or wrap around into the anchorage at high water, it will be very uncomfortable. And if the bow begins to plunge excessively from sea or swell, it can exert enough force to yank the flukes out of the bottom.

Try to avoid powerful currents. Not only do they magnify the strain on the anchor, but when wind and current do not agree you may end up betwixt the two, with the boat lying beam to the wind. This will put a sideways strain on the anchor and cause you to roll uncomfortably. 

Perhaps the most important part of appraising an anchorage is assessing wind strength and direction. Think about how it could change in the hours ahead. You may  start out in a snug little haven at cocktail hour, and then find yourself on deck in the middle of the night, swearing in your underwear in a driving rain as your stern swings disturbingly close to an exposed lee shore.

Once you have identified a suitable anchorage, the next step is to determine where to place the anchor. You can enter coordinates into a chartplotter and steam toward them, but, being old school, I like to establish bearings or natural ranges that I can use to monitor the approach and verify my arrival at the chosen position. Approach head-to-wind, reducing speed and then coasting with the engine out of gear. When you arrive at your chosen spot, put the engine astern. Wait until you have gathered sternway, then let go the anchor. Sternway ensures that the rode won’t pile up on the anchor, entangling it and preventing the flukes from biting into the bottom. How will you know when you have sternway? Look for prop wash moving toward the bow, or monitor a fixed object ashore that is more or less on your beam. As the vessel backs down, pay out the rode until you have achieved the desired scope.

Vessels don’t always back straight down. Often, the bow pays off, leaving you beam-to the breeze. This is not necessarily a problem; you just have to be patient while the vessel settles back and stretches out the rode. Applying some light, momentary tension on the rode as it runs out can help you keep the bow into the wind, but don’t overdo it, as that can interfere with the anchor setting.

Obviously, backing down too aggressively won’t give the anchor a fair chance to set. Once the hook appears to bite, you can always increase RPMs to satisfy yourself that the flukes are dug in well. The best way to visually determine if the anchor is holding is to monitor a fixed object on the beam. If there is no relative motion, your anchor is set. If an object on the beam appears to be trending forward, you’re not done yet.

Sometimes in a busy anchorage, people will tether a buoy to the anchor before letting go. The buoy shows other boaters where your anchor is so they can avoid dropping theirs too close to yours. Also, if another vessel starts to drag down onto you, the buoy makes it easier to assess the situation so you can act early to prevent entanglement. To buoy the anchor, run a line outboard of everything—stanchions, lifeline, rigging—and tie it to the anchor. Fasten something buoyant to the other end (a fender, jug or buoy) and make sure the line is long enough to reach the surface at high tide. Double check for potential entanglements, including people, so the line and buoy will run free when you let go.

Captain Daniel S Parrott photo

Capt. Daniel S. Parrott

A different reason for buoying an anchor relates to the possibility of it jamming in the bottom. Some bottom types, such as rocks or boulders, are especially prone to this. A buoy rigged for this purpose is known as a tripping line. For a tripping line to be effective, it must be fastened to the crown of the anchor. Some anchors may be fitted with an eye or ring at the crown for this purpose. If, upon shortening up the rode, the anchor doesn’t break out, apply tension to the tripping line. Instead of fighting against the flukes, the tripping line will enable you to draw them out backward. But remember, if you want to avail yourself of a tripping line, you have to think of it before you let go the anchor.

Last, it’s important to remember that proper anchoring etiquette puts the onus on new arrivals to stay clear of those who are already in the anchorage. Sometimes, someone simply anchors too close to you, presenting you with a problem not of your own making. Try not to be that person.

This article originally appeared in the March 2019 issue.