Anchor Design for Soft Mud

Posted by Darrell Nicholson at 10:40AM - Comments: (16)

Photo by Jonathan Neeves
Photo by Jonathan Neeves

The Ultra anchor is ballasted in the bottom and has a hollow shank, promoting a "toe-down" position when setting.

Soft mud seabeds are relatively common, particularly in shallow estuaries and at the mouths of large rivers. In many cases, the soft mud gives way to clay or harder, packed sand, so that if an anchor penetrates deep enough, it finally has something to bite. But in other cases, the mud is very soft and deep. Such areas are avoided for long-term anchoring—and consequently, anchor testing—because of the difficulty in finding good holding. As a result, most anchors are optimized for harder bottoms. One interesting implication from recent anchor tests in soft mud is that some newer design elements engendered by this logical bias toward hard-sand bottoms might actually hinder anchor performance in soft mud. For example, one of the observations from our 2006 test of anchors in soft bottoms was that anchors equipped with roll bars performed far below our expectations in soft bottoms.

Practical Sailor carried out its own series of anchor tests in a mud bottom in 2006 (see April 2006 and October 2006 issues), and those tests bore out a commonly known fact: Danforth-style anchors, which feature flukes that are proportionally larger than other types of anchors of the same mass, tend to hold better than older, plough-style anchors (such as the CQR, or Delta) in soft mud. A well-documented test in Chesapeake Bay carried out by anchor maker Fortress in 2015 yielded similar results.

The troubles faced by roll bar anchors in the Chesapeake Bay test were an eye-opener. The difficulty setting suggests that at least one anchor, the Rocna, might have landed upside down and that the self-righting effect of the roll bar did not work in a soft seabed. The result also suggests that this might be a problem for other concave-type anchors that have roll bars but lack a weighted toe. As further evidence of this, the Manson Supreme, which has a roll bar, but also has a weighted toe, did yield higher holding numbers.

Photo by Evans Starzinger
Photo by Evans Starzinger

The roll-bar anchor Manson Supreme has a weighted toe to help aid in setting.

Most anchors rely on a firm substrate to self-right, and this seems especially true for anchors with roll bars. It is logical that a roll bar would be little or no help in a bottom that is too soft to roll on—in which case, a weighted toe would come in handy. However, the Mantus, which has a roll bar and lacks a weighted toe, seemed to defy this logic. Compared to both the Rocna and Manson, it fared pretty well in the Chesapeake mud.

As we pondered this puzzle, we were reminded that in our own tests, the hydrodynamic effect of water flowing past the flukes of the Mantus seemed to help it self-right. The Mantus’s tendency to self-right during deployment was most obvious in our tests when the boat was moving in reverse—the direction of the set. We suspect that the protocol used during the Chesapeake Bay tests—with the test boat Rachel Carson shifting to reverse once the 20 feet of chain was deployed—could have promoted this self-righting.

Regardless, the reliability of the Mantus and others of its ilk should be viewed with caution in soft mud (as in fact should almost any anchor.) There is evidence that the weighted convex and concave anchors—Delta, CQR, and Spade—also self-righted, but the amount of holding power for all of these anchors was inadequate for anything but a lunch hook.

Photo by Drew Frye
Photo by Drew Frye

PS Technical Editor Drew Frye loads anchors for soft-mud tests using two anchors from a single rode (tandem anchoring).

Based on its better holding-power numbers in the Chesapeake, it is obvious that the Ultra anchor, a weighted concave anchor without a roll bar, self-righted. Its holding power was 20-percent greater than similar designs—the Boss, Supreme, and Mantus—but, again, none of these anchors, which have fared well in our Practical Sailor anchor tests, generated reassuring numbers in soft mud.

As a result, Practical Sailor has been exploring a number of other anchoring options for very soft mud, a substrate that presents problems for every type of anchor, to some degree. Most of our experiments have involved using more than one anchor, but our general advice remains the same as it has been for years: Whenever possible seek the best available holding, and avoid very soft bottoms. We’d be interested in other experiences in soft bottoms.

We’ll revisit anchor holding power in an upcoming issue of Practical Sailor this spring. In the meantime, those in the market for a new anchor can get a comprehensive look at the art of anchoring and the related equipment in our four-volume ebook “Anchors",” available for download online, which includes articles on selecting articles in various bottoms, and an evaluation of various accessories, including rode, swivels, and snubbers.  

Comments (16)

So far we have had shockingly good results from the 55 pound Delta that came with our on our 30k+ pound 2004 Beneteau 50. That said have recently upgraded & added a 73 pound Rocna (barless) Vulcan in addition.
Couple years back we were a stake boat for the Americas cup race in New York Harbor. We set the Delta in the north river off lower Manhattan in about 3 1/2 - 4 kts of current and in about 50 some odd feet of water with quite a bit of wave action and 10-15 kts of breeze. Unfortunately all we had onboard was 175 feet of 3/8 chain so we put out every inch we could and also used our bridal. But even so... over multiple days with multiple sets due to relocating the racing area ( so no we were not hooked onto anything solid) we never budged an inch with nothing but pure muck down below.

Posted by: CaptainKornchex | February 17, 2019 10:33 AM    Report this comment

How about the Supermax?

Posted by: Joe Pica | January 28, 2019 4:14 PM    Report this comment

How about test including the venerable Super Max which is now being manufactured again in the US using high test steel. I've known several long term cruisers that have cruised with them for many years and swear by them rather than at them.

Posted by: Joe Pica | January 28, 2019 4:13 PM    Report this comment

How about test including the venerable Super Max which is now being manufactured again in the US using high test steel. I've known several long term cruisers that have cruised with them for many years and swear by them rather than at them.

Posted by: Joe Pica | January 28, 2019 4:12 PM    Report this comment

I have the fortress and found it lacking in weed. It would not hold and when retrieved it had so much weed my 1000 pd. Winch could not lift it. So I researched and found the Mantis. I could not afford their price of $3k for a stainless storm anchor so I made my own version of a combo of the Mantis & Rocna for $650 using 304 stainless stick welded with a lead filled tip. It sets instantly in all conditions.

Posted by: Diamondgirl | January 27, 2019 12:52 PM    Report this comment

I have the fortress and found it lacking in weed. It would not hold and when retrieved it had so much weed my 1000 pd. Winch could not lift it. So I researched and found the Mantis. I could not afford their price of $3k for a stainless storm anchor so I made my own version of a combo of the Mantis & Rocna for $650 using 304 stainless stick welded with a lead filled tip. It sets instantly in all conditions.

Posted by: Diamondgirl | January 27, 2019 12:52 PM    Report this comment

I use an oversized Manson Supreme on my Pacific Seacraft Crealock34. The tables recommended a 35#; I use a 45# as my working anchor. So far completing more than half of the Great Loop, that's been a great anchor. Now that I'm here in the Florida Keys with the soft sticky mud that's the predominant bottom it's still performing flawlessly. Highly recommended as far as I am concerned.

Posted by: Boatbum | January 27, 2019 9:28 AM    Report this comment

Back in 2010, in the muck of the Las Brisas acnchrage of Panama City, we discovered what is mentioned here, that at least some of the "roll over bar" anchors did not roll over in the muck. My CQR, and others, were successfully set by backing them SLOWLY at about 5:1 scope, all chain. They would completely dissappear under the muck. I am sure the CQR would not have nearly the ultimate holding power of a danforth or other anchors with larger fluke area.

I suggest if you have trouble setting a CQR, is that you may be backing too fast for the point to get a good grip. Also, the "knockoffs" do not seem to work at all well. We use it as our common anchor, but shift to either an aluminum french plow, or Fortress FX55 if holding power is likely an issue.

Posted by: Capt Chetco | January 26, 2019 10:29 AM    Report this comment

Back in 2010, in the muck of the Las Brisas acnchrage of Panama City, we discovered what is mentioned here, that at least some of the "roll over bar" anchors did not roll over in the muck. My CQR, and others, were successfully set by backing them SLOWLY at about 5:1 scope, all chain. They would completely dissappear under the muck. I am sure the CQR would not have nearly the ultimate holding power of a danforth or other anchors with larger fluke area.

I suggest if you have trouble setting a CQR, is that you may be backing too fast for the point to get a good grip. Also, the "knockoffs" do not seem to work at all well. We use it as our common anchor, but shift to either an aluminum french plow, or Fortress FX55 if holding power is likely an issue.

Posted by: Capt Chetco | January 26, 2019 10:29 AM    Report this comment

Back in 2010, in the muck of the Las Brisas acnchrage of Panama City, we discovered what is mentioned here, that at least some of the "roll over bar" anchors did not roll over in the muck. My CQR, and others, were successfully set by backing them SLOWLY at about 5:1 scope, all chain. They would completely dissappear under the muck. I am sure the CQR would not have nearly the ultimate holding power of a danforth or other anchors with larger fluke area.

I suggest if you have trouble setting a CQR, is that you may be backing too fast for the point to get a good grip. Also, the "knockoffs" do not seem to work at all well. We use it as our common anchor, but shift to either an aluminum french plow, or Fortress FX55 if holding power is likely an issue.

Posted by: Capt Chetco | January 26, 2019 10:29 AM    Report this comment

Best anchor depends on the bottom you are trying to grab onto. I have a 40 kg Rocna and a 20 kg CQR. On hard sand, I've seen the CQR fail to set; it merely lays on its side and slides along.

Posted by: GaryB | January 24, 2019 5:38 PM    Report this comment

I know anchor performance and testing is extraordinarily complex and difficult. My personal experience and that of my friends doesn't really match much of the results you present here, or in other tests that have been published. We sail primarily the Chesapeake. I've cruised it from headwaters to ocean for 30 years on two different boats, and anchored many hundreds of times in virtually all of the major tributaries. Both boats carried an original Bruce. In all of those years, through some remarkable winds, we have never (knock on wood) drug. The current boat is 43', displacement approx 25,000 lbs, high topsides production sailboat. We have anchored her for 20 years with a 66 lb Bruce and all chain rode. It always sets immediately, with the final set at 2500 rpm in reverse. One notable anecdote, with two similar boats rafted to us on my anchor, a t-storm gave us swirling 60+ knot winds for about 40 minutes. We never moved, but watched boats all around us dragging. Another observation, we've many times watched a boat drag in the anchorage, and when they pulled up their anchor, it was a Danforth in almost every case, otherwise a plow. Finally, many of my friends on large sailboats have switched to Rocna for the Bay and absolutely swear by them. My personal experiences may not conform to logic or your testing, but it has convinced me. By the way, when we get to Florida and Bahamas, we switch to our Spade.

Posted by: CapnR | January 24, 2019 2:15 PM    Report this comment

The west end of Lake Erie has a lot of mud and a good old Danforth or Danforth clone does very well. I buried one so deep that it took about an hour to retreive it. I was very close to abandoning it. If anything, the Danforth might work too well in western Lake Erie. With cheap Danforth clones available, why use anything else in mud?

Posted by: Dave9111 | January 24, 2019 10:44 AM    Report this comment

I kept my 42' sloop Prestissimo at Bath Harbor Marine in Bath, North Carolina. The cove is all soft mud! Before hurricanes Paul, the owner, takes his motor boat out to set anchors for everyone. We are instructed to purchase Fortress anchors and equip them with 10' of cable before the chain and then nylon rode. The purpose is that the Fortress with the cable will cut through the mud and bury itself way down deep in the mud where it holds securely. If the chain is connected to the anchor it prevents the Fortress from burying as deeply. After the hurricane he retrieves the anchors for us and we wash off the mud. This has worked for many seasons.

Posted by: JHuberman | January 24, 2019 10:13 AM    Report this comment

No mention of the claw-type anchor. Seems these would set well in soft bottoms, though perhaps not as well as the fluke-type.

Posted by: pgnewt | January 24, 2019 10:02 AM    Report this comment

Soft goo, big flukes. Danforth light weights seem to fare best. My experience: my 45# CQR has yet to fail me in any anchoring. I carry a Northill, several Danforths, and a fisherman but that CQR is my first and best bet in spite of testing by others.
My boat, Nimue is a 45 foot wood S&S, 36,000 displacement, deep keel. We lived at anchor two years in Baja.

Posted by: SailorJim | January 24, 2019 9:59 AM    Report this comment

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