All Mud Isn’t Created Equal

By Tom Neale, 12/8/2014

There are at least three problems with any "scientific" anchor test. (1) Anchoring well requires old fashioned seamanship which, in my opinion, is far more complex than that which can be defined by any practical scientific protocol. (2) Anchoring isn't so much a science, as it is an art. And (3) all mud isn't created equal. So while some were surprised at the results of a well planned and executed major anchor test this summer, some weren't.

I'm not a scientist (as is obvious, I am sure) but I've been testing anchors for almost 60 years in every kind of bottom, in hurricanes, in "storms of the century" and even in two tornadoes. Of those 60 years around 35 included anchoring out almost every night. And often I've gone underwater in anchorages during storms to see up-close-and-personal what different anchors are doing. From my experience I've chosen two primary working anchors for my motorsailer. I wouldn't be out without both aboard. They are the Fortress and the original CQR. (I also have a "Herreschoff" type anchor for very special circumstances.) I know that other experienced people have differing views, which I respect. And I should note that, while I've used many anchors, I've hardly tried them all.

Set screws
Good mud coming up on the author's anchor chain.

Never has a Fortress failed to set and to hold for me, except the few times that I've put it down in a bad bottom such as sandstone or thick grass and once when I was forced to anchor in an area where the currents caused constant eddying which, with the high winds, made my boat repeatedly swing around and around the anchor. As sometimes happens with Danforth type anchors the rode got under the stock and pulled the anchor out backwards. But all anchors have their issues and this didn't dissuade me from the Fortress. So, in a recent major anchor test, I should have been very surprised when the Fortress didn't completely measure up to my past experiences with the anchor. But I wasn't.

During August 5-8, 2014 extensive holding testing was done on the Claw, the CQR and Delta by Lewmar, the Danforth HT, the Mantus, the Rocna, the Supreme and Boss by Manson, the Spade, the Ultra and the Fortress. The testing was done by Fortress Anchors. Each anchor was pulled five times during the four day test. The test vessel was the 81 foot aluminum, research vessel "Rachel Carson." She's stationed at Solomons Island, Maryland. She has twin 1,205-horsepower MTU diesels and Hamilton jet drives. She also has a dynamic positioning system (DPS). When activated, its computers keep the boat in a pre-set spot and orientation, utilizing its jets and thruster. The site was the Patuxent River off Solomons.

Efforts to control bottom variables included pulling each anchor along the same bottom area. This was achieved with the vessel's DPS and other sophisticated equipment. After each set of pulls the vessel moved to a different area, to get fresh bottom. They started each pull of each set from essentially the same position (where the anchor was lowered) and pulled in to the same location.

Set screws
Fortress anchor test.

The anchors had chain attached to cable which was wound around a large drum operated with precision by the vessel's chief engineer. After the anchor reached bottom, the Rachel Carson moved to another position, paying out cable as she moved, and maintained position at that second position. Then the engineer began reeling in the cable at the rate of ten feet per minute. The anchors were pulled for 100 feet, the scope shortening from 8:1 at the beginning to 5:1 by the end of the pull. Sophisticated sensors measured cable tension continuously. The data was transferred to computers. These recorded every change in tension and various other factors. By this means one was able to see the amount of resistance of each anchor as it was pulled through the mud. The testing was done in consultation with Bob Taylor, a civil engineer with widely recognized expertise in the subject matter for over 45 years and a consultant in many anchoring issues, including for the US Navy.

There was great effort to insure complete transparency and equal treatment of the anchors tested. Members of the boating press had been invited and those present were carefully watching every facet of the testing, free to move about and observe all that was going on. No anchor performed perfectly and some, including the Fortress, seemed at first blush to fall below expectations in some of the pulls.

I've learned that anchoring well is primarily an exercise of good seamanship. For example, to get your anchor down into gray clay type of mud (which is what the test site had) you have to take certain steps to work it through the loose mud and into the good stuff. You can seldom just lower it down and start reversing to get a secure hold. Steps you take depend in part on the anchor you're using. Different anchors may need different setting tactics to perform at their best. I'll share more of my setting techniques in a later column on this site.

The protocol of necessity precluded much of the art and seamanship tactics normally used in actual anchoring situations. Also, in order to be fair to all anchors tested, each anchor was, at first, pulled in the same manner. This manner, described above, didn't use any special setting tactics.

Another difficulty was that even with the extensive and meticulous care taken to pull each anchor along the same bottom in each set, there were still variables in the bottoms during each set, such as unexpected bottom debris. It's always this way when you anchor.

Tom's Tips
Tom's Tips On Choosing Your Anchor
1. Don't chose your anchor based on gimmickery, unrealistic boat show demonstrations, on what any one person says or limited testimonials about how well one particular boat held in one bad storm. It's more complex than that.

2. Listen to various experts. Even if they disagree with each other, their experiences can be very helpful.

3. When choosing anchors, talk with and listen to experienced people who do your type of boating, in the areas where you boat and with comparable boats.

4. "Experience" should mean more than just one storm at anchor or a year or two of boating or an ocean crossing trip in which you anchored little if any at all.

5. Use common sense when looking at anchors available. Ask yourself if what you're seeing should really work well, considering what it has to do down on the bottom. Think it through.

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There was another very significant factor that couldn't be helped. The vessel's DPS was truly impressive, but there will be the pulls and pushes of a gust of wind, the current, an eddy, bottom turbulence, waves and wakes. The ship's equipment normally defeats this quickly, but in the meantime the vessel has been moved maybe two or three feet off station. If the vessel moved two feet toward an anchor being pulled through the mud, the stress would immediately spike down as though the anchor had broken free. As the vessel corrected, moving two or three feet back to position, the full force of those engines and thrusters would be transmitted via the cable down to that poor anchor on the bottom, and the stress might spike up indicating that it was holding on with extreme power, until it popped out. The only way to have prevented this would have been to use a vessel with spuds and spud down for each draw. This would have taken forever and would have been much more expensive.

Bob Taylor's report and findings are posted online at the Fortress site: He commented, according to Fortress, that the most notable finding is the huge disparity in Ultimate Holding Capacity (UHC) for an anchor specifically configured for operation in a mud seabed. Changing fluke angle from the regular fluke angle setting of 32 degrees to a mud setting of 45 degrees almost doubled the ultimate holding capacity of the Fortress FX-37 anchor in mud. The bi-lateral fluke anchors (Fortress FX and Danforth HT) achieved the highest anchor capacities for any of the anchors configured for general purpose anchoring. The Ultra achieved the highest average capacity of the fixed fluke (angle) anchors.

None of the above is to suggest that the test wasn't immensely helpful. The fact that you can't duplicate everyday in-the-field anchoring circumstances in a scientifically conducted anchor test doesn't mean that you don't do it and that the data obtained isn't useful. True, that data is only part of the picture, but it gives boaters a huge amount of information. I have to wonder how many other manufacturers have gone to the immense expense and effort, as did Fortress, to provide scientifically obtained and monitored data to the boating public in a transparent manner.

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