Anchor test in chesapeake mud - bit of a surprise

Just a word of caution to anyone planning to adjust their Fortress to 45 degree setting based on this test. This setting is only suitable for soft mud.

If you try and use the 45 degree setting in a substrate that is slightly too firm the anchor will not work at all. The conventional 32 degree setting will allow the anchor to work in any sort of substrate. In a very soft substrate the holding power will be higher on the 45 degree setting, but you need to be sure of the substrate before making the adjustment.

The instructions for making the adjustment are here:

http://fortressanchors.com/anchors/fortress/fluke-position

It is also worth checking your Fortress is not accidentally set to 45 degrees. I see a few that are.
 
I use my Fortress as my second anchor, and also as what I would call a main anchor, when I rig a Bahamian Moor. The place where I regularly do this, in order to leave my boat unattended for several weeks, has a clean soft mud bottom. You can be sure that when leaving the boat to her own devices, in the Outer Hebrides, I make certain that she is secure.

Each anchor, in turn, is subjected to full cruising revs from my 59hp engine. One anchor is a (genuine) 20kg Bruce, the other is a Fortress FX23, about 8 or 9 kg IIRC. I cannot get either anchor to drag. What am I doing wrong?

Even though the mud at this particular site is very soft, I have never been tempted to change the Fortress setting to 45º. To me, that just seems too much.
 
Norman: although the Fortress test (Sail mag version) is replete with data, the striking thing that is not quantified is the mud. Yes, it's 'soft mud', and once 'very soft mud', but what that actually means is inevitably highly subjective. My soft mud may not be the same as yours.

Fr'instance, a few years ago I anchored in Arisaig in a ferocious blow, gusts peaking at over 60knots (according to the harbour office anemometer). Arisaig, I was told at the time, was 'soft mud'. I had a pair of Bruces out, one 15kg, the other 7kg. Had I read the Sail test I would clearly have dragged halfway to Oban. Luckily I hadn't, so I didn't. In fact recovering the little Bruce nearly ruptured me: it was seriously buried.

The one notable lesson was that every yacht with one anchor out did drag; not one with two out dragged. But evidently Arisaig's soft mud is tougher stuff than Chesapeake's.

And here's more mud in your eye: slange.
 
NormanS said:
Each anchor, in turn, is subjected to full cruising revs from my 59hp engine. One anchor is a (genuine) 20kg Bruce, the other is a Fortress FX23, about 8 or 9 kg IIRC. I cannot get either anchor to drag. What am I doing wrong?
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Hi Norman, you are not doing anything wrong :).

There is mud then there soft soupy mud.

Anchors should be able to hold full reverse. I use full reverse for thirty seconds when setting my anchor. In wind above about 30 knots the anchor will start to bury more deeply, indicating that this setting force is equivalent to about 30 knots of breeze.

The other estimate you can make is that 59hp should exert about 1,100 lb of pull on your anchor (this depends on prop etc so it is only a rough guide). This 1,100 lb of pull can be converted to windspeed to give you another idea of the equivalent windspeed you are testing each anchor with your setting force. For this we need the size of your boat which I don't know.

Please bear in mind that these calculations are very rough, but they will give you a ball park idea.

Normal mud is good holding and has the advantage that most anchors work well. Soft mud is a little more problematic. Some of the anchors with a small fluke area especially the convex plough anchors start to struggle, but even then they should hold at more force than you will generate under engine power alone.

It is only in very soft mud that many anchors start to struggle. When a Fortress set at 45 degrees is struggling to generate enough holding power you know it must be very soft mud.

In the Fortress test substrate the larger brother of your anchor (the FX-37) set at 32 degrees would probably not have held your full engine reverse in any of the 5 trials. Even set at 45 degrees the FX-37 would not have held your setting force in two of the five trials. This shows how soft the mud was for the test.
 
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Hi Noelex,

Realistically, most of our soft mud has firmer mud under it, so provided you don't just drop the anchor, and then go shooting full astern right away, the anchor gets a chance to penetrate the soupy stuff. That's partly why I'm not keen on setting the Fortress to 45º.

By the way, boat is a 36ft deck saloon ketch, and although her masts are relatively low, with two there's a fair bit of windage. The prop is an Autoprop, setting its pitch automatically, and is, I believe, very efficient.

Hi macd,

Yes, I reckon if you believed everything that's written in supposedly unbiased anchor trial reports, you wouldn't sleep at night. like you, in 60 knots of wind, I would have two anchors out. That has never let me down.
Lang may yer lum reek.
 
dylanwinter said:
http://www.sailmagazine.com/tips-an...-anchors-chesapeake-bay#.VJWLU-CjpU8.facebook

BarGraph_0.png
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Maybe I'm cynical but every american test says the Fortress is the best. Every French test says that the Spade is the best.
 
Noelex,

I had been invited to attend the Chesapeake tests but frankly could not justify the journey. However I have been asked by 4 publications, UK, Germany, USA and Oz, to produce a summary based on information derived at the tests and I asked Fortress for access to the fullest of information. I have also canvassed comment from a number of people who use the Chesapeake as their home cursing (edit, should read 'cruising' - but its worth leaving in! close edit) grounds and from international cruisers who have visited the Chesapeake but have exposure to many other locations as well. I hope I obtained a balanced view. Fortress provided all the raw data, access to their dropbox and access to information (non confidential) provided by observers to the tests. Fortress also provided links to the various videos that were made. The information from Bob Taylor was included. There was a lot of information! I can assure you there were no private emails from you nor private emails from anyone else - the information I received was only from experts in the field.

The emails from Bob made complete sense as I had had correspondence from John Knox over the last 6 or 7 years and I had already queried his data and interpretations.

I am grateful to have access to Bob's data which I will possibly use (at some time in the future) in an appropriate and fair manner.

However if you knew Bob Taylor's comments why did you only publish the information from John Knox when you were well aware Bob's comments totally contradicted that of Knox. You made no mention that an experts in the field, working on anchors for 60 years, disagreed with John Knox. You in fact say you agree with Bob, so why did you post John Knox data in the first place. I would have no query if you had published both and made your own interpretation but publishing one side when you had access to the other side, and agree with the other side, looks biased and designed to distract from the message Fortress are making.

You take every opportunity to bag the opposition - this is simply another example.

It has been shown that the speed at which an anchor is dragged in an anchor test has no impact on the holding capacity developed. If you extrapolate this you will find that at 'no speed' the holding capacity is the hold that an anchor develops - which is part of Bob's message. Bruce and Vryhof have both done much work on the topic and copious industry and University research papers have been published

Excuse me if I maintain the thought that you have another agenda. The evidence of your bias grows and this is, frankly, simply another disgraceful example.

Finally you venture to offer your advise based on hindsight - that a firmer seabed would have been more useful. Fortress have revealed a glaring weakness in many designs (which you continue to ignore) - this would not have been evident if they had chosen a firmer seabed - and we would remain in blissful ignorance. I can understand that some anchor makers, and as you imply - yourself, would have preferred the state of ignorance - but in the real world we need to know. Fortress have also underlined the fact that most anchor tests are conducted in sand and that characterising performance of anchors in other seabeds is lacking - it seems unlikely but maybe the anchor industry (and yourself) will take notice.

And to try to offer balance to the negativitiy you express - Fortress have sold over 0.5 million anchors, Danforth continues to be held in extremely high regard (even though the basic design is over 80 years old). They both have much more than something right.

Jonathan
 
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LittleSister said:
Love it! Ours is like that, too. :D
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Sorry, I'm in receipt of a Mac and it has a mind of its own and makes its own decisions on how to correct my spelling mistakes - sometime they are humorous, sometimes incomprehensible.

I need to check more often.

And to Dylan, the whole idea is to entertain and educate (or is it educate and entertain).
 
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jdc said:
Surely the Bruce?

(Actually it was, apparently, developed on the Isle of Man)
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I'm not sure that's true. The company was a few years ago (and maybe still is) registered on the IoM, but that's far from the same as having an engineering presence there (or here).

Just checked and Bruce Anchor Group is still registered in Douglas. There's also Bruce Anchors (Scotland) Ltd in Livingstone, Lothian, but they're just a 'small company', probably at most a subsidiary.
 
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For additional background information to this discussion, Bob Taylor spent over 45 years in anchor design and soil mechanics with the U.S. Navy and offshore industry. He has met Peter Bruce and discussed anchor design with him, and our late company founder was a follower of Bob's work, as he kept a small library of his U.S. Navy reports on anchor design and performance at our Florida manufacturing facility.

Bob was aboard for the 1990 San Francisco Bay soft mud tests and a family health situation kept him from being aboard the recent Chesapeake Bay test, but he was very helpful to us as a consultant on this project.

While some of the boating writers and staff aboard the 81-ft Rachel Carson RV test boat were surprised by the results, particularly from the highly touted "new generation" anchors, Bob was not, as he stated that an anchor which is designed and optimized for a harder soil will typically only have a holding ratio (holding capacity divided by anchor weight) of 10 - 15 in a softer soil, and that is almost exactly what we found in the soft mud of the Chesapeake Bay.

For example, during the majority of pulls, the 44-46 lb (20-21 kg) steel anchors achieved tensions that were in the range of 400-700 pounds. One of the most puzzling of the models was the Rocna 44 lb (20 kg) as it failed to achieve a minimal 300 lbs of tension in 3 out of 5 pulls, which led to comments of concern as to whether this anchor would be able to orient itself with the fluke in the downward position if it landed upside down, or on its side when pulled along in soft mud.

Noelex, I know that you are a huge proponent of the Rocna anchor and you have an oversized 121 lb / 55 kg model aboard your boat, and additionally a comparably sized Mantus. If the holding ratio of 10 - 15 held true to your anchor models in soft mud, and there's no reason to believe that it wouldn't, then neither of these anchors would offer you much in the way of a factor of safety when anchored in this bottom condition.

In the best interests of boater safety, I think your forum position as a leading anchor commentator would be better served to get this information out to the public, rather than to continuously post images of anchors set in ideal hard bottom conditions when they should all perform optimally.

Regards,
Brian
 
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Its always appeared to me that a Danforth type has a great deal more surface area than any other type so I'm not surprised that they do well in this type of material. The plough and cqr type have a much lower surface area and must rely on weight for much of their holding.
Mud, being cohesive, will behave very differently from sand (a granular material). In an anchoring context, they are both saturated which affects their properties massively.
 
How easy is it to ascertain the nature of the bottom, without anchoring and dragging up a large sample? In the Med I'm sure you can see it - but elsewhere? Not many use tallow on a lead line, and I wouldn't have thought even that would tell you how soft the mud is, and what fluke angle you should select. So how do you do it - do you have a better way when you arrive in an unfamiliar anchorage?
 
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