Anchor test in chesapeake mud - bit of a surprise

[NormanS]

A lead line can tell you a surprising amount about the bottom. Not just from the material which sticks to the lead (or doesn't ), but also you can feel it either hitting solidly, or going in to mud, and having to be pulled out.

My fishfinder tells me whether it is a clean, weed-free bottom, but doesn't clearly differentiate between sand and mud.

 

[GrahamM376]

I use a Fortress as a kedge but, because of the occasional problems breaking it out always us a trip line.

I'm not surprised at the Danforth's performance after helping a mate out here. Nauticat 44. Mainly mud, he laid 3 x (IIRC 30kg) Bruces in diamond pattern connected with heavy large link chain with a riser in the middle for his mooring. Didn't take long for the lot to wind up in a bundle, all dragging. Next time, we laid them in line, 2 laid into prevailing wind and ebb, the third down wind and into flood. All dragged again! He then deployed a single (not too large, can't remember the weight) Danforth and never budged!

 

[estarzinger]

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?

This is an excellent question.

I have owned a fortress 'forever' but have only ever set it in the general purpose setting, and never used the mud setting. I have done this because, while I sometimes know the bottom is mud (from the chart or prior experience), I almost never know if it is very soft or quite hard mud. Fortress has said to me that if I don't know, the general purpose setting is more appropriate.

I am in fact a Chesapeake bay 'local' and Annapolis was my home port. I did not know the mud was so soft in the specific anchorage the test used. I would have probably used the general purpose and not the mud setting there, but I have never anchored there simply because it is in a pretty busy traffic pattern (into a marina) and has a long fetch to the south.

But if fortress is going to be trumpeting a test were the variable geometry played a significant part . . . .then we really need more practical council from them when to (know how to) actually use it.

Note: It is still a pretty high holding anchor even in the 'general purpose' setting, but then probably not statistically significantly better than 'danforth' style anchors.

As to 'holding power' . . . . as far as I am aware, there is no real surprise in this test. The fortress has topped pretty much every test ever conducted in terms of holding power per kg. It is an aluminum anchor designed to maximize fluke area, and in this test took advantage of it being the only anchor with user adjustable variable geometry (the mud setting). It 'should' have the highest holding power/kg. Back when Craig and Alain were active, they both argued that all articles, graphs and tables should separate the 'kedge' designs from the 'main bower' designs and not show them together (as is done in the SAIL graph) because they have different purposes, strengths and weaknesses. They both argued this from self-interested positions (manufacturing rocna and spade respectively), but they did have some what of a point. Brion (fortress) would (and has) argued this, but while I love the fortress as a kedge, special purpose anchor, I would never put it on my bow as the primary every day cruising anchor, no matter what it's holding power is. Even from very occasional use the aluminum gets dinged up, and the hinged design does have jamming possibilities, and potential wind shift difficulties. Again, the fortress is a great very useful anchor, but IMHO is for a different purpose than the common 'bower' anchors.

 

[NormanS]

<not statistically significally better than danforth type.....>

Size for size, I'm sure you're right, but weight for weight?

My second anchor was a 20kg Danforth, and I have replaced it with a Fortress FX23, which is very nearly the same size, but less than half the weight. As far as I can tell, there is no measurable difference in holding capability, but there is a huge difference in handling. If I choose to lay out a second anchor, or kedge, using the dinghy, the Fortress is easily managed, whereas the Danforth was a pain.

Similarly, when lifting anchor, my main 20kg Bruce comes up and stows on the bow roller, but my second anchor has to be man-handled over the rail, so again the Fortress wins.

 

[estarzinger]

Size for size, I'm sure you're right, but weight for weight?

You may be right. I would have to go look at a bunch of numbers to be sure. My memory of the statistics of this recent fortress test were that the mean holding of the fortress at general setting was slightly higher than the danforth mean (edit: the graph says 995 vs 990, pretty much exactly the same) but the difference was not significant at the 95% confidence level (Edit: and 5lbs was most certainly not significant in this test - so you are right it was size for size in this test, because the FX37 weights I think 10kgs or so). It was really hard to generate truly significant difference in this test because of the extremely high variability and small sample sizes (I wish people writing about these sorts of tests would at least learn the very basics of statistical analysis - otherwise they are just writing garbage).

I will comment that whenever I needed personally a 'fast kedge' (just for instance to hold me off a rough fuel dock) I got out the danforth (40lbs), because I stowed the fortress in its bag (un-assembled) so it took longer to use. And the danforth was still 'light enough' to handle easily, which our main bower's were not.

I used the fortress when it was going to be out a while and I needed straight line holding power (just for example in hurricane lenny)

 

[Brian@Fortress]

Typically anchor tests involve Fortress models being pitted against steel anchors which are much heavier and this Chesapeake Bay soft mud test was no exception, as the 21 lb / 10 kg FX-37 was tested along with a 35 lb / 16 kg Danforth HT and nine 44-46 lb / 20-21 kg models.

In terms of physical size, the FX-37 is comparable to the Danforth HT, and both anchors achieved similar tensions when the FX-37 was set at the 32 degree angle. They were also certainly far and away the most difficult anchors to recover afterwards.

Concerning the physical size of an anchor being a key factor in it's holding capability, you must also consider the "effective fluke angle," which we learned from Bob Taylor.

As an example, one of the new generation anchors was physically a beast in size, and everyone had expected that it would achieve among the highest tensions in the test based upon that fact alone, but it was clear by the readings that the large fluke area did not aggressively point down and into the soft mud, and it basically just skated along as it was slowly being pulled.

 

[J Neeves]

One theme that comes through when reading Fortress posts are the numbers of people who keep their Fortress stored in a bag and as a result of the perceived aggravation of assembly actually never use it (and some of these people will quite happily take the head off their engine!). Unless you are really stuck for space or on a racing yacht there is no reason not to assemble a Fortress and have it available for immediate deployment. In fact if you cannot use it easily there seems little point in carrying it. It is much easier to lift a 10kg Fortress over the lifelines and then lower it in a controlled manner than a 25kg, anything else. its much easier and considerably safer to deploy a 8kg or 10kg Fortress from a dinghy than a 25kg + steel anchor.

It is not difficult to lash a Fortress to a stanchion/lifelines, transom or if you are lucky - store in a deck locker.

There is another continual theme - a Fortress performs poorly with a wind shift - if you are using a Fortress as an anchor of final resort (to be used to supplement a bower) then you will be deploying for strong wind conditions - and my experience in the UK (limited to 25 years in Scotland) and Australia is that strong winds are well forecast (timing and strength might be out but they usually get direction right), and these winds seldom veer more than 90 degrees - and this concept of an inability to cope with a wind shift is simply irrelevant (obfuscation comes to mind). Circular storms are different - but you would have different approach anyway - and circular storms are not that common in the UK.

We would not use a Fortress as our main anchor as to accommodate it we would need to alter the complete structure of the bow as well as the bow roller and I'm thinking over stg1,000. The stock on a Fortress is additionally not yacht friendly. But we would not leave home without our FX23, assembled and ready to deploy - and we do use it, frequently but we 'enjoy' anchorages that are subject to fairly frequent 35 knot + winds

Most anchorages that most people use today are very well documented and seabeds described, the exception being places so remote and distant that few venture (and even these are covered in Admiralty Pilots - whose origins were small boats). Changing the fluke angle on a Fortress is no more complex than taking in a reef and if its so much of a hassle, buy a second Fortress, Brian@Fortress will love you

There does seem a desire and theme from some to find (and emphasise) fault, many of these faults are common to other anchors and many of which are simply irrelevant, and these same people completely downplay, ignore and belittle the advantages of a Fortress and completely ignore and downplay the disadvantages of other anchor(s). It reminds of a group of less endearing creatures in Lord of the Rings.

Again, anchors are a compromise, there is no perfect design that will suit all seabeds and all conditions. Fortress have shown most anchors have at least one Achilles Heel and that is not the end of the story

Jonathan

 

[estarzinger]

>>It is not difficult to lash a Fortress to a stanchion/lifelines, transom

Not ever on a boat of mine. Personally I consider that crappy seamanship and boat preparation. Don't need misc heavy chunks of metal on deck that could come loose in a breaking wave (and it looks like **** also).

I like the fact the fortress disassembles and they provide a well designed bag for it. That's a plus in my book.

And related to this discussion it is no big help to have it already assembled if you are going to be switching between the two angle settings.

>>you will be deploying for strong wind conditions . . . and these winds seldom veer more than 90 degrees

What!? First the amount of shift has fundementally nil to do with the strength. The shift is all about the pattern, and the strength about isobar compression - two seperate things. And second there are often greater than 90 degree shifts. If a low pressure goes overhead you frequently get more than a 90 degree shift, sometimes almost 180.

Just for instance, on the current Atlantic weather chart - look at the 130 degree shift you are expecting at the red X View attachment 47986. Pretty much any time you look at the Atlantic chart you will see at least one shift like this.

There's real good reason that from ireland to scotland people look for 360 degree protection and that the top anchorages provide that.

>> circular storms are not that common in the UK.

What!? UK gets rotating low pressure systems commonly fall winter and spring. Perhaps less so in the summer. If you mean hurricanes, UK gets the tail end of hurricanes. And hurricane force lows during the winter.

Are you really seriously arguing (as you seem to be) that winds shifts are so rare that you don't think it important how well (or poorly) an anchor handles them!?

>>Most anchorages that most people use today are very well documented and seabeds described, the exception being >>places so remote and distant that few venture

Not where I have cruised, and not in the Chesapeake. I have only rarely seen a cruising guides be as specific as "very soft mud". Tell me, in English Harbour, back behind nelsons dock yard, near the mangroves, mid channel (where I laid the fortress for hurricane Kenny) what exactly the bottom is? I had every guide available and did not really know (I do now). The guide I have of the Che's bay does not specify "very soft mud" in the fortress test spot.

I still think the question asked above about how do you know when to use the mud setting is interesting./useful/valuable and one that fortress should address more comprehensively.

JN, I am thinking you may have been drinking some pre-Christmas cheer when you wrote your post . . . So merry Christmas all

 

[J Neeves]

JN, I am thinking you may have been drinking some pre-Christmas cheer when you wrote your post . . . So merry Christmas all

It was already Xmas here and chilled drinks the order of the day.

If you do not lash your boards to the stanchions where on earth do you keep them?

Possibly the reason you do not have good Admiralty Pilots is/was you dispensed with the services of the RN, your loss obviously

Best wishes to you and yours.

And compliments of the season to all.

Jonathan,

 

[VO5]

The problem with the bottom in the Chesapeake is that it consists largely of mud of varying consistency of goo. Invariably when the anchor is recovered both the anchor and chain have to be hosed down thoroughly because the mud clings persistently.

What I have done is to arrange two anchors in tandem, both ploughs, and that has done the trick because invariably the first one sinks and the second not so much, thus ensuring holding power, and both on chain and not rope as is popular among American boaters, of the sailing variety not the headgear sort.

Compliments of the Season to you all.