All plow anchors did poorly in mud after 6 minutes

I watched this and actually wonder, do you know if plow anchors will grab hold for 6 minutes in mud and then they all break out drop close to zero holding? They consistently make this observation in the video. Why is that?

I anchor in the Chesapeake mud using a big Seachoice fluke anchor and it mostly works fine holding the 37 foot boat. Even in a thunderstorm it has held without slipping. Also I don't have any chain.

Maybe they have a harder bottom 8" down and the anchors temporarily dig in some but break out of the harder sub bottom and then drag along w a big lump on their nose?

Not a very good guess though.

Hard to imagine why the Rocna didn't do squat where many other anchors did at least fair. Perhaps the roll bar is too small. So many here on TF have or at least reported very good setting performance. The Mantus roll bar dosn't look so odd now.

Re the plow anchors and the 6 min problem .. it has all to do w the bottom and not the anchors IMO.

Have two types of anchor, one for mud and one for everything else.

Too bad they didn't stick a GoPro camera on the shanks before they dropped them (carefully). That way, you would get a good view of the anchor that could be tied to tension performance. That was done in 2014, so probably before GoPro took off.

Maybe next time?

Believe most all anchors will do well in the thick, deep, sticky SF estuarian mud. Never had an anchor there needing to reset itself. Anchoring, isn't it all in the bottom?

Mark,
Indeed the bottom is by far the greatest variable.
Next could be the weather. Very few have anchored out in winds of more than 35 knots. I anchored in very benign weather in "Windfall Anchorage" and the name should have been a clue. I was clueless of course and anchored in the very small anchorage w a 13lb Danforth. Fortunately the little Dan was/is a good anchor and held us all through the night in 35 knot winds. A lot of jerking back and forth and swinging though.

But I also made a trip to Juneau and back to WA on our 25' Albin using a 16lb Claw. We may have had some wind somewhere but I don't remember it. Benign weather it was and a 6lb Claw probably would have held us.

So w the #1 variable (the bottom) and the #2 variable .. the weather .. the anchor used kinda looks like an also-ran. But as we know there are variables in the anchors (all of them) but if we can get the bottom, the weather and a good anchor for the bottom at hand we have more than an excellent chance of staying .. anchored.

I have have a plow anchor, mine plows in bay mud. I am not a huge fan of plow type anchors even though mine main anchor is just that. I carry a back up
Danforth and in the past have never had a problem in mud with the Danforth. I always seem to have a problem getting my plow to really harden up in mud. it may do better in sea grass over sand, but then again I have trouble getting it to really bite in sea grass as well. It does well in sand and rocks.

To me the classic CQR is a plow anchor , some companies copy is just that some companies copy.

Think ferrocement aircraft ,,,,

Never an issue with my Delta in all sorts of mud bottoms. I carried a big Danforth as a ready-to-drop spare, and thought I'd change back to it when cruising and gunkholing around the Chesapeake, but never did bother.

I think one could make any anchor look good or bad depending on how you test it.


What's most important for a boater is; how well does it work on my boat in the areas where I operate my boat?


The reason I don't rush out and buy a new $400 anchor is, my $100 anchor has never let me down.

sdowney717 said:

I watched this and actually wonder, do you know if plow anchors will grab hold for 6 minutes in mud and then they all break out drop close to zero holding? They consistently make this observation in the video. Why is that?

I anchor in the Chesapeake mud using a big Seachoice fluke anchor and it mostly works fine holding the 37 foot boat. Even in a thunderstorm it has held without slipping. Also I don't have any chain.

Click to expand...

Quite a lot of discussion about those tests here on the Forum as they were happening. Maybe 2 or 3 long threads, IIRC, so you might review those if you haven't already.

As you know, there's mud here in the Chesapeake, and then there's mud (slime) here in the Chesapeake... so bottom material is key and varies. Then there's rode composition. Then there's setting technique. Boat weight. Windage. Choice of anchorage (protected? open?). Weather. Tides/current. Eventually comes anchor design, size, weight... ideally matched to all those other factors.

No surprise your flukes seem to do well.

-Chris

The softer the bottom goop the larger the area of the anchor to hold you in place.

SIZE does MATTER

Yep, that's why Navy LST's dropped a 6,600 lb Danforth style anchor on the way into the beach !

Other than a CQR (obviously a plow anchor) what is a plow anchor? What brand/style do you consider a plow? If we're going to talk about farm anchors it would be best to get on the same track.

For openers I would assume all concave fluke anchors are not plow anchors but does that make all convex fluke anchors plow anchors? And IMO flat fluke anchors are'nt plows either. Both the SARCA and the Excel are convex. But are they plow anchors? The SARCA seems not to me but the Excel and Delta are quite likely plows IMO.

I have a suspicion on why they fail after about 6 minutes. It's process called liquefaction.

If you stand in the surf and move your feet back and forth, the sand will get wet, smooth and buttery, and you will sink into the sand. It is the same thing that causes SF Earthquakes to be so bad. Since the earth is moving, it turns to jelly and everything built on it shifts, sinks and cracks.

So, back to the anchor problem. It has tension on it, with chain & cable rode. I suspect the chain and cable are vibrating with the tension, waves and movement of the boat / barge. I suspect that it takes about 6 minutes to soften the sand around the anchor and let it move.

We had a problem with telephone poles sunk in sand when we had three hurricanes. The high winds caused vibrations on the power lines and that made the poles vibrate. The vibration softened the sand at the foot of the poles and the wind force pushed them over. Once the storm was over the sand dried out and hardened again, with the poles at an angle... I have no idea how many poles FPL had to replace but it was a big number.

Liquefiction ..... hmmmmm

Tallys up to some degree ... except for the vibration. I'm thinking the chain would have a hard time vibrating sourounded by dense water. If so though it could be an advantage for the nylon rode. Perhaps it's an all metal rode thing?

I'm more inclined to buy into the liquefaction (or is it liquification) factor. Perhaps it's a pressure thing. The anchor fluke being pulled has high pressure on it's face and lower pressure on the backside. Over time (6 min?) the water on the face in the sand and mud may tend to gravitate around to the backside. Then "deliquification" would/may occur on the fluke face and "liquification" (or increased liquification" would/may occur behind the fluke/flukes.
The problem w that possible theory is how would that bring about draging or sudden decrease in holding??
Perhaps at some point the liquification causes the cohesiveness of the compacted seabed to break down and start flowing? But it would seem to me that compaction would cause the bottom to become more solid and inhibit flow or movement.

But it's a good tree to bark at in that the seabed is a fluid .. perhaps even w/o water. Sand "flows" around a small anchor in a sand box w/o water.

Sand and water and gravity create a mass of sand to settle together (like crushed gravel) and resist movement. But given enough water the cohesiveness of the mass could suddenly (relatively speaking) allow the whole mass to "flow".

But how would that apply to an anchor in the seabed?

Was the 6 min factor evident in the Fortress CB test?

The vibration I was referring to would be any catenary swing that might happen due to waves on the boat. Certainly it is changing tension nearly constantly, and secondly the engine(s) pulling the boat / barge. Since the wire rope has very little give, and chain almost none too. Anything beating on the barge is transferred to the barge.

I had thought it was liquifaction, but the Chrome spell checker corrected me... Who knows who is right.

Thinking like Spock again, it seems logical that it would move a few feet into clear bottom and set again, then repeat the process. But holding for 6 minutes and releasing for good is a strange sequence of events.

Maybe the bottom mud on a plow style anchor starts acting like a boulder, as if a metal ball shell forms around the anchor and it then drags thru the mud. Bottom mud is sticky gooey stuff and so it sticks together forming itself into a structure on the anchor, the anchor no longer works. Sand bottoms are loose, wont stick together and the anchor can cut into it. Instead of forming a ball, it flows away from the anchor, so the anchor can hold.

A fluke Danforth style in mud, they mention it buries itself, like it keeps on diving into the mud deeper like a knife edge. At one point in these tests they mentioned the Fortress had buried itself 14 feet into the mud.

manyboats said:

Was the 6 min factor evident in the Fortress CB test?

Click to expand...

Pretty sure the video OP posted is from the Chesapeake Fortress tests...

Didn't go back to see whether specific timing was mentioned in the original posts and derivative articles/reports...

-Chris

There is both liquefaction and liquidification...but subaqueous soil would be the appropriate topic in my mind.


https://en.wikipedia.org/wiki/Subaqueous_soil

FF said:

To me the classic CQR is a plow anchor , some companies copy is just that some companies copy.

Think ferrocement aircraft ,,,,

Click to expand...

My CQR emblazoned with "Made in Scotland!" does just what Big Daddy Lipscomb used to do for the Giants, a few gens back:

"I grabs me an armload of football players and picks out the one with the ball."

sdowney717 said:

I watched this and actually wonder, do you know if plow anchors will grab hold for 6 minutes in mud and then they all break out drop close to zero holding? They consistently make this observation in the video. Why is that?
.

Click to expand...

Because of "good" marketing by Fortress

Over the course of 4 full days, every anchor was tested in a fresh, close proximity seabed and pulled using the exact same starting scope, and for the exact same distance, speed and time.

The test results were measured using a running line tensiometer and were clearly viewable aboard the test vessel on computer monitors.

There might have been several pulls when the tension built to around the 6 minute time period, but then the anchor broke free and the tension quickly declined, as it was likely that the fluke(s) was full of compressed sediment and it could not re-penetrate the bottom

Articles, comments, test results and videos are on the web page below:
Fortress Anchors – The World's Best Anchors! – Chesapeake Bay Anchor Test

Safe anchoring,
Brian

Didn't see many in Alaska but I see lots of Fortress Anchors at the marina in LaConner WA. Danforth and Claws too.
Haha no Dreadnoughts though.

Most all bottoms around the world are mud of some sort. Alaska having such a rocky coastline led me to believe there were lots of rocky bottoms but few were found. I think the rocks are covered up w mud by the hydraulic forces on land caused by all the rain and snow. And in the desert offshore winds transport the makings of mud. And time ... lots of time.

Re the failure after breaking out compaction of the mud bottom on the fluke makes a bullet shaped anchor out of a plow anchor. And even more so the scoop anchors it would seem. Do the scoopers do the 6 min dance too?

Besides the obvious warning that the testing was conducted by Fortress, rather that a truly independent testing facility, the test methodology was both odd an not a 'real-world use case'.

The scope was laid out first. The vessel was held in position, then the anchor was retrieved, slowly reducing scope until it broke free. In a real world scenario, scope would not be reduced as a mechanism to apply force.

Shrew said:

Besides the obvious warning that the testing was conducted by Fortress, rather that a truly independent testing facility, the test methodology was both odd an not a 'real-world use case'.

The scope was laid out first. The vessel was held in position, then the anchor was retrieved, slowly reducing scope until it broke free. In a real world scenario, scope would not be reduced as a mechanism to apply force.

Click to expand...

In a real world scenario, surging seas can shorten up the scope which in turn would apply a force, or load, on the anchor.

What holds the anchor in soft stuff is the anchors projected area.

Look at it down the shank as the mud would to see whats holding you..

The Danforth and its newer copies have huge areas , the CQR less.

WE usually go up one size , if a 35 Danforth would do the 60 CQR would be set if desired.

This makes the projected areas about the same , and a second or stern anchor is usually not required as a Danforth or Danforth copy would require in a reversing tidal area.

FF,
You go up one size .....
From what? What the manufacturer recomends? Or what was on the boat when it was bought? Or from a guru's boat on your float?
From what is all over the map. And tends to grow and grow. But you say all the cool guys say "bigger is better".
I say ( for whatever that's worth) bigger is only better if too small is what you've got. And many want to be extra secure or even totally secure. Bigger is better got a whole lot smaller when the GPS anchor drag alarm was introduced. Unless one's GPS goes TU anchor dragging is just an inconvenience.
Only experience can give a good chunck of mind peace. If I can hold fast w a given anchor and boat in Alaska in a 50 knot gale I'm going to feel quite comfortable anchoring in Washington w almost any anchor where 50 knot wind is rare.
But if you consider the biggest variable in anchoring (the bottom) perhaps the perdieved best anchor and anchoring technique still won't be secure. OK it looks like you're right FF ... bigger is better.
But only in anchoring. A bigger boat or engine may definitely not be better.

Surface area can definitely be a factor in developing resistance, although we learned that if the "effective fluke angle" is minimal and not very aggressive, and the fluke does not orient downward and into the bottom, then even a physically large anchor is likely to simply slide through the soft mud.

Additionally, widening the shank / fluke angle to 45° in soft mud allowed the Fortress to bury far deeper and develop significantly greater resistance, at least 2X versus the standard 32° angle.

While Fortress holds a US patent on the adjustable 32° / 45° shank / fluke angle, widening this angle to improve holding in soft mud is certainly no secret, as large anchor manufacturers such as Bruce, the US Navy, and Vryhof all make anchors with this capability.

Here's a write up on this topic from Vryhof's latest 172 page anchoring manual which is available for download or viewing on their web site.


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Shrew,
Good point.
But the method Fortress used did IMO show what the anchors could do anchoring in slimy mud. No anchor test will duplicate your next anchoring scenario. And no anchor test is free of all the troublesome variables. Lots of anchor tests can be very misleading I admit. The one that takes the cake (as they say and IMO) is the Mantus vidio of someone pulling a Rocna over a hard sand beach at the perfect angle so it only skids along. And Rocna did a similar one pulling a CQR over a dry beach at high speed. Pulling anchors in sand boxes at boat shows or (to a lesser degree IMO) dragging anchors on beaches at low tide not even in the water is lacking of real world anchoring but they all "indicate" what an anchor may do in the real world. Steve on Panope came about as close to real world as one can get but his tests were'nt really representing typical anchoring .. more like worst case scenario in a specific way (tide reversals). Steve was going up north last I heard.