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Old 02-08-2016, 05:18 PM   #1
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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.
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Old 02-08-2016, 06:52 PM   #2
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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.
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Old 02-08-2016, 07:47 PM   #3
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Have two types of anchor, one for mud and one for everything else.
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Old 02-08-2016, 09:00 PM   #4
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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?
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Old 02-08-2016, 09:06 PM   #5
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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?
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Old 02-08-2016, 11:16 PM   #6
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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.
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Old 02-09-2016, 12:27 AM   #7
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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.
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Old 02-09-2016, 07:51 AM   #8
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To me the classic CQR is a plow anchor , some companies copy is just that some companies copy.

Think ferrocement aircraft ,,,,
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Old 02-09-2016, 08:05 AM   #9
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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.
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Old 02-09-2016, 08:15 AM   #10
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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.
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Old 02-09-2016, 08:21 AM   #11
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Quote:
Originally Posted by sdowney717 View Post

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.

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.

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Old 02-11-2016, 07:44 AM   #12
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The softer the bottom goop the larger the area of the anchor to hold you in place.

SIZE does MATTER
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Old 02-11-2016, 08:47 AM   #13
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Yep, that's why Navy LST's dropped a 6,600 lb Danforth style anchor on the way into the beach !
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Old 02-11-2016, 09:07 AM   #14
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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.
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Old 02-11-2016, 10:15 AM   #15
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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.
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Old 02-11-2016, 12:33 PM   #16
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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?
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Old 02-11-2016, 02:06 PM   #17
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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.
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Old 02-11-2016, 02:22 PM   #18
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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.
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Old 02-11-2016, 02:43 PM   #19
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Quote:
Originally Posted by manyboats View Post
Was the 6 min factor evident in the Fortress CB test?

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...

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Old 02-11-2016, 03:13 PM   #20
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There is both liquefaction and liquidification...but subaqueous soil would be the appropriate topic in my mind.


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