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Old 06-05-2014, 08:26   #1
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Mantus Anchor "Resetting"

I have been avidly observing anchors underwater for many years, but have only recently purchased an underwater camera. I hope to be able to use it to illustrate what happens underwater to anchors in various situations.

The first situation is the anchor "Resetting" with a shift in wind direction.
There is a commonly held belief that during resetting the anchor most frequently breaks out, flips over, and then resets itself. In practice a good quality anchor that is set well initially does not (or at least very rarely) do that.

The anchor remains buried and shuffles around remaining set. It will develop a list as it rotates so is a bit more vulnerable to breaking out, but good anchors look very stable as they rotate. It is one of the hallmarks of a good anchor design (if you want to use it as a bower anchor)

I have seen this many times with my Rocna and managed an early glimpse of this same performance with the Mantus. So I thought I would share the photos.

The Mantus was set yesterday with a very light southerly wind @4:1 under full reverse. The set can be seen in photo 1. It is early days with my testing of the Mantus, but it has been setting beautifully and this is no exception.

The wind has swung around today almost 180 degrees.
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Old 06-05-2014, 08:28   #2
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Re: Mantus Anchor "Resetting"

Photo 2 shows the Mantus today with the chain leading almost back along the shank, but with the anchor unchanged. It actually takes a fair bit of wind to get the anchor to move at all. It is not unusual for the boat and chain to swing around to a new position and for the anchor to remain unmoved.
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Old 06-05-2014, 08:30   #3
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Re: Mantus Anchor "Resetting"

Photo 3 shows the anchor in the process of shuffling around. It was taken late in day so the quality is not great. but the anchor has rotated about 40 degrees without any tendency to break out or need to "reset". If the wind keeps up and in this direction it should keep rotating around in this manner.

So next time there is large wind shift don't worry that your anchor will be yanked out and have to dig itself in again. If it's a good anchor it will be doing the shuffle .
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Old 06-05-2014, 08:48   #4
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Re: Mantus Anchor "Resetting"

I've had good anchors pop out in strong wind against current situations when they repeatedly get snatched in opposite directions. Once had two anchors pop in a pre-dawn frontal passage when the wind went from 40k southerly to nothing to 55k northerly in about a minute--fortunately they reset by themselves after dragging about 5 boatlengths.
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Old 06-05-2014, 08:56   #5
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Re: Mantus Anchor "Resetting"

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Originally Posted by noelex 77 View Post
So next time there is large wind shift don't worry that your anchor will be yanked out and have to dig itself in again. If it's a good anchor it will be doing the shuffle .
That seems like a broad statement. There are so many different bottom types and anchor sets.
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Old 06-05-2014, 09:16   #6
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Re: Mantus Anchor "Resetting"

Great pics! thanks. It is amazing with an anchor buried in sand like that how they will hold fairly well even backwards. I have observed my Delta is similar sand in the Caribe in steady 33-35 knots of wind and the chain was still buried 10 feet in front of the anchor and had a catenary in it still. Why? no seas... perfect water protection and the water had at most a 6" chop. I've had 20 knots of wind but 3-4 foot wind waves yank the chain bar tight and jerk the anchor out. I guess it's the water action that's the issue.
The old CQR's with the swivel shank did wind shifts fairly well until they broke loose and just dragged along the bottom.
Yeah anchors do roll over sometimes too. Usually the problem when they do that, is they lay on their side, less aggressively digging in. Even a ballasted Delta will lay on it's side and drag.
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Old 07-05-2014, 03:13   #7
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Re: Mantus Anchor "Resetting"

The wind has been switching all night.
So I went for a look at the Mantus this morning.

It has rotated about 120 degrees from its position last night, but back in the direction it came from.
At the moment the wind has shifted again and the chain is coming at well over 90 degree from the anchor (the chain can be seen in bottom of the photo).

The Mantus has remained very well set, and has not moved an inch apart from rotating. It has a slight list of about 10 degrees, which is excellent performance especially with the chain and therefore the force leading off at right angles as it is at the moment. This constant sideways pull is normally a little unsettling to an anchor and it has done a great job to remain beautifully set.
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Old 07-05-2014, 03:14   #8
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Re: Mantus Anchor "Resetting"

This photo shows better the arc of sand has been scraped out by the shank as the anchor has rotated over 90 degrees. You can see the anchor has rotated, but not otherwise moved.
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Old 07-05-2014, 03:29   #9
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Re: Mantus Anchor "Resetting"

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Originally Posted by Guy View Post
That seems like a broad statement. There are so many different bottom types and anchor sets.
If a thunderstorm passes directly over head, I'd need to agree with Guy.

Its not the benign conditions we worry about - possibly even 'poor' anchors will swivel - but the extremes are the concern, I am sure - you or someone else (if not many) have said the same on many occasions.

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Old 07-05-2014, 05:54   #10
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Re: Mantus Anchor "Resetting"

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That seems like a broad statement. There are so many different bottom types and anchor sets.
I have spent about 2000 nights at anchor with a Rocna. Most of them I have dived and looked at the anchor so I have seen the anchor reset on many occasions in different bottom types.

It does depend on the quality of the anchor's stability when rotating. They must also be set well before the rotation. If the anchor is not well set (because the anchor will not set well in that bottom type, or the anchor is not set with sufficient force), it cannot do this shuffle.

An anchors ability to remain stable and buried is one of the important aspects of anchor design (for a bower anchor) that has unfortunately been given very little attention.

It is reasonably obvious when diving and observing anchors which anchors are struggling. They develop a very high list and expose a lot of fluke. It is disconcerting to watch and if a strong enough gust hits at the wrong time the anchor is vulnerable to being pulled out and dragging.

One of the reasons that the Rocna, Manson Supreme and the steel Spade are my favourite bower anchors for general bottom conditions is that they are reasonably stable rotating around during a change in pull, developing only a little list and remaining well buried. Some other designs do this less well. It is very early days for my Mantus testing having only seen a few snapshots of its performance as it rotates on one occasion, but this was an excellent performance.

Anyway, I hope the photos help convince people that the "break out, rotate and then have to reset" model of anchor performance does not match the reality of the performance of a good quality anchor that is well set.

That does not mean you should not be totally nonchalant about a large change in the direction of pull with stronger wind. Even good anchors typically have a 20 degree list during the rotation so they are slightly more vulnerable during this phase.
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Old 07-05-2014, 15:46   #11
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Re: Mantus Anchor "Resetting"

Noelex,

I do not think anyone is arguing that a well set anchor will shuffle round if the wind or tide allows a gentle rotation. However life is not quite like that and in a sudden wind shift, the best example is a storm cell passing directly overhead, you may have 35 knots in one direction and then 35 knots in the opposite direction - it is in that scenario the anchor might pull out and not shuffle - and there have been tests to illustrate how anchors might perform.

Based on you past posts I think you do not believe that such a situation will ever exist - sit in a channel with a 5, or more, knots of tide + some wind and you might consider differently. Close to your home think Hunter Passage or FNQ.

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Old 07-05-2014, 16:24   #12
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Re: Mantus Anchor "Resetting"

It's all good info. Yes the rapid shift and pull out does exist also. No Name harbor Biscayne Bay 1998: At anchor a full week. Daybreak no wind. 10 minutes later anemometer is pegged at 70+ MPH with a 180 degree wind shift. The well set anchor pulled completely out and I barely got the engine going and in gear before we hit the beach. I could only hold position at full throttle losing a little ground. I literally threw the large Fortress backup in the water as the keel occasionally bounced on the ground. It held. Wind died gradually to the 30's over the next 15 mins or so.
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Old 07-05-2014, 16:55   #13
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Re: Mantus Anchor "Resetting"

We found that most (all?) medern anchors, did not try CQR nor Delta, will shuffle round if well set (top of shank only showing) if you pull at less than about 140 degrees and are not too aggressive with the pull. As long as the anchor has time to stay 'settled' then it will shuffle. The tests are well documented. I suspect if you simulate a 35 knot prolonged gust, even on a reasonably well set anchor, at say 130 degrees - it might still pull out.

However all anchors tested when pulled at 150 degrees (to set direction) or only 30 degrees off an opposite pull will break out and sommersault.

But a really well set anchor, where nothing is visible, can hold (back to front) as long as the wind (or load) is not too great. This has been reported of some modern anchors, but insufficient to determine whether true of all modern anchors - but I do not see why not. As an example I have heard of Fortress that have been abandoned after hurricanes- they have buried so deep they have been irretrievable. This is not a fault of the Fortress - it did what was required, held the yacht.

My view of your observation is that they are valuable, in that you clearly demonstrate what most (all?) modern anchors will do (and that the Mantus fits into the 'most anchors' category). What is of interest is worst case scenarios, weed in bottom, maybe a bit of mud - something that might clog up the fluke.

Testing in clean sand is not worst case.

If you want to test this

Set the Mantus and then Rocna such that only the top of the shank is just visible, drive over the anchor (you will need to use a buoy) and then pull at 180 degrees - engine in full reverse - now view what happens. You will find this can only easily be done in a dead calm (and plenty of room).

Good luck

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Old 07-05-2014, 21:51   #14
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Re: Mantus Anchor "Resetting"

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Set the Mantus and then Rocna such that only the top of the shank is just visible, drive over the anchor (you will need to use a buoy) and then pull at 180 degrees - engine in full reverse - now view what happens. You will find this can only easily be done in a dead calm (and plenty of room).
I don't think this is an ideal simulation of what happens in the real world. The pull on the anchor is not a smooth steady state, but a series of jerks that is not well mimicked by motoring. In addition there is anecdotal evidence that anchor behaviour is different when the anchor has been sitting for a while, particularly when it is subject to some side to side force.

I have done the test in the real world during thunderstorms with strong winds that have rapidly reversed (too often for my liking ) and all I can say is that I have not seen the "break out, rotate and reset" mode of action with my Rocna that I have used for many years.

I do agree that if you cannot get a good set because of poor holding ground, or anchor performance then all bets are off.

I would also emphasise that even an anchor that is good at rotating is more likely to drag while shuffling around. The holding power does go down even during a modest rotation. In many anchoring situations this weakness is one of the most common reasons for you to drag. (Just like Cheechako described) This is why I think the performance during the rotation is important.

There is a marked difference between anchors that are good at rotating (like the excellent performance illustrated by the Mantus in the photographs) and anchors that are poor or even average at rotating around. I don't agree with the tenant of your posts that most anchors are similar in this regard. The differences are easy to see underwater and I hope to post, some photographs of anchors that are performing this rotation in a much less secure manner, to illustrate the point.

This is a factor that should be taken into account when selecting an anchor. I don't think this aspect of performance has been well addressed by the magazine tests.
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Old 07-05-2014, 23:02   #15
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Re: Mantus Anchor "Resetting"

I guess part of our differences are semantics and terminology. If an anchor breaks out and moves that is dragging. Only if you are lucky will a moving anchor reset.
I don't view this as normal resetting procedure. It's not normal, or inevitable and it certainly is not reliable.

Good anchors of appropriate size in appropriate holding ground should not breakout in my view (especially while I am asleep ) and my long experience with the Rocna (and observing the performance of good anchors on other boats such as the steel Spade) indicates that this goal is achievable.

That does not mean good anchors will never drag, but accepting that your anchor will breakout every time there is a rapid 180 degree wind shift indicates to me that there is something wrong with your anchoring system.
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