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Old 25-07-2016, 17:24   #1
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Setting an anchor when tides do a 180 degree change

I have been wondering about a specific aspect of anchoring. Here are two things I have often read:

1. Where a tide will flow one way then the other, an anchor is needed that will reset easily.

2. When setting an anchor, best to power set it by reversing the motor.

What I am wondering is if an anchor needs to be set by reversing the motor, what happens at change of tide when the anchor pops up out of the bed and has to reset itself? Does the motor have to be used every tide change to keep power setting the anchor?

And, I have also read about some anchors burying themselves very deeply, so do these anchors actually come to the surface when the tide does the 180 degree change or do they simply twist deep under the sand/mud?

With power setting an anchor, does it go deep then twist around at tide change, not actually needing resetting?

I apologise if these questions seem stupid, I am very interested in how anchors work.
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Old 25-07-2016, 17:33   #2
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Re: Setting an anchor when tides do a 180 degree change

There is a huge thread titled "photos of anchors setting" or something close to that. It is full of anchoring wisdom. If you wade through that thread, you'll be an expert.
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Old 25-07-2016, 17:34   #3
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Re: Setting an anchor when tides do a 180 degree change

The forum's "Doctor of Anchorology" has just the thread/dissertation for you.

http://www.cruisersforum.com/forums/...ng-126073.html

Its a long one but he covers a lot of the questions you have.
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Old 25-07-2016, 17:40   #4
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Re: Setting an anchor when tides do a 180 degree change

Most I have seen just hold when the tide reverses, the anchor never changes, it just holds backwards. But if the tide or wind are too strong it may break free and likely will not reset.
That is the problem with anchors. In that kind of tide change two anchors set on one rode may be best. Two, not on the same rode, often end up in a big cockled mess twisted. (don't ask how I know this!) Bow and stern anchors may force one anchor to drag loose from the pressure, then it's a very messy fire drill (don't ask how I know this!) I usually just set one anchor well and pay attention.
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Old 25-07-2016, 17:42   #5
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Re: Setting an anchor when tides do a 180 degree change

As someone who anchored in tidal streams almost exclusively, with currents to 3 knots and winds typically 20-25 mph in summer. For mud, clay and sand, most anchors will bury enough so that they rotate in place 4 times a day. A Bruce or danforth will bury pretty deep. The new gen anchors bury well also.

Hard sand or rocks can be tricky as can a sudden 180 degrees wind shifts. Tide changes happen pretty slowly, over about an hour. I have anchored on one place for well over a week at a time without resetting. But that was with a bruce and now a Mantus.

While the danforth I used for a week in 25-35 knot winds held well enough with tide change, it popped out far to easy on anchor retrieval. I did reset the Danforth every few days. The Bruce and Mantus I never worried about. Both required the boat engine to break them free with the Mantus taking a slight bit more force/time to break free. The mantus sets in a few feet which is quite pleasant too. My old bruce set in about 10 feet in mud and the danforth, sometimes dragged a bit before setting.

One area to watch for is when tides and winds are almost opposite of each other, This will cause the boat to dance around the anchor in loops for the time the tides are opposite the winds. Best to have winds at 90 degrees to tides, or close to it, when ever possible.
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Old 25-07-2016, 17:54   #6
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Re: Setting an anchor when tides do a 180 degree change

Consider a Bahamian moor if anchoring where there are strong tidal effects.

Bahamian Mooring : by S.Bryant [Anchors and Anchoring] - VisitMyHarbour articles
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Old 25-07-2016, 18:03   #7
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Re: Setting an anchor when tides do a 180 degree change

Quote:
Originally Posted by sailorchic34 View Post
One area to watch for is when tides and winds are almost opposite of each other, This will cause the boat to dance around the anchor in loops for the time the tides are opposite the winds. Best to have winds at 90 degrees to tides, or close to it, when ever possible.
Try this:

https://www.catalina36.org/forum/sai...lesson-learned

Sometimes a kellet or sentinel is a good choice for reversing tides & wind.

Good luck, it takes some investigating, and finding the USING the right anchor.

Danforth anchors are GREAT for one way pulls. Think about it.

Enjoy.
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Old 25-07-2016, 21:20   #8
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Re: Setting an anchor when tides do a 180 degree change

If you leave the boat unattended, better on a mooring with the tidal flows you have up there.

We're on all chain, so use less scope than you are forced to, but still, in rivers, we up anchor and re-set every few days. The water is murky, sharky and/or crocodiley, and we've never dived to try and see what it does, so don't know if our anchor "shuffles" like noelex shows in his thread, "Photos of Anchors Setting." Very highly recommended viewing.

Ann
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Old 26-07-2016, 01:50   #9
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Re: Setting an anchor when tides do a 180 degree change

Normally setting the anchor once after dropping is enough. The setting process drives the flukes into the seabed. If you choose an anchor design that is good at rotating, and it is a reasonable substrate, the anchor will remain buried and set as it rotates, so there is no need to reset the anchor with each change of direction. It should stay buried.

As Cheechako has pointed out, with a tide change alone there is often not even enough force to make the anchor rotate. The boat and chain will move to the other side of the swing circle, but the anchor will remain pointing in the same direction.

The greatest concern is with anchors that are poor at rotating. The worst performers seem to be the Danforth style of anchors. Even these models will often rotate successfully remaining set. Unfortunately, on some rotations this style of anchor develops a high list and breaks out, or almost breaks out. Even if this occurs the anchor will often reset itself to the new direction of pull, but it is less reliable than an anchor that can stay buried with its flukes engaged with the seabed throughout the rotation.

An easy solution is to only use a Danforth style of anchor when the direction of pull is going to be reasonably constant. Unfortunately, this rules out this style of anchor as normal primary or bower anchor. There are other solutions if you really want to use a Danforth style anchor, such as using two anchors (although you can still have a reasonable amount of rotation in many circumstances), or periodically testing and resetting the Danforth anchor as Sailorchic described.

Frankly, with the wide range of anchors that rotate well, these steps should be unnecessary these days. Get a good quality primary anchor, set it once, and in a reasonable substrate you can have every confidence that it will rotate without any problems or intervention.
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Old 26-07-2016, 03:00   #10
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Re: Setting an anchor when tides do a 180 degree change

Not to take away from the graciously submitted pics of anchors already mentioned. But you might also want to see some anchors in action live. As many here are fans of Panope's vidoes. Which show various kinds of hooks doing their thing. This is one link, but he has a channel with lots of them.
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Old 26-07-2016, 03:09   #11
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Re: Setting an anchor when tides do a 180 degree change

Thank you for your stimulating points.

I had to move my boat today from being anchored to my mooring and had a little think about my anchor as I was cleaning the mud off it. It is a Manson Boss which is similar to many of the newer types of anchor. What I noticed was that the shank was relatively thin and the flukes relatively big. I also noticed the angles. I know the size of fluke and shank is obvious but what I was thinking about with the relative difference and the angles was that with the anchor well dug in, it would take less effort to twist it in situ than to pull it out.

That's what Noelex77 and some others said, the anchor spins while staying dug in.

With the anchor dug in and the pull on the rope turned 180 degrees, I would expect that the flukes would resist rising to the surface more than the shank and edges of the flukes would resist twisting around.

As Cheechako said, sometimes the force is not strong enough to spin the anchor around but it still holds (more force would likely spin it).

Noelex77 pointed out that some anchors such as Danforth style are not so good at rotating. When I mentally compare the Boss anchor I have with a small Danforth type I also have, I can see that if both were buried in mud and then pulled in a way to try and spin them around, the geometry and angles of flukes and shank would likely make the Boss easier to spin.

Certainly very interesting. Well, I am finding it so.

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Old 26-07-2016, 03:13   #12
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Re: Setting an anchor when tides do a 180 degree change

What's a tide? Med sailing
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Old 26-07-2016, 06:51   #13
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Re: Setting an anchor when tides do a 180 degree change

You can view some of the simulated anchor rotation tests, which are typically done on beaches, by visiting the web sites of the various anchor manufacturers. Who also tend to have filmed underwater examples of the same thing. Though, of course, unlike noelex77 & Panope, anchor makers are biased, & doubtless leave some of the more unflattering film footage on the cutting room floor.
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Old 26-07-2016, 08:57   #14
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Re: Setting an anchor when tides do a 180 degree change

I fish in the Humber in Yorkshire England and you will not find many places with a worse riptide but I just drop anchor, let out what I think is an appropriate amount of rope and leave my 34ft Eurobanker to it. Obviously from time to time I check for drift but it never happens. Same when tide turns, just leave it alone to look after itself. 24KG Danforth, 20ft 1\2" chain rest rope. The hardest work is getting the bloody thing up again. Mechanical winch.
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Old 26-07-2016, 09:46   #15
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Re: Setting an anchor when tides do a 180 degree change

Mantus re-anchoring 44 lb. perfect score



Instructive....Great visibility as to how the anchors behave under water.
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