Why does my anchor hold in wind from the opposite direction... - SailNet Community
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post #1 of 29 Old 03-05-2010 Thread Starter
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Why does my anchor hold in wind from the opposite direction...

I've been wondering for a while now, what is happening to my anchor as my boat swings around and forces it to hold from a different direction? I cruise mostly in the Puget sound, Canadian Gulf Island and up the inside passage. Here, 10-15ft tide swings from high to low are a very common occourance. This means that even on days when the wind doesn't shift around, the tide flow will force the boat around it's anchor several times in a day.

If I set my anchor in a north south direction for example, with my bow facing north. What happens to my anchor when that unexpected south wind comes along? Does my anchor slowly spin around while remaining flat and buried? Does it pull out and reset? Does it remain buried in the same orientation and just hold a pull from the opposite direction in that position?

Has anyone ever dove their anchor and seen what is really happening, or anchored in clear enough water to observe this? I've had many a time where I anchored expecting wind to come from one direction and instead it comes from another. Anchor has (knock on wood) always held (usually a bruce or fortress). What do you suppose it is doing down there?

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post #2 of 29 Old 03-05-2010
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I have observed what you are talking about several times in water this is clear enough to see. Like you, I spend a lot of time in tidal areas with current up to 3 or so knots right by my mooring. From my observations, there are two major things that will determine what will happen, the force you put from the new direction and the anchor type.

In light air, you don't put enough force on the anchor to pull it free from how it was previously set. This is a little worry to me since if the wind picks up a little, the anchor will pull out with relatively little force (I have watched this) and you are dependent on it resetting.

The other thing is that it really depends on the anchor you are using. My experience with danforth anchors is that they pull out and then need to reset. Some people report that they tend to foul themselves although I have not observed this. What I have seen of claw anchors suggest that they tend to flop over and reset quite quickly although a few times they have stayed buried and pivoted. I really don't have any experience with CQR anchors in this situation so I can't comment on them. The new generation anchors (Rocna, Manson Supreme) use their roll stability as one of the selling points. This means that they stay buried and pivot in place.
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post #3 of 29 Old 03-05-2010
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Are different bottom types more or less conducive to anchors automatically reseting? For example I could see getting a good set in sand with a Danforth, and then the anchor pulling out and not getting a good bite, whereas if it were mud it might reset more easily. Or is the "resetting" ability of a given anchor in a given holding the ground basically the same as its setting ability?

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post #4 of 29 Old 03-05-2010
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I think that the newer designs are a lot better in reversing current/wind situations. The ability of an anchor to re-set is not quite the same as its ability to set, though they are related. When an anchor sets, the boat is backed down intentionally and forces the anchor to set. When an anchor re-sets, it depends a lot on the anchor's design.

Some, like the Manson Supreme, Rocna and Spade, are relatively roll stable, and will probably pivot in place, rather pull free completely. Others, like the Claw/Bruce and Danforth/Fluke designs will generally pull free and need to reset completely.

One problem with the fluke anchors, especially the aluminum Fortress types, and multihulls, is that the anchors can "kite" if the boat gets moving once the anchor breaks free. This is more common with the lighter multihulls which accelerate faster, but can happen with monohulls. Another problem with the fluke anchors is that mud, small rocks and such can

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Last edited by sailingdog; 03-05-2010 at 04:47 PM.
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post #5 of 29 Old 03-05-2010
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One of two things is happening:

1. The force pulling against your anchor is not great enough to dislodge it.

or

2. The force has been of sufficient strength to dislodge it, but not great enough to prevent it from resetting itself.

As previously mentioned, some bottoms really lend themselves to holding and resetting, like sand and mud. Some anchor designs reset quickly if they're dislodged, like Bruce, Delta, and CQR.

In my experience, once you get a Danforth set properly, it will hold forever. However, if it ever dislodges, it's off to the races you'll go.

P.S. I did not offer anchor names to start a debate on which is the "best" one. I've only mentioned those I've used personally.

P.P.S. I use my Delta almost exclusively in the Bahamas and Keys, with a Bruce on the roller waiting for a muddy bottom (like the Hudson River) where it holds like crazy.
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post #6 of 29 Old 03-05-2010
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Yeah, any time we start talking about anchoring there's a danger it will "devolve" into a debate about which is best.

I'll just say I've experienced a fluke-style anchor popping out (even when properly set) as a result of an instant 180 degree wind shift followed by severe thunderstorm. That said, it did actually reset eventually, and there was no harm to boat or crew (perhaps my shorts though).

I've experience similar conditions with a Rocna, and it doesn't seem to move much. It either resets faster, or never pops out. I don't know, as I can't see it in the Bay. A claw-style seems to be similar in my experience. I haven't used a Delta, and never experienced those shifts while using a plow-style.

For the record, as AlanBrown mentioned, I'm definitely not arguing any one anchor is better, just describing my experiences with them in relation to the original post.

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post #7 of 29 Old 03-05-2010
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This is why I have the following anchor setups.

Danforth - 6 ft chain - mushroom - tackle

We set marks and boats down in Cascade Locks, OR all the time for running sailboat races down at CGRA. This is the entry of the columbia river gorge for Hood River. We have light westerlies in the morning so that the current drags everything down river. Then in the afternoon the wind pickups to the point that it over takes current or is neutral. This has the end result of pulling a normal danforth out, and in all different directions.

With the addition of a mushroom it helps keep the pull direction of a danforth down even if you rotate on it.

I use these anchor setups on everything. Its a little more to deal with but really works great. When I cruise later in life I will have always have a couple of mushrooms with shackles that you can put them on existing anchor setups a few feet from the anchor.

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Last edited by mackconsult; 03-05-2010 at 05:49 PM.
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post #8 of 29 Old 03-05-2010
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Mack: doesn't several feet of chain between rope and anchor have the same effect as the additional mushroom you describe?

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post #9 of 29 Old 03-05-2010
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Not really, he's using the mushroom anchor as a kellet or sentinel.

Quote:
Originally Posted by AdamLein View Post
Mack: doesn't several feet of chain between rope and anchor have the same effect as the additional mushroom you describe?

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post #10 of 29 Old 03-05-2010
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Really good thread. We need some underwater video of anchors pulled at the opposite angle from which they were set, so we can see what's going on.

Any of our members in the carribean setup to take underwater video while their significant other takes the helm and (slowly) powers the boat upwind to break the anchor free and then to reset again?

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