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Discussion Starter · #1 ·
Hi All,

In my studies and getting the tackle ready for next years crusing (that will include anchoring), I pondered accross something I've not heard an answer for, or even discussed.

Lets suppose I anchor.. texbook 7:1 scope. What happens below the water when the tide completely swings me 180. Does the anchor get pulled out as it's load is now oposit the original set? Does it stay set in it's original position? All I do know is water here in the Puget Sound changes direction 4 times a day. Being at anchor for 2-3 days... what's going on down below?

Dave
 

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Like so many questions.... it depends!

If the reversals are gentle, ie little current and little wind, you may not even straighten out the chain.. but obviously if there's good breeze or a lot of current you will pull around and potentially swing in your full radius circle. The anchor might simply 'swivel' in place, or be 'tripped' and reset itself.

Depends, too, on the bottom surface, anchor type, etc etc...
 

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TROUBLE
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That happens all the time in Florida and the Bahamas too. I assume the anchor just re-sets itself? Sometimes, I wonder if there is even much tugging on the anchor when the current turns against the wind. It's a pain when the chain is rubbing on the topsides, or the mooring is banging against the side of the boat.

Ralph
 

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As was indicated, it depends on the conditions. In all of the interminable anchor squabbles a major consideration was how the anchor handled resetting itself. That is almost as important (in some cases more important) the ultimate holding ability. In most places that I have been, the current switches slowly enough that the anchor can turn without unsetting (is that a word?) itself. Have been in a place where there was a solid wind from one direction (around a hill) that would reverse almost 180° around the hill and come from the stern. The boat would sail over the anchor and unset. Half an hour later after I reset (it was a Danforth as I remember), the process would reverse. It can be a problem.
 

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Time to put on face mask,fins wet/dry suit or better yet if certified some scuba gear and go watch your anchor..or the 'cats meow' don a rebreather and sit down there for a complete tide cycle change..:}
 

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islander bahama 24
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Dave in eagle harbor for a week last summer the anchor never flinched and the winter before in poulsbo with some really bad winds and tidal same thing for me with a fortress and 27 ft of chain and the rest rode never a problem for me.
 

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Discussion Starter · #8 ·
Like so many questions.... it depends!

If the reversals are gentle, ie little current and little wind, you may not even straighten out the chain.. but obviously if there's good breeze or a lot of current you will pull around and potentially swing in your full radius circle. The anchor might simply 'swivel' in place, or be 'tripped' and reset itself.

Depends, too, on the bottom surface, anchor type, etc etc...
Ron,

Have you ever been "un-stuck" or had any issues up at your end?
 

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Ron,

Have you ever been "un-stuck" or had any issues up at your end?
I think I can honestly say that the only times we've 'dragged' were times we were lackadaisical about setting in the first place.

We started having more trouble than usual setting the anchor (a 35# CQR) once we got a Max prop.. went to a Mantus this year with no problems at all.

We have occasionally had to release a stern tie or rearrange the tie point in a building overnight breeze but have been lucky enough that we've never seriously 'moved' overnight. Certainly haven't had an issue directly related to the tide changes involved.
 

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I would not trust a danforth style anchor around her to reset if the anchor did do a 180. Some of the plow, claw styles will reset most 99% of the time. Generally speaking, with a boat length or two of chain, the rest rope, you should find yourself doing fine. Assuming you do get the anchor initially set per say.

Marty
 

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A bad case, more common on the east coast, is a powerful squall. Typically the prevailing wind will be very light from the south, and the gust front will be 50 knots from the north west.

My practice is to set the anchor against where I believe the blast will come from. It will easily stay set against a 5-10 knot southerly, and be prepared for that 50 knot north west.

I might set 2 anchors, in different directions, if space for re-setting is limited or if the bottom is bad for resetting (weeds or shell).
 

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Discussion Starter · #12 · (Edited)
A bad case, more common on the east coast, is a powerful squall. Typically the prevailing wind will be very light from the south, and the gust front will be 50 knots from the north west.

My practice is to set the anchor against where I believe the blast will come from. It will easily stay set against a 5-10 knot southerly, and be prepared for that 50 knot north west.

I might set 2 anchors, in different directions, if space for re-setting is limited or if the bottom is bad for resetting (weeds or shell).
Now there's an idea! :) If one knows their area you could plan ahead.
 

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.

My practice is to set the anchor against where I believe the blast will come from. It will easily stay set against a 5-10 knot southerly, and be prepared for that 50 knot north west.
I do something similar sometimes. If the wind is blowing me off the beach, I might still set the anchor twards the beach (180 different than the wind) because I'd rather be blown out to sea than blown onto the beach.

Typically I'll do this if the wind is light. If there's a strong wind, I'll set it in the direction of the wind.

Regarding the OPs question about what actually happens, little is known for sure. The conventional wisdom is that danforth style anchors might reset, or might pivot and remain buried, but could flip out and not reset. This DID happen to me in soft mud. I scuba dove the anchor and found it laying flat on the top of the mud! :eek: I had power set it and was certain it was holding just 2 days before.

MedSailor
 

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Marty, my 20-pound Danforth stays put in many locations where my 42-pound CQR drags. This winter, I'm going to add another 100 feet of chain to the system so I can go to a 10 to 1 scope.

Gary :cool:
 

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Gary,

Glad you can get them to work. I can not even get one to hold a turn/start mark bouy! Altho my 4lb claw holds them fine!

There are a couple of boats in the race club I used to belong to, a lot had fortress and danforth anchors, many times took 3-4 try's at anchoring themselves. I drop a 9lb fast set with 6' of 3/8" chain and 7/16" 3 strand, I'm set in my 28LOD 6500 lb boat first try! I do better with my 7.5kg original bruce.......Even with wind and tide changes they reset or stay where they were easy enough. again, no backing down on them......Then again, we have upwards of 14-15' tide changes on the two worst ones, 7-8' on the shallow 2 changes........tides can be an issue!

CQR's do not seem to do so well around here either.

Marty
 

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while cruising the us/bvi, our catamaran was equipped with a cqr and a danforth. never used the cqr, but the danforth was fantastic. only one dragging incident and that was (my) operator error. not enough scope.
 

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It is not a silly question at all.

How an anchor responds to a change in the direction of pull is a very imprortant characteristic. If the force is only mild the anchor will not change at all, but in many circumstances the anchor will need to rotate.

The anchors that are good at changing direction will remain buried and simply "shuffle" around to the new direction without otherwise moving (providing they set and the substrate is reasonable). Anchors that are poor in this regard develop a very high list, sticking one fluke high in the air. From this position they are at high risk of breaking out completely. If this happens they will often reset, but an anchor design that can remain well buried while changing direction is much more secure.

These are some underwater photos of my Mantus anchor rotating about 160 degrees. This anchor rotates very well, remaining almost level during the whole process. Other than the rotation there is no other movement. There are a couple of stones that act as a reference mark.











 

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As you contemplate all the above info, add the concept that the boats around you may not behave the way you do. For example, those on all heavy chain in light air, will just rotate around the catenary of the chain, while those on all rode will swing around and repull against their anchor. IOW, you won't all stay in the same relative position. This is where art meets science in anchorage positioning.

One good way to get a sense of this is to attach a light buoy ball and line to your anchor. This is usually done to secure a rope to help dislodge a stuck anchor, but it can be a very interesting way to see how you swing about your set.
 

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Time to put on face mask,fins wet/dry suit or better yet if certified some scuba gear and go watch your anchor..or the 'cats meow' don a rebreather and sit down there for a complete tide cycle change..:}
Or, if you're lucky enough to make it down to a place like the Bahamas - where most typically anchor in shallow, incredibly clear water - you can simply tool around any popular anchorage in your dinghy with a look bucket... Particularly in the wake of a frontal passage, when everyone has swung 180 degrees or more on their hooks, an exploration of a place like Elizabeth Harbor in Georgetown will reveal a great deal about how different anchors are likely to behave, as the pattern is often still clearly written in the sand below, just like the photos from noelex77...
 

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We run into this pretty often at Santa Cruz Island where the wind shifts 180deg many times a day on the west end. Our old Danforth set very well in the sandy bottom but nearly every time we raised it it would have three or four wraps of chain around the shafts and flukes. Last week we used our manson supreme. It took all the spins and turns in stride, never fouled and remained set all weekend. My only complaint was that we never really felt it set.
 
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