chain wrapping around anchor

[boatman61]

The best way without an engine in light winds is to sail downwind with just the main keeping speed as low as possible, drop the hook in your chosen spot and then put your helm over hard as the chain runs and release the mainsheet to allow the main to luff asap.
Chain lays itself and boat slowing as you lose windage and lock the chain will bed in the hook if bottom is decent.
Reason for helm hard over is the chain does not scrap your hull.. always worked well for me, even solo.

[Seamentress]

Ok, I don't usually post much on here, but read a lot!
Firstly, I live aboard, here in La Paz, I am one of the small community who make up the Mogote fleet. We usually have two tides a day here, and on big Spring tides, the current can reach 5Kts, that's 5 in and 5 out, I arrived here in 2011 and have seen 2 hurricanes come through and numerous storms.a
I am also a member of our hurricane response team.
I have attended and helped recover numerous boats during that time, probably upward of 50, so I think I can contribute to this discussion with a higher than average degree of experience.
First to the question of the Bruce anchors.
In my experience the Bruce is the anchor giving the highest failure rate in these conditions, in almost every case when a dragging Bruce anchor has come up, it is inevitably wrapped, often in a huge ball of chain, several times it has been necessary to lower the ball into a volunteers dinghy to unwrap it, being too heavy and awkward to get aboard the owners vessel.
So, Bruce anchors, in my experience are prone to fouling when a boat swings from one end of the scope to the other.
I have talked to the owners about how the anchor was set initially, and almost all of them use their normal methods, and scope. One of the common denominators comes to mind, that most of them don't allow enough scope out to bury the shaft when setting the anchor, this leaves a small enough gap between the sea bed and the anchor shaft for the chain to get wrapped, after several tides, the anchor eventually gets pulled out backwards and the boat is off to either the nearest neighbour or sandbar whichever comes first.
Also a greater scope of 7:1 or more helps to minimise this issue, I have seen two boats anchored close to one another with exactly the same ground tackle, one dragged in a Chubasco storm which came up very suddenly, the other was secure! The only difference we found was one was on a long scope the other on everyone's usual of 4:1 / 5:1.
I have never seen a Rocna anchor behave in this manor, and there are plenty of users here.
The principal difference between these two anchors, is the roll bar on the Rocna, it keeps the chain from going underneath that small gap and prevents a wrap, so my advice would be to get a roll bar welded to your existing Bruce if you are anchoring in an area of tidal change, or swap it for a Rocna, and put out more scope, especially if you are sticking with the Bruce. Good Luck, stay safe!
Paul

[sailorchic34]

I have had my Bruce wrapped in chain a couple times. It all happened at the same location. In my case it's hard packed sand and the Bruce would not penetrate far enough. Generally if the Bruce is buried in mud or light sand, it's not going to get the chain wrapped around it.

I use a variation of boaties method. I keep a 1.5 ish knot way on the boat. When I deploy the anchor. I have the amount of rode needed on deck and wraped around the post, prior to arrive. It lays the rode out and sets the hook all in one go. Mind you I have a pretty strong Samson post (hard wood no less) that's anchored to the hull.

Any anchor with a shallow bury, can get chain wrapped when winds and tides are opposite of each other.

[boatman61]

Originally Posted by Seamentress

]Ok, I don't usually post much on here, but read a lot!
Firstly, I live aboard, here in La Paz, I am one of the small community who make up the Mogote fleet. We usually have two tides a day here, and on big Spring tides, the current can reach 5Kts, that's 5 in and 5 out, I arrived here in 2011 and have seen 2 hurricanes come through and numerous storms.
I am also a member of our hurricane response team.
I have attended and helped recover numerous boats during that time, probably upward of 50, so I think I can contribute to this discussion with a higher than average degree of experience.
First to the question of the Bruce anchors.
In my experience the Bruce is the anchor giving the highest failure rate in these conditions, in almost every case when a dragging Bruce anchor has come up, it is inevitably wrapped, often in a huge ball of chain, several times it has been necessary to lower the ball into a volunteers dinghy to unwrap it, being too heavy and awkward to get aboard the owners vessel.
So, Bruce anchors, in my experience are prone to fouling when a boat swings from one end of the scope to the other.
I have talked to the owners about how the anchor was set initially, and almost all of them use their normal methods, and scope. One of the common denominators comes to mind, that most of them don't allow enough scope out to bury the shaft when setting the anchor, this leaves a small enough gap between the sea bed and the anchor shaft for the chain to get wrapped, after several tides, the anchor eventually gets pulled out backwards and the boat is off to either the nearest neighbour or sandbar whichever comes first.
Also a greater scope of 7:1 or more helps to minimise this issue, I have seen two boats anchored close to one another with exactly the same ground tackle, one dragged in a Chubasco storm which came up very suddenly, the other was secure! The only difference we found was one was on a long scope the other on everyone's usual of 4:1 / 5:1.
I have never seen a Rocna anchor behave in this manor, and there are plenty of users here.
The principal difference between these two anchors, is the roll bar on the Rocna, it keeps the chain from going underneath that small gap and prevents a wrap, so my advice would be to get a roll bar welded to your existing Bruce if you are anchoring in an area of tidal change, or swap it for a Rocna, and put out more scope, especially if you are sticking with the Bruce. Good Luck, stay safe!
Paul

[/QUOTE]

I like Bruce anchors but then I dont do all this scope crap you Yanks rave on about.. I anchor old school as taught to me by an old salt back in the 60's..
I go by boat length x 3 plus depth.. wind kicks up to F7 or more I let out another boat length.
So a 30ft boat hangs on 90ft of chain plus say 20ft depth, and I sleep soundly.

[saltytar]

[QUOTE=boat_alexandra;2902019]After dragging I found the chain wrapped around the anchor. I have a bruce style anchor but I have heard other types can do this.

This happens from anchoring in a tidal area or with variable winds, and it's relatively rare but has happened to me a few times.

Are there any types of anchors that are immune to this or any way to prevent it other than using multiple anchors?[/QUOTE

We've had very good luck with our CQR but the YouTube channel Sailing Emerald Steel has a great anchoring video that discusses the pros and cons of some anchors. https://youtu.be/4UADSoAYjX8

[TrentePieds]

Hm... that seems a bit short to me. I like this: 5 ft from roller to water, + 5 ft draft + 5 foot clearance at low water + 16 ft rise of tide = 31 ft to allow for. At scope of 7 that comes to 217 ft = 36 fathoms (app.) which I measure (literally) by my outstretched arms (= 1 fathom) and flake on deck. I pay it out through my hands as the boat pays off downwind thus getting a feel for what the hook's doing while keeping the rode tiddly on the bottom. As Sailorchick sez: With the bitter end already made fast to the samson, the inertia of the boat sets the hook, and the scope is long enuff to let the Bruce shank lie flat. In sand, the moment arm twixt C of E of the flukes and the shackle 'ole in the shank tends to bury the shank when the strain is on the rode.

TP

[Seamentress]

Hi Boatman 61,
Well, I'm just relaying my experience of recovering failed anchored boats here in a high tidal area, I'm not knocking Bruce anchors or their users. Your method might work well here, it might not, who knows.
But one thing I'm not, is a Yank!!
I'm a retired Brit ex pat, a Black Country Boy. Nails ain't in it! You continue to sleep well, I wish you all the very best.
Paul

[boatman61]

Originally Posted by Seamentress

Hi Boatman 61,
Well, I'm just relaying my experience of recovering failed anchored boats here in a high tidal area, I'm not knocking Bruce anchors or their users. Your method might work well here, it might not, who knows.
But one thing I'm not, is a Yank!!
I'm a retired Brit ex pat, a Black Country Boy. Nails ain't in it! You continue to sleep well, I wish you all the very best.
Paul

Not saying your a Yank.. just that they tend to talk scope whereas most I know talk length and only use chain.. we tend not to read the mags.. or gave em up 40yrs ago..
I only tolerate rope rode on OP's boats.
TP.. thats usually good enough with all chain.

[Davo1404]

Originally Posted by gamayun

One thing a friend told me when I drop my anchor in shallow water is to not drop the chain too quickly before the boat starts to drift back because the chain can pile up on the anchor. Maybe this is one way it could get itself wrapped before the anchor is set. Just a thought.

Exactly right. This happened to us just recently. Thank goodness it was calm, when I retrieved it the chain was wrapped around it. Definitely wouldn't have buried. Moral of this is if you are anchoring in say 10 m then once you have 10 metres out start reversing letting the chain out as you go. Of course if you have tide or wind then you shouldn't have to reverse. We use a Rocna.

[thinwater]

Originally Posted by boatman61

Not saying your a Yank.. just that they tend to talk scope whereas most I know talk length and only use chain.. we tend not to read the mags.. or gave em up 40yrs ago..
I only tolerate rope rode on OP's boats.
TP.. thats usually good enough with all chain.

You either heard him wrong (most of those type formulas used X times water depth plus a factor) or he was wrong.


The length of the boat really has very little to do with anchoring and nothing to do with geometry.



On the other hand, if I use "water depth + freeboard" instead and add a 20- to 40-foot factor, 3 x (5+3) + 30 = 54 = 6.5:1 scope. I might go longer than that, because 75 feet is still nothing, but the formula makes sense. It also gives pretty much the same result as the formula you suggested, for your case (3 x (20+3) + 30 = 99 = 4.3:1 scope. The result is somewhat less scope, but with all chain, in deeper water, in settled weather, that's OK.



I suggest " 3 to 4 x (depth + freeboard) + 30 to 40 feet" as a reasonable approach in settled weather. If I expect a real storm I'd increase it at lease 30%, which is OK, because in a real storm there generally arn't many other boats around (but not always). We get thunderstorms a lot in the summer, so 60 knots is often plausible. A simple formula is fine, so long as you understand where it comes from.

[boatman61]

Actually 90ft + 20ft from roller = 110ft..
Funny thing is when I have mentioned my anchoring guage in the past on here I have been slagged off for using to much 'scope' and hogging the anchorage.
Cant win..
I should add.. This is not allowing for tidal factors.. for example if anchoring outside the inner breakwater at Cherbourg I would add another 30ft for hw/lw fluctuations, Poole 15ft, Alcudia in the Med I would not bother.

[thinwater]

Originally Posted by boatman61

Actually 90ft + 20ft from roller = 110ft..
Funny thing is when I have mentioned my anchoring guage in the past on here I have been slagged off for using to much 'scope' and hogging the anchorage.
Cant win..

Actually, The number is very reasonable for 20 feet. Let them slag on!


Factors can always be adjusted. My point is that the formula should be based on the depth of the water (relevant) instead of the size of the boat (less relevant). But I'm guessing you anchor in 15-30 feet of water most of the time. On the other hand, I anchor in 4-7 feet with very limited tide, because that is common here.

[boatman61]

Originally Posted by thinwater

Actually, The number is very reasonable for 20 feet. Let them slag on!


Factors can always be adjusted. My point is that the formula should be based on the depth of the water (relevant) instead of the size of the boat (less relevant). But I'm guessing you anchor in 15-30 feet of water most of the time. On the other hand, I anchor in 4-7 feet with very limited tide, because that is common here.

Size = weight..
Bludi multis..

[thinwater]

Originally Posted by boatman61

Size = weight..
Bludi multis..

And weight of boat = scope? No, weight + windage = weight of anchor, with scope being unrelated (if the chain is matched in strength to the load, and thus weight by logical extension, then the catenary available and required does not change).


This isn't a multi-mono thing, this is a maths/geometry/physics thing. The scope used by a multi-thousand ton ship is on the same order as a 20 boot boat. That is what the maths and experience say. If you apply your formula to a large freighter you also get a comical result. A panmax ship would need to lay 3x950 + 50 = 2900 feet of chain in 50 feet of water, or a scope of over 40:1. They don't.



No, it is not about weight or the length of the boat, it is about the depth.

[Alan Mighty]

Originally Posted by thinwater

No, it is not about weight or the length of the boat, it is about the depth.

Or it could be about BOTH length of the ship (as a proxy for windage etc) AND the depth of the water.

I've noted before (http://www.cruisersforum.com/forums/...ml#post2869814) the common practice of cargo ship masters using the scope formula of:

Length of chain = 3H + length of hull; (where H = water depth + freeboard to anchor hawse)

That formula is often simplified to:

Length of chain = 3H + 90; (where Length is measure in metres - the 90 representing 90 metres as a nominal hull length of a cargo ship)

The UK Admiralty used an approach that focused, like Thinwater, only on H.

I've attached a graphic from one of the more common guides to ship handling in E Asia that compares the Japanese formula to the UK Admiralty formula. See: JCA Guide to Ship Handling Fig 3-2.jpg, about 115 KB