Why Do We Drag Our Anchor?

[thinwater]

Modern anchors, and even most older anchors, can easily hold a boat through some pretty severe weather... unless something is wrong. Measured rode tension is just not that high compared to measure holding capacity in a good bottom, generally 5-10 times less well into gale conditions. It's not a basic lack of holding capacity that usually gets us, it is some failure in setting, rigging, or circumstance.

I've dragged because of excessive yawing and poor bottom conditions. It's been many decades, and none of the episodes resulted in anything more exciting than moving to a different location or a slight change in rigging. I've never dragged when the bottom was good, and mostly not even when it's quite bad. I've never been forced to anchor somewhere I knew was unsafe. Each time dragged it was because something simple was fundamentally wrong. I was a beginner. And it wasn't the brand of anchor I had.

Why have you dragged?


[I should have added "Anchor Fouled" to the poll list]

[Shrew]

There is no ONE answer. Common causes (in no particular order) are:

1) undersized ground tackle (chain, anchor, or both)

2) Insufficient scope (either for conditions or changes in conditions, such as tide changes or squalls).

3) Poor holding, (slime, thin sand over hardpan, etc)

[Chotu]

I have never dragged in my life. I think it was helpful to have the Internet to look at even all those years ago when I first started.

The right set up has a lot more to do with it than anything else I think. No matter what the anchor is.

A lot of it has to do with absorbing the shock loads I think.

[thinwater]

How do you KNOW what caused the dragging? It's easy to say the anchor was too small.

The first time I had anchored a beach cat just off the beach, tied the rope to one bow, and left the sails up. The wind had died and I was only going to be a little while. And I was a teenager, distracted by a bathing suit-clad girlfriend. The boat start zigging like mad and popped the anchor out. It caught again a few hundred yards away and I swam there FAST. Obviously excessive yawing.

The second time was a too-small Delta that came with the boat and mud so soft you couldn't even feel it. We moved before the wind came up. A Fortress would have worked, and I had one, but it had become too crowded anyway. I heard later that several dragged a few hours later in a squall. Glad I left.

I know a guy that snapped his chain when breaking waves arrived. It was a bad location. Yes, he could have had a long snubber, but I doubt it would have mattered.

I watched badly yawing boat get loose in a mild squall. The suddenness and that it happened at the end of a swing made it obvious what happened. The area was also thin sand over hardpan, so the anchor was probably not as well set as it seemed.
In the Chesapeake bay, poor mud is certainly the most common problem. Anchors just don't set well, and many boats come with anchors too small for the softer coves.

Internet? DOS 1.0 hadn't come out yet and expensive calculators had 4 functions.

[Kelkara]

I've dragged three times ...

1) CQR - scope too short: 5:1 scope dragged 10:1 held.
2) Excel - my fault, I anchored in a stupid place, sloping gravelly bottom, 2:1 scope at high tide ... But at least an easy exit.
3) Excel - poor holding, anchor just didn't set properly. had to reset twice ... dunno what the bottom was, but 3rd time it dug in deep.

Each time wind was somewhere 35-50ish (I don't have an anemometer).

[HopCar]

Bent Danforth anchor on a boat I had chartered. The charter company replaced it the next day with a CQR. That wasn’t much of an improvement.

I’ve had Danforths drag when they they pick balls of grass between the flukes and shank.

[Captain Bill]

I distinguish between anchor dragging and anchor creeping. Dragging I define as the anchor failing to hold and the boat moving at a fairly rapid pace. Creeping on the other hand is a slow but persistent slow movement of the anchor through the sea bed usually measured in feet per hour. I have only dragged twice. Both were the result of what I call false sets. Once on grass and once on sand covered hardpan. The grass set was anchoring at night and I did not have a good view of the bottom and it was the first time anchoring in the area. Though I backed down it seemed to be holding well but it was a bit choppy so eventually broke out. Fortunately I had lots of room to drag. The hardpan time the water wasn't very clear and I attempted to drop the anchor in what looked like a sandy spot in the grass. The tip of the delta caught on something under the sand and held, but when the wind shifted it didn't.



Creeping on the other hand was a fairly common occurrence and was attributable to type of anchor's compatibility with the bottom. For the first 10 years I owned my cat I used my Delta almost exclusively. In strong winds the boat would creep in several bottom types. It would not move in consolidated mud or deep sand, but in softer muds and loose sands it would creep in winds over 30. It might have held better if it was a size or two larger, but using a danforth type would have probably been the better solution. As a friend once put it, "Sometimes there's just no substitute for surface area". I now carry a danforth in the lazerette for just such occasions. I also changed my primary anchor to a Spade. The only time the spade has creeped was during a tropical storm in NC while up a side creek with a non-optimal bottom. The wind was forecast to switch 180 as it passed so I was afraid of the danforth breaking out. The TS didn't read the forecast and we never really got the wind switch until the winds had dropped considerably. Fortunately the winds remained down the creek and we only moved about 100 ft despite the winds being above 40kt for about 12 hours and with about 2 hours of above 50kt and a few gusts to 60.

[Mike OReilly]

I dragged a few times in my earlier years. It hasn't happened in over a decade, and that includes some fairly challenging anchoring locations and conditions.

I dragged using old CQR anchors, and once using a Danforth. The CQRs were either improperly set, or in one case, in soupy mud that just wouldn't hold. The Danforth was used in the wrong substrate (hard packed sand, impenetrable).

Since moving to my current bower (Rocna 55#) I have never dragged once the anchor was properly set and dug in. But I always lay to sufficient all-chain rode. And I take a fair bit time making sure I am well secure.

[Shrew]

Originally Posted by thinwater

How do you KNOW what caused the dragging? It's easy to say the anchor was too small.

Deduction. If scope was reasonable for depth and conditions and the anchor was undersized based on industry recommendations, it would seem a logical conclusion that the anchor size was the culprit.

If the anchor is reasonably sized and the scope was closer to 3:1, than 5:1 or 7:1 and the weather or wind kicks up, it would seem logical to conclude that insufficient scope was used.

If the anchor is sized within industry recommendations and scope was liberal, and you pullup a bunch of slime on the chain, it would seem logical to conclude that the holding is less than desirable.

There are many exceptions and few rules. Sometimes, though rare, you scratch you head and say "how did that happen".

We once pulled up a T-shirt clinging to the tip of a Rocna that refused to set.

[Be Free]

Most of the areas around me are either sand or mud and I have only had one time when my anchor did not hold. It was a cold and windy night and I was anchoring after dark in a new spot. After dragging several times I finally got close to the windward shore and tied off to some trees. I left the anchor out as well. I figured it was not going to hurt anything and I did not want to retrieve what I expected to be an anchor and rode covered in black mud in the dark and cold.


The next morning I pulled in a spotless rode but when the anchor came up it brought up a lot of small snail shells. The cove I was anchored in was covered several feet deep in tiny freshwater snail shells.

[thinwater]

Originally Posted by Shrew

Deduction. If scope was reasonable for depth and conditions and the anchor was undersized based on industry recommendations, it would seem a logical conclusion that the anchor size was the culprit.

If the anchor is reasonably sized and the scope was closer to 3:1, than 5:1 or 7:1 and the weather or wind kicks up, it would seem logical to conclude that insufficient scope was used.

If the anchor is sized within industry recommendations and scope was liberal, and you pullup a bunch of slime on the chain, it would seem logical to conclude that the holding is less than desirable.

There are many exceptions and few rules. Sometimes, though rare, you scratch you head and say "how did that happen".

We once pulled up a T-shirt clinging to the tip of a Rocna that refused to set.

Certainly yes. And no.


In testing anchors, I've seen anchors trip on debris many times but come up clean. The debris either lifted the chain or knocked an anchor sideways.



Same with sand over hard pan. Other than diving and really looking, it can only be a guess.


Scope may be the problem, but you have to do the math to ascertain if the chain actually lifted much. Depth is a big factor.


I've noticed some posters say something about what the bottom looked like. Many sailors can never see the bottom.


And of course, it is often several factors combined.



---


But so far, poor bottom is way out ahead. Often it is the one thing you can't control.

[Don C L]

The one time I dragged pretty dramatically, it was MOSTLY poor holding conditions because I am pretty sure the anchor was fouled with kelp, but I also credit poor anchor design and I would like to have had more scope out in retrospect. The bow pitching in large swells was also a factor but that is not one of the options.

[chrisr]

we're full time live-aboards and anchor a lot. we have an over-sized SARCA excel + 100% chain.

in last 2 years i can only think of dragging once. we'd been anchored for abt 3 weeks in good holding...thunder storm 30k+ with a 180 deg change of direction in the middle. we moved abt 20m before the anchor re-set.

unfortunately this put us a tad close to the neighbours so we up anchored and re-anchored. subsequently did not move again until we left weeks later.

cannot recall any other drag...but we go to a lot of trouble when anchoring plus we have good gear.

cheers,

[sailorboy1]

The past 4.5 years of full time cruising I have never dragged anchor once the anchor was dropped and set. That includes many gales and even a mini tornado. I have dragged a few times when trying to set the anchor, so me the only reason is because of the bottom.

I don't understand why people make anchoring so hard!

[Lodesman]

I've only dragged once - because we had to hang with the cool kids in a crowded anchorage, short scope, thin sand over hardpan, strong reversing current. A set-up to fail. The dragging was more like creeping as described above and more scope fixed it. Next morning, we left and went somewhere quieter. Never again.