Anchoring with 4:1 Scope?

[smacksman]

With a Force 8 forecast I thought it would be a good idea to lower a 28lb. weigh scale weight down the rode to increase the horizontal pull. Worked well till the whole lot dragged anyway. Terrible lesson learned was trying to pull the 28lb. weight on board from the bows of a yacht bouncing about in a gale in the pitch dark. Never again.

[Mancora]

It’s a judgement each time. The weather, swells, bottom holding ability, your equipment (anchor type, anchor size, chain size), risk of thunder storms, plans to be away from boat or not etc.
I use a rule of thumb ratio: shallow water around 5:1 down to 3:1 in deep water. But again depends on many factors.
(I’m using a Rocna 33 kg with 10 mm chain for a 51’ monohull of approx. 17 mt displacement).

[Bill_Giles]

I was anchored in the Canaries in fairly shallow water. We got the anchor touching and fed out the chain as we backed off. The boat was 55ft so helm/bow comms were a bit difficult. Anyway we had a nice night at anchor and had a swim off the boat in the morning. Someone duck dived to the anchor and found that the anchor was on its back and next to it was a massive heap of chain. Luckily it did not blow up in the night.

[john manning]

Early in my time of owning larger vessels I had several eventful nights while anchored. Those days are over and long rodes rule my anchoring.

The most useless thing for a yachtsman when anchoring is rode still in the locker.

[Bill_Giles]

Absolutely right. I’d feel really foolish if my lifejacket was hanging up in my locker after I drowneded. (Old English: I am drowning, I am drowned, I am drownded).

[Capt. Mike Maurice]

Every boat I deliver has it's own anchoring system. I have generally zero input on what I get and have to use what there is.
Anchoring is part Art, part Science. If you want the best analysis go read Earl Hinz's book on Anchoring. More weight, more chain, more rode, is good. Bottom conditions and range of tide plus wind and current changes add to the complexity.

Or to put this way:

"There are more things in heaven and earth, Horatio,
Than are dreamt of in your philosophy", Hamlet.
When it comes to anchoring, that goes double. Most of the time no matter what you do you won't drag. And, once in a while, you will get bit, big time.

Here is the rough rule of thumb. Put the anchor out. Make sure you set it. Put out more scope, as much as the situation will allow.
Keep an eye on the wind, current and tide. If they change dramatically, expect trouble. If you don't get any, count yourself lucky. If you have it all out and you are dragging and the wind is approaching 100 knots, grit your teeth and hope the anchor snags before you go aground or drag out of the anchorage.And, make an oath that you will read the book again and make improvements in your system for the next time.

That's what 60 years of dragging and not dragging has taught me.

So, there is a mud bank just inside Hinchinbrook Entrance, Alaska. It's about 1/4 mile long. With all our rode out, we dragged nearly the entire length during a night blow that approached 100 knots. We were the only small craft anchored in the area and unlucky enough to be there. Another 100 yards and we would have dragged into 200 feet of deep water and the anchor would have let go...
Needless to say, we didn't get any sleep that night.

[MVDarlin]

Years ago when I first came to the Sea of Cortez I woke at 2am to find my 43 ft trawler drifting out to sea after setting my trusty 45# CQR anchor offshore on a sloping beach in 30 ft with 5:1 scope and my stern facing west toward the beach with an easterly wind. It is common for winds to change and blow from the west at 20 knots at 2am in the Sea of Cortez, the Chubaco wind. I had used the CQR with great reliability in Puget Sound, the San Juans and SE Alaska. Unfortunatelty, it is not the best design choice for the Sea of Cortez. Most anchorages are a sandy bottom. I soon replaced the CQR with a 50# Danforth. I usually anchor in 30 ft of water and 150 ft of chain. The large flukes of the Danforth hold well and the anchor seems to remain set in spite of "clocking" winds. So bottom conditions have a lot to do with anchor choice.

[dmkkeng]

My go to ratio is 5:1 regardless of depth. I have a 55lb Rocna anchor that is oversized for my boat (45lb recommend for my boat) and 300' of 3/8" chain and 150' of rope. So for all but the deepest anchorages I have all chain attached to my anchor. Ratios examples such as 3:1 for a day stop, 5:1 overnight with light or moderate winds and 7:1 overnight with high winds are likely on the conservative side and don't take into account variables in anchor or rode weight or type. Recent articles that I have read on anchoring ratios also take into account water depth when determining the appropriate ratios. The conclusion that I came to was that a 5:1 ratio at depths less than 15' is not adequate and at depths greater than 30' is somewhat excessive especially in a crowded anchorage. In the future I plan to increase my ratio at depths less than 15' to 6:1 or 7:1 and reduce my ratio to 4:1 at depths greater than 30' especially where boat spacing is limited.

[GreenWave]

Originally Posted by geoff3nebel

Anchor chain or warp is useless lying in the locker. If there’s plenty of room in the anchorage why limit yourself? I’ll happily let out 40m of 10mm chain on the end of a 20kg Delta in 8metres of water to moor my ten tonne 41’ Westerly Oceanlord, sometimes more if there’s plenty of room and there might be some wind on the way

Not picking on you exclusively because others have said similar, but ...
the anchorage may be open when you get there but what about the guy who arrives at dusk and is looking for a spot? He assumes you have 5:1 scope when you really have much more. Next morning his cockpit is in your living room.


Granted your example is 5:1 but have heard in this thread that some double that.

[Kim Klaka]

Originally Posted by CarlF

I've been anchoring for 40 years. First boat had a CQR so I always used 7:1. As I've gone to better anchors I've shortened up a bit and now use 5:1.

But S/V Panope's anchor tests on YouTube are eye opening. His standard test is at 3.5:1 (and a short scope test at 2.5:1). The anchors that do well in his testing all set, hold, and reset repeatedly at this scope. There's no evidence in the video that more scope would make them hold any better.

Going to 4:1 scope will mean I'll have to worry less about swinging in a crowded anchor and will mean that my 150ft of chain (spliced to 150ft of brait) will be 100% chain in even deep anchorages.

I know this will seem like sacrilege to many but there's no magic to 7:1. Or science either. It's just the scope you needed with a 50 year old anchor design like the CQR.

Thoughts?

You might find the following presentation to be relevant:

https://www.youtube.com/watch?v=KVV0...3GpnEj&index=3

[chasfgr]

Pet hate, in crowded Med anchorages are those who arrive and pay out vast lengths of cable , rush ashore to the bar and then ignore the mayhem their boat is causing total mayhem amongst their neighbours.
This definitely includes the incompetent who have to use greater than 3:1 to anchor.
The bottom substrate is the important factor in the scope you use, next is the likelihood of storm-force winds and finally the anchor design.
Modern anchors (even the CQR) will frequently hold on a 2:1 scope and if you're anchoring in more than 15m of water, few boats can affored the amount of chain, up front, that a 7:1 scope requires.
I've anchored about 4000 times, in Western Approaches and the Med - dragged 4 times (2 of which were due to another boat fouling my rode).
Digging in the anchor is the secret, when the boat fishtails @ 50% power in reverse, you're fast and don't need all that scope.

[Mike OReilly]

Originally Posted by chasfgr

Pet hate, in crowded Med anchorages are those who arrive and pay out vast lengths of cable , rush ashore to the bar and then ignore the mayhem their boat is causing total mayhem amongst their neighbours.
This definitely includes the incompetent who have to use greater than 3:1 to anchor.

This is a ludicrous statement. What's incompetent is those who believe you can achieve the same holding at 3:1 vs 5 or more. You can't. It's actually been studied. Look at the chart Noelex posted earlier.

Now, it's certainly possible that 3:1 will be adequate in certain circumstances, and you're absolutely correct to be pissed at people who behave the way you describe. But that doesn't mean those who know that at 3:1 you're only holding on 40% of your potential strength vs 70% at 5:1 or 85% at 7:1 (from Noelex's chart), that these people are incompetent. I'd say the opposite is closer to the truth.

Originally Posted by chasfgr

The bottom substrate is the important factor in the scope you use, next is the likelihood of storm-force winds and finally the anchor design.

Of course it is. But it doesn't require anywhere near "storm-force" winds (55+ knots) bring your rode fully taut. At 3, or 2:1 it would take little more than a fresh breeze (17+knots) -- unless you've got exceedingly heavy chain.

Originally Posted by chasfgr

Modern anchors (even the CQR) will frequently hold on a 2:1 scope and if you're anchoring in more than 15m of water, few boats can affored the amount of chain, up front, that a 7:1 scope requires..

Most cruisers aim for a slightly higher standard than just "frequently holding." And I've never seen anyone claim a CQR will hold anything at 2:1 once the wind pipes up. As someone who used a CQR for a decade or more, that was certainly not my experience.

Deep water anchoring is different than shallow. It's defintely true one does not need the same scope in deep vs shallow.

Originally Posted by chasfgr

I've anchored about 4000 times, in Western Approaches and the Med - dragged 4 times (2 of which were due to another boat fouling my rode). Digging in the anchor is the secret, when the boat fishtails @ 50% power in reverse, you're fast and don't need all that scope.

This may be true in your defined area, with your boat. It's not true everywhere for everyone.

[sailorboy1]

I have always felt that it should be a requirement for every boat in the anchorage to have a sign on the bow with their scope length, type, and anchor

Of the more often that not I have found the opposite. I come into an anchorage and drive looking for a spot big enough for my wants and ask the boat next to it "how much scope do you have off". Normally the answer "I don't know".

[thinwater]

A new internet forum anchoring thread meme is born: the less scope you claim to need the greater your competence.

[Mike OReilly]

Originally Posted by sailorboy1

I have always felt that it should be a requirement for every boat in the anchorage to have a sign on the bow with their scope length, type, and anchor.

You jest, but I think it's an excellent idea. Would help others learn what is adequate for a given area (assuming not everyone is incompetent ).