Anchoring with 4:1 Scope?

[contrail]

Originally Posted by MicHughV

I've lost track of the number of different anchors available to the yachtie.....different rode setups, different boats, different bottom holding, different experience, etc, etc, etc..when you pull up to an anchorage you will have no idea who is using what, at what scope, what depth....none...nada...zilch...
it's one huge mish-mash.....

Of course, you can always ask; I often do. It always surprises me -and makes me nervous - when the other boat won't, or can't say, and it happens more often that I would have ever thought!

[MJH]

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?

Here's S/V Panope's test of the Excel which I think will be my next anchor.

My previous boat was a San Juan 28 (6,200 lbs.) with 198' total of chain, 1/2" 3-strand nylon, and a Danforth 13S anchor sailed in the Pacific Northwest, well known for deep waters.

My general technique was to drop anchor and backdown to a 7:1 ratio. When in doubt due to location, expected weather, etc. I would drop all 198', backdown to a firm hold and then retrieve to an acceptable ratio. I once anchored in a small very remote British Columbia cove (no other boats) for the night and used all 198' in 95'of water and didn't drag because it was a calm beautiful evening.

As others have said there are numerous elements that go into anchoring properly. After 30 years of cruising I take all the anchor test reports with a large grain of salt. The best anchor (if there is such a thing) is no better than the thought and care used by the captain in selecting the best location and technique used in securing his boat for the evening and the weather elements expected. If you have any doubts about that just watch some of the charter boats anchor.

I'm now sailing a boat that weighs five times as much with 300' of chain and windlass. I've anchored from Alaska to Hawaii and the routine stays pretty much the same, first checking the expected weather and selecting the appropriate location. The rest is elementary.

~ ~ _/) ~ ~ MJH

[CarlF]

Originally Posted by Panope

More shallow pull vector absolutely makes anchors bury better.

Here is the test:

https://youtu.be/i146P6BL7y4

Impressive. I had not seen that video. Even though I use a chain rode, your video is convincing evidence to stay with my 5:1 scope whenever there's room and especially in shallower water where chain catenary might not be much good.

Thanks for all your work on this. And again, CruisersForum comes through with solid information. Rare on Internet

Thanks

[moseriw]

Originally Posted by Don C L

Now let's see, what's the name of your boat? You don't mind if I anchor upwind of you do you?

No Problem go up 80 m upwind, throw out 60 m of chain and we are fine.
Uaah but it is to deep there...
OK even with 16m which I consider as maximum for our windlasses you have 3,75:1 which is not so important as the weight of the chain.


Sorry pal - your problem - go elsewere or use a shoreline what I usually do in "close quarters" to enable others to come in.

[thinwater]

Originally Posted by contrail

Yes, and yes. Made a big difference in a hurricane I rode out.

Explain. Specifically, what was the difference.


A kellet adds weight, the same as deploying a similar weight of chain (but without the scope advantage). Thus, I can see the purpose...
* with rope in tides with light wind.
* with rope in a harbors and light wind, so you swing with chain rodes and yaw less.



But not once the wind comes up, the math and experience say it will just lift. Better and simpler to let out anouth 10-20 feet of chain.


I do use a kellet on my other boat (rope rode), but it is loops of chain of the same weight, because they are easier to handle over the roller and on deck.

[MicHughV]

Of course, you can always ask; I often do. It always surprises me -and makes me nervous - when the other boat won't, or can't say, and it happens more often that I would have ever thought!

Yes, off course, you can ask...if....there is someone on the boat at the time of your arrival...just one boat....or other boats in your immediate vicinity.....and as you say....you may...or may not get a response....you might hear that a certain amount of rode is out...but what?...all chain...rope/chain....etc...and what kind of anchor do they have down, what size is it....far too many questions......and there is no telling in what condition their equipment is in....then again....you might get an informed answer from an old salt...but a charter boat is unlikely to tell you much of anything..

some boats really sail around their anchor....other boats are docile...no control over that either.....I've seen boats anchor with what appears to be a half mile of rode...and then freak out should you be less than 1/4 mile from them...

some boats might come in at night, after you have hit the sack...or while you are at the bar...etc....too many variables to list...

there simply is no hard and fast rule is my opinion.....some common sense and seamanship is really all you have.....you have to assess each new anchorage on it's own merits and decide accordingly what is in your best interest...

[Dockhead]

Originally Posted by Mike OReilly

Except, that's not what I said, and I think you know that. In fact, based on your description of your own approach, you do exactly as I suggested. And I don't know where this "Fetishizing scope" comment comes from. No one I know has ever done this.

I agree, to be rational one needs to consider a wide variety of factors. You've listed a few. I'm sure we could extend your list quite a bit. And that's the point. To be truly rational is to admit that you can't know all the factors when anchoring. So, to be rational, one should build in a margin of error, or as I put it, be conservative.

Clearly that's what you do, even with your massive gear. Otherwise, and in your own words, you should only rarely put out more than 3:1, but you do "in bad weather more." That's not rational, unless your bad weather is a hurricane.

So all good .

Yes, of course. I wasn't accusing YOU of fetishizing scope; I was just saying it for the record.

Some people think that scope is the single measure of anchoring, and that's a mistake. There is no such formula as x:1 and you're good no matter what the bottom, how big if your anchor, how deep the water, etc. It depends. The whole idea of oversizing the anchor, and having the best anchor available, is to give yourself room to deal with (a) shorter scope; (b) less than perfect bottom; (c) unexpected bad weather. A 100 pound Spade at 3:1 holds better than a 50 pound Delta at 20:1 holds in the same bottom. For example. And if that Spade has say 10x the holding power you need in a medium bottom, then you don't mind at all giving up 50% of that to get the scope down to 3:1. It makes no difference since it's still 5x more than you need.

But as you correctly say you must have a margin of error, because you never know exactly for sure what kind of weather will blow up, or exactly how firm that bottom is. If your anchor barely holds you and you don't dare to go down below the optimum scope, you've got the wrong anchor. I'll take 7:1 if it doesn't cost me anything. But rarely more than that -- diminishing returns.

[Dockhead]

Originally Posted by PirateGuy

. . . I have found the CHIRP sonar I recently added to my sensor suite to give me a pretty good idea of bottom conditions, especially if rocky or with coral heads. A strong bottom return signal (which is quite distinct from the fuzzy return in soft mud) is also useful.. . .

Thread drift alert! I am VERY interested in this -- I've been thinking about doing the same thing. Since it would mess up this thread, I've started a new one - PLEASE tell us there about your experiencers.


https://www.cruisersforum.com/forums...36#post3313436

[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

[cdcorl]

All chain? 3 or 3.5:1 is always plenty. I like 25’ of it to be a good double bridle. I only go more if the bottom is questionable. 25’ of chain with line? 8:1.

[Mithril Bham]

3 to 1 standard in SJI's but depends on bottom, swell, current, rode & wind. No wind, no current, no swell you could lay a chain out without an anchor and it will hold. Many variables.

[sstuller]

How are you going to set the anchor if your engine quits? Make sure your ground tackle and deck fittings are up to the task.

[Dockhead]

Originally Posted by cdcorl

All chain? 3 or 3.5:1 is always plenty. I like 25’ of it to be a good double bridle. I only go more if the bottom is questionable. 25’ of chain with line? 8:1.

Just like you can't say "7:1 is minimum", you also can't say "3 or 3.5:1 is always plenty". It depends on your anchor, and the bottom, and the weather. At 3:1 a good anchor will have about 50% of its maximum holding power (for that bottom). If 50% enough? Well, it ought to be under most circumstances. But not always.

The fact that it's all chain doesn't necessarily change the scope you need. Once there's enough wind to pull the catenary out of the chain, then chain and rope work more or less the same. In any case, the geometry is the same.

[Moo]

Originally Posted by cdcorl

All chain? 3 or 3.5:1 is always plenty. I like 25’ of it to be a good double bridle. I only go more if the bottom is questionable. 25’ of chain with line? 8:1.

This is the "best" post in this thread LOL. Advocating a set scope with no mention of gear, depth, bottom, swell, waves, wind strength, gust strength, current, vessel windage etc.. etc..

Just for the record I occasionally shorten up to 3:1 ish when the water is over 20m deep and the wind not forecast to be over about 25'

10.8m steel fin keel yacht. 20kg Rocna as bower with 10mm chain.

These anchor threads are always fun.

[Chotu]

I have a logical question for the short scope crowd:

Other than a crowded anchorage or a spot where you are trying not to swing into a hazard, what is the goal?


If you are trying to put out the minimum scope you can get away with, you’re factoring in:

*bottom type
*expected weather
*unexpected weather
*if it’s good holding ground exactly where you dropped it
*current


Say you tally all that up and determine everything is favorable so you can get away with 4:1. Or maybe it’s really favorable and you can do 3:1.

But then 2 days later, a front passes and you end up with 40 knot winds.

You now have diff conditions and decide to increase the scope to 5:1 because all the factors you consider say it’s not ideal for 3:1 anymore.

Ok, no problem. Just let some more out, right? Easy!

But why?????

Why not just set the anchor for its best performance when you arrive and forget about managing the anchor?

I dump out 10:1 not because I need it on nice calm days. I dump it out so when a surprise thunderstorm comes flying through while I’m ashore, the boat stays put. So I can sleep through truly insane weather soundly, safely and in comfort and security.

But what’s the main reason I dump out 10:1?

Because I’m lazy!

I’d rather do other things than manage my anchor system constantly. 10:1 is “set it and forget it” scope. Like an autopilot for your anchoring system.

Why do you all want to pay this much attention to your anchoring system? That’s the part I just can’t wrap my head around.

Do you not use the autopilot when underway? Do you prefer to be more deeply involved in the management of things on the boat than to have automatic systems? Does it make boating more enjoyable to keep track of things like this?

It might for some people and I can understand if it does. Then I would understand the short scope and playing with the scope as conditions change.

In my lazy world, I dump it overboard at 10:1 and don’t think about it again until it’s time to pull it back up. For weeks. No matter what the weather, all the way up through named storms. I check for chafe once a season or so if it’s been particularly brutal out. That’s it. Otherwise, the anchoring system is not in my thoughts.