Anchoring scope YM article

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RJJ

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How much anchor chain? - Yachting Monthly

Happy Christmas folks

Any views on the article, which confused me? I am always happy to learn but am sceptical about the rules-of-thumb cited here. There are many variables, and the art is picking out which key variables to inform your educated guess. I don't see that boatlength or catenary estimates are very useful.

I propose to stick with depth as the main variable, indicating 3:1 in ideal conditions when well-attended; 4:1 always to leave the boat; increasing to 7:1 in adverse conditions at which point strength of gear becomes the limiting factor rather than catenary. And always using a snubber. And considering a tandem/double/stern anchor if it's really arsy or to limit swing.

What am I missing?
 
Make sure you include the height of the bow.

Personally I use 4:1 in ideal 5:1 usually and 7:1 in extremis. Also investigating the use of a riding sail.
 
Yes; or just take the scope from where the chain enters the water rather than the bow roller. Thoughts on the article?
 
If the article you are discussing is the one printed a couple of months ago I would treat its advice cautiously. All of the replies above, along with your initial post, are sensible solutions using well-established guidelines.
As a matter of interest, two years ago I anchored using my Fortress anchor with a scope of only 3:1 on Anchorplait in a full gale for several days. No.problems other than difficulty in getting the anchor out of the seabed.
 
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we use 4:1 to water line most of the time, bit more in shallow water and lots more if leaving the boat/ heavy weather/ bad ground conditions. Can't see the point in using less than 4:1 most of the time, clearly if its tight you might need to reduce it a bit and keep an eye on things but generally it just a few seconds longer on the windlass so might as well be safe.
 
vyv_cox said:
If the article you are discussing is the one printed a couple of months ago I would treat its advice cautiously. All of the replies above, along with your initial post, are sensible solutions using well-established guidelines.
As a matter of interest, two years ago I anchored using my Fortress anchor with a scope of only 3:1 on Anchorplait in a full gale for several days. No.problems other than difficulty in getting the anchor out of the seabed.
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Thanks Vyv...kinda as I thought. Will stick to plan A.

Interesting re the fortress, and good to know as our kedge is a (full-size) fortress. With 6m of chain; I don't think I am as brave as you with rope only 3:1. Happy Christmas
 
I confess that I have not read the article to which you refer. Not because I'm not interested, nor becuassae I am parsimonious (which I am) but because UK magazines take a very long time to arrive in some of the UK's historic outposts (they come by sea - and its a long way!)

If you want to delve into the maths of scope - then check this link to Cruisers Forum:

Anchor chain catenary is real - Cruisers & Sailing Forums

There was yet another thread a bit earlier on 'scope' again in CF, if you are a glutton for punishment, I recall is was linked (possibly by Dockhead, who seems keen on the topic)

Both threads miss key characteristics (for example Vyv's experience with his Fortress would not be accepted). Scope is but part of the equation - just remember the anchor itself is, actually, quite important :) as is the seabed, the steadiness of the wind direction and the depth of water (3:1 in 3m is different to 3:1 in 15m). Snubbers, or good snubbers will negate much sage advice. Much sage advise is also based on antiquated ideas - and Vyv's experience is a refreshing breath off fresh air (and an anecdote which I would underline).

Anchoring is all about compromises and there are commonly many correct answers. Sadly many of the compromises are made for you - the size of your chain is what is on the yacht, the length of the chain is what you've got (when you decide you wished you had more :) ) and your anchor is not easy to change if you are in the isles of NW Scotland.

Jonathan

Edit

I have just noticed that you link the article - which I have now read. He seems oblivious to snubbers (which in 2019, and the wealth of threads on YBW, seems very odd). For this reason alone - I would treat the article with caution.

I might commend a search using the YBW search engine - 'snubbers' - it will keep you busy over these long winter nights (but have a nice bottle of decent whisky handy). Note that Vyv was using anchor plait - useful stuff!

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My norm is 10 metres + 3:1 (chain, measured from water level, allowing for tide if any). Since I never anchor in less than about 2.5m, that means a minimum of 17.5 metres.

Very rarely use more than this, except in exceptionally strong winds when I have plenty of space.
 
AndrewB said:
My norm is 10 metres + 3:1 (chain, measured from water level, allowing for tide if any). Since I never anchor in less than about 2.5m, that means a minimum of 17.5 metres.

Very rarely use more than this, except in exceptionally strong winds when I have plenty of space.
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My experience is very similar. The Fortress case history I posted above occurred due to a mistake in the Anchorplait length markers, only discovered when we recovered it. That was in 6 metres if I remember correctly.

The article suggests differing rode lengths for every wind speed, although not sure how you would predict this. I almost invariably aim to anchor in around 5 metres and usually put out 25 metres of chain measured at the water. This has always been sufficient in the strongest of winds, although along with most of us I will add 10 metres if it gets very windy overnight.
 
Neeves said:
But Vyv,

Do you use a snubber, for both the 'normal' 5:1 scenario with 5m depth and what works out to be 7:1 if it might be 'windy (?)'

Jonathan
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Always use a snubber. A good stretchy one for open water anchoring, 11mm doublebraid nylon and a much stronger one for stern-to berthing to unload the windlass. Elasticity is not desirable when stern-to.
 
vyv_cox said:
My experience is very similar. The Fortress case history I posted above occurred due to a mistake in the Anchorplait length markers, only discovered when we recovered it. That was in 6 metres if I remember correctly.

The article suggests differing rode lengths for every wind speed, although not sure how you would predict this. I almost invariably aim to anchor in around 5 metres and usually put out 25 metres of chain measured at the water. This has always been sufficient in the strongest of winds, although along with most of us I will add 10 metres if it gets very windy overnight.
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We had a similar accidental scope experience. We end for ended our chain as it was going rusty. We anchored in relatively sheltered waters but it was blowing 30-35 kts for a couple of days. Our Spade anchor was set on all chain and a long stretchy snubber in sticky mud. When we recovered the anchor we realised that with had mixed up the chain marks due to the end for end. We had only had our Spade on a scope of 2.5:1 it didnt drag. I think the success was down to the good anchor and 9m snubber with an oversized rubber snubber as well. We have since moved to using a 12m snubber for deeper water and a 7m skinny snubber for shallow water.
 
In normal conditions I aim to drop my Delta in 3 to 3.5 mtrs, attach the 10m snubber at the 15m chain mark which means I have at least 20m of chain to the water.
I never put out less than 20 mtrs of chain, if there is a swinging issue I put a Chum on just before the snubber.
 
Unfortunately, I have not read the Yachting Monthly script.

We all seem to have a number of ways to work out the scope for out yachts; it appears that most of us come up with similar scope lengths. There are so many variables that we need to consider such as type and weight of anchor, chain, rope, yacht weight, yacht length, weather conditions, sea bed type and depth.

For my 10m sailing boat, heavy loaded, I use:
15m of chain plus 2 x depth; if I am expecting strong wind, I let out additional 10 m.

So, if the depth is 7m, the scope will be: 15 + (2 x 7) = 29m of chain.
I carry 30m of 8mm chain and 60m of rope; 90m in total.
 
AndrewB said:
My norm is 10 metres + 3:1 (chain, measured from water level, allowing for tide if any). Since I never anchor in less than about 2.5m, that means a minimum of 17.5 metres.

Very rarely use more than this, except in exceptionally strong winds when I have plenty of space.
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That seems to match fairly well the catinary curve of depth against scope of when the last link lifts from the bottom for 10mm chain & 100Kg horizontal force.
Equal force scope
I tend to go for 3 x depth plus 20/25m which is closer to 300Kg.
Back to the YM piece, lacking in many ways IMHO, no mention of a snubber which can drastically reduce the force on the hook , or no mention of fetch either.
Anyone wants a good read with loads of real world testing then this is absolutely worth a kindle purchase for anyone spending time on the hook :cool:
Rigging Modern Anchors eBook: Drew Frye: Amazon.co.uk: Kindle Store

If only experience like that were to post around here....... ;) ;)
(Happy Xmas thinwater :) )
 
RJJ said:
Hi

... Why?

Thanks. ☺
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3:1 scope in 3m gives very little catenary, where the same scope in 15m gives lots. Catenary gives "spring". If you anchor in shallow water, your chain will never give " spring", no matter what scope you give it. If you anchor in deep water, the weight of chain hanging in a catenary gives very good resilience. Shallow water, use a snubber, particularly if your boat is light and ranges about. Other possibilities are available, like riding sails etc.
 
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