Anchor Scope

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Alanij

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What length of anchor chain or chain/rope combination do forumites have on their boats?

I ask, because my boat has 22m chain plus 30m rope, allowing me to anchor in 5m using chain only or about 8m using everything, which doesn't give me much scope (appropriately enough) for anchoring in the general area I do my boating as suitable spots to anchor in around 5m depth are not particularly common.

I am considering purchasing ~30-40m chain and adding this to the chain I already have - has anyone any experience of the Osculati or similar joining links?
 
I have used a osculati joining link successfully for many years on a previous boat going from 30 + 20 to 50 m of chain .
I did wrap some copper wire around it as an insurance it wouldn’t somehow naturally twist open in use .

As far as scope question there’s no definitive answer .Depends on the boat , waves , anchor , depth , any anchor watch surveillance , windage , density of nearby boats etc etc .

Fortunately in the Med where go we can find Sandy bottoms , dig in the anchor so it buries itself and always have nearby bolt holes to run to if the weather closes in .I can also dive in and eyeball the effect of scope .You will be surprised by the results , tend to put too much out .
 
What size boat and what type of anchoring, lunch, overnight, riding out storms? Also location? If occasional lunch/overnight anchoring in fairly benign conditions keep the chain and change to a longer rope. I’ve currently got 12m of 8mm chain with 100m of 14mm 3 strand on a 26’ <4t boat. If I were to plan regular overnighting I’d buy a longer length of chain.
 
Thanks Portofino - as far as the scope bit is concerned I was only looking for general answers, for the reasons you gave - the chain/rope combination currently on the boat was obviously suitable for what the previous owners' requirements.
Thanks for the link.
 
Jamie Dundee said:
What size boat and what type of anchoring, lunch, overnight, riding out storms? Also location?
Click to expand...

Hi Jamie - I was just keeping it vague, just to see what others have, expecting a wide range of answers.
The boat is 10.8m, just over 35ft, dry 6t, so ~7t in use. We've done lunch anchoring with the current set-up, but are intending to do more overnighting. Cruising area is Sounds of Luing & Jura down to Islay, Firth of Lorn, Mull, and hoping to extend our area to include the Treshnish Isles and Colonsay & Oronsay.

More chain is my preference, but being a Scot I'm looking at whether the cheaper option of just buying extra chain and joining it would be sufficient, or should I just stop mucking about and get a whole new (10mm) chain of an appropriate length and fit that.
 
Don’t forget to allow for the height of the bow above the water (which needs to be multiplied by the scope), plus distance to the windlass. Plus most of us would want a anchor snubber on a hook, which needs a bit of slack to work. So with a 1 metre bow height the first 5 metres or so are needed before allow for any water depth. And with a tidal range of say 4 metres at springs (much bigger in some locations) that is another 20m or so before you allow for depth at low water.
If going to be using for more than a lunch when on board, I would get a new length of 60m chain, then add a bit for luck.
(Typed sitting on anchor overnight, as have been most nights since April - regularly had 60m out overnight, and 70m in a gale)
 
I was passing and saw the thread:



The answer is more complicated than you might think

Older anchors reward use of more chain. New anchors, with some exceptions, are more dependable and are more forgiving. So in the absence of knowing what anchor you use and not knowing what others use with their comments on scope and rode length, the comments above - you need to make a judgement.

If you use a good, elastic, snubber, the demand to deploy more chain is reduced - as the elasticity of the snubber 'replaces' the catenary if you use a shorter chain. A good snubber will be at least boat length and when in use you will see it stretching. If it is too beefy - it will not stretch and you will not enjoy the benefits of elasticity.

The other unknown is chain size, diameter of the wire from which the chain is made. In general a generously sized chain will require less chain deployed than if the chain is a bit undersized.

If you anchor a lot and those anchorages are in more obscure locations then carrying a spare rode (and spare anchor) would be prudent. You could 'retire' your current rode to be a spare and invest in a single length of new chain.

If you are considering new chain and you use a windlass then be aware that there are two metric sizes for 10mm chain and the gypsies for each of these different specifications are not interchangeable. If you look through the Cox Engineering link that has already been posted you will find detail of the two specifications. for 6mm, 8mm and 12mm chain the two metric specification are the same sized link. If you take your gypsy apart - somewhere on the gypsy often the two 'inside' faces or round the circumference the size/specification of the matching chain is engraved, embossed.

There is an article on snubbers for monohulls in the July issue of YM

These are for sailing yachts - but the principals are the same:

How to: Dealing with Snatch Loads in an Anchorage

Anchor Snubber Tips

Know how: Expanding your Anchoring Repertoire

Know how: Ground Tackle

this is for a sail catamaran but if you have a beamy vessel - it may be relevant

A Snubber & Hook for all Occasions | Practical Sailor

Take care, stay safe

Jonathan
 
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'Older anchors reward use of more chain. New anchors, with some exceptions, are more dependable and are more forgiving. So in the absence of knowing what anchor you use and not knowing what others use with their comments on scope and rode length, the comments above - you need to make a judgement. '

belt and braces it is not an exact science, put more down if there is the room, with an elecric windlass why not ?
 
Another how long is a piece of string thread. I’m a 70m 10mm chain man with a 40kg delta stuck on the end. Has always worked for me.
 
simonfraser said:
belt and braces it is not an exact science, put more down if there is the room, with an elecric windlass why not ?
Click to expand...

The OP has not mentioned a windlass, nor chain size nor anchor.

Belt and braces is definitely not an exact science when there is no data.

But a key part of your post is

'if there is enough room'

With lots of room. most know the rules, deploy more and more (though where you get the second lot of more is an interesting question :). ).

The skills is - what to do when not enough room (and no more) - and have confidence in what you do.

Its not rocket science.

Jonathan
 
longjohnsilver said:
Another how long is a piece of string thread. I’m a 70m 10mm chain man with a 40kg delta stuck on the end. Has always worked for me.
Click to expand...

70m x 10mm on a 80', weighing 20t vessel, might be a bit parsimonious, on a 30' vessel maybe a bit OTT. :)

In the absence of data on the vessel - does not mean anything - how is the OP to make a decision with only half the information needed so that he can try to equate his vessel with yours, or anyone else.

Sorry to be harsh

Jonathan

Edit

We have a sailing cat, 38' x 22'6", fully laden 7t (full of water, fuel and provisions and a crew of 2 - capable of surviving (with a bit of fishing) for 3 months. Our rode is 75m x 6mm high tensile chain (same strength as the 8mm chain it replaces). We supplement the chain with 30m of elastic snubbers ( 2 snubbers. making a bridle). We use anchors that work by design, not weight - all aluminium. Our cat has the windage of a 'off the shelf' 45' yacht.

I don't contribute to motor boat forum (I know - so why have I interrupted :). ) and I don't know how a 45' yacht or a 38' cat relate to a Mobo.

I simply am offering data that the OP can try to relate to his questions.

close edit.
 
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Be as harsh as you like. It’s just a forum. And I use what I described to anchor a mirror dinghy. As pictured in my avatar.
 
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Here's my recipe for stress free beach restaurant lunches whilst my boat is at anchor and for getting a good night's sleep on the hook
  1. Check the maximum size of chain that your existing windlass can handle and upgrade the gypsy accordingly, if necessary
  2. Buy enough high quality calibrated chain (never rope) of that chain size to suit the maximum depths in the anchorages in your intended cruising areas. I know the accepted wisdom on scope is 3x depth but I sometimes put out 5x or even 7x depth if I'm anchoring overnight in marginal wind conditions. So if the max depth in your intended anchorages is say 10m, then you need 70m of chain. Obviously if you only intend to day anchor and you will never leave your boat to go ashore, you might select 4-5x scope ie 40-50m of chain
  3. Chuck away the standard anchor fitted to your boat (manufacturers always penny pinch by fitting the minimum size of anchor they think they can get away with) or at least stow it in your lazarette as a spare. Then buy the correct size of anchor for your boat as recommended by the manufacturer of the anchor type you are considering as a replacement
  4. As to what type of anchor to choose, this subject causes even more handbags on this forum than brexit but personally I favour the modern anchors over the traditional types. As it happens I have a Rocna but somebody will be along in a minute to tell me that Rocnas are made of Chinese spaghetti. Best thing you can do is ask the locals in your cruising area what anchors work there and what dont. One thing you will have to check is that any new anchor you choose fits your existing bow roller. It is a good idea to offer up the anchor into your bow roller before you buy it
I have a Ferretti 630 and when I bought the boat, it was fitted with 75m of 10mm chain with a 40kg Bruce anchor on the end. I upgraded that to 125m of 12mm chain with a 55kg Rocna anchor and I've been very happy with that set up
 
longjohnsilver said:
Be as harsh as you like. It’s just a forum. And I use what I described to anchor a mirror dinghy. As pictured in my avatar.
Click to expand...

I saw your Avatar but it actually does not tell me how long your vessel is nor how heavy - be as angry as you like but without that information the OP cannot compare your, satisfactory, practice with his requirement. He too may have a motorised Mirror dinghy - who knows. At least if you know, or look up, a Ferretti 630 you can find out how big the vessel is and then you know that one owner of that size of vessel did not think 10mm x 75m was adequate and upgraded to 12mm x 125m and increased anchor size from 40kg Bruce to a much better 55kg Rocna.

Jonathan
 
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Scope maybe important. Snubber maybe important. Chain size maybe important. But the only thing that IS important is never use a Delta anchor
 
Neeves said:
I saw your Avatar but it actually does not tell me how long your vessel is nor how heavy - be as angry as you like but without that information the OP cannot compare your, satisfactory, practice with his requirement.
Click to expand...

Ljs are you going to take this lying down? This migrant from a foreign forum is impugning your honour. I think this calls for a duel. Anchors at dawn on Teignmouth beach to the death I would suggest? I would be happy to referee
 
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