Anchoring with chain only versus anchoring with a mix of rope and chain

[Neeves]

Thanks Jonathan!

And yes, my comment on 1 metre stretch (at least) needs more qualifications. All my studies have shown that no matter what snubber or rope or even dog bone you use, thin and short, thick and long, at the end of the day all that counts is by how much it stretches at a given wind force. In my work I chose - arbitrarily - a wind strength of 8 Beaufort as a reference force, but any other would do equally well. But my 1 metre comment refers to 8 Beaufort.

Now, why is that so? Since energy / work is force times distance, it is clear that in order to absorb a given amount of shock load energy, you can either chose a large force and a short distance, or a small force and a long distance. The product of the two is the same. But you do not want a large force, as this is the anchor load / bow load. Consequently, if you intend to keep the force as low as possible, you need to increase the distance over which the rope or snubber will have to stretch.

For any normal sized vessel that in this community we usually talk about, it turns out that this distance is 1 - 2 metres at 8 Beaufort. Beyond this, the additonal gain gets very small.

And yes, 30 kn, 40 kn, 50 kn winds are quite different, as the wind load is quadratic in wind speed. To me, the only solution is to have more than one snubber. Have one as a lunch hook, another one for daily / nightly use in ok weather, and yet another one for when it really blows hard. They will come with different elasticities and different maximal working loads. The added benefit is that the heavy duty one will not get worn out by daily use and then be rendered useless when its time comes.

The question how to change from one to another is a tricky one. With sufficient weather forecast, one can do this switch in time before it starts to blow. Otherwise, I think I will simply add my heavy duty bridle and then disconnect my normal bridle, dropping its ends in the water. It is too short to get entangled in the prop, so it should be ok.

Cheers, Mathias

Thanks Mathias.

If I read carefully you are not saying 1m elasticity but 1m-2m elasticity? You may find some surprise being expressed (but not from me)

I thought you recommended long snubbers but you are saying that if the squall came through 'unforecast' then you would drop the everyday bridle and attach your storm bridle. I assume you are still looking for the same 1m-2m elasticity (but now at the higher windspeed). what sort of length are you advocating, both for the storm bridle and the everyday bridle?

In this community very few will have any idea of the tension in their rode - how do you suggest they address this omission with any certainty..

I have recently been introduced to Marlow's KERR, vehicle snatch recovery cordage. K.E.R.R. To me it looks too beefy for the size of vessel owned by members here. But there may be other ropes of a similar construction that might be more applicable - and offer the 1m-2m elasticity you recommend. In Oz, as you may know, 4x4 adventures are common place and snatch recovery kits (and land anchors) can be bought off the shelf (I thought they used tape, rather than rope). Any comments?

Take care, stay safe

Jonathan

 

[geem]

If you use a mixed rode, not a snubber, then the textile portion needs to have a strength sufficient to hold the yacht in all conditions. If you use 8mm chain for its strength then the rope needs to have the same strength as the chain, preferably more as the rope will degrade. A rope of the strength of 8mm chain will not be particularly elastic and at short rode deployment will not offer sufficient elasticity.

You would be a brave man to rely on a nylon rope with the elasticity of a snubber. Its not something that I could endorse.

Better an all chain rode and a long thin snubber - the the fall back is the chain (which should be secured by a chain lock or short strop - not left to be secured by the windlass).

Jonathan

Our 50m of rope rode is permanently grafted on to the end of our 60m of 10mm chain. The rope is 1" multiplait. Breaking load of 12t. Far more than the chain. Anchored in deep water with 3:1 scope in very gusty conditions in 80ft of water there was no snatch. The combined effect of catenary and heavy rope works well. Although the rope has little stretch per metre, add enough metres and you get all the stretch you need

 

[Refueler]

Question for Neeves :

https://forums.ybw.com/index.php?attachments/img_4743-jpeg.136406/

Just a question : The two ropes to the 'bridle' - do you suffer chafe where they pass through ?

Just commenting : Sharp angles such as they are subjected to weaken a ropes ability to 'work' and also can lead to excessive chafe.

I do see you have fitted clean rounded sheeves ... but that's still a very sharp angle ...

Just saying ...

 

[Neeves]

Question for Neeves :

https://forums.ybw.com/index.php?attachments/img_4743-jpeg.136406/

Just a question : The two ropes to the 'bridle' - do you suffer chafe where they pass through ?

Just commenting : Sharp angles such as they are subjected to weaken a ropes ability to 'work' and also can lead to excessive chafe.

I do see you have fitted clean rounded sheeves ... but that's still a very sharp angle ...

Just saying ...

The Low Friction Rings are a direct copy of Ronstan's low friction rings, made in the same factory but they are machined to the diameter I specified and in 316 stainless (to be compatible with the Duplex stainless (black painted) plate.. They may look like sheaves - but are actually LFRs. They are threaded so that I could insert them in the plate. You can buy similar rings from Allen Brothers in Essex (amongst other sources) The angles are too large but the movement through the rings is not great. The diameter was dictated by the largest hole I could make in prototypes (wrong reason, but needs must). I have tried replacing the LFRs using blocks (these are snatch blocks) - but they make not an iota of difference. The rope cover is specifically,y designed to be abrasion resist over rock (it is for rock climbing). So far, after 2 years no sign of damage - but any damage might be in the core - unseen (we carry complete spares). I would have liked the LFRs to have been bigger but then the plate would have become monstrous. The plate design developed slowly this was the best - but as you indicate there have been compromises - I know I could make some minor improvements but I'm looking at long term usage, have a few plates being tested by others - so I am being patient. One of the changes is to incorporate the rubber dog bone things to modify elasticity. I have a design for those people who sail a monohull (and have a bow and water line located pad eye).

Jonathan

 

[Neeves]

Our 50m of rope rode is permanently grafted on to the end of our 60m of 10mm chain. The rope is 1" multiplait. Breaking load of 12t. Far more than the chain. Anchored in deep water with 3:1 scope in very gusty conditions in 80ft of water there was no snatch. The combined effect of catenary and heavy rope works well. Although the rope has little stretch per metre, add enough metres and you get all the stretch you need

Interesting how we come to similar conclusion but based on different theses. You have a heavy yacht (no disrespect) and a relatively short length of heavy chain with a 'textile' extension. We have 'plastic fantastic' and a short length of small high tensile chain, 75m x 6mm to your 60m and we have 2 x 30m elastic snubbers instead of your 60m of 1" multi plait. In deep water you will enjoy good snubbing from10mm chain we enjoy good snubbing from an 'elastic' rope.

There are many ways to skin a rabbit - and many ways to rig a rode - and many of the ways are very different but each combination can be correct.

Showing our convergence of ideas - we both highly rate the Spade anchor design. on which each of our very different yachts with very different rodes rely. Similarly our wives (said this before (one each) are responsible for anchor deployment (and enjoy cooking).

Take care, stay safe

Jonathan

 

[Refueler]

The Low Friction Rings are a direct copy of Ronstan's low friction rings, made in the same factory but they are machined to the diameter I specified and in 316 stainless (to be compatible with the Duplex stainless (black painted) plate.. They may look like sheaves - but are actually LFRs. They are threaded so that I could insert them in the plate. You can buy similar rings from Allen Brothers in Essex (amongst other sources) The angles are too large but the movement through the rings is not great. The diameter was dictated by the largest hole I could make in prototypes (wrong reason, but needs must). I have tried replacing the LFRs using blocks (these are snatch blocks) - but they make not an iota of difference. The rope cover is specifically,y designed to be abrasion resist over rock (it is for rock climbing). So far, after 2 years no sign of damage - but any damage might be in the core - unseen (we carry complete spares). I would have liked the LFRs to have been bigger but then the plate would have become monstrous. The plate design developed slowly this was the best - but as you indicate there have been compromises - I know I could make some minor improvements but I'm looking at long term usage, have a few plates being tested by others - so I am being patient. One of the changes is to incorporate the rubber dog bone things to modify elasticity. I have a design for those people who sail a monohull (and have a bow and water line located pad eye).

Jonathan

I wasn't trying to be smart or anything .... just as an ex Seaman - we always tried avoid acute angles even with smooth fairleads etc. Ropes can - especially wire ropes lose strength when angled too far ... there used to be BSF Safety films about it ,...

 

[MathiasW]

Thanks Mathias.

If I read carefully you are not saying 1m elasticity but 1m-2m elasticity? You may find some surprise being expressed (but not from me)

I thought you recommended long snubbers but you are saying that if the squall came through 'unforecast' then you would drop the everyday bridle and attach your storm bridle. I assume you are still looking for the same 1m-2m elasticity (but now at the higher windspeed). what sort of length are you advocating, both for the storm bridle and the everyday bridle?

In this community very few will have any idea of the tension in their rode - how do you suggest they address this omission with any certainty..

I have recently been introduced to Marlow's KERR, vehicle snatch recovery cordage. K.E.R.R. To me it looks too beefy for the size of vessel owned by members here. But there may be other ropes of a similar construction that might be more applicable - and offer the 1m-2m elasticity you recommend. In Oz, as you may know, 4x4 adventures are common place and snatch recovery kits (and land anchors) can be bought off the shelf (I thought they used tape, rather than rope). Any comments?

Take care, stay safe

Jonathan

Hi Jonathan,

Well, my everyday snubber / bridle needs to be able to cope with a squall. I would not want to have to drop it for every squall that passes by. Where I am currently sailing and anchoring, that would mean having to drop it every day... Although an individual squall may not be forecast, one certainly knows whether squalls are likely or not in a given area. So, when I say 'every day snubber', I mean a snubber that can take the usual in the region one happens to be in, and this will certainly depend on the region. But it is not there to ride a long, serious storm.

As to lengths - it will always be a compromise. But given that normal snubber material should not be stretched by more than 20%, this together with my 1-2 metres of stretch at 8 Beaufort imply that a snubber needs to be at minimum 5 metres long to achieve 1 metre of stretch, better 10 metres. Longer is certainly better to reduce the maximal stretch and hence increase the snubber's life.

I do not have your neat system of running the snubber along the deck, so my everyday bridle is only 5 metres long (each leg), my heavy duty bridle is about 14 metres long. I consider this as the minimum. At the next replacement cycle I will go for longer ones.

Regarding what tension to expect in the rope - my tool, www.anchorchaincalculator.com, gives a good idea what to expect for the vessel at hand. It is then down to studying the specs of various ropes to find the one that can cope with the expected maximal tension.

I have not heard about the KERR stuff, need to look into that.

Cheers,

Mathias

 

[Neeves]

I wasn't trying to be smart or anything .... just as an ex Seaman - we always tried avoid acute angles even with smooth fairleads etc. Ropes can - especially wire ropes lose strength when angled too far ... there used to be BSF Safety films about it ,...

You are correct - it is bad practice to have such large angles through LFRs - but its neat and if you use blocks, as I illustrate its becoming overly complicated - and anchoring should be simple. and easy. I decided my compromise might be more acceptable - but I have been trying to show there are options. I hoping people will look at the things I design (not many) the other big one is my Boomerang and they say:

I can do that - and I can make it better. The idea is perfect but I can make an improvement.

I'm not in this to make money - but knowledge is of no value unless it is shared. I appreciate its only for a few - but this forum gives me the vehicle to disseminate. If someone does not like it - tough - go and read something else!

But thank you for the comment - it might allow someone else to think more deeply and offer a novel idea.

Jonathan

 

[Neeves]

Hi Jonathan,

Well, my everyday snubber / bridle needs to be able to cope with a squall. I would not want to have to drop it for every squall that passes by. Where I am currently sailing and anchoring, that would mean having to drop it every day... Although an individual squall may not be forecast, one certainly knows whether squalls are likely or not in a given area. So, when I say 'every day snubber', I mean a snubber that can take the usual in the region one happens to be in, and this will certainly depend on the region. But it is not there to ride a long, serious storm.

As to lengths - it will always be a compromise. But given that normal snubber material should not be stretched by more than 20%, this together with my 1-2 metres of stretch at 8 Beaufort imply that a snubber needs to be at minimum 5 metres long to achieve 1 metre of stretch, better 10 metres. Longer is certainly better to reduce the maximal stretch and hence increase the snubber's life.

I do not have your neat system of running the snubber along the deck, so my everyday bridle is only 5 metres long (each leg), my heavy duty bridle is about 14 metres long. I consider this as the minimum. At the next replacement cycle I will go for longer ones.

Regarding what tension to expect in the rope - my tool, www.anchorchaincalculator.com, gives a good idea what to expect for the vessel at hand. It is then down to studying the specs of various ropes to find the one that can cope with the expected maximal tension.

I have not heard about the KERR stuff, need to look into that.

Cheers,

Mathias

Thanks Mathias,

Better the link comes from you.

Jonathan

 

[ibbo]

We anchor in tidal rivers fairly frequently. When I used rope with a 10m length of chain, expecting it to be a good all round choice, the biggest problem was wrapping the rope around the keel on the turn of the tide. A mixed rode gives me no sleep at night.

All chain with a short snubber to stop chain noise is perfect for us.

Unfortunately there is no fixed answer for every situation.

 

[Neeves]

We anchor in tidal rivers fairly frequently. When I used rope with a 10m length of chain, expecting it to be a good all round choice, the biggest problem was wrapping the rope around the keel on the turn of the tide. A mixed rode gives me no sleep at night.

All chain with a short snubber to stop chain noise is perfect for us.

Unfortunately there is no fixed answer for every situation.

You could consider the rivers in which you anchor and ponder their depth (and how much shelter there is for you in those rivers). You may calculate that with, say 15m of chain you could comfortably anchor, at a 5:1 scope you would need a depth of 3m thus 15m of chain - no need to deploy any rope at all. You could still use a mixed rode as if your yacht is, say 8m long, you could deploy maybe another 4 m of rope - as it will be more than 4m ahead of the keel.

I can advise that if you are using 6mm chain it wraps itself, certainly round a sail drive, with surprising ease - even chain might not be the answer.

I wholeheartedly agree - there is no one right answer.

Jonathan