An Anchor Thread! Grab your beers and popcorn.

[NormanS]

It is a mechanical impossibility for any loaded chain (other than a vertical one) to be absolutely straight. Obviously, this is not peculiar to chain, think of overhead power lines etc. The elastic limit of the material determines when it starts to deform under tension.
So it depends on your definition of "very straight". A bit like "very unique" or " very dead". None of these mean anything.
The fact that Peter Haward's chain deformed in winds of 120mph, merely meant that the load on his chain exceeded the elastic limit, determined by the cross sectional area of the link, and the type of steel that the chain was made from.
At least, his experience proved that although the chain was stretched, all the other components of his anchoring equipment, from deck fittings to anchor, passed a severe test. Of interest, what anchor was he using?

 

[geem]

It is a mechanical impossibility for any loaded chain (other than a vertical one) to be absolutely straight. Obviously, this is not peculiar to chain, think of overhead power lines etc. The elastic limit of the material determines when it starts to deform under tension.
So it depends on your definition of "very straight". A bit like "very unique" or " very dead". None of these mean anything.
The fact that Peter Haward's chain deformed in winds of 120mph, merely meant that the load on his chain exceeded the elastic limit, determined by the cross sectional area of the link, and the type of steel that the chain was made from.
At least, his experience proved that although the chain was stretched, all the other components of his anchoring equipment, from deck fittings to anchor, passed a severe test. Of interest, what anchor was he using?

Are you serious? Impossible for any loaded chain to be absolutely straight? Having snapped chains towing heavy machinery on farms in the past I would beg to differ. Bar tight chain under enough load is dead straight.

 

[rotrax]

True knowledge is the product of direct experience.

I assisted on two serious HGV recoverys. Fully loaded 42 ton artics.

The chains used to revolve the ditched one were as straight as a pencil. As were the wire ropes on the huge tow trucks winch once it was back on its wheels.

 

[rotrax]

It is a mechanical impossibility for any loaded chain (other than a vertical one) to be absolutely straight. Obviously, this is not peculiar to chain, think of overhead power lines etc. The elastic limit of the material determines when it starts to deform under tension.
So it depends on your definition of "very straight". A bit like "very unique" or " very dead". None of these mean anything.
The fact that Peter Haward's chain deformed in winds of 120mph, merely meant that the load on his chain exceeded the elastic limit, determined by the cross sectional area of the link, and the type of steel that the chain was made from.
At least, his experience proved that although the chain was stretched, all the other components of his anchoring equipment, from deck fittings to anchor, passed a severe test. Of interest, what anchor was he using?

There are none so blind as those who will not see.

Power cables could be winched bar tight if the distance and strength of the towers was suitable. As it is, the distance and tower strength is wrong. Make it 30 0r 40 metres between towers it would be far different.

I used to use a garage 'Porta-Power' hydralic ram for chassis and motorcycle frame repairs. If the chain was used for pulling at around seven tons strain, I can assure you it was straight! So straight it sang. I made sure I was well out of the way should it let go.

Little H&S in those days....................................................

 

[geem]

There are none so blind as those who will not see.

Power cables could be winched bar tight if the distance and strength of the towers was suitable. As it is, the distance and tower strength is wrong. Make it 30 0r 40 metres between towers it would be far different.

I used to use a garage 'Porta-Power' hydralic ram for chassis and motorcycle frame repairs. If the chain was used for pulling at around seven tons strain, I can assure you it was straight! So straight it sang. I made sure I was well out of the way should it let go.

Little H&S in those days....................................................

The great thing with chain when it snaps is it doesn't go twang and eject missiles as it has little stretch in my experience. Chains would snap and just land on the floor between vehicles. Not elasticity but safe when towing a stuck tractor with a tracked excavator

 

[Stemar]

If I'm not mistaken, it's impossible to pull any flexible line, chain or whatever dead straight when gravity is pulling it any way other than vertical. The curve may be barely measurable, but it's there. However, what matters in an anchor rode is whether that curve is enough to allow it to straighten more under a shock load to absorb that shock.

An all chain rode relies on that to reduce shock loads, but how much curve you need to be effective is way beyond my rusty A level maths or physics. I'm content to leave it as the more the better, which means the heavier and longer the chain the better. Still, there comes a point where there isn't enough curve to do any good. A longer, heavier chain moves that point, but doesn't eliminate it, which is why an effective snubber and/or a mixed rode with elasticity in the rope part is more effective in extreme conditions. Hooke's law rules! Yes, the elastic bit will rebound when it snaps, but I would suggest that if conditions are so bad that a properly sized rope rode snaps, that'll be the least of you worries!

 

[NormanS]

There are none so blind as those who will not see.

Power cables could be winched bar tight if the distance and strength of the towers was suitable. As it is, the distance and tower strength is wrong. Make it 30 0r 40 metres between towers it would be far different.

I used to use a garage 'Porta-Power' hydralic ram for chassis and motorcycle frame repairs. If the chain was used for pulling at around seven tons strain, I can assure you it was straight! So straight it sang. I made sure I was well out of the way should it let go.

Little H&S in those days....................................................

I would still like to know what Peter Haward's anchor was. Presumably you have the book to hand?

 

[rotrax]

It does not say. As the event was in the late fifties or early sixties it was not a NG one!

 

[Neeves]

The great thing with chain when it snaps is it doesn't go twang and eject missiles as it has little stretch in my experience. Chains would snap and just land on the floor between vehicles. Not elasticity but safe when towing a stuck tractor with a tracked excavator

Chain when it fails will stretch but most of the stretch is permanent - the links elongate. Quite often the links elongate and narrow and in narrowing pinch the adjacent links and when the chain eventually fails you can pick up one end of the failed chain and it has turned itself into a non articulated bit of steel. Stretch can be as much as 20% of length. Chains that are commonly used for anchoring will start to stretch at about 2 x WLL, for a 8mm G30 chain that's at a bit more than 1.5t of tension You are most unlikely to enjoy 1.5t of tension produced by a vessel with the associated wind sized for that chain. Chains do, have, stretch - but they would not meet current standards. Chains are now Proof tested during production and Proof Test is a measure of permanent deformation at 2 x WLL. As Vyv demonstrated some years ago much G30 chain is almost a G40 quality and that 1.5t maybe as high as 2t before it stretches.

Chain failure seems to be a thing of the past - though there may be a lot of really old chain about that meets the G30 spec (or not) - those tensions are simply unlikely. I might suggest deck fittings will fail first - and if you are using a 15kg NG anchor 2,000kg is typically its hold - in clean sand and ideal conditions (no chop) (so it will probably pop out before you reach 2t.

Jonathan

 

[boomerangben]

I am frequently criticised for repetition - nestawayboats illustrates why I am repetitive.

Swivels have been thrashed to death, as not actually swivelling and being prone to failure. This is the reason I developed my Boomerang, Boomerang Your Anchor and NormanS developed his bent link.

Anchor Swivels: Caution Required - Practical Sailor

and also

How Well Do Swivels Reduce Twist? - Practical Sailor

These may be behind a paywall. I am sure PBO has published similar articles.

Oscalluti have their own device, a combination of a bent link and a swivel and Vyv Cox had a picture here on YBW illustrating it may have solved one problem but introduced another - that is equally damning of the design. Vyv may have written an article in PBO - but I don't recall.

But people miss these articles, or the posts here. But the more times the issues are aired the more chance people will take notice.

So....repetition is the name of the game - you may not like the repetition but there are people who have not read articles on swivels (or snubbers) and to require once is enough denies opportunity for members here to read something, of real interest. Reading is voluntary - you don't need to bore yourself - be selective and allow others the opportunity to learn.

And for an appropriate shackle - size is not everything. If you want quality buy a Crosby G207a shackle - but check it fits first - the smallest they make is a 3/8th" shackle - but it has a WLL of 2t much better than your chain. I buy mine from Tecni, in the UK. The shackle pin will fit metric 8mm chain but whether the 'eyes' will fit through the slots in a Knox - ask Knox Anchor.

The 'problem' with a mixed rode is that the textile portion needs to be sufficiently strong, and/or as strong as the chain. It thus tends to be a bit more beefy and less elastic than using a snubber.

Anchoring is a series of compromises.

But I'm becoming repetitive I'll have the Forum Police on my back soon for infringing 'topic frequency' rules

Jonathan

Quick question, why would the textile portion need to be as strong as the chain? A mixed rode will have a number of components, which of course the weakest must be greater than the maximum expected load by a margin of safety factor. But we have already seen that chain is generally far stronger than is required for a snubbed/mixed rode. Once you are converted to nylon rode components, chain is merely there because of its abrasion resistance.

 

[boomerangben]

The great thing with chain when it snaps is it doesn't go twang and eject missiles as it has little stretch in my experience. Chains would snap and just land on the floor between vehicles. Not elasticity but safe when towing a stuck tractor with a tracked excavator

I’ve had a chain snap trying to pull a tractor out of a bog and realised that chain can and does spring back. Frightening. I guess it all depends on the steel

 

[Neeves]

If I'm not mistaken, it's impossible to pull any flexible line, chain or whatever dead straight when gravity is pulling it any way other than vertical. The curve may be barely measurable, but it's there. However, what matters in an anchor rode is whether that curve is enough to allow it to straighten more under a shock load to absorb that shock.

An all chain rode relies on that to reduce shock loads, but how much curve you need to be effective is way beyond my rusty A level maths or physics. I'm content to leave it as the more the better, which means the heavier and longer the chain the better. Still, there comes a point where there isn't enough curve to do any good. A longer, heavier chain moves that point, but doesn't eliminate it, which is why an effective snubber and/or a mixed rode with elasticity in the rope part is more effective in extreme conditions. Hooke's law rules! Yes, the elastic bit will rebound when it snaps, but I would suggest that if conditions are so bad that a properly sized rope rode snaps, that'll be the least of you worries!

For an 8mm chain then a 10mm piece of nylon would be about right as a snubber (for a yacht for which 8mm is appropriate) and the nylon will have about half the strength of the chain. If you use stronger nylon it will not have the elasticity at lower tensions, say the tension from a 30 knot wind. Nylon ages and the strength will reduce with time, its a function of many and how large are its historic stretch cycles. If you are expecting 50 knot winds, actual winds to which you will be exposed at deck level - you should move to somewhere more sheltered. Forecasts are sufficiently accurate to allow most people to move. But its a yacht and its 'only' a forecast and you should have a storm snubber that is deployed and ready for use if winds are to be over 30 knots ++. You then release the every-day snubber and rely on the storm snubber - and being able to do all of this from the cockpit is sensible - hence running your snubbers along the side decks. My arrangement might look complicated - but its not complicated compared to venturing down the deck at 2am in a 40 knot wind imposed on the hull (with associated rain).

Most people are never going to experience 40 knot winds across their deck as they listen to forecasts - and move to somewhere where the 40 knots winds do not impact their hull - but a storm snubber is cheap and if you are venturing far from home then the cost of the investment in a storm snubber (better a bridle) will ensure you don't have to pay for divorce proceedings.

Just read that article on the storm in the Med. His chain hook was rubbish and he needed a storm snubber.

Jonathan

 

[boomerangben]

Are you serious? Impossible for any loaded chain to be absolutely straight? Having snapped chains towing heavy machinery on farms in the past I would beg to differ. Bar tight chain under enough load is dead straight.

The theory says that gravity will always have an effect to form a catenary, in theory NormanS is correct. In practice however, you’d need a very accurate ruler to measure it since it is negligible where T/s is large, ie tension is high and length is short

 

[geem]

I’ve had a chain snap trying to pull a tractor out of a bog and realised that chain can and does spring back. Frightening. I guess it all depends on the steel

It's always a bit of a wow moment but it seems to spring back only a foot or two. Pulling a Landrover out with a nylon rope on a Range Rover when the Landrover tow point failed was like being hit with a ballist missile. The tow hitch went through the rear window and the passenger seat and landed in the passenger footwear.

 

[Neeves]

Quick question, why would the textile portion need to be as strong as the chain? A mixed rode will have a number of components, which of course the weakest must be greater than the maximum expected load by a margin of safety factor. But we have already seen that chain is generally far stronger than is required for a snubbed/mixed rode. Once you are converted to nylon rode components, chain is merely there because of its abrasion resistance.

The rode is your ultimate back up. The textile portion will be subject to wear and ageing, nylon deteriorates with the number and size of the stretch cycles (not so the chain). The nylon will rub on the seabed (and wear). Whatever its specification its ultimate strength will reduce with time. If you start off with a rode with the chain with a strength of 3t and a rope of 50% of that your safety factor reduces. Better to have rope roughly as strong as the chain and add elasticity with a thinner snubber (which will also help prolong the life of the textile part of the rode).

Think of your mixed rode as being permanent but your snubber is sacrificial.

Because your textile portion of the rode is strong it will not offer much elasticity at lower wind speeds - say 30 knots - and it will be at 30 knots you will want the snubbing effects.

The chain still offers some catenary the chain and rope work together.

Jonathan

 

[NormanS]

For an 8mm chain then a 10mm piece of nylon would be about right as a snubber (for a yacht for which 8mm is appropriate) and the nylon will have about half the strength of the chain. If you use stronger nylon it will not have the elasticity at lower tensions, say the tension from a 30 knot wind. Nylon ages and the strength will reduce with time, its a function of many and how large are its historic stretch cycles. If you are expecting 50 knot winds, actual winds to which you will be exposed at deck level - you should move to somewhere more sheltered. Forecasts are sufficiently accurate to allow most people to move. But its a yacht and its 'only' a forecast and you should have a storm snubber that is deployed and ready for use if winds are to be over 30 knots ++. You then release the every-day snubber and rely on the storm snubber - and being able to do all of this from the cockpit is sensible - hence running your snubbers along the side decks. My arrangement might look complicated - but its not complicated compared to venturing down the deck at 2am in a 40 knot wind imposed on the hull (with associated rain).

Most people are never going to experience 40 knot winds across their deck as they listen to forecasts - and move to somewhere where the 40 knots winds do not impact their hull - but a storm snubber is cheap and if you are venturing far from home then the cost of the investment in a storm snubber (better a bridle) will ensure you don't have to pay for divorce proceedings.

Just read that article on the storm in the Med. His chain hook was rubbish and he needed a storm snubber.

Jonathan

Jonathan, I wish that you could come and sail in the Outer Hebrides. There are lots of sheltered anchorages. Sheltered from the sea, yes. Sheltered from the wind, no. You have to realise just how far north it is. At 58°N, in the exposed parts, there is very little in the way of vegetation, never mind trees, to absorb or reduce the wind.
Every time that you say, "If the wind was going to be that strong, they should have moved somewhere else". Where?
For instance, If I'm in the region of either of the Loch Roags, on the northwest coast of Lewis, next stop Greenland, where do I get this magical shelter from the wind? No, we just have to take what's thrown at us. I'm not complaining, I love it, but it grates with me when you repeatedly insist that shelter is available, when it isn't.

 

[boomerangben]

The rode is your ultimate back up. The textile portion will be subject to wear and ageing, nylon deteriorates with the number and size of the stretch cycles (not so the chain). The nylon will rub on the seabed (and wear). Whatever its specification its ultimate strength will reduce with time. If you start off with a rode with the chain with a strength of 3t and a rope of 50% of that your safety factor reduces. Better to have rope roughly as strong as the chain and add elasticity with a thinner snubber (which will also help prolong the life of the textile part of the rode).

Think of your mixed rode as being permanent but your snubber is sacrificial.

Because your textile portion of the rode is strong it will not offer much elasticity at lower wind speeds - say 30 knots - and it will be at 30 knots you will want the snubbing effects.

The chain still offers some catenary the chain and rope work together.

Jonathan

I guess it depends on the application. I have 5m of 6mm chain and 20mm of 8mm nylon 3 strand. I very much doubt the safety factor on the chain is less than 10 for my 20’ boat. There is no way I need rope as strong as that. I think you found a maximum snatch load of around 600kg on a 38’ cat (correct me if I’m wrong) which gives a SF of around 3 on 6mm G40 chain, greater for snubbed rode. You’d get nearly 4 on 10 MM nylon and more still because of the snubbing effect. So just how big a SF do you need? It seems crazy to me to snub a snubber (in effect) not least because the knots will weaken both rode and snubber and on a calm day might give you snakes wedding to sort out on recovery. Having said that, I’ve never tried. I suppose if you consider a snubber as consumable, then a rope rode should also be considered thus. But if a 10mm snubber provides sufficient elasticity and a sufficient SF, why do you need a back up? I think you’ve said before you need chain to provide security against coral but if that wasn’t a factor short chain and long nylon would save a lot of weight and ok live with regular change out, which you’d have to with the snubber anyway?
Interesting discussion!

 

[Neeves]

Jonathan, I wish that you could come and sail in the Outer Hebrides. There are lots of sheltered anchorages. Sheltered from the sea, yes. Sheltered from the wind, no. You have to realise just how far north it is. At 58°N, in the exposed parts, there is very little in the way of vegetation, never mind trees, to absorb or reduce the wind.
Every time that you say, "If the wind was going to be that strong, they should have moved somewhere else". Where?
For instance, If I'm in the region of either of the Loch Roags, on the northwest coast of Lewis, next stop Greenland, where do I get this magical shelter from the wind? No, we just have to take what's thrown at us. I'm not complaining, I love it, but it grates with me when you repeatedly insist that shelter is available, when it isn't.

If you measure 40 knots at your masthead - the actual wind on deck is less. If you are anchoring behind a low hill, mast height, the wind is even lower.

Now if you tell me you anchor fully exposed to winds coming off the Atlantic and those winds are 50 knots. .... but you are not. You report you are sheltered from seas, thus there is some land between you and the direction of the wind. If the land is mast height then the 40 knots you record at the masthead is much lower than 40 knots. Yes - you are anchored and the wind is 40 knots - but your hull is not exposed to 40 knots. Its your hull the determines the windage of your yacht, not the mast. If there are no seas - which is what you suggest the land behind which you shelter - is effective, you don't need trees for shelter - I know as I southern Tasmania there are trees - but they tend to be 10cm high.

Someone will tell us what reduction in wind speed might be valid based on the height of your masts.

Jonathan

Jonathan

 

[Neeves]

I guess it depends on the application. I have 5m of 6mm chain and 20mm of 8mm nylon 3 strand. I very much doubt the safety factor on the chain is less than 10 for my 20’ boat. There is no way I need rope as strong as that. I think you found a maximum snatch load of around 600kg on a 38’ cat (correct me if I’m wrong) which gives a SF of around 3 on 6mm G40 chain, greater for snubbed rode. You’d get nearly 4 on 10 MM nylon and more still because of the snubbing effect. So just how big a SF do you need? It seems crazy to me to snub a snubber (in effect) not least because the knots will weaken both rode and snubber and on a calm day might give you snakes wedding to sort out on recovery. Having said that, I’ve never tried. I suppose if you consider a snubber as consumable, then a rope rode should also be considered thus. But if a 10mm snubber provides sufficient elasticity and a sufficient SF, why do you need a back up? I think you’ve said before you need chain to provide security against coral but if that wasn’t a factor short chain and long nylon would save a lot of weight and ok live with regular change out, which you’d have to with the snubber anyway?
Interesting discussion!

If your rode is composed of 5m of chain and 20mm of nylon I can only assume you anchor in a duck pond. You are correct - no need to use a snubber. If you have made a mistake and use 5m of of chain and 20m of rope - then ..... your rode is too short for a cruising yacht.

Not uncommon but you were slightly economic with data - you are correct you don't need to worry about the strength of your textile portion - it and the 6mm chain are over strength. However because your vessel is 20' you may not enjoy much elasticity as your 8mm rope (and 6mm chain) is a bit oversized for a 20' vessel.

Jonathan

Jonathan

 

[NormanS]

If you measure 40 knots at your masthead - the actual wind on deck is less. If you are anchoring behind a low hill, mast height, the wind is even lower.

Now if you tell me you anchor fully exposed to winds coming off the Atlantic and those winds are 50 knots. .... but you are not. You report you are sheltered from seas, thus there is some land between you and the direction of the wind. If the land is mast height then the 40 knots you record at the masthead is much lower than 40 knots. Yes - you are anchored and the wind is 40 knots - but your hull is not exposed to 40 knots. Its your hull the determines the windage of your yacht, not the mast. If there are no seas - which is what you suggest the land behind which you shelter - is effective, you don't need trees for shelter - I know as I southern Tasmania there are trees - but they tend to be 10cm high.

Someone will tell us what reduction in wind speed might be valid based on the height of your masts.

Jonathan

Jonathan

That's very reassuring from your position thousands of miles away. ?
Our anemometer is indeed at the masthead, but it's at the mizzen mast head - what, maybe all of 25feet above the deck. So if it reads 74knots, I'm merely imagining that it's slightly windy. I stand corrected. ?