Anchor snubber- long stretchy rope or rely on catenary

[RupertW]

As the chain lifts and falls it causes the anchor to twitch.

Just put your finger on the anchor as the chain moves, you will feel it.
Jonathan

Still not convinced about the twitching (if by twitching you mean the whole anchor moves slightly) as observation from a few metres above looks like the anchor is absolutely still and no slow backwards move even in heavyish wind.

But always happy to learn so I will give that a go next season and feel for a vibration as the chain lifts (which I wouldn't describe as a twitch) or an actual small movement (which I would). I suspect I will just feel a vibration but until I feel it I am just surmising from the lack of any backwards movement over hours.

 

[RichardS]

That's why the few people left who still maintain that it's the chain that holds the boat .......

You've got a bite. Reel him in quick.

Richard

 

[Little Dorrit]

Continuing the drift where does Campbell fit in?http://www.campbellchainandfittings.com/about

 

[Neeves]

Campbell, part of Apex Tools.

Excellent shackles, (Orange Pin) up with Crosby G209a, but again the smallest is a 3/8th". We have a few and we use them in preference to anything else, but difficult (if not impossible) to source in Oz and I think similarly difficult in the UK. Ours came direct from America, but that was a special. We might go back to America in 2020 - and I'd buy some more.

They make a range of lifting equipment, hooks and hammerlocks. This is all powder coated, not really applicable for the marine environment. However if you can strip the powder coating off their new range of chain hook and have them galvanised they are an excellent design - but you would really need to be keen (there are easier options)

They make the complete range of galvanised Imperial chain, G30, G43, G70 (not sure if they make a BBB) - but it is Imperial sized. Galvanising is good, chain strength good. Like Peerless their G70 is an original G70 that they galvanise - Maggi's strength is higher (but Maggi has a poor reputation for their galvanising).

If you wanted American chain - Peerless are, or at least were, selling metric chain, G30, G40 and G70 from stock in Germany.

I've tested Campbell's range of gal chain and Orange Pin shackles. All results in Practical Sailor, separate articles on chain and shackles covering Peerless, Campbell, PWB (Oz and now owned by Kito who own Peerless and Kito Italy, was Weissenfells), Serafino also Oz, CMP and Maggi for chain and Crosby, Peerless, Campbell and West Marine (WM sourced from China) for shackles.

WM are a case in point - shackles are rated and meet strength for spec - but deform like spaghetti. I would not for any reason use them. UTS alone is an inefficient measure of quality as if the shackle deforms such that the only way to remove the anchor is to cut the shackles then in my book the shackle is a liability (in the same way 316 shackle are a liability). WM's shackles are embossed China and I suspect are of a quality similar to those you might find in many hardware stores. The only shackles I would suggest should be on a yacht are from Crosby or Campbell and if push comes to shove CMP - but none of the others.

If you have a large yacht and large chain then Van Beest and Columbus Mackinnon are also a good source - but most of us have smaller vessels.

The shackles to look for are described as Grade B, most others are Grade A, roughly half the strength of Grade B.

Campbell do not appear very interested in the leisure marine market, if distributors want to buy from them I believe they sell but its not a market on which they focus. I think it may be too small and fragmented, lifting, mining, construction, industrial marine appear to be more interesting to them.

I have no hesitation in using their chain or Orange Pin shackles.

If you found an easy way to buy their shackles - I'd be interested.

Jonathan

The website i unusual(ly) difficult

this I think is the listing for their 3/8th" Grade B shackles

http://www.campbellchainandfittings...ad-limit-metric-ton/2-t?q=Orange+pin+shackles

and they are still made in the US

 

[noelex]

Here is another drop of my Mantus anchor and a better photo of the fan pattern produced by the chain.

In this photo you can just see the chain emerging from the sand near the bottom of the photo. You can see the striations in the sand correspond to size of the links in the chain.

No twitching is needed to produce this pattern. If you see this pattern don’t interpret this as evidence that your anchor is twitching or moving in any way.

Indeed any anchor twitching would only tend to blur the pattern. The striations are produced by the chain sweeping across the bottom. The anchor has to be be stationary to produce the regular pattern you can see here.

The other thing to note, as a side interest, is how the direction of pull has altered substantially but the anchor has not rotated. People imagine their anchors swinging back and forth, but it takes quite a high level of force before a well set anchor will begin to rotate.

 

[Little Dorrit]

Well I'm in the Philippines visiting and it appears I can lay my hands on some locally in Manilla so I'll go and have a look and see what's available before I return to the UK. I need a few for some 8mm Lofrans G40 plus I'll get a few extra if the price is good to pass on at cost.

 

[Neeves]

Well I'm in the Philippines visiting and it appears I can lay my hands on some locally in Manilla so I'll go and have a look and see what's available before I return to the UK. I need a few for some 8mm Lofrans G40 plus I'll get a few extra if the price is good to pass on at cost.

Just be aware - the clevis pin will not fit Lofrans 8mm metric chain, nor any other 8mm DIN/ISO metric chain. You will need to enlarge the end link to get the clevis to fit, not impossible, both Vyv (who suggests squeezing in a vice) or Norman (who suggest enlarging with a drift) would agree. The clevis fit a Australian Grade L metric chain, but our links are bigger than European chain - really confusing.

Oddly, maybe not odd, American product is more easily available in Japan, Saipan and, now, the Phillipines than Europe or Oz.

Jonathan

 

[Little Dorrit]

Just be aware - the clevis pin will not fit Lofrans 8mm metric chain, nor any other 8mm DIN/ISO metric chain. You will need to enlarge the end link to get the clevis to fit, not impossible, both Vyv (who suggests squeezing in a vice) or Norman (who suggest enlarging with a drift) would agree. The clevis fit a Australian Grade L metric chain, but our links are bigger than European chain - really confusing.

Oddly, maybe not odd, American product is more easily available in Japan, Saipan and, now, the Phillipines than Europe or Oz.

Jonathan

Oh well that more or less scuppers that idea then but I'm pleased to have at least posed the question and found someone who knows the answer!

 

[Neeves]

Here is another drop of my Mantus anchor and a better photo of the fan pattern produced by the chain.

In this photo you can just see the chain emerging from the sand near the bottom of the photo. You can see the striations in the sand correspond to size of the links in the chain.

No twitching is needed to produce this pattern.

Indeed any anchor twitching would only tend to blur the pattern. The striations are produced by the chain sweeping across the bottom. The anchor has to be be stationary to produce the regular pattern you can see here.

The other thing to note, as a side interest, is how the direction of pull has altered substantially but the anchor has not rotated. People imagine their anchors swinging back and forth, but it takes quite a high level of force before a well set anchor will begin to rotate.

The chain appears to simply have slid round no thrashing on the seabed, no lift and fall, lift and fall. You can see the marks, made without a break, as each link has slid round. so there will be no twitching, any twitching will be lost in the seabed - the anchor is not under any tension. For the anchor to be under any tension the chain would have been lifted.

At a 5:1 scope with 30m of 8mm chain deployed the tension needed to lift all the chain, to the last link is 70kg (how do I know, I measured it). As the chain has slid round the tension is simply not significant, a very few 10s of kgs. If your anchor moves under such a low load - you would have a real problem. Obviously if you have a bigger chain, 10mm, the tension will be higher and if you are in deeper water the tension will be higher - but if the chain has not lifted - the tension is negligible. Of course its a 50kg anchor , it has been power set at a few 100s of kgs of engine - of course it has not moved!

Jonathan

 

[Neeves]

Oh well that more or less scuppers that idea then but I'm pleased to have at least posed the question and found someone who knows the answer!

Glad to be of help - and saved you carrying them back home! Pity - they are a good product.

Enjoy the Philippines.

Jonathan

 

[Neeves]

Noelex,

On 'your' CF shackle thread - Armorgalv by PWB was a complete and embarrassing disaster. The coating thickness was too thin and the product withdrawn and chain replaced with HDG. If you check your issues of PS you will find the detail. I was given full access to the range of PWB Armorgalv product and conducted abrasion tests. Some of the coating thickness was 20 microns.

The US Navy spec is 80 microns, my spec for my chain 100 microns, check my article on high tensile chain in PS. Subsequent batch of HT chain has also been to 100 micron coating spec. If you need to know more, let me know - I had been under the impression you had given up on using HT chain - but your new yacht is pretty hefty so maybe unnecessary. But all test show that Armorgalv (of any chain quality) has a longer life span than the equivalent thickness of HDG - and you can tailor the coating thickness (within limits)

There will be an update on our use of our HT Armorgalv coated chain, the latest production developments, further abrasion testing (prompted here) and development of various hooks (for snubbers) and other components in PS later this year or early next - something for you to look forward to!

Abrasion resistance is contingent on a decent coating thickness, this has been known for decades. The coating also has to be 'sound' - but if it is thin - it will not last.

Jonathan

 

[thinwater]

It should be obvious that twitching depends on the load. If the anchor is well-set in a good bottom, and the load is no where near the failure point, it won't budge. On the other hand, if the load was > 30% of dragging they'd probably all be shuffling, depending on the material. But in most of the images, the load is probably only 10% or so.

 

[RupertW]

The chain appears to simply have slid round no thrashing on the seabed, no lift and fall, lift and fall. You can see the marks, made without a break, as each link has slid round. so there will be no twitching, any twitching will be lost in the seabed - the anchor is not under any tension. For the anchor to be under any tension the chain would have been lifted.

At a 5:1 scope with 30m of 8mm chain deployed the tension needed to lift all the chain, to the last link is 70kg (how do I know, I measured it). As the chain has slid round the tension is simply not significant, a very few 10s of kgs. If your anchor moves under such a low load - you would have a real problem. Obviously if you have a bigger chain, 10mm, the tension will be higher and if you are in deeper water the tension will be higher - but if the chain has not lifted - the tension is negligible. Of course its a 50kg anchor , it has been power set at a few 100s of kgs of engine - of course it has not moved!

Jonathan

I normally mostly agree with you but that is so wrong.

Of course the anchor can be under some tension before it lifts. To take an extreme example of 14mm chain 100m long in 5m depth there will be lots of tension before it lifts.

But the next assertion about the tension needed, in your example 60kg tension not lifting and 80kg lifting makes it sound as if it would take more than a minor gust of wind - in fact 10mm chain at 5:1 scope will lift in well under 10knots of wind assuming the boat is veering about as most modern boats do.

And finally of course you will get a smooth fan even with chain lifting because it won’t lift for every part of every swing so over time all the lines will become smoothed.

 

[thinwater]

I normally mostly agree with you but that is so wrong.

Of course the anchor can be under some tension before it lifts. To take an extreme example of 14mm chain 100m long in 5m depth there will be lots of tension before it lifts.

But the next assertion about the tension needed, in your example 60kg tension not lifting and 80kg lifting makes it sound as if it would take more than a minor gust of wind - in fact 10mm chain at 5:1 scope will lift in well under 10knots of wind assuming the boat is veering about as most modern boats do.

And finally of course you will get a smooth fan even with chain lifting because it won’t lift for every part of every swing so over time all the lines will become smoothed.

The chain does not have to lift to generate a fan. This too, is obvious. With a smooth sand bottom, 60kg should be plenty. 20kg is probably enough in some conditions.

We're talking about two different things: yawing with enough force to cause an anchor to move, and wind shift sufficient to move the chain across the bottom. Very, very different. Dragging a chain sideways can be slightly difficult if it is imbedded in mud, but that is not what we are looking at.

Thus, neither disproves the other. Also an illustration of how different bottoms behave.

 

[RupertW]

The chain does not have to lift to generate a fan. This too, is obvious. With a smooth sand bottom, 60kg should be plenty. 20kg is probably enough in some conditions.

We're talking about two different things: yawing with enough force to cause an anchor to move, and wind shift sufficient to move the chain across the bottom. Very, very different. Dragging a chain sideways can be slightly difficult if it is imbedded in mud, but that is not what we are looking at.

Thus, neither disproves the other. Also an illustration of how different bottoms behave.

+1

This comes back to Neeves definition of twitching - if it means the anchor is moving at all backwards then it's not set properly and a problem and the fan says nothing about that - except maybe as stated above to show that backwards movement has not happened.

 

[noelex]

It should be obvious that twitching depends on the load. If the anchor is well-set in a good bottom, and the load is no where near the failure point, it won't budge.

I think this is correct.

The impression from the boat is that dragging is always caused by the anchor suddenly breaking out without warning. The vessel turns beam on to wind and the anchor starts dragging rapidily.

If you observe anchors underwater, unless the wind rises very rapidly, anchors often display the sort of behaviour that has been described in this thread as a precursor to a rapid drag. They will creep back in gusts, twitch and slide without digging in any deeper. Sometimes the wind will reduce and the anchor settles down again, but the above behavior is a sign that the anchor has very little reserve.

This can be seen underwater, but is very difficult to detect from the boat. If you do dive and observe the above behaviour I would strongly suggest doing something (such as increasing scope) so your anchor is no longer near the limit.

This is an unhappy Delta that is not yet started the rapid drag, but is slowly moving and creeping back with each gust. This anchor moved about 30m in 5-6 hours. The scope was about 7:1. You can see the puffs of sand caused by the anchors slight movement.

As a contrast this is a Delta in the sort of rapid drag that many owners are familiar with. You can see the anchor has almost no grip. The rapid speed is even causing the weighted toe to bounce off the bottom. At this stage the Delta had rapidly dragged about 60m. It was dropped at 5:1 but by the water was deeper by the time the photo was taken and the scope here was about 4:1. I had to be very careful photographing this anchor.

 

[RupertW]

I think this is correct.

The impression from the boat is that dragging is always caused by the anchor suddenly breaking out without warning. The vessel turns beam on to wind and the anchor starts dragging rapidily.

If you observe anchors underwater, unless the wind rises very rapidly, anchors often display the sort of behaviour that has been described in this thread as a precursor to a rapid drag. They will creep back in gusts, twitch and slide without digging in any deeper. Sometimes the wind will reduce and the anchor settles down again, but the above behavior is a sign that the anchor has very little reserve.

This can be seen underwater, but is very difficult to detect from the boat. If you do dive and observe the above behaviour I would strongly suggest doing something (such as increasing scope) so your anchor is no longer near the limit.

This is an unhappy Delta that is not yet started the rapid drag, but is slowly moving and creeping back with each gust. This anchor moved about 30m in 5-6 hours. The scope was about 7:1. You can see the puffs of sand caused by the anchors slight movement.

As a contrast this is a Delta in the sort of rapid drag that many owners are familiar with. You can see the anchor has almost no grip. The rapid speed is even causing the weighted toe to bounce off the bottom. At this stage the Delta had rapidly dragged about 60m. It was dropped at 5:1 but by the water was deeper by the time the photo was taken and the scope here was about 4:1. I had to be very careful photographing this anchor.

Great shots as a happy Delta owner (apart from distance to set) then it’s the first that I would worry about as the second is obvious.

 

[GHA]

I normally mostly agree with you but that is so wrong..

At last someone agrees with kellys eye! The anchor does nothing, it's all the chain.

For the anchor to be under any tension the chain would have been lifted.

Somehow the horizontal force on the chain appears from nowhere, or a few links of 8mm chain @ 5:1 in sand can generate 70Kg....

Or to think of it another way, if that's the case then if you pull a chain it will only start to move when the last link lifts of the ground, it won't move while there are still links touching the ground.

Only takes a moments thought to see that what he's saying bears no relationship to the real world.

 

[Neeves]

At last someone agrees with kellys eye! The anchor does nothing, it's all the chain.



Somehow the horizontal force on the chain appears from nowhere, or a few links of 8mm chain @ 5:1 in sand can generate 70Kg....

Or to think of it another way, if that's the case then if you pull a chain it will only start to move when the last link lifts of the ground, it won't move while there are still links touching the ground.

Only takes a moments thought to see that what he's saying bears no relationship to the real world.

I was obvious not very clear, I hope I clarified above.

Maybe I should have said 'for the anchor to be under sufficient tension (for the tension to be sufficient to impact the anchor such that it would move, and turn to reflect that change in tension direction then the chain would have been lifted). I don't know the tension is needed to turn the anchor, will depend on anchor and seabed - it will be much more than 70kg.

At some very low tension the friction of the seabed will be sufficient that there is no tension at the shackle end - I've never thought it would merit examination. But with my 5:1 30m 8mm the tension is the same at both ends - and no it does not suddenly come from nowhere.

Thank you for pointing out my post was unclear.

Hopefully this clarifies for GHA, as well.

Jonathan

 

[Neeves]

Great shots as a happy Delta owner (apart from distance to set) then it’s the first that I would worry about as the second is obvious.

Rupert,

You are an expert on Delta, these are both genuine Delta?