Tranona
Well-known member
Why? Heavy chain makes no difference to holding power and the dampening effect of catenary can be achieved using a snubber
Worth the difference G40 v G70 anchor chain
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Neeves
Well-known member
I'm answering Post 17
As Tranona says if you use a snubber it performs exactly the same role as catenary. Both transfer energy, catenary by straightening the catenary, a snubber does it by stretching. A difference is you carry unnecessary weight in the bow with chain and catenary works with diminishing returns, viz as the catenary straightens it can accept less and less energy (it becomes more difficult for the catenary to further straighten). A good snubber will cont9inue to stretch 'roughly' linearly.
In the graph both chain and rope perform similarly upto about 300kg of tension - beyond 300kg of tension the chain has little ability to convert increased energy (from the wind) - but the rope continue to stretch (its not linear - but almost as good as).
Most people are going to use a combination, a snubber and chain - so they have the advantage of both chain and a snubber. Chain offers abrasion resistance, the snubber offers a better ability to manage snatch loads using a short chain rode combined with the snubber.
Most new yachts sold today (which are going to become AWBs) and most 'recent' AWB are lightweight and will have better sailing characteristics if not overloaded in the bow (with heavy chain in the anchor/chain locker). Heavy chain is not such a disadvantage if you own an older yacht. New or newer yachts - its a different story.
Jonathan
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Seven Spades
Well-known member
I think a heavy chain will cause the anchor to be pulled horizontally along the sea bed which gives the anchor more holding power. Take an extreme case and replace te chain with nylon and the effect would be to lift the shank pulling out the anchor. In bad weather we pay out additional chain becaure the strain on the chain tends to lift the shank. The longer chain both reduces the angle but also adds weight thus requiring more force to lift the shank. therefore a heavier chain increases holding power.
NormanS
Well-known member
I'm sure that your oft repeated graph means something to some people. It is noticeable, however, that it conveniently omits any information regarding depth. It's obvious that if anchoring in shallow water, chain will not give much useful catenary. Conversely, when anchoring in deeper water, the weight of chain gives a very useful catenary. There is good reason for deploying a stretchy snubber in shallow water, but in deeper water, decent sized chain is perfectly adequate, and much simpler.
Neeves
Well-known member
30m of (decent sized?) 10mm chain, 5:1 scope - all given in the graph - what more do you need? Deeper water can mean less shelter (more wind), closer to open seas (more chop) - you takes your choice more shelter less catenary or.....
Jonathan
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Tranona
Well-known member
That may be true of certain types of anchor, notably the CQR which does indeed tend to "plough" when the chain is straight and perhaps the reason for heavy chain in the past. However modern design anchors set in a different way and holding power is not affected by the angle of the rode. Once wind speed gets to around 26 knots the rode becomes effectively straight and the role of the rode is then just connecting the boat and the load to the anchor.
The only benefit of heavier chain is the added weight which increases catenary, but the difference between say 8 and 10mm is small. Catenary does of course limit swinging room in crowded anchorages, but a similar effect can be achieved with a snubber. The downside of heavy chain is weight at the bows of the boat and cost with no advantage in holding power - that comes from the design of the anchor.
Good explanation here petersmith.net.nz/boat-anchors/catenary.php
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Neeves
Well-known member
Time for a bit of lateral thinking
The young lady is using a snubber, sorry bungee, and when she reaches the bottom of her descent does not feel any tension, or not much, in her ankles.
The next step is unpalatable - but bear with me - its just in your imagination.
Say she replaces the snubber, aka bungee, with chain......
This is what you are suggesting no dampening of the forces of nature.
If you have a look at the graph at 300kg, 30m of 10mm chain 5:1 scope, there is effectively no catenary, or any more of any use, left in the rode - the ability of the rode to take an increased tension and further reduce the effect of catenary has gone - what you have left is snatch loads, on the yacht and the anchor. The snatch loads you feel on the yacht are the same as on the anchor - you are connected.effectively, by an inextensible wire.
The anchor will hold, as Tranona says, anchors offer a huge safety margin. Its not the anchor dragging you need worry about - but the strength of the device securing the rode to the yacht, your back up.
You can of course deploy more chain - how much do you carry - in your chosen anchorage, howe many people do you have to your stern (when the chips are down good anchorages are like a honey pot for wasps.
No worries - you don't need to deploy more chain just extend your snubber - surely you have 2 x deck lengths of 10mm nylon
Add a bungee, sorry snubber, and you could hold the snubber in your hands (try that with your chain, no snubber.) Its uncanny - you know the tension in the rode is around 300kgs, 30/35 knots, you have a decent snubber attached and you release the snubber and are easily able to hold it in your hands, not even gloves - the tensions (like the effects of a glass of decent whisky) all melt away.
The rule of thumb, which might not be correct, is that a fit healthy young male can hold the tension of his weight - I should thus be able to hold 70kg - but I know the wind will develop 300kg in an, our, all chain rode - but its all gone, well almost all gone at the end of the snubber - that's one reason I use a snubber.
We used a 15kg steel Excel, replaced by a 15kg aluminium Excel. We also carried a 8kg aluminium Spade and would happy use either of the aluminium anchors. We would power set either anchor at a 3:1 scope at a depth of 15' - 30'. If it did not set - they always set - we would move. If they did not set the holding was insufficient - move. Our anchors would set at 3:1, 2 x 20hp Volvos, so 400kg of tension. If the anchor held we would then deploy more rode to be appropriate for the location/conditions etc.
Why 3:1? - why deploy more if you are prepared to move as it is simply more to retrieve.
Jonathan
Neeves
Well-known member
For the sceptics - some bedtime reading.
The first and second last articles make a good introduction - and that second last article particularly opens a complete can of worms. The Scilly storm was experienced by some members here - some of whom were waiting to cross the Atlantic - and on hearing the forecast retreated to more comfortable locations. Forecasts are now sufficiently reliable that there no bragging rights in enduring bad weather - sailing is meant to be a pleasure not an SAS endurance test - but prepare for the worst.
Storm tactics at anchor: Surviving gales in Scilly - Yachting Monthly
The art of snubbing, in the nicest possible way
Anchor Snubber Tips - Sail Magazine
https://www.cruisingworld.com/story/how-to/safety-at-sea-surviving-a-powerful-storm-in-the-med/
https://www.sailmagazine.com/diy/how-to-dealing-with-snatch-loads-in-an-anchorage
For gluttons there are more articles on specific topics, chain hooks, yawing etc etc.
Heavy chain costs more, needs a bigger locker, needs a bigger windlass, needs more power. Heavy, or more, chain increases the benefits of catenary but a snubber does exactly the same by using elesticity, costs peanuts and weighs, almost nothing. There is absolutely nothing wrong with heavy chain - provided you accept the down sides - have I mentioned more weight, sacrificing sailing characteristics, costs more, needs a bigger windlass and more power - think bigger power cables.....maybe bigger battery
The 2 drums on the left contain 50m of G30 8mm chain, the two drums on the right contain 75m of 6mm chain. The 6mm chain has the same UTS and WLL as the 8mm chain (I checked them both). The 6mm and 8mm chain use the same shackles, UTS 10/12t; WLL 2t; 3/8th" shackles. The 6mm chain does need 'connectors' to take the same sized shackles but its an easy addition and done once. You can source the shackles and the connectors easily, mail-order or off the shelf, in the UK.
6mm chain attached with an Omega link to a 3/8th" shackle and a 15kg SHHP steel anchor.
Jonathan
The first and second last articles make a good introduction - and that second last article particularly opens a complete can of worms. The Scilly storm was experienced by some members here - some of whom were waiting to cross the Atlantic - and on hearing the forecast retreated to more comfortable locations. Forecasts are now sufficiently reliable that there no bragging rights in enduring bad weather - sailing is meant to be a pleasure not an SAS endurance test - but prepare for the worst.
Storm tactics at anchor: Surviving gales in Scilly - Yachting Monthly
The art of snubbing, in the nicest possible way
Anchor Snubber Tips - Sail Magazine
https://www.cruisingworld.com/story/how-to/safety-at-sea-surviving-a-powerful-storm-in-the-med/
https://www.sailmagazine.com/diy/how-to-dealing-with-snatch-loads-in-an-anchorage
For gluttons there are more articles on specific topics, chain hooks, yawing etc etc.
Heavy chain costs more, needs a bigger locker, needs a bigger windlass, needs more power. Heavy, or more, chain increases the benefits of catenary but a snubber does exactly the same by using elesticity, costs peanuts and weighs, almost nothing. There is absolutely nothing wrong with heavy chain - provided you accept the down sides - have I mentioned more weight, sacrificing sailing characteristics, costs more, needs a bigger windlass and more power - think bigger power cables.....maybe bigger battery
The 2 drums on the left contain 50m of G30 8mm chain, the two drums on the right contain 75m of 6mm chain. The 6mm chain has the same UTS and WLL as the 8mm chain (I checked them both). The 6mm and 8mm chain use the same shackles, UTS 10/12t; WLL 2t; 3/8th" shackles. The 6mm chain does need 'connectors' to take the same sized shackles but its an easy addition and done once. You can source the shackles and the connectors easily, mail-order or off the shelf, in the UK.
6mm chain attached with an Omega link to a 3/8th" shackle and a 15kg SHHP steel anchor.
Jonathan
NormanS
Well-known member
Maybe where you sailed, but deeper water doesn't automatically mean less shelter or proximity to open seas, where some of us anchor. It's not a choice between more shelter or less catenary.
I sometimes deliberately anchor in deep water in perfectly sheltered bays, when bad weather is expected, knowing that the catenary of my chain will work better.
Tranona
Well-known member
But only up to less than 30 knots of wind and then it becomes irrelevant. Over30 knots catenary has no effect on the holding power of the anchor. So it depends on what you mean by "bad weather"
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NormanS
Well-known member
That's a very strange comment to make. You say, "Under 30 knots catenary has no effect on the holding power of the anchor". Do you really believe that? If so, we're in different worlds.
Yes, that's true in very shallow water. I don't consider 30 knots of wind bad weather. I sail off the West Coast of Scotland.
noelex
Well-known member
Where heavier chain is of significant benefit is assisting the anchor develop an initial set.
When the anchor first begins to grab the seabed, it possesses limited holding power, resulting in a relatively low force. However, the superior catenary of heavier chain assists in maintaining a more horizontal pull on the anchor during this initial phase. The catenary becomes a helpful factor at this stage due to the low force exerted.
Modern anchors set so well that this superior reliability when setting rarely comes into play, but it does help in most difficult substrates, which is arguably when enhancing anchoring performance is most needed.
Despite these advantages, there’s a substantial price to pay in the form of additional weight.
When the anchor first begins to grab the seabed, it possesses limited holding power, resulting in a relatively low force. However, the superior catenary of heavier chain assists in maintaining a more horizontal pull on the anchor during this initial phase. The catenary becomes a helpful factor at this stage due to the low force exerted.
Modern anchors set so well that this superior reliability when setting rarely comes into play, but it does help in most difficult substrates, which is arguably when enhancing anchoring performance is most needed.
Despite these advantages, there’s a substantial price to pay in the form of additional weight.
Tranona
Well-known member
Yes - it is you perhaps that are in a different world by denying the physics and the ample evidence that the holding power of a specific anchor is a function of the load applied and the nature of the substrate. What connects the anchor to the load is irrelevant. You could replace your 10mm chain with rope and the holding power would be exactly the same. Plenty of evidence posted here regularly demonstrating this but you do not seem to accept nor offer any evidence to support your view other than "it works for me" - but it works the same for everybody. It is totally irrelevant where you sail - the forces are the same in Scotland, Solent or Australia. The figure of 30 knots is at the high end of estimates of when the catenary effect disappears. If you look back over the threads on this subject you will find real life tests, for example by Vyv Cox and Neeves which. prove this.
There are benefits of catenary as I (and many others) have explained but improving holding power in higher wind speeds (and therefore higher loads) is not one of them.
NormanS
Well-known member
So why do you say that in winds of less than 30 knots, catenary has no effect....?
Tranona
Well-known member
My apologies that was clearly an error and should say "over" - now corrected, although the previous sentence made it clear that under 30 knots catenary has some relevance, though not necessarily to the holding power of the anchor.
I hope my subsequent, more detailed explanation makes this even more clear.
NormanS
Well-known member
Hi Johnathan,
Not sure about the relevance to this thread, of your last photo of a chain attachment to an anchor, but as a (retired) mechanical engineer, I'm not impressed by the finish detailing of the anchor. I don't know, or really care, what make it is, but the sharp edges on the attachment slot are horrible. It is evident in the photo that instead of the shackle load being spread over an area, it rests only on the two sharp corners of the slot. Not good engineering practice.
Neeves
Well-known member
You said in an earlier post something about smaller chain needing more complex attachment than a 'standard' sized chain. I was illustrating the connection was very, very simple - even I can achieve a robust and safe connection. All the components are significantly over strength - the shackle has a 2t WLL, whereas the chain is only 750kg or 1t. The Omega link has a WLL of 1t.
The shank used was a developmental product and just one I used to illustrate the connection and take some photographs. The fabricator has bought a machine to bevel edges since and the slot in the end of the shank has been 'rounded'. This change or addition was made not to improve the 'mating' of the 2 surfaces but to improve the galvanising which had suffered from chipping in the past. Nevertheless well spotted.
Jonathan
Neeves
Well-known member
I ponder
If yachts had been built since time began with 'smaller' chain, equipped with decent snubbers, and had windlass to suit with smaller power cables etc would we have a debate on the advantages of bigger chain? Looking at the advantages of bigger chain - the characteristics can all be achieved 'another way' - more cheaply and offering better sailing performance. The idea that heavy chain is an aid to setting an anchor is a complete phurphy - once the toe of a modern anchor engages - the anchor will set - that's how nearly all modern anchors are designed. In fact because a modern anchor buries the toe and the shackle end of the shank (holding the chain) simultaneously then a small chain provides less resistance to burial and having a bigger chain hinders anchor performance in every seabed. A well set anchor is one with buried chain - 6mm chain is much easier to bury than 8mm etc - especially in 'difficult' seabeds.
Similarly if we were not subject to the old salts fears would we ever consider using a bigger anchor than recommended by the anchor maker - it might, only might, have had value with a Fishermans, or CQR/Delta - but today - we have more than enough hold - tales of dragging anchors and yachts on beaches are almost consigned to history (and those who have not made the change to a modern anchor).
Changing chain, once your yacht is already equiped is expensive, as you also need a new gypsy - yacht builders today are bestowing unnecessarily large chain on new owners - which will largely remain unchanged for the life of the yacht - yacht builders have a lot to answer for.
If yachts had been built since time began with 'smaller' chain, equipped with decent snubbers, and had windlass to suit with smaller power cables etc would we have a debate on the advantages of bigger chain? Looking at the advantages of bigger chain - the characteristics can all be achieved 'another way' - more cheaply and offering better sailing performance. The idea that heavy chain is an aid to setting an anchor is a complete phurphy - once the toe of a modern anchor engages - the anchor will set - that's how nearly all modern anchors are designed. In fact because a modern anchor buries the toe and the shackle end of the shank (holding the chain) simultaneously then a small chain provides less resistance to burial and having a bigger chain hinders anchor performance in every seabed. A well set anchor is one with buried chain - 6mm chain is much easier to bury than 8mm etc - especially in 'difficult' seabeds.
Similarly if we were not subject to the old salts fears would we ever consider using a bigger anchor than recommended by the anchor maker - it might, only might, have had value with a Fishermans, or CQR/Delta - but today - we have more than enough hold - tales of dragging anchors and yachts on beaches are almost consigned to history (and those who have not made the change to a modern anchor).
Changing chain, once your yacht is already equiped is expensive, as you also need a new gypsy - yacht builders today are bestowing unnecessarily large chain on new owners - which will largely remain unchanged for the life of the yacht - yacht builders have a lot to answer for.
vyv_cox
Well-known member
Indeed so. Last weekend I was presenting my anchors talk at the Cruising Association HQ in London. Someone asked a question about setting my Fortress kedge, which has a rode of 5 metres of 8 mm chain plus Anchorplait . I only ever throw it overboard, either from the dinghy or bow of the boat, and it never fails to set. I believe that Fortress say the chain is unnecessary. It most definitely does not need heavy chain.
Supertramp
Well-known member
I completely get the overengineering built into anchor rodes and many other aspects of yacht design. A light boat or anchor system is not of itself flimsy or prone to failure.
With chain, looking at WLL rather than breaking load, then 6mm offers 600kg, 8mm offers 1100kg and 10mm offers 1690kg. I just replaced my 10mm chain with the same size rather than 8mm because it was simple (gypsy wheel) and was in the original spec for the boat. My boat (like NormanS) carries about 3000kg more plastic, wood and metal than it technically needs to plus another 1000kg of fuel and water. Plus 8 sails and lots of gear etc. The extra 44kg of 10mm is insignificant in that lot! In view of the weight and respecting WLL rather than breaking load given that these numbers will decrease with wear and corrosion, I "felt" comfortable with 10mm.
If I had a lighter weight monohull or a multihull then I would sail with a different philosophy and less, lighter stuff. Chosen wisely I would not expect failures.
As a corollary, I was aboard my boat afloat in the marina during one of the vicious storms this winter (92mph recorded nearby). The forces generated by wind striking the boat in a sheltered marina were fearsome. This was shortly before I made the chain replacement decision!
With chain, looking at WLL rather than breaking load, then 6mm offers 600kg, 8mm offers 1100kg and 10mm offers 1690kg. I just replaced my 10mm chain with the same size rather than 8mm because it was simple (gypsy wheel) and was in the original spec for the boat. My boat (like NormanS) carries about 3000kg more plastic, wood and metal than it technically needs to plus another 1000kg of fuel and water. Plus 8 sails and lots of gear etc. The extra 44kg of 10mm is insignificant in that lot! In view of the weight and respecting WLL rather than breaking load given that these numbers will decrease with wear and corrosion, I "felt" comfortable with 10mm.
If I had a lighter weight monohull or a multihull then I would sail with a different philosophy and less, lighter stuff. Chosen wisely I would not expect failures.
As a corollary, I was aboard my boat afloat in the marina during one of the vicious storms this winter (92mph recorded nearby). The forces generated by wind striking the boat in a sheltered marina were fearsome. This was shortly before I made the chain replacement decision!