8mm Anchor chain?

[Ric]

I have a 30 ft. boat with 40m of chain and 20m of warp.

My friend has a 35' catamaran.
He had NO chain - just 60m warp. I spent years moaning to him about the terrible risk he was taking and hectoring him with the anchoring theory that we are all so aware of.
His response was that he had been sailing for 30 years and had never had an anchor drag. He is a very intrepid sailor who sails (and anchors) in the most unlikely places, so it was hard to argue with him.
A few years ago, just to shut me up, he put a couple of metres of chain on the anchor, (keeping the 60m of warp). Thankfully, we have had no dragging anchors, or I am sure he would have blamed the chain!
I am a disciple of the RYA and pile out my chain, as per RYA recommendations.

But, on his yacht, I have seen, for myself, that an all-warp scope can do the job, even in a ripping current in Jersey.

Maybe he is just lucky or maybe the importance of chain is overstated. Who knows?

It is somewhat counter-intuitive given their large windage, but catamarans are more stable and require less ground tackle at anchor than monohulls of similar LOA. I think that this is because they tend not to snake around like monohulls, because the anchor post is set so far back (almost amidships) and they can use a very long bridle-snubber which is cleated amidships too.

 

[coopec]

We NEVER ever had less than 100 meters of chain all 8ml plus 30 meter rope.

What size boat was that on?


(40 minutes later)

OK! OK! I've found it: 11x4.7 meter cat . And you "also carried two more anchors with 60 meters of chain"
I'm with you now...................

 

[coopec]

Well, we know where to come when we want advice on anchoring don't we!

Yachting Monthly anchor chain test | Yachting Monthly
www.yachtingmonthly.com/videos/.../yachting-monthly-anchor-chain-te...
Dec 10, 2012 - Yachting Monthly's expert metallurgist Vyv Cox tests various samples of 8mm anchor chain - grade 30 and 40 - from Europe and the Far East ..

 

[Niander]

Is your friend wise? does he not realise the warp could chaff through on a rocky bottom...then what?
ALL chain can never do that of course

 

[vyv_cox]

But, on his yacht, I have seen, for myself, that an all-warp scope can do the job, even in a ripping current in Jersey.

Maybe he is just lucky or maybe the importance of chain is overstated. Who knows?

Modern theoretical studies show pretty conclusively that the weight of the rode has no effect when it comes to holding. A decent anchor does not care if the rode is not lying on the bottom, it will hold perfectly well with its shank at an upward angle. Those of us who can swim in clear water when the wind is fresh to strong and watch what is happening can confirm the theoretical findings - at winds of over about force 6 the rode will be off the bottom and pretty much straight, whether rope or chain. It follows that an all-rope rode will hold as well as an all-chain one but it has two distinct disadvantages:
1. Wear of the rope on the bottom. In mud maybe not too bad but those who sail where there is coral suggest that rope can be cut through in very short order
2. Boats on all rope wander all over the anchorage in light winds, especially when the wind direction varies due to surrounding hills. Several posters have described having rope wrapped around keels, rudders and props due to this effect. I have seen several collisions between anchored boats on chain and rope.
Some more minor benefits of chain - it stows far more easily in most lockers, especially with a hawse pipe. When berthing stern-to on anchor the chain helps to keep the boat straight in crosswinds. When the wind is shifty the drag of the chain over the bottom seems to provide some stability.

 

[Sarnia]

Modern theoretical studies show pretty conclusively that the weight of the rode has no effect when it comes to holding. A decent anchor does not care if the rode is not lying on the bottom, it will hold perfectly well with its shank at an upward angle. Those of us who can swim in clear water when the wind is fresh to strong and watch what is happening can confirm the theoretical findings - at winds of over about force 6 the rode will be off the bottom and pretty much straight, whether rope or chain. It follows that an all-rope rode will hold as well as an all-chain one but it has two distinct disadvantages:
1. Wear of the rope on the bottom. In mud maybe not too bad but those who sail where there is coral suggest that rope can be cut through in very short order
2. Boats on all rope wander all over the anchorage in light winds, especially when the wind direction varies due to surrounding hills. Several posters have described having rope wrapped around keels, rudders and props due to this effect. I have seen several collisions between anchored boats on chain and rope.
Some more minor benefits of chain - it stows far more easily in most lockers, especially with a hawse pipe. When berthing stern-to on anchor the chain helps to keep the boat straight in crosswinds. When the wind is shifty the drag of the chain over the bottom seems to provide some stability.

Theoretical studies or not, we know that anchors bury when the shank is parallel with the sea bed, as a result of enough chain put out in the depth anchoring in, and a good catenary ensures this. I have my doubts if all light rode can do the same as the chain does. I have seen my chain in high winds (I put out 5 : 1 depth 10mm) pull straight, but the anchor has been properly set in the first place so no dragging. I have no confidence in the all rode arguement, which, IMO does not have the weight to set the anchor properly, despite what has been said in previous posts, might be ok for small fishing boats but not for me thank you.

 

[KellysEye]

As said it depends how much depth you anchor in and you might need rope to keep the weight down on the bows. There is not a fixed multiple of chain for depth: 12 feet requires 10 x depth, 25 feet 8, 35 feet 6 x, 45 feet 4 x. Its the weight of the catenary that matters as the wind picks up, that's why you need so much chain at 12 feet.

 

[vyv_cox]

J

Theoretical studies or not, we know that anchors bury when the shank is parallel with the sea bed, as a result of enough chain put out in the depth anchoring in, and a good catenary ensures this. I have my doubts if all light rode can do the same as the chain does. I have seen my chain in high winds (I put out 5 : 1 depth 10mm) pull straight, but the anchor has been properly set in the first place so no dragging. I have no confidence in the all rode arguement, which, IMO does not have the weight to set the anchor properly, despite what has been said in previous posts, might be ok for small fishing boats but not for me thank you.

My kedge, a Fortress on a rope rode, sets perfectly well every time. I use it as a kedge or as a second anchor set at 90 degrees to the bower in strong winds. Never had an issue with it not setting or not holding.

 

[NormanS]

When berthing stern-to on anchor the chain helps to keep the boat straight in crosswinds. When the wind is shifty the drag of the chain over the bottom seems to provide some stability.

Yes, but you've already told us that all the chain will be off the bottom in F6, so how is that going to work?

 

[vyv_cox]

Yes, but you've already told us that all the chain will be off the bottom in F6, so how is that going to work?

Not sure which 'that' you are talking about. For the first, I wouldn't even try to berth stern-to in a F6 crosswind. For the second, I find that wind rarely blows constantly over F6, there are always lulls.

 

[Sarnia]

J

My kedge, a Fortress on a rope rode, sets perfectly well every time. I use it as a kedge or as a second anchor set at 90 degrees to the bower in strong winds. Never had an issue with it not setting or not holding.

I have a kedge which has 10m of 8mm plus rode, but despite your success with just rode, I could not sleep well at anchor doing the same as you do with rode alone, but each to his own.

 

[J Neeves]

I'm with Vyv on this, above 30 knots the chain is effectively straight - there is minimalist catenary and what there is will not stop snatch loads - at over 30kn the yacht and anchor are effectively joined by a long bit of straight wire. Of course you can extend the 'nominal' 30 knots to maybe 32 knots by using 12mm chain instead of 10mm chain and deploying 100m instead of the 50m most might have - but you can equally sail with 2 gorillas permanently sitting on the bow. If you want to avoid snatch loads - get a decent snubber. Failure of brand name chain is notable by its absence, so its safe - its advantage is that it has abrasion resistance and it fits your gypsy - but if you could find piano wire of the correct strength (which you cannot) then it would do just as well when the winds are over 30 knots. AS with rope - in light winds you might tend to wander - but that is a different issue (drop your second anchor off the bow allowing it to just skip in the surface - it will stop the wander.

The idea that the anchor needs to have the chain 'on the seabed' is another phurphy. When an anchor is well set the shackle end of the shank has completely disappears along with a good few metres of chain. Under the seabed you have a reverse catenary. A fully set and buried anchor, that has reached its ultimate diving (setting) depth will have the angle between shank and the first link(s) at about 30 degrees - so a 30 degree, upward, pull, through the seabed.

If your anchor is too big, of course, it will not reach maximum efficiency but it will always remain in sight with bits of it sticking our of the seabed. If the seabed is very hard it might reach ultimate diving depth very quickly etc

Its all about accepting compromises.

Jonathan

 

[Sarnia]

As said it depends how much depth you anchor in and you might need rope to keep the weight down on the bows. There is not a fixed multiple of chain for depth: 12 feet requires 10 x depth, 25 feet 8, 35 feet 6 x, 45 feet 4 x. Its the weight of the catenary that matters as the wind picks up, that's why you need so much chain at 12 feet.

Can you explain your figures please, 12 feet requires 10 x depth. etc, what is the 10 in the equation, and 8, 6, and 4.
There is from my experience a recommended multiple for anchoring with chain, which is 5m of chain for 1m of depth.

 

[J Neeves]

Depth, to determine scope ratio, should be measured from the bow roller to the seabed at high tide. Think 3:1 for lunch, 5:1 min overnight, beyond 7:1 there is little advantage of deploying more - and there might not be room anyway. Optimise your scope ratio for between 5:1 and 7:1 and 'learn' how to anchor safely with those numbers - use a 10m nylon snubber!

Jonathan

 

[Sarnia]

Depth, to determine scope ratio, should be measured from the bow roller to the seabed at high tide. Think 3:1 for lunch, 5:1 min overnight, beyond 7:1 there is little advantage of deploying more - and there might not be room anyway. Optimise your scope ratio for between 5:1 and 7:1 and 'learn' how to anchor safely with those numbers - use a 10m nylon snubber!

Jonathan

+1 to that.
I also agree with your earlier post, I have often found, when conditions allow and I feel like a swim, my anchor, as you noted, buries itself and the shaft plus some chain. Never been to look what happens to it in 30knts wind! but the chain has been taught and shivers with the strain. I use a snubber to absorb the shocks, which is fastened to a large staghorn cleat forward of the gypsy, which also takes the load from the gypsy. Compromises are essential when the circumstances dictate them, or the old maxim...needs must when the devil drives.

 

[noelex]

This is our Fortress holding us on temporary basis @ 4;1 in 5m of water on an all rope rode.

The anchor has set reasonably despite the absence of chain and reasonably modest scope. Look at the angle of the rode.

 

[NormanS]

The people who anchor with rope are happy.
The people who anchor with chain are happy.
Why try to change each others point of view?

 

[J Neeves]

Because coral has an insatiable appetite for nylon! Rocky anchorages might be a bit less forgiving maybe 2 nights of safety vs one night for nylon in coral - but unless you only anchor in mud or sand (which many do) then never use an all nylon rode. It has nothing to with weight, or catenary - its all about abrasion. But even sandy anchorages have old concrete mooring blocks etc etc - its a compromise - be aware of the risks and you then can make your own informed decisions.

On the last but one Vendee Globe one of the competitors anchored at Auckland Island part of but way south of S Island NZ, its around 30 degrees south, for repairs. He used a Fortress FX 55 the rode was eaten through overnight - he then deployed his second FX 55. When he left he simply cut the rode (difficult to retrieve an anchor single handed in an Open 60).

Jonathan


Jonathan

 

[Sarnia]

This is our Fortress holding us on temporary basis @ 4;1 in 5m of water on an all rope rode.

The anchor has set reasonably despite the absence of chain and reasonably modest scope. Look at the angle of the rode.

I accept what you say, an exchange of views and experiences very useful, but my honest comment is that I believe the anchor looks ready to break out, a very tempory hold whilst having lunch in calm conditions. I prefer to stick to what has kept me safe in both good and bad circumstances as you do what is best for you.

 

[J Neeves]

Sarnia,

Fortress (and Danforth) set differently to other anchors in that the shank does not disappear until all the fluke is buried, and these anchors have huge flukes. Consequently though you can see all the shank, all the fluke is buried. If you apply further load, in the same direction, you can start burying the shank. One of the complaints of Fortress is that after a big blow they can at times be impossible to retrieve - simply because they set so deeply - but this is much better than an anchor that does not set easily and your yacht drags (or worse).

In thin mud, mud and sand - a Fortress has a higher holding capacity, for its weight, than any other anchor. For its surface area its incredibly light and easy to dinghy out, or throw when in panic mode.

They are difficult to stow on many bow rollers (and that long stock is a hazard to spinnaker sheets) but we never leave home without one! And both Noelex and Vyv declare to caring one, as standard. Ours, FX 23 (8kg) fits neatly assembled into our bow locker, with its chain/rope rode in an anchor crate (that some might call a milk crate) and I can deploy in an instant and a half, less easy to throw a 20kg steel anchor very far.

Compromises

But you go with what you are comfortable with - as you rightly say - its your experiences that allow you to sleep soundly and my experiences in Oz are different to yours in, wherever.

Jonathan