its the anchor not the chain

[geem]

I have heard people say that the anchor chain does most of the work when you anchor and it doesn't matter what anchor you have on the end. To dispel that myth, here's my recent experience.
44ft ketch, 18 tons or so, 13ft of water anchored off beach in lee of land gusting 40 kts but sea no more than 1ft due to shelter from land. I snorkelled on the anchor to check how well dug in. We have 120ft of chain out and a 30kg spade anchor. only the last 5ft of chain was contacting the sand. The anchor was well buried with little showing. the anchor had set in its own length.
under extreme conditions I suspect there will be no anchor chain in contact with the sea bed so you better get an anchor you are confident in.

incidentally, in the last week we have been anchored here in Caribbean, at least six yachts have dragged. They are all French without exception. they never put enough chain out and have tiny Brittany anchors!

 

[TimBennet]

The easiest way to disprove the "chain does all the work", is to remove the anchor and just lay out the chain next time you want to spend the night somewhere. But don't be in a hurry to go to sleep - I think you would drag!

The other clincher is that I can move 200ft of 5/16th chain across the boatyard by pulling on one end. But if I put the anchor on and dig it in, I then can't move it with the yard's little tractor, let alone pulling by hand.

 

[vyv_cox]

This is one of noelex' photos, showing my Rocna with a scope of around 4:1 being pulled at 2500 engine rpm in astern. This is about equivalent to force 6. Chain is completely off the bottom. I have swum and observed all chain off the bottom and gusts acting on the anchor shank with a scope of 10:1 in winds of force 6-7.

Confirming what TimBennet says, I have pulled my 60 metres of 8 mm chain along the yard, admittedly not very far, even at my advanced age and diminishing strength.

 

[ghostlymoron]

This sounds like a candidate for the 'myth busters' thread.

 

[TradewindSailor]

Yes, but the length is important due to the angle of pull on the anchor ..... and the elasticity in the system, either by having nylon rode or a heavy chain, to absorb the dynamic loads in the system. If the dynamic loads are not absorbed in extreme weather either the anchor will be unseated, the deck gear will be damaged, or the anchor system itself could be damaged.

Spades, Rocnas, Manson Supremes, can all work with an upwards pull on the shaft, better than say a CQR, but within reason.

 

[macd]

No-one's disputing that, Tradewind, but some (one in particular) harp on dogmaticalay about the chain doing everything. It really doesn't bear even humouring.

 

[charles_reed]

No-one's disputing that, Tradewind, but some (one in particular) harp on dogmaticalay about the chain doing everything. It really doesn't bear even humouring.

Mac,

There are still some people who believe fervently that the world is flat and the sun and stars revolve round us. (and not all in the funny farm). There are others who believe the chain does ALL the work and finally those who believe chain alone is all you need for anchoring in high winds.
If they're happy in their beliefs, who are we to disabuse them and cause unhappiness.
So as a matter of human kindness we should, perhaps, humour them and NEVER anchor downwind of them.
In answer to the slanderer of the poor old Brittany - if you use 6:1 scope to pull it in @ full revs in reverse it'll hold as well as any other (until a wind shift).

 

[danbridger]

If its the anchor, not the chain, am I wasting my time carrying 1/2 a ton on chain around at the front of the boat. Should I ditch it for string and is there any logic in using twice as much string as I would chain when anchoring.
I have a light boat and no windlass and would love to lose the weight [and still sleep soundly]

 

[geem]

Mac,



In answer to the slanderer of the poor old Brittany - if you use 6:1 scope to pull it in @ full revs in reverse it'll hold as well as any other (until a wind shift).

I have nothing against Brittany anchors. I just don't believe they should be used as the main anchor. In the gusts we have been getting here the wind direction has shifted about 70 degrees. With only one anchor set, that looked too small for the size of boat, far too little chain and the wrong anchor for the application, it's no wonder so many French yachts have dragged.
The other observation here is that the French yachts drag across the anchorage then stop about 6feet from your bow. They then put fenders out rather than moving! We have seen a few heated exchanges with other nationalities. The french seem to wait until they have hit you before they up anchor!! Half the boats here are French so not surprising they are dragging but they do seem to be ill prepared.

 

[macd]

If its the anchor, not the chain, am I wasting my time carrying 1/2 a ton on chain around at the front of the boat. Should I ditch it for string and is there any logic in using twice as much string as I would chain when anchoring.
I have a light boat and no windlass and would love to lose the weight [and still sleep soundly]

Not necessarily all-string, but there are plenty of learned advocates of lighter chain, especially if the stronger stuff (G70).

 

[Skylark]

This is one of noelex' photos, showing my Rocna with a scope of around 4:1 being pulled at 2500 engine rpm in astern. This is about equivalent to force 6. Chain is completely off the bottom. I have swum and observed all chain off the bottom and gusts acting on the anchor shank with a scope of 10:1 in winds of force 6-7.

Confirming what TimBennet says, I have pulled my 60 metres of 8 mm chain along the yard, admittedly not very far, even at my advanced age and diminishing strength.

I hope that no seahorses were harmed during the making of this post

 

[alahol2]

If its the anchor, not the chain, am I wasting my time carrying 1/2 a ton on chain around at the front of the boat. Should I ditch it for string and is there any logic in using twice as much string as I would chain when anchoring.
I have a light boat and no windlass and would love to lose the weight [and still sleep soundly]

There are thousands of weight sensitive boats that anchor to a combination of chain (chafe mitigation) and rope. Our last boat was a 32ft cat, we anchored to 5m of chain and the rest was multiplait rope. You don't need much more scope than you would use with all chain. Once successfully anchored we very rarely dragged. The only real downside of rope is that the boat does tend to range about, particularly in light winds and currents, when boats that are anchored with chain are actually lying to the chain rather than the anchor.

 

[vyv_cox]

If its the anchor, not the chain, am I wasting my time carrying 1/2 a ton on chain around at the front of the boat. Should I ditch it for string and is there any logic in using twice as much string as I would chain when anchoring.
I have a light boat and no windlass and would love to lose the weight [and still sleep soundly]

As always, pros and cons. Current thinking is that the rode has no function other than joining the boat to the anchor. Going to something lighter but with equal strength is theoretically just as effective. So rope for example although Alain Fraysse says you need to increase scope in order to reduce the angle that the shank makes with the seabed. To my mind, if the chain is a straight line anyway, as the rope would be, it makes no difference so maybe the old idea of increasing scope for rope needs to be re-thought? However, his winner is a short chain and long rope. But anyone who has shared an anchorage with a boat on all, or mostly rope, will know what a PITA they can be, dancing all over the anchorage with every puff of wind.

Chain does offer some excellent properties for rodes, principally its wear resistance, but it also counters the all-rope problem, providing excellent stability in lighter winds. For stern-to berthing in the Med it also has the valuable property of not being cut when some idiot gets it around his prop!

Now that Grade 70 chain is more widely available in galvanised versions this provides a beneficial solution, e.g. going from Grade 30 10 mm to Grade 70 8 mm saves 90 kg and nearly doubles the strength. Unfortunately chain in Grade 70 at sizes less than 8 mm is extremely rare or non-existent.

This season I intend experimenting with some thin cable as an anchor rode, at first using an anchor and chain as backup.

 

[lw395]

Does anyone actually use all rope, without even a couple of metres of chain to take the worst of the chafe?
When we've done this for race marks, the wear on the rope is often a bit alarming IMHO.

 

[doug748]

Mac,

There are still some people who believe fervently that the world is flat and the sun and stars revolve round us. (and not all in the funny farm). There are others who believe the chain does ALL the work and finally those who believe chain alone is all you need for anchoring in high winds...........
).

Just that.

There are not many of these people.

Perhaps we could just send them a PM next time.

 

[johnalison]

Does anyone actually use all rope, without even a couple of metres of chain to take the worst of the chafe?
When we've done this for race marks, the wear on the rope is often a bit alarming IMHO.

Only once. I decided for some reason to use only line in the form of anchor tape on a reel with a 10Kg Bruce as a stern anchor in a Swedish harbour. It dragged.

 

[Jeva]

geem, you don't mention the size of your chain but my first reaction to your commentary was to ask myself if a 30kg anchor was sufficient for an 18 ton yacht? But I'm sure your happy with it.

 

[vyv_cox]

Does anyone actually use all rope, without even a couple of metres of chain to take the worst of the chafe?
When we've done this for race marks, the wear on the rope is often a bit alarming IMHO.

I understood from reading these pages that Fortress suggested using no chain at all, just connect the rope to the shackle. However, I have now looked them up and find they recommend a minimum of 2 metres at a depth of 8 metres, adding 2 metres of chain for every further 8 metres of water. http://fortressanchors.com/resources/safe-anchoring-guide

I have about 5 metres of chain on mine but it would mostly be deployed in less than 8 metres.

 

[jdc]

Does anyone actually use all rope, without even a couple of metres of chain to take the worst of the chafe?
When we've done this for race marks, the wear on the rope is often a bit alarming IMHO.

I have, but at the end of 200m of rope (it was 75m deep!). We didn't want to have to haul the weight of the chain all that way up again.
It held while the rest of the fleet went backwards on the tide.

BTW, of course it's the anchor which holds all the horizontal force. Even those like me who believe that the catenary is of some use some times make the assumption that the horizontal component of force is constant along its length, which is to say the friction on the chain is effectively zero - otherwise the maths wouldn't give rise to a catenary.

 

[lw395]

....
BTW, of course it's the anchor which holds all the horizontal force. Even those like me who believe that the catenary is of some use some times make the assumption that the horizontal component of force is constant along its length, which is to say the friction on the chain is effectively zero - otherwise the maths wouldn't give rise to a catenary.

That may only be strictly true in the steady-state case, chuck in a few waves and consider the damping effect of the rode moving through the water.....
The sums get very complex very quickly.

I met people who believe all sorts of old nonsense (about time we had a lee bow thread?...) but never anyone who tod me I didn't need an anchor.