The Anchor is Just Decoration

[noelex]

There have been a number of anchor threads on YBW where posters have expressed the surprising view that it is the chain that really holds the boat. Such discussion has cropped up repeatedly in many anchor threads. Someone even suggested doing a trial and anchoring without the anchor.

I came across this example that proves that the chain on its own, or even with a weight attached to the end has very little holding power. Hopefully the photos prove the point.

It was a Kobra, but the skipper left out the bolt holding the fluke at the correct angle. This made the anchor little more than a dead weight. Of course if the chain was doing all the holding of the boat, the anchor being defective would make no difference and the boat would be held quite nicely.

As most of would expect this was not the case. The skipper re anchored three times and dragged slowly each time in the light wind. As he became more frustrated he laid out more chain with each attempt.

My wife explained the problem to the skipper and he subsequently fixed the anchor.

This was the photo of the anchor dragging. You can see it was lost in the disturbed sand. On each of the three occasions the boat dragged over 100m due to the ineffectual anchor.

This makes the missing bolt clearer. The anchor would not sit still.

I am afraid these are not good quality photos because of all the disturbed sand. I have been trying to take some better photos of anchors underwater to show what is going on. Here is a Rocna doing what an anchor should do which is a lot more that just decoration. (OK, this is really included just because it nice picture )

 

[sailorman]

was that on the East Coast

 

[claymore]

What a shame all that lovely yellow paint has been damaged.......

 

[prv]

I thought this was going to be a thread about people who cruise from marina to marina or the very occasional visitor's buoy, consider anchoring to be an advanced skill, and regard a night on the hook as something of an adventure

Pete

 

[AngusMcDoon]

I anchor with 2m of chain and the rest warp, with a Knox at the end. Never dragged. Can be a sod to get out sometimes though. When in mud it brings up an impressive splodge of sticky stinky stuff with it.

 

[GrahamM376]

There have been a number of anchor threads on YBW where posters have expressed the surprising view that it is the chain that really holds the boat. Such discussion has cropped up repeatedly in many anchor threads. Someone even suggested doing a trial and anchoring without the anchor.

I came across this example that proves that the chain on its own, or even with a weight attached to the end has very little holding power. Hopefully the photos prove the point.

It maybe depends on the bottom and what the chain may pass around. When using a trip line, the trip buoy is often out to one side of the boat after the tide turns, leaving the chain in a horseshoe with the anchor it would appear not taking the weight.

 

[lustyd]

It maybe depends on the bottom and what the chain may pass around. When using a trip line, the trip buoy is often out to one side of the boat after the tide turns, leaving the chain in a horseshoe with the anchor it would appear not taking the weight.

It may appear that way, but it would be quite foolish to come to the conclusion the anchor won't do anything from this very thin evidence. Even if this is initially the case after a tide turn, a small increase in current or wind and you'll be lying to the anchor in no time.

 

[noelex]

It maybe depends on the bottom and what the chain may pass around. When using a trip line, the trip buoy is often out to one side of the boat after the tide turns, leaving the chain in a horseshoe with the anchor it would appear not taking the weight.

Yes true, but the boat being held by the chain disappears at a very low windspeed, maybe 10 knots (or the equivelent force from current). Weedy substrates do provide a bit more grip on the chain, but around 15 knots is maximum. I suspect that without an anchor to fix one end the limits would be even lower.
In rock of course the chain can sometimes jam and hold the boat quite securely, but this is not a common situation.

 

[GrahamM376]

Yes true, but the boat being held by the chain disappears at a very low windspeed, maybe 10 knots (or the equivelent force from current). Weedy substrates do provide a bit more grip on the chain, but around 15 knots is maximum. I suspect that without an anchor to fix one end the limits would be even lower.
In rock of course the chain can sometimes jam and hold the boat quite securely, but this is not a common situation.

I wasn't suggesting that chain on its own is adequate but, in some circumstances such as low wind and slow moving water, it is the chain which is holding the boat in position, not the anchor.

 

[charles_reed]

was that on the East Coast

Most probably Greece.
Noelex ain't fool enough to try and take photos in the cold and murky N Sea.

 

[charles_reed]

I wasn't suggesting that chain on its own is adequate but, in some circumstances such as low wind and slow moving water, it is the chain which is holding the boat in position, not the anchor.

The very concept Noelex was trying to dissipate. It really is a fallacy!!

 

[charles_reed]

It maybe depends on the bottom and what the chain may pass around. When using a trip line, the trip buoy is often out to one side of the boat after the tide turns, leaving the chain in a horseshoe with the anchor it would appear not taking the weight.

Very true with light forces - you might get that impression - but the anchor is still acting as the pivot point. Mostly round UK coasts tidal streams in anchorages aren't much (except the Dyfi where spring ebb reaches 8 knots past the pier).

 

[vyv_cox]

I have posted this photo a couple of times but another won't hurt on this thread. Manson Supreme, a fairly large one on an Oyster 57. The scope is my estimated 25 metres in about 5 metres depth. The wind was initially south or southwesterly about F4-5 but veered to northerly 6-7 during the day, photo taken at 1800. The chain has clearly pivoted about the anchor tip. It looks like the anchor dragged maybe half a metre before resetting to the new direction. Our Rocna performed in exactly the same way.

 

[Chris_Robb]

I wasn't suggesting that chain on its own is adequate but, in some circumstances such as low wind and slow moving water, it is the chain which is holding the boat in position, not the anchor.

Recently we were anchored in 10 knots in a bay (Sporades). We dragged even in that wind. I dived on the anchor to watch what was happening. The anchor was completely buried in very loose sand and was dragging along under the surface leaving a cloud of suspended sand. The anchor was a Manson and 30 meters chain out in 5 meters depth.

So even at 10 knots of wind the anchor chain made little or no difference.

No doubt the chain only brigade will be along shortly!

 

[Greenheart]

No doubt the chain only brigade will be along shortly!

Hopefully. I read on here, late last year, that even a long chain lifts right off the bottom in surprisingly light conditions, thereby relying wholly on the hook at the end, for holding.

That seemed to fly entirely in the face of all the lessons I'd ever heard about the importance of catenary, and the point of carrying a huge weight of chain and handling gear.

I'd like to believe an anchor is all that's needed (aside from chafe-proofing the lower end of the rode) but if that really is the case, why do the majority still carry an all-chain rode?

 

[JimC]

I'd like to believe an anchor is all that's needed (aside from chafe-proofing the lower end of the rode) but if that really is the case, why do the majority still carry an all-chain rode?

In my experience (which is limited to British coastal waters) the only downside to using rope/chain rather than all chain is that the boat will move around the anchor more due to wind changes and inter-action between wind and tide. I wanted to lighten bows and have changed from all chain to 10 metres chain and balance rope and I believe holding power has not decreased. Agree that benefit of catenary seems to have been demonstrated to be a myth on this forum and elsewhere as chain lifts and pulls bar-taut in testing conditions.

 

[vyv_cox]

I'd like to believe an anchor is all that's needed (aside from chafe-proofing the lower end of the rode) but if that really is the case, why do the majority still carry an all-chain rode?

Wear, longevity, stowing, windlass grip, not wrapping around underwater parts, preventing the boat from dancing all around the anchorage, are the first few that come to mind. For stern-to berthing in the Med there are other significant benefits but that is maybe not so relevant here.

That seemed to fly entirely in the face of all the lessons I'd ever heard about the importance of catenary, and the point of carrying a huge weight of chain and handling gear.

My kedge is a Fortress weighing just a few kilograms, 5 metres of 8 mm chain plus 50 metres of Anchorplait. It holds just as well as my Rocna plus chain and provides its own snubbing. The late Hylas, (Alain Poireaud) inventor of the Spade anchor, was a strong proponent of rope rodes, other than a short length of chain, and used his in the Magellan Strait and other very windy places. His boat was a heavy 48 footer.

 

[jon711]

I suggest you advise the Royal Navy of your assertions. It would appear that they need to correct the Admiralty Manual of Seamanship (Part I) and forget those hundreds of years experience.

Jon

 

[Greenheart]

I suggest you advise the Royal Navy of your assertions.

I wasn't asserting, just asking. I bought 20ft of 6mm chain for my dinghy...and I plan to get 50ft of warp too. I just wondered whether my willing adherence to traditional wisdom is now regarded as mistaken.

 

[vyv_cox]

I wasn't asserting, just asking. I bought 20ft of 6mm chain for my dinghy...and I plan to get 50ft of warp too. I just wondered whether my willing adherence to traditional wisdom is now regarded as mistaken.

I feel certain you have already consulted the Alain Fraysse website. I believe that he and Alain Poireaud worked closely together. Despite the theoretical benefits of all-, or nearly-all rope rodes not all that many people use them for some of the reasons I have already given. Multihull sailors differ of course and many use rope to save weight.

However, there is an increasing number of cruising sailors who use Grade 70 chain a size down from the Grade 30 they would otherwise have used to save weight in the bow locker. Paul Chandler followed this route when refitting Lynn Rival, 8 mm Grade 70 instead of 10 mm Grade 30. Interestingly, I received an email flyer from Jimmy Green advocating that practice only yesterday.