Tandem anchoring

[Quandary]

In a recent thread someone was advocating using two anchors in tandem. Idly thinking about it this afternoon while polishing some bits, it occurred to me that though I have always carried two anchors, I have never tried using them in that way. In fact, I think I have only ever had both out once or twice. I anticipate that if it was ever necessary it would be in pretty grim conditions so it would be worth knowing how to do it as it seems very vulnerable to a foul up, and if that happens with both anchor already out the trouble could be major. I recall seeing diagrams for the practice which seemed a bit theoretical.
Anyone used this method routinely? I presume you put your best anchor out first, but this is generally the one with the best and longest chain, or do you switch the shorter chain on to the heavy anchor? Is the second anchor connected directly to the end of the first chain or is the first chain joined some distance back from the anchor on the second chain. If the first chain is attached directly to the second anchor I presume that anchor is simply acting as an anchor weight as it would be dragged about as the boat swings, but alternatively, if the two chains are joined behind the anchor is there an optimum distance to avoid a foul up, and how do you prevent the chains tangling with the anchor as the boat swings?
Is tandem anchoring a sensible idea at all? Or am I better with my former technique of laying the two anchors at about 30 degrees apart and adjusting scope as if the wind swings? Or perhaps the sensible man keeps his second anchor aboard until the first one is definitely dragging and then uses it as a last resort or should we just stay in a cosy marina.

 

[Billjratt]

I had the most horrible tangle using two anchors and ended up having to motor to the nearest club nautico with a football sized clump of chains dangling over the front and a mountain of chains and anchors on deck. NEVER AGAIN.
I would try the tandem method next time I smell trouble in the air.
How you go about it depends on what you've got...
The book says don't shackle to tripping eyes etc ( on a CQR for instance), shackle a loop round the shank just where it articulates and lay the secondary andchor by hand until the chain is out, then drop the main bower in the usual fashion while continuing to drop astern.
Dig in as well as your power will allow, the weather demons will complete the job for you.
Recovery obviously involves a bit of strong arm as the bower comes aboard, since it will be neccessary to hand haul the next bit of chain until you can clear the gypsie and get the new chain on. Meanwhile, I hope somebody else is on the helm keepng control!!

 

[Searush]

(snip)
Meanwhile, I hope somebody else is on the helm keepng control!!

If your first anchor has a length of chain that is at least 1.5 depth at HW then you will still be anchored while you sort out the connection between the two.

 

[philip_stevens]

In a recent thread someone was advocating using two anchors in tandem.

Is tandem anchoring a sensible idea at all? Or am I better with my former technique of laying the two anchors at about 30 degrees apart and adjusting scope as if the wind swings?

Last summer we got caught in a near gale while at the Isles of Scilly, at Tresco.
As the wind was right on the buoys from the SW, we decided to go over to Green Bay at Bryher, where we could anchor and dry out at low tide - bilge keel.

There were about 10-15 boats there and we dropped anchor to the N of all the others. As we were sheering all over the place, we put out the kedge over the bow, at about 60degrees from the main anchor. It stopped all the sheering, and as the wind shifted, we moved the kedge, at low tide, to compensate for the wind direction.

Quite a few other shallow draft boats, bilge-keel, drop-keel and catamarans, etc, also put out two anchors in V lay-out.

Among the anchored boats were 3 French keel-boats with legs, who put out tandem anchors, to prevent dragging. They did not sheer all over the place, probably being fin keel boats.

This was the first time I had ever put out two anchors (even though we mainly anchor and rarely go into marina's), and will do it again.

 

[Krusty]

In a recent thread someone was advocating using two anchors in tandem. ..............Or am I better with my former technique of laying the two anchors at about 30 degrees apart and adjusting scope as if the wind swings? ...........

FOR WHAT IT'S WORTH:
For forty years we have routinely use two (equal) CQR anchors at about 30* apart ("open hawse") whenever there is a risk of anything over F5, and slept easy. In over 1500 anchorings we had experienced four occasions of dragging after setting; every one traceable to a poor decision of mine.
About four years ago, in Hebrides, the late afternoon forecast for Hebrides was for F9 or F10, possibly F11: we scudded for a favourite small anchorage with good holding and adequate shelter which we could almost guarantee we would have to ourselves.
A short time previously I had read about anchoring "in tandem" with a second anchor a boat-length ahead of the first and shackled to it; (Alaine Gree, I think, a frenchman who seemed to know what he was on about).
We adopted his recommendation on that occasion, and at the height of the blow, (just after the attached pics) we realise we were steadily leaving the bay, stern-first.
Engine on; a lot of power needed to push upwind, and foredeck heroics to get both anchors on board. By then, out of shelter of the bay, we had to use maximum power to regain shelter. We relaid anchors in open hause, as normal, lying to only one with the second in place for the expected veer. The first never budged through the height of the blow, and neither did the second after the veer, when gusts were particularly vicious.

We gave a lot of after-thought to what happened and why. Then I remembered that tandem anchoring was common practice with Fishermans anchors. Perhaps it made sense with that type, but not with anchors designed to bury themselves under increasing load?
We thought through the mechanics of the CQR and realised that anything, whatever, which interfered with the 'diving' action of the anchor, or its chain close to the shank, should be shunned! Taking any notice of A G was my fifth poor anchoring decision!

Photos to Port & Starboard before the fun started:

 

[silver-fox]

Tandem or V anchors?

I realise that the subject of anchor choice and technique raises great passions.

We each have to work out what to do in extreme conditions and I have always had reservations about deploying two anchors in a V for two reasons: -

1. The boat only ever really lies to one anchor at any moment in time so i don't see where the desired improved holding power comes from.

2 Once the smaller of the two anchors drags their is a very high risk of one anchor fouling the other.

Because of this and because of advice from a number of very experienced Kiwi sailors I have swapped notes with on my travels I have opted for the tandem approach in extreme conditions.

That said I have a larger than recommended bower anchor and a kedge that is big enough to be a bower anchor. They are both of the same make and design and both are fitted with mounting points to facilitate tandem anchoring.

I would prevent yawing/sailing at anchor by deploying a riding sail if necessary as I believe this is a very important problem that can cause anchors to drag. (I say if necessary because I have put up a stern arch with solar panels and a wind gen and I suspect the extra windage so far aft may have altered the boats characteristics at anchor but that has yet to be proven in anger.)

The experts seem split on tandem or Vee as effective techniques

The Spade inventor argues passionately against, whereas the Rocna people are more positive. I have provided a link to Rocna's article on the subject and leave everyone to make their own mind up.

One point Rocna made to me when I was doing my research was to buy a big enough anchor to deal with bad weather (in my case I sized based on a force 10) and only deploy a second anchor in extreme conditions.

Multiple anchors

 

[ytd]

Silver Fox is right, once the boat starts veering around, most of the load will be on one anchor or the other and if the holding is good there is no advantage. Better to set a stern anchor to reduce the veering. Only time I have laid 2 anchors was in soft mud. Dropped the main anchor with 60m chain and we were dragging at a good pace. Dinghyed (?) out a second similar sized anchor dropped level with the first with about a 30deg separation in the cables. Adjusted cables so there was equal load on them. Still dragged but much slower. We were waiting for a seaplane to pick up a crew. Once they departed we moved to a better anchorage.

 

[dt4134]

I remember reading of an incident where a sailing school boat with tandem anchors dragged.

There was some discussion of whether, once dragging had started, the seabed was disturbed by the first anchor making the second one ineffective. It seems tandem anchoring was traditional technique that didn't work very well in the past.

I could find any proper details, but I did find this summary on the MAIB website.


http://www.maib.gov.uk/cms_resources.cfm?file=/SD3-06_ Leisure craft.pdf

 

[TerryMac]

FWIW - I have used the tandem method and it didn't budge. We were expecting F8-9 but as it blew through it was more like F6-7 although I did experience gusts of over 40 knots. The wind veered through 120-160 degrees.

I laid out an FX23 Fortress by hand with 12m of 10mm chain shackled to the crown of a 45lb CQR with another 60m of 10mm chain. I lowered the CQR using the windlass and the weight of the anchor and chain set the Fortress. I dove down and checked they were both set.

It was simple to set and retireve probably due to the lightweight of the Fortress. Definitley a technique I will use again.

 

[puddock]

Oil Rigs sometimes use a tandem system (usually Bruce style), then again they usually have an 8 cable spread

 

[lw395]

I suspect much of the gain of tandem anchors is due to the pull on the first one being straight along the seabed. So the second anchor acts partly as a weight.

 

[Quandary]

Thanks for responding
JCP, I think you may have attached the wrong page?
From what I read above, I understand that the first chain should be attached directly to the second anchor?
The shorter length of chain must always be used first.
There seems to be a difference of opinion on whether the biggest/best anchor should go down first?
My conclusion so far
Take the short chain off the smaller anchor and switch it with the best one, put down best anchor on shorter chain, attach end of short chain to second (smaller) anchor, shackle long chain on to second anchor and lay.
Any comments on this interpretation?

 

[Salty John]

My preferred method is two anchors in vee formation, about 40 to 50 degrees apart.

I have tried the tandem arrangement on a few occasions and found that it is troublesome to set up properly and leads to tangled chain in reversing current situations.
Difficult to say if it holds any better than a single anchor but theoretically it should, even if only because one anchor helps to hold down the shank of the other to give a horizontal pull.

But, I prefer to keep things simple so always revert to my relaible vee formation method.

 

[zeds]

. . . . we decided to go over to Green Bay at Bryher, where we could anchor and dry out at low tide - bilge keel.

Quite a few other shallow draft boats, bilge-keel, drop-keel and catamarans, etc, also put out two anchors in V lay-out. . . . .

Same place - maybe same time! The variety of opinions expressed underpin the need to consider individual vessels, ground gear and circumstances. Green Bay is hard sand and dries - not perfect for a CQR! Advice for here (and Scilly generally) is normally, I believe, to carry a kedge with different characteristics to cope with rock, kelp and very firm sand. With the blow forecast I dropped anchor in Green Bay on a dropping tide, waited until dry, re-laid CQR digging it in as well as possible, laid a fisherman kedge at approx 35 degrees which I knew would pull to fluke depth under any tension and lay relatively unmoved for 3 days. Anchors were checked at each low tide - the CQR usually benefitted from some attention - the fisherman, though significantly lighter, would only be moved to balance a wind direction change. I would not, however, adopt this technique anchored out in the Tresco channel or other spot subject to strong tidal movement which would conflict with, and probably often take precedence over, wind/gust direction