Tandem Anchoring

[Steadman Uhlich]

I am no anchor expert. But I recently came across some views from two anchor experts, the designers of the Rocna and the Spade anchors. The views expressed below are theirs. I have no connection to any anchor manufacturer and no vested interest. I am merely sharing the views of two highly regarded experts.

You may disagree. You may feel your own anchors or your methods or traditional anchors or traditional methods are best. Anchors and methods of using them are a hotly contested topic. So I fully expect that there are many opinions on the subject.

I don't claim to have anywhere near the experience of some members here, whose experienced views I do value. So, I am not offering my opinion on what is the best anchor or method.

But anchors are a debatable subject, often with opinions that are formed by imperfect observations in uncontrolled testing or simply anecdotes passed on, when the anchorage conditions may be highly variable. I am no anchor expert, but here are the words of two real ones you might want to consider:

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Alain Poiraud (Spade Anchors)

Alain Poiraud, French designer of the Spade anchor, dislikes the concept of tandem anchoring and relates his experiences as follows:

“Attaching two anchors to one rode, known as tandem anchoring, should be avoided.

“The double approach attaches a second anchor with around 15′ of chain in front of the first anchor. I personally almost lost my boat trying out this idea. At the time, my first anchor dragged. Needless to say, it was an old generation model, so I decided to try something new. I added a smaller anchor in front of the large one. This worsened the holding power as opposed to doubling it, drifting swiftly on the smaller anchor while the larger one couldn’t grip at all.

“When an anchor has dragged, a trench formed behind it and this quickly backfilled with loose un-compacted sand. These areas can be still visible after several tides and may explain why some popular anchorages are criss-crossed with patches of poor holding. Then, if the most proximal anchor set, they are very good chances that the [far] anchor will fall down in this loose bottom, with, as a consequence, a poor holding!

“I have done a series of approximately 70 tandem anchorages in the clear waters of the Med, diving on nearly all of them. In 62% of the cases, only one anchor was set. During bad weather, you will not have the possibility to dive to check your anchors, and you only have to ‘trust’ your anchors, which is what I call ‘the Russian Roulette’ anchoring.

“At first, I tried to attach the smallest flat anchor (a 16 kg Brittany) with 5 meters of chain to the hole at the back of the shank of the CQR (20 kg), and I noticed that it will more or less change the equilibrium of the CQR."

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Peter Smith (Rocna)

Using multiple anchors on boats is fairly common, and various well recognized arrangements exist for handling particular situations. For example, a bow-and-stern arrangement may be used to hold a boat into a swell in order to minimize rolling, or a Bahamian Y moor may be used to deal with frequent 180 degree veers such as when anchored in a tidal area.

“Most boaters should never have cause for tandem anchoring. Your primary anchor should be sized so that it is adequate on its own in practically all conditions – if it is not, then upgrade. [The tandem anchoring] functionality is provided for those more ‘extreme’ adventurers who require it.”

A tandem anchor set-up is intended to simply maximize holding power. It does not deal with complex situations for which another rig may be more appropriate, and works best at dealing with strong winds from a single direction.

There is one point that should be strongly emphasized, and that is the fact that any multiple anchor rig introduces a complexity to an anchoring set-up that is undesirable. Your primary anchor should be sized to be good enough on its own for most all situations – if it is not, reconsider your choice of that anchor. Tandem anchoring is for extreme situations, in which a single anchor large enough alone would not be practical for daily use.

Let’s pause to reiterate this. It is a mistake to think to tandem anchor regularly. You must have a primary anchor of a good size and type for your boat. If not, get one.

Never attach the rode of the tandem anchor to the front of the primary anchor…
…Unless the primary anchor is designed for it, i.e. has a dedicated attachment point intended for a tandem anchor.

Most anchors have a hole near their crown. However, this is not an attachment point for a tandem rode! It is for a trip line. Never use it for the tandem anchor, as it will unbalance the primary anchor when load is applied. It is also frequently not strong enough, intended only to take the weight of the anchor itself.

Anchors which cannot have tandems attached directly to them include the CQR, Bruce, Delta, Spade, and Danforth types.

Never use an anchor unreliable at setting as the tandem

In addition to using identical types, one should never use a type which is known to be unreliable at setting per se. It is no good dragging your primary plow for 10 meters before getting a set, and hoping that the plow tandem will perform similarly. The reality is it may drag 100 meters before setting, and that may be too far.

Most older “traditional” types are not terribly reliable at setting. Articulated plows such as the original CQR can require multiple attempts to get them to bury. Fixed shank plows such as the Delta are better.
Claws like the original Bruce are better than the plow, but not necessarily in hard sand, where they can lie on their back and fail to right themselves.

Danforth types including the Fortress are shocking and are absolutely to be avoided. They are not general purpose anchors, and have no place in a tandem rig.

New generation anchors which have been demonstrated to set reliably are the best bets. These include the Spade, Bulwagga, and Rocna. Having said that, many new anchors promise everything yet deliver little, so check carefully for credible test results and other users’ experiences."

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Bahamian Moor?

Peter Smith (Rocna):

"A modified Bahamian moor, where two anchors are deployed from the boat in the form of a V or Y shape and the boat can hang on both simultaneously, is often considered an alternative to a tandem rig. It has some advantage in that it can help reduce swinging or “sailing” at anchor as the two anchors both exert some lateral restraint on the boat.

Dual anchors in a V arrangement
Modified Bahamian moor
However, in the interest of maximizing holding power, it offers a false security. It is almost impossible to get the load on the boat distributed equally on both anchors, even while the wind is in the exact direction for which the anchors were set. Rather, the stress can oscillate from one anchor to the other, and if the stresses are enough to justify the use of dual anchors in the first place (otherwise why bother with the second at all?), the two anchors may simply be “walked” downwind.

This set-up is also completely incapable of dealing with veers in the wind direction. If it survives such a veer at all, the two anchors will be out of rank, and the now windward one will have to drag back into line with its opposite number. At this point, the two anchors will be closer together than before, and such a process continued could see the two anchors meet and foul each other.

A further disadvantage is the requirement to use two identical anchors, or else accept a total reduction of the capacity of the rig to the lowest common denominator. For example, if one sets a Bahamian moor with a 20 kg anchor and a 30 kg anchor of the same type, the maximum capacity of the rig is defined by the point at which the 20 kg will drag, whereupon the entire system fails and the extra size of the 30 kg anchor is wasted."

[Don C L]

Yeah I have never tried tandem, never considered it. But what they are calling "Bahamian" is really "modified Bahamian," the V set-up. I personally have not considered that one either. But anchoring bow and stern and then bringing the stern anchor rode forward to the bow if needed to allow the boat to swing (true Bahamian) has served me well and works in the widest variety of scenarios IMO. It is more of a hassle, and there is the chance the boat will rotate around and twist the rodes together... but we all consider what is "worth it" for ourselves. Where I am we are all almost always anchored bow and stern so these issues don't come up much I confess.

[JPA Cate]

We do not tandem anchor.

We have some friends who did so, in the Clarence River in New South Wales Australia, with a Fortress first, and something else behind, maybe a Bruce, but I'm not sure. In any event, the Fortress held them. It was a b---h to recover. He talked about that for a long time.

I've known folks who were set up to tandem anchor, but ime, it is pretty rare.

Ann

[El Pinguino]

I've read about tandem anchoring, and I've thought about tandem anchoring but I have never tandem anchored.

Honestly don't see the point..... no matter what you do only one anchor will be working at any given time.

I once combined a Bahamian Moor with a Mediterranean Moor ...

Open ( by my standards )... wind came away on the beam... rowed out a kedge very broad on the starboard bow to hold her 'in line' .

[Kenomac]

Steady,

When you eventually get out and spend any time at anchor, you'll learn very quickly what an annoying ass anyone who does this tandem procedure is in an otherwise tranquil anchorage. The practice messes things up for everybody.

Maybe during a hurricane it's OK to try, otherwise it creates a mess in the anchorage because other boats are unable to anticipate the swing of he culprit.

[Snowpetrel]

I have tandem anchored a fair few times. Mostly I dragged when I tandem anchored. Usually because either the bottom was poor, or the wind was strong, or more commonly it was a combination of both, hence the tandem anchor, but I do think two anchors in tandem has much less holding than two in a V on separate rodes. And often its really no more holding than one anchor, since it's hard to get both to work together.

So I much prefer to use two anchors in a V if I feel I need extra security. Though tandem anchors has some handling benefits and some downsides, that makes it sometimes useful, especially if the bottom is so bad that you are just deadweight anchoring. Or you really want to switch anchors and don't want to remove the primary.

The V is great when the wind blows hard from a reasonably steady direction as long as both anchors are properly sized to more or less manage on their own. Done right it seems to significantly reduce yawing and if one anchor let's go the second can give you time to react and will most likely stop you dragging and give the first anchor a chance to grab. I always like to have the second anchor on mostly rope so it is easy to untangle if they get crossed. I also like to have different length scopes so they won't foul each other if they drag and end up in line.

Another technique I have used is to drop the second anchor on short scope under the bow. It is supposed to drag, but the resistance reduces yawing, and if you drag into shallow water it might well bite. It's quick and easy to drop at 1.5:1 scope or so. If it really comes on to blow you can add scope to both anchors and lie to a both in line, not quite as good as a V but still helpful.

Overall though I think the concept of sizing the main anchor to manage ok on its own 99% of the time is a good approach. Even then being neurotic I'll still often use two anchors in strong winds or if I leave the boat for a while for extra peace of mind.

[boatman61]

IMHO Tandem anchoring is an accident waiting to happen.. looks grand to the newbie.. 2 hooks Must be stronger than one..
However the problem is not the swinging.. you'll swing as normal on the first hook at the end of your chain.. the problem comes when one has to up hooks in a hurry..
Basically after getting the first hook on the roller one is left with 5m plus the hook dangling of the bow while wind and/or tide scoot you off out of control.
Now this is no biggie if well crewed and someone to steer under motor.. however solo or with 'passengers' one can get into all sorts of trouble.
Tried it once in Poole harbour behind Brownsea Castle where there's a strong tide run.. it joined my Danforth experience.. Never Again.
Watched one old Frenchman clear the anchorage at Olhau docks one day.. he had 2 undersized anchors in tandem (double anchor logic ) and was trying to anchor in strong wind and modest holding.. there were 8 of us on the hook and one after the other he dragged onto the boats.. maximum effort.. zero success.

[Snowpetrel]

Originally Posted by boatman61

IMHO Tandem anchoring is an accident waiting to happen.. looks grand to the newbie.. 2 hooks Must be stronger than one..
However the problem is not the swinging.. you'll swing as normal on the first hook at the end of your chain.. the problem comes when one has to up hooks in a hurry..
Basically after getting the first hook on the roller one is left with 5m plus the hook dangling of the bow while wind and/or tide scoot you off out of control

Yep, the tandem anchor thing can be awkward to handle if you haven't thought it through pretty carefully before you drop, especially on bigger boats. Just in case anyone has a perverse desire to try it here is what has worked for me in the past.

The best way I have found to set them up is with a floating line from the shackle on the second anchor (end anchor) that runs back and and is tied to the chain before the first anchor with a rolling hitch. Then when you get to the knot you can untie it and use the line to winch the second anchor up to the other roller. It can be done pretty quickly, but it's not ideal if you are on your own.

But in all honesty I think the whole tandem anchor thing doesn't work in almost all cases.

[admiralslater]

Great articles in the last two Practical Sailor mags on this subject . mixed reviews at best

[thinwater]

Originally Posted by boatman61

... the problem comes when one has to up hooks in a hurry..
Basically after getting the first hook on the roller one is left with 5m plus the hook dangling of the bow while wind and/or tide scoot you off out of control.

Very easy, actually. You ALWAYS rig a recovery line, which is different from a tripping line. It is floating line, is just a little longer than the space between the 2 anchors (only floats a few feet off the bottom), and is attached to the anchor shackle on the farthest anchor, and a few feet above the shackle on the near anchor.

Recover the near anchor as usual. Detach the recovery line from the rode, clip an extension to it, and lead the recovery line to where ever the other anchor is going and haul. Then either disconnect the rode between them or just tie it up. Easy. If recovering the second takes more than a few minutes you are doing it wrong.

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That said, there are very few bottoms where a tandem helps (rocks and cobbles). Everywhere else it is worse.

I think the biggest problem with the method is that very few people practice it enough to understand it. They either try it on sand/mud (wrong method) or try it only in bad conditions, and it fails predictably.

[thinwater]

Originally Posted by admiralslater

Great articles in the last two Practical Sailor mags on this subject . mixed reviews at best

Actually, there is final article coming on tandems on rocks and cobbles (the last was more about V-tandems). The overall conclusions:

1. A single anchor is best 98% of the time for all of the reasons folks have stated.
2. An in-line tandem is never the right answer on sand or mud.
3. If you need 2 anchors for soft mud or coarse sand/shells, they are most effective if they are set in an asymmetric V, with the stronger farther way holding (like the anchor guy in tug of war) and the nearer is buffering the shifts and sometimes dragging. This is well suited to the common Fortress/scoop combination folks carry.
4. In-line tandems are very effective on certain rocky/cobble bottoms where digging and burying are not possible.

[boatman61]

[QUOTE=thinwater;2202750]Very easy, actually. You ALWAYS rig a recovery line, which is different from a tripping line. It is floating line, is just a little longer than the space between the 2 anchors (only floats a few feet off the bottom), and is attached to the anchor shackle on the farthest anchor, and a few feet above the shackle on the near anchor.

Recover the near anchor as usual. Detach the recovery line from the rode, clip an extension to it, and lead the recovery line to where ever the other anchor is going and haul. Then either disconnect the rode between them or just tie it up. Easy. If recovering the second takes more than a few minutes you are doing it wrong.
QUOTE]

A few minutes is a very long time if you've a spring tide running at 3+kts and a rising wind.. fantastic if you've lots of room but otherwise..
The pick up line is common sense.. however as I said..

[Stumble]

I would rather melt them both down and have one large anchor than two smaller ones. in any case where tandem anchoring might work out, have a single anchor the combined size of the two will be better.

[Hudson Force]

I've never found a need or desire to put two anchors on one rode. I almost always select a single anchor with ample rode. The times that I've used a Bahamian moor are usually dictated by my neighbors being on Bahamian moors and I do't want to be the odd man with the bigger swing.

[thinwater]

Originally Posted by Stumble

I would rather melt them both down and have one large anchor than two smaller ones. in any case where tandem anchoring might work out, have a single anchor the combined size of the two will be better.

Maybe. Mostly. But...

a. A 2x anchor, assuming the primary is conservativly-sized, is a monster. I don't want to have to work a 100-pound monster into the rollers every day. If the primary is tiny, then you are right!

b. Cobbles. The limiting factor is often when the rock rolls, not the size of the anchor. Two hooks means 2 cobbles may be hooked, and if you do start to drag, the second hook will probably catch before the boat gains momentum. I've played with using 2 very small anchors ( 2 x 2-pounds) and found them as secure as a single 35-pound anchor on some bottoms with small rocks and breakable rocks.

This subject deserves more study.

But for sand and mud, in-line tandems have no place. I agree. I've tested it too many times (load cells, beaches, mud, sand, many sizes, many attachment points) to believe it. But yet it keeps showing up in mags and text books. It looks like it might help, but don't believe us; try it (dive on the anchors and look) and see.

Only rocks.