Best dual anchor configuration?

[Thalas]

Serious storm is coming and you have no choice but to anchor. Better to lay out two anchors in series with the rode of the smaller anchor attached to the larger anchor or tandem anchors around 30 degrees apart (assuming you have sufficient chain for the second anchor)?

[Don C L]

This topic has come up a time or two. So you do not have have two identical sufficiently sized anchors? How small is the smaller anchor? I still choose the second option. But can I see what is behind door number three too?
I better edit that. If the smaller anchor will likely drag then It is of little use in any case. It will be the larger anchor that will inevitably be taking the load, unless it too starts dragging. In any case, scope! Lots of it.

[Jim Cate]

The best dual anchor configuration is a better single anchor...

Jim

[Pelagic]

I agee with Jim, make sure your primary tackle is up to the task and keep it well serviced.

I do have a back up anchor on the bow in case I had to drop the primary if fouled and dive on it.


I also have a 3rd anchor with about 60ft of heavy chain.

If I was concerned about a slimy bottom for being reliable in a blow, then I would shackle that on to the primary anchor so that its resistance would cause the primary anchor to pivot down into the harder bottom

[thinwater]

The truth is that it depends. A single NG anchor is nearly always the better answer. But there are times when that can be improved upon even farther. I've done a LOT of testing for articles, much of it using load cells, a long with a lot of field testing.

First, the answer depends strongly on the bottom and the anchor types. Change anchor types, and the best way to deploy them changes. Obvious enough.

Second, it depends on the weather. Are you expecting wind from a relatively constant direction, or do you expect a 180 degree shift?

Finally, it depends on the bottom. Rocks, hard sand, and very soft mud have practically nothing in common.

I have a book coming out this winter.

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In-line. Practically everything positive that has been posted was anecdotal and if they actually dove, they would see that only one anchor is holding. Try it on a beach, I bet you cannot get both anchors to set and remain set in even a 10 degree veer. However, it can work well on hardpan, cobbles, and rocks, where anchors are not really setting.

Bahamian moore. Not for increased holding, only for reduced motion. Certainly not helpful if one anchor is smaller.

V-tandem. This can be very good, depending on the anchor types. However, you do NOT simply lay them 30 degrees apart for best results. That will simply allow the weaker to drag when the loads comes onto one anchor, which it will. Mostly, this is only useful in very soft bottoms, where anchors will tend to move a little anyway. https://www.practical-sailor.com/iss...g_12072-1.html

Hammer lock. Really, the only good use for a smaller anchor.

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If you have a second anchor to deploy, it should be even larger, no, or at least higher holding capacity, like a Fortress. If that is the case, perhaps you are thinking about this backwards; how can you use your "main" NG anchor to reinforce the Fortress? Puzzle that out.

[Hasbeen]

I have been through a number of Queensland Oz cyclones with a number of boats.


We had a 120Ft ferry that had to survive cyclones unattended in Shute Harbour in the Whitsunday Islands. We would lay out 2 heavy CQR anchors on 3/4" stud link chain. These were set at 45 degrees either side of the expected South East wind, meeting over the usual mooring.


She survived 3 cyclones this way, with 105 knots the strongest wind experienced. Getting these back up from heavy mud was not easy after the blow. The greatest danger in Shute Harbour was other boats broken free, or dragging moorings.


For normal anchoring it is important to remember you may have to move. It could be a wind change, or a loose boat attacking you, & you don't want the complication of anchors attached to the main chain as you lift the main. If you doubt the holding power of your storm anchor, dice it & get a bigger/better one, it is the cheapest insurance you will ever buy.


I lay to my 45 Lb. CQR in both mangrove creeks, & in open bays, [off shore wind] in 80 knots successfully, & again the hardest problem was getting it up. I had to dive on it once, & dig it out.


Make sure your bow gear is up to it. Many production boats are really only meant for marina mooring. No anchor gear is much use, if your winch comes off.

[barnakiel]

I can't tell which is better.

We used V configuration with two similar anchors - a Bruce and a Danforth. This combo held very well. There was no/little wind shift.

I may be wrong, but it felt as if anchors in V reduced sailing. Being on one rode only (anchors in tandem) will not reduce sailing. But it may be the better choice if you expect a major windshift (direction shift).

Cheers,
b.

[thinwater]

I gotta comment:

Originally Posted by barnakiel

I can't tell which is better.

We used V configuration with two similar anchors - a Bruce and a Danforth. This combo held very well. There was no/little wind shift. [The Bruce and Danforth could not be more different in their stress/dragging performance. Both can be good anchors, but I wouldn't call them similar.]

I may be wrong, but it felt as if anchors in V reduced sailing. [Yes, 100% correct] Being on one rode only (anchors in tandem) will not reduce sailing. But it may be the better choice if you expect a major windshift (direction shift). [In-line tandems are terrible if the wind shifts. They are ONLY used commercially and by the Navy in multi-poin moorings, where the angle cannot change. Try this and you will watch the primary anchor roll over and not reset every time the wind shifts.]

Cheers,
b.

Honestly, I would love to have readers try in-line tandems in fair weather. Wait for the wind to shift, and see if the primary is not on it's side, upside down, or some times even suspended above the bottom by rode tension. It simply does not work. Yes, you can do it an survive a storm, but was it one anchor holding? Probably.

Folks (Rocna) have posted stuff on in-line tandems, but they do not show or talk about even a 10 degree shift. There is a reason. Wemar posted images, and even the company photos show the lead anchor rolling out.

The exception is rock and patchy weeds, where 2 anchors can increase the possibilities.

[barnakiel]

Yes.

Probably a lot depends on what the configuration is (e.g. which anchor goes up first: the small, or the big one, or are they both big anchors, etc.) as well as on the bottom (sand, mud, or rock, or weed). There are many factors.

I think tandem is difficult to lay out too. One may want to have No1 dig in very well and then No2 just as well. But if they are chained, No2 may become next to impossible to set as No 1 will keep the rode tight and the No2 immobile. If No2 is immobile, it cannot dig in.

If we reverse the situation and use a smaller 'pilot' No1, then No2 may dig in, but what is the use of No1 then?

Etc.

I have no doubt tandem may work with good skills and in some situations but it does seem more difficult to deploy well.

b.

[newhaul]

Originally Posted by Thalas

Serious storm is coming and you have no choice but to anchor. Better to lay out two anchors in series with the rode of the smaller anchor attached to the larger anchor or tandem anchors around 30 degrees apart (assuming you have sufficient chain for the second anchor)?

single larger anchor and lots of scope.
Last storm I anchored in 60kt winds 27# danforth 30 ft 3/8 chain and about 150 ft 1/2rode in about 10 ft water. Slept quite well that night. (24ft islanders that trip)

[a64pilot]

I agonized about this for awhile, even started a thread about an “Armageddon” anchoring situation.
Not that I’m saying what I decided was best, but what I settled on was a stupid big oversized New generation anchor, in my case a 40 Kg Rocna on a 38’ Boat.
I did sit out one small Hurricane, that thankfully missed to the East. As you can imagine I did everything I could to get the anchor to set as hard as I could. If you do go with a stupid big anchor, set a trip line to retrieve it on a float if you do have to ride out a big storm, I didn’t need to use my trip line, but it did take about a half hour to retrieve the anchor. Had I really ridden out a major blow, I think I would have had to use the trip line.
Then sort or decided, why not just use it as the primary anchor, cause sometimes unplanned events happen.

However I can see how maybe a stupid big oversized Fortress would also be a go to Armageddon anchor, it also has the advantage of being lightweight and easily disassembled and stowed if you so desire.
However it would not be my go to for a primary anchor.

I’m in the one big, beats two small camp myself.

[anacapaisland42]

Don't forget a kellett
Bill

Originally Posted by Thalas

Serious storm is coming and you have no choice but to anchor. Better to lay out two anchors in series with the rode of the smaller anchor attached to the larger anchor or tandem anchors around 30 degrees apart (assuming you have sufficient chain for the second anchor)?

[kas_1611]

Originally Posted by a64pilot

Not that I’m saying what I decided was best, but what I settled on was a stupid big oversized New generation anchor, in my case a 40 Kg Rocna on a 38’ Boat.

And I thought I was mad with my 33kg Vulcan on my 40ft boat

Originally Posted by a64pilot

I’m in the one big, beats two small camp myself.

Agree with you. Better to have a single bower that can handle everything Mama Nature could throw at you than have to mess around with multiple chains, anchors, shackles, snubbers etc. As I say "Go big or go home!"

[Bill whitmore]

We always put out at least 2 large "primary" anchors assuming we have the space and are not too near other boats that are riding on a single anchor/mooring. We place them so that when the wind and waves are the worst we will have some load on both anchors such that by adjusting lengths we can keep the bow relatively fixed. We have found that avoiding the side to side "tacking that naturally occurs with a single rode, the shock loads on every part of the system, and our personal stress level, is greatly reduced. As the wind almost inevitably changes direction, we are set up to adjust the length of the rodes under load from a relatively protected position, to maintain this status. On some occasions, when a very large windshift was anticipated, we have placed three anchors out, leaving one slack and adjusting lengths so that only two are loaded at any point in time--all with the intent of controlling the lateral movement of the bow and thus keeping quite even tension on the anchor taking most of the load. Of course---all this only functions correctly with someone on board to adjust rode lengths as necessary, and your anchors provide sufficient holding for the loads that occur. The best aspect of this system (other than comfort) is that: if you have anticipated the winds correctly, when in the worst wind and waves, both anchors will be seeing about half of the maximum loads that would occur with just a single anchor, or, conversely, you would be able to survive much worse conditions than expected.

[Souzag818]

Originally Posted by Jim Cate

The best dual anchor configuration is a better single anchor...

Jim

This is the best quote of the whole thread!! And I think the best advice