Best dual anchor configuration?

[IslandHopper]

Originally Posted by thinwater

I should have been more clear. They will tell you it will not work in a shift. A spread means no shift.

Not sure what you mean by a shift, are you talking about a rig shift? if so i have never heard of an rig trying to shift location with a set of piggybacks still connected, recipe for disaster i would think and why it wouldn't work, the vast majority of piggybacks are prelaid by anchor handlers, the rig plays no part. Having said that, it's not unknown for an extra piggyback anchor to be installed later, have done that to, mongrel of a job.

Also, some of the rig anchor companies (Vyrhof) no longer attach the secondary to the tail of the primary, they attach it to the shackle because that is more stable. So the thinking is changing.

Been that way for a long time, the connection from the secondary drapes over the back of the primary and is shackled to the head of the primaries shank

Define "when needed." Too my understanding, it is generally when a larger anchor cannot penetrate deeply do to deep soil conditions.

Exactly, if the primaries can't penetrate enough then a secondary is the usual fix, it's not unheard of for a third to be used used but hopefully i never have the misfortune of doing that.

This is more likely for large anchors than for sailors. Sailors, on the other hand, nearly always need more penetration. So the factors are reversed. That said, on of the situations where in-line tandems can excel is sand over hardpan and similar situations where the anchors cannot deeply set and are struggling for friction. There are times when in-line tandems make sense, but they are rare and the sailor needs to save the in-line rig for those times.

On the bridge here we have Vryhof manuals and many many more, no shortage of cat skinning procedures....

Back to sailboats

[ZULU40]

I think the real question is what would your insurers expect you to have

and if it all goes to s*** how will you convince them that a single anchor no matter how good, was/is the best option

[Fortress]

Originally Posted by captstu

50 years Anchoring experience including diving on the anchors probably 30 times give me some confidence that tandom anchor is the way to go.

Let me share one anecdote that is typical of my experience.

Hurricane Wilma Passed over North Palm Beach with more wind than I felt I can safely endure on board. I anchored my boat, a 43 foot voyage catamaran, with a tandem anchor consisting of a 25 kg Bruce backed by an FX 37 fortress. The heavier anchor was attached to the boat with 100 feet of 5/16 HT chain and 2 bridles. Primary bridal was 5/8 nylon spliced to the boats beam and hook to the chain with a Wichad Chaim hook. The secondary, bridle was attached to two cleats some chafing gear and rolling hitch on the anchor chain.

At the end of the storm both bridals broke at both ends. The rolling yet remain attached to the chain and the chain hook also rebate attached to portions of the primary bridle and the chain. There was no apparent chafe. I believe the lines broke when the the Eye passed over the boat and the beer passed over the boat causing her to run down the shade and lurch to a stop suddenly.

The chain pulled the windless out of It’s mount . The chain had an overhand knot just before the hard point where the bitter end was attached. The bitter end attachment snapped out of builders Hard point, and the chain knot jammed the hawse pipe saving the boat.

I dived the rig before recovering. The primary anchor, the Bruce, showed signs of tripping when the veer hit the Boat. All that was visible of the fortress was the chain where it attached to the Bruce. The chain was about 6 feet long and completely buried.

I was able to recover the Bruce with the windless and some help from a spare halyard. It took several hours of motoring To recover the remains of the fortress. When the veer hit The shank of the fortress bent 180° And the flukes were both destroyed.

Virtually every other boat in a crowd of anchorage was up on the beach.

Other than a broken winless about, two broken bridles, and a chain that it stretched itself in the near uselessness with the overload, my boat took no damage.

While this may be an anecdotal story it is not the only time that I survive moderate to heavy winds on a tandem anchor set While the boats around me using more sophisticated anchoring systems either drifted away or in some cases were rescued when I throw line to them And allowed them to trail off of mine till the wind died down.

Fortress replaced the damage parts for free under warranty and Bruce was not damaged.

Captstu, thanks for sharing your story and glad to hear that there was no damage to your boat after Wilma. As you know, we are south of you in Fort Lauderdale and in addition to extensive boat damage in the area, we were without power for two weeks after that storm which had Category 2 winds of 110 mph (200 km/h).

Worth noting is that your Fortress FX-37 only weighs about 21 lbs (10 kg), and when the wind pipes up, an anchor's deep burying capability is likely to determine whether it remains embedded into a sea bottom or not.

Here's a reprint of noted boating writer Tom Neale's Soundings magazine cover story, "Surviving a Storm at Anchor," with some additional thoughts:

http://fortressanchors.com/SSA.pdf

[thinwater]

Originally Posted by thinwater
I should have been more clear. They will tell you it will not work in a shift. A spread means no shift.

Not sure what you mean by a shift, are you talking about a rig shift? if so i have never heard of an rig trying to shift location with a set of piggybacks still connected, recipe for disaster i would think and why it wouldn't work, the vast majority of piggybacks are prelaid by anchor handlers, the rig plays no part. Having said that, it's not unknown for an extra piggyback anchor to be installed later, have done that to, mongrel of a job.

Also, some of the rig anchor companies (Vyrhof) no longer attach the secondary to the tail of the primary, they attach it to the shackle because that is more stable. So the thinking is changing.

Been that way for a long time, the connection from the secondary drapes over the back of the primary and is shackled to the head of the primaries shank

Define "when needed." Too my understanding, it is generally when a larger anchor cannot penetrate deeply do to deep soil conditions.

Exactly, if the primaries can't penetrate enough then a secondary is the usual fix, it's not unheard of for a third to be used used but hopefully i never have the misfortune of doing that.

This is more likely for large anchors than for sailors. Sailors, on the other hand, nearly always need more penetration. So the factors are reversed. That said, on of the situations where in-line tandems can excel is sand over hardpan and similar situations where the anchors cannot deeply set and are struggling for friction. There are times when in-line tandems make sense, but they are rare and the sailor needs to save the in-line rig for those times.
On the bridge here we have Vryhof manuals and many many more, no shortage of cat skinning procedures....

Back to sailboats

By shift I meant a shift in the wind direction, leading to a shift in the direction of pull. To my knowledge, this is not something rig anchor experience.

Yes, draping over the back is what I meant by the new thinking (for a long time). The problems is, when most people think of in-line tandems they mean a second anchor attached somewhere at the back of the main anchor. This was recently popularized by Rocna, and that is what I consider and atrociously bad idea. He posted a bunch of pictures, but they are also faked in the sense that the anchor are not in fact well set, in some if you look closely you can see the anchors lifting out, and he never shows a direction change. Thus, the pictures give a complelelty false impression.

An as you said, this is for when the anchors cannot penetrate deeply. The corollary for sailors is that in-line tandems are ONLY for sand over hardpan, cobles, and rocks. Otherwise, a single large anchor is the better answer.

[captstu]

Happy to see we have diverged from facts and moved to opinion. Sort of the religion of anchoring.

I have no problem if you feel some other anchoring mechanism but tandem is better - use whatever you feel is appropriate for your situation.

But, as I said above, I was one of only three boats in a 100 boat anchorage to survive Wilma - the other two being commercial boats 4 times or more my size. Most went up on the beach.

A tandem anchor setup has served me well for four boats, fifty years, and about 10 storms. I dive the rig after the storm goes by - the primary anchor, a 50 kg bruce, has always tripped while the fortress dug in and held - sometimes bending in the process.

Static testing, load testing, and imagination are not as good as real life experience. I'll stick with a tandem, you use a heavier anchor, a bigger windless, and more weight on your bow every time you anchor for lunch.

It is, after all, your boat.

[NevisDog]

Originally Posted by captstu

...A tandem anchor setup has served me well for four boats, fifty years, and about 10 storms. I dive the rig after the storm goes by - the primary anchor, a 50 kg bruce, has always tripped while the fortress dug in and held - sometimes bending in the process...

There is tandem anchoring, and then there's tandem anchoring. I believe your set-up is more akin to a large Fortress supported by a heavy weight 6' in front of it. Okay the heavy weight you have is a 50kg Bruce, but the Bruce "always trips", so it's not actually supplying any extra anchoring, it's just keeping the chain flat on the bottom. You already said the Bruce acts as a weight but it's not worth swapping it out as it does no harm as a weight - or words to that effect, if I understood correctly. So there is not a great deal of difference between you two 'experts' - you both agree that the forward anchor (oops! I mean the one closer to the boat) trips, which seems the main point to emphasise with this set-up, soon as wind direction shifts. The Bruce clearly pulls out in the wind shift, then drags back at least 12 ft without digging in, otherwise the Fortress would not end up bent through 180 degrees.

The Rocna anchor website is of some concern here, as its advice seems to contradict both your experience (the forward Bruce tripping out in a windshift) and Thinwater's would seem to indicate its advice is at best questionable (for anything other than a multi-directional moor - such as an oil rig).

I hope I've understood the argument so far.

[james247]

Originally Posted by Jim Cate

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

Jim

I have never dragged anchor since I made two changes. Went up in size. On size bigger anchor than recommended and one size heavier in chain. Still have second anchor. Might surprise some folk but things do go wrong on boats [emoji12]

[Naughty Cat]

For any Brits in this thread there is an excellent article in Sailing Today this month comparing the effects of a snubbing bridle -v- heavier chain in winds above 30knots. I will.post a link if I can find one. Whilst not the question posed by the OP it has persuaded me to get a longer line that I can snub off cleats further towards the stern giving me more elasticity and greatly improving holding power. I would rather do than double anchor as a first resort.

[Hasbeen]

I used to do quite a bit of Great Barrier Reef charter trips, usually from 2 to 6 days duration. Some were fishing, & some were dive trips, which dictated which part of the reef we went to. These were usually on a 45Ft fishing boat, or a 56Ft dive boat.


Overnight anchorages were all "underwater lagoons", with no drying area, with the coral from 4 to 16 Ft under water depending on tide level. It is surprising to many how much a reef even 16Ft deep will calm the sea.


These anchorages were 45 to 60 miles out, with no visible reference, & usually 60 to 80 Ft deep. The bottom was usually a mixture of coral & coral sand, with many up to bus sixed lumps of coral washed into the lagoons during cyclones.


It could be quite unnerving on rougher nights to hear the chain rumbling over the coral, as the boat sailed around the end of usually 300 Ft or so. The question of were you dragging was constant.


My use for a second anchor was not to reinforce the main anchor, but to anchor a buoy, or jerry can around the spot my anchor was placed, so I could check it regularly to reassure myself the boat was not dragging. Dragging out there at night at low tide is usually disastrous.


I never used a duel anchor system, & never had the misfortune of dragging, although I did not enjoy the occasion when my sighting buoy anchor did drag, giving me a rather restless night.


I also did some yacht charters. A reasonably deep drafted yacht could be a real pain out there. A south east going flood tide, running against the south east trades could hold the yacht stern into the chop, would give a very uncomfortable 2 or 3 hours approaching high tide.

[Jolly Roger]

In their Jan/Feb 2016 edition Good Old Boat magazine published an article by me about a tandem anchoring method I always use when anchoring overnight, irrespective of the forecast.
It can now be found on my boat website at www. A drag proof method of anchoring.
It’s just another method, but one which I have perfected to the extent that I can deploy both anchors as quick as any single. It has never failed on many boats where I have used it, including a 35 ton 77 foot ketch in a hurricane.

[Navicula]

man I just read your system......its now in my head...thankyou

[NevisDog]

Originally Posted by Jolly Roger

In their Jan/Feb 2016 edition Good Old Boat magazine published an article by me about a tandem anchoring method I always use when anchoring overnight...

At first read, this method seems beyond genius!

Two comments (could be wrong):
1. You still use CQRs. I wonder if the 3rd generation anchors make this genius anchor set-up unnecessary, at least until that mistral/hurricane is forecast?
2. I wonder if we should avoid the term 'tandem anchoring' with this method, or is this the correct meaning of this term? (I've only seen 'tandem' referring to two anchors shackled close to each other, like a tandem bicycle - the two virtually joined together and pulling in identical direction.)

[Jolly Roger]

I don’t use the term “tandem” in the article, and it can be called whatever you like. It’s the working principal what matters.
I use the CQR’s which were on the boat when I bought it and which fit neatly on my twin bow rollers. I can't see why any of the new style anchors could not be employed in the same manner. It’s just a matter of what you’ve got and what you are familiar with. JR

[anacapaisland42]

Very interesting article//thank you.
You mention kellets and I would like to follow up on that.
Pretty well all the criticism I've seen/read on kellets show the example of them/it suspended way off the ocean floor in what one presumes is "a howling gale" to show the chain so taught.
HOWEVER.....I have a "feeling" that the kellets main benefit is way before that, happening in the period of gradually increasing winds or, indeed, of setting the anchor with the engine.
MY hypothesis is that in this period the kellet encourages the anchor to drag horizontally for a further distance than solely using chain thus facilitating a better/deeper set. ???

Bill

Originally Posted by Jolly Roger

In their Jan/Feb 2016 edition Good Old Boat magazine published an article by me about a tandem anchoring method I always use when anchoring overnight, irrespective of the forecast.
It can now be found on my boat website at www. A drag proof method of anchoring.
It’s just another method, but one which I have perfected to the extent that I can deploy both anchors as quick as any single. It has never failed on many boats where I have used it, including a 35 ton 77 foot ketch in a hurricane.

[captstu]

Hard to picture what a Kellet might do that a tandem anchor won't accomplish better. In the tandem setup I use, the plough-type anchor acts temporarily as a Kellet during the first part of the process when the Fortress is first setting and the boat is backing slowly, deploying chain. The plough (Bruce or your favorite) keeps the Fortress on the bottom and helps it anchor.

During a severe storm, the chain is taught so the extra weight doesn't do much.