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Thalas 27-10-2017 16:39

Best dual anchor configuration?
 
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 27-10-2017 17:40

Re: Best dual anchor configuration?
 
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 27-10-2017 18:20

Re: Best dual anchor configuration?
 
The best dual anchor configuration is a better single anchor...

Jim

Pelagic 27-10-2017 18:43

Re: Best dual anchor configuration?
 
1 Attachment(s)
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.
Attachment 158414

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 27-10-2017 19:13

Re: Best dual anchor configuration?
 
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.

----

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.

----

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 28-10-2017 02:57

Re: Best dual anchor configuration?
 
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 28-10-2017 07:08

Re: Best dual anchor configuration?
 
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 28-10-2017 07:30

Re: Best dual anchor configuration?
 
I gotta comment:

Quote:

Originally Posted by barnakiel (Post 2507803)
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 28-10-2017 07:51

Re: Best dual anchor configuration?
 
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 28-10-2017 08:05

Re: Best dual anchor configuration?
 
Quote:

Originally Posted by Thalas (Post 2507485)
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 28-10-2017 08:10

Best dual anchor configuration?
 
I agonized about this for awhile, even started a thread about an ďArmageddonĒ anchoring situation.
Not that Iím 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 38í 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 didnít 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.

Iím in the one big, beats two small camp myself.

anacapaisland42 28-10-2017 08:48

Re: Best dual anchor configuration?
 
Don't forget a kellett
Bill

Quote:

Originally Posted by Thalas (Post 2507485)
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 28-10-2017 08:53

Re: Best dual anchor configuration?
 
Quote:

Originally Posted by a64pilot (Post 2507829)
Not that Iím 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 38í Boat.

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


Quote:

Originally Posted by a64pilot (Post 2507829)
Iím 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 28-10-2017 09:42

Re: Best dual anchor configuration?
 
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 28-10-2017 09:48

Re: Best dual anchor configuration?
 
Quote:

Originally Posted by Jim Cate (Post 2507561)
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:thumb::thumb:

Don C L 28-10-2017 09:49

Re: Best dual anchor configuration?
 
Yeah I really think once you have an adequate anchor, rode that won't chafe through (don't forget that one) and plenty of scope (10:1 or more) it is time to look at the fittings on the boat and see if they are really up to the task of holding the displacement of the boat if it is lurching, and being thrown back and really yanking on the rode. The cleat or post, of course need to be bomb proof, but I used to sail a boat that had the bow roller halfway out on the sprit. I never trusted that. Fortunately it had a beefy snubber that went to a good fitting at the waterline at the bow (which is also a good idea not mentioned yet.)

noelex 77 28-10-2017 11:04

Re: Best dual anchor configuration?
 
Quote:

Originally Posted by Jim Cate (Post 2507561)
The best dual anchor configuration is a better single anchor...

:) :).

It is hard to add a second anchor and increase the holding significantly over the better single anchor.

In a "V" configuration, as the boat sheers in the gusts the load will be applied to one anchor without much load sharing. As the boat swings the load will come on the other anchor and the boat "walks" backward dragging each anchor in turn until they let go completely. In a tandem arrangement there also tends to be little load sharing. Often one anchor is totally unset.

The drawbacks of two anchors are considerable. The extra weight of two anchors and two rodes is significant, much more than a slightly heavier single anchor. In a V configuration you will swing differently to other boats, there is a risk of the rodes becoming tangled. Most critically if you do drag, recovering two rodes especially two tangled rodes (and in all probability they will be tangled) can be difficult. If you ditch the lot you are down to using your third anchor.

There are some advantages:
When at anchor and very bad weather is forecast most people feel compelled to do something. Setting a second anchor feels very constructive and is perhaps better than simply worrying about the weather. There are other things that be done but they just dont have have the feel good factor of deploying a second anchor. It is easy to pretend that your holding power is now double, although most realise this is a fallacy.

On a more practical note, two anchors do reduce sheering. There are other ways to reduce sheering and these may be more effective and easier. On most boats the effect of two anchors is not great, but some boats report more significant benefits so it is worth some experimentation.

So I am not a great fan of two anchors designed to be used in heavy weather, although there are plenty of other practical uses to two anchors such as to point the bow into the swell, or to reduce the swinging area.

Having said the above, if facing something like a named storm, especially if leaving the boat, you may as well put out all the anchors you have.

NevisDog 28-10-2017 12:01

Re: Best dual anchor configuration?
 
Quote:

Originally Posted by thinwater (Post 2507583)
The truth is that it depends.
...
...I have a book coming out this winter.
----
Hammer lock. Really, the only good use for a smaller anchor.
...

Sounds like this guy really knows his stuff, so I went searching for 'hammerlock anchoring,' which led me to "anchoring 201" at captfklanier.com. Now I thought I knew a little bit about this subject but I sure never heard of "drudging" before (which is exactly what Thinwater was rather cryptically referring to above).

So, if you don't have that 40kg beast and only have a large and small anchor to keep you safe through that unexpected storm, I suggest you read up on 'drudging' and the like, or better still, Thinwater may tell us the name of his forthcoming book?

Personally, I find the greatest shock-loads are imposed by the vessel 'sailing' about under a single anchor, so, though a second anchor may not provide much extra holding power, it can greatly reduce the loads as the boat comes up hard on one tack and swings back on the other.

Navicula 28-10-2017 12:15

Re: Best dual anchor configuration?
 
having 2 anchors is great......if one get fouled like a previous post suggested, you can drop that one and re hook somewhere safe and come dive on it later....

I recived a great tip in the bahamas .....have a method to let the chain go at the bitter end....most, like mine are shackled to the boat and the shackle wired up so it does not come undone.....replace the shackle with a strap or rope to the bitter end so if its blowing and your dragging and tangled up with others you will be able to cut the strap with a knife with easy and set yourself free

NevisDog 28-10-2017 12:22

Re: Best dual anchor configuration?
 
Quote:

Originally Posted by Navicula (Post 2508000)
.....have a method to let the chain go at the bitter end....most, like mine are shackled to the boat ...

Never, ever, shackle the bitter end to the boat!!! (Anchoring 101).

Don C L 28-10-2017 12:29

Re: Best dual anchor configuration?
 
I hadn't heard of hammer lock either, had to look it up. I'm not sure drudging and hammer lock are strictly speaking the same thing though they do share dragging an anchor on purpose. Hammer lock involves dropping a second, smaller hook from the bow on a short scope, I see, to dampen the sailing at anchor, once the 2:1 slack is taken up on each tack. I gather you'd want to set the smaller hook a bit aft of the bow to minimize chance of fouling the main rode on the unset smaller anchor when the weather is calm.

Don C L 28-10-2017 12:42

Re: Best dual anchor configuration?
 
Quote:

Originally Posted by Navicula (Post 2508000)
having 2 anchors is great......if one get fouled like a previous post suggested, you can drop that one and re hook somewhere safe and come dive on it later....

I recived a great tip in the bahamas .....have a method to let the chain go at the bitter end....most, like mine are shackled to the boat and the shackle wired up so it does not come undone.....replace the shackle with a strap or rope to the bitter end so if its blowing and your dragging and tangled up with others you will be able to cut the strap with a knife with easy and set yourself free

and if you have all chain keep a length of line 50 or 60' or so with a buoy and carabiner on it to quickly clip on to that bitter end if you ever want to retrieve it again without diving. If you have nylon rode, just keep a buoy handy. Had to do that a couple times. Or keep a grappling hook on board for it. Buoy is much easier.

captstu 28-10-2017 13:08

Re: Best dual anchor configuration?
 
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 180į 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.

NevisDog 28-10-2017 14:20

Re: Best dual anchor configuration?
 
Quote:

Originally Posted by captstu (Post 2508033)
...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.
... It took several hours of motoring To recover the remains of the fortress. When the veer hit The shank of the fortress bent 180į And the flukes were both destroyed. ...

This is an absolutely fascinating story, one that deserves most careful evaluation (which I'm sure Capt Stu has already done) and I hope I can be forgiven for attempting to analyse it further to see what I can learn from this once-in-a-lifetime experience (well, for me, once would be more than enough!).

I've picked only those sections that I find most concerning, though the entire story deserves reading again.

1. "All that was visible of the Fortress was the chain where it attached to the Bruce" and "the Bruce showed signs of tripping": This suggests to me that, had this been a single anchor moor (the Fortress alone, without the Bruce) then it would most likely have buried deeper than the six feet of chain it was allowed from the Bruce. It suggests to me that having the Bruce in tandem actually hindered the Fortress's well-known ability to keep on burying until it can never be recovered.

2. "The Fortress shank bent 180 degrees and the flukes were both destroyed": seems to me the only thing that saved the boat was the Fortress being buried deep enough so that in its mangled state it still had enough holding due to the depth of bury of this mangled lump of twisted metal. But I again suggest the Bruce in tandem actually restricted its ability to bury.

I would conclude that the big Fortress alone would have been more effective than the tandem set-up. I'd also speculate that a bahamian-type moor might have prevented the damage inflicted on the Fortress; it seems fortunate indeed that such damage didn't result in it letting go or snapping off, leaving the Bruce to drag along just below the surface (as it is well known to do).

But this is all just idle speculation on my part - I wasn't there to witness any of this. I take it that Capt Stu reached entirely different conclusions, as it seems he still favours tandem anchoring, and I'd love to hear his reasoning.

thinwater 28-10-2017 15:06

Re: Best dual anchor configuration?
 
Quote:

Originally Posted by barnakiel (Post 2507821)
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.


Try it. Then dive on the anchors. Then tell us what you see after a shift.

I've tried it, lots. Every anchor manufacture, including oil rig anchor manufactures, will tell you it does not and cannot work.

Try it.

TheThunderbird 28-10-2017 17:38

Re: Best dual anchor configuration?
 
If you believe that you should deploy two anchors, first add 20# to your primary anchor.

A second anchor can be used as a kellet hanging on the rode and softening jerks..

'Course, in a shitless situation a Tandem anchoring can give you some psychological Peace of Mind

V-setting will never work with 2 anchors at once, and IF they do, one is unnecessary.

Sheering and sailing on anchor is stressing both me and her.... I find a brilliant solution, by means of taking the snubber out, over one side, at the bow or even more aft, thus allowing for some righting force.

The side to choose depends on boat and on local circumstances

They used to have heavy and cheap storm anchors. We may agree that on a leisure vessel it is impractical or dangerous. The second anchor must be a spare, and an alternative for different grounds

captstu 28-10-2017 18:48

Re: Best dual anchor configuration?
 
Some comments on the comments if I babe.

I tried various lengths of chain between the primary Bruce at the secondary fortress. I settlrd around 6 feet because it was easy to recover and easy to lay out.

When I know Iím going to deploy two anchors, I go forward as I enter the Anchorage at low speed and throw the fortress over the bow. It hangs below the deck above the bottom and does nothing until I bring the boat to a stop. At this point Iíd apply enough chain with the wetlands so that the fortress hits bottom as I begin to drift backwards. Once I feel the fortress it I slowly deploy chain in the usual manner until the last of shade I decided has been deployed.

At that point I wait until the boat Works is to stop.

I go forward the second time attach the primary bridal and played a short chain until the bridal is taught in there is significant slack in the chain between the bridal in the Bow roller.

I believe but cannot verify that the Bruce is acting as a way to keep the Fortress shank parallel to the bottom.

I donít actually bother to back what the set up because it is never ever felt the hold.

If I use more than 6 feet of chain fortress would hit the bottom before I was ready.

Recovery is Perform in reverse. I go forward release the bridal and motor forward to trip the Bruce. Once the Bruce is tripped I can recover it one to the power roller tripping the fortress of the process. Itís a fortress does not trip, I cannot completely recover the Bruce and bus go forward reattach the bridal at power forward until the unit trips. This is happened a few times

I have no problem with the idea that the fortress became a sacrificial anchored in a hurricane Wilma. My chain became sacrificial as well as that both of my bridals.

If I were to use just a fortress I donít think the weight of the fortress and Chain would be sufficient to stop for Fortress from flying rather grabbing.

I thought about adding weight to the chain to make the Fortres operate alone, But it made no sense since on some bottoms I have to use the fortress in the Bruce operates as a weigh only. It makes no sense to change over rather use both.

I understand that under the most severe conditions the Bruce. The fortress from going further down. I believe it is 6 feet down the fortress will hold whatever stress my chain set up can support

One caution, my experience may not be your experience. Solutions that work for Me may not work under the Unique conditions that you see.

IslandHopper 28-10-2017 19:37

Re: Best dual anchor configuration?
 
Quote:

Originally Posted by thinwater (Post 2508100)
Try it. Then dive on the anchors. Then tell us what you see after a shift.

I've tried it, lots. Every anchor manufacture, including oil rig anchor manufactures, will tell you it does not and cannot work.

Try it.

While i'm firmly in your camp re tandem anchors on our boats, i have to disagree re rigs and other offshore use.

We routinely use tandem (piggyback been the correct term) anchor setups when the situation demands, BUT, it's a very involved and time consuming process that can take easily a week to complete a whole spread.

When doing a whole spread (up to 8 piggyback sets) these are usually prelaid and tensioned in a straight pull by the anchor handler, long before the rig is even on site, this can take hours for each set and may have to be repeated if they don't set correctly, longest i have sat on one was just under 6 hours with about 90t tension on it until it set and the surveyor was happy.

When all are done and the surveyor is happy they are well "soaked" in, the rig is manoeuvred into position and connected to the free ends and snugged up to there working tension, then they will sit and monitor until happy that all is stable before starting drilling.

As i said it's a very involved exercise and the above description is massively simplified, but the point i'm making is it is used quite often when needed, I couldn't tell you how many times I've been involved in the operation over the years.

But for our use i agree, any lateral pull tends to upset the primary and fails to reset, in my experience anyhow :smile:

billknny 28-10-2017 19:49

Re: Best dual anchor configuration?
 
Quote:

Originally Posted by kas_1611 (Post 2507857)
And I thought I was mad with my 33kg Vulcan on my 40ft boat :biggrin:




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!"

You know your anchor is big enough for long-term, remote, ocean cruising when people walking down the dock point at it and laugh.

Nobody, but nobody, ever work up at 2AM in a storm and stayed awake because they were worried that their anchor was too big!

If you are fussing around with other complex arrangements involving kellets, tandem anchors, etc., you already have decided your main anchor is not big enough.

thinwater 28-10-2017 19:53

Re: Best dual anchor configuration?
 
Quote:

Originally Posted by IslandHopper (Post 2508330)
While i'm firmly in your camp re tandem anchors on our boats, i have to disagree re rigs and other offshore use.

We routinely use tandem (piggyback been the correct term) anchor setups when the situation demands, BUT, it's a very involved and time consuming process that can take easily a week to complete a whole spread.

When doing a whole spread (up to 8 piggyback sets) these are usually prelaid and tensioned in a straight pull by the anchor handler, long before the rig is even on site, this can take hours for each set and may have to be repeated if they don't set correctly, longest i have sat on one was just under 6 hours with about 90t tension on it until it set and the surveyor was happy.

When all are done and the surveyor is happy they are well "soaked" in, the rig is manoeuvred into position and connected to the free ends and snugged up to there working tension, then they will sit and monitor until happy that all is stable before starting drilling.

As i said it's a very involved exercise and the above description is massively simplified, but the point i'm making is it is used quite often when needed, I couldn't tell you how many times I've been involved in the operation over the years.

But for our use i agree, any lateral pull tends to upset the primary and fails to reset, in my experience anyhow :smile:

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

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.

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

IslandHopper 28-10-2017 20:44

Re: Best dual anchor configuration?
 
Quote:

Originally Posted by thinwater (Post 2508336)
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 :smile:

ZULU40 29-10-2017 01:54

Re: Best dual anchor configuration?
 
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 29-10-2017 04:26

Re: Best dual anchor configuration?
 
Quote:

Originally Posted by captstu (Post 2508033)
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 180į 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:

https://fortressanchors.com/SSA.pdf

thinwater 30-10-2017 17:48

Re: Best dual anchor configuration?
 
Originally Posted by thinwater https://www.cruisersforum.com/forums/...s/viewpost.gif
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 :smile:

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 30-10-2017 19:03

Re: Best dual anchor configuration?
 
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 30-10-2017 20:18

Re: Best dual anchor configuration?
 
Quote:

Originally Posted by captstu (Post 2509803)
...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 30-10-2017 20:39

Re: Best dual anchor configuration?
 
Quote:

Originally Posted by Jim Cate (Post 2507561)
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 03-11-2017 15:35

Re: Best dual anchor configuration?
 
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 03-11-2017 22:33

Re: Best dual anchor configuration?
 
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 04-11-2017 17:56

Re: Best dual anchor configuration?
 
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.
Itís 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.


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