Fork or 'V' anchoring

[thinwater]

120 deg is the magic number between the rodes.

The force on B is shared between A1 & A2 so the "200" vector is actually 100 - less than 120° you can't get a greater load on either anchor.

^^ This. Just school trig.

One advantage of a relatively broad angle (>90) is that the lazy rode does not pass over the anchor, reducing the chance of fouling. Another is that the pull angle doesn't change too much even in the 180 spin.

 

[thinwater]

Two anchors on the same rode ONLY works if there is no change (<10 degrees ) in direction of pull, and even then, there are numberous rigging and setting details. I doubt one set in 10 gets it closed to right, based on much testing. This is ONLY for oil platforms.

IF you disagree, please show pictures of two anchors set with an angles pull.

 

[fisherman]

I did it only because I was waiting for water into the harbour, the wind wouldn't change, and I didn't leave the boat. Also, I had a socking great pot winch and numerous hook ropes, grapnels, for retrieval. Fisherman with a plough on 4fm of chain behind....or ahead, depending on which way you look at it.

 

[thinwater]

With two anchors at 120°, and provided the rode is joined forward of the bow roller, is pretty much the definition of a Bahamian Moor. It has the huge advantage over rigging two anchors on the one rode, that the boat is secure in any wind direction, and swings in a very small circle. I have never tried "tandem anchoring" with two anchors on the one rode, but I would imagine that retrieval could be a nightmare, particularly in deeper water.

No, not difficult to retrieve. Tandems are rigged with a retrival line from the shackle to 1-2 meters above the primary so that you can un-weight the secondary before the primary goes on the roller (you can't load the primary with side-load from the secondary). recover to the retrieval line and un-weight the secondary. Retrieve the primary, retrieve the secondary.

Done it many times. However, it is a method for cobbles and similar non-bury bottoms only.

---

I should have been more clear. In about 80% of the trials I performed, having two anchors in a row actually reduced the holding capacity below that of the primary anchor. The second anchor causes the primary to trip and then pins it upside down, or it lifts it off the bottom. I suggest folks test this. You'll surprised.

Just because 2 anchors held does NOT mean it was better. You don't know that.

 

[NormanS]

If it gives a poorer result in 80% of occasions, why on earth do it?

 

[noelex]

The “flying” Rocna:

 

[thinwater]

The “flying” Rocna:

^^Yes, that. I've seen this many, many times.

The tandem method is effective when the anchor can't bury (shale rocks, hard cobbles). However, it must be used at VERY long scope, such that the chain can never lift, not even slightly, not even when the secondary catches and the primary is not (see above). This means 10:1 in deeper water and 20:1 in shallow water. Yes, that much. I've watched anchors lift at 10:1.

And yes, the tandem rode is attached the wrong place, even for cobbles. Of course, look at the attachment.

 

[NormanS]

Personally, I think it's a crazy idea, and obviously so do you if you have found it to fail 80% of the time. Makes me wonder why you've done it "many times". If I find that something doesn't work, I tend not to do it.

For both anchors to share the load, one or both of them has to drag. Nuff said.

 

[noelex]

And yes, the tandem rode is attached the wrong place, even for cobbles. Of course, look at the attachment.

Yes I agree not an ideal implementation.

 

[thinwater]

Personally, I think it's a crazy idea, and obviously so do you if you have found it to fail 80% of the time. Makes me wonder why you've done it "many times". If I find that something doesn't work, I tend not to do it.

For both anchors to share the load, one or both of them has to drag. Nuff said.

A. A lot of the anchoring I have done is for testing for magazine articles and books. It is normal to try everything, every variation, and repeat it many times. It is the only way to be sure and to create data. Thus, I would call it "diligent research."

B. It does work for specific things, reliably. It is the best choice over shale or jointed slabs of rock. There are a few places I frequent where it works well.

I tend to come out opposed to tandem anchoring because I would like people to understand that it is not a "standard" method and that generally, one big anchor, thoughtfully deployed, is better.

V-anchoring has a lot more good, valid applications. However, it still has pitfalls, so one anchor is still generally better.

 

[GHA]

Personally, I think it's a crazy idea, and obviously so do you if you have found it to fail 80% of the time. Makes me wonder why you've done it "many times". If I find that something doesn't work, I tend not to do it.

He tests things for a living.

 

[NormanS]

He tests things for a living.

Hmm, I anchor for real.

 

[GHA]

Hmm, I anchor for real.

You and I and hundreds others on here.

Lucky for us we've the likes of thinwater/noelex/SVPanope-youtube sharing gigbytes of tests/pics/video so the rest of us can get a glimpse of whats really going on down there instead of "it worked last time!" ..

Thanks guys!!

 

[Neeves]

Just because 2 anchors held does NOT mean it was better. You don't know that.

View attachment 71261

I suppose you can also possibly say that just because one big anchor held - does NOT mean it is better? You don't know that.

And the corollary?


On the topic of tandem anchors, Noelex pictures and Thinwater's comments - tandem anchors do not seem very sensible and possibly much more trouble than they are worth.

Edit - I had to check

Peter Smith on his website appears too strongly recommend tandem anchoring on his website, and he would be considered by many as an anchor guru/

http://www.petersmith.net.nz/boat-anchors/tandem-anchoring.php

close edit

Jonathan

 

[Artic Warrior]

Exactly..... if you think 25 knots is going to drag you your main anchor isn't big enough.....and if you need to get away from the anchorage quickly a single system is the key

 

[Neeves]

Exactly..... if you think 25 knots is going to drag you your main anchor isn't big enough.....and if you need to get away from the anchorage quickly a single system is the key

If you drag your main anchor in 25 knots it might be either size, design (or both) at fault. No-one has suggested they are going to drag at 25 knots, which is pretty benign.

Reiterating earlier posts by a number of members - anchoring in a 'V' reduces veering which makes living on board much more comfortable. The 'V' is not necessarily intended to improve hold, though it does (because it reduces veering), but improves comfort.

If you need to move, quickly, not necessary (so far) in my many years - buoy the anchor. If you need to move out of the way of an errant yacht - simply take in the rode on one anchor and lie on that anchor - providing room for the dragging yacht to pass, assuming you have set the 'V' wide enough. Quicker than taking in a single anchor - and leaves you where you were/are.

Jonathan

 

[noelex]

If you need to move out of the way of an errant yacht - simply take in the rode on one anchor and lie on that anchor - providing room for the dragging yacht to pass, assuming you have set the 'V' wide enough.

How do you stop the dragging boat catching your anchor rode?

This is a significant problem when deploying two anchors in a “V’ configuration. When lying to a single anchor, the chain will be laid out downwind and a boat traveling in the same direction, which is how a dragging boat will be moving, only has a small chance of catching your rode.

Once you start deploying anchors at an angle, the risk of someone catching your rode becomes much greater. Typically, if a dragging boat hooks your rode, the anchor will slide down your rode towards your boat. It quickly becomes a mess. Often a dangerous mess.

 

[thinwater]

Exactly..... if you think 25 knots is going to drag you your main anchor isn't big enough.....and if you need to get away from the anchorage quickly a single system is the key

Agreed, with two thoughts:

a. It should not take more than a few more minutes to recover a second anchor, if it is rigged correctly. I have done this countless times, most often when testing anchors so that I could insure that my boat was a stationary platform as I pulled other single anchors with winches.

b. A sailor should not have to get away in a hurry, at least not where a few minutes matter. The heart of seamanship is planning ahead, and weather does not change so quickly. The only likely possibility is someone dragging down on you, in which case moving forward to breakout any anchor is likely a poor option. It's probably better to let the whole business go with a bouy and come back later (there should be a third anchor and rode somewhere in the bilge). Alternatively, if you are lying to two anchors and someone is dragging straight at you this is even simple than one anchor; just let one of them go and swing to the other. Very fast. It should be reflex, since this is often part of the two anchor drill. I doubt that would take me one minute.

 

[thinwater]

How do you stop the dragging boat catching your anchor rode?

This is a significant problem when deploying two anchors in a “V’ configuration. When lying to a single anchor, the chain will be laid out downwind and a boat traveling in the same direction, which is how a dragging boat will be moving, only has a small chance of catching your rode.

Once you start deploying anchors at an angle, the risk of someone catching your rode becomes much greater. Typically, if a dragging boat hooks your rode, the anchor will slide down your rode towards your boat. It quickly becomes a mess. Often a dangerous mess.

Correct. A crowded anchorage is a poor place for a V anchor rig, for a number of reasons, including swing. To avoid a drager you need to cast off and buoy the rode. Not difficult.

Of course, in countless anchor nights, I've seen people drag, but never from directly up wind. This is one of those thing that depends on where you anchor; answers aren't universal and many posters (including me) seldom share an anchorage with more than a few boats, and very seldom within hundreds of yards. However, in general, if you need two anchors AND it is crowded, this is not a good situation.

 

[Neeves]

In general if you are in an anchorage where winds, measured on your yacht, are going to be in excess of 25/30 knots then it is unlikely to be a crowded anchorage (because the crowds will stay in a marina). There are always exceptions to any situation but damning something, a product or a technique, because your experiences are based on one situation lacks some validity. As Thinwater says we seldom see other yachts, at all, but if a small anchorage has 10 yachts then it is very likely to be very well sheltered and there is then less need, or no need, for a 'V'.

Because we do not see many yachts we would seldom find ourselves forced to anchor direct down wind of other yachts - where winds are likely to exceed 25/30 knots (measured at the masthead). If winds are to exceed 25/30 knots we would consciously go out of our way to ensure we were no-where near 'dead down wind' - for the very reason - you do not know the skill of the upwind yacht, nor the seabed where they are anchored, nor the gear they are using. Any technique or product needs to be used with care - no anchor is perfect, I'm sure even the claimed gurus get it wrong (and why most use an anchor alarm), seabeds vary - its all about awareness and seamanship. On this latter - everyone claims confidence in their NG tackle - so why do they set an anchor alarm?

Its horses for courses and prudence.

Jonathan