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brokesailor 12-07-2008 08:39 AM

Anchoringing techniques
 
I have read about placing to anchors in series for better holding during high winds. How/where do you attach the add on anchor? I remember it was descibed I think on Cruising Mag but I didn't get it.

sailingdog 12-07-2008 09:59 AM

Brokesailor-

You're talking about tandem anchoring, and it has been discussed quite often on this forum previously. However, I generally don't recommend it, as a properly sized primary anchor should be sufficient to the task. If it isn't your ground tackle is undersized at best.

Part of the problem with using tandem anchors is that it is very difficult to set the two anchors sufficiently. If the two anchors are the same design, the primary anchor will usually set before the secondary, because it is closer to the boat, and the load on the anchor rode will cause it to set, and unless the connection between the two anchors is perfectly taut when you start backing down to set them, the first will set before the second gets a chance to.

Some anchors have a specific attachment point on the crown of the anchor for tandem anchoring setups. That is generally the best location to use to attach the two.

The anchors should be separated by at least a boat length of chain IMHO. Anything less than that will generally mean that the secondary anchor is trying to set in ground disturbed by the primary, reducing the holding power it can generate. This is also a big reason why a larger single anchor makes more sense than two smaller anchors.

Finally, if the tandem anchor setup is exposed to a reversing wind/current, the two anchors may foul one another, preventing the setup from resetting properly. This is far less an issue with a properly sized single anchor.

Valiente 12-07-2008 01:32 PM

Good thing our Portuguese friend doesn't post in "Cruising" very often...because he doesn't think he's a cruiser!

sailingdog 12-07-2008 04:19 PM

When his wife is aboard, he is most definitely a cruiser, regardless of what he thinks. :)
Quote:

Originally Posted by Valiente (Post 413302)
Good thing our Portuguese friend doesn't post in "Cruising" very often...because he doesn't think he's a cruiser!


Omatako 12-08-2008 12:55 AM

Brokesailor

Don't believe everything you read in the papers . . . . . .

A properly sized anchor will hold you when things are normal or even slightly abnormal. An oversized anchor will do it better but will be a PITA in other ways. Any prudent cruiser will have AT LEAST two anchors on a vessel. Some carry a lot more (I try to have 4 when I'm sailing long distance).

When the situation calls for more than the "properly sized" anchor will deliver (strong wind coupled to tidal surge and once for me, a flowing river) then two anchors are better.

Dual anchors in a V formation work for some but wouldn't be my choice for a range of reasons. Tandem anchoring is IMHO far better.

One thing I will agree with is a decent length of chain between the anchors and one boat length ain't enough. I have done this more than once and I let the first anchor out on 25 metres of chain, let out the rode until the second anchor is not quite ready to dig. Then I pull back, dig the front anchor. Then I motor forward and let the second anchor hit the bottom and pull back while the rest of the rode goes out.

Remember too, if you need two anchors, the reality is you also need a lot more rode out than you ordinarily would use.

So in short, if you reckon you're going to need some extra comfort to sleep well, there is nothing wrong with using two anchors. Yes, they're a bit of work when the tide changes direction but tandem anchors hold very strongly.

Valiente 12-08-2008 02:12 PM

Andre, would you say that in a tandem anchoring situation that you start counting the scope from the second anchor (the one closest to the boat) and try to get 7:1 or better from there, or are you advocating even more scope and rode?

Omatako 12-09-2008 02:32 AM

Quote:

Originally Posted by Valiente (Post 413819)
Andre, would you say that in a tandem anchoring situation that you start counting the scope from the second anchor (the one closest to the boat) and try to get 7:1 or better from there, or are you advocating even more scope and rode?

I'm just suggesting that if there is a need to deploy tandem anchors, the conditions are likely to be pretty demanding and when they are, the more rode the better. Deploying tandem anchors is not easy and managing them when things change is even more challenging so I wouldn't do it unless there was a genuine need.

I normally deploy 5-1 and if the conditions suggest tandem anchors I would go with 7-1 from the second anchor .

Also just have a care if there are other boats anchored nearby because if they deploy significantly less, you could end up swinging onto them.

Giulietta 12-09-2008 03:34 AM

Quote:

Originally Posted by brokesailor (Post 413203)
I have read about placing to anchors in series for better holding during high winds. How/where do you attach the add on anchor? I remember it was descibed I think on Cruising Mag but I didn't get it.

Val..luckily I read all forums..eheheheh


Brokesailor..(now that's a funny name!!)...

If you read and do everything you read here, you will endup sailing a Cabo Rico or a Valiant built in 1234 B.C., with no sails (sailing is dangereous, and those don't sail anyway)..with 3 extra hulls, 12 bbq's, a brand new 3200HP Caterpillar engine, and be freightfull of sailing for the rest of your life...

read this bellow....and go anchor with a tandem set up...AT LEAST TRY IT YOURSELF...DO IT....I have beed doing it for over 20 years and am still here..fishing vessels in my country do it since the time of Vasco da Gama...

I wrote this HERE


I anchor many many times in a place called Culatra Island, here in Portugal.

It has 3 to 5 knot currents twice a day, in both directions.

I have been using the tandem method here, for over 20 years, and never draged once. Do it only one anchor I don't care what anchor.....and bye bye...

I use a smaller Danforth anchor (14kg) with 10 feet of rope, attached to the "head" of my main anchor, a 28Kg plow, then chain, then rope. Here is what everyone uses, or you're dragging all the time.

Works for me, and for the others. Our bottom is mud / sand / weed.

Some say its a disater waiting to happen (specially Craig Smith of Rocna, but he is he, and I am me....,) if the smaller first anchor rolls around the primary as the boat circles with the current. So far in over 20 years no problem what so ever.

I do it.

Here is a drwing

http://i125.photobucket.com/albums/p...sc/culatra.jpg


then go HERE

HERE

brokesailor 12-09-2008 02:36 PM

Thanks for the sketch and simple explanation!!

sailaway21 12-09-2008 04:02 PM

I fear the simple explanation belies the complexity of the operation. What Giu has diagrammed is simply an anchor resetting device; one that aids the primary anchor resetting on the change of the tide. I, like many others, think that either a single anchor well set or a Bahama moor would be superior to the method shown, certainly in terms of ease of use and lack of fouling.


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