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-   -   Slightly unorthodox anchoring technique (http://www.sailnet.com/forums/seamanship-navigation/17999-slightly-unorthodox-anchoring-technique.html)

Iraklis 07-07-2006 02:31 PM

Slightly unorthodox anchoring technique
 
Hi everyone,

My (possibly wrong) intuition tells me that the best way for an anchor to set is the following: after the initial tug, let out all the rode you can, and then motor in reverse. This will keep the anchor most parallel to the sea floor & should allow it to set better. Afterwards, you can reduce to whatever scope you'd normally use.

My thinking goes as follows: unless you do this, the force that will dislodge the anchor at its final scope (e.g. 7:1) will be the same as the maximum force you can use when motoring backwards. Using e.g. 10:1 just at the "setting" phase should allow you to bury it even more. I'm not saying that this will make 7:1 work just like 10:1 - all I'm saying is that this would bury the anchor deeper, which should be a good thing. This would probably hold true for any anchor that requires you to motor backwards.

I am familiar with the "proper" way to do this. However, I only suggested this as an idea and my sailing instructor almost failed my ASA bareboat certification (I guess he took it as a statement instead of a question). Obviously, there are situations (e.g. med mooring) where you can't do this. But can any saltier SailNet member think of something wrong with this approach?

Thanks,
Iraklis

sailingdog 07-07-2006 02:48 PM

I can see some potential issues with doing it this way.

The first being, if you're on an all chain rode, not being able to apply enough force on the anchor to actually get it to set properly. Most sailboat auxiliary engines are not powerful enough to set a long length of chain rode, as most are a bit underpowered as it is.

The second being that many anchorages don't have enough room to do it this way, and if you get in this habit, you will find that in an emergency, where you default to what you know best, you'll get screwed over pretty badly.

Those are the two that jump out immediately to me... but there are probably some other fairly serious reasons not to learn to do this as a default.

Nathan West 07-07-2006 03:37 PM

The purpose of using the engine in reverse is two fold. The first is to set the anchor. The second is paradoxically to try and break the anchor lose, its much more convenient to have the anchor fail when you are behind the helm with the engine running than at 3:00 AM. Your anchoring method should work but after shortening your anchor line to the desired scope I would again back down on the anchor to make sure its holding.

camaraderie 07-08-2006 11:41 AM

Ditto the above replies + in a muddy bottom, you're gonna be cleaning a lot of rode every time you drop the hook. Not very practical.

Omatako 07-08-2006 06:57 PM

If you're using a combination of a shortish length of chain then rope rode you also risk snagging the rope on whatever is lying between your boat and your anchor and shortening the life of the rode (or worse cutting it through and losing your anchor!!).
This is especially so if you're anywhere near coral.

Irwin32 07-11-2006 11:02 PM

It is difficult to back many sailboats straight. Once all that rode is dumped out, how can one be sure that one is backing out the rode in a straight line.

I like to drop my anchor and ease out the scope as the anchor gently digs itself in. I give some easy tugs in reverse at 3:1 and 4:1 before I give the final test. Has worked so far and have not dragged yet using this technique. But then again, you know what the farmer said when his horse died: "Funny, he never did that before"

SoOkay 07-13-2006 05:57 PM

Iraklis,
I think you'll end up dragging more times than not, and have much rode to take up and try again. But hey, "My horse has never done that yet either"

Harry

captnnero 08-04-2006 02:46 PM

The others have come up with the complications to the "let it all out idea". In practice it usually works fine just to let a fair scope (5or7:1) out first and try it. If it won't grab then let a bunch more out and try again, which will probably work. If it still won't grab you've got a grassy bottom, the wrong anchor for the bottom type, or even something wedged in the anchor hinge as happens with Danfoth types.

solent 08-04-2006 09:58 PM

Let it all out!!!
 
Reading theses posts explain why at some achorages yachts are swinging into the position of other yachts. There is a certain amount of rode required depending on the depth of water. The anchor is not what holds the boat, it is the water pressure pressing down on the surface of the rope as the boat pulls on it.

sailingdog 08-04-2006 10:54 PM

Quote:

Originally Posted by solent
Reading theses posts explain why at some achorages yachts are swinging into the position of other yachts. There is a certain amount of rode required depending on the depth of water. The anchor is not what holds the boat, it is the water pressure pressing down on the surface of the rope as the boat pulls on it.

This answer is so wrong in so many ways.... Actually the water pressure has nothing to do with it... Water pressure on the rode is effectively neutral, as almost as much water is pushing down on the water as is pushing up on the water. There is some buoyancy, which works against the rode sinking, but with an all-chain rode, this is minimal, with an all-rope chain it is still not really a factor. You might want check your facts before posting again.

The scope is what determines what angle the rode will pull at. With an all chain rode, the scope can be shorter, as the weight of the chain will cause it to hang in a catenary curve, and the part of the chain near the anchor will be close to parallel with the bottom. With a combination rode or an all-rope rode, the scope has to be greater, as the line does not have the weight to hang in a catenary curve, against the tension caused by the boat, which is being pushed by the current and/or wind. The closer to parallel that the rode pulls on the anchor, the less likely the anchor is to pull free as a general rule.

The anchor, and in the case of an all-chain rode, the weight of the rode, are what hold the the anchor and rode against the bottom initially, but are not what hold the boat in position. Most anchors do not depend on the weight of the anchor as the sole factor providing the holding power. Spade, plow, fluke, and next generation anchors, like the Rocna, Buegel, and Bulwagga, all depend on burying into the holding medium to provide the bulk of the holding power.


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