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chriisu


Jun 14, 2011, 3:28 AM
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Clove hitch anchor equalization
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Alright, let's try yet another anchor critique thread. Flame on!

Is there anything wrong using clove hitches for connecting and equalizing pieces of protection to the master point? Example of such anchor below. The strands between two clove hitches are unweighted.




Partner devkrev


Jun 14, 2011, 3:43 AM
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Re: [chriisu] Clove hitch anchor equalization [In reply to]
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chriisu wrote:
Alright, let's try yet another anchor critique thread. Flame on!

Is there anything wrong using clove hitches for connecting and equalizing pieces of protection to the master point? Example of such anchor below. The strands between two clove hitches are unweighted.

[img]http://farm4.static.flickr.com/3660/5831723071_c335dc412b_z.jpg[/img]


Lets do some critical thinking...

What do you think some of the pros and cons of such a set up are?


michael1245


Jun 14, 2011, 5:30 AM
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Re: [chriisu] Clove hitch anchor equalization [In reply to]
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I would have just tied a cordellette. everything would equalize at the master point at one knot, instead of 4 knots that weaken the system.


blueeyedclimber


Jun 14, 2011, 5:37 AM
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Re: [chriisu] Clove hitch anchor equalization [In reply to]
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chriisu wrote:
Alright, let's try yet another anchor critique thread. Flame on!

Is there anything wrong using clove hitches for connecting and equalizing pieces of protection to the master point? Example of such anchor below. The strands between two clove hitches are unweighted.

[img]http://farm4.static.flickr.com/3660/5831723071_c335dc412b_z.jpg[/img]

Because you're defeating the purpose of actually using a cordellete/powerpoint system. If you are going to go with clove hitches, then why don't you just use the rope?

Josh


Partner devkrev


Jun 14, 2011, 5:38 AM
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Re: [michael1245] Clove hitch anchor equalization [In reply to]
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michael1245 wrote:
I would have just tied a cordellette. everything would equalize at the master point at one knot, instead of 4 knots that weaken the system.


I might be mistaken, but I don't think knots have a cumulative effect of cordage...So your one knot is just as bad as 4 or 5...I think.

Someone correct me if I'm wrong.


trenchdigger


Jun 14, 2011, 5:54 AM
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Re: [chriisu] Clove hitch anchor equalization [In reply to]
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As with a normally tied off cordelette, you have a statically equalized system. Everything is fine and dandy until your load shifts 3 degrees to the left.

With any statically equalized system, you run the risk (with relatively high probability) of loading only one or two of the strands. Even in the ideal direction of pull, the loads will be uneven due to stretch, however minimal.

So essentially, as with any statically equalized system, you're relying primarily on redundancy for anchor strength rather than good equalization. In most cases that's fine. What I don't like about this case is that you're essentially using single strands of a spectra sling as each arm of the anchor system. The sling as a loop is about 22kn strong, which means each arm will be ~11kn strong. Add loss to a clove hitch to that, and you're down in the 7-8kn territory.

Now combine that decreased load handling with the poor equalization inherent in a statically equalized system and you've got an anchor that's going to start to fail at relatively small loads.

Is it strong enough? Probably... But why not use a simple, quicker, stronger option like the standard tied off cordelette (for static equalization and great redundancy) or if you insist on using clove hitches, the equalette (for the best possibly equalization with adequate strength and redundancy)? The strength of either of these alternatives should be approximately double your pictured anchor system.


(This post was edited by trenchdigger on Jun 14, 2011, 5:57 AM)


TarHeelEMT


Jun 14, 2011, 5:59 AM
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Re: [chriisu] Clove hitch anchor equalization [In reply to]
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It's not heinously unsafe or anything, but it doesn't offer any advantages that I can see over a tied off cordalette. Which begs the question... Why do it?


michael1245


Jun 14, 2011, 6:06 AM
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Re: [devkrev] Clove hitch anchor equalization [In reply to]
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I try to use the least amount of knots.

But it's this set up. There's really no need for all the clove hitches. Cordellette is one and done.


michael1245


Jun 14, 2011, 6:15 AM
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Re: [trenchdigger] Clove hitch anchor equalization [In reply to]
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trenchdigger wrote:
As with a normally tied off cordelette, you have a statically equalized system. Everything is fine and dandy until your load shifts 3 degrees to the left.

With any statically equalized system, you run the risk (with relatively high probability) of loading only one or two of the strands. Even in the ideal direction of pull, the loads will be uneven due to stretch, however minimal....

That's always in the back of my mind...that a cordellete is never really 100% equalized.

So I ask an AMGA Guide is it really the best option? What about a sliding-x or an equalette? And they always say cordellete.

And so like you say, whenever I tie a cordellette I rely on the redundancy of the pro. I think there were what, four in this picture? For me, four bomber peices is a solid anchor for a cordellete.


trenchdigger


Jun 14, 2011, 6:24 AM
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Re: [michael1245] Clove hitch anchor equalization [In reply to]
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There is no single anchor option that is always the best. What do I use? Probably in order of frequency of use: 1. a tied off cordelette 2. the rope (double loop 8 or bowline on a bight) or 3. an equalette.


chriisu


Jun 14, 2011, 6:35 AM
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Re: [TarHeelEMT] Clove hitch anchor equalization [In reply to]
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TarHeelEMT wrote:
It's not heinously unsafe or anything, but it doesn't offer any advantages that I can see over a tied off cordalette. Which begs the question... Why do it?

The main advantage of this setup is that it's possible to do with quite short slings. In my example anchor four pieces were tied off with a 120cm sling. The same setup with cordalette would have required about double length of sling. The tradeoff seems to be the strength of the system as tenchdigger pointed out.


(This post was edited by chriisu on Jun 14, 2011, 6:36 AM)


ddooddodo


Jun 14, 2011, 6:36 AM
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Re: [trenchdigger] Clove hitch anchor equalization [In reply to]
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On a slightly different note you can also replace the figure eight with a sliding x. That will equalize much better than a figure eight but will bring about the problem of shock loading.
Pick yur poison


trenchdigger


Jun 14, 2011, 6:46 AM
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Re: [chriisu] Clove hitch anchor equalization [In reply to]
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chriisu wrote:
The main advantage of this setup is that it's possible to do with quite short slings. In my example anchor four pieces were tied off with a 120cm sling. The same setup with cordalette would have required about double length of sling. The tradeoff seems to be the strength of the system as tenchdigger pointed out.

Which I don't think is worth it. Inadequate safety factor is the reason we don't use 4 or 5mm cord for a cordelette to save weight/bulk/$. Spend $23 and get one of these if you're concerned about weight or bulk. Or be like the rest of us and get 25' of 7 or 8mm cord that's a little bulkier but will last 3x as long for about the same price.


patto


Jun 14, 2011, 6:48 AM
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trenchdigger wrote:
So essentially, as with any statically equalized system, you're relying primarily on redundancy for anchor strength rather than good equalization. In most cases that's fine. What I don't like about this case is that you're essentially using single strands of a spectra sling as each arm of the anchor system. The sling as a loop is about 22kn strong, which means each arm will be ~11kn strong. Add loss to a clove hitch to that, and you're down in the 7-8kn territory.

THIS is a very compelling argument.

You are significantly weakening every single arm of your anchor while gaining nothing over many other systems. Stay away from this over complication.


JimTitt


Jun 14, 2011, 9:29 AM
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Personally Id have opened the windows and tied the rope around the pillar between them but then Im a bit old-school anyway.


Partner devkrev


Jun 14, 2011, 12:02 PM
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trenchdigger wrote:
chriisu wrote:
The main advantage of this setup is that it's possible to do with quite short slings. In my example anchor four pieces were tied off with a 120cm sling. The same setup with cordalette would have required about double length of sling. The tradeoff seems to be the strength of the system as tenchdigger pointed out.

Which I don't think is worth it. Inadequate safety factor is the reason we don't use 4 or 5mm cord for a cordelette to save weight/bulk/$. Spend $23 and get one of these if you're concerned about weight or bulk. Or be like the rest of us and get 25' of 7 or 8mm cord that's a little bulkier but will last 3x as long for about the same price.

Besides cost, something that I feel gets overlooked sometimes...

I like being able to chop my cordelette for rap anchors or prussiks or whatever...good luck cutting spectra with a pocket knife.

Those DMM videos of the slings breaking didn't instill confidence in knotted spectra in me either...


dev


Rudmin


Jun 14, 2011, 1:01 PM
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ddooddodo wrote:
On a slightly different note you can also replace the figure eight with a sliding x. That will equalize much better than a figure eight but will bring about the problem of shock loading.
Pick yur poison

^This is my anchor of choice for equalizing a nest of stuff. Load gets spread out somewhat evenly to all arms. Not much shock loading unless two pieces fail, and it's redundant.


patto


Jun 14, 2011, 1:25 PM
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devkrev wrote:
I like being able to chop my cordelette for rap anchors or prussiks or whatever...good luck cutting spectra with a pocket knife.

I must have exceptional luck or an exceptionally sharp pocket knife. Angelic


Partner cracklover


Jun 14, 2011, 2:46 PM
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chriisu wrote:
TarHeelEMT wrote:
It's not heinously unsafe or anything, but it doesn't offer any advantages that I can see over a tied off cordalette. Which begs the question... Why do it?

The main advantage of this setup is that it's possible to do with quite short slings. In my example anchor four pieces were tied off with a 120cm sling. The same setup with cordalette would have required about double length of sling. The tradeoff seems to be the strength of the system as tenchdigger pointed out.

The other advantage is that if the clove hitches slip a tiny bit under heavy load they would equalize better than a standard cordelette.

To me, it seems like it's plenty strong, and being able to link 4 pieces with one sling is nice.

The only major downside I see is that when you weight this at the belay, you've got a lot of stuck knots you have to undo every pitch. That's a fair amount of wasted time.

GO


patto


Jun 14, 2011, 6:44 PM
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cracklover wrote:
The other advantage is that if the clove hitches slip a tiny bit under heavy load they would equalize better than a standard cordelette.

Slipping, heavy load, low melting point.... This is getting better and better.


Partner devkrev


Jun 15, 2011, 6:56 AM
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patto wrote:
devkrev wrote:
I like being able to chop my cordelette for rap anchors or prussiks or whatever...good luck cutting spectra with a pocket knife.

I must have exceptional luck or an exceptionally sharp pocket knife. Angelic


I am also able to cut spectra with my pocket knife.....who knows where I got that assumption from, I guess I was wrong.


Partner cracklover


Jun 15, 2011, 9:32 AM
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patto wrote:
cracklover wrote:
The other advantage is that if the clove hitches slip a tiny bit under heavy load they would equalize better than a standard cordelette.

Slipping, heavy load, low melting point.... This is getting better and better.

I have never heard of clove hitches in spectra failing in dynamic loading situations due to melting. Have you?

GO


patto


Jun 15, 2011, 5:24 PM
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cracklover wrote:
I have never heard of clove hitches in spectra failing in dynamic loading situations due to melting. Have you?

No. But I've never heard of such an anchor being used in a high fall factor situation. Have you?

I'm not saying they will melt, in fact I'd say they would likely not melt. But that whole anchor seems unnecessarily compromised. There are other many better ways.


nafod


Jun 15, 2011, 6:29 PM
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chriisu wrote:
Alright, let's try yet another anchor critique thread. Flame on!

Is there anything wrong using clove hitches for connecting and equalizing pieces of protection to the master point? Example of such anchor below. The strands between two clove hitches are unweighted.

So it looks like you're using one long runner? In that case, I'd fiddle with it to remove the slack in the strand between the clove hitches where it is unweighted. After that, you'd have your anchor equalized over four pieces of pro with no chance of shock loading for a single piece failure (and the load as designed for). Still, only two loops of spectra going around the hotpoint biner don't give me a warm and fuzzy. Spectra is strong as all, but far too easy to cut. That's just me.


(This post was edited by nafod on Jun 15, 2011, 6:29 PM)


rescueman


Jul 5, 2011, 11:50 AM
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Re: [cracklover] Clove hitch anchor equalization [In reply to]
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cracklover wrote:
I have never heard of clove hitches in spectra failing in dynamic loading situations due to melting. Have you?

Spectra has a much lower melting point (<300F) compared to nylon (420-480F), an even lower critical temperature of 150F, and is more likely to fail in a shock-load. It also has high lubrisity or slipperiness, so it doesn't hold a knot (or clove hitch) as well.

I do not use Spectra (or any high-strength cordage) in any application, except as factory slings on protection. High strength-to-weight ratio is useless if it has a higher failure potential when the proverbial crap hits the fan.

Nylon cords and slings are still the most versatile, inexpensive and reliable in all applications and failure modes.

Check out the Tom Moyer/Black Diamond test report presented at the 2000 International Technical Rescue Symposium: http://www.xmission.com/...gh_Strength_Cord.pdf


(This post was edited by rescueman on Jul 5, 2011, 5:04 PM)

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