|
chriisu
Jun 14, 2011, 10:28 AM
Post #1 of 60
(25129 views)
Shortcut
Registered: May 26, 2009
Posts: 5
|
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.
|
|
|
|
|
devkrev
Jun 14, 2011, 10:43 AM
Post #2 of 60
(25115 views)
Shortcut
Registered: Sep 28, 2004
Posts: 933
|
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, 12:30 PM
Post #3 of 60
(25064 views)
Shortcut
Registered: Nov 23, 2010
Posts: 247
|
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, 12:37 PM
Post #4 of 60
(25054 views)
Shortcut
Registered: Nov 19, 2002
Posts: 4602
|
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
|
|
|
|
|
trenchdigger
Jun 14, 2011, 12:54 PM
Post #6 of 60
(25040 views)
Shortcut
Registered: Mar 9, 2003
Posts: 1447
|
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, 12:57 PM)
|
|
|
|
|
TarHeelEMT
Jun 14, 2011, 12:59 PM
Post #7 of 60
(25035 views)
Shortcut
Registered: Jun 20, 2009
Posts: 724
|
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, 1:06 PM
Post #8 of 60
(25028 views)
Shortcut
Registered: Nov 23, 2010
Posts: 247
|
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, 1:15 PM
Post #9 of 60
(25017 views)
Shortcut
Registered: Nov 23, 2010
Posts: 247
|
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, 1:24 PM
Post #10 of 60
(25005 views)
Shortcut
Registered: Mar 9, 2003
Posts: 1447
|
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, 1:35 PM
Post #11 of 60
(24995 views)
Shortcut
Registered: May 26, 2009
Posts: 5
|
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, 1:36 PM)
|
|
|
|
|
ddooddodo
Jun 14, 2011, 1:36 PM
Post #12 of 60
(24993 views)
Shortcut
Registered: May 17, 2010
Posts: 23
|
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, 1:46 PM
Post #13 of 60
(24978 views)
Shortcut
Registered: Mar 9, 2003
Posts: 1447
|
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 $23 and get one of these if you're concerned about weight or bulk. Or be like the rest of us and get 25' of 7 or 8mm cord that's a little bulkier but will last 3x as long for about the same price.
|
|
|
|
|
patto
Jun 14, 2011, 1:48 PM
Post #14 of 60
(24974 views)
Shortcut
Registered: Nov 15, 2005
Posts: 1453
|
trenchdigger wrote: So essentially, as with any statically equalized system, you're relying primarily on redundancy for anchor strength rather than good equalization. In most cases that's fine. What I don't like about this case is that you're essentially using single strands of a spectra sling as each arm of the anchor system. The sling as a loop is about 22kn strong, which means each arm will be ~11kn strong. Add loss to a clove hitch to that, and you're down in the 7-8kn territory.
THIS is a very compelling argument.
You are significantly weakening every single arm of your anchor while gaining nothing over many other systems. Stay away from this over complication.
|
|
|
|
|
JimTitt
Jun 14, 2011, 4:29 PM
Post #15 of 60
(24870 views)
Shortcut
Registered: Aug 7, 2008
Posts: 1002
|
Personally I´d have opened the windows and tied the rope around the pillar between them but then I´m a bit old-school anyway.
|
|
|
|
|
devkrev
Jun 14, 2011, 7:02 PM
Post #16 of 60
(24784 views)
Shortcut
Registered: Sep 28, 2004
Posts: 933
|
trenchdigger wrote: chriisu wrote: The main advantage of this setup is that it's possible to do with quite short slings. In my example anchor four pieces were tied off with a 120cm sling. The same setup with cordalette would have required about double length of sling. The tradeoff seems to be the strength of the system as tenchdigger pointed out. Which I don't think is worth it. Inadequate safety factor is the reason we don't use 4 or 5mm cord for a cordelette to save weight/bulk/$. 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, 8:01 PM
Post #17 of 60
(24749 views)
Shortcut
Registered: Mar 29, 2009
Posts: 606
|
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.
|
|
|
|
|
cracklover
Jun 14, 2011, 9:46 PM
Post #19 of 60
(24691 views)
Shortcut
Registered: Nov 14, 2002
Posts: 10162
|
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 15, 2011, 1:44 AM
Post #20 of 60
(24637 views)
Shortcut
Registered: Nov 15, 2005
Posts: 1453
|
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.
|
|
|
|
|
devkrev
Jun 15, 2011, 1:56 PM
Post #21 of 60
(24547 views)
Shortcut
Registered: Sep 28, 2004
Posts: 933
|
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. 
I am also able to cut spectra with my pocket knife.....who knows where I got that assumption from, I guess I was wrong.
|
|
|
|
|
cracklover
Jun 15, 2011, 4:32 PM
Post #22 of 60
(24522 views)
Shortcut
Registered: Nov 14, 2002
Posts: 10162
|
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 16, 2011, 12:24 AM
Post #23 of 60
(24453 views)
Shortcut
Registered: Nov 15, 2005
Posts: 1453
|
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 16, 2011, 1:29 AM
Post #24 of 60
(24432 views)
Shortcut
Registered: Jun 5, 2003
Posts: 110
|
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 16, 2011, 1:29 AM)
|
|
|
|
|
rescueman
Jul 5, 2011, 6:50 PM
Post #25 of 60
(24109 views)
Shortcut
Registered: Mar 1, 2004
Posts: 439
|
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 (<300°F) compared to nylon (420°-480°F), an even lower critical temperature of 150°F, 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 6, 2011, 12:04 AM)
|
|
|
|
|
|
|
|
|
1
