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]

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]

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.

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....

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.

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.

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.

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

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

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.

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

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?

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.

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

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

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

...it makes little sense to choose the high tech cords.

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

However I doubt you can actually buy pure Spectra/Dyneema tape, all the tape I know of is a hybrid with nylon and both ourselves and others have noted in testing that this has a higher friction than pure nylon tape or cord, the reason and exact mechanism for this is not known.

As pointed out in the link you gave the Spectra/Nylon hybrid tape was an excellent performer

Friction in a Prusik? We/I am talking about friction over a karabiner in cordalette/equalette setups and as related to clove hitches.

There is no UIAA drop test for slings, tape or accessory cord.

Yes, I understand that, but this test offers some suggestion of the relative friction qualities of the various materials. And the main reason that Spectra is mixed with nylon is because the Spectra alone has almost no friction or knot-holding capacity (plus it's vulnerable to UV and tends to creep).

Perhaps there should be, since it's these anchors that we're falling on.

As Tom Moyers states in his ITRS report on Comparative Testing of High Strength Cord, "Since these are used as anchors, the UIAA spec for maximum dynamic-rope impact force is shown for comparison. This represents a typical worst-case force on the rope. However, if the belay is run through the anchor, force on the anchor is multiplied. A level 170% of the UIAA spec - an assumed maximum - is also shown for comparison. It is apparent from this chart that at least some of these cordelettes would be expected to fail a UIAA drop test."

If that's not a concern for you, it certainly should be.

...I never use a webolette, cordalette or whatever and have a fundamental dislike of running the lead rope through the belay in a way that can potentially lead to such high impact forces.Jim

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.

If the hitches are not uniformly set then slippage under load would dis-equalize the anchor, and there will be no sling stretch to self-equalize the forces as there would be with a nylon cord.

Is there anything wrong using clove hitches for connecting and equalizing pieces of protection to the master point?

If you are going to go with clove hitches, then why don't you just use the rope?

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.

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.

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?

Stay away from this over complication.

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.

The only knot in there is the central point, and assuming you have a specific belay sling, that stays there for the whole climb.
The other stuff are clove hitches, you just slip them over the nose of the carabiner, and youre done. Even easier with keylocks.

qwert

So what you're saying is the micro-equalizing of the system by way of material stretch is good but the micro-equalizing of the system by way of cinching/slipping knots is bad?

Sounds like they accomplish the same thing to me.

But the legs are unequal length so surely a stretchy cord will not equalise in a micro or macro sense anyway?

Jim

No, I'm saying that a completely static high-strength sling is not going to offer any equalization from stretch, and unless those clove hitches are all equally tight and equally tight to the master point, it's not a well-equalized anchor.

From the picture, it looks like only the top right clove hitch is tight and that piece may take all the load.

Well, it surely wont equalize as good as a sliding x (though that's equalization properties are also questionable), but from how i look at it, it should offer some equalization.

Actually that is one of the things this anchor is supposed to do (at least according to the DAV).

You thighten the clove hitches in such a way that you put the load mostly on those points that you think that are best, and have the others as a kind of backup.

The friction in a sliding X or any other setup doesn´t slow down equalisation, it prevents it ever occuring no matter the speed or impact.


Surely it is irrelevant in which order the pieces are loaded and fail, the total of the energy absorbed by the work of ripping/breaking them is the same?

Or, better yet, use a pre-equalized, fixed, focused anchor using a somewhat dynamic nylon cordalette with double strands to each piece and tied into a master point so the load is as distributed as evenly as possible.

Then you don't have to bring your calculator or laptop and spreadsheet to calculate the loading potentials for each anchor.

... i would say the clove hitch anchor is easier to tie in such a way that it is equalized that the cordalette.

...are unlikely to convince a die-hard stretchy-string man

And as is pointed out, tying that enormous knot screws it all up completely anyway.

I´ve tested just about all the configurations and equalised is not the word that springs to mind

"Or, better yet, use a pre-equalized, fixed, focused anchor using a somewhat dynamic nylon cordalette with double strands to each piece and tied into a master point so the load is as distributed as evenly as possible."

But we were talking about equalising, well you were Since you (wisely) don´t trust the word equalised...

The word I don't trust is "equalizing"

"Though one may be overpowered, two can defend themselves. A cord of three strands is not quickly broken." - Ecclesiastes 4:12