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r0cker
Jul 17, 2008, 11:19 AM
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In the past I've just used webbing to set up anchors and now I'm looking at using Cordelettes for obvious reasons. What size Cordelette or strength do I need to get to be legit with anchors?
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moose_droppings
Jul 17, 2008, 11:57 AM
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r0cker wrote: In the past I've just used webbing to set up anchors and now I'm looking at using Cordelettes for obvious reasons. What size Cordelette or strength do I need to get to be legit with anchors?
7mm perlon cord should do ya fine. Its single strand strength is around 3000lbs.
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rob6118
Jul 17, 2008, 2:39 PM
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I'll put my .02 cents, but my opinion is not set in stone so feel free to debate it. I just finished John Lang's Climbing Anchor book and was impressed with his equalette concept. This will be my default anchor for both TR and trad placements.
When I got my static rope in the mail bluewater included some 5mm cord that is rated at 1250 lbs. Now as I understand it this is perfectly fine for using it as an equalette. In order to tie it, I tie the 20' cord in a loop with double fishermans, then I double the loop. If you are familiar with the equalette you then do two overhand knots to limit extension about 3-5" on either side of the half way mark.
This results in 4 strands to each anchor (2), and four strands between the two overhand knots with an equalette that is approximately 2.5' long on either leg to the anchor.
1250lbs x 4 is 5000 lbs. I believe the conversion factor is 244, so this means that each leg to an anchor is 20.50kN. The section between the two overhand extension knots is where the biner is placed on three of the four strands. That means that section is rated at 15.37kN.
Therefore most parts of this equalette are rated for only a little less then the biners themselves. Even accounting for 10-15% knot weakness the strength is well over the 10-12kN force maximum in climbing falls stated within the book.
The consensus on the board using the search factor is that everyone uses 7mm cord. But given the same anchor setup (without doubling the loop since the 7mm is stronger) would yield you similiar strength, but only one strand of cord holding the biner.
So me personally using my preferred equalette setup I would say 5mm nylon is fine after doing the math. It is even preferred since its more redundant after doubling the loop. It is also cheaper, and not necessarily bulkier.
But then again by carrying 5mm only I cannot do sliding x's or simple cordelettes w/o doubling the strand. But then again I have slings for sliding x's....
So just my opinion, and I'd be curious to hear any opposing thoughts but after doing the math I'm pretty sure 15kN with 3x redundancy is a pretty good safety factor.
Rob
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coolcat83
Jul 17, 2008, 2:55 PM
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rob6118 wrote: I'll put my .02 cents, but my opinion is not set in stone so feel free to debate it. I just finished John Lang's Climbing Anchor book and was impressed with his equalette concept. This will be my default anchor for both TR and trad placements. When I got my static rope in the mail bluewater included some 5mm cord that is rated at 1250 lbs. Now as I understand it this is perfectly fine for using it as an equalette. In order to tie it, I tie the 20' cord in a loop with double fishermans, then I double the loop. If you are familiar with the equalette you then do two overhand knots to limit extension about 3-5" on either side of the half way mark. This results in 4 strands to each anchor (2), and four strands between the two overhand knots with an equalette that is approximately 2.5' long on either leg to the anchor. 1250lbs x 4 is 5000 lbs. I believe the conversion factor is 244, so this means that each leg to an anchor is 20.50kN. The section between the two overhand extension knots is where the biner is placed on three of the four strands. That means that section is rated at 15.37kN. Therefore most parts of this equalette are rated for only a little less then the biners themselves. Even accounting for 10-15% knot weakness the strength is well over the 10-12kN force maximum in climbing falls stated within the book. The consensus on the board using the search factor is that everyone uses 7mm cord. But given the same anchor setup (without doubling the loop since the 7mm is stronger) would yield you similiar strength, but only one strand of cord holding the biner. So me personally using my preferred equalette setup I would say 5mm nylon is fine after doing the math. It is even preferred since its more redundant after doubling the loop. It is also cheaper, and not necessarily bulkier. But then again by carrying 5mm only I cannot do sliding x's or simple cordelettes w/o doubling the strand. But then again I have slings for sliding x's.... So just my opinion, and I'd be curious to hear any opposing thoughts but after doing the math I'm pretty sure 15kN with 3x redundancy is a pretty good safety factor. Rob
there is 5mm that could be used, but that is titan, technora, tech cord, kevlar(which i have not seen in a long time) theses are usually a blend if high tech polymers like spectra/nylon/dyneema. the benefit is it's smaller and lighter but you loose the dynamic properties of all nylon. the 5mm that they sent if just nylon and that strength is not meant for a cordolette. for starters why use something weaker? it's less resistant to cutting and abrasion. if you really want something smaller go with some tech cord or something similar, 5mm is ok for prussics on smaller ropes and glacier travel. but why not include that measure of safety?
especially if oyu are starting out go with the standard (giver you more margin of error), you can fuss with the other stuff later when you learn more. the equalette has its place, but the cordolette has its as well, along with many other ways to construc an anchor. do some more research, try things out safely on the ground, you'll see that even with and equalette there's not perfect equalization and you wouldn't want to load one placement on one strand of a tiny cord. and think about what happens if your placement pops.
just my 2c
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rob6118
Jul 17, 2008, 3:10 PM
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coolcat83 wrote: there is 5mm that could be used, but that is titan, technora, tech cord, kevlar(which i have not seen in a long time) theses are usually a blend if high tech polymers like spectra/nylon/dyneema. the benefit is it's smaller and lighter but you loose the dynamic properties of all nylon. the 5mm that they sent if just nylon and that strength is not meant for a cordolette. for starters why use something weaker? it's less resistant to cutting and abrasion. if you really want something smaller go with some tech cord or something similar, 5mm is ok for prussics on smaller ropes and glacier travel. but why not include that measure of safety? especially if oyu are starting out go with the standard (giver you more margin of error), you can fuss with the other stuff later when you learn more. the equalette has its place, but the cordolette has its as well, along with many other ways to construc an anchor. do some more research, try things out safely on the ground, you'll see that even with and equalette there's not perfect equalization and you wouldn't want to load one placement on one strand of a tiny cord. and think about what happens if your placement pops. just my 2c
Why use something weaker > redunancy w/o overkill on strength.
Not strong enough? See above calc on 15kN strength.
Equalization? See Long's discussion on equalization of cordelette. Equalization occurs when there is no angle between the strands and no length differential. Both are the case in the equalette.
Why not use stronger stuff? Same reason why I haven't seen any 40kN biners. As per Long's book 10-12 kN is the max force seen in dynamic climbing falls. Not the 20kN seen in the static lab tests.
The biggest flaw I can see in the equalette, esp. with the weaker cord is if one piece of pro pops. In my case above the biner would be resting on one of the overhand extension knots with 3strands on one side, and 1 strand on the other. But there is no way for the biner to apply stress to that 1 strand. All of the weight would still be on the three strands (prob helps to have the equalette in front of you). The single strand just keeps the biner from slipping over the knot. The only way the weight could be placed on the single strand is if the entire leg that popped fed through the biner.
Is this unlikely scenario enough not to use the equalette method with the 5mm cord? Obviously I wouldn't keep climbing in that scenario until I replaced the protection to ensure that the single strand did not become loaded.
Last question...where would you use a cordellette instead of an equalette. I read the book several times and must admit I couldn't see as situation where I would. I could see doing a sliding x when simplicity was more desirable then strength, but as a new climber I think I'll place more value on the strength.
Rob
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adatesman
Jul 17, 2008, 3:38 PM
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rob6118
Jul 17, 2008, 3:50 PM
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How's that for mad drawing skills???? And where is it a single strand?? The two filled in circles are the overhand knots.
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clc
Jul 17, 2008, 3:55 PM
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i use 8mm cord, 5.5 meters long
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moose_droppings
Jul 17, 2008, 4:09 PM
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rob6118 wrote: How's that for mad drawing skills???? And where is it a single strand?? The two filled in circles are the overhand knots.
Your drawing shows four loops, which it is not. A cordelette equalette has two loops, each loop has two legs of single strand.
That said, the cordelette equalette if (and a big if) it was set up so all four legs (many times its used with only 3) were equal in length and weight bearing, your calcs would be somewhat correct. Should your PP swing just a little to one side or the other, you are now only weighting two strands. If one of the legs on one side of the 2 legs were to give, your load would drop to the one backup leg on that side, granted shock loading isn't much of an issue. So why go dangerously close to failure point by going with a 5mm when the cost of 7mm is negilable.
Edytid for spelin.
Another edit: isn't it called the equalette? I'm not much of one of its followers.
(This post was edited by moose_droppings on Jul 17, 2008, 4:35 PM)
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rob6118
Jul 17, 2008, 4:22 PM
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Seriously guys, is it really that hard to understand (granted via the internet) that I already conceded the point that w/ 5mm I would not tie a single stranded cordellette. It is really to hard to understand the drawing where I intentional doubled the loop to get around this issue.
Is it also hard to understand that the equalization is why I stated I prefer the equalette over the cordellette. The equalette allows you PP to move the length between the two extension knots before loading just one of the anchors.
I apologize to the OP for drifting the thread. I thought the majority of people on the board had read the book I referenced and would easily understand the concepts involved.
Didn't realize I would get stuck arguing whether the anchor has single loops or double loops, or whether an equalette equalizes!
FYI I got my 5mm cord for 24 cents a foot, vs 42-45 cents a foot for 7mm. 50% increase in cost is significant. I even considered that I would have to double the length of the 5mm cord to have the equivalent strength of 7mm in the same anchor, at which point the 7mm cord would be cheaper. But the anchor would not be as redundant as the setup I described with the 5mm. I'd rather spend the extra money, buy double the 5mm, and double loops to get extra redundancy, and the same strength. Redundancy negating abrasion concerns associated with the smaller cordage.
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spikeddem
Jul 17, 2008, 4:25 PM
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adatesman wrote: Did you miss the part with the equalette where you take one of the loops and clove/overhand loop to two pieces? ....which then makes that leg just a single strand? Might want to re-run your calculations taking that into account.
Agreed.
Also, to the person originally posting about the equalette, I agree it is a good method, but it seems you skipped the part in the back with the studies done on it? It's not what you described.
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ryanb
Jul 17, 2008, 4:31 PM
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I've moved away from the cordelette recently in favor of the climbing rope but I did a long alpine free route with predominately hanging gear belays sunday and my partner, a former guide, brought two skinny cordelette's which worked great to reduce the cluster fuck at belays. Yesterday, to kill time at work, I was doing some research/calculations about how skinny you could go. Found this site:
http://www.caves.org/.../49/cthsc/cthsc.html
Summery: 7mm nylon cord rated for ~11 kn does not weaken with flex cycle testing and has strength reduced only %8 at knot. Ends up with a cordelette strength around 22 kn (for each leg). High strength cords weaken tons with knots and flexing and end up with lower cordelette strengths as low as 11 kn for sterling vectran which i believe is no longer sold.
So 7mm is more than sufficient and we can interpolate some of the newer 6mm nylon (mammut pro cord fro example) rated as high as 7.8 kn will have a ultimate strength in cordelette formation of 14-16kn per leg which is about what most of my pro is rated for.
This is consistent with the AMGA's recommendation (http://www.amga.com/.../gearlist_alpine.php):
"Cordelettes — Bring 2 or 3. Cordelettes are 5–6 meters of 6mm or 7mm pure nylon cord. Tech cords are not as helpful for rescue work and hitches."
Thoughts? IS 6 mm nylon to skinny for a cordelette? 7 mm is definitely best for TR etc when weight and bulk matter less.
(This post was edited by ryanb on Jul 17, 2008, 4:32 PM)
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acorneau
Jul 17, 2008, 5:35 PM
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rob6118 wrote: In order to tie it, I tie the 20' cord in a loop with double fishermans, then I double the loop. If you are familiar with the equalette you then do two overhand knots to limit extension about 3-5" on either side of the half way mark.
Hey Rob,
If you read your John Long book again, I believe he calls this doubled-loop equalette "the Quad" since it gives you four strands in the center instead of just two for the standard equalette.
If you're only making Quads then your 5mm cord should be just fine. Just understand that it would be considered by most folks to be insufficient for a standard equalette.
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rob6118
Jul 17, 2008, 5:40 PM
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Thanks Allen, I didn't have the book handy at work so I forgot that the doubled equalette is phrased as a quad.
Clearly only one loop of 1250 lbs cord is not suffecient. If you count each strand that is barely 10kN of strength per anchor leg before you consider the knot and only one strand where the biner connects so only 5kN of strength for the whole anchor. Clearly not sufficient.
But I thought the pic made it clear that I was referring to a quad / a doubled equalette not a single loop cordellete, sliding x, or equalette.
Rob
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858jason
Jul 17, 2008, 6:08 PM
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rob6118 wrote: Thanks Allen, I didn't have the book handy at work so I forgot that the doubled equalette is phrased as a quad.
I believe Long still recommends 7 mm nylon for the quadlette. I was previously using 5 mm, but recently reread that section and he recommends 5 mm tech cord or 7 mm nylon (p. 199). He also only recommends it for sport routes where the bolt anchors are in a horizontal line. You mentioned using it for trad anchors. The 2.5 foot arms in general won't give you enough range for a gear anchor where pieces may be some distance apart.
I like the equalette as well, but explain to your partners about it first so they don't remove the overhand knots when breaking down an anchor.
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rob6118
Jul 17, 2008, 6:20 PM
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Agreed on all points....
Haven't done any trad yet though so I'm interested in oddball protection placement and resulting anchor design. Obviously you can always make it bigger (40' loop instead of 20').
On unequal placement I don't see how a cordellette is superior to an equalette. If it were me I would prob just use a trad draw or sling to equalize the two tie in points for the quad.
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bozeclimb
Jul 17, 2008, 6:43 PM
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I use 5.5 mil tech cord for my quad. It is a little more compact than 7 mil and it works great for top ropes or fixed two-point anchors on trad/sport routes. I will also report that I have found the equalette much easier to set when I don't pre-tie the two overhand knots. Using a standard cordalette, I normally tie into the two most closely spaced pieces with clove hitches first. It it then pretty easy to tell where to tie the overhand knots and then clip the final piece (no hitch). It is easy to shorten by just having more slack between the first two pieces. This is quick, simple, and offers a degree of equalization that the standard cordellete does not.
Cheers
(This post was edited by bozeclimb on Jul 17, 2008, 6:44 PM)
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vegastradguy
Jul 19, 2008, 3:21 AM
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i use 6mm pro-cord from mammut. stronger than standard perlon by a bit, although not as strong as 7mm. i forget the specs, but its strong enough.
5mm is too thin, imho, no matter how you double it/equalize it up, one strand is going to get loaded more than the others.
that said, although i do own the pro-cord, i purchased it exclusively for the rock instructor course (amga). it has since lived in the cordage bag in the gear room. i rarely use it any more, i generally just use the rope these days.
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majid_sabet
Jul 19, 2008, 5:21 AM
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That book is the most stupidest thing a climber could read cause all it does makes noobs more confused to seek help in RC.
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the_bruce
Jul 19, 2008, 6:49 AM
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Check out Tom Moyer's article titled Comparative Testing of High Strength Cord at http://www.xmission.com/...gh_Strength_Cord.pdf.
In the end I ended up ordering a spool of Sterling 7mm nylon cord for my cordelettes. The reasons were:
* Very strong
* Keeps strength when knotted
* Holds knots well
* Did not fail in cordelette drop tests
* No loss of strength over flex tests
* Inexpensive
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umeroz7
Jul 19, 2008, 1:04 PM
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no math here but i just used my 5.5 maxim cord to pull my truck out of a ditch. i got a new one the next day but it was worth seeing the ladies face when i tied a "shoe string" to her tow hitch
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