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Accessory Cord for Rappel Anchors - What size?

Original Post
Prametheus · · Teton Valley · Joined May 2013 · Points: 55

Hey,

I just purchased some 5 mm cord (20 ft) with a rap ring for those times when the fixed anchor seems questionable. At the gear store, there was a posted sign stating this cord can hold over 700 lbs of weight and I just read on Mammut's website that it's breaking point is about 5.5 kN.

Note: this 5 mm cord is intended to be a rappel anchor only.

Just wanted to reach of to my fellow mtn proj'ers...would you feel ok rapping off of an anchor constructed with 5 mm accessory cord?

Thank you,

Max

FrankPS · · Atascadero, CA · Joined Nov 2009 · Points: 276

That's fine - just make sure there are no sharp edges, the horn or rock you're attaching it to is solid and your knot is good. I might feel better with a 6 mm, but 5 will be sufficient. If you're not comfortable with it, you could use two, separate 5 mm cords to rap off of.

My two cents.

Highlander · · Ouray, CO · Joined Apr 2008 · Points: 256

Unless you and your partner combined weigh close to 700lbs and don't shock load it, you should be fine. Also if the cord is doubled up, you will increase the total strength.

Eric Stern · · Seattle · Joined Jun 2014 · Points: 52

Keep in mind that others will use your anchor and age/weathering will weaken it over time. I like 7mm or 6mm.

Marc801 C · · Sandy, Utah · Joined Feb 2014 · Points: 65
Prametheus wrote:At the gear store, there was a posted sign stating this cord can hold over 700 lbs of weight and I just read on Mammut's website that it's breaking point is about 5.5 kN.
Even a 145lb lightweight can pretty easily bounce and exceed 700 lbs. 5mm is just too thin except for an emergency. Go with at least 6mm, preferable 7mm. Especially note that someone else might be using it, too.

If I came across an anchor made of 5mm tat, I'd cut out the 5mm and add my own slingage.
Thomas Beck · · Las Vegas, Nevada · Joined Feb 2006 · Points: 1,025

Prametheus,

IMO...For emergencies only right? I'd prefer doubling the cord if I could. You might consider a non loaded back up for the first person down.

A matter of personal style, but I sling my chalkbag on 5.5 cord and if I am going somewhere I think I might have to supplement the existing anchor or bail on a route I'll carry 6 1/2 ft of 11/16 black webbing. I use whichever is cheapest...rap ring or 5/16" screw links.

rgold · · Poughkeepsie, NY · Joined Feb 2008 · Points: 526

700 lbf is unacceptable. But the correct rating for Mammut 5 mil is 5.5 kN, which is about 1200 lbf. Taking into account the strength reduction from the knot, 1200 lbf is about what you can expect from a loop; a doubled loop will usually give about 2400 lbf.

I'd consider a single loop for desperate emergency situations in which you need every last bit of cord, otherwise I wouldn't go with less than a double loop.

Still, 5 mil cord wears, weathers, and cuts easily, so, single or double, should only be for emergency retreats. If you are setting up rappels that you expect others will use as well, I'd say double 7 mil (the standard for cordelettes) is the minimum.

In the Gunks, for tree anchors I think will be reused and might be top-roped off, I install two independently-tied strands of retired (but not in any way damaged) 8.5mm half rope.

Prametheus · · Teton Valley · Joined May 2013 · Points: 55

Thank you all! I guess I'll find an alternate use for this cord and get some 7 mm. Just read a post about an anchor on Monster Tower failing. If the anchor is ever questionable...lets do something about it!!!!

Brendan Maguire · · Manassas, VA · Joined Aug 2014 · Points: 5

Also keep in mind that you won't be rapping off of a single strand of cord and depending on how you set up your anchors it will hold 3 or 4 times more than that. I prefer to use 6 or 7 mm for anchors whether it is for extending a top rope anchor off of a tree or anchoring off of rings.

Brendan Maguire · · Manassas, VA · Joined Aug 2014 · Points: 5

Also keep in mind that you won't be rapping off of a single strand of cord and depending on how you set up your anchors it will hold 3 or 4 times more than that. I prefer to use 6 or 7 mm for anchors whether it is for extending a top rope anchor off of a tree or anchoring off of rings.

djh860 · · Unknown Hometown · Joined Dec 2014 · Points: 110

Why not maxim tech cord or webbing?

r m · · Unknown Hometown · Joined Apr 2015 · Points: 0
andy-kirkpatrick.com/articl…

Read the rest of the article so you can be assured that nothing has been taken out of context, but here's a sentence from the opening paragraph:
...In my opinion the best material for abseil anchors is 5mm accessory cord...
Tyler Thompson · · Estes Park, CO · Joined Jan 2012 · Points: 15

IMO an emergency should never justify using sketchier gear anyway. That's when you need things to be extra bomber. If you're planning for emergency situations ahead of time, plan beefy.

r m · · Unknown Hometown · Joined Apr 2015 · Points: 0
Tyler Thompson wrote:IMO an emergency should never justify using sketchier gear anyway. That's when you need things to be extra bomber. If you're planning for emergency situations ahead of time, plan beefy.
I disagree, mostly owing to weight and space constraints, but also because I think in emergencies the acceptance of level of risk for many things can be increased.

Simple case regarding the weight:

7mm cord is ~2x heavier than 5mm cord, ergo for the same weight you could carry twice as much 5mm. Which would you rather for an unpredicted 2 man emergency situation? Keeping in mind its a pretty simple operation to double up 5mm.

The heavier gear is, the less likely you are to pack it and the less of it you can take when you do pack it.

As for the sketchier gear (higher acceptable level of risk), whilst in normal climbing you might never want to rap off that crap anchor, but maybe someone dropped the rack and there's a storm brewing and if you're not down soon you may not be coming down at all.
There's all sorts of situations where taking an increased risk in one specific aspect reduces the overall risk.

Now if you're planning for emergencies in the context of being on a rescue team, that's a very different situation.
Tyler Thompson · · Estes Park, CO · Joined Jan 2012 · Points: 15

I suppose I tend to be on the more conservative side of things. Although, unless I'm in the alpine or very unsure of the route, I rarely care spare webbing/cordelette just for emergencies. In a true emergency you can always use your anchor cordelette or chop your rope. I carry 6mm cord. There is definitely a large grey area here, as with everything in climbing.

jackieliu · · Unknown Hometown · Joined Jul 2015 · Points: 0

If you have a Gopro camera, that must be fun! Looking some accessories for that!

Guideline #1: Don't be a jerk.

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