question 6mm strong enough for quad anchor/cord-a-lette?

[DPS]

I recently bought a 100 meter spool of 6mm cord because it was on sale and I leave so much of it as rappel anchors.

 

I have always considered 6mm to be too weak for quad anchor/cord-a-lette material, however, this manufacturer rates it at 9kn. For comparison, PMI 7mm is rated at 10.7 kn.

 

What is the cc.com's brain trust consensus on this, is 9kn strong enough for use as anchor material?

 

Also, 100 meters is more cord than I can use in the foreseeable future, so I am selling lengths of it at 0.34 cents a foot, what I paid. Great for rappel tat, prusik slings, tag lines (if you are into that kind of S&M) and perhaps even anchor material.

 

If you want to buy some 6mm cord, still in plastic on the spool, email me at Daniel-p-smith@hotmail.com

[dave schultz]

My current philosophy is:

 

7mm for rock terrain (ie real rock climbing, real falls possible)

 

6mm for alpine terrain where real falls are very unlikely; and ski terrain where the loads are significantly less than vertical.

 

Who made the 9kn 6mm?

 

I currently use 6.5mm dynamic prussik cord from bluewater in the alpine and on skis, but still use full 7mm for rock terrain.

 

For a dedicated quad, ie four total strands I would think the 6mm should be totally adequate, but would potentially limit you in application if you were in rock terrain and wanted to undo the quad.

 

I've also shifted to webbing for reinforcing or upgrading tat, though cord works if you don't have any webbing. For leaving cord, 6mm seems fairly limited on the time it will add value before it's just another POS that needs to be cut out.

[chris]

Yes, I think 9kn/2000lbs is adequate for rock and alpine anchors, so I use 6mm as well. I'd buy some off of you, but I got a spool of my own last fall.

[DPS]

 

Who made the 9kn 6mm?

Edelrid, here is what I bought: https://www.backcountry.com/edelrid-powerloc-expert-sp-accessory-cord-100m?CMP_SKU=ELR001K&MER=0406&skid=ELR001K-FIR-S6MM&mr:trackingCode=4530F522-2651-E711-8100-005056944E17&mr:referralID=NA&mr:device=c&mr:adType=plaonline&CMP_ID=PLA_GOc001&utm_source=Google&utm_medium=PLA&k_clickid=fe0ca984-ea2a-4883-9043-51b100033e50&gclid=Cj0KCQjw557NBRC9ARIsAHJvVVPvkYXTJzcBLNcBLN2w79vwPOR8NGWL5Ye6YIdEeEoYv-uns5Yh3FEaAvdeEALw_wcB

 

Edited August 31, 2017 by DPS

[DPS]

 

I've also shifted to webbing for reinforcing or upgrading tat, though cord works if you don't have any webbing. For leaving cord, 6mm seems fairly limited on the time it will add value before it's just another POS that needs to be cut out.

You may be correct. If I was civically minded like Chris or Kurt, I would use static caving rope inside 1" tubular webbing. A lot of the anchors I leave are not meant to last that long, for example V-threads, or are on obscure descent routes.

 

For some reason I have had the notion that cord is better than webbing. Maybe I read that some where. At any rate, I feel good and wholesome using 6mm for tat, it is a good balance of compactness in the pack, lightweight, and strong enough for the application.

 

Andy Kirkpatrick weighs in, and he mentions cord is better than webbing: https://andy-kirkpatrick.com/blog/view/life-at-retail?utm_content=buffer93c8e&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

 

Edited August 31, 2017 by DPS

[alps]

Out of curiosity, what is the rationale for preferring webbing over cord for reusable rappel anchors? I learned (coming from Europe) to use cord if possible. The reason being that in cord the sheath offers at least some UV protection for the actual load-bearing part, whereas in webbing the load-bearing structural material is directly exposed to UV radiation.

 

Are there other considerations that make you prefer webbing?

[dave schultz]

The worst is tape, which can look in good condition but one bad little patch, plus serious sun damage, and it just rips apart like paper. Cord is better, the sheath soaking up the rays, but even then, a 7mm strand of cordellete abandoned on a flake several years before you got there is a dice rolling anchor.

 

His opinion is not exactly scientific. I would argue that webbing is easier to judge the quality when compared to cord, making the decision to trust it or beef it up easier.

 

I thought I had read that webbing is more UV resistant than cord; though, in my quick google search, I can't find any real evidence toward either being any better against UV.

 

Some quick numbers:

 

6mm Edelrid 9 kN 2023 lbs 25 g/m 81 lb/g

6.5mm Bluewater 9.3 kN 2100 lbs 26.3 g/m 80 lb/g

7mm Bluewater 10.4 kN 2360 lbs 32.9 g/m 72 lb/g

1" Bluewater Webbing 17.7 kN 4000 lbs 40 g/m 100 lb/g

 

I find that cord makes a master point better than webbing, but this tends to focus the wear in a single area. This works best with larger diameter cord or rope. Redundancy is achieved with two loops around the tree, rock, etc; and this requires a longer length. Adding a length requires a double or triple fisherman, though you could maybe make a reasonable argument for using other knots.

 

Another way to add redundancy is to add two independent loops of webbing, which may be easier and likely uses less length than the cord with masterpoint strategy. The two loops of webbing also prevent isolated wear since the loops are able to rotate around and spread the wear.

 

Does accessory cord have a true core with a sheath? Looking at mine, it appears there is a core, but it is fairly small. Regardless, the strength of the webbing is an order of magnitude higher than the strength of the cord.

 

So, I use webbing because:

 

(1) it is significantly stronger.

(2) I am/was under the impression it was more UV resistant than cord, I'll do some more research to try and find the answer.

(3) I am able to easily remove a significant amount of the tat at an existing station (i.e. all the nasty shit), while leaving the one or two best lengths of cord or webbing, and simply add a loop of my own webbing (which is easier than cord) to improve the overall station and remove the excess trash.

(4) on a route where I think there is a possibility of needing to beef up a station, I will bring about 10 feet of webbing, which is sufficient to beef up at least one station. Anything beyond one station I will use my cordage and, if needed, my rope.

(5) on a route where I KNOW I will be adding an unknown number, but definitely multiple stations, I will bring 30-40 feet of webbing in a continuous length, which should give me plenty to add the required stations. The cord and rope are still options.

 

A lighter to clean the edges of the webbing is nice.

 

For v-threads, cordage is still king, and I use the cut off ends of a set of double ropes at 7.8mm. Cut to pre-measured length make for easy threads.

 

[DPS]

 

Does accessory cord have a true core with a sheath?

 

Yes, I pull the core out of 6mm and use the sheath for flat boot laces when the stock ones break.