splitter climbing gear

Should I use Nylon or Spectra (Dyneema) Slings?

Should my cordelette be made from Spectra or Nylon??

This question got asked (and answered) in Issue 155  of Rock & Ice on pages 88-89. First, as our website stresses, this article points out that a cordelette is not the best option for building anchors, especially when equalization has any importance what-so-ever. Check out our article on building anchors for more on this issues. Let’s not get off task, the purpose of this article is to learn what we should be using for our cordelette. This article points out that a cordelette made of 7mm nylon is the best choice. The nylon will stretch when it’s loaded, acting as a shock absorber and reducing the peak impact force on the anchor. The stretchy nylon will also help the anchor to equalize better, and as we now know, your chances of equalizing an anchor with a cordelette is as good as your chance to hit the lottery. So, the stretch in the nylon is important. Also, never clip into the anchor with a Spectra sling or daisy chain. If you’re fussing around at the anchor and you fall directly onto your static (Spectra) sling, you can generate loads large enough to break gear or blow placements. For more on this continue reading...

On Tom Moyer’s testing website:

http://www.xmission.com/~tmoyer/testing/

there is a paper titled “Comparative Testing of High Strength Cord,” by Tom Moyer and two Black Diamond employees (Paul Tusting and Chris Harmston), which discusses the differences between nylon cord and high strength cords or slings made from different blends of Spectra, Nylon, Kevlar, and other materials. Through all of the tests that they conducted for this paper, they concluded that nylon cord (typically 7mm) is the best choice for use as a cordelette or an equalette. Check out the website listed above for the whole paper.   

How dangerous is it to fall directly onto a spectra sling or spectra daisy chain?

This is extremely dangerous! If you clip directly into your anchor with a sling or daisy chain and fall, the fall factor will be extremely high with a good chance of being a factor 2 fall. This can generate extremely large peak forces that will shock load your anchor. In Rock & Ice issue 137 (pages 104-109) they examined the seriousness of a fall onto a sling or daisy chain. First, they looked at a 24 inch fall onto a 12 inch quick draw with a live (human) load. These falls created peak forces of 1600 pounds force. After this, all of the tests were conducted with a 165 pound weight. Next they tested a 44 inch fall onto a 22 inch spectra runner. The runners tested were rated at about 5000 pounds and in the tests the runners broke! Then they tested the same fall onto a nylon sling instead of a spectra runner and though the falls produced peak loads of over 2 tons, the nylon slings did not break. Lastly, they tested 54 inch daisy chains. They clipped the daisy chains into the middle pocket and into a pocket a third of the way down the daisy chain. These falls resulted in loads that peaked at 2200 pounds force. The initial static fall caused pockets in the daisy chain to blow out. The result of the pockets blowing out was a dynamically slowed fall which was eventually caught by the daisy chain after a few pockets blew out. Finally, they took the daisy and clipped it into the ends and dropped it the full length of the daisy. They did this test twice and both times it broke the daisy chain into 2 clean pieces.

The spectra runners are in general stronger than the nylon ones. The reason that they were able to break them in these tests is because there was nothing dynamic in the system to slow the fall. Instead, the rate of deceleration was extremely quick which, in turn, broke these otherwise strong slings. The nylon runners stretched when they were fallen on, which resulted in a slower rate of deceleration and in turn lower peak forces that did not break the nylon. When the climbing rope is clipped through these spectra runners, the climbing rope will stretch and dynamically slow the fall. This type of fall will not create peak loads that are capable of breaking the spectra runners.

We can take a lot away from these studies. Most important, the climbing rope should always be the primary connection to an anchor. If you tie into the anchor with your climbing rope, then you’ll never be able to truly ‘shock load’ the anchor. Clipping into your anchor with a static connection, such as a spectra sling, is dangerous and can shock load the anchor. If you clip in with a static connection and then climb above the anchor and fall, it can truly shock load the anchor, and create peak forces that are large enough to blow out a solid anchor.

Todd McCormick, of Splitter Gear, did testing to confirm the risks of tying into your anchor with a daisy chain versus tying in with a piece of your dynamic climbing rope. The test results...

DAISY CHAIN FALLS

Climber Weight: 150 lbs.

Length of daisy chain: 50 in.

Length of falls: slightly less than 50 in.

Fall Factor: Slightly less than factor 1 (greater than .9)

Forces generated: always more than 5kN, never more than 6kN.

DYNAMIC ROPE FALLS (9.4mm)

Climber Weight: 150 lbs.

Amount of rope in the system: between 35 and 40 in.

Length of falls: between 32 and 38 in.

Fall Factor: slightly less than factor 1 (greater than .9)

Forces generated: always more than 2kN, never more than 3kN.

These are significant results. The daisy chain falls averaged approximately double the force of the dynamic rope falls. In the worst case scenario, a factor 2 fall, if you’re tied into your anchor with a static connection point (like your daisy chain), you could easily be generating enough force to blow out your anchor. Especially if your anchor isn’t purely equalized.