DMM (a UK gear company) recently shared some drop testing done on a collection of Dyneema slings. The results have created a lot of new discussion in the blog-o-spere and on the forum circuit. But is this really breaking news?
Dyneema and Spectra are synthetic fibers that have a much higher strength-weight ratio than typical nylon, and they have become the "top shelf" material to build light and fast fabric. Really applicable for backpacks and...climbing slings. But here's the rub: these fibers also are a lot less able to stretch than their nylon equivalents. And that ability to stretch is what allows our safety system to absorb much of the force that is generated in a fall. So if you were to take a 2 meter fall in a dynamic system, where much of the force generated is transfered into the stretch of some of the materials, then the end result is you healthy and whole. That same fall in a static system will have no absorbtion of the forces generated, causing the force to break equipment and the climber, sometimes both with catastrophic consequences.
DMM's video of their tests can be viewed here.
And a short article about it, with the same test results can be read here.
Does this mean that Dyneema has become more dangerous? Hardly. This is simply one more piece of data that only adds to a body of work collected over the last couple of years. Dyneema is less static, less durable, less heavy, and less bulky. That doesn't mean its innappropriate for its application. What is does mean is that more responsibility is on the climber to think about what they're doing, and rely less upon the "recipe" taught to them by their climbing club, gym, or best friend.
What is shows is what we all know - that the rope is the single best and biggest piece of equipment in the system. A dynamic rope absorbs the lion's share of impact forces in any scenario, making it the key piece in any factor 2, 1, or 0.1 fall. That's why carabiners and slings are required by CE to meet 22kN, but protection is not. And this re-inforces my personal opinion that using the rope to tie into the anchor is not only the most efficient method, but also the safest.
On other plus sides, if you carry your shoulder-length slings tripled up, as I do, then you'll quickly discover that Dyneema slings outperform Nylon slings in the bulk category by 3:1. I typically carry 8-12 shoulder-length slings on any gear route, and two more double-length slings on alpine routes. If I'm cragging or day-tripping, I'll often replace those two double-length Dyneema slings with Nylon equivalents, because I think they're more likely to run over edges at anchors or be used for personal anchors during rappels.
On other negative sides, Dyneema slings appear to be more susceptible to UV radiation, aka sunlight, becoming brittle and loosing strength at a much higher rate than nylon. In animated objects this is called aging - it happens to everything. So if all things are equal, then Dyneema slings need to be replaced more often than their nylon counterparts. Following the example of an AMGA Examiner and mentor, I replace mine annually out of prudence.
And finally, this isn't an absolute. All Dyneema slings are actaully a nylon/dyneema weave, since Dyneema can't be colored. So every manufacturer has a different blend combination, resulting in wider and narrower material. Don't like the ultra-skinny Mammut slings? Then go for the uber-wide Metolius (this is relative, they're still narrower than nylon) or the middle-of-the-road Black Diamond - my personal choice.