Sterling Evolution Duetto 9.4 Half Ropes

Belaying and Rappelling

Last weekend I pulled them out of the closet for a similar three-person team trip up Castleton Tower in Utah. True, you can rap down the Kor-Ingalls, but that sounds horrible and a much weaker option than doing two full-length raps down the north face. Once again, the Duettos were easy to use. Because of the thin diameter, they pulled through my belay device with very little resistance. I was using an ATC-Guide in guide mode, and the ropes pulled through so easily that at the top of the third pitch that I was able to set up a quick anchor, extend my tie-in point two about eight feet, and belay from the far side of the ledge where I could see my followers climbing.

Sterling Evolution Duetto, Blister Gear Review
Dave Alie, Castleton, Utah.

Rapping off the tower was the first time I had done a vertical rappel with the doubles and, with the weight of a pack on, they fed so quickly through my belay device that I had to work to keep the rappel at a reasonable speed. Some sort of autoblock backup when rappelling is always recommended, but the thin nature of the Duettos places a real premium on their use.

The lightning-fast action of the Duettos was noticeable during belay sessions as well. I remember listening to a conversation about how much rope slips through belay devices when belaying from above or below and thinking to myself, “Is this really an issue? I can’t remember my rope slipping at all.” Then I used half ropes for the first time. Holding a climber who is sitting on the rope is more work with halves than with singles, and the Duettos even more than many halves: they felt faster through a device than the Mammut genesis doubles I had used in the past.

Catching Falls

While out in the desert, I also had the pleasure of whipping onto one of the ropes. (Why review a rope you haven’t really tested, right?) I did feel a bit silly breaking out a double rope for splitters at Indian Creek, maybe the last place on Earth you’d need double ropes, but we had brought them so why not use them? Falling on the Duetto is where you really notice that you’re climbing on a double. The Duettos are listed on Sterling’s website as having 31.6% dynamic elongation. While hardly an outlier for this metric, the ropes felt like they stretched more than previous double ropes I’d used and, without question, significantly more than a single rope would. The soft catch is nice, for sure, but it’s important to be aware of the slightly longer fall when climbing above ledges or other obstacles.

Over the course of these uses, I occasionally had to un-kink the ropes, and the thinner diameter means they’ll tangle up in one another when pooling both ropes at a belay. The kink factor of the ropes, however, is not outside of what should be expected from most ropes. While we’re on this point, I think I should show my hand and describe part of my philosophy on ropes.



A quick follow-up on dynamic elongation: dynamic ropes are often listed with statistics such as elongation at first drop, the number of falls a rope is certified for, etc. The dynamic elongation of many ropes is listed as being in the high twenties or low thirties, implying that the degree of stretch is similar as well. This is not really in line with what we observe: obviously a Duetto half rope is going to stretch noticeable more than a 9.8mm single rope. The discrepancy, as best I understand it, is that the dynamic elongation figure is recorded using the standard UIAA drop-test conditions: 80kg weight dropped onto a rope with a fall factor of 1.71. Because this generates much higher forces than seen in the vast majority of climbing situations, you’re real-life experience with the rope is unlikely to generate that much stretch. If we think of that value as being close to a rope’s maximum ability to stretch, then the extra stretch experienced with a half/double rope is due to the fact that the skinnier rope requires slightly less force to achieve that maximum elongation than does a thicker rope.

For the sake of completeness, I feel compelled to mention that the Duettos are rated by the UIAA for 6 falls. I take issue with this as a metric for anything of value about a rope, but it is the industry standard. Generally speaking, the falls are recorded in succession using the conditions mentioned in the above paragraph until the rope fails. Because those conditions are uncommon, to say the least, it is a poor standard for the lifetime of a rope. But for those interested in fall-rating comparison, there you have it.


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