Mark Smiley and the Black Diamond QC lab are well known tinkerers. Smiley often presents gear mods (both soft and hard goods) via social media, whereas BD has conducted lab tests on topics like the risks of twisted ropes or the strength of certain ice screw placements.
The QC Lab’s Matt Berry and Smiley, to use some modern parlance, had a recent collab of note. The two paired up to gather data and make some conclusions regarding snow anchors titled “The Art and Science of Using Snow Anchors.” Yes, a melding of art and science that relates to readers of The High Route.
The QC Lab’s research piggybacks on some well cited prior research. Google a few iterations of search terms involving snow anchors, and two resources routinely populate the results. (They are also linked in the QC Lab piece.) The first is a 2010 paper titled “Snow Anchors for Belaying and Rescue.” Summarizing the 2010 research, the paper’s authors write this about effective snow anchors: “The three key things are to increase snow strength, get anchors deep, and pull from the middle.” The folks conducting this research examined such factors as snow strength, anchor material/shape qualities, and anchor placement.
The second resource often cited is a video by the Ecole Nationale de Ski et d’Alpinisme (ENSA) in France. The video is short and provides some basic takeaways. For example, placing a small snow stake at 25-degrees to the snow surface (the perpendicular) was ~40-50% stronger than the same anchor placed perpendicular to the snow surface.
Back to Smiley and the QC Lab. Smiley, an IFMGA guide, presents a three-step process for building snow anchors. First, create a stout anchor. Second, bounce test the anchor (with a backup in place). Third, rappel smoothly.
The presented data enhances our understanding of each step in the process (build/bounce test/rappel).
A snow anchor test highlights the anchor type, orientation, peak load, and whether the anchor failed. (Yes, there are results for building an anchor from a Snicker’s bar.)
Screengrab: BD QC Lab
Bounce tests are simulated in the lab. We get a sense of the forces generated when bounce testing with different connecting setups and the associated body weight multiplier. (They tested the following different connections to the anchor between: a Dyneema sling, a nylon sling, an 8.5mm single strand dynamic rope with ATC-Guide, and a 9mm single strand static rope with ATC-Guide)
Screengrab: BD QC Lab
Smiley writes, “The data we collected challenged my previous assumption that bounce testing with a UHMWPE sling tether applies MASSIVE forces to the anchor. It really doesn’t. One must really wail on the anchor to generate more force than can be potentially generated during a long herky-jerky rappel. Using a UHMWPE sling, however, does generate much higher loads than bounce testing when rigged for rappel with a rope and ATC.”
The last set of information relates to forces generated while rappelling. The team raps on a single strand 8mm Dynamic or 9mm static rope, and their rappel technique is varied by degrees of “aggressiveness,” from delicately, realistic, moderate, and aggressive.
Screengrab: BD QC Lab
The data are clear: rappel smoothly, as “aggressive” rappelling is a bodyweight multiplier. Smiley and Berry point out that smooth rappelling vastly reduces the load on the anchor compared to more aggressive rappelling. Smooth rappelling ensures you do not come close to generating the higher forces yielded during a bounce test, allowing for a greater safety margin. We don’t rappel smoothly all the time—thus, conducting a vigorous bounce test before committing to the anchor is crucial.
To guarantee the bounce test is vigorous and reliable, Smiley and Berry recommend using UHMWPE/Dyneema slings when bounce testing, as they help generate a higher force on the anchor.
Smiley and Berry provide helpful information. And they have several other takeaways. We encourage folks to read the full BD QC Lab’s findings to learn more.