Which Rope Block Systems are SAFER for Single Strand Rappels?

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When we climb in the alpine a lot, we increase the probability of damaging our rope. No one is up there cleaning routes, removing the loose rocks and ensuring we don’t have sharp edges on critical terrain. So, we can get our rope dragging across less than ideal “knives” of rock, and we can have more rock fall potentially hitting our rope. Plus, depending upon season, we are much more likely to have the occasionally swung axe or ice tool, and if we are following on the route, the rope above us can inadvertently be hit by one of those swings.

In short, I talk fairly frequently about rope damage because it is a persistent risk in my typical climbing styles, much more so than during a day spent cragging.

The other thing about alpine climbing is that routes are much more likely to be multi-pitch, and often call for multiple rappels on descent. Combine those two probabilities, and we have the not-unreasonable potential of needing to do many rappels on a damaged rope. When we do damage our rope, we typically will isolate the damage with a bight knot. The damage is in the loop, so the strands of the rope going into and out of that knot are damage free and still reliable for holding our weight. That damage-isolating knot, however, is a hinderance to our rappels. It can’t go through the rappel device.

We may be left with needing to go through a quite time consuming procedure of moving our device from above the knot to below the knot. We did a video on that procedure.

… Or we could avoid rappelling around that damage-isolating knot if at least half our length of rope is in good condition. We can use that good half as a rappel line and the half that contains the damage as a pull strand. We create an anchor with a “block” that doesn’t allow the rope to pull through the rappel point when we pull on the rappel strand but does allow the rope to pull through when we tug on the pull strand. We then rappel down the one line and then, when everyone is at the bottom, tug on the other to retrieve our rope down to us.

But like with any rappel, we have the potential of our rope getting stuck when we try to pull it down. That can be a really scary thing, as we don’t know if the way that it’s stuck is severe enough to support our weight should we want to ascent that stuck rope so that we can unstick it. It might hold solidly under the weight of our tugs become become loose when we add our more hefty body weight and upward motion to it.

There are options to deal with this, such as using what rope we have managed to pull down as a lead rope to lead climb back up to where the rope is stuck. But there is no guarantee that the rope length we have at the bottom with us will be enough to reach wherever that rope is stuck. We could, at worse case, cut our rope, and use a shortened length for all of our future rappels. Now, though, are are building in more anchors as we make shorter rappels, and we have to worry about burning through gear as we build and leave behind anchors. We also have to worry about there even being good terrain features for building any anchors at all, given the odd distance our cut rope may allow us to rappel.

So, the combination of rope damage and rappel becomes an even greater hazard as the “rope blocking” techniques we can use to make a single-strand rappel also increase the likelihood of our rope getting stuck when we try to pull it down. We need to balance making our rope block effective with making is small so as to reduce the risk of the rope getting stuck.

That’s where these various techniques come in, and the point of the video. The likelihood of the rope getting stuck depends on the kind of terrain we are on. Slabby, lightly featured terrain poses much less risk of a stuck rope than blocky and crack-filled terrain. We might as well make bulkier, and less-likely-to-fail rope blocks for the former, but may need smaller, but mildly more-prone-to-failure blocks for the latter.

Given all of the above, getting to know our options could prove to be a valuable use of our time.