Monthly Archives: July 2013

A is for Angle

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Anchor angle is too wide

The angle is far too wide.

As you likely already know, the ‘A’ in the rock climbing anchor building mnemonic acronym ‘EARNEST’ is for “Angle”. The angle between the legs of your anchor shouldn’t be too wide, right? Certainly less than 90°, and ideally less than 45°. The angle formed by the outer legs of the anchor in the photo above are too wide. This is a bolted three point anchor, so it’s not likely to fail. But it’s odd that the bolt on the right is so far off from the two on the left. I mean who bolts a route to make this scenario likely? This anchor could be improved simply by using longer cord and extending the power point closer to the edge of the cliff. The further away the power point is from the bolts, the smaller the angle becomes.

Location: Unknown.

Why does the angle matter? Intuitively, it makes sense that regardless of the angle created in constructing a two point climbing anchor, each of the two anchor points will carry half (50%) of the load. But this isn’t true. The wider the angle, the greater the load each anchor point has to bear.

Take a look at this graphic from the AMGA Manual. You have to create a narrow 20° angle between the anchor points to have them each bear 50% of the load. At 45° the weight distribution only increases to 54%, at 80° it’s 70%, and by 120° each anchor point is bearing 100% of the load! If you really want to geek out on the physics involved, check out this trigonomic analysis of tension in climbing anchors.

Climbing anchors angle

Relative weight distribution on a climbing anchor determined by angle

The Trouble with Quickdraws

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Improperly assembled sport climbing quickdraw

Improperly assembled sport climbing quickdraw

If you’re an avid rock climber you’ve probably already heard about the tragic, untimely, and completely unnecessary death on July 5th of 12-year-old Italian climbing phenom Tito Traversa at the French crag Orpierre. Apparently while being lowered off of a 5.10b eight of the 12 quickdraws he’d used to protect the route failed, causing him to deck after a fall of some 25 meters. The police photo above, published in the French climbing magazine Grimper, reveals what speculation has suggested up to now: the quickdraws, which were provided by someone on he gym team he was travelling with, were improperly assembled. The tiny bit of elastic, which is designed to keep the carabiner in an upright position at the end of the dogbone for easy clipping, was used as the sole attachment point between the carabiner and the nylon/dyneema dogbone itself. You can see similar coverage in English from Climbing magazine.

Unless you’re mindful to carefully inspect your quickdraws before you climb, this assembly error isn’t readily apparent until the quickdraw is actually weighted (in which case it’s too late). However, assuming you use your own quickdraws, which you’ve assembled yourself and probably used many times in the past, it’s highly unlikely that you’ll encounter this assembly error. So maybe this is a cautionary tale for those rare times you borrow someone else’s quickdraws, right? Perhaps. But in this video from UKClimbing, climbing gear designer Streaky Desroy shows us how we unwittingly might encounter this very quickdraw problem simply by carrying our quickdraws around in a pack. This is probably a greater danger for open slings used to create alpine draws than your conventional dogbone style sport climbing quickdraw. Nevertheless, it’s something we should all be mindful of anyway.

Location: Orpierre, Haute Alps, France

Nice dog! Is That a Bowline?

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Dog securely anchored to a tree with a bowline knot.

Dog securely anchored to a tree with a bowline knot.

I was walking in downtown Portland, Oregon a while back and I came across a dog tied to a tree in front of a restaurant. I noticed that the knot used to tie the rope around the tree was none other than the infamous bowline knot, suggesting that dog’s owner was either a sailor or a climber. I didn’t get to talk to the owner, so I guess we’ll never know.

I have to admit that the bowline surprised and delighted me–enough that I was prompted to take this very poor photo. I think it’s in part a matter of context. As a climber I encounter this knot all the time in alpine climbing anchors. However, I don’t expect to run across a bowline in the city. I mean urban dog owners typically don’t know their knots. I would have expected a square knot at best, or a ‘granny knot’ at worst.

The dog just stood there staring attentively, like he was waiting for something to happen.

“What ya looking at boy?” I asked him. And I half expected him to respond.

“Well this rabbit came out of the hole. He ran around the tree, and then he went back down the hole. If he comes back out of that hole he’s mine.”

Location: Portland, Oregon, USA