Friday, November 10, 2006

More on clipping

The posts on clipping and falling distances have generated a lot of email. Some graph paper will help in working the various clipping situations; we're all conditioned to think of the fall distance as twice the amount of rope above the last piece, but when clipping overhead the fall distance isn't twice the amount of rope above the last piece... Ulimately a fall while clipping is roughly equal to twice the distance between the two pieces, regardless of where the climber falls off while clipping. Diagrams drawn to scale will help sort this out. My friend Bill B sent the following in, good points also--it's not just starting point of the fall that matters, but also how belayers deal with over-head clips:

"I would consider a couple other factors here; 1. the climber will most always pull thru more rope than he/she needs, 2. the belayer will most always chuck out more slack than the climber will take (this is quickly adjusted for, but after the clip is made). Fall at the wrong moment before making the clip and the fall will certainly be longer than if you clipped at the waist. " -Bill B.

Understanding the physics allows us to make better decisions about difficult clips. I've seen a few accidents recently that just didn't have to happen, and a couple of other very close calls, I don't think enough climbers have thought this through carefully.



JD LeBlanc said...

OK, since I’ve been yapping a lot from the ARMCHAIR, here’s my take. Not a rocket scientist, but the only real issues I see with BAD falls, is the BOLTING. Take Swank M8, Haffner Creek, BC; DD can clip the second bolt from the deck, presuming snow. The 3rd and 4th are ok – 4th bolt - you could hit your belayer. Bolt number 5 is really the issue. Yeah, its easy terrain, but if ice, or rock fails, you’ll hit the deck. Hip clip or not! As Bill B. notes – here’s a good photo of it in action:

F-ing sport belayer – but it is CSI and he doesn’t fall? Roger S. is looking and saying – DUDE! Evgeny K. is the photographer and likes the belay method – besides he and I were BB style and they were full-on spurring – he kind of liked to watch the struggle – he is after all a core-climber and funny man. CSI sent and the f-belayer didn’t.

I’ve not read the book – tried to get one from the author at the OR SLC tradeshow, but he declined! Damn him! Oh wait, isn’t that you? Milton didn’t get one either, I can understand the sidekick not getting one, but Milton?

My guess is that people comment that the falls may not be “X”, but X.5 or X.33, maybe X/pie squared - Too many variables to give a definitive statement. Hip clips reduce the length of fall over “above-head”. Well, the one clip that definitively reduces all fall length is the one you get into the DAMN biner! Often the length of fall is heavily dependent on your belayer, rather than where you clip the darn thing. And often not the belayers fault, after all you did fall off.

I fell clipping into a station at Acephale on a 25m route. Clipped the draws to the anchor and the ‘ear’ I was clipping off snapped and I teetered and then fell. Above the last bolt about 10 feet, so I was expecting a 25 footer. The belayer was NOT expecting a hold to break, fed out slack to clip the anchor – leaned into his pack to get a STOGIE – then he goes; “oh-shit!” DD gets a ride up to the first bolt, about 15ft off the deck - I pass him and stop about 3ft from the ground. So the ride was a smidgen over the “X” distance closer to an “XX”. Oh yeah, I was trying a hip clip.

Anonymous said...

I've read your info regarding clipping and, while I didn't pull out the graph paper, I did use a string demo and am not seeing your logic.

Here's my scenario:
- assume a vertical face
bolt3 (30ft above ground - not clipped)
YOU (28ft above ground)
bolt2 (20ft above ground - clipped)
bolt1 (10ft above ground - clipped)

If you overhead mis-clip 2ft from bolt3 (ie. 8ft above bolt2) then you'll have 8+2+2=12ft of slack rope and a 24ft fall from 28ft above ground. (You better hope you got less than 4ft rope stretch!!). If you mis-clip at your harness then you have 10ft of slack rope and a 20ft fall from 30ft above ground.

Seems to be safer to clip from the harness at bolt height. What am I missing!?

Will Gadd said...

Hi Anon, you're definitely right that clipping at waist-level is often safer than clipping overhead. That's the main point of all of this, so you're not missing anything in my mind in terms of where it's generally safer to clip. But your math is wrong in your scenario for total fall distance. I've written a few explanations below that I hope will help you understand...

In your scenario you don't fall twice the distance of the amount of rope you have above the last piece. That's the error I made as well when I wrote my book. Seems obvious that you would and that's how we are often taught to think of lead falls, but it doesn't quite work that way when part of the rope is "above" you. We actually end up the same distance below a piece as the amount of rope we had above the piece when we fell...

It's funny, I too refused to believe the graph paper for some time until I really counted the squares and thought it through. In your example you correctly have 12 total feet of rope in the system above the last piece at 20 feet. So you'll definitely end up with 12 total feet of rope below the 20 foot piece after the fall, right? What's 20 minus 12? 8. If your harness starts the fall at 28 feet and ends at 8 feet how far did you just fall? 20 feet... It's fun to run this scenario using a "long armed" climber who can clip 6 feet over his/her harness; Now there's 16 (10 to the missed clip, six from the missed clip to the harness) feet of rope above the last piece and the climber will end up 16 feet below the last piece--four feet off the ground. But the fall is still 20 feet, the "extra" six feet of rope going from the climber's harness to his attemped clip hand doesn't increase the fall.

So in your scenario, you actually fall 20 feet and end up 12 feet below the last piece--the two feet of rope going from your harness to the clipping point doesn't "double" or add to the fall distance. Count your squares on the graph paper, or with the string--the fall distance is exactly 20 feet (ignoring rope stretch, belayer feed, etc.) The KEY difference in the clip at waist and clip overhead scenarios is that the starting point for the fall is higher off the ground when clipping at waist level (safer). Belayers also tend to feed more slack than absolutely necessary, and climbers generally also pull more slack, which adds at least a few more feet of slack in the system when clipping overhead...

Just for fun and 'cause I'm a nerd, think of a climber who has a bomber piece at 100 feet above the ground. He climbs up another 20 feet, rattles in a sketchy piece, and starts climbing down to get back to his bomber piece. Unfortunately, just as he gets his harness level with the bomber piece he falls, the top piece blows, and he goes for a ride. How far is he going to fall? 20 feet? 40 feet? 80 feet? He has 40 feet of rope above the last piece now, our "classic logic" would tell us he's going to go 80 feet... Nope, he's going to end up 40 feet below the "bomber" piece because he had 40 feet of rope above it. Total fall 40 feet... This is just an exaggerated version of the clipping overhead scenario.

Please post your results and maybe your thought processes, I think a lot of people find this difficult. It's very hard to break the idea that "fall distance is always equal to twice the amount of rope above the last piece." Not exactly...

I'll post this in a new blog post as well, I've had a half-dozen discussions on this now. I expect a non-climbing math student would figure this out very fast, but as climbers we have a very strong, almost religious belief that fall distance equals twice the rope above the last piece. In the last two weeks I've had three major beliefs I hold about climbing seriously revised: fall distance, half-rope impact forces, and the use of Cordelettes...