You won't be clippin' my lead line through just one bolt of a two-bolt anchor.

Gotta go with Brian on this one. (people are overdoing the theory side of things)


Jay,
Assume a two bolt anchor. What type of anchor system are you using? Do you place the lead draws above or below your anchor system and to which side?

What happens if you start climbing on the right side of the anchor and move to the left side before you can place any gear?

You won't be clippin' my lead line through just one bolt of a two-bolt anchor.

Now pretend that both bolts are dubious and your standing on a ledge.

Be a rare route where a quick draw thru each bolted anchor would provide equal force on each anchor. Especially if the anchor is vertically positioned and you clip a draw into each bolt hanger.

...when the second falls a breaking force at least equal to his body weight must be applied in order to arrest the fall. Thus the maximum tension in the second's side of the rope must be at least 2 times the second's body weight.

This isn't the way rope tension works. At every point in the rope, there are a pair of equal and opposite forces, but this does not mean that the tension in the rope is double either one of them. The tension is the value of just one of the pair of opposing forces. If you hang a 50 lb weight from a rope, then the tension in the rope is 50 lbf, not 100 lbf.

However, you are right for another reason, and that is that when you hang a weight on a dynamic rope, the rope stretches, causing an increase in tension. At the maximum stretch (there is a recovery after that), the tension rises to a momentary peak of twice the original load. Thus,your claim that there will be a (momentary) tension of twice bodyweight is correct, as is the claim that the top piece will experience a load in excess of three times bodyweight.

Does anyone have a better source for a description of how to tie a "Dog eared bowline" than the one that was printed in the mag? Does the knot go by any other name? I haven't seen it anywhere else.

Assume no friction across the biner. Then, in order for there to be no slippage of the rope thru the biner, the braking force applied would have to be two times bodyweight, at least momentarily, wouldn't it?

This goes for every anchor and no anal-retentive thread like this one can adequately cover every qualifier ("assuming both bolts are bomber...", "if it's a hanging belay...", if the belayer is asleep with too much slack in the system...", etc.).

If Climbing's Tech Tip bothers anyone that much, clip another draw to the second bolt, a la jt512, and climb on.

It's been called a bowline-on-a-bight for centuries. But some bonehead decided to make up a new name and describe a hard way to tie it. Long described this anchor as the "Atomic Clip" almost a decade ago.

The double bodyweight figure that must be held comes not from the pulley, but from the fact that, momentarily, there really is double bodyweight tension in the rope because of the effect of rope stretch. This is just as true if the rope is a fixed rope tied to an anchor with no pulley in sight as it is if the rope is redirected through a pulley.

By the way, the double body weight rope tension figure can be obtained from the standard equation for fall-induced rope tension by taking an H/L ratio of zero, i.e. by assuming a "fall" of zero height.

But by clipping the leader through just one, you are defeating the whole purpose of having two bolts there in the first place, especially if the belayer is not on a ledge.

On the contrary, two identical draws will provide very good equalization on most two-bolt anchors in the U.S., where the bolts are almost always aligned horizontally.

Not ditto always for me.

I think I like the leader and their potential factor two fall on just one bolt. If the bolt fails, then the force is on the belayer via the belay device on the harness. I prefer taking the force of the lead climber after that single bolt fails on me (I'm assuming a non-hanging belay station where I'm standing on my feet). Then the single bolt I'm anchored to is the backup, and I'm holding my partner whilst on my feet, off my harness. Seems like it would add a more dynamic shock reduction to the whole system.

If the leader fell and the force was on both bolts, and they both failed, yikes. At least by only clipping one, the force will only initially be on one, then transferred to the belayer, whilst the single remaining bolt would be the last ditch back up with a much lower force coming on it should the belayer's knees buckle.

I almost always only clip the leader to a single bolt off a double bolt anchor for the above reason. And, after the leader gets in a bomber piece of gear or three, I'll unclip them from that single bolt.

YMMV...

Brian in SLC

In this scenario why redirect at all? Wouldn't it be even safer to belay directly from you harness?

Only if the route goes directly in a straight line above the belay...

Er something.

Brian in SLC

It does not fulfill all of the SRENE requirements...specifically the 'Never/Not Extending' requirement.

If the right hand bolt blows then the quickdraw will fall until the 'dog eared bowline' fully extends and thus will shock-load the left hand bolt.

Agree?

Bryan

No. If the leader falls before clipping the first bolt above the anchor, two draws will still provide good equalization even if the route doesn't go straight up. This is because the leader will end up penduluming directly below the anchor, where the maximum (or close to it) impact force will occur.

Isn't the atomic clip based on a figure 8 and not a bowline?

Would seem awkward to manage if the anchor was widely spaced (and a bit more rope drag as the rope wouldn't run as smooth perhaps)...cleaner if just clipped single.

You're right. Leader down on one, belayer up on the other. Should kinda equalize.

Would seem awkward to manage if the anchor was widely spaced (and a bit more rope drag as the rope wouldn't run as smooth perhaps)...cleaner if just clipped single.