Bombproof Anchor?

A little situational awareness goes a long ways, in climbing, and life.

Yeah..you just slap a length of chain on, with a screw gate.

Yes, it's Science Friction. I have seen other "shot at anchors" in the swell also...luckly they were crappy shots, or whisky faced...or both. yeehaw!

Michael:

You asked when can you stop placing pieces. I was taught a rule of thumb for this that I've found useful:

Your anchor should have a total score of 8, where each individual piece of protection is given a score of:
4 = bomber, would trust my life to it if needed.
1 = sketchy, would only use it alone if being chased by a bear, etc.
2 and 3 = somewhere in between.

Pretty subjective of course, but I've used it to justify stopping at using only 2 pieces for an anchor (i.e., both are just honking bomber), or using more than 3 (two good placements (3 each), but one really sketchy (1); add another piece).

In general, 3 decent placements gets you to a score of 8 total.

Jeff Fiedler wrote:Your anchor should have a total score of 8, where each individual piece of protection is given a score of: 4 = bomber, would trust my life to it if needed.

I would end up with a lot of 2 piece anchors by this method.

--Marc

Jeff,

I didn't mean to literally be asking the question. Instead, I'm saying that's the question posed when building an anchor. I think it's an interesting question to ask when building an anchor. I was also trying to be a bit light hearted in this discussion because I see a lot of "interesting" anchors and I sometimes wonder why someone called their anchor good after their 6th piece, for example.

There is a similar scoring/points system used within the AMGA to answer the question of when to stop placing pieces in an anchor and call it good.

Well, maybe my definition of a "4" wasn't clear. By bomber I meant really really, live 4-foot-diameter tree in solid ground bomber, absolutely no question it would fail bomber. Or a larger size nut/hex in a deep inward-flared constriction, i.e., beyond a shadow of a doubt you would have to destroy the piece before it could pull out downward or sideways. Not just a, "oh yeah, looks pretty bomber".

So I'd say most of my placements are decent "3's" and only rarely do you get a "4".

Similarly, my "1" really meant, would only trust your weight to it if literally the only other option was dying. Really crappy.

Well, anyway, I found the "rule of 8" a good beginner lesson to stay out of trouble.

brenta wrote: I think this study is flawed in many respects.

My impression of this study was that they show destructive testing of the anchor based on a certain type of rigging. I can't provide a direct answer to your concerns.

I think one of the points they brought out about angles was surprising to me. I think they were going after: If you had the choice between good placements & marginal angles OR good angles & marginal placements; choose the good placements.

In review of this thread, we discussed a little bit about the material used in a no-extension rig. I would agree with this report that by using elastic rigging, it will react better to manage the energy than by using high-strength dyneema/spectra as the main rigging.

I disagree with their quick summary of sliding x rigs. It's easy to make this rig both redundant and limited extension. Stricker had offered the thought of the possibility of biner cross loading in a sliding x (I can't remember the thread topic); but I can't see it unless the angles are just so pronounced -- I can see friction being a problem, which is why sling redundancy should be a part of this rigging.

As to why use cord. It's just one tool for redundancy -- I think this report does show it can be relied upon for recreational climbing within a redundant system. If the climber's have just one leader and/or multiple seconds; this rig offers workable tie-in points for climbers, equipment, & packs. You can also use cord for decent anchors/v-threads, buddy evac, self ascension, & probably other applications I can think of if I had some more time.

Can't you use slings also? sure; but I'd like to keep slings for leading. And, what about leading ice, most of which climbers have screamers; cord would be a real nice thing to have.

Can't you just use the rope? sure, if swinging leads, this is the ticket. I don't think anyone has really disputed the value of the climbing rope as anchor rigging.

Overall, the main point I think with these findings is to look at whether or not cord will serve adequately to make a redundant anchor; I feel okay with what they found.

Mark Nelson wrote: My impression of this study was that they show destructive testing of the anchor based on a certain type of rigging.

There was a bit of destructive testing, but mostly it was not. In the main tests, they pulled only until the main load cell read 20 kN. If you look at the bar charts, you will see how most bars in the rightmost groups extend to exactly 20 kN.

They also pulled until they broke the cord in the experiments of Figure 20, but that's only a small part of what they did, and effectively confirmed that 7 mm cord doubled up and passed through a biner will start breaking at a bit less than twice its rated strength.

Mark Nelson wrote: If you had the choice between good placements & marginal angles OR good angles & marginal placements; choose the good placements.

In a way, it's hard to argue with this. A marginal placement may hold close to nothing. At least, with angles, you know what you are getting into. My gripe with this conclusion of theirs is that they fail to mention that widening the angle in a three-point anchor puts most of the stress on the middle piece. Granted, it is better than in a two-piece anchor, where the forces may exceed that in a one-piece anchor, but there's still a considerable incentive to keep the angle small.

Mark Nelson wrote: I would agree with this report that by using elastic rigging, it will react better to manage the energy than by using high-strength dyneema/spectra as the main rigging.

It stands to reason, though this report does not contribute new evidence.

Mark Nelson wrote: Overall, the main point I think with these findings is to look at whether or not cord will serve adequately to make a redundant anchor; I feel okay with what they found.

Yes, I would agree that 7 mm cord can be used to build safe anchors.