What's Wrong?

[oldno7]

A new thread to help understand anchoring and it's intricacies.


The first pic is provided by mzamp

discuss

[skiclimb3287]

If I am not mistaken, on a wrap 2 pull 1, the water knot should be against the front of the tree so that more friction is working in your favor to help reduce the stress on the knot.

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[SRG]

If I am not mistaken, on a wrap 2 pull 1, the water knot should be against the front of the tree so that more friction is working in your favor to help reduce the stress on the knot.

Yes, this is one of the major advantages of the wrap 2 pull 1 rigging. In the first pic the water knot would have less force applied to it if it were positioned on the front of the tree. Even less force if it were a wrap 3 pull 2.

In the picture, the quicklink is attached to the webbing at an overhand on a bight. I think this knot would become the weak spot in the rigging and negate the strengthening effects of isolating the water knot mid-tree.

[ratagonia]

Yes, this is one of the major advantages of the wrap 2 pull 1 rigging. In the first pic the water knot would have less force applied to it if it were positioned on the front of the tree. Even less force if it were a wrap 3 pull 2.

In the picture, the quicklink is attached to the webbing at an overhand on a bight. I think this knot would become the weak spot in the rigging and negate the strengthening effects of isolating the water knot mid-tree.

While your point may be technically true, it is an insignificant difference, for two closely related reasons:

A. The diff between the two locations of the back-knot is perhaps 7000 lbs for one and 6500 lbs for the other. Even with two hefty canyoneers rapping at the same time, you would be hard pressed to produce anywhere near this kind of load, unless one of em had an SUV in his pocket.

B. The weakest point in this rigging is the overhand knot next to the rapide. This knot is likely to be around 6500 lbs, maybe a little less.

May I suggest that understanding the significance of choices in your rigging is an important skill, in addition to knowing what the "textbook" best practice is.

:moses:

[ratagonia]

A new thread to help understand anchoring and it's intricacies.


The first pic is provided by mzamp

discuss

This anchor does not need a piece of webbing or rapid link. The rope can be placed around the dead tree, and it will pull just fine. Leaving webbing and a rapid link is litter, and unnecessary in this case.

(unless, actually, it is not).

:moses:

[SRG]

May I suggest that understanding the significance of choices in your rigging is an important skill, in addition to knowing what the "textbook" best practice is.

I understand that in this case the main reason for choosing this style rigging was likely to hold the anchor at a specific point on the tree, not due to the bomber nature of the wrap-3-pull-2, but still I thought I'd point it out cause this is a "What's wrong?' thread, where someone posts a picture of rigging and then someone else posts what they see wrong with it.... I saw what looks like an improperly rigged wrap-2-pull-1.

[nonot]

Not sure what you're poking at oldno, maybe the bight next to the rap ring is too close to the tree, resulting in much larger forces than necessary due to the triangular angle increasing the load, but I've rappelled on worse.

[Bootboy]

I'd hit it

[oldno7]

My input and it's just that.

A textbook rigging of a wrap 2 pull 1, does indeed place the water knot at the front of the tree or whatever you are anchoring to.

The difference may be semantics, but it is never wrong to get the best performance out of an anchor set up.

I do have a "bit" more concern on the small overhand knot that the rapide is tied into.

My math gives a single strand of webbing around 4200lb breaking strength. Putting this overhand in, reduces that by roughly 30%.

Knots in rope or webbing will generally be the weak/breaking point of a system, we cannot avoid them but we should use them wisely.

At one point in my canyoneering career, I would argue the overhand knot in the end of a wrap2 pull 1, had a "slight" chance of adding redundancy, depending on whichever side of your webbing might fail, a very small chance, but once again, it cannot be wrong to rig your anchors for optimum strength. If one is to add the overhand, I might suggest that the longer you leave the bight, the more an anchor will remain equally loaded with lateral movement by a rappeller.
The beauty of not adding an overhand is that the rapide can float from side to side if a rappeller is moving laterally while abseiling.

This type of discussion by canyoneers usually benefits all. I would say when the majority are satisfied with solving a problem/or lack of, on an anchor picture, someone post another to discuss.

No input should be belittled, all input is encouraged.

[oldno7]

The good I see in this set up is, a wrap 2 pull 1 was initially used for 2 reasons:

1-to keep the webbing up and out of the watercourse
2- to facilitate an easy pull

[unimog]

From my training, the water knot is on front for two reasons: 1- so it sees less tension; 2- it is more visible and easier for each rapeller to inspect.

[oldno7]

From my training, the water knot is on front for two reasons: 1- so it sees less tension; 2- it is more visible and easier for each rapeller to inspect.

Valid points

[oldno7]

Not sure what you're poking at oldno, maybe the bight next to the rap ring is too close to the tree, resulting in much larger forces than necessary due to the triangular angle increasing the load, but I've rappelled on worse.

Not really "poking" at anything, just trying to stir up discussion on a topic that needs attention as born out by a recent death and a recent 60' fall.

Please feel free to add a picture for discussion.:2thumbs:

[canyoncaver]

That knot in the front is good to about 4,000 lbs tops. Unless you guys use some other kind of webbing that I'm not familiar with.

4,000 lb. webbing X 2 = 8,000 divided in half for overhand knot = 4,000.

The knot is also unnecessary. It does not provide any redundancy. Leaving the knot out does not increase strength, it only reduces unnecessary complexity. 4,000 lbs is plenty of strength for a rappel anchor.

[Scott P]

The knot is also unnecessary.

That's what I was thinking.

What is the purpose of the knot where the rapid link is?

[SRG]

Canyoncaver,
I'm confused by these two statements as they seem to be saying opposite things...


4,000 lb. webbing X 2 = 8,000 divided in half for overhand knot = 4,000.


and


Leaving the knot out does not increase strength, it only reduces unnecessary complexity.

It seems from your first explanation that leaving the knot out would indeed increase the breaking strength from 4,000 to 8,000lbs. Could you please explain?

[canyoncaver]

Oh sorry, yes I should explain.

When you knot webbing, it decreases its strength by about 50%. Two knots also decrease the strength by 50%, not 100%. Three knots also decrease the strength by 50%, not 150%. This is because when pulled to failure, the webbing will break at one of the knots somewhere near 4,000 lbs of force. It doesn't matter which knot.

In the example above, there is already a water knot in the webbing, so removing the overhand does not restore any strength.

Hope this helps. If not, let me know.

[oldno7]

Oh sorry, yes I should explain.

When you knot webbing, it decreases its strength by about 50%. Two knots also decrease the strength by 50%, not 100%. Three knots also decrease the strength by 50%, not 150%. This is because when pulled to failure, the webbing will break at one of the knots somewhere near 4,000 lbs of force. It doesn't matter which knot.

In the example above, there is already a water knot in the webbing, so removing the overhand does not restore any strength.

Hope this helps. If not, let me know.

Generally I would agree but in the instance of a wrap 2 pull 1, stress on the water knot is reduced. Thus if there is to be a breaking point from direct load(doubtful), the week point is the overhand knot--not the water knot.

On the redundancy issue--go and tie a wrap 2 pull 1, there will have to be one strand overlapping the other. Depending on whether there is a failure of the under strand or the loaded strand, an overhand knot MIGHT be redundant. Try it....:mrgreen:

[canyoncaver]

On the redundancy issue--go and tie a wrap 2 pull 1, there will have to be one strand overlapping the other. Depending on whether there is a failure of the under strand or the loaded strand, an overhand knot MIGHT be redundant. Try it....:mrgreen:

Yeah, I hear ya. I just don't consider that redundant enough to really be called redundant. At least not by my high standards... :afro:

[bjp]

it is never wrong to get the best performance out of an anchor set up.
Well, I think it's pretty clearly true that it is never wrong to get the best performance out of an anchor setup when all else is truly equal. But all else isn't equal -- people have limited attention, memory, and time. In this case, I think the evaluation of the inline water knot should be "it will not break" rather than "it would be stronger if it were in the front". When evaluating the options of "spend a bit of extra time to scoot the knot around to the front" and "screw it, just rappel on it as-is" using EARNEST criteria, both anchors are far Stronger than they need to be -- there is no change in the safety afforded by Strength between the two options. But, there is a change in Time -- the first option takes some additional time/attention and that is a limited commodity. I would argue that any extra effort spent ensuring that the joining water knot is in the front of this anchor makes the group marginally less safe.

Of course, if someone is setting up the anchor and it takes the same amount of time to put the knot in front as in back, then everyone should learn to put the knot in front because all things are equal, and that is the stronger anchor.

So, from the perspective of "how should this anchor have been rigged by a perfect canyoneer", I think you're totally right. But, from the perspective of "I constructed/found this anchor; now what should I do?", the knot should stay at the back.

This:

While your point may be technically true, it is an insignificant difference
...
May I suggest that understanding the significance of choices in your rigging is an important skill, in addition to knowing what the "textbook" best practice is.

[Brian in SLC]

This anchor does not need a piece of webbing or rapid link. The rope can be placed around the dead tree, and it will pull just fine. Leaving webbing and a rapid link is litter, and unnecessary in this case.(unless, actually, it is not).

Maybe. Dead tree looks kinda scrappy, especially where a rope could roll down and get pinned in one of the loose pieces of bark/wood. If you can't pull the rope easily, that'd be reason enough to leave a sling.

[oldno7]

Yeah, I hear ya. I just don't consider that redundant enough to really be called redundant. At least not by my high standards... :afro:



I hear ya as well, just thought it might be interesting to discuss.:twisted:

Food for thought to keep in the back of your mind for "someday":mrgreen:

[oldno7]

Scenario:

You arrive at this anchor and don't have the tools to help it out.

How should you safely get your group past it?

Your group is 5---ranging in weight from 155-260lbs

[Renatomic808]

Depends what the drop looks like? If that's all you got on a 200+ rap, I'd have the last person sit far back as a backup meat anchor. He/she goes down with the higher risk. If you can bypass it/downclimb... well i'd do that.

[Mountaineer]

Scenario:

You arrive at this anchor and don't have the tools to help it out.

How should you safely get your group past it?

Your group is 5---ranging in weight from 155-260lbs

Assuming no other anchor points.

Contingency anchor on the chain (or webbing loop through the hanger to avoid the chain if it is suspect given the apparent hanger failures), backing it up with meat at the contingency point/rigging (not at the hanger). Heaviest goes first (assuming everything else with the dynamics, location, environment, experience is equal). If it holds OK, last person goes down at a bit higher risk. Be ready below...:eek2:

[Brian in SLC]

Scenario:

You arrive at this anchor and don't have the tools to help it out.

How should you safely get your group past it?

Your group is 5---ranging in weight from 155-260lbs

Can't tell from the photo, but, are both the aluminum anchors jacked?

If I could sneak a piece of webbing under the top anchor's hanger, and, shuffle it around so its on top of the bolt, but, still under the hanger, I'd use that to back up the single bolt.

The single bolt/chain/ring rig looks bomber to me. I'd inspect it and maybe bounce on it lightly to see if it was robust, then, send the biggest guy down first with whatever back up I could cluge off the hammered bolt/hangers.

I place those double hanger/chain/ring anchors all the time. They're nice.

[Absolute Gravity]

I'll go with what Renatomic808 says. That hangar doesn't look terribly scary to me. I am curious as to what is holding the fourth hangar (under the block) to the wall though.

[canyoncaver]

I assumed that the fourth hanger is attached to the ring, but blew out of the hole with the scratched arrow. So no longer attached to the wall.

[oldno7]

o.k.--little add on.

Drop is 80' in the direction the rope is currently hanging.

2-aluminum hangers are toast

hanger with chain, freely rotates on the bolt but bolt doesn't pull with finger pressure.

I think that covers everybody.

[Slot Machine]

I'll go with what Renatomic808 says. That hangar doesn't look terribly scary to me. I am curious as to what is holding the fourth hangar (under the block) to the wall though.

From Ren's hypothetical 200 ft?? BZZZZZT! Wrong!

Not terribly scary... but if that bolt fails, then your last guy dies.
_____

Nice job posting this problem Kurt!

[SRG]

When I come to a single bolt and hanger, I typically rappel off of it after inspection. In this case the two(three?) broken hangers would sketch me out even if the bolt in question looked solid... especially if this is at a rappel station in a canyon.

I'd opt for this...
If I could sneak a piece of webbing under the top anchor's hanger, and, shuffle it around so its on top of the bolt, but, still under the hanger, I'd use that to back up the single bolt.

[Slot Machine]

2-aluminum hangers are toast

hanger with chain, freely rotates on the bolt but bolt doesn't pull with finger pressure.



Top anchor - toast.
Middle anchor - chain.
Bottom anchor - toast.

The toast is still usable IMO.

I like Brian's solution best, but if the toast anchors were bolted tight against the wall, then you should at least try to do something creative with the toast that could hold. Better than leaving your last man's fate to a scary spinner, right?

Cut two pieces of rope, then stuff a piece of rope up and through each of the damaged bolt hangers. Then tie each rope in a big knot, to block the rope from pulling down and through the regular hole in each hanger. Then weight each rope, to see if it pulls through the cut in the anchor. If it does, then you need to fill each damaged hanger with more 'stuff'.

Two ropes in each? To pieces of webbing in each? Whatever fits and doesn't work through the cut in each bolt hanger. Weight each of the three anchors. Make sure they individually will probably hold.

Then you have the chain, plus the two backups.

[Absolute Gravity]

In this case the two(three?) broken hangers would sketch me out even if the bolt in question looked solid... especially if this is at a rappel station in a canyon.

Seriously! Looks like two empty bolt holes, 1 dangling hangar, 2 broken hangars, and then 1 loose hangar. A lot of fail there.

[Slot Machine]

Seriously! Looks like two empty bolt holes, 1 dangling hangar, 2 broken hangars, and then 1 loose hangar. A lot of fail there.

Kurt's shot is from an anchor station in Imlay (if I'm not mistaken). I guess logs are washed through there periodically and destroy those bolts by snagging on the webbing.

Our friend Tom fixed this thing recently, I think. Where is he anyway, to tell us a better solution? :mrgreen: :fishing:

[ratagonia]

Our friend Tom fixed this thing recently, I think. Where is he anyway, to tell us a better solution? :mrgreen: :fishing:

Canyon Collective...

:moses:

[Absolute Gravity]

Kurt's shot is from an anchor station in Imlay (if I'm not mistaken).

I figured you were not, and it was easy to find.

http://www.canyoneeringusa.com/rave/imlay-on-memorial-day-weekend/

[Slot Machine]

65510

I joke with you Tom... :haha::lol8::haha::lol8::haha: :hippy:
_____________________________

Sorry to hijack the thread. It's a good one to get creative with. What would you have done with that anchor Kurt?

[ratagonia]

Kurt's shot is from an anchor station in Imlay (if I'm not mistaken). I guess logs are washed through there periodically and destroy those bolts by snagging on the webbing.

Our friend Tom fixed this thing recently, I think. Where is he anyway, to tell us a better solution? :mrgreen: :fishing:

Tie off the huge log that is 20 feet back.

Or rap off the new, 1/2" bolt. Yeah it is only one bolt. Have you been in Imlay in the last 5 years? There have been like 10 raps off single bolts that are really skanky. So by this point, you have rapped off a bunch of unsafe museum pieces. In comparison, this single, new 1/2" bolt is truck!

Tom

[oldno7]

So---someone post up another anchor

[Udink]

So---someone post up another anchor
:ne_nau:

65521

[SRG]

:ne_nau:

This is an easy one.... there needs to be a sock or underwear or something tucked under the yellow rope on the left side... you know, for equalization... :lol8:.. also the shirt should be the same color as the rock... to enhance the "natural feel" of the anchor.

[Slot Machine]

Tie off the huge log that is 20 feet back.
Or rap off the new, 1/2" bolt. Yeah it is only one bolt. Have you been in Imlay in the last 5 years? There have been like 10 raps off single bolts that are really skanky. So by this point, you have rapped off a bunch of unsafe museum pieces. In comparison, this single, new 1/2" bolt is truck!


Hmm... I seem to remember you saying a while back, something like "If my safety is at stake, then maybe isn't good enough." And that seems like a reasonable motto.

I'm sure the new bolt is bomber. BUT, if it fails, you die. Seems odd that you are ok with rapping off a series of single bolts, some that are museum quality. Don't they fall into the 'maybe' category?

Honest question- why so nonchalant about the bolts in Imlay?

Bob

[ratagonia]

Hmm... I seem to remember you saying a while back, something like "If my safety is at stake, then maybe isn't good enough." And that seems like a reasonable motto.

I'm sure the new bolt is bomber. BUT, if it fails, you die. Seems odd that you are ok with rapping off a series of single bolts, some that are museum quality. Don't they fall into the 'maybe' category?

Honest question- why so nonchalant about the bolts in Imlay?

Bob

Not so non-chalant, really. We (ie, Zion locals) have been working to get at least one good bolt into each standard rap over the last few years. It is an on-going project and involves a lot of work. Pretty close to done, at least on the lower canyon.

Those two destroyed aluminum hangers were part of that effort, pretty much the start of that effort. Crazy to see them ripped through like that. Jonathan's replacement bolt w chain was part of that effort. My going in with more tools and and finishing that anchor was part of that effort.

The truth is, people rap off single bolts all the time. Just did The Squeeze - yikes what a nightmare. So many raps there off single bolts, sometimes backed up elsewhere, sometimes not.

See: http://www.canyoneeringusa.com/rave/canyoneering-the-squeeze-san-rafael-swell-utah-anchor-survey-sept-2012/

So I think it IS a good question.

Long term, rapping off skanky single bolts will catch up with SOMEONE. I'm hoping it is not me, and I have made it a crusade to get rid of skanky bolts in the backcountry. Bolts in the newly revealed Happy Dog, Poe and Baboon are on the list of unsafe single bolts - so we try not to use those (and mostly succeed).

A complicated answer to an apparently single questions. People trust those bolts because it is convenient, and people have trusted them before. It is impossible to eliminate all risk in the sport, but yes people should choose their risks carefully. In this particular case, since I know who placed that bolt and when, and that it is a 1/2" bolt and entirely in shear, I am fully comfortable with rapping off that particular bolt.

Tom

[hesse15]

Not so non-chalant, really. We (ie, Zion locals) have been working to get at least one good bolt into each standard rap over the last few years. It is an on-going project and involves a lot of work. Pretty close to done, at least on the lower canyon.



The truth is, people rap off single bolts all the time. Just did The Squeeze - yikes what a nightmare. So many raps there off single bolts, sometimes backed up elsewhere, sometimes not.
Long term, rapping off skanky single bolts will catch up with SOMEONE. I'm hoping it is not me, and I have made it a crusade to get rid of skanky bolts in the backcountry. Bolts in the newly revealed Happy Dog, Poe and Baboon are on the list of unsafe single bolts - so we try not to use those (and mostly succeed).
Tom

why Imlay does not have stainless steel glue in bolts in couple with rap ring or directly rapping out of the bolt?
they probably will get trashed less in a flood not having much debris can catch on?

[Slot Machine]

why Imlay does not have stainless steel glue in bolts in couple with rap ring or directly rapping out of the bolt?
they probably will get trashed less in a flood not having much debris can catch on?

Great idea! Problem is once you have them installed, you can't use them. They have to cure/dry for a while.

However, you could place 1/2 inch bolts up high and permanantly put steel rings on them. Bolt hanger - quick link - steel ring.

Just put some epoxy on the threads of the quick link, so they don't wander away.

Disclaimer - I've never bolted anything. Just an idea. YMMV. :mrgreen:

Bob