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How would you set up this anchor?

Discussion in 'Tech Tips and Gear' started by The Dread Pirate Roberts, Jul 6, 2016.

  1. The Dread Pirate Roberts

    The Dread Pirate Roberts

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    I came across this anchor last Friday in a fairly well traveled rout. The anchor is normally a climbing anchor I think. How would you set it up for SRT? The biners are are all for tethers.
    Thanks

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  2. Brian in SLC

    Brian in SLC Brian in SLC

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    Well...I'd just rappel it double strand, but...

    Run your rappel line through both anchors and biner/knot block one side.

    Was this a trick question? Ha ha.

    Horizontally oriented anchors are really common in the US at climbing areas.

    Where was that? Looks like granite. LCC?
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  3. Jman

    Jman

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    X2. I would do the same, personally.

    Keep it simple. No need to make it more difficult than what it needs to be for your group.


    Sent from my iPhone using Tapatalk
  4. The Dread Pirate Roberts

    The Dread Pirate Roberts

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    My first impression was exactly what you just said and I'm sure that would work just fine. That method however would violate a few of the basic rules of building an anchor:
    Solid Anchors
    Redundant
    Equalized
    No Extension
    Small Angles

    You would have solid anchors. The anchor would be redundant but with a shock load if one failed. They would not be equalized, in fact the primary anchor would have about 40% more weight than would be necessary (i.e. for a 100lb load anchor #1 would have 140lbs and anchor #2 would have 100lbs instead of like 54lbs on each). There would be extension. The angle is definitely not small.

    Like I said it's probably not a big deal I was just wondering what the CC would think was best practice. This anchor is the second real rap in the Great White Icicle, the hanging station that is on the RDC. I know there have been a few groups go through there recently so I thought maybe there was a different technique.

    Thanks for your response
  5. Brian in SLC

    Brian in SLC Brian in SLC

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    [​IMG]

    Uhhh....how'd the force go higher?

    Your weight is essentially tied to the first anchor, and, the rope goes horizontally over to the left anchor, but, travels through that anchor. So, you have your load hanging off one anchor, through another (and, gives that anchor some load due to friction through the ring) and the angles are 90 degrees. Right angles.

    With essentially 60% pulley efficiency at the second anchor ring, your load on the first anchor should reduce by that amount. So, 100 pound load at the first anchor is 60 pounds with the second anchor taking 40 pounds. Give or take. Maybe 70 pounds and 30 pounds (90 degree angles).

    Certainly not a force multiplier like the load angle between two anchors when the load is coming off a central line in the middle of the anchors that is above 120 degrees in angle.

    Here's the anchor to the west and slightly below the anchor you posted (traditional belay anchor atop the "bulge pitch"):

    GWI anchor right bulge pitch.

    (not sure why it won't upload in the correct orientation)

    When multiple climbing parties collide...ha ha. Now, that's an anchor CF...(why it worked out, we still don't know).

    Here's your anchor in the lower left...used for belay:

    GWI anchor left last belay.

    Fun stuff...sometimes its just best to rappel double strand....

    [​IMG]
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  6. gajslk

    gajslk

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    Har. I thought it was a trick question too. You could leave webbing and a quick link ... and you could make that anchor less safe if you aren't careful.

    Gordon
    ratagonia likes this.
  7. The Dread Pirate Roberts

    The Dread Pirate Roberts

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    @Brian in SLC That is a serious anchor! Calculate the forces on that one! Awesome pictures man.

    I could be wrong but...
    I'm not sure that the pulley efficiency would apply in a static situation but let's say it does. If the main anchor is on the left and the anchor on the right has the biner block then you have 70lbs on the anchor on the right. That's if the load is still 100lbs. If you isolate the main anchor, on the left, you have 100lbs down and 70lbs to the right (equal and opposite forces). So the net force would be the square root of (100^2 + 70^2). Give a total force on the anchor of 122lbs. Compared to something like 55lbs if the anchors are equalized. That doesn't include any shock forces.

    Maybe non of this really matters because those anchors are bomber but if they were questionable maybe it would matter. What do you think?

    Thanks for indulging my curiosity
    Ram likes this.
  8. Brian in SLC

    Brian in SLC Brian in SLC

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    Ahhh...I got ya.

    If you had just your weight hanging of either of the anchor, straight down, then, you'd have 100 lb load and 100 lb force at the anchor.

    Do we have this situation?:

    Deflection 90 degrees.JPG

    Since the ring isn't a frictionless pulley, would the load be 60% of 141 lbs? 84.6 lbs?

    Now my head hurts....ha ha.

    Be an interesting thing to measure. Some guys here have load cells. Easy to configure. Hang a weight straight down then deflect it.

    Ok, physics guys, some angular vector force help here...

    I get your point, though. Really good reminder about forces on anchors that we don't usually consider. I sling shot belay all the time. I need to remember to consider that it doubles the force at the anchor. Which is why in the alpine, on hastily built anchors, I belay direct from my waist to keep the force off the anchor.

    Good stuff!!
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  9. Brian in SLC

    Brian in SLC Brian in SLC

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  10. Canyonero

    Canyonero

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    The right answer is to tie and equalize a sling to get a SRENE or ERNEST anchor, then do your SRT through a rapide at the bottom of the sling.

    In reality, you just Fiddlestick it. Problem solved.
  11. Brian in SLC

    Brian in SLC Brian in SLC

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    Right answer is recognizing when to rappel double strand.

    Pull cord from fiddle stick in stream flow releases rappel line causing fatality. USFS becomes aware of folks recreating in a watercourse in a watershed area, bans rappelling waterfall. Problem solved.
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  12. The Dread Pirate Roberts

    The Dread Pirate Roberts

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    Your picture shows the situation perfectly! I think the pulley efficiency takes 60% of the 100lb load going to the right.
  13. CRNPRES

    CRNPRES

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    If you thought one bolt was not enough to hold you, why wouldn't you just add webbing and equalize it? In this case looking at the rock and inspecting the bolts (if they were good) would lead me to not equalizing it but some fragile sandstone it may be a different story.

    Passing through both without equalizing is still going to overload one bolt close to full load so without equalizing it would be like being one bolt.
  14. Craig

    Craig Feeling My Way

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  15. Brian in SLC

    Brian in SLC Brian in SLC

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    Completely different seasons which don't compete for anchors. My only concern initially was if anchors got moved that ice climbers might be in a bad belay spot but that really hasn't happened.

    GWI whipper last pitch.

    That anchor's seen a bunch of action! Above photo was of a leader fall. Guy broke his ankle. Rescue off of those bolts. I helped rescue a party that fell from the last pitch as well a couple of years ago.

    The usual anchor for many years at the top of what climbers call "the bulge pitch" was on climber's right, in a shallow alcove. Rock isn't great there and its a cramped location, and, sometimes the ice is thin there as well. New anchor is visible and at a length that most top out from it. Reduces the old pitches on the climb by one, and, keeps the troops movin' through. Although that stance is a bit cramped for a couple of parties (understatement).
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  16. Brian in SLC

    Brian in SLC Brian in SLC

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    Or, better yet, rappel double strand. Do I sound like a broken record? Ha ha.

    Easy without leaving any extra gear.

    Hank/Shane...when we did this many moon ago, I think this anchor wasn't there, but, we rapped into a corner on climbers' right (west)? Was it just the three of us? How long ago was that?
  17. Andrew Humphreys

    Andrew Humphreys

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    I've put in lots of this kind of set-up in commercial canyons. Unlinked anchors are the ideal choice if the bolts are exposed to flood water. Linked anchors get bashed around in the water, and they will eventually destroy themselves. For this reason, it's advisable to not add fixed webbing or chain to bolts like this.

    A properly placed bolt can hold 22kN. Your body weight is about 1kN; with the Pulley Effect, you're exerting 1.5kN on that deviating bolt. A hard bounce on the rope would exert maybe 3kN, up to 5kN on the deviating bolt. The average sport climbing fall exerts 3 to 5kN on the last clipped bolt, and people are taking big whippers every day. So yeah, I would say you're still within your safety margin.

    If you're stressed about not equalizing, add a sling and a few carabiners to make it happen. And now for the shameless plug, here's the tool I promote:



    Edited: Changed the word "permanent" to "fixed" to alleviate semantical problems.
    Last edited: Jul 9, 2016
  18. wsbpress

    wsbpress

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    I'm looking forward to some future lucky bastard posting a custodianeering pic of stacks of Attachés and dyneema runners after doing Spry.
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  19. Canyonero

    Canyonero

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    Probably not, but definitely a good reason to use DRT (which is exactly what I did the last time I did this route.)
  20. Canyonero

    Canyonero

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    Where can I get me some of that permanent webbing?
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