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Derek DeBruin · · Unknown Hometown · Joined Jul 2010 · Points: 585
mattm wrote:

I'm hoping Jim will chime in here as I can't recall specifics but if I recall correctly, GriGri's will slip around 4.5kN highly dependent on rope thickness and coating etc with others such as the AlpineUp more in the 2kN range.  So the forces found in their tied off scenario of 8kN seem unrealistically high given the fact even an ABD a device will start to slip before the peak loads found in their tied of scenario are reached.  I'm also not a fan of how little emphasis is given to the "flying belayer" syndrome or loss of control by the belayer in high impact falls.  They do acknowledge it yes, but for me this is the BIG gotcha.  IF the belayer can't hold the force (no glove, rope slipping through hand, belayer pulled violently etc) then you'll never reach the peak forces the paper is worried about.  I think it was Semmel who noted that he thought 5kN was a more realistic MAX an anchor could possibly see in high force, real world falls    

I do recall geometry based ABDs slipping around 2kN from Jim's belay device data. If the grigri slips at 4.5kN (don't remember from Jim's data) but also has high dependency on rope parameters, that doesn't make me feel much better given the lack of predictability for the belayer. The lack of emphasis on the flying belayer is the point; using a fixed point belay dramatically reduces the belayer displacement, making them more likely to hold a high factor fall. I agree that if the belayer can't hold the fall the forces will be lower as rope moves through the system, but just because the anchor isn't failing in that case doesn't mean everyone lives :/ As I recall, Semmel's assertion was based largely on his prior research and his intuition but was not explicitly tested. Granted, I think his intuition on this is highly valuable, but I would be happy to see something definitive. Regardless, the CAI and DAV also both recommend against a grigri for fixed point belaying.

Derek DeBruin · · Unknown Hometown · Joined Jul 2010 · Points: 585
mattm wrote:

I'm hoping Jim will chime in here as I can't recall specifics but if I recall correctly, GriGri's will slip around 4.5kN highly dependent on rope thickness and coating etc with others such as the AlpineUp more in the 2kN range.  So the forces found in their tied off scenario of 8kN seem unrealistically high given the fact even an ABD a device will start to slip before the peak loads found in their tied of scenario are reached.  I'm also not a fan of how little emphasis is given to the "flying belayer" syndrome or loss of control by the belayer in high impact falls.  They do acknowledge it yes, but for me this is the BIG gotcha.  IF the belayer can't hold the force (no glove, rope slipping through hand, belayer pulled violently etc) then you'll never reach the peak forces the paper is worried about.  I think it was Semmel who noted that he thought 5kN was a more realistic MAX an anchor could possibly see in high force, real world falls    

One more note about the 8kN number: with a redirected belay (i.e. the flying belayer), anchor force is 8kN, climber force is 4.5kN, belayer force is 3.5kN. In other words, even at 4.5kN slip for a grigri, it seems unlikely to slip as the 3.5kN on the belayer side is below that threshold.

Jim Titt · · Germany · Joined Nov 2009 · Points: 490

The CT video isn´t off the anchor, it´s off an extension from the climber who is free to move. Belaying off the anchor means the device is directly on the bolt/piton. It´s also dangerous advice because they don´t show what happens if the climber falls before the first bolt (i.e. takes a FF2 onto the belayer) as that type of device provide no braking force whatsoever in that scenario.
Learn to use a Munter dynamically straight off the bolt or belay conventionally off your harness, there´s no better solution.
The forces for the Munter in the paper linked are misleading, you cannot use a weight to reproduce a belayer hand force in dynamic testing, only in constant-speed pulls and so the results are invalid.

rgold · · Poughkeepsie, NY · Joined Feb 2008 · Points: 526
Jim Titt wrote: The CT video isn´t off the anchor, it´s off an extension from the climber who is free to move. Belaying off the anchor means the device is directly on the bolt/piton. It´s also dangerous advice because they don´t show what happens if the climber falls before the first bolt (i.e. takes a FF2 onto the belayer) as that type of device provide no braking force whatsoever in that scenario.
Yeah, the CT video has the Munter on a long cordelette anchor and the belayer cloved to the anchor. (The DAV calls this a "central point belay" as opposed to a "fixed point belay.")  With enough load, the belayer and Munter will be lifted above the anchor, negating one of the principal advantages of the direct anchor belay (its basically a harness belay).  

If you look closely at the video, you'll see that the  leader has clipped one of the anchor  bolts as the first piece.  This eliminates the factor-2 failure scenario for the device, but has its own problems.  First, the belayer is going to be pulled into that piece---if they don't get their hand out of the way there is significant injury potential.  Second, the pure factor-2 fall is going to load the anchor considerably less than, say, a 1.8 factor fall through the belay bolt.  For this reason, there are good arguments in favor of not clipping the anchor for the leaders first piece, and but then the device failure scenario Jim mentions is back in play. (Note that conventional harness belays with assisted and non-assisted tubes potentially have the same failure mode.)  The standard solution is to put another carabiner in the power point next to the device and redirect the brake strand through that carabiner until the party feels certain that a factor-2 can't happen.  But that redirection makes rope handling, especially pumping slack to a leader trying to make an overhead clip, clumsy at best.

Considering all these issues,
Learn to use a Munter dynamically straight off the bolt or belay conventionally off your harness, there´s no better solution.
With the additional consideration that one might use a hybrid of both methods as Derek describes in cases where a factor-2 fall near the anchor seems possible.
Fran M · · Cottbus, DE · Joined Feb 2019 · Points: 0
Derek DeBruin wrote:
Consider a hybrid system as recommended in the paper above: fixed point belay until there is bomber protection on the pitch, then switch to ABD off the harness. Not appropriate in every case, but can leave the ABD on the rope from the start of the pitch with adequate slack out so that the fixed point belay is backed up the whole time. 

ABD off the harness as the backup to the fixed-point belay? Then if the belayer looses control of the break strand in the fixed-punkt belay, she still gets pulled into the anchor, albeit with the reduction of the friction provided by the Munter Hitch. Also, the belayer needs to pay out slack through the ABD every 5m lets say, and that is a two hands maneuver.. I think its too cumbersome and does not eliminate the first reason for the fixed point belay: The lighter belayer getting hurt.

We tried tying loose overhands every 5 meters as backup but it also takes time and clutters easily. We also tried restricting the upward pull on the belayer with a piece connected directly to their belay loop, but when falling above the last bolt, the belayer still gets aggressively jerked.

Jim Titt wrote: The CT video isn´t off the anchor, it´s off an extension from the climber who is free to move. Belaying off the anchor means the device is directly on the bolt/piton. It´s also dangerous advice because they don´t show what happens if the climber falls before the first bolt (i.e. takes a FF2 onto the belayer) as that type of device provide no braking force whatsoever in that scenario.
Learn to use a Munter dynamically straight off the bolt or belay conventionally off your harness, there´s no better solution.
True, thanks for pointing that out. As rgold says, it is a "central point" configuration. Nevertheless, the locking motion of the device is the same as if it was clipped into the bolt directly, correct?

Concerning the dynamic belay by slippage, we have tried but haven´t been able to create a fall so strong that there is significant slippage. Will try again this week and try to record it. Anyway, in most of the "adventure" multi-pitch climbs I have done so far, one losses visual contact with the climber after maybe 2, 5 or 10m so a dynamic belay is unrealistic, isn't it? Just feel for slack and hold tight as a reflex if there is an unexpected pull. As a climber I don´t care if the catch is hard, I just want to be sure the fall is arrested and the belayer isn't hurt. More so when the pitches are up to 40-60m long!

Do you think that makes a good case for using the ABD directly off the bolt?

rgold wrote:Yeah, the CT video has the Munter on a long cordelette anchor and the belayer cloved to the anchor. (The DAV calls this a "central point belay" as opposed to a "fixed point belay.")  With enough load, the belayer and Munter will be lifted above the anchor, negating one of the principal advantages of the direct anchor belay (its basically a harness belay).  
I think the pull on the belayer should be less than in a harness belay because of the angle between the central point, anchor, and belayer's tie-in. Maybe not significantly though. Also, because the bealy device is lifted above the belayer, he stands a better chance of not losing control of the brake strands: He still needs to pull down, from above his waist line. When belaying from the harness and getting pulled into the first piece, the belayer has to pull downwards bellow his waist while this same region is getting sucked into the first piece. Not very ergonomic unless she can fly unobstructed (high first piece, or well lowered from the anchor as first piece).

Second, the pure factor-2 fall is going to load the anchor considerably less than, say, a 1.8 factor fall through the belay bolt.  For this reason, there are good arguments in favor of not clipping the anchor for the leaders first piece, and but then the device failure scenario Jim mentions is back in play. (Note that conventional harness belays with assisted and non-assisted tubes potentially have the same failure mode.)
Could you please rephrase this? This is my standard practice when using the ATC XP off the anchor, until the leader has clipped solid gear. The munter and the grigri do not need to be redirected because they brake in any direction. But double ropes with the Munter are too messy.

The standard solution is to put another carabiner in the power point next to the device and redirect the brake strand through that carabiner until the party feels certain that a factor-2 can't happen.  But that redirection makes rope handling, especially pumping slack to a leader trying to make an overhead clip, clumsy at best.
I have done this when the anchor is made of only one point (Saxony or Frankenjura). Clumsy, true. I opted for the munter in this cases. In this places the "leader shouldn't fall" rule applies anyway :P

Probably the most dangerous situation is when close to the anchor, but then a well placed belay station should not have really exposed and unprotected moves right off the anchor. And if so, I have seen a third bolt close enough to the anchor for the first piece (at least in Spain and Portugal).
climber pat · · Las Cruces NM · Joined Feb 2006 · Points: 241
Jim Titt wrote: The CT video isn´t off the anchor, it´s off an extension from the climber who is free to move. Belaying off the anchor means the device is directly on the bolt/piton. It´s also dangerous advice because they don´t show what happens if the climber falls before the first bolt (i.e. takes a FF2 onto the belayer) as that type of device provide no braking force whatsoever in that scenario.
Learn to use a Munter dynamically straight off the bolt or belay conventionally off your harness, there´s no better solution.
The forces for the Munter in the paper linked are misleading, you cannot use a weight to reproduce a belayer hand force in dynamic testing, only in constant-speed pulls and so the results are invalid.

Can you explain why "you cannot use a weight to reproduce a belayer hand force in dynamic testing"?  Is some type of clamp used instead?


Thanks
Jim Titt · · Germany · Joined Nov 2009 · Points: 490
climber pat wrote:

Can you explain why "you cannot use a weight to reproduce a belayer hand force in dynamic testing"?  Is some type of clamp used instead?


Thanks

Because if there is any slip through the device (there normally will be) the weight will be pulled upwards, that is it accelerates and force is mass times acceleration. If the weight is accelerated upwards by 1G then the 20kg is suddenly 40kg so you get completely wrong results. There are various clutch ideas used, mine is a rotating spool and a disc brake from a small motorcycle, it automatically adjusts to keep a constant force. The DAV one uses clamping plates.

climber pat · · Las Cruces NM · Joined Feb 2006 · Points: 241
Jim Titt wrote:

Because if there is any slip through the device (there normally will be) the weight will be pulled upwards, that is it accelerates and force is mass times acceleration. If the weight is accelerated upwards by 1G then the 20kg is suddenly 40kg so you get completely wrong results. There are various clutch ideas used, mine is a rotating spool and a disc brake from a small motorcycle, it automatically adjusts to keep a constant force. The DAV one uses clamping plates.

I see.   It is awesome how much I don't know or just don't think about correctly.  Thanks

Jim Titt · · Germany · Joined Nov 2009 · Points: 490
climber pat wrote:

I see.   It is awesome how much I don't know or just don't think about correctly.  Thanks

Don't worry, just look at your president........

rgold · · Poughkeepsie, NY · Joined Feb 2008 · Points: 526
Fran M wrote:

ABD off the harness as the backup to the fixed-point belay? Then if the belayer looses control of the break strand in the fixed-punkt belay, she still gets pulled into the anchor, albeit with the reduction of the friction provided by the Munter Hitch. Also, the belayer needs to pay out slack through the ABD every 5m lets say, and that is a two hands maneuver.. I think its too cumbersome and does not eliminate the first reason for the fixed point belay: The lighter belayer getting hurt.

The ABD is not there to back up the harness, it is there to provide a more fluid belay once the leader is out of factor 2 zone.  I've considered this specifically for half ropes.  Belay the leader off the anchor with both ropes in the Munter until out of factor 2 danger, then switch to ABD on harness so that ropes can be manipulated independently.

Concerning the dynamic belay by slippage, we have tried but haven´t been able to create a fall so strong that there is significant slippage. Will try again this week and try to record it. Anyway, in most of the "adventure" multi-pitch climbs I have done so far, one losses visual contact with the climber after maybe 2, 5 or 10m so a dynamic belay is unrealistic, isn't it? Just feel for slack and hold tight as a reflex if there is an unexpected pull. As a climber I don´t care if the catch is hard, I just want to be sure the fall is arrested and the belayer isn't hurt. More so when the pitches are up to 40-60m long!
What I think of as the dynamic belay is what the CAI calls the "inertial phase" in which the brake hand, while resisting, is pulled to the Munter carabiner.  Rope doesn't usually slip through the hand, although gloves are certainly a good idea.  This can be initiated by the belayer if there isn't enough force, allowing an anchored belayer to provide a "soft catch" in appropriate circumstances, but the primary use is to reduce loads in the ultimately bad factor 2 case.  You can be sure the inertial phase will happen with a factor 2 fall, and there are various internet videos illustrating this; it hardly seems necessary to test this again.

Do you think that makes a good case for using the ABD directly off the bo
No, you have to redirect the brake strand, which I find clumsy.  Moreover, the behavior of ABD's under high loads is very suspect according to tests by Jim Titt.  Even with the redirected brake strand, not only might there not be a locking reaction, but the amount of friction provided could be less than if you had used an ATC.

Could you please rephrase this? This is my standard practice when using the ATC XP off the anchor, until the leader has clipped solid gear. The munter and the grigri do not need to be redirected because they brake in any direction. But double ropes with the Munter are too messy.
Because of the pulley effect, a high fall-factor fall (eg 1.8) held with the leader's rope clipped to the anchor is going to load it with considerably more force than a factor 2 fall onto the anchor without a pulley configuration.  If the plate is installed on a lower anchor piece, that will avoid the collision problems I mentioned.
Fran M · · Cottbus, DE · Joined Feb 2019 · Points: 0

Rgold, thank you for your detailed reply.

I reached out to Climbing Technology and explained my query quoting the video and this illustration from the CAI:

source: CAI - Classic vs Harness belay

Their repy:
Si, è possibile anche assicurare il primo di cordata con l'Alpine Up collegato all'anello di sosta. Ma NON DIRETTAMENTE A UN CHIODO (BOLT) come nella figura 3 ma sempre a una sosta costruita con CORDINO E FETTUCCIA (fig. 1 - 2). Questo perchè non bisogna far lavorare metallo su metallo (es. moschettone dell'Alpine UP con altro moschettone o direttamente in un ancoraggio. La figura 3 è adatta solo all'uso con un nodo mezzo barcaiolo.
In English:
Yes, it is possible to belay the leader with the Alpine Up attached to the central point BUT NOT DIRECTLY TO A BOLT like in figure (3) but always through a central point built with a cord or tape (fig. 1 - 2). This is to avoid a metal-on-metal interaction (specially the carabiner of the Alpine Up with another carabiner or directly to an anchor point). Figure 3 is only adequate for a Munter hitch.
The reply is a bit unclear, as it would be trivial to incorporate a soft link between the bolt and the carabiner of the alpine up in the configuration of figure 3 (series connection) to avoid metal on metal interaction.

I imagine the CAI presentation I quote above is based on this very comprehensive article: CAI - Belay Methods where the inertial phase is well explained.

On the transition from fixed point to ABD belay, you belay with both ropes through the same Munter hitch? (shall we start calling it Italian hitch at least, at this point?)
If so, does the climber clips both ropes through the first piece?
I could imagine belaying with the Italian hitch off the master point until the high factor fall is not likely anymore and then switch to the (previously set) ABD also on the master point.
Guideline #1: Don't be a jerk.

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