Backing up rappells: Who does it?

bearbreeder wrote:prohaska-hedden under load 10mm dynex sling on string

daayyyyyuuuuum.
that's the king of friction hitches

9 pages and Im not sure if anyone saw this, from this very website! mountainproject.com/v/how-t…

"4. Back up the Brakes: While there are many ways to back up rappels, the best I’ve seen is a friction hitch, sliding along the rope(s) itself below your brake hand. (Rock Climbing: Mastering Basic Skills, by Craig Luebben, is an excellent book for this tip and others like it; order at mountaineersbooks.org.) It takes about five seconds to rig and doesn’t lessen the rappel “experience.” When rapping in a storm in Cody, Wyoming, my partner lost control of the slippery 9mm ropes. However, with a friction hitch in place, he averted disaster, quickly righting himself and carrying on after the knot checked his slide. "

So there ya go. Says its the best, and says he saw someones life saved by a friction hitch. There, that should lay the matte to rest. I dot foresee any more posts on this.

csproul wrote: I've never used one above the device. I use it below on the leg loop and have tried it on the belay loop too. I use more like 4mm. I'm not sure I'd trust 6mm to reliably grab a single rope and you said you'd seen it slip. I've let go of the rope with a 4mm backup many times and it has never slipped any amount. I do agree that a reliable backup is probably more sensitive to a variety of setup factors and mostly people are unaware of whether or not it will work since few ever actually test the system under realistic conditions. Edit: I'd have to look at the cord that I use to be sure if it's 4mm or perhaps 5mm, but certainly smaller than 6, especially with a single strand.

Uh what? The general rule of thumb in rope access and rescue is no less than 70% of the rope diameter for a single line rap. On top of that, a 6 wrap prussik with 6mm cord fails at a lower amount of force than a paltry 4 wrap prussik with 8mm cord in a test carried out by some arborist gear manufacturers. I dunno I'm a rope access/climber guy.

Friction hitches rely on surface area. If you 12 wrap that 4mm cord of yours, you might be able to apply more surface area onto your rope, but do you want to dress a 12 wrap prussik with 4mm every pitch? A higher number of wraps with a thinner cord is also harder to dress, free up, manage during your rappel, and will be more likely to glaze your rope or become tangled once it activates.

Also, keep in mind the abrasion resistance of a thin cord is much lower and the materials used are probably not made of materials for high-heat applications like backing up a rappel. Aramid is ideal, polyester ain't bad. Nylon melts at about 420f.

Another thing...

You guys might want to check this link out.

blog.alpineinstitute.com/20…

I see a lot of you are using your leg loop as an attachment point to back up your rappel.

I've done my own, very crude tests on this and I was able to open up my leg loop with a 75lb proof mass, and a 4 by 5', 1.25" pulley, 10ish degree v-angle drop on 10.2mm dynamic rope about 3/10 times. There's a lot of variables here that are beyond my mathamagical ken. All the same, I can't imagine it would be hard to summon those gravitons and graviolis during an uncontrolled rappel.

Last point and I'm done: Why are you guys putting your friction hitch below your atc in the first place? How do you make a friction hitch slip? You apply downward pressure and it slips. What happens when you load your friction hitch and then it smacks into your atc? It experiences downward pressure. Is it really that much of a convenience to have both hands on your break end? No one that gets on ropes professionally would ever use this configuration. Friction hitch backup above ATC always please...

Screw all other knots, yer gonna die if youre not using this one and ONLY this one.

climbing is NOT rope access ...

youtube.com/watch?v=cYtYLJz…

other than for a knot pass there is absolutely no reason to use a backup above the device for recreational climbing ... the "modern climber/canyoneer" often has shiet rope skills and cant even escape a stuck prussic above the device as evidenced by the video above

keeping both hands below the device is absolutely critical when not using a backup ... and the same habits will carry over, so if one keeps one hand above the device when using a backup, theyll often do the same when not

would anyone here lower a climber with one hand above the device above an ATC? ... if you do go off and learn the modern way to lower soneone (the sole exception is when theres so much friction you need to feed out the rope)

the arguments over whether to use a backup and to use it above or below have been going on for decades

storrick.cnc.net/VerticalDe…

caves.org/section/vertical/…

MP is just regurgitation

but its something we all prefer to do rather than actually go out climbing

;)

Gription, thinking to mess around with leg wraps, this evening I brought my Purcell's to the university gym I go to (so I could ascend two rope strands just high enough to hang free of the ground). This was the second time I've done ascending there. Tonight, most of the folks were very new, so it's reasonable that they had no clue what I was up to, and a few were very interested. Earlier in the summer though, only one person had used a friction hitch (a staffer who used Purcells when working on stuff in the gym). My impression was that pretty much none of the others had seen or heard of a prussik hitch, any friction hitch, really, or what you might use one for, including folks who are sport climbing outside pretty regularly. I hate to say it, but I'm afraid part of your answer is people not being taught a backup at all, or that's it's just a "maybe" to consider. Brand new climbers learning from pretty new climbers. And, if you don't see any of your crowd doing so, how likely are you to back up?

FYI all, tying the Prussik tonight probably took ten seconds, maybe less.

Disaster Franklin wrote: Uh what? The general rule of thumb in rope access and rescue is no less than 70% of the rope diameter for a single line rap. On top of that, a 6 wrap prussik with 6mm cord fails at a lower amount of force than a paltry 4 wrap prussik with 8mm cord in a test carried out by some arborist gear manufacturers. I dunno I'm a rope access/climber guy. Friction hitches rely on surface area. If you 12 wrap that 4mm cord of yours, you might be able to apply more surface area onto your rope, but do you want to dress a 12 wrap prussik with 4mm every pitch? A higher number of wraps with a thinner cord is also harder to dress, free up, manage during your rappel, and will be more likely to glaze your rope or become tangled once it activates. Also, keep in mind the abrasion resistance of a thin cord is much lower and the materials used are probably not made of materials for high-heat applications like backing up a rappel. Aramid is ideal, polyester ain't bad. Nylon melts at about 420f. Another thing... You guys might want to check this link out. blog.alpineinstitute.com/20… I see a lot of you are using your leg loop as an attachment point to back up your rappel. I've done my own, very crude tests on this and I was able to open up my leg loop with a 75lb proof mass, and a 4 by 5', 1.25" pulley, 10ish degree v-angle drop on 10.2mm dynamic rope about 3/10 times. There's a lot of variables here that are beyond my mathamagical ken. All the same, I can't imagine it would be hard to summon those gravitons and graviolis during an uncontrolled rappel. Last point and I'm done: Why are you guys putting your friction hitch below your atc in the first place? How do you make a friction hitch slip? You apply downward pressure and it slips. What happens when you load your friction hitch and then it smacks into your atc? It experiences downward pressure. Is it really that much of a convenience to have both hands on your break end? No one that gets on ropes professionally would ever use this configuration. Friction hitch backup above ATC always please...

The larger the difference in diameter between the cord used to make the hitch and the diameter of the rope the hitch is applied to, the more friction. The closer the diameters, the lower the friction; ie smaller cord has more friction..right?

There's probably lots of things that climbers do that don't pass mustard to professional riggers. I can tell you that ~3-4 wraps with a 4-5mm cord is more than sufficient to stop me on a single or double ~9-10mm rope (hitch on my leg loop below the rap device). I can completely let go of the brake hand mid rap and I will come to a complete stop. No slipping. The hitch (I use an autoblock) does not hit the ATC, especially if I extend it. The ATC does not apply "downward pressure" and cause slippage. I've tried to make this happen and it just doesn't happen. 12 wraps are definitely not required.

Thanks though for the info about the location relative to the leg loop buckle. That is an easy change to make with no downside that I can think of.

bearbreeder wrote:climbing is NOT rope access ...

Man, just about absolutely everything you can visually see in that video is a disaster waiting to happen...

for those MPers who want some more historical context .... rather than arguments about who can breed the largest fuzziest beahs

note that larry penberthy, founder of MSR, is generally the person credited with coming up with using a backup BELOW the device

article by Gordon Birkhimer, Bat News 2006

Genealogy

The use of a self-belay when rappelling can be traced to
mountaineers, arborists, and rock climbers, who developed
and successfully employ a variety of rappel safety systems.
Climbing books have detailed the development of both
mechanical and self-belay rope rappel safety systems that
are effective. Mike “TinY” Manke introduced the French
Wrap, or Autoblock, to me as part of the Basic Vertical
Training as designated by the Vertical Section of the
National Speleological Society. The self-belay he taught
me employs a friction hitch the French properly refer to as
the noeud Machard or Machard Knot. The knot was named
for the old French mountaineer who developed it. Given the
choice, I would call it the Machard Hitch because a hitch
makes a rope hold fast to another object, in this case the main
rappel rope. The jargon in the world of rope can be rather
confusing. The most accurate terminology for the
arrangement I use would be, “The French Wrap Self-Belay
Rappel Safety System with a Machard Hitch as the
Autoblock.” To simplify things I have accepted the name
“French Wrap” and use that as the common expression.
Many climbing books show the Machard Hitch as a
rappel safety, and they refer to it as a French Prusik or an
Autoblock. Those two terms may cause some confusion to
the reader. The term French Prusik can be problematic
because there are several different hitches with the same
name. Also, a French Prusik is not the Prusik Knot as we
know it. The term Autoblock is not a specific knot, but rather
a generic term taken from noeuds autobloquant. This is a
term for an entire class of friction hitches used to grip a rope
and when translated means Selfblock or Autoblock Knot.

The most common hitches in this group are the Prusik,
Machard, Braid (Plaited), French Knot, and the Valdotain.
There are several other friction hitches in common use by
climbers, such as the Hedden, Bachmann, and RBS.
I suspect the terminology used in climbing books may be
responsible for some of the ambiguity prevalent in the
caving community regarding the self-belay rappel safety.
For instance, a caver reading a climbing book may not
realize that “French Prusik” refers to a Machard Hitch and
not to a Prusik Knot. In practical application, the Machard
Hitch works well as a self-belay rappel safety, while the
Prusik Knot performs poorly because once loaded, it is
impossible to loosen unless all weight is removed.

Larry Penberthy first described the technique of using a
rappel safety fashioned from rope and positioned below the
rappel device in the article, “A Method of Securing a
Rappin’ With The French Wrap
Rappel,” in On Belay magazine, No. 16, August 1974. In
the article, he recommends either a "Penberthy Knot" or a
"Penberthy-Pierson Knot,” which was a reinvention of the
Helical Knot, also known as the Ascender Knot, or noeud
Valdotain. Although the knot Penberthy used is different,
the rappel safety system he describes is arranged exactly the
same as the Machard Hitch self-belay method that I
recommend. Penberthy accurately explained: “If the
climber lets go with his braking hand completely, the knot
grabs and stops him. If he grips the control knot tightly in
panic, the extra braking friction force stops him.” Penberthy
also correctly cautioned: “The security knot must not be able
to touch the rappel device. If it does, the security knot will
not grab.”

Historical Failures

The negative beliefs regarding the early self-belay systems
involved two problems. Problem number one has two parts
and resulted from using the wrong hitch for the job and
attaching it too high on the rope. A Chest Safety Prusik Self-
Belay System is a good example of this problem because
once the Prusik Knot was engaged, it was out of reach and
difficult to release until the weight of the rappeller could be
removed. And if the knot was positioned just below the
rappel device it could be sucked up into it. Mechanical
devices, such as the Gibbs ascender, Safety Rappel Cam,
Petzl Shunt, and the Spelean Shunt were all tried as a high,
second point of attachment with less-than-rave reviews.
Mechanical devices can run the risk of severing the main
rope when put under the stress of a high fall factor. If the
rappeller becomes out of control and suddenly engages a
mechanical device, it can cut the rope.

Problem number two resulted from a phenomenon
known as “negative action.” In order for these early systems
to work, the rappeller had to relax his/her grip on the Prusik
Knot or mechanical device in order stop descending. As you
might imagine, when accelerating out of control down the
rope, victims are inclined to grasp tighter, thereby defeating
the purpose of the self-belay, and falling unimpeded until
impact. These negative action rappel safety systems began
to be associated with accidents and they lost their appeal.
Many of these early attempts of self-belayed rappels
resulted in hopeless entanglements, injuries from improper
use, and even death. As a result of the problems encountered
with the first systems, cavers decided that self-belaying
while rappelling was not practical or safe, and should not be
encouraged or recommended. Cavers mainly relied instead
on bottom belays.

Renaissance

The fact that the caving community was trying to develop a
satisfactory self-belaying system indicates they understood
the logic of adding a second point of attachment to reduce
rappelling risk and accidents. Many years after those first
trials, cavers again began exploring ways to self-belay a
rappel, focusing on ways to avoid the problems encountered
by their predecessors. Finally there was a breakthrough, and
we now have a reliable, effective system to protect
rappellers. The self-belay innovation used two new
concepts: a lower fixed point of attachment and a more
effective friction hitch, or Autoblock.

A life-supporting webbing loop is sewn directly to the
leg loop on a seat harness, and a carabiner is attached. It is
best to sew the carabiner webbing loop to the side or slightly
toward the rear of the leg. A sewn carabiner webbing loop
should be used instead of simply attaching a carabiner to the
leg loop, because a carabiner tends to ride forward around
the leg loop toward the rappel device. I believe wrapping the
webbing loop around the leg loop and sewing it is much
stronger than just sewing it on the outside surface of the leg
loop.

A Prusik loop (note I am saying loop instead of knot)
constructed of 8mm accessory cord is connected to the
carabiner, and used to create the French Wrap with a
Machard Hitch. The French Wrap is operated with the
braking hand, which is relaxed on the hitch at the user's side
near the leg loop. In this configuration, the hitch should
never ride closer than 12 inches to the rappel device. The
Machard is the right hitch because it engages properly and
releases easily with the slight pressure of two fingers.
The earlier insurmountable problems associated with
using the wrong knot and the higher attachments from the
chest or seat harness are now solved. The low point of
attachment ensures that the French Wrap will not become
entangled in the rappel device. It also ensures that, by not
reaching the rappel device, the hitch will catch properly and
stop the rappeller in an out of control situation. Just as
Penberthy elaborated, if the hitch does come in contact, the
rappel device will actually be pushing, or “minding” the
self-belay system down the rope. Because the French Wrap
never comes close to the rappel device, it is a successful
system, and the first problem is solved.

The second problem was the issue of negative action.
The French Wrap is not a negative action self-belay rappel
safety system. To descend freely, place your hand above or
on the hitch, and push or hold the hitch at your farthest reach
down the rope – the position of the hitch on the rope controls
the rappeller's speed, rather than pressure on the hitch.
When the hitch moves up the rope, it tightens on the rope and
begins to slow your descent. The relationship of the
position of the hitch to the speed of rappel is easily mastered.
If you let go of it, say after being hit on the head with a rock,
you will stop. If you push the hitch up the rope as high as
possible, you will stop. Grasping the hitch with the strength
of white-knuckle fear will also slow the speed of descent
through friction. Therefore, I believe that the problem of
negative action is inconsequential when using the French
Wrap and the second problem is
solved.

Eliminating the two original
self-belay problems was
instrumental in developing a
successful self-belay rappel
safety system. However, I must
emphasize that the French Wrap
is not a Hail Mary air brake
guaranteed to preserve life for
those too lazy to learn the skills
required. It is mandatory that
each user takes the time to
acquire the knowledge, skill, and
experience necessary to operate
the system. There are hundreds
of types, sizes, and diameters of
rope, and all behave differently.

The conditions of the rappelling
rope, such as age, moistness, stiffness, and cleanliness, also
dictates its behavior. For example, a new rope is faster than
an old muddy one, and the French Wrap may need to be
adjusted to obtain optimum performance. My experience
has been that four wraps around the main rope are usually
adequate. On the other hand, the French Wrap may require a
fifth wrap on new or smaller diameter rope to be effective.
It's important to be aware of the existing rope factors and to
understand how best to adjust the French Wrap according to
those variable rope conditions. There are no shortcuts, but
with training and practice, you can easily gain the skills
required to employ the French Wrap.

youtube.com/watch?v=cYtYLJz…

bearbreeder wrote:...other than for a knot pass there is absolutely no reason to use a backup above the device for recreational climbing ...

Yup. Back in the day when people sometimes rappelled off just a swami belt (no leg loops) a prussik knot above the device killed at least one person when the knot jammed and the rappeller suffocated. All he had to do was invert, but he didn't know about that. This wouldn't happen today because of harnesses, but the point is that only knowing one way to do things and not knowing how to deal with unexpected system behavior can be fatal.

In the video, the woman rappelling ultimately had a knife lowered to her and she cut off the prussik backup. If she was in a situation where that help from above couldn't be provided, what would have happened to her? And whew! Nothing scarier then slicing things with a knife right next to a tensioned rappel rope. That too has killed at least one person.

And then she's rappelling without a backup after an exhausting session fighting the prussik. I do think she knew about leg wraps, which would have been required for even a hint of safety when sawing away with a knife, a process that probably required both hands to make sure only the prussik sling got sliced.

The old-timers have known about the dangers of a prussik above the device for many years, but ignorance about the problem seems to persist. Moreover, it has been known for many years that if you use a friction knot above the device and something knocks your brake hand off, the fact that you are gripping the friction knot with the non-brake hand means this "backup" will never lock and you're going for your final ride. This has been tested and found to be true even when the rappeller knew the brake hand would be lost as part of the test. So whatever caused you to release the brake hand had better have knocked you out, otherwise you had no backup but didn't know it.

We've also known for many years that the solution to the knot below hitting the device is to extend the device, which is a good idea anyway even if you aren't using a backup knot. People regularly chose not to extend the device, and check that the knot won't hit the device while standing up straight. In any kind of accident, the chances are that the legs will be drawn up, and then the knot that won't hit the device does. I know of at least one fatality from this.

So please, folks, if you aren't going to extend, at least check your setup clearance from a seated position, and even then be very wary of raising the leg with the autoblock on it, as you might when maneuvering to clear a tangle. Better yet, back up the autoblock with leg wraps and leave the autoblock by itself for strictly emergency duty.

Bearbreeder called this "regurgitating," and it does seem that way when this knowledge has been around as long as it has. I console myself with the hope that someone will be helped by some of this. I surely have no other reason for making the effort.

Really, I think one of the messages emerging from the discussion (besides the fact that faulty logic will get you whatever answer you were hoping for) is that it is important to understand the system you are using, what its drawbacks and gotcha's are---because absolutely nothing is foolproof---and then know alternative ways to do things, whether it be types of knots or methods of setting up, so that when something you never anticipated makes your preferred system ineffective, you aren't in a critical situation with no options.

I know bearbreeder would add that if you don't practice those alternatives, they may not be available to you if it happens that you need them, or perhaps worse you'll "remember" them but get something about them wrong.

A rather long thread, so why not add my worthless two cents.

I was in mixed minds regarding no backup, extending and backup below device, or not extending and backup off leg loop. Thinking extending and backup below was probably safest, but also the most faff and complexity.

I spent two days just rapping recently. A few couple of thoughts and observations:

- One person rapping had a prussik below the device that was far too long. They said it was OK, as their hand was stopping it from hitting the device. :(

- Extended devices are more likely to get stuck on the lips of roofs, leaving your feet on the lip for as long as possible helps prevent that, but sometimes you f*ck it up anyway.

- When the rope runs over some sharp looking thing, or the anchors aren't all that confidence inspiring, smooth is good. Backups are the enemy of smooth [see next comment]

- Getting the backup running just right is not a given. Too much friction is too slow and jerky, not enough and it might not catch. You can tweak the number of turns, sure, but change ropes or prussiks, and you'll have to rework it out on the first pitch. You also have to account for the weight of the rope below you changing, affecting the friction (halfway down I did get annoyed enough to remove a backup)

- Despite being paranoid about safety, the local caving club I used to frequent only did fireman belays in uncommon circumstances (eg: learning to rap) and didn't install backups above or below the devices. Sometimes the devices that ran quite fast were used (eg: bobbins).

- On reflection of the clusterfuck of trying to untangle ropes on a windy day that never made it to the ground, rather than worry about backups I think the safer option would have been just abseil with the ropes in a sack hanging off me.

- Complexity correlates with mistakes

Unless something compels me otherwise, my current default is no backup. Sure, if I let go there's a problem. Just like with every lead fall, or partner lower off we do. So I don't let go.

bearbreeder wrote:climbing is NOT rope access ... youtube.com/watch?v=cYtYLJz… other than for a knot pass there is absolutely no reason to use a backup above the device for recreational climbing ... the "modern climber/canyoneer" often has shiet rope skills and cant even escape a stuck prussic above the device as evidenced by the video above keeping both hands below the device is absolutely critical when not using a backup ... and the same habits will carry over, so if one keeps one hand above the device when using a backup, theyll often do the same when not would anyone here lower a climber with one hand above the device above an ATC? ... if you do go off and learn the modern way to lower soneone (the sole exception is when theres so much friction you need to feed out the rope) the arguments over whether to use a backup and to use above or below have been going on for decades storrick.cnc.net/VerticalDe… caves.org/section/vertical/… MP is just regurgitation but its something we all prefer to do rather than actually go out climbing ;)

Yeah rope access way way over the top with regards to safety. Two static (low stretch) ropes, 2-4 secure attachment points on the rope at all time, a $250 idiot proof grigri, and so on.

But the additional testing, evaluation required to meet workplace safety represents a good alternative perspective on safety in a vertical environment. I would encourage all of you guys to cross-pollinate with rescue/arborist/rigging workers and resources because you learn cool shit. Also dumb shit.

As far as two hands on the brake end goes, yeah I guess that's how I should be doing it. There's clearly no downside. But I'm always a little wary of my friction hitch crashing into my atc. I guess the solution is to use the shitty sterling 6.8mm hollowblock aramid sewn prussik above the atc because it grips for shit and doesn't need to be minded no matter how well you dress it.

csproul wrote: The larger the difference in diameter between the cord used to make the hitch and the diameter of the rope the hitch is applied to, the more friction. The closer the diameters, the lower the friction; ie smaller cord has more friction..right?

Sorta. It has a lot to do with how pliable the cord is, what it's made of, the condition of the rope and of the cord. 70% of rope diameter works well because too thin can cause the friction hitch to coil over itself, cause glazing damage when loaded, become so tightly locked to the rope you have to go hands-free to deal with it. the theory behind the sterling is that it's highly heat/abrasion/cut resistant (aramid is a class of uber-nylon, kevlar, nomex, and technora are aramids.) floppy, and it's rectangular cross-section gives it more surface area in a smaller package. It just doesn't seem to come together because 6.8mm would require more than the maximum 3 or 4 wraps, and it's not long enough for that.

There's probably lots of things that climbers do that don't pass mustard to professional riggers. I can tell you that ~3-4 wraps with a 4-5mm cord is more than sufficient to stop me on a single or double ~9-10mm rope (hitch on my leg loop below the rap device). I can completely let go of the brake hand mid rap and I will come to a complete stop. No slipping. The hitch (I use an autoblock) does not hit the ATC, especially if I extend it. The ATC does not apply "downward pressure" and cause slippage. I've tried to make this happen and it just doesn't happen. 12 wraps are definitely not required.

Thanks though for the info about the location relative to the leg loop buckle. That is an easy change to make with no downside that I can think of.

The idea behind the friction hitch rap backup is not to hold your weight while you enjoy the view, it's to prevent the worst case scenario, you let go of the brake strand for whatever reason and rapidly build speed at near freefall. 4-5mm cord will catch if you use an appropriate friction hitch, but as I mentioned above, bad things could happen to that cord or your rope.

No prob on the leg loop tip. One of the manufacturers put out a notice IIRC a couple years ago.

And guys, I'm not an expert at this stuff. I've been climbing for just a few years. I went out and did my own trials, but a new climber's vim and vigor < decades of experience. Do your own research, and testing. Have an open mind. I've even learned some cool tricks from the climber's sworn enemy, the canyoneer.

Drop tests are easy to set up at home. Personally, I'm gonna probably play with some of Bearbreeder's great content up there. Thanks for the super post, bro.

rgold wrote: /

Rgold, comparing the danger of keeping your hand on top of your prussik is like comparing the danger of pulling the decamming lever on a grigri. Ya just let go. However, there's at least one rope access guy that died or got badly injured after grabbing his petzl shunt. You're right about extending the atc, that would probably be the best of all options. Suffocation isn't much of an issue these days, unless you're bringing the swami out of drydock, but the phantom of suspension trauma, whatever the fuck that is, remains. I'm gonna let all of this soak in. Thanks for the post mate.

Disaster Franklin wrote: ...The idea behind the friction hitch rap backup is not to hold your weight while you enjoy the view, it's to prevent the worst case scenario, you let go of the brake strand for whatever reason and rapidly build speed at near freefall. 4-5mm cord will catch if you use an appropriate friction hitch, but as I mentioned above, bad things could happen to that cord or your rope...

There is no free fall. I can rap at normal speed and spontaneously let go of my brake hand at any time and the autoblock catches. I've tried it. There is no sliding. No "rapidly building speed". If there is any sliding without being tended by hand, the autoblock is too loose.

PS as I said upthread, the cord I use may be 5mm, I may have been wrong when I said it was 4mm, but I'm not entirely certain without getting it out and looking.

Disaster Franklin wrote: Rgold, comparing the danger of keeping your hand on top of your prussik is like comparing the danger of pulling the decamming lever on a grigri. Ya just let go.

The problem is, you don't "just let go". The natural panic reaction is to grip tighter. This has been tested, with experienced people, and a consistently large number of people, even when prepped, don't let go.

As bearbreeder's large quote explains, if you have a knot below your device and let go, you're fine. If you grip tighter, you're still fine, because then you're gripping tighter on the rope below your rappel device, and that will also slow-down/stop you.

csproul wrote: There is no free fall. I can rap at normal speed and spontaneously let go of my brake hand at any time and the autoblock catches. I've tried it. There is no sliding. No "rapidly building speed". If there is any sliding without being tended by hand, the autoblock is too loose.

I want to know if people are just hauling on raps or what? I just go slow and never have ahad an issue with a 5mm autoblock.

I don't like speed rapping and bouncing all over the place though.

In 35 years of climbing, I have never backed up my rappel. Just lucky, I guess.

David Gibbs wrote: The problem is, you don't "just let go". The natural panic reaction is to grip tighter. This has been tested, with experienced people, and a consistently large number of people, even when prepped, don't let go.

My memory is that the test was set up so that a belayed rappeller went off the end of the rope. The above-device prussik was attached to a second parallel rope that was much longer, so that the prussik would have plenty of time to engage if activated. The subjects knew they were going to go off the end of the rope they were rapping on and knew that they had a belay. Nonetheless, most or maybe all, I don't recall, were unable to release the prussik and have it engage; they had to be stopped by the belay.

Extrapolating to someone taken by surprise, there is almost no chance that an above-device prussik will keep a rappeller who has lost control from falling unless, as I said earlier, they have been rendered unconscious. They won't be letting go otherwise.

The above-device prussik has some uses, but is clearly inferior as a safeguard against accidental loss of control. Moreover, the prussik may be the wrong knot for the job because it its tendency to jam, sometimes ferociously as in the video clip.

If you are going to backup your rappel, I think you want an extended device and the knot below the device, placed so that no body contortion can possibly produce a knot-device collision. Probably the best place for the knot is on the harness belay loop, which eliminates any question of failure due to leg-loop buckle release, is less likely to collide with the device if the (unconscious) rappeller inverts, and allows for comfortably and naturally having both hands as brake hands.

The relatively small price to pay for the extension is, as mentioned by rm, that the extended device can grate over the lip of ceilings. Actually, rm suggests the device can "get stuck" doing that but I've never seen a situation where that could happen. It can also be more awkward to get started if the anchor is really low.

Parker Wrozek wrote: I want to know if people are just hauling on raps or what? I just go slow and never have ahad an issue with a 5mm autoblock. I don't like speed rapping and bouncing all over the place though.

Also, I would think that a fast rap would be kinda rough on your rope, what with the sharp bend at the atc/biner interface choochin' through at 88mph.

rgold wrote: If you are going to backup your rappel, I think you want an extended device and the knot below the device, placed so that no body contortion can possibly produce a knot-device collision. Probably the best place for the knot is on the harness belay loop, which eliminates any question of failure due to leg-loop buckle release, is more likely not to collide with the device if the (unconscious) rappeller inverts, and allows for comfortably and naturally having both hands as brake hands.

Yeah, this right here. I think this should be canon, even though I do it YGD style.

csproul wrote: There is no free fall. I can rap at normal speed and spontaneously let go of my brake hand at any time and the autoblock catches. I've tried it. There is no sliding. No "rapidly building speed". If there is any sliding without being tended by hand, the autoblock is too loose.

There are so, so many variables that will increase the amount of time it takes for a friction hitch to hitch.

First of all, let's talk about what a well-dressed hitch looks like. A bit off topic but here are some pictures of a fig8 on a bight. One is dressed correctly, one is not. Can you tell which one?



ignore that it's not tightened all the way. One is actually incorrect. True story. And that's easy-mode, the easiest knot to visually inspect. Now the improperly dressed knot is irrelevant to our happy fun times, but it does make the rope a little easier to untie when done properly.

CSproul. It's obvious you've got your shit figured out what with the friction hitch backups and such, and you caught me playing devil's advocate a bit.

This might be a bit pedantic, and I'm sorry in advance, but here's a list of things that make friction hitches slip before choochin'. Most of you already know this but just in case:

Rain
Mud
Mist
High humidity
Dirt
Urine
Cheesegrater fall
Carabiner profile and orientation
New ropes with teflon dry coat
Elongation of the rope toward end of long raps(load increase/time is stretched)
Stiff cord
Cord that is too thick or thin
Cord with any high-lubricity fibers in the sheath
Cord that has a nylon sheath and is glazed from repeated loading, but still passes visual inspection
Temperament of the Gods
Inability to visually inspect because the sun went down faster than usual
Haste
Single rope simul-rap compounds all of the above

But if you're doing everything right and you've got the right gear on the right day, then you're 100% correct on hitch activation.

David Gibbs wrote: The problem is, you don't "just let go". The natural panic reaction is to grip tighter. This has been tested, with experienced people, and a consistently large number of people, even when prepped, don't let go.

I'm aware of this, as I mentioned in my related story about the petzl shunt. Some people died or got hurt over the 30 year career of the shunt in rope access. Not many, but Petzl decided to declare (secretly at first) that the shunt should not be used as a backup device.

ropebook.com/industrial/new…

The Kong, however, has the same issue. If your main line breaks or what have you and you instinctually grab the kong, it may fail to engage for the same reason as the shunt. But it's still widely used by both SPRAT and IRATA, even though it sucks dicks. We can use 4 wrap 8mm prussiks too, and you know how ridiculous the standards for rope access safety are. I keep up to date on the climbing accident reports and I don't think I've ever seen one involving a person grabbing their prussik and falling to the deck.

You're still right. It is a risk. It can be easily mitigated. But let me quote every booklet from every piece of gear I've ever bought. "Warning. Rock Climbing is Dangerous!"

On a personal note, I just give it a little pinch from the top. If you were to suddenly plummet, even with your hand on the top, gravity will kick in and bring your hand onto or below the hitch. At least I would think. That's probably why Hitch up/atc down accidents are rare.

RockinGal wrote:In 35 years of climbing, I have never backed up my rappel. Just lucky, I guess.

Same here. I've got the same amount of years in as you do - when we learned, it just wasn't something people did. Not that I ever saw anyway. Don't tie knots in the ends of my rap rope either, guess we're just crazy that way.

When I learned to drive, none of us ever wore seatbelts. Never did get into an accident. Guess I'm just lucky that way.