Rope Too Short? What Can You Do?

To quote Mad magazine: "Thimk"

This. Long enough for that initial shock and the first rush of adrenaline to ease off. I know can't think very clearly until that happens.

This is something I do as well (in practice sessions though I clip into loops on a separate dynamic rope).

Lately, however, I've been wondering just how painful that catch will be when the rope is static.

If OSHA standards are any guidance then we should limit fall forces to 4 kN to avoid serious injury (for a waist harness, full-body harness is 8 kN I believe https://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=STANDARDS&p_id=9730).

I wonder how far one would have to fall to exceed that limit? The answer will vary based on how much rope is between the ascending human and the anchor/ledge. For kicks -- if someone wants to crunch numbers and report -- lets say there are 10 meters of rope between your backup knot and the anchor above and the rope is 8.3 mm Canyon Fire (Elongation at 390 lbF: 1.2%).

Of course I'd rather fall 10 feet on a static rope than 100 feet onto sandstone... but will I be dangling from a rope with a broken back and my aorta separated from my heart?

P.S. I wonder... would a Yates Screamer help this situation to a degree where it is useful?

Yates screamer help?
Yes, but it is more GACK.
Why bother to carry it? Solve the problem by carrying REAL ascending gear.
VT Prusick, Ti BLocks,
Micro Traxion
Also have a RAPPEL device that you can lock off in a 'jiffy' (shameless CRITR2 plug)
As for falling on a static rope: DON'T!

there are some complicated answers to this conundrum, but at some point, I have to ask myself if the complexities of all these techniques - and the need to apply them under extreme duress- start to override the original reason for going out into the canyons in the first place. Originally, it was for the beauty, solitude, and adventure. I don't want that part of the experience to get overshadowed by the fear, adrenaline, stress, and complexity of needing to know and apply all sorts of techniques when I am hanging 100 feet off the ground.

As for my answer to this, it is a heck of a lot easier to sit on a computer and think of it compared to hanging off the deck under that kind of stress. Having said that, I think I would go single strand and make sure I can see or hear the rope bag hitting the bottom. Use a contingency block if I can't. Take my Microtraxion, Tibloc. and webbing footloops with me and hope I don't need them. If I do need them, I know I can lock-off (easy on the CRITR) transition my weight to my ascending system (easy with Purcell Prussic tether), and climb back up. It sounds easy in theory and I have done it (a few times) in practice, but not under extreme duress. I hope I never have to....

edit: only use DRT when I can see the bottom and know for certain both ends will reach.

We all want to assume we are going to have a beautiful sunny day in the canyons. Tweaking standard operating procedure will make the rare bad situation less likely to evolve into something for which there is no recovery. I think there also needs to be more team awareness regarding rope resources (i.e. is this the place for the lead to take the bulk of the rope in their pack on a particular rap).

In the spirit of simplification I'll simplify and rephrase my previous question:

An 80 kg human is ascending a static rope. This individual clips into a figure 8 on a bight on the same rope and ascends 15 feet above that knot. At that point all of the individual's ascending gear inexplicably pops off the rope and the individual falls the full 15 feet and is stopped by the backup knot. What kind of condition could we expect that person to be in after that fall?

How about only 5 feet above the knot? What about 2 feet?

----
Context:

This practice is often referred to as "clipping in short" or using a "catastrophe knot". It's a practice I've seen recommended in both climbing and canyoneering literature. When on a dynamic rope I think it might be able to prevent a catastrophe. When on a static rope I doubt it would prevent serious injuries if the knot is stopping a free fall. (It would probably help shorten a fall on a slipping friction hitch.)

I think this matters because I've seen people rely on that backup knot to justify incorrect changeover technique. For example, when transitioning from ascending to rappelling some people will remove one of the rope grabs before attaching the rappel device. This is often justified by the existence of the backup knot. My hypothesis is that these people are unaware of the dangers of actually falling onto that backup knot. They think they are on belay, but are they actually free soloing?

15 feet? I'm guessing under 8g's. Still pretty, uhhh, shocking. Wouldn't think it'd break your harness. Plus, knots would tighten, etc, to slow down peak loads.

Rumor has folks surviving 100+ foot falls onto static rope. Cavers?

If we're talking about "shock loads" which I think is more appropriately called dynamic load deflection; when an object falls unobstructed... Yeah, a 15 foot fall on static rope for a 180 lb person is 2700 ft-lb of energy to deflect. That's serious whip-lash. (Feel free to correct my math/physics, I'm out of my league here.)

I'm not aware of any such falls, either from my experience or from campfire lore. Even if they have occurred in caving, static falls would be rare, especially under the circumstances that are being described. Simply, because vertical cavers have substantial climbing systems on them as primary course of action, usually employing 3 points of contact, i.e. failure redundancy. If and when static falls did occur, it would most likely be the result of a rebelay or secondary anchor blowing out. Obviously, primary anchor failure being a deck scenario.

I did a quick scan of the ACA caving accidents for rope related falls over the past 15 years. Could have missed it, but I didn't find any related to static rope fall arrests. The ones I did find, I believe the victims would have been happy to take their chances on a static rope...just a guess.

Soooo, I'll take static fall for 2 feet, Alex.

wsbpress-
Ascending devices I have used have never 'inexplicably popped off the rope'.
Shoe-laces or some junk might.
Tethering yourself to two devices at all times is plenty of redundancy for me, but you could tie off to your rope (big wall style) every few feet, if it
makes you feel better.
For transitioning (needing to remove one device at a time) a back up knot IS a great idea but it needs to be tied CLOSE (within two feet). I consider two feet a 'top rope' fall- not much shock load.
The 2700 ft lbs Kuen is talking about could break your rope (remember loss of strength at the knot), or your anchor, and will definitely
break your back.

Rapterman-

Thanks for your response. I was actually trying to make some of those same points.

"Ascending devices I have used have never 'inexplicably popped off the rope'."​

Same here. When ascending devices pop off the rope it is usually explicable and user error. Anyway that statement was just to frame a hypothetical situation where the backup knot was stopping a free fall.

"Tethering yourself to two devices at all times is plenty of redundancy for me, but you could tie off to your rope (big wall style) every few feet, if it makes you feel better."​

It really doesn't make me feel better. Actually, I was trying to warn others who are using that practice as an excuse for not having two tethers at all times. I believe they may be somewhat unaware of the dangers of a static fall.

"For transitioning (needing to remove one device at a time) a back up knot IS a great idea but it needs to be tied CLOSE (within two feet)."​

Good advice.

"I consider two feet a 'top rope' fall- not much shock load."​

I think it depends on just how static the system really is. I was surprised to find that slings have been broken from sub-two-foot falls on drop towers. http://dmmclimbing.com/knowledge/how-to-break-nylon-dyneema-slings/ Certainly these conditions are more static than the situation we are talking about though.

"The 2700 ft lbs Kuen is talking about could break your rope (remember loss of strength at the knot), or your anchor, and will definitely break your back."​

Ouch.

Falling from 15 feet above a catastrophe knot is a 30 foot factor 2 fall. That is a heck of a lot of force with static rope. I am going to say that there would be a good chance of serious injury and possibly gear failure. I would like to know what the mechanical engineers out there have to say about this. Ascending gear blowing off your rope-bad day.

No. Falling from the anchor 15 feet onto the knot would be a fall factor of one. If you're 85 feet down and make the same fall, the factor is 0.15. The fall factor is the distance of the fall divided by the length of rope that stops the fall.

Gordon

Here are the equations I'm planning on using to satisfy my curiosity whenever I get around to it. https://en.wikipedia.org/wiki/Fall_factor#Impact_force

What would be really great though is if someone with a load cell and a drop tower ran some tests and reported. Or perhaps better yet someone finds such a report on the interweb and shares the link .

Gordon,
the Fall factor equations are for dynamic climbing rope and assume a range of impact force and dynamic elongation specified by UIAA.
Fall factors for static ropes are WAY different.
I know of two instances in the rigging world where static rope (Tech 12 and Amsteel gray) were being used to fly stunt people and the
fly system 'locked up' while the performer was in near free fall.
The flying systems were supposed to slowly decelerate the performers but had brakes activate instead.
In the first situation the performer had fallen about 30 feet when the system seized and they broke their back (crushed three vertebrae) inside their harness.
In the other (the harness was designed to absorb a shock overload and) the performer was unhurt, but a 12 foot fall with a 300 lb performer
(200lb guy wearing a 100lb monster suit) on static rope generated a force of around 3,000 lbs. bursting a series of spectra bar-tacks in the harness.
It has taken me a while to get my head around shockload as it applies to static rope because many of us live in the dynamic rope world.

Yes, for rope ascension, you are right on. I was thinking of the typical climbing situation. Still a 15 foot fall on static rope is a lot of force. Of course the answer is not a Yates screamer but rather not taking your ascending devices off the rope at the same time. I'd rather carry better ascending devices than waste grams on a Yates device.

Ken

is it just me... but what is the "extreme duress"? If rappelling causes extreme duress, then perhaps you should find another sport (Ram excluded).

You rappel down, the rope doesn't reach, you need to go back up. Where is the extreme duress? This is part of rappelling - sometimes things don't work out as planned. That's why we have skills, and training, and practice.

You do have skills, training and practice, right?

Tom

Extreme duress was brought up in the thread and I tried to think of an example for me. It would be rappelling down something like the situation described in the Not Imlay accident when, for whatever reason, the rope is way too short. There is just something about the psychology of it. Being way off the ground free hanging near the end of the rope.. even if you know what to do. There would still be an "oh shit!!" factor. It's mental.

Responding to the theoretical. The closest I ever came was finishing a canyon late when the sun was going down, rapping in an increasingly dark evening. Having to re-thread and re-tie the anchor by feel, when sitting near the edge of a 200' drop. Others depending on me, it was a bit stressful, but I did everything right and we all made it down safely. But, I can imagine being in a really bad rappelling situation as a mental exercise..

Even doing Egypt II rap when everything went as it should was stressful.. YMMV. To answer your last question: yes, but certainly not more than many here.. but enough to be safe on what I chose to do.

As a old wall climber (kinda retired?), ascending fixed rope, on an overhang, way off the deck, is the freakiest stuff I have ever done.
Sort of a grit your teeth, hang on to your lunch, and pray sort of activity.
For many of us recent events have under-scored the importance of training and practice
and we are glad to report that many canyoneering teams in Las Vegas have been hitting the 'Training Crag' at Red Rock a LOT lately (we can see those brightly colored rope bags from our house!)
Congratulations everyone for getting out there, on the ropes, and building your 'skill set'.

Is the fall factor different, or is the force generated different because of the different stretch?

Gordon