Would girth hitching a longer prussic into the guide loop of a tube style belay device be an acceptable backup for a rappel?

Pat Light wrote:

I'll also point out that while the average climber would do well to put her third hand below the rappel device, a lot of old-school rescue folks will put a VT prusik above the rappel device, totally bomber. That was another theme of this thread that I found puzzling (not from Helen, but in general): "Prusik above the rappel device" isn't the reason this idea is dangerous, and isn't even necessarily a problem. "Prusik fixed to the rappel device" is the issue.

In summary: A lot of y'all should be spending more time two feet off the ground in the Backyard Technical Institute.

Well, my noob head also thinks "backup" is something that makes something else redundant, right? So, if the ATC is the thing you're attached to, via that bight of rope, and that only works with your hand on the rope, otherwise that connection is pointless (okay, barring a leg wrap, stuff like that)? Then, a "third hand" controlling the rope should be attached to you also? It's a backup for the combined system of your ATC plus hand on the rope. So it has to do both parts. Hold you, move on the rope. Right?

And what's VT?

Rescue rigging is interesting! Quite a rabbit hole, even just looking at gear on Petzl's site! Carabiners for triaxial loads! Who knew?!

Ages ago, googling prussik hitches netted a bunch of stuff where loads (litters) are "belayed" with a prussik on the lowering line to backup the lower.

Best, Helen

Edit to add, thanks again! I don't even hafta leave the house to mess around with rigging.

VT is a valdotain truss. I was waiting for someone to bring that up. Here is a picture of the setup I have been using. I am really happy with it. It’s also very versatile for instance when riding a pig I use the locking draw to connect myself to the ATC and use my Bluewater VT Prusik to tie a three wrap prusik that goes on a locker directly to my belay loop on the brake strand. Can anyone see a problem with this setup? 

I think this thread brings up a really important point (other than that no one should sell life insurance to Greg). When you're at the Backyard Technical Institute, the goal IS NOT to see if a thing works. The goal is to see HOW IT CAN FAIL.

We got a perfectly good video showing a keeper loop holding body weight. Sometimes. Without bouncing. That's great and all, but hasn't addressed the "is this safe" question. Just the "will you die the first time you try this" question. 

Equally, when my 100lb wife tries without the keeper loop attached, Greg's scheme holds! The first time, with the thick fuzzy rope. But not always, not 200lb me, not on the alpine ropes, etc... If the goal in the Backyard Institute were to show Greg's scheme working, one test and it works! But the goal is to show that it can fail, so multiple tests (with even one failure) are needed. 

Joseph W. Dutton wrote:

VT is a valdotain truss. I was waiting for someone to bring that up. Here is a picture of the setup I have been using. I am really happy with it. It’s also very versatile for instance when riding a pig I use the locking draw to connect myself to the ATC and use my Bluewater VT Prusik to tie a three wrap prusik that goes on a locker directly to my belay loop on the brake strand. Can anyone see a problem with this setup? 

Great setup, I use it when canyoneering with a non-atc type device. If you need to do a knot pass, this system will make your life easier if you have a little more extension than is pictured.
fwiw, I use the VT cord to hold my chalk bag—just have to experiment with the right size of biner to match your waste size 

Pat Light wrote:

I'll also point out that while the average climber would do well to put her third hand below the rappel device, a lot of old-school rescue folks will put a VT prusik above the rappel device, totally bomber. That was another theme of this thread that I found puzzling (not from Helen, but in general): "Prusik above the rappel device" isn't the reason this idea is dangerous, and isn't even necessarily a problem. "Prusik fixed to the rappel device" is the issue.

In summary: A lot of y'all should be spending more time two feet off the ground in the Backyard Technical Institute.

That's mostly true. But the point does remain that above the rappel, you're having a prussic cord talking in all your weight, whereas below, it shares tension with the rap device. That does imo make in an inherently better setup - old-school folks may have kept other habits, but regarldess.

The VT is fine if you wish and resolves the locking issue with a classic Prusik when placed above a device. Also easier ascending and can be used for some sexy rescue tricks (descending a taut rope). 

In terms of KISS it's more complicated to tie (IMO). And while you save yourself extending the belay device most people extend the backup so in terms of clutter It's a wash. It's also pretty burly and I prefer to carry my little 5mm/35cm/20g Beal Jammy that works just fine below the device. Does anyone make a lighter/skinnier sewn VT? I imagine limitations because it's meant to hold one's entire body weight. I also personally prefer to have both hands on the brake strand instead of one above. Less likely to need my backup in the first place if I get knocked around. But a VT is a functional rig for sure. 

I think bringing the VT up is slightly pedantic :-) but a cool thread drift! Yes I could have clarified that a classic Prusik (the one 99% of climbers use) above the rappel device is inadvisable, not any/every backup. It seems like bringing up novel knots in a thread where some people don't understand basic rope systems is not necessarily productive. Probably best for OP to stick to the standard textbook for a bit. 

Old lady H wrote:

Wait...trying to understand....

How are you guys getting that he is not connected to the rope, or the ATC, if/when the keeper loop breaks from the ATC? This looks like the ATC is rigged with the rope, through a locker on a belay loop. Maybe facing an awkward direction, but minus the additional prussic, what's any different than just a rappel with no backup?

I was a bit confused at first too. I was assuming that the prussik would catch and pull the atc up into guide mode. That may not be the case. What can happen is the atc will stay where it is on the rope, then all the free rope hanging below will just zip up through the atc since there's no angle/friction to pull the biner into the atc. Think about when you make a bight initially to put through the atc but instead of clipping, just keep pulling the bight through.

Joseph W. Dutton wrote:

VT is a valdotain truss. I was waiting for someone to bring that up. Here is a picture of the setup I have been using. I am really happy with it. It’s also very versatile for instance when riding a pig I use the locking draw to connect myself to the ATC and use my Bluewater VT Prusik to tie a three wrap prusik that goes on a locker directly to my belay loop on the brake strand. Can anyone see a problem with this setup? 

How do you slide a hitch above the ATC down, if there's a bulge or something to pin your hand?

H.

jdejace wrote: I think bringing the VT up is slightly pedantic :-) but a cool thread drift! Yes I could have clarified that a classic Prusik (the one 99% of climbers use) above the rappel device is inadvisable, not any/every backup. It seems like bringing up novel knots in a thread where some people don't understand basic rope systems is not necessarily productive. Probably best for OP to stick to the standard textbook for a bit. 

Yeah, the VT is kind of specialized (and hard to pronounce).  In the interest of exploring esoteric use cases, if you have to pass a knot on rappel, it’s better to have the backup above the rap device, and the best knot to use is a VT hitch, because you can slide it under load.  Something else to practice in the backyard. 

Old lady H wrote:

How do you slide a hitch above the ATC down, if there's a bulge or something to pin your hand?

H.

I’m having a hard time imagining a situation where I would be pinned against the rock in a way that would mess with my ATC or VT. Possibly I’m misunderstanding the situation you’re trying to describe. Anyway I’ve never had a problem with this system. 

I saw the words girth and longer and was intrigued. 

Joseph W. Dutton wrote:

I’m having a hard time imagining a situation where I would be pinned against the rock in a way that would mess with my ATC or VT. Possibly I’m misunderstanding the situation you’re trying to describe. Anyway I’ve never had a problem with this system. 

I believe the issue Helen is thinking of occurs when someone extends their device too far (I've seen an ATC 4 ft above the harness) and then you need to hop over the edge of an abrupt large roof. Of course a device that far away would effectively preclude an autoblock or other safety above it.

This is why you get 50 pages of safety instructions when you buy a carabiner.

https://youtu.be/Ens4VYu3eNo

Here's a vid of just the things discussed here.

First, as far up as this dude is reaching, to have his hand on top of the tress? I might not reach, 100% of the time.

But my objection is if you are getting started over a big, bulgy, ledge, say, so you need to sort of slither off the thing, can't just lean or walk back, you'll not clear the bulge before feet are in the air. At some point, I could see hanging free, mostly, but with that top bit held down tight to the rock. No way to get fingers under it (or maybe even hand pinned to rock). Picture a curved rope path, not vertical.

With the backup below, it's on the nonweighted end, and entirely in reach.

That help?

I have to say, the arborist vids, just this and a pulley, are slick! It looks great in that application.

Thanks! Helen

Redyns wrote:

I saw the words girth and longer and was intrigued. 

Makes sense. After all, the title is just an anagram for:

"Would a longer tube be an acceptable girth? Guide back up into the loop for a device style of h****ing. 

Belay rappel prussic."

Old lady H wrote:

But my objection is if you are getting started over a big, bulgy, ledge, say, so you need to sort of slither off the thing, can't just lean or walk back, you'll not clear the bulge before feet are in the air. At some point, I could see hanging free, mostly, but with that top bit held down tight to the rock. No way to get fingers under it (or maybe even hand pinned to rock). Picture a curved rope path, not vertical

I’ve never had a problem like this. Probably because my entire system is pretty close in. It may be hard to see in the picture but the VT lands a very comfortable distance above the ATC. One of the reasons I primarily use this setup is because I don’t really like extending my ATC. The way the guy in the video extends his ATC and puts a VT above does seem like it could be a problem. I also like this setup because it’s versatile I’m not married to one way of doing it. Although I use a VT above 90% of the time I can easily extend my ATC and use a three wrap prusik below if the situation dictates. 

Not Hobo Greg wrote:

Yes it is: backup is attached to ATC, ATC is still attached to rope via the locker. They would only plummet if the friction hitch slips. You won’t find me using this method but we should at least be able to agree about the facts.

Dude... aren't you a guide?

You are correct all the way up to the bullet point. Try it in your backyard, for real.

Alexander Blum wrote:

I gotta admit, over here at my own Backyard Technical Institute, I was never able to produce quite the satisfying YEET you manage to get from yours