Gri-gri rappel backup?

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7 years 7 months ago #136542 by Bushwhacker
Gri-gri rappel backup? was created by Bushwhacker
So this might be a really stupid question, but is it safe to rappel down a tree using a Petzl Gri-gri? Or would you need some sort of backup, like a friction knot?

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7 years 7 months ago #136543 by dogwood
Replied by dogwood on topic Gri-gri rappel backup?


You might want to have a look at this system!
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7 years 7 months ago #136544 by dogwood
Replied by dogwood on topic Gri-gri rappel backup?
By the way, that is certainly not a stupid question!
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7 years 7 months ago #136545 by Bushwhacker
Replied by Bushwhacker on topic Gri-gri rappel backup?

dogwood wrote:



You might want to have a look at this system!


Using a whoppie sling for the foothold is quite ingenious! Thanks for showing me that!

So does he only have two tie in points? The gri-gri, and the rope that's connected to the ascender? I've been doing that, but when I descend, I often just disconnect my ascender (I don't know how else I'd get down). Is this really safe?

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7 years 7 months ago #136546 by dogwood
Replied by dogwood on topic Gri-gri rappel backup?
Yes, he's tied in to his Grigri and the Microscender. It sounds to me like you're familiar with the Grigri, right? There are several climbing systems, and they're adapted to an individual climber's needs and climbing style. I believe it's always useful to think in terms of a complete system, including all of its parts and pieces, and what you want to accomplish with it. Could you post some pictures of your climbing system?

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7 years 7 months ago #136547 by dogwood
Replied by dogwood on topic Gri-gri rappel backup?
If you're using a tooth cammed ascender in your system, you need to remove that from the line before you descend. The rule for ascending on tooth cammed ascenders is that two points of attachment are needed. For belay devices, you need to keep one hand on the brake strand of the rope, usually down at your side and away from the belay device. You don't want to get your fingers tangled up in that thing!

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7 years 7 months ago #136549 by dogwood
Replied by dogwood on topic Gri-gri rappel backup?
The Grigri is not an autolocking hands free device, so you need to keep your hand on the brakeline when descending. The real beauty of a work positioning system, and there are many, is that you can ascend, descend, stop anywhere in between, and take your hands off the line to do other stuff.

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7 years 7 months ago #136550 by Bushwhacker
Replied by Bushwhacker on topic Gri-gri rappel backup?

dogwood wrote: Yes, he's tied in to his Grigri and the Microscender. It sounds to me like you're familiar with the Grigri, right? There are several climbing systems, and they're adapted to an individual climber's needs and climbing style. I believe it's always useful to think in terms of a complete system, including all of its parts and pieces, and what you want to accomplish with it. Could you post some pictures of your climbing system?


I run the rope through the ascender, around the gri-gri, and back up through the carabiner that's attached to the ascender.
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7 years 7 months ago - 7 years 7 months ago #136551 by dogwood
Replied by dogwood on topic Gri-gri rappel backup?
http://www.rescuedirect.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=SM220500N&Store_Code=RD

Here's another piece of gear, similar to the Microscender. Perhaps you could use a rope grab in your system for progress capture, as in the video. On descending, just hold the cam open, and if you want to come to a stop on the way down, you can allow it to hold your position. If you put a Revolver carabiner on it, you'd be able to do advances with a 3:1 mechanical advantage. Pretty handy!
Last edit: 7 years 7 months ago by dogwood.

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7 years 7 months ago - 7 years 7 months ago #136554 by moss
Replied by moss on topic Gri-gri rappel backup?

Bushwhacker wrote: So this might be a really stupid question, but is it safe to rappel down a tree using a Petzl Gri-gri? Or would you need some sort of backup, like a friction knot?


Good info provided by Dogwood!

The short answer is yes it is provided you know how to operate the Grigri safely. Whenever you pull the release lever your right hand must be gripping the rope below the device. If you let go of the rope with your right hand while pulling the release lever you will meet the ground very quickly. Be sure that the rope exiting the Grigri is directed over the smooth folded area of the Grigri facing you (assuming the release lever is in the correct left side position). This rope position gives you smoother control during ascent. To get an ideal smooth descent you balance pressure between the release lever and your right hand on the rope. On a long fast rappel a Grigri will heat up a rope enough to melt it. Moderate descent speed is recommended.

I've never used a backup with a Grigri on descent. It can be done theoretically, classic autoblock technique as you would with an F8. Overall I'm not thrilled with the Grigri II, it's great for a lightweight belay device but it's a step backwards from the original Grigri as a tree climbing tool. The Petzl Rig is a better choice IMHO for tree climbing over the Grigri II.

As with all new tree climbing gear and technique, practice low and slow before using at height.
-AJ
Last edit: 7 years 7 months ago by moss.

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7 years 7 months ago #136555 by moss
Replied by moss on topic Gri-gri rappel backup?
To elaborate further on why I don't like the Grigri II for tree climbing...

When I'm rappelling single rope I like to position my right hand on the rope approximately at my hip. With my rope hand in that position the rope exiting the Grigri II will not stay on the curled over metal area and it's difficult to get a smooth ride. To keep the rope on that sweet spot you need to hold the tail of the rope very close to the device. I feel that is not a strong control position. I modified my Grigri II to compensate for that problem. Works well but the other issue is that the Grigri II is optimized for 9.4 mm to 10.3 mm rope diameters. 11mm or greater arborist ropes get squeezed pretty hard going through the device, not at all optimal.
-AJ

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7 years 6 months ago #136739 by Nimbadon
Replied by Nimbadon on topic Gri-gri rappel backup?
Hey Moss, did the mods to your grigri 2 help?

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7 years 6 months ago #136741 by moss
Replied by moss on topic Gri-gri rappel backup?

Nimbadon wrote: Hey Moss, did the mods to your grigri 2 help?


It made it usable for me. I still don't like it much though for 11mm ropes, it's tight in the GG 2. Works fine for 10mm. I'm rarely using a descender these days, Rope Wrench and hitch are the way I climb SRT 90% of the time.
-AJ

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7 years 6 months ago #136743 by Nimbadon
Replied by Nimbadon on topic Gri-gri rappel backup?
Yep, I only really use mine when we have multiple climbers using the same access line, mine works on some ropes better then others ( same size different manufacturer ), the sweet spot is hard to find and maintain,
maybe it just needs some breaking in.
Would you be willing to share your mods?

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7 years 6 months ago #136744 by Tree-D
Replied by Tree-D on topic Gri-gri rappel backup?

moss wrote: The Petzl Rig is a better choice IMHO for tree climbing over the Grigri II.


Agreed.

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