Every one has their preferences, and the debate over descending devices will go on unending.

My $.02...

I was a volunteer on the rope team at a very famous adventure race in Utah in 06. www.ecopromalquest.com The canyon ascents and rappels at that race were not 60 feet or 160 feet, but rather 600-800 feet, some higher including a zip line almost 1600 feet off the desert floor. The ONLY rappel device the racers (all 360+ of them) were allowed to use was an 8, sometimes reversed. That is, clipped into the harness at the large end and rope running through the smaller hole. As I remember, there wasn't all that much rope twisting. Some, but not THAT much.

There were some sections on that course where I would have given almost anything I had for just one branch to hold on to!

cambium wrote:
The set up and use of the gri-gri, the I'D, and the Petzl stop are relatively easy to understand. Unless I'm mistaken, they can all be installed on a rope without much fuss. Is the same true for the ATC? It looks like a solid block with holes in it. Does it come apart to allow easy application to the rope mid-line? Or, is it a device that one puts on while on the ground and employs when needed? In any case, it is certainly affordable and light weight, but I have also been looking at the Simple Petzl Stop (as opposed to the automatic version). I wonder if anyone has had experience with that product.

cambium

I've used an ATC for SRT descent. The way they work is feed a loop of rope down through the opening and put a locking carabiner through the loop. Attach the carabiner to your harness anchor (Google ATC rappel and you'll find complete instructions). ATC's are jerky for a single rope descent. They're optimal for a doubled rope descent. I like a hands off stop, ATC doesn't provide that. For tree climbing it's a good idea to extend your ATC/carabiner out on a short sling and attach the sling to your harness. This will give you enough room to install a prusik/autoblock below the device so you can have a safer ride down. It's more convenient too because you can stop during decent and free up both hands without having to lanyard in.

For tree climbing the Grigri is my favorite SRT descent, it's compact and does the job, no nonsense. The I'D is bulky and overkill for me. Grigri, I'D or Eddy are great tools to have because they are multi-purpose, specifically they are perfect for setting up an SRT RADS or Yo-Yo system. They are well worth the investment.

Here's a climber about to rappel out of a tree on a doubled rope using a tethered ATC with prusik back-up. This is a safer way to utilize an ATC in tree climbing, as mentioned earlier I'm uncomfortable with the idea of descending out of a tree on a system that doesn't have hands off stop. For instance if you collided with a limb during descent you could become disabled enough that you might end up with uncontrolled drop to the ground.

Test and learn all static or SRT descending techniques and gear close to the ground, don't test when you're up high! (mandatory disclaimer)

ATC rappel (view the large size for detail)

-moss

The same setup can be employed with an 8 on a single rope. Attach the 8 with a daisy chain or cord, and attach a prusik to the main D between you and the 8. This is a much better way than attaching the 8 directly to the main D and putting the prusik above it. The prusik can really jam tight like that, and it's a real bear to get loose if your not versed in self rescue.


Regular 8


Rescue 8


Not wrong, but this can sometimes get you into trouble.


Double rope w/ belay device

Looking good there Baker. My only comment for tree climbing is to cinch the tether on the anchor biner so the gate doesn't get loaded if you stop on the way down on a limb and unload and reload the system. Agreed that it's a bad idea to put the prusik above the descender since the descender takes some load off and makes a hitch below much more usable.

There's a way to tie a sling/tether using a double fisherman's that cinches a noose on one end to solve the gate loading problem, it's in the Tree Climber's Companion (which I lent out). Can't find an example of this knot online. I think the way it works is just capture the other side of the sling with one of the double overhand knots.
-moss

Wow, that's a blast from the past! I forgot all about that knot.





Some good information can be found in the following safety report presented by our arboriculture friends over the pond. There are some photos of the captive loop or sliding prusik as well.

http://www.hse.gov.uk/research/hsl_pdf/2003/hsl03-18.pdf

Forgot too that you can girth the open loop end on the biner if the cord has a high enough rating to make up for the percentage (whatever it is) strength loss of the girth hitch. You might need to invert an HMS biner to get enough room for the girthed cord and the anchor for the descender on the same biner. I've seen some eyebrows raised at two rope anchor/ends attached to one biner. Seems ok as long as they're not wandering around on the biner.

But you can see why an all-in-one hands off descent device is popular, less parts to the system, quick on and off.
-moss