Too often people think that a rap backup will work all of the time. It really isn't a 100% redundant system. Cloee though, it its designed properly. The most critical issue is making sure that neither part interferes with each other. In that case, the whole works collapses.

I think that adding a tool to take some of the load on a long rap is a good idea. When I climb with a hitch and I want to do a fast, long rap, I use an HMS biner attached to my hip d-ring below my hitch. The Munter is my primary and the cllimbing hitch is the backup. Me left hand is above the hitch and the right hand controls the MUnter. Since the left has to grab and the right has to slip, if my brain ever got inot overload one or the other will work since they are opposing. The normal response to panic is to grab tighter. I hope that this setup would work until my brain gets control of the situation.

In a rescue situation I don't think that your setup is the best. It takes too many hands to operate. Another issue is the lack of testing with two person loads. When I teach AR I prefer to not see the rescue load come onto one system. My preference is to have two parallel systems with a connection between the two.

Good discussion!

Tom

The purpose of this entry is to summarize the discussion at this point. The operative word throughout our exchange has been controlled descent. The underlying question is what method of descent and what application of technique establishes the greatest margin of safety? In relation to the DRT set with a Blake’s Hitch, the experienced climbers are using a descending device beneath this friction knot for the purpose of reducing friction. A consequence is a smoother descent. The worse thing that can happen to the Blake’s Hitch is over-heating of the knot due to the friction build-up during a fast descent. The result is rope damage. Though there are documented reports of Prusiks disintegrating on uncontrolled rappels, this is less likely to happen with the Blake’s Hitch for three reasons: 1) the resistance of the rope passing through the tree crotch diminishes speed. 2) these are polyester ropes with a higher melting point. 3) The Blake’s Hitch uses a larger diameter rope. The documented Prusik failures were on static rope systems where speed builds more quickly, and the failed ropes were made of nylon with a smaller diameter.

In “The Tree Climber’s Companion” beginning with page 64, Jepson is very disciplined to never mention the word rappel when describing the process of descending from a tree. Every de_script_ion emphasizes controlled descent. Even the figure-8 is described as a descending device, not a rappel device. This wise choice of wording creates distance from the use of a tree descent as an adventure sport.

Thus, the concern of the tree climber continues to be how to make a descent absolutely safe. Though the Blake’s Hitch has a proven reliability for descent, climbers are working to reduce friction on the knot by establishing a back-up to it. The benefit is ease of control and reduced rope damage. Finally, personal judgment in a descent has the ultimate control on the outcome of events.

The purpose of this entry is to highlight the discussions on the development of a “spider” configuration for descent in a DRT system using a Blake’s Hitch. Because the “spider” configuration places the descending device above the back-up knot, these are the aspects to consider: 1) it’s not a standardized practice 2) most descending devices require slack for installation 3) a descending device can be drawn into the lower knot if not protected 4) the descending device is placed higher from the harness.

The experienced climbers are achieving the benefits of reduced knot friction by attaching a descending device beneath the Blake’s Hitch. They’re using the traditional descent configuration: the back-up knot is above the descending device. The traditional configuration uses two hands to control the descent. One hand is working to release the upper knot. The other hand is controlling rope into the descending device (see Jepson page 65 for a diagram). When control of this traditional descending device is released, all the weight of the climber is transferred solely to the Blake’s Hitch –as designed.

In the “spider” configuration, only one hand is needed to control the descent. That control hand is on the Blake’s Hitch underneath the descending device, and it requires very little effort to slide the knot down. When hands are off the “spider” descent system, the climber’s weight remains largely on the descending device with only a small fraction of the weight returning to the Blake’s Hitch. Hence, less force on moving the knot down is needed. Otherwise, the mechanics of descending on the Blake’s Hitch are the same.

How is the descending device controlled in the “spider” configuration? The “spider” configuration operates on the same principle as the Fireman’s Belay or ground belay. In “The Tree Climber’s Companion” on page 64, Jepson describes a ground belay as a ground person pulling down on the rope. The tension in the rope stops the climber’s descending device. In the “spider” configuration, the Blake’s Knot is literally a hand pulling down on the rope. Like the ground belay, the Blake’s Knot creates enough tension to arrest the descent.

Much thanks to the feedback generated thus far on this topic. It brought forth discussions on techniques and preferences. Especially thanks to sawmill1 for being so thorough with his evaluation and establishing adaptations. As a reminder, a diagram of the “spider” configuration was posted a few entries ago. Remember to go “slow and low” until this is recognized as a standard practice.

Regards,
JimK

The purpose of this entry is to provide the passage from Jepson 2nd Edition "Tree Climber's Companion" that echoes the voice of the experienced climbers on this topic of reducing hitch friction damage on a descent in a DRT.

p. 82

"Helpful Hint: Heat damage to the cord used to tie the friction hitch can be prevented during a descent on a dynamic climbing line system by first releasing and slightly loosening the hitch and using one of the following methods: 1) descend on a loosely formed foot lock on the climbing line: 2) descend on a Munter hitch tied to a pear-shaped locking carabiner attached to the saddle at a point below the friction hitch (a leg strap works well). Both methods are effective with any of the friction hitches used as a self belay."

Thanks for the sharing and productive input. The voice of the experienced climbers rang out clear on this topic.

Regards,
JimK