Janus Anchor

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Ugly rope marks.

1 Janus anchor

[edit] Janus anchor

Using upstream anchors

Figure 1

Figure 2

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Figure 4

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Figure 7

Figure 8

Figure 9

Using Janus anchor as sling on short rap

[edit] Purpose

Since my first technical canyon trip I've been working on the problem of releasable anchor systems. I'm hoping to solve two problems. First, I'd like to be able to use upstream anchors, say a tree or arch, extend the anchor to the lip of the canyon and still retrieve that extension. Second, when an anchor is positioned above a significant lip the rope-pull cuts ugly grooves in the rock. I'd like to quickly and safely extend the anchor beyond such a lip for aesthetic and ethical reasons.

So far, the systems I know of are described on the Advanced Canyoneering Anchors page and include the Omni-sling, the Macramé knot, and the very interesting Slick. I also developed a system called the Greasy Girth. Unlike the other systems, the Greasy Girth's release mechanism is blocked until the rope is pulled out. Like the Omni-sling and the Macramé knots, the Greasy Girth runs the risk of biting and becoming difficult to release. Matt Moore's version of the Slick appears to be a very reliable system that is safe and releasable. However, it is not available.

Out of a desire for access to a similar system, I've developed what I'm calling the Janus anchor. Named after the Roman god of doorways, it, like the Slick, can either be open or closed. Like the Slick, it can be released from below and one must be careful not to pull on the release strand while on rappel. Unlike the Omni-sling, Macramé knot and Greasy Girth, the risk of biting is nearly non-existent. Matt Moore's web site describes many unique situations where the Slick can be used to extend an anchor from an upstream element to the lip of a drop and still retrieve the lengthy extension. The Janus anchor should function in a similar manner.

[edit] Risk

Risks of using any releasable system are two fold: if it releases mid-rappel you will fall and possibly injure yourself; if it does not release you will lose whatever is attached (the extender, the pull line, the rope, etc, etc). Like all other releasable systems, the Janus anchor is a little tricky to set up and mistakes can be made. Care should be taken to learn the system until you feel comfortable tying it.

There is additional risk in that this system reduces redundancy in the anchor by focusing all the weight of the rappel onto single points. This risk must be assessed when establishing an anchor with the Janus anchor.

The Janus anchor attempts to limit risk of premature release by transferring rappel force onto the interlocking loops and release loop. Thus, increased rappel force requires increased force to release the anchor. This limits the risk of premature release. It will not prevent release if you get tangled in the release line and continue the rappel.

[edit] Instructions

To tie the Janus anchor as an integrated webbing loop you will need 6+ feet of 7mm cord and 9 feet of 1 inch tubular webbing. Alternatively you can tie it as an autonomous device using 6½ feet of 1" webbing. Always leave a reasonable tail when tying overhand and waterknots with webbing.

Integrated webbing loop:

Tie off two loops of webbing, one longer than the other, with overhand knots on each end of webbing. (Figure 1)
Tie a short loop of cord with a double-fisherman about 18". Leave about 12" of tail. (Figure 1)
Feed the cord through the water knot on the longer loop. (Figure 1)
Lock off the cord tail and the overhand tail with a second overhand knot. (Figure 1)
Feed the long loop of webbing through the short loop. (Figure 2)
Lock off the webbing loop by feeding the upper cord loop through it and then feed the lower loop through the upper loop. It is important that the lower loop feeds through the upper loop. The force on the webbing loop is transmitted to the cord's upper loop and draws the two sides of the upper loop together. This narrows the loop and makes it difficult for the loop to widen enough to flip over the locked off lower loop. (Figure 2 and 3)
Lock off the upper and lower cord loops by feeding a loop of the cord tail through it. Tighten the cord loops against the webbing loop. (Figure 4)
Tuck a second loop of cord between the two overhand knots. This acts as a safety release. When the rig is weighted, it sinches against this loop, decreasing the risk of premature release. (Figure 5)
Tie pull line into cord and carefully throw so as not to prematurely release rig. You could clip a carabineer to either or both the safety loop and the locking loop to prevent premature release. Release the carabineer before the last rappeller rappels. (Figure 6)
Carefully rappel so as not to put force on the pull line.
To release, pull the safety loop and then the locking loop out of the lower cord loop. The cord loops and webbing loop should then fall apart. Once apart, continue pulling to bring down the rig. Depending on conditions, it may be best to add a rapide somewhere on the system and rappel off double-stranded or with a 'biner block, pull the rope first and then retrieve the rig. Alternatively, one could release the rig and pull it down via the rope and pull line together. I'm not sure which will be more prone to snags on the way down. Perhaps pulling the pull line and the rope simultaneously so the two come down as a package. If snagged, pull the rope out of the mess and then jimmy with the rig.

Autonomous device:

Follow the same instructions as above, but don't tie the short loop on the end of the webbing. Instead, double back the lower webbing into the second overhand knot as a large waterknot. This makes a small autonomous device that can be attached to any length of webbing loop. (Figure 7 and 8). If you plan to Girth Hitch this lower loop into something, consider adding a half-twist in the lower loop so the hitch lays flat.

The autonomous device can be tied at home and carried into the field. It may be best integrated with a piece of old rope or spectra cordelette using a figure 8 on top and a butterfly knot below. The cordelette will wear better than webbing and the butterfly knot holds tangential forces better than an overhand knot or a figure 8. Additionally, butterfly knots in cordelette are much easier to untie and reposition than overhand knots or figure 8's in webbing once they have been weighted. Alternatively, you could use in-line-figure-8's in place of the butterfly knots. This may direct the force more appropriately than the butterfly knots, but I think the butterfly knot tends to be easier to untie.

Should the distance to the canyon lip be much longer than the cordelette, one could extend this from the second butterfly knot to the rapide using a long length of webbing.

Approximate Dimensions:

Cord loop 18"
Cord tail 12" - long enough to tie off in the second water knot.
Cord pull tail 50" could be longer or integrated into the pull line.
Webbing long loop: 9"
Webbing short loop: 7"
Between water knots: 2"

[edit] Discussion and Experience

In my current pictures I'm using 7mm PMI accessory cord and not spectra as I initially planned. I started with 5mm cord, which is probably ok, but recently switched to 7mm for safety reasons. The 5mm cord is rated at 5.5 kN = 1200 lbs. As no more than ¼ of all the force on the rig can be on the cord, and the cord is doubled over twice, I estimate that each cord strand only holds 1/16th of the total rig force. 1 inch webbing is rated at 18 kN = 4000 lbs. ¼ of that is 1000 lbs and 1/16th of that is only 250 lbs. Both are below the 1200 lbs limit. So, while it may be better to use something stronger, a bit of good cord should do fine. I think 5mm would suffice, but then again, maybe one should use 6mm (6.8 kN = 1500 lbs) or 7mm cord (9.3 kN = 2000 lbs).

Testing using 5mm cord resulted in the upper loop flipping over the loop tail at 800 lbs when the upper loop was large and 2400 lbs when the upper loop was small. However, on both tests, the anchor didn't fail, as this requires pulling the entire tail loop through the upper loop (Figure 9). These tests also showed that the autonomous system had at least 2 inches of extension when weighted, suggesting that reasonable tails should be left on all the knots. Because of these tests I've used a small upper loop to prevent the loop tail from getting flipped and a longer tail loop for safety.

Sonny Lawrence was considerate enough to do pulls to failure of two Janus anchors. The first used Blue Water 1 inch tubular webbing tied with 5mm PMI cord and the second used military spec webbing and 6mm PMI cord. The first rig stretched 138 mm and broke at 22.3 kN. The second rig stretched 183 mm and broke at 15.9 kN. Both failed at the water knot. Both released when the pull cord was pulled, despite the heavy loading. Both were tied to minimize the upper cord loop and neither experienced the upper loop flip noted previously. This would suggest that minimizing the size of the cord loops prevents the loop flip and that even the thinner 5mm cord is sufficient for strength, although I think the 6mm feels a little nicer.

As rappel force is applied to the Janus system, that force is transfered to the interlocking loops. Increased rappel makes release increasingly difficult. In a simple slow pull test, with the system weighted by 80 lbs, it consistently required 40 lbs of force on the pull line to release the system. This provides some margin of safety against inadvertant release.

I've rappelled off the integrated webbing loop and the autonomous device systems about 35 times in the field. I've used it to ghost almost all the drops in Imlay, Pine Creek, Neon, Medieval Chamber and das Boot. I've used it to rappel from natural chocks, trees, wedged logs and as a Simul-rap from Morning Glory Arch and the Imlay arch. The system has always held and always released. So far I've been very happy with this anchor and think it will fill both of my inital goals.