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david.yount
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Oct 22, 2004, 4:41 PM
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Sometimes when you need two ropes to rappel, there is an edge near the top of the rappel. This edge may create difficulties after the last climber has descended when you try to pull the ropes. The joining knot may hang up on the edge.
The Overhand knot with both tails on the same side has shown in several lab tests to be far superior in strength (stability) to any other zero profile knot. The other common zero profile knot is the Figure-8 with both tails on the same side, but this knot easily inverts repeatedly until the tails pull thru.
All other knots used to join two ropes together have a profile. This profile gets hung up on edges fairly easily. The Overhand, when weighted, presents no profile to the edge, it almost glides over, in ideal situations.
The Overhand with tails on the same side is very commonly called by the misnomer "Euro Death Knot" or "EDK." There is story telling history with this misnomer but I'll defer at this point.
A common technique is for the last person down to deal with it, everybody else leaves the joining knot near the anchor, rigs their rap device and backup friction if used, and raps down to the ege, over the edge, and down to the next belay.
The last climber down assures no problems with retrieving the ropes by sliding the position of the ropes until the joining knot is below the edge.
But now what?!
The ropes are repositioned so the knot is below the edge. If you rig your rappel, unclip from the anchor and begin rapping you won't get far. You will rap until the joining knot comes into the bottom of your rap device.
What to do instead?
In reply to: * You're the last one rapping on two ropes tied together and you're worried about the knot sticking on the corner of the ledge. Besides using the EDK, there's a bonus feature: with a sling attached to your harness (either clipped or girth-hitched, it doesn't matter), clip the end *behind* [above] the knot and begin to rappel. The 'biner will pull the knot along with you [as only one rope will be moving thru your rap device].*
Do not use this technique unless the anchor is metal: rap rings, biners, chain links, screw links, quick links, cold shuts
If the rap rope is touching webbing, do not use this technique as it will begin to cut the webbing anchor.
Universal alternative and far better technique:
while anchored at the rap station, adjust the position of the knot joining the two ropes placing the knot below the edge,
leave the knot below the edge for now,
near the rap anchor rig a temporary friction hitch on the ropes, I prefer the klemheist in 6mm cord, the klemheist may also be tied with webbing, attach the friction hitch to your harness with a double length (48-inch loop) sling girth hitched around your waist and leg loops, your temp friction hitch should stay near the anchor,
now pull up the rap ropes until you have the joining knot, and just below the knot rig your rappel device and rig your friction backup if you use one,
as an added safety (few will actually choose to do this) pull up 5-feet more rope and tie an overhand on a bight in both lines and secure both lines to your harness,
there will be slack rope at your feet, the slack will exist between your temp friction hitch and your rappel device,
carefully down scramble from the anchor, pulling your temp friction hitch as you descend, if you were to slip now the temp hitch would catch you (assuming you don't maintain a grip on it while you slip; tests have shown that most everybody will maintain a grip, oh well),
if the temp hitch does not catch you then you will continue to stumble/fall until your rappel device catches you and since you're at the top of a two rope rappel the weight of the two ropes will likely provide sufficient friction thru the rappel device that you might get control of your fall by grabbing/entangling the brake lines,
but if you use a friction backup to your rappel then that will most likely catch you even if you don't grab the brake lines (the friction backup will not see the full force of your stumble/fall because the rappel device will generate significant friction due to the weight of the two ropes hanging on it),
as you down climb to the edge your weight will come upon the rappel device with the temp friction hitch is still above the rope knot, that is why you used a double length sling to connect the temp hitch to your harness,
if you rigged a rappel backup friction hitch then your weight will be held solid by that, otherwise you will need to grab the brake lines from the rappel device to hold yourself,
while hanging from your rappel backup hitch, or holding the brake lines from the rappel device, remove the temp friction hitch,
if you tied a safety backup knot below the rappel device, untie this,
begin your rappel!
Most experienced climbers will choose to ignore the temp friction hitch and ignore the safety backup knot below the rappel device. They will adjust the rap ropes so that the joining knot is positioned below the edge, pull up both ropes and rig their rap device below the knot, and batman from the anchor to the edge, and this is not always a poor choice. If you choose this reasonably safe and very expedient method it's worth considering the safety backup knot below your rap device.
Choosing no safety knot while you batman, this technique has a high level DFU.
david yount.
"don't f--- up!"
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the_pirate
Oct 23, 2004, 4:32 AM
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Registered: May 20, 2003
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In reply to: this technique has a high level DFU.
I kind of understand what you are describing here (though your method seems unnecessarily complicated) from having performed similar maneuvers. But expecting someone to read what you wrote and then go out and perform this stunt is inviting fiasco.
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jakedatc
Oct 23, 2004, 4:48 AM
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Registered: Mar 12, 2003
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this thread is deemed unreadable by the A.D.D.A (attention deficiet disorder assocation)
:shock: :shock: :shock:
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