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wbw
climber
'cross the great divide
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May 10, 2010 - 03:13pm PT
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Auto-x, have you ever measured the largest diameter of the figure 8 follow thru rappel knot, and compared it to the EDK. The name doesn't bother me; I just have never thought that the advertised advantages, such as doesn't snag on the pull as much as other knots, are as significant as people say.
I don't generally back up the figure 8 when I use it for rappeling, to keep the bulk of the knot as low as possible. Maybe the main reason I like it is that I have used it as my system for rappeling for so many years, in many different rappeling situations, without having any difficulty.
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Gene
Social climber
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May 10, 2010 - 03:17pm PT
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Any opinions/consensus on the knot(s) to tie in the bottom ends of the rap ropes? Tie both ropes together with a huge knot? Knots separately in each strand? What knot to use? I typically tie the bottom strands together with a figure 8 on a bight.
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snaps10
Mountain climber
Visalia, CA
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May 10, 2010 - 03:17pm PT
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Personally, I weight and unweight my prussik, on rappel, hundreds of times a year. I don't have a problem getting them undone, never have. I use 6mm for my prussiks for personal climbing and 8mm for rescue. Always tandems for rescue if I may be adding a load to my own body weight. Always triple wrapped.
I rap with my prussik above the rack or device, always. My thought process is:
I can keep the prussik at whatever distance I want away from my body, and it will grab without jerking me by just letting go.
If I need to weight the prussik, I don't have to jam up my rap device to get it to grab. Consequently, I don't have to unjam my rap device when I want to continue on my rappel.
Someone mentioned the whistle test. I challenge them to put on their autoblock below the device, start to wrap, then whistle and let go without wetting their pants. With a prussik above it is no big deal.
I tie barrels in the bottom, and never tie them together, it can be a twisted mess sometimes if they're tied together and you're using two different diameter ropes.
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Mighty Hiker
climber
Vancouver, B.C.
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May 10, 2010 - 03:29pm PT
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If you want to be certain not to rappel off the ends of ropes, tie them together in a double figure eight. Either that, or clip a piece of gear to the bottom of each rope - then there's no chance of a rope slipping through your rappel setup.
Several accidents, including I believe Jim Madsen's on El Capitan in 1968, showed that knots can feed through carabiner brakes, at least.
Chiloe's carabiner brake setup could use a second cross-carabiner.
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Chiloe
Trad climber
Lee, NH
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May 10, 2010 - 03:45pm PT
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Chiloe's carabiner brake setup could use a second cross-carabiner.
Agreed, but I didn't have a fourth oval. I would have used a munter instead, if I
had a large locker along. What you see there was rigged unexpectedly with gear
that happened to be at hand. It worked.
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Gene
Social climber
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May 10, 2010 - 03:50pm PT
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Knott to pick nits, but
Agreed, but I didn't have a fourth oval.
Wouldn't any biner work as the cross piece?
g
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tradmanclimbs
Ice climber
Pomfert VT
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May 10, 2010 - 04:13pm PT
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Pate, any multi pitch I use doubbles. Any single pitch I use singles. there are exceptions to every rule or method though. Long single pitch ice climbs its back to the doubbles. Multi pitch spurt climbs with anchors every 30m I use a single. Long single pitch desert cracks are better with a single and a tag off the back of the harness. 2 ropes in the crack get in the way of the feet. Got to be flexable and use diferent systems for diferent aplications. Just make sure you have em all wired.
BTW when I use the tag line its one of my 8.6mm doubble ropes and I rap both lines, no tricks.
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Gary
climber
Desolation Basin, Calif.
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May 10, 2010 - 04:44pm PT
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In the accident thread coz posted:
Futhermore, jamming knots and all this trick stuff is killing people use the kiss system.
Yes! Keep it simple.
Keep it simple and safe.
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ec
climber
ca
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May 10, 2010 - 04:52pm PT
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use 5 mm Spectra cord (not kevlar), about 5.5 feet long, tied with a triple fisherman knot[...It's tempting to tie a prussic loop out of accessory cord. Much cheaper. But also way weaker. - DR
Doug is strength the issue in a prussik? Spectra has a very low melting point. I never went there because of it...however I did some other pretty stupid things with it...like a single fixed line to jug on...
Spectra has several difficult issues. The melting point is very low, 147 °C or 297 °F, not much warmer than boiling water.
from: http://www.caves.org/section/vertical/nh/49/cthsc/cthsc.html
 ec
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Chiloe
Trad climber
Lee, NH
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May 10, 2010 - 04:55pm PT
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Wouldn't any biner work as the cross piece?
Nope, not the ones I had. Tried 'em.
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Brian in SLC
Social climber
Salt Lake City, UT
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May 10, 2010 - 05:09pm PT
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From the crossposted analysis:
Pull cords of that diameter have a much lower melting point.
Melting point of a fiber doesn't really change per se with the diameter of cord it's woven into.
Changing the amount of friction might generate more heat, related to diameter methinks. But, not melting point.
Anyhoo...sad deal.
I use a pull cord and rappel from a Gri Gri quite often. Also use a pull cord and single dynamic rope with an ATC too, but, I usually rappel them together. Most often from a "knot block". Sometimes from a figure eight on a bite to which sometimes I attach a locking biner and clip it back through. Just depends on the chanee I think the ropes will hang up or not.
Always try to jam the knot against a link/ring that I know won't allow the knot to slip through. Did have one pop through in the Tetons (from Guides Wall) and was glad I was rappelling both the pull cord and the lead line. Just adjusted the friction on the cords to keep the smaller diameter pull cord from creeping.
Take care out there...
-Brian in SLC
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kev
climber
A pile of dirt.
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May 10, 2010 - 05:33pm PT
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So unless you're trying to go ultra light then why not take 2 lines (or a single 70 or 80)?
I have a 8.9, and a 9.4 lead lines and an 8 mil tag line. If the route requires two lines I take the 8 mil plus one of the lead lines. Not too much weight here. Just seems easy and you've got the flexibility of two ropes (even if one is static) in a pinch.
kev
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mucci
Trad climber
The pitch of Bagalaar above you
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May 10, 2010 - 06:09pm PT
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I just don't see the advantage in using a 6 or 7mm pull cord rather than a 8 or 8.5 1/2 rope?
How much wight are we talking here?
You can lead on a 1/2 rope in a pinch.
Lighter than a single rope.
Can someone explain to me how using this method with the backup biner, a better way to avoid snags when pulling?
There is so much shite going on with that EDK/pull cord method, 2 or 3 knotts, and a biner that all have to come down when pulling.
I guarantee that I can rig a rappel with a figure 8, or fisherman's in the SAME amount time it takes to set this "LIGHT and FAST" rappel.
Please enlighten me.
Mucci
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August West
Trad climber
Where the wind blows strange
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May 10, 2010 - 06:21pm PT
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There is a pretty big difference between 7mm and 6mm in both bulk and weight. I can treat a 7mm as a rope and get it to grip the rap device, not so a 6mm.
The main advantage that I see for the 6mm, is you can coil it up and stick it in a summit pack or fannypack. Cannot really do that with fatter ropes. So you either trail it, with all those hassles, or have a coil on your back (possible in addition to summit pack).
I played around with a 6mm (and a 5.5mm) tag line. I found it not worth the trouble. At best, take when you don't expect to use it (planning on walking off, but don't summit).
I never liked the biner backup because of fear of it getting caught when pulling the ropes. As an alternative, we would set up the rope/pull line through the anchor but then tie the main rope off straight to the anchor, for the first one down to rap a single line (first down also comes down with the pull line). Once the first down gets to the next anchor, he can tie the pull line straight to the anchor (or his harness) so that the main rope cannot slip when the second comes down. Not saying this is safer, since it relies on the first correctly tieing the pull line off before the second starts down, but it requires no backup biner.
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ontheedgeandscaredtodeath
Trad climber
San Francisco, Ca
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May 10, 2010 - 06:24pm PT
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I've thought about the single rope/tag line method and can't say I see the point.
In situations where weight is truly critical it makes no sense to bring one larger diameter rope and 180+ feet of 5-6mm cord that's only good for one thing.
Seems like it would take longer to set up-- I know I would be spending a lot of time making sure it is rigged right and there is a lot to look at.
Looks like a cluster to pull over/through anything. Straight down from chains is one thing, but...
Use of an auto locking belay device to rap increases the possibility of giving the anchor a good jolt.
Rapping on a single line has it's own set of problems/risks.
There are a million rap anchors out there with different set ups, the single rope method seems to rely on links. Other methods can be used no matter what one comes across.
Dunno, to each his own.
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Ken M
Mountain climber
Los Angeles, Ca
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May 10, 2010 - 08:02pm PT
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What I find troubling, is the statement of simple opinions, when there are actually facts (that is, actual testing) of the EDK vs Fig 8.
In the below comprehensive test, they found:
"The flat-overhand is clearly better than the flat-figure-eight. The flat-eight is represented three-to-one in the accidents despite (to the best of my knowledge) many more climbers using the overhand. The flat-eight also starts flipping at a lower load (750 lbs vs 1400 lbs for well-tied, 110 lbs vs 200 lbs for badly tied) than the overhand, and it eats two to three times as much tail in each flip."
http://www.xmission.com/~tmoyer/testing/EDK.html
So the actual testing is very clear about which is better, not just opinion and a series of experiences.
Here are some other actual data sites and comments:
Preferred Knots for Use in Canyons - from Bushwalker's Wilderness Rescue Research Page. Long paper with pull-test data on a number of knots used to join ropes, including measurement of the force to drag the knots across edges. The author concludes that the flat-overhand is his preferred choice and that the flat-figure-eight is dangerous.
Chockstone Tech Tips/JoinRopes - good pictures of knots and discussion. No testing. They express a preference for the figure-eight follow-through, and show the flat-figure-eight knot with a skull-and-crossbones.
Edelrid tests - (in German, with much of it translated into English). Test data on three knots: the flat-overhand, the double-fisherman's tied as a flat-knot (photo at right from their page), and on a new type of flat-knot. He translates it as "Triple Fisherman's", but it's not. The flat-double-fisherman's didn't invert at all in his tests. Cool! People have asked me about it, but I haven't done any tests.
Abseil Knots - from NeedleSports. Pull-test data on the flat-overhand and flat-figure-eight, including data on frozen ropes. The author prefers the flat-overhand with a second overhand as a safety (he calls this the double-overhand). He calls the flat-figure-eight the "instant-death knot."
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mucci
Trad climber
The pitch of Bagalaar above you
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May 10, 2010 - 08:08pm PT
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^^^^
Nothing says safe like a properly tied 8 or fisherman with overhand finish.
Can't say the same for the EDK.
Oh and I don't know the actual #'s but I rarely see the EDK being used, and I highly doubt it is the knott used by "MOST" for rappeling as stated above.
Edit: I thought we were talking about the inline 8. I meant the quoted sentence above from the testing company.
No reason for a "Flat" knott in my opinon.
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Ken M
Mountain climber
Los Angeles, Ca
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May 10, 2010 - 08:10pm PT
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I didn't state that, the tester stated that. His experiences are probably vastly larger than the small number of places that you climb.
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climbingcook
Trad climber
sf
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May 10, 2010 - 08:12pm PT
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I've never seen anyone use a flat figure eight to rap on. When people are talking about using a figure eight to join two ropes to rappel, they're talking about using a flemish bend.
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