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d.ben
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Jul 13, 2005, 7:54 PM
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In the trad issue of Climbing there was a tech tip for bailing on a 7mm cord while cleaning on lead. I'm trying to figure out if it would be just as safe to use that 5.5mm spectra cord instead of the 7mm nylon cord. My reason for wanting to do so is the spectra is smaller, half the weight, and twice as strong as the nylon cord. My concerns are since spectra cord is more slippery than nylon and the cord is smaller, am I going to be able to control my rappel easily. And will a friction knot backup even work on such thin spectra cord?
The cord I'm taliking about:
http://www.rei.com/product/1059.htm?vcat=REI_SSHP_CLIMBING_TOC
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dancefax
Jul 13, 2005, 7:59 PM
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one concern would be the heat generated to give the required friction, I vaguely remember this being an issue with spectra.
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mgoodro
Jul 13, 2005, 8:06 PM
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I won't speak for the safety of this tactic, though you make a good point with the strength issue.
I've been able to control a short rap on 6mm nylon cord with the BD ATC-XP, but I don't weigh much.
As for the friction knot, it's recommended to have a smaller cord for the knot to generate adequate friction. This gets tricky on a line that small.
The cord you are looking at is Spectra core with nylon sheath, so you may still be able to get adequate friction with the right device/combo. I would experiment with a short length and see if you can generate enough friction to control the descent.
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landgolier
Jul 13, 2005, 8:18 PM
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I think you'd end up with about 5 feet of hollow sheath at the ends of the line if you rapped this stuff, which would be pretty spooky. Also, do you really want a $200 bail line?
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veganboyjosh
Jul 13, 2005, 8:18 PM
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this is prolly gonna get labeled a troll, but here goes anyway:
what if you used two rap/belay devices in a row? like run the skinny rope thru one, and then thru the other...
i suppose that would be kinda like those fancy/weird multi-wrap rap devices that are around, huh?
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euroford
Jul 13, 2005, 8:24 PM
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in another thread i started we debated rap line strategies (the thread was started on me debating the use of some twins), and i ultimatly went with a 7mmX60m trail line/rap line. it worked out pretty good for us, but i sure wouldn't go with anything skinnier. we did a 50ish meter free hanging rap bailing off of Triple Exposure at Garden of The Gods, and even using it with a small rope compatable belay device (trango b52, in combination with a dry treated 9.8 lead line) it rapped pretty fast.
the 7mm is pretty dang light, and packs down pretty small. rather than think about how much weight you could save with the 5mm, think about how much your already saving (allot) with the 7mm :D
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landgolier
Jul 13, 2005, 8:24 PM
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2 devices in a row is a bit goofy, a canyoneering device might work, but regular device + munter on leg loop might be one way to actually make this work without a friction knot. Having to mule every time you want to stop and clean a piece would kinda suck, tho.
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davidji
Jul 13, 2005, 8:30 PM
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I tried a rap on a single 6mm cord, with an ATC-XP. Not enough friction for a secure rap (using 2 biners IIRC), so I added a leg wrap. Using your leg as a dynamic friction device isn't ideal, but it worked fine.
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d.ben
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Jul 13, 2005, 8:50 PM
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landgolier, why would I end up with 5 feet of hollow sheath at the end. & I would be able to get this cord at at least 30% off. with the light use it will encounter it should last me 3 years. That's worth the money to me. The reason I'm looking for the lightest possible option is too be as light and fast as I can be on Cannon. this rap line would mean I could take only one rope + rap line instead of two ropes. I'll have to see just how light and bulky a 7mm is.
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landgolier
Jul 13, 2005, 9:10 PM
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I've never played with more than a couple of feet of the stuff (for hexes), but with a spectra core and nylon sheath, the sheath has a tendency to slide. Play with it, you'll see. The stuff is stiffer than accessory cord, too, which might be better or worse for tossing. I would call BW and ask them if they know anything about how the stuff raps, maybe somebody has done it in a rescue application.
You're only going to save about 2 lbs on this deal. I'd say this is not a wheel that needs to be reinvented, but it's your call.
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shiggetyshiva
Jul 13, 2005, 9:13 PM
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You probably *could* get away with it, but would you really want to? With a 5.5 or a 7mm rap line I think either way I'd definitely want a mondo friction knot as a backup.
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montaniero
Jul 13, 2005, 9:40 PM
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I've used this ultralight setup in Chamonix a couple of months ago. An 8.1mm Beal Ice Line plus a 5.5 Dyneema trail line, can't get much ligther than this. IT WORKS....but friction was very poor with my Reverso and my stop hand grip had to be very very strong.
If I would use this setup again I would use a Reversino with two carabiners for increased friction. I guess that should do it. If this isn't enough you can always do a rope clipback, leg wrap and prussik backup. All of these should be more than enough.
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sspssp
Jul 14, 2005, 2:15 AM
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I've done raps on chord with this small of diameter. Here's how I do it and here are some things to think about.
Tie your lead line off at the anchor and have the first person down rap this as a single line. The small diameter rap/pull line is also tied off at the anchor and the first person down takes this line also (and untangles it on the way). The first person down ties off the rap/pull line (either to himself or the anchor) before (important!) taking himself off rappel (this prevent the second from rapping too soon).
The second ties the two lines together through the rap anchor. If communication conditions allow, the first down can tighten up the rap/pull line using an additional clove hitch.
The second now raps the lead line as a single line. The rap/pull line keeps the lead line from sliding through the anchor but the second does not incluce the rap/pull line in their rap device.
When you get to the bottom you can now pull the pull line to retrieve both ropes.
Pros:
You have a very light rap rope that can fit in a small fanny pack. You might carry it when you wouldn't carry a heavier rope.
Cons:
That small of line is a real pain to deal with. Tangles, the wind, you name it, the handability is zip.
If you feed the lead line through the rap anchor, this has the advantage that the knot is on the "far side" so if your partner doesn't have the rap/pull line tied off correctly (or if it gets severed), then the knot will jam in the anchor and you would probably be ok with your rap. However, in this case, you have to pull the small line. This is really difficult and time consuming. If the ropes jams, you don't have anything that you can lead back up with, or even, cut off a short piece and keep rapping. If you tie it with the rap/pull line through the anchor, it is very easy to pull the lead line. However, your safety is much reduce and you are depending on your partner to have correctly tied off the rap line and the integretity of the rap line (but this is how I usually do it).
Bottom line: I've found it is an "ok" setup for in-an-emergency I have to do a double rope rap, but I'm really planning on walking off. When I am planning on rapping, I take a 8.1mm dynamic line.
Note:
Actually, it is quicker and safer to tie the two lines together (through the rap anchor) before the first goes down. After tieing the lines together, the lead line is then [additionally] tied off to the anchor (clove hitch or double figure eight). So after the first raps, the second only has to untie the clove hitch and the two lines are already tied. If communication is difficult, the second has got to keep some tension in the rap rope or else there is the danger that the person up top could untie the clove hitch too soon.
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euroford
Jul 14, 2005, 3:54 PM
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reading this thread has again convinced me that i'm correct in going with my 7mm. thinner lines just seam foolishly sketchy and problematic for a variety of reasons. whilst on the other hand the 7mm is pretty dang light, but still robust enough to have a variety of uses and not require any special procedures.
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d.ben
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Jul 14, 2005, 8:55 PM
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I called Blue Water they said the heat would be a problem on spectra. I'm going with the 7mm. Thanks for all the help.
Dom
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norushnomore
Jul 14, 2005, 9:24 PM
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Which 7mm are you having in mind (brand model)?
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montaniero
Jul 14, 2005, 9:33 PM
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I don't know what BlueWater have told you but Dyneema is very widely used as a trail line. Friction heat on the Dyneema line generated by the belay device shouldn't be a problem because you are always going to be weighting more the thicker rope while you abseil. The thinner trail line would pass through the belay device much faster than the thicker dynamic rope.
The Dyneema trail line system is used by many guides in the Alps in a very specific situation: routes where you don't need double ropes to climb but still had to abseil to return to base.
Nevertheless, I believe there is a better reason for going for the 7mm. Perlon instead of the 5.5mm. Dyneema: $200 is a lot of cash for some trail line that you are only going to be using in very specific routes. The reason guides use it is because they can get for free/big discount! ;)
Jean-Christophe Lafaille used it for fixing a small part of his solo climb in the South face of Shishapangma, but again..he got it for free! ;)
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d.ben
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Jul 15, 2005, 3:55 PM
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The lady form blue water said the heat generated from a rap could damage spectra. I plan on rapping on this cord alone, and only in case our lead rope is damaged or stuck and we have to bail. Otherwise I plan on walking off. I'm not sure what brand of 7mm I'll get. Any suggestions? I'll be getting at least 30% off the cord.
Dom
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landgolier
Jul 15, 2005, 4:06 PM
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Blue water makes a 7mm dynamic prusick that I always thought would be good for rapping with alongside a normal single since it stretches a bit more than normal static and won't be as annoying as 1 static and 1 dynamic, but it sounds like for this particular instance you wouldn't care. Might be good if you want to keep it for later, though. Granted I've never rapped on this stuff, just use it for prusicks, so you'd have to check it out for yourself. It has a slightly different sheath weave than other accesory cord, check it out and see how it runs, I'd like to know.
EDIT - BTW, the first time I bought this stuff, I thought it was normal accessory cord. If anybody out there has a 7 mil bail line that is yellow and blackish/dark blue, that's the stuff. Let us know how it goes.
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euroford
Jul 15, 2005, 5:12 PM
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thats not the stuff that i have, my bluewater 7mm line is a red/yellow weave i think. but now that i know about it i wish thats what i had. in fact i bet it would also make a pretty great glacier line as well maybe?
fwiw: the 7mm makes a great bail line, tag line, rap line and light haul line, in fact i'd even use it for a fixed rope/jug line on lower angle stuff. you'll get allot more use out of it than just simply a uber skinny dedicated 'bail' line.
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montaniero
Jul 15, 2005, 5:52 PM
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In reply to: I plan on rapping on this cord alone, and only in case our lead rope is damaged or stuck and we have to bail.
I don't think that's the best thing to do. I thought you wanted the Spectra as a trail line to retrieve the dynamic rope in a single-rope rappel system.
If I had the choice, abseiling on 7mm. perlon would be my very last choice. If the rope is damaged or stuck, I would repair/cut the damaged bit or climb up and retrieve the stuck rope. 'Cause if a dynamic rope gets damaged or stuck on a multi-abseil situation, just wonder what could happen to the 7mm. perlon on the remaining abseils....
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d.ben
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Jul 15, 2005, 6:53 PM
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If I trust 7mm cord as an anchor, then I trust it to rapp on. I'm not gonna be using this to go sport tradding and rapp on it all day. It's for "oh shit our rope got cut in half by that falling death block" or other such " oh fuck" situations. If I though I was gonna have even a 25% chance of needing to rapp off I'd just bring another lead rope like last time. Climbing Magazine didn't seem to have a problem with rapping on a line this size since they had a tech tip describing just that. I do see the concern with it getting stuck easlily pulling it. Any other reasons you're so against it? Can I get some more trad veteran feedback on this to help me out?
Dom
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euroford
Jul 15, 2005, 8:57 PM
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yeah but thats the glory of it. the 7mm is good enough that you don't need another big ass lead line just to rap off.
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d.ben
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Jul 15, 2005, 9:39 PM
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I'm with you euro ford. Have you rapped on a 7mm before?
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