|
|
|
|
blitz933
Aug 27, 2006, 6:39 AM
Post #1 of 14
(2548 views)
Shortcut
Registered: Aug 10, 2006
Posts: 27
|
I'm relatively new to climbing in general (about 6 months exp) and Trad climbing specifically (about 3 months exp), but I have this comment, and am just looking for opinions.
Specifically, why are all cordalettes made from Static line? They're supposed to equalize the load on the anchors, so wouldn't a Dynamic rope do a better job? If you weren't perfectly equalized to begin with (or your direction of loading changes), wouldn't a Dynamic rope allow even the least equalized point to absorb some of the load, especially in a lead fall?
I'm not suggesting this for hanging biviouacs or the like, just belays you expect the potential for a leader fall on. I know the Dynamic qualities of the rope have the potential to move the Belayer significantly, but as long as you keep the falling climber locked off safely, I don't see any danger in this method. Now, this would require you to climb with a 10mm or larger cordalette slung to your harness, but with the much higher potential for shock absorbtion, wouldn't the few extra oz's be worth it?
Comments please . . .
|
|
|
|
|
beesty511
Aug 27, 2006, 7:10 AM
Post #2 of 14
(2548 views)
Shortcut
Registered: Mar 4, 2004
Posts: 336
|
the problem with cordalettes is that each leg stretches proportional to its length: the longest leg stretches the most and the shortest leg stretches the least. so the shortest leg will end up bearing the majority of the load. it doesn't matter if the cordalette is made out of dynamic rope or steel cable because any material stretches and the shortest leg will stretch less than the other legs.
in addition, making a cordalette out of dynamic rope would make the cordalette bulkier and heavier. try tying a master point knot with 6 strands of 10mm dynamic rope.
|
|
|
|
|
j_ung
Aug 27, 2006, 1:09 PM
Post #3 of 14
(2548 views)
Shortcut
Registered: Nov 21, 2003
Posts: 18690
|
Why 10mm? Why not, say, 8.5? And the problem with the short leg... I'm wondering the same thing as the OP, how would a more dynamic cord affect the situation? I think this is a good question.
|
|
|
|
|
tgreene
Aug 27, 2006, 1:23 PM
Post #4 of 14
(2548 views)
Shortcut
Registered: Oct 22, 2003
Posts: 7267
|
Given the neccessity to be fully equalized and absorb shockloads, why not opt for utilizing heavy-duty bungee cord instead..?
|
|
|
|
|
davidji
Aug 27, 2006, 3:00 PM
Post #5 of 14
(2548 views)
Shortcut
Registered: Jan 30, 2003
Posts: 1776
|
In reply to: Specifically, why are all cordalettes made from Static line?
In reply to: Now, this would require you to climb with a 10mm or larger cordalette slung to your harness, but with the much higher potential for shock absorbtion, wouldn't the few extra oz's be worth it? |
|
|
|
|
beesty511
Aug 27, 2006, 5:01 PM
Post #6 of 14
(2548 views)
Shortcut
Registered: Mar 4, 2004
Posts: 336
|
In reply to: how would a more dynamic cord affect the situation |
|
|
|
|
david_smithrock
Aug 27, 2006, 5:16 PM
Post #7 of 14
(2548 views)
Shortcut
Registered: Jul 12, 2006
Posts: 361
|
It's a bulk issue. 7mm line is about as thick as I'd want to carry for a cordalette, and static spectra, etc. is stronger than dynamic rope. The amount of dynamic stretch in that length of dynamic rope doubled over wouldn't be much anyway.
Besides, if you really are worried about shock loading your anchor out of the wall, you shouldn't be using that anchor!
If you get to a point (in the mountains, etc) where you really don't trust your anchor and don't have any options :shock: it is probably better to belay off your waist, as you and your muscles are the best shock absorber.
|
|
|
|
|
colotopian
Aug 27, 2006, 5:41 PM
Post #8 of 14
(2548 views)
Shortcut
Registered: Dec 17, 2005
Posts: 518
|
In reply to: If I want to anchor in with climbing rope, I anchor in with the climbing rope.
Nicely done!
|
|
|
|
|
blitz933
Aug 27, 2006, 6:48 PM
Post #9 of 14
(2548 views)
Shortcut
Registered: Aug 10, 2006
Posts: 27
|
Bulk really shouldn't be an issue, you can get dynamic rope down to 8.5 or 9mm in size, and at that diameter it's still strong enough to arrest a leader fall with lots left over. There would be a few extra oz's of weight and a little bit more bulk involved, but that doesn't really bother me.
My argument against tying in with the climbing rope is that your now much more stuck in your position (with a cordolette I can tie off/release the belay and am instantly free in a rescue/emergency/leader swap), you shorten your avaliable rope, and I've never seen a good way to rig the climbing rope where the anchors are actually equalized (or even close).
However, this thread really isn't about debating the merits of different anchor setups, rather about the materiel used for one of them.
It's not easy tying a knot in 6 strands of 10mm rope, but it's do-able (I just did). Given the difficulty of tying that knot however, I'd suggest getting 9mm or smaller single dynamic rope to use for this cordalette. I personally use 7-8mm static cord for my cordalettes anyway, the extra mm or two of diameter and 2-3oz of weight won't bother me a bit.
The point about the shortest loop absorbing more of the load than the longer loops is probably correct, but with a Dynamic cordalette I think that effect will be minimized (in fact, just loading the cordalette with body weight should take it out of the equation, all the loops will stretch a bit with just that much on them).
This might also lessen one of the bad points of the cordalette, that they aren't multidirectional. If your direction of loading changes significantly, the Dynamic cordalette has the potential to stretch and distribute the load more evenly (it won't be equalized, but better than nothing) than a static cord, where that full load will fall on just one or two pieces instead of the entire anchor.
Comments?
|
|
|
|
|
ctardi
Aug 27, 2006, 7:17 PM
Post #10 of 14
(2548 views)
Shortcut
Registered: Oct 8, 2004
Posts: 1278
|
If load direction changes, it doesn't matter if it's dynamic or static, it will still unload at least one peice.
Why go with dynamic? It's most likely cheaper to get 7mm cord than it is to get some dynamic rope. The static is smaller, lighter, easier to tie...
|
|
|
|
|
pointy
Aug 27, 2006, 8:28 PM
Post #11 of 14
(2548 views)
Shortcut
Registered: Jul 8, 2004
Posts: 17
|
Yates makes dynamic cord for a cordelette, though i couldn't seem to find it on their website. So does Bluewater (see Davidji's post above).
Recently there was a thread with a link to an AMGA study of different cordelette materials.
|
|
|
|
|
heiko
Aug 27, 2006, 8:44 PM
Post #12 of 14
(2548 views)
Shortcut
Registered: Mar 3, 2005
Posts: 1505
|
I've been using a few meters of dynamic rope (twin) as a cordalette for the last few months, and so far the bulk issue has not bothered me very much.
|
|
|
|
|
david_smithrock
Aug 28, 2006, 4:45 PM
Post #13 of 14
(2548 views)
Shortcut
Registered: Jul 12, 2006
Posts: 361
|
To each his own. I'm looking at my 8.5 dynamic line, and 20 feet of it seems pretty bulky; but if it works for you guys, it wouldn't bother me if someone was belaying me off it. If I asked why they were using it and they said they didn't want the anchor to get shock-loaded out of the wall, I would be worried. Not only is the dynamic effect negligible compared to the rope the belayed climber is already using, but you should always trust your anchors, or not be using them.
Again, trusting your anchor shouldn't be an issue, but if it is, use a cordalette (static, dynamic, etc), secure yourself to the master point, and belay off the waist. This is much more dynamic, to the point you may be able to hold all the climbers weight with your own body if you have a good stance. Although it takes a few extra steps and some spare gear to transfer the weight of the fallen climber to the anchor (for self-rescue, etc) at least it actually has a significant dynamic effect! (If you're worried about you anchors doing the "vertical limit" out of the wall, that is :wink: )
|
|
|
|
|
beesty511
Aug 28, 2006, 9:24 PM
Post #14 of 14
(2548 views)
Shortcut
Registered: Mar 4, 2004
Posts: 336
|
In reply to: The point about the shortest loop absorbing more of the load than the longer loops is probably correct, but with a Dynamic cordalette I think that effect will be minimized (in fact, just loading the cordalette with body weight should take it out of the equation, all the loops will stretch a bit with just that much on them).
consider these points:
1) assume you initially tie the cordalette so that all pieces of the anchor are equalized(which is impossible to do by the way)
2) the legs stretch proportional to their length
3) you hang your body weight on the anchor
based on 1-3, which leg has more force on it while you are hanging from your anchor.
ok, let's say now you understand what is going on with stretch. so you decide to get a little tricky. instead of tying your cordalette so it is perfectly equalized when no weight is on it, you leave a little slack in the short leg, and somewhat less slack in the next shortest leg. then you hang your body weight on the anchor. using a force measuring device, you discover that you managed to tie a cordalette that pefectly equalized the pieces with you hanging on the anchor. congrats! the perfect anchor technique! right?
nope. what happens when your leader falls on the anchor?
|
|
|
|
|
|
|
|
|
