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Isolation loop for glacier travel

PostPosted: Wed Mar 24, 2010 8:02 pm
by alpinejason
I was just reading The Complete Guide to Climbing and Mountaineering and they have a nice photo (page 198 for those reading along) showing the middleman tied in using an short isolation loop. I like the idea. The rope is able to ride along side of you while walking better than other methods (butterfly and biners, etc.). I can't rationalize any downsides to this method, assuming the isolation knot is close enough to reach in order to prusik out. Any thoughts on way or the other?

PostPosted: Wed Mar 24, 2010 9:46 pm
by BrunoM
Do you have an illustration of this knot?

PostPosted: Thu Mar 25, 2010 3:55 am
by alpinejason
Yeah. Shoot. I'll have to scan it off next week. Stand by.

PostPosted: Tue Mar 30, 2010 8:54 pm
by alpinejason
As promised! Any thoughts now?

Image

PostPosted: Wed Mar 31, 2010 1:23 pm
by AndyJB444
I still prefer the alpine butterfly for its simplicity and quickness to tie into.

PostPosted: Wed Mar 31, 2010 2:39 pm
by Buz Groshong
alpinejason wrote:As promised! Any thoughts now?

Image


The actual knot that is replacing an alpine butterfly in the picture is nothing but a double overhand knot. Not particularly secure and the whole setup could be done with an alpine butterfly as well. You could still do that double slipknot and biner through the two loops (the tie-in) with an alpine butterfly; you'd just have to make the loop on the alpine butterfly extra long, but you really don't need all of that complicated bullshit.

PostPosted: Wed Mar 31, 2010 3:27 pm
by nartreb
I thought the question was about the overhand knot at the right edge of the picture. ("The rope is able to ride along side of you while walking..."). I'm no expert but I don't see a problem if it's kept short (and prusik loops are long enough, as noted in the OP). Mind you, I don't see a big advantage either. The rope won't magically ride up by your side just because there's a knot in it.

PostPosted: Wed Mar 31, 2010 8:21 pm
by rmick25
Petzl has some rock, ice, and snow climbing technique diagrams in there catalogs. I found this in the 2008 and 2009. It's similiar to the OP picture.

I haven't used this method either, but in theory it seems like it could help albeit more complicated.

Although were supposed to be talking about the knot on the right. Wouldn't a double bowline be preferable to the double overhand in the OP picture?

Image

PostPosted: Wed Mar 31, 2010 8:40 pm
by nartreb
I'm bad at 3-D visualization, but doesn't that latest diagram create a girth hitch at the belay loop? See the "attaching 2 slings" thread... (I know, ropes are a lot stronger than thin slings, but still.) Also, wouldn't that be hard to get out of if needed?

PostPosted: Wed Mar 31, 2010 9:09 pm
by Buz Groshong
nartreb wrote:I'm bad at 3-D visualization, but doesn't that latest diagram create a girth hitch at the belay loop? See the "attaching 2 slings" thread... (I know, ropes are a lot stronger than thin slings, but still.) Also, wouldn't that be hard to get out of if needed?


It does appear to create a girth hitch at the belay loop. To get out of it, just reverse the process in the diagram - except that you can't do that if the rope is under load.

PostPosted: Wed Mar 31, 2010 9:58 pm
by alpinejason
cool guys. thanks for the input. i realize it probably wouldn't help things to have the iso. loop but i guess the consensus is it probably wouldn't hurt much either. we won't be back on the snow until june. maybe we'll try it out for fun. it just seems like (in my head anyway) that it would ride a bit nicer on your hip when walking along. i think a couple people mentioned different knots than the overhand on a bight shown in the picture. i agree, i would probably just use an exaggerated butterfly instead.

as for the petzl diagrams. i think the idea is interesting. but i like to be tied in or butterfly with a biner. i don't like the thought of having to jump rope, literally, to escape the rope if something happens. i think this idea was "developed" by the europeans. maybe somebody has more info.?

PostPosted: Wed Mar 31, 2010 11:40 pm
by Jakester
Buz Groshong wrote:
nartreb wrote:I'm bad at 3-D visualization, but doesn't that latest diagram create a girth hitch at the belay loop? See the "attaching 2 slings" thread... (I know, ropes are a lot stronger than thin slings, but still.) Also, wouldn't that be hard to get out of if needed?


It does appear to create a girth hitch at the belay loop. To get out of it, just reverse the process in the diagram - except that you can't do that if the rope is under load.


Or just unlock and open your 'biner.

PostPosted: Thu Apr 01, 2010 2:35 pm
by Buz Groshong
Jakester wrote:
Buz Groshong wrote:
nartreb wrote:I'm bad at 3-D visualization, but doesn't that latest diagram create a girth hitch at the belay loop? See the "attaching 2 slings" thread... (I know, ropes are a lot stronger than thin slings, but still.) Also, wouldn't that be hard to get out of if needed?


It does appear to create a girth hitch at the belay loop. To get out of it, just reverse the process in the diagram - except that you can't do that if the rope is under load.


Or just unlock and open your 'biner.


It's unclear from the picture whether that's a belay loop or a biner. Of course, if it's a biner you wouldn't have to go through all of those gymnastics to get the rope hitched to it.

PostPosted: Thu Apr 01, 2010 3:41 pm
by Brad Marshall
alpinejason wrote:As promised! Any thoughts now?

Image


One thing I hate when I'm in the middle is the rope and knot rubbing against my thigh all day. To avoid this I've always tied in using an overhand knot with a very short loop and a small locking biner to my harness. The long tail after the overhand in the photo would make it worse for me. Also, seems like a complex process for such a simple matter.

PostPosted: Sun Apr 04, 2010 10:58 pm
by robgendreau
Brad Marshall wrote:One thing I hate when I'm in the middle is the rope and knot rubbing against my thigh all day. To avoid this I've always tied in using an overhand knot with a very short loop and a small locking biner to my harness. The long tail after the overhand in the photo would make it worse for me. Also, seems like a complex process for such a simple matter.


I've used the tail, but it's annoying on snow since it drops the rope into the step-on-it-with-your-crampons range. And it's harder to reach (it can become pulled tight close to the ground, and pull your waist down). It was more useful like this in broken rock.