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Re: [brunoschull] Single rope and lightweight rap line:
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billl7
Dec 20, 2010, 1:36 PM
Views: 7432
Registered: Oct 13, 2005
Posts: 1890
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I've done this with a 10+ mm dynamic and a 6 mm static. If you simply thread both in the belay device, the fat will still see more of the weight (more friction) which causes the rig to want to shift through the attachment at the anchor and so cause uneven rope ends at the bottom. Place the joining knot so it works against that shifting (i.e., would run up against the rap rings or chains). Still, there is some risk that in some situation the knot will pull through the attachment point at the anchor.
Although not quite the same set up as the above, the yose rap accident is sobering. Keep your wits about you at all times.
Once, I put an addtional munter above the belay device in only the static to help balance the load between the two strands. Seemed to work okay but haven't done it enough to feel for certain it gave a good balance. And if one had to stop the rap and ascend the rope, that extra munter might make for a bit of a hassel.
vinnie83 wrote: I've never had any trouble with the EDK.
I also use the EDK. Since the failure mode of the EDK in this use is to roll or capsize towards the tails, I tie the EDK such that the skinny has to roll over the fat strand for it to do the first roll.
If this rig is set up to pull the skinny first (see part of using knot to work against the shifting), be watchful of anything that causes friction during the pull and try to prevent it (edit: extra extra watchful). Pulling the skinny can be rather easy with a straight drop from fat rap rings to the pull point. Or it can be very very hard if, say, there is a low angle slap below the anchor that transitions to vertical terrain. The drag from a fat rope running over such a transition gets amplified when pulling on a skinny tag line. Bring gloves?
Bill L
(This post was edited by billl7 on Dec 20, 2010, 1:41 PM)
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Edit Log:
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Post edited by billl7
() on Dec 20, 2010, 1:41 PM
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