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Edk ok with different diameters?

Original Post
Optimistic · · New Paltz · Joined Aug 2007 · Points: 450

Would the edk/overhand knot be adequate for joining a 9.5 dynamic and a 7mm static? If not,what knot is preferred, and why? Thanks, David

Ryan Kempf · · Boulder, CO · Joined Jul 2011 · Points: 371

Yes, tie your EDK and tighten it, then tighten each strand individually. If your really concerned about it tie 2 EDK's a few inches apart. Make sure to leave lots of tail as always with EDK's.

Enjoy your long rappels and safe climbing.

Chris Massey · · Unknown Hometown · Joined Oct 2012 · Points: 5

Long tails, agreed... Just watch not to rig your rappel into the tails. It has happened, almost to me. The longer the tails the easier it is to do.

wivanoff · · Northeast, USA · Joined Mar 2012 · Points: 674
Optimistic wrote:Would the edk/overhand knot be adequate for joining a 9.5 dynamic and a 7mm static? If not,what knot is preferred, and why? Thanks, David
Asked and answered before
mountainproject.com/v/joini…
Ryan Nevius · · Perchtoldsdorf, AT · Joined Dec 2010 · Points: 1,837
wivanoff wrote: Asked and answered before mountainproject.com/v/joini…
Beat me to it. Thread closed. Also, the thread you linked to (specifically, rgold's comments) should be "sticky."
Xam · · Boulder, Co · Joined Dec 2011 · Points: 76

There has been a lot of these threads lately so I would like to ask a follow up to the original question. I just bought 60m of 6mm cord to used with 9.x mm singles on routes I do not intend to rap but might need to bail on ... think alpine moderates. I am very familiar with the biner block method and have used it many times canyoneering...no need to rehash that here. I am also familiar with the rope 'travel' issue and the possibility of the knot popping through the link/ring. I also know how to back up a knot block with a biner so no need to link the petzl page or diagram. So my questions:

1) How many folk have rapped directly off the setup I just described (no biner block, 6mm / 9.xmm double rope rap) and what was their experience?

I know I am going to die and I know may people do not recommend this method but please just tell me if you have done this and if it worked out ok and what I should pay attention to. Also, no need to tell me I should use 7mm cord, 8mm cord, a twin or a half...I have already considered the weight and safety trade-offs of this approach. Just looking for real world practical experience comments on this setup.

2)Tell me if this seems like a reasonable backup for this method: Assume two climbers. Send first rappeler down with a biner block and/or backup (e.g. petzl). First rappeler heads down and clips skinny cord to belay loop once down via fig 8 on a bite. Second rappeler removes biner block and/or backup to eliminate snags on the pull and heads down. Now if the second rapeler losses control of the skinny rope and the knot pops through ring, they are backed up. This idea originates with a post I saw from bearbreeder earlier.

You could even take this idea a bit further and have the first rappeler tension the cord and the second do a single rope rape on the fat rope...but this seems excessive, complicated and would increase the force on the anchor...but an idea none the less. Comments?

Thanks.

Tim Stich · · Colorado Springs, Colorado · Joined Jan 2001 · Points: 1,520

YES.

(Read above for details.)

rgold · · Poughkeepsie, NY · Joined Feb 2008 · Points: 526

I'd also say yes to (2), but would suggest considering two modifications at least some of the time.

(A) Set up the rappel so that you'll be pulling the fat rope. This means you are not relying on the knot jamming in the rings. This system will have to be tied off (there are various obvious ways) so that the first person can rappel on it.

(B) When the first person gets down, they anchor the thin rope to the next rappel anchor and the second person undoes the tie-off does a single-strand rappel on the fat rope.

Doing things this way has two advantages which could avoid a serious epic.

(i) The primary advantage is if the rappel hangs after the rope comes free from the anchor, the party will have the fat rope. In the usual method, the party would be left with a 6 mil rope.

(ii) A second advantage is that it is a lot easier to pull the fat rope then the thin one, and in high-friction situations this could be the difference between being able to pull the rappel and not being able to pull the rappel.

The main disadvantage is that the second person down is entirely supported by the 6 mil strand, a somewhat scary prospect although 1700 lbf breaking strength is adequate if you don't go wild and crazy; I'd rather use 7 mil with a 2600 lbf breaking strength for this, which is still scary enough. In either case, you probably wouldn't want to be doing this with a worn or nicked tag line.

A second disadvantage is that some rap anchors might not be appropriate for upward pulls. In this case, a counterweight rappel could still work, with the thin rope anchored to the first climber rather than to the anchor.

Josh Brown · · Unknown Hometown · Joined Apr 2008 · Points: 20

Another point to consider when one rope is static is that it should be a bit longer than the dynamic to account for the rope stretch. This way you can avoid uneven ends and a potential rap off the ends ( or just knot the ends)

Optimistic · · New Paltz · Joined Aug 2007 · Points: 450
wivanoff wrote: Asked and answered before mountainproject.com/v/joini…
Sorry! I find searching the site is pretty hit or miss (eg, I was using the word "different" instead of "unequal"). Thanks for posting the link.
bearbreeder · · Unknown Hometown · Joined Mar 2009 · Points: 3,065
rgold wrote:I'd also say yes to (2), but would suggest considering two modifications at least some of the time. (A) Set up the rappel so that you'll be pulling the fat rope. This means you are not relying on the knot jamming in the rings. This system will have to be tied off (there are various obvious ways) so that the first person can rappel on it. (B) When the first person gets down, they anchor the thin rope to the next rappel anchor and the second person undoes the tie-off does a single-strand rappel on the fat rope. Doing things this way has two advantages which could avoid a serious epic. (i) The primary advantage is if the rappel hangs after the rope comes free from the anchor, the party will have the fat rope. In the usual method, the party would be left with a 6 mil rope. (ii) A second advantage is that it is a lot easier to pull the fat rope then the thin one, and in high-friction situations this could be the difference between being able to pull the rappel and not being able to pull the rappel. The main disadvantage is that the second person down is entirely supported by the 6 mil strand, a somewhat scary prospect although 1700 lbf breaking strength is adequate if you don't go wild and crazy; I'd rather use 7 mil with a 2600 lbf breaking strength for this, which is still scary enough. In either case, you probably wouldn't want to be doing this with a worn or nicked tag line. A second disadvantage is that some rap anchors might not be appropriate for upward pulls. In this case, a counterweight rappel could still work, with the thin rope anchored to the first climber rather than to the anchor.
the biggest disadvantage is that you are entirely reliant on your partner to remember to set it up properly

if they forget or screw it up ... or if your communication is poor on raps, a frequent occurrence, you die

the other disadvantage is that you cant simply pull one strand through once your at the anchors ... youre going to have to pull the the entire thing down before rethreading

using a ~8mm half rope as a tag line solves alot of these issues as it allows you to lead back up in an emergency

;)
Brie Abram · · Celo, NC · Joined Oct 2007 · Points: 493
Xam wrote:There has been a lot of these threads lately so I would like to ask a follow up to the original question. I just bought 60m of 6mm cord to used with 9.x mm singles on routes I do not intend to rap but might need to bail on ... think alpine moderates. I am very familiar with the biner block method and have used it many times canyoneering...no need to rehash that here. I am also familiar with the rope 'travel' issue and the possibility of the knot popping through the link/ring. I also know how to back up a knot block with a biner so no need to link the petzl page or diagram. So my questions: 1) How many folk have rapped directly off the setup I just described (no biner block, 6mm / 9.xmm double rope rap) and what was their experience? I know I am going to die and I know may people do not recommend this method but please just tell me if you have done this and if it worked out ok and what I should pay attention to. Also, no need to tell me I should use 7mm cord, 8mm cord, a twin or a half...I have already considered the weight and safety trade-offs of this approach. Just looking for real world practical experience comments on this setup. 2)Tell me if this seems like a reasonable backup for this method: Assume two climbers. Send first rappeler down with a biner block and/or backup (e.g. petzl). First rappeler heads down and clips skinny cord to belay loop once down via fig 8 on a bite. Second rappeler removes biner block and/or backup to eliminate snags on the pull and heads down. Now if the second rapeler losses control of the skinny rope and the knot pops through ring, they are backed up. This idea originates with a post I saw from bearbreeder earlier. You could even take this idea a bit further and have the first rappeler tension the cord and the second do a single rope rape on the fat rope...but this seems excessive, complicated and would increase the force on the anchor...but an idea none the less. Comments? Thanks.
I have spent 10 or so years rapping on a 9.x and a 6mm cord using the 6mm both as a pull line and as part of a simple double "rope" rappel. I inspect the cord before every trip out, and it gets replaced regularly. No problems, though I'm really careful about sharp edges.

I recently purchased a 100m spool of New England Ropes 6mm Prusik Cord and cut it down for tag line use. It it higher strength (10.3 kn) than most 6mm cord.
marty funkhouser · · Unknown Hometown · Joined Dec 2007 · Points: 20

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
This is how I use tag lines and it has served me well for hundreds of rappels

Edit: however I do rig the rappel so I pull on the fat rope and my tag is 7mm

iceman777 · · Colorado Springs · Joined Oct 2007 · Points: 60

Never had a problem with it yet

rgold · · Poughkeepsie, NY · Joined Feb 2008 · Points: 526
bearbreeder wrote: the biggest disadvantage is that you are entirely reliant on your partner to remember to set it up properly if they forget or screw it up ... or if your communication is poor on raps, a frequent occurrence, you die
Yup, better climb with folks who know their stuff if you're going to do this.

bearbreeder wrote: the other disadvantage is that you cant simply pull one strand through once your at the anchors ... youre going to have to pull the the entire thing down before rethreading
That's true for the usual way of rigging it too, so this is not a disadvantage relative to the conventional option.

bearbreeder wrote: using a ~8mm half rope as a tag line solves alot of these issues as it allows you to lead back up in an emergency ;)
Yes, but this is not exactly a lightweight (or low bulk) option.
bearbreeder · · Unknown Hometown · Joined Mar 2009 · Points: 3,065
rgold wrote: That's true for the usual way of rigging it too, so this is not a disadvantage relative to the conventional option.
if i have say a 8mm half and a 9.5mm main ... i simply put the pull side of the rope through the next anchors ... and once the last rapper is down pull it through the chains while the other climber pulls the rope down ...

its exceptionally fast this way, rather than having to pull the cord back up and thread the same side through all the time

especially with thin cord, that stuff gets tangled and caught easily if theres features/trees below

now the question came up about the 6mm cord .. personally i would use the biner block ... while i can see the benefits of having the rope down first before the cord ... remember that in a biner block scenario the thin cord is not loaded and thus less subject to abrasion and getting cut ... if you were to tie it off to the bottom anchors such a possibility merits serious consideration IMO especially if there are edges and features for the rap ... in addition to the communication issue, ie until the first climber is down you wont know if there are edges and features that can cut the loaded cord, and on long raps in windy conditions you many not be able to communicate that it may not be safe to set it up that way

as to the the OPs 7mm cord ..

remember that with you should be getting cord up to 5-10% longer to account for rope stretch

as an example

mammut 7mm cord - 33 g/m

mammut phoenix 8mm half - 42 g/m, 8% static elongation

so on a 70m 8mm rope ... thats 2940g

vs a 76m 7mm cord ... 2508g

or a 432 g difference ... less than 1 lb

for that weight difference the half ropes allows much more options than a cord

not to mention you can use it for glacier or moderate alpine routes/scrambles as well

;)
Optimistic · · New Paltz · Joined Aug 2007 · Points: 450
bearbreeder wrote: remember that in a biner block scenario the thin cord is not loaded
Would there be a problem with using the biner block on the cord rather than on the lead line?

EDIT: Oh I see what you are saying there now, that while the cord (esp the 7mm I'll be using, min. breaking strength 2700#) is strong enough by far to take the LOAD of rappelling, you still prefer the lead cord to be loaded, for abrasion resistance because of its larger diameter?
wivanoff · · Northeast, USA · Joined Mar 2012 · Points: 674
Optimistic wrote: Would there be a problem with using the biner block on the cord rather than on the lead line? EDIT: Oh I see what you are saying there now, that while the cord (esp the 7mm I'll be using, min. breaking strength 2700#) is strong enough by far to take the LOAD of rappelling, you still prefer the lead cord to be loaded, for abrasion resistance because of its larger diameter?
Yes. I see two bad scenarios here - unless I'm misunderstanding you. One is the the 7mm cord goes through the master point and is loaded with the biner block on the 7mm cord side and the connecting knot on the thick cord side. The other is the thick cord goes through the masterpoint and the biner block is tied in the thin cord and clipped to the thick cord. In that case, the connecting knot would have to pull through the master point before the biner block did anything. Neither seems good practice to me.

Best not to reinvent the wheel. Canyoneers do a lot of this type of rappeling. Probably more so that the average rock climber.
canyoneeringusa.com/techtip…
caves.org/section/vertical/…

And, BTW, re-reading my original reply sounds more snarky that I intended. Should have added a smiley. Sorry about that.
Optimistic · · New Paltz · Joined Aug 2007 · Points: 450
wivanoff wrote: Yes. I see two bad scenarios here - unless I'm misunderstanding you. One is the the 7mm cord goes through the master point and is loaded with the biner block on the 7mm cord side and the connecting knot on the thick cord side. The other is the thick cord goes through the masterpoint and the biner block is tied in the thin cord and clipped to the thick cord. In that case, the connecting knot would have to pull through the master point before the biner block did anything. Neither seems good practice to me. Best not to reinvent the wheel. Canyoneers do a lot of this type of rappeling. Probably more so that the average rock climber. canyoneeringusa.com/techtip… caves.org/section/vertical/… And, BTW, re-reading my original reply sounds more snarky that I intended. Should have added a smiley. Sorry about that.
No worries on snarky! I should've at least TRIED to search!

Could you elaborate on why you don't like rigging to pull the lead line? Seems like:
-have to do something to deal with the difference in stretch, which adds complexity (especially if the last person down forgets to free up whatever you rig to stop the thin cord from sliding)
-potential for increased abrasion on thin cord if it is taking the rap load
-something else?

I do see rgold's points about wanting to get the lead line back first and about the discomfort of pulling the thin line... Do people just rig a kleimheist or something if it's too painful to pull on the skinny line? Or does that not come up much in practice? I don't see the tag line fans complaining about that issue much here...
rgold · · Poughkeepsie, NY · Joined Feb 2008 · Points: 526
bearbreeder wrote:if i have say a 8mm half and a 9.5mm main ...
Of course the pulling order doesn't matter if you have two lead ropes, but that wasn't the question. We were speaking of either a 6 or 7mm tag line, and in that case, whether you use the method I described or the conventional one, you will have to wait until the rope is down before threading the next rappel, so the method I described has no pulling and threading disadvantage.

Since the method I described loads the tag line, it is only appropriate for experienced parties who know how and when to make the appropriate judgement calls. It isn't something you'd use every time---I said "...suggest considering two modifications at least some of the time" (now bolded to increase reading comprehension) for a reason!

As for not hearing much about difficulty pulling a thin tag line and/or having the rope hang after it has come free of the anchor, you can probably manage without problems most of the time. In a climbing career spanning 56 years, I have had a rappel hang after coming free of the anchors---and not be retrievable by pulling---just once. But if all we had was a tag line at that point, we would have been in some very deep doo-doo. So at the end of the day you have to decide which of the associated risks seems worse for the situation you're in.

My solution, by the way, is half ropes. I tried tag lines years ago and concluded they were an inferior option for me. I do get the tag line concept as an emergency backup when long raps are not anticipated, and for things like single-pitch access raps. I understand the big wall applications when the leader may need to pull stuff up during a lead. But for routes that are long, possibly remote, but mostly free, I think the tag line is not the best choice.
Guideline #1: Don't be a jerk.

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