I'm about to buy a 70 meter rope and I want to reduce the number of raps necessary to get back to ground level so I'm thinking of buying a thin pull rope to carry up and then use just for rapping.
First, what diameter cord should I use?
Second, will the considerable difference in diameters of the climbing rope and pull cord present serious problems as they pass through the rap device, or is this easy to deal with?
~ beau

PS: I've just found this very intersting discussion on supertopo.com http://www.supertopo.com/climbing/thread.php?topic_id=836473

Are you trying to get a consensus from all the forums? BTW, a lot of people post in all three places, RG for example. Better listen to what RG says, it's good stuff. Though I think he'll probably tell you to walk off as it's faster than rapping.

I don't know anyone that uses a tag line at the Gunks. Some friends use doubles. Some make two raps. Some walk off. Some wait until there's another party then join ropes.

Edited to add:
Here's a post by RG regarding tag lines and doubles.
RG post from the other web site.

To reduce the number of raps necessary, you should walk off...
Nobody uses taglines at the Gunks. People only use them when you can't get down easily with a single rope.
That usually happens when the anchors are full rope lengths apart due to a lack of intermediate ledges.
At the Gunks, there are lots of ledges and trees and bushes to get stuff caught in. So you have not only intermediate rap stations (plus walk offs), but it's actually often easier to do single-rope rappels.

As a slight thread derailment to trivia, who can name a climb at the Gunks where you actually need more than a 60m rope to get off the top of the climb (without upping the climb grade to get off or leaving a new anchor beyond those traditionally found)?

Hey, thanks for the plug, QTM. A bit more on the subject in this SuperTopo thread.

I think tag lines make very little sense, but there are a lot of very experienced climbers who use them, so maybe its me who is off base. A few years ago, Steve Molis and I hung a rappel in Red Rocks which would have left us totally stranded if we had used a tag line. The account (along with many other things) is in the following Red Rock TR also on SuperTopo.

As you mention in the referenced report, "In this case, had we used a single with a tag line and, as is most common, pulled the tag line and therefore hung the single, we would have really been up the creek.", a common mistake. When using a rap retrieval line (a tag line is really somewhat different), always rig it to pull on the main lead rope. The retrieval line is sacrificial if necessary.

Back to the OP...my retrieval line is an 8mm static, 'cause I got it at a good price. I'd consider a 7mm, but no thinner as those just tend to always get into a tangled clusterfluck.

Rigging to pull the main rope is indeed a good idea from the point of view of retrieval, but a perusal of both written and electronic material suggests that this is not the usual recommendation, which accounts for the proviso, "...as is common..." in the remark quoted by Marc. One reason for this is that the potential for the thin rope running through the anchor during the rappel, leading to uneven ends and even complete failure of the rappel, is much higher if the rappel is rigged so that the fat rope is pulled.

This effect comes from both the differential stretching of the different diameters (this perhaps alleviated by having the small diameter a static line) and the fact the the fatter line runs through the rap device with more friction than the thinner line. Typically, something extra is done to prevent rope motion at the anchor for all but the last person down, who has to be extra careful and who can also be protected by having those below control any rope slippage.

Beau, I'm a little confused by your premise. I know a bunch of people who buy a 70 so they can combine rappels (for instance, you can rap Birdland in Red Rock with a single 70) with only one rope. In that case, they buy the 70 so they don't have to carry two ropes. So you're looking to buy a 70 *and* a tag line?

I prefer (60m) doubles for just about anything, but iff'n I was going to bring a tag line, I don't think I'd go far below 8. Maybe 7.8. I tend to get nauseous at the thought of rapping on a 7. But that's just me.

Like RG said, big differences in diameter slip and stretch at different rates. I believe there have been rap-off-the-end accidents due to this - so be sure to either tie a knot in the end of the tag line, or watch it very carefully.

Tradjunkie, can you be a bit more specific in your trivia statement: in one rappel, or multiple? I can say that when S & I went about rescuing someone's stranded girlfriend off of Shockley's many years back (in the dark of course), I found out the hard way that a pair of 60s do not reach the ground.

Agreed. Another reason (which I should have mentioned) why my retrieval line is an 8mm instead of something thinner.

OK Julie,
Excluding rescues and other such misadventures, what climbs at the Gunks can you not return to the base of the cliffs if your equipment consists of a single 60 meter rope and you are leading at your limit and you have no leaver gear beyond maintaining existing in-situ anchors?
A 5.6 leader who does Shockley's with a single 60 meter rope will normally climb to the top of the cliff. From there it is easy to walk off (or rap down 3 Pines or Arch with a single 60 meter rope).

Birdland or Levitation 29 at Red Rock are good examples where, with a single 60 meter rope, you can't get back down. My question is, which climbs at the Gunks will similarly leave you stranded? (3 Doves/Limelight does not qualify as stranded even though a 60m rope won't get you to the GT ledge tree.)

If you go to the top you can always walk off or walk to a bolted station, so I'm not sure I understand the trivia question. I must not get it.

Bonnie's requires a double rope rap from the top, since it's all air once you start the rap.

No Glow has no station between the GT Ledge and the ground.

Double Crack is a double rope rap unless you care to rap off that tat on the moving chockstone.

SethG,
The trivia question was related to my point about needing a tagline, which you're catching onto in your confusion.

Of the 1,300 or so climbs listed in guidebooks across the various crags at the Gunks, when is a 60 meter rope NOT ENOUGH such that you need a tagline or more rope?

The tricky part of this trivia question is that such situations are exceedingly rare.

I think Double Crack may be one, unless you're desperate enough to use the chockstone, though I've never tried to climb up to the top of the cliff from the top of the route. I wonder if anyone here has.

No Glow takes you to the top, unless you're just doing the first pitch, which makes no sense. And the GT ledge is huge there anyway, so just walk along to a different rap station.

Any bolted rap line will get you down the cliff with a single 60. if you start using fixed tat to get down, you will eventually get hosed. Either walk off completely, or know where the bolted rap lines are. They are spaced out fairly evenly along the cliff. This beats carrying a 70m rope and a tage line hands down.

I cannot think of any good reason to drag a tag line at the Gunks. If you use the bolted rap lines the most raps you will do is 3 which is not that time consuming. If you want to use two 70m ropes to rap down wherever you want it is really not a good idea -- loose rocks, erosion, not good for the trees etc. etc..

In Red Rocks, you are better off using double ropes in case the ropes get stuck. I know of guides who use tag line because they have to carry most of the load and most of their clients do not know how to belay with doubles.

But again, if you're doing 3 raps, you'll usually be able to walk down faster.