UKC

is an overhand knot the best knot if I am using a 8.3 half as a tag line with my 9.8 single
thanks

In reply to GDS:

It matters not what knot you use so long as it's big enough to not pull through the maillion and doesn't come undone.

In reply to GDS:
Knots can and have pulled through rappel rings with, of course, fatal consequences. We had a tragic accident of this sort in Yosemite not too long ago; see the Supertopo thread at http://www.supertopo.com/climbers-forum/1164065/Climbing-Death-in-Yosemite-... .

In that thread is the following picture of ten common Yosemite anchor set-ups. The knot in a 9.2mm rope with a tagline will pull through seven of these. http://www.supertopo.com/climbing/thread.php?topic_id=1164065&msg=1171763#m... .

The method recommended by Petzl catalog and others is not the best, because even if the knot doesn't pull through the rings, it can jam there and make retrieval a major problem. The best system is pictured here; http://1.bp.blogspot.com/_D0ucNey_VU0/S_JAWXobEwI/AAAAAAAAAC4/uvZxnDXcJ4E/s... , the biner on a clove hitch does double-duty as both a blocking agent that won't jam in the rings and a backup that makes the rappel secure no matter where the knot ends up. I think I'd be more comfortable using a locking carabiner for this purpose however.

In reply to rgold:

Thanks for giving those Supertopo threads an airing.

In reply to rgold:

Better image: http://static-dev-climbing.s3.amazonaws.com/wp-content/uploads/2012/11/Long...

Instead of the butterfly I do a fig8 on bight with both the tag line and the end of the abseil line.

In reply to GDS:



As you said "tag line", the above posters have assumed you want to rap just one rope. Is this what you meant, or do you plan to rap as normal on both ropes?

In reply to GDS:

I have used a 5mm tag line a few times in Yosemite and Red rocks. It works quite well but it a bit of a faff.

However if I was climbing, as you are, on a single rope with a 8.3 half as a tag/rap/haul line I would tie the ropes together and rap as normal.

I normal use a single overhand to tie my ropes together but due to the difference in diameter in this situation I would probably tie the ropes together using a reef knot with half a double fishermans on either side. http://0.tqn.com/d/climbing/1/G/k/2/-/-/KnotsClimbing033_SquFishKnot_2.jpg

HTH

In reply to Tom Ripley Mountain Guide:


This isn't a criticism - I don't know enough about knots to criticise - but I believe a sheet bend might be a more secure knot there.

In reply to Tom Ripley Mountain Guide:

Why the need to tie the tagline to the other rope and not attach it to the krab, with a double fig-8 for example?

In reply to featuresforfeet:


Because you don't need to treat the 8.3mm rope as at a tag line you can abseil on it like normal perfectly safely, providing you tie the ropes together with an appropriate knot.

Hope this makes sense.

In reply to Tom Ripley Mountain Guide:

Sorry, I'm asking a slightly different question. Assuming the tagline is a tagline (say a 5mm cord) why wouldn't you just tie it to the krab?

In reply to featuresforfeet:


Ah, okay.

When I have used a tagline I have tied figure of eights on the bite into the ends of both tag line and the lead line. I then clipped both ropes together using a triple action screwgate. I then clipped the screw gate back into the the lead line so if would form a slip knot if the tag line got damaged. I abseiled as normal putting both the tag line and the lead line through my belay plate. This is to stop the lead line jamming against the anchor and becoming difficult to pull.

It is worth keeping the tag line in a stuff sack and throwing it down each abseil in one. As soon as it gets windy they get blown everywhere and are a bit of a nightmare.

In those circumstances it is probably best to lower the first climber (using a munter mule) and then the second climber abseils down on the lead rope and tag line. This is much slower than abseiling normally.

In reply to Removed User:

Part of my point was that this method is not better, because the knot can jam in the rings or chains, making the pulldown harder. In the picture I posted, the blocking is done by the carabiner rather than the knot.

In reply to rgold:
So in my pic you'd be abseiling on A and pulling on C rather than the other way around?

In reply to Removed User:


Eek No! Look at http://1.bp.blogspot.com/_D0ucNey_VU0/S_JAWXobEwI/AAAAAAAAAC4/uvZxnDXcJ4E/s... , but as I said substitute a locking carabiner. The strand on the right is the rappel strand. What blocks that strand is the carabiner (and clove hitch) bearing up against the rings, and the point is that this is much less likely to jam in the rings then any of the bigger knots suggested by the other posters. US canyoneers call this a "biner block."

David is of course right that with the rope diameters originally mentioned, the OP could rappel on both lines rather than rappelling on just the single fatter rope and using the thinner rope as a tag line, but other posters are speaking about thinner pull cords that are definitely tag lines, and I (mis)interpreted the question as a tag line rappel question.

In reply to Tom Ripley Mountain Guide:



The approach shown in http://people.bath.ac.uk/dac33/high/10GettingBackDown_files/image074.png

is I think better. As others have pointed out this is because placing the krab above the knot linking the two ropes stops the knot getting stuck in the maillon or passing over the top of the sling.

chapter 10 in www.multipitchclimbing.com shows a host of pictures on the topic.

In reply to GDS:

Don't really understand why you would use a tag line, couple of skinny ropes would weigh about the same and i think have more utility - am i missing something

In reply to Removed User:

no ! in your pic the alpine butterfly would be replaced with a clove hitch on the krab,
it stops the knot (AB) going through (partly) the links on your chain. If say 1/2 of your AB got pulled through the links (ab ring) when descending it would be hard to pull it back via the tag line, the clove hitch on krab would stop that

(as i understand it from reading the post and pix and what rgold has said)

In reply to John Kelly:

I think the US is the only place where tag lines are popular. I don't think there are, objectively, much in the way of good reasons except in the context of big wall climbing, and there are some pretty obvious drawbacks. US climbers seem to me to be far more dedicated to their single ropes than other nationalities, and far less likely to own or even consider half or twin ropes. If all you own and use is a single rope, then a tag line is a relatively inexpensive way of extending your rappelling range.

In reply to John Kelly:


Examples:
1. team using a single rope because they want to climb faster, or simul-climbing through a microtaxion, or belaying with a grigri, or short fixing
2. they like climbing on a single and the route has one 60m rap off the back of the hill
3. someone rope soloing

In reply to rgold:

get the US thing, suppose endless cracks are easier with a single

In reply to David Coley:

all good reasons which I overlooked (but i like 2X1/2)

In reply to David Coley:

Yes, although I'd add that if the climb requires a significant amount of rappelling, then "climbing faster" on the way up may be balanced or even seriously negated by "descending slower" on the way down if a tag line is used. In any case, the majority of climbers in the US who I have encountered using tag lines are mostly in a category analogous to #2. I think the recent trend is to use the thinnest available half rope as the second rope rather than some 5.5mm tangling nightmare you can't lead on if your rappel hangs.

In reply to rgold:


That's what I did/saw when over there, but then it made even less sense to me over using half/double ropes than the 5mm tag line. I was carrying more weight (a single and a half) but wasn't using the half rope to ease any rope drag.

It also meant that there was another task when I got to the belay - hauling up an unused rope and stacking it really carefully so it runs free on the next pitch. And then there's the possibility it's going to snag when you pull it up so your second has to make a detour to retrieve it.

If I was making my own choice I'd take two half/double ropes or a long single rope and a 5mm tag line in a stuff sack.

In reply to rgold:

First choice would be a pair of ropes of one sort or the other.

In reply to GDS:

I think with an 8.3 you'd just tie the two together and ab normally, assuming you're not using a GriGri or similar.

A question for those who've used the Reepschnur method ie assuming you have a single and 5 or 6mm tagline - where do you put the back up?? Clove hitch the biner (I understand the argument against using the AB on the single) to the single as per above http://1.bp.blogspot.com/_D0ucNey_VU0/S_JAWXobEwI/AAAAAAAAAC4/uvZxnDXcJ4E/s... or fig8/AB the biner to the tag line http://www.rockandice.com/lates-news/reepschnur-review ?? Or does it not matter??

In reply to kyaizawa:



I've always assumed
http://1.bp.blogspot.com/_D0ucNey_VU0/S_JAWXobEwI/AAAAAAAAAC4/uvZxnDXcJ4E/s...

(but with a locker not a snap gate) to be best as the knot can't get stuck in the maillon or sling.