Multi-pitch rap sequence with single rope + tag line

Andy Wiesner wrote:

Ha! What kind of biner? I just carry the little ones anymore. 

I always had my wires on old-style ovals:  RPs, small stoppers and large stoppers.  That makes three.  I have big hands and those were easier to handle when placing a stopper.   And I usually had a couple other ovals or D's floating around on the rack.  You only need 4 plus your locker, 5 if you're rapping on a single, twins (7.5mm) or have a heavy pack.  

https://m.youtube.com/watch?v=9_sGyjr8IKo

Here’s some break tests with tag line combo rap

That's a cool video.  It's neat being able to see the knots invert live and to see the numbers associated with it.  The bit about never placing the skinny rope in the maillon is very simplistic and likely dumbed down for the general public.  As I said upthread, I've done that a lot (as have others) and have never had a problem that I couldn't easily fix.  When it comes to 'nevers' in rappelling, I can think of much more important ones than this.  Also, at the end of the video, he's rapping off of a single flat overhand stopped in a maillon without any sort of backup if the knot were to pass through.  That seems way sketchier to me than rappelling on both strands simultaneously with the skinny end fed through the mallion and managing the travel potential as you go.

Lots of shenanigans going on here regarding rapping ropes of different size.  Rope creep is real and should be addressed.

Simply

Set up rappel device normally, then add a second biner to the thin rope in your device the same way you would to rappel a single rope.  This will balance out the friction quite a bit.  Then, while first is descending, second monitors for rope creep.  He/she can simply grab both ropes with bare hands to add more friction, if needed.  

When second raps, first hold both strands (as one should always to give a fireman's), then he/she can put a small amount of tension in thin rope as needed.

Quick and efficient.   Keep it simple.

Max Tepfer wrote:

That seems way sketchier to me than rappelling on both strands simultaneously with the skinny end fed through the mallion and managing the travel potential as you go.

I thought so too. May work in a lab (2:50 of the video) but in real life, for me, no way.

Greg D wrote:

Set up rappel device normally, then add a second biner to the thin rope in your device the same way you would to rappel a single rope. 

Greg, Do you mean like in the below in cross section?  It is crudely drawn, I know. 

I'm assuming this is part of an ATC rig without actually showing the ATC itself below.

LEGEND

black - cross section of biners in, say, plain ATC (though hopefully not hollow  biners!)

purple - fat single rope

red - skinny tag line

Bill Lawry wrote:

Greg, Do you mean like in the below in cross section?  It is crudely drawn, I know. 

I'm assuming this is part of an ATC rig without actually showing the ATC itself below.

LEGEND

black - cross section of biners in, say, plain ATC (though hopefully not hollow  biners!)

purple - fat single rope

red - skinny tag line

Hey Bill. That may be correct. But I’ll post a photo later. 

Brings back memories of things I tried to add friction to the tag line. Never tried a second biner biner for just one or just the other line.  But I did find other ways to do it.

But adding friction to a really skinny tag line adds to how my much we are trusting our lives to it, I feel.  I mean, we do it to stop the knot from moving which I agree is a killer concern. But by stopping knot movement that way is safe only if the skinny cord does not break under the resulting higher forces or related edge abrasion  

Now, we can all pull out strength ratings of our favorite skinny cords and argue we are ok (except for maybe the edge thing).  I kind of did for a short while. But I personally decided to not rely on adding friction to the skinny cord and found other ways to stop the knot movement. 

After doing a couple laps on a route today, I spent some time working on this subject, and doing some unscientific experiments.

General notes:

• Climbing rope is a Bluewater Xenon 9.2 Double Dry. Used probably 10-15 times. Purchased last year.
• Tag Line is a brand new Black Diamond 6.0 static line. This was its first use. Package says 10kN breaking strength.
• Ropes were joined with a single flat overhand with around 12"-14" of tail. I rappelled 5 or 6 times on the same flat overhand. Inspected before and during weighting each time.
• Rappel device is the new style Reverso with a Metolius Element as the friction-bearing carabiner.
• When an additional carabiner was added to the tag line, it was a Mad Rock SuperTech Screw Gate
• When a "second" was pre-rigged, it was with the 2018 version of the ATC guide and a BD RockLock screwgate.
• Rappels extended with a nylon sling, knotted half way.
• Friction hitch backup is a 4-wrap autoblock with the new version of Sterling's Hollowblock, well used.
• I rappelled with gloves every time.
• Rappel was about 100'. The anchor was built with a static rope and extended so the masterpoint was over the edge on a vertical/slightly overhanging route. Rope was free hanging when I wasn't rappelling, but my feet were against the rock when rappelling.
• All tests conducted with the tag line passed through the masterpoint, as shown in the pictures. Masterpoint was two Petzl Attaches.
• Each picture that you see is a recreation of what I did at the top of the cliff (I didn't want to drop my phone from up there), with the exception of the flat overhand pictures. Those pictures are of the actual knot after rappelling 5 or 6 times on it.

First test was with a "second" pre-rigged onto both strands:

Second test was without any additional friction measures (other than my autoblock), or a pre-rigged "second".

• The first time I didn't rappel any differently from how I would perform any other double-strand rappel. This means no special attention to the skinny line. This resulted in about 4'-6' of knot creep. It is very obvious when the knot is creeping. There is no way that you wouldn't notice it happening.
• The second time I tried to focus on letting the autoblock catch, and hopefully do something to prevent the knot creep. This resulted in about 3' of knot creep. Again, it was obvious when the skinny line was zipping through the device.
• The third time I focused on pinching the two strands together with the hand that was simultaneously defeating my autoblock. This worked very well, but required constant diligence to pinch the two stands together. By the end of the rappel, the knot had crept about a foot.

The third test was with an additional carabiner added to the skinny line at the rappel device to add friction.

This worked perfectly. It resulted in zero knot creep, and felt very controlled with just the right amount of friction. I rappelled as normal without doing anything else special and it worked great. I'm not sure why I chose to orient the additional carabiner that way, but I did. The test was conducted with the carabiner in the same orientation as the picture above. This method is likely how I will proceed in the future if I have a partner that doesn't want to pre-rig at the top or give me a fireman's belay at the next rappel station.

This worked perfectly. It resulted in zero knot creep,

Bill.  I'm going to borrow this photo. Thanks Demetri.  I have done it this way.  It does provide some added friction.  But, this is not what I was describing.  It does provide additional friction, but not nearly enough friction in the configurations that I have used.  Regarding the photo, clipping the "top black biner" to the belay loop as well as the other rappel biner is what I was describing, which adds more friction than what the photo depicts. 

Bruno, ideas, let’s chat!