Full length rappels with Accessory Cord and Single Ropes

Doubles and Twins are nice and all that, but for curiosities sake is there any significant risk factor involved in rappelling off a single rope joined to 7-8mm accessory cord in the same fashion that one would perform a full length rap using doubles? 

If the rappel is largely static what would make this a poor choice for full length rappels? You can build anchors with sufficient diameter accessory cord, so it shouldn't be a problem to lower a static load off accessory cord? 

Any comments would be appreciated 

The danger would be if your rope got stuck (when pulling it) and you had to lead on the 7 mil cord to free the snag.

I have a  6mm mamut rappelling line.  Use  it mostly for soloing  but  wouldn't hesitate to use it for a tag with a single.  

Dirt Kingwrote:

Doubles and Twins are nice and all that, but for curiosities sake is there any significant risk factor involved in rappelling off a single rope joined to 7-8mm accessory cord in the same fashion that one would perform a full length rap using doubles? 

If the rappel is largely static what would make this a poor choice for full length rappels? You can build anchors with sufficient diameter accessory cord, so it shouldn't be a problem to lower a static load off accessory cord? 

Any comments would be appreciated 

Why do that?

Normally, people combine an even thinner accessory cord, and use it as a pull cord: rap on a single strand of your climbing rope, then use the accessory cord to pull that rope through your anchors and down.

That saves weight,  but more importantly, rapping on two ropes of different thickness, static/vs stretchy, etc. is likely to cause problems, with uneven amounts of each rope moving through your rappel device.

I have also gone round and round on this and if it is a "better" system overall. It seems the benefits are simplicity and weight savings; but with a quick look around at the lightest options for both systems, the weight savings is not that great.
I imagine there are lighter total system weights out there, but this was just from a quick Weigh My Rack search:

2.75lbs. for a 60m Beal Back Up Line (5mm diameter)
6.34lbs. 8.5MM OPERA UNICORE 60M 2XDRY
= 9.09lbs. for both lines 

4.76lbs. for a 7.1mm 60m Edelrid Skimmer Half Rope
= 9.52lbs. for both lines

That is only about a 7 oz. weight savings. Not too impressive. Sure, you get to climb on one line which is easier to manage for clipping gear and sorting out at a belay and rap station, but I think I would carry the extra weight and have the security of two legit half ropes to work with vs. a 5mm tag line and lightweight single rope system, especially with any risk of a stuck rope or damaged rope from ice/rockfall, etc. Just my two cents. 

The 6mm Esprit Alpine Escape rope is a way better option than 7mm accessory cord.  It has been used by alpine climbers for the past 15 years and is pretty much the standard down in Patagonia for a second rope.  It is stiff and coarse enough that you can use it without any special tricks when paired with a normal single rope.  I usually set it up so you pull the full size rope.

https://www.outdoorgearlab.com/reviews/climbing/climbing-rope/esprit-alpine-personal-escape-rope

Maxim ropes made a direct copy of the Esprit.  Edelrid is also making a similar rope that is a bit softer which I haven't had a chance to test yet.

Mikey Schaeferwrote:

The 6mm Esprit Alpine Escape rope is a way better option than 7mm accessory cord.  It has been used by alpine climbers for the past 15 years and is pretty much the standard down in Patagonia for a second rope.  It is stiff and coarse enough that you can use it without any special tricks when paired with a normal single rope.  I usually set it up so you pull the full size rope.

https://www.outdoorgearlab.com/reviews/climbing/climbing-rope/esprit-alpine-personal-escape-rope

Maxim ropes made a direct copy of the Esprit.  Edelrid is also making a similar rope that is a bit softer which I haven't had a chance to test yet.

Good info, Mikey, thanks for the tip.
Question for you -- is there any worry about using that line if you are climbing as a party of three, bringing up a climber on the 6mm line? What would be your vote as the primary single rope? 

If you rap with a tagline off a v thread, it is probably a good idea to keep the tag a few meters longer than your rope, so use a 65m tag for a 60 meter single rope. Euro death knot with a good tag with your single rope touching the anchor and the knot offset to the side of the tag line is the way I learned. It is probably cheaper to buy a rappelling tag line than accessory cord by the foot but there is nothing wrong with it, 6-8mm accessory cord is used for cordelettes and other life preserving aspects of climbing. most canyoneering ropes are between 6 and 9 mm static line, so i dont think you would get any funny looks for using life bearing accessory cord as a tagline on a rap.

Normal nylon accessory cord sucks in comparison to the purpose made rap cords, but the real decider is that 60 m of accessory cord costs about the same as a 60 m rap cord. Don't waste your money on the accessory cord option thinking that you're saving $20 (I speak from experience).

I have the Edelrid cord referenced by Mikey, and it is great. It's awesome to have a 6 mm cord which is completely compatible with normal belay devices and rope grabs. Accessory cord is made to be very supple, to tie knots. Rap lines are stiff to increase the effective friction through a rap device. For reference, I can easily rap on two strands of Edelrid cord with an ATC and single locker, no prusik. If you try that with 6 mm nylon accessory cord, you probably can't control a free hanging rap. (I understand this isn't the system the OP is using, just an example.)

Tim Hwrote:

Good info, Mikey, thanks for the tip.
Question for you -- is there any worry about using that line if you are climbing as a party of three, bringing up a climber on the 6mm line? What would be your vote as the primary single rope? 

I don’t believe the Esprit rope is certified as a single line rope to be used in that manner.  It would have to be super easy terrain with no chance of abrasion or cutting for me to be comfortable using it like that.  Using it on a really easy snow climb or glacier travel is a scenario I could see doing it.  But for rock there is no way.  I’ve rapped on it as a single like more times that I care to admit and it always feels a bit exciting to do so and not something I’d encourage people to do.

I use whatever the mamut  version of the 6mm  rappelling specific  cord is.  

supposing a lead rope of 70 m, what would the ideal length be for the Esprit or similar

I may be opening up a can of worms here, if so apologies in advance.  

It seems that the general consensus here is that if using a skinny pull cord, to rappel on both strands.  I think that's a good call, assuming a) the rap is clean, with no sharp edges and/or b) the skinny cord is designed with a abrasion in mind.  If I were using a skinny second for rapping in this manner, I would strongly consider something with an aramid component to reduce the risk of sawing through the skinny on an edge.  Regular 5mm or 6mm nylon is much more susceptible to failure through abrasion, which would be catastrophic in this setup.

For whatever reason, it seems to have become really popular lately to use the reepschnur to rap a single line with a skinny retrieval line, or even when the retrieval line isn't that skinny. I would caution folks against doing this, especially in situations where the anchor setup can induce any twisting.  There were two rescues in RMNP this past summer of teams using the reepschnur and ending up with ropes hopelessly twisted together and virtually impossible to retrieve (without ascending, which for different reasons didn't work out for those parties).

My inclination is towards proper half/twins when appropriate, or using a single rope and aramid-sheathed-or-cored skinny line to do standard double rope rappels.

Tjaard Breeuwerwrote:

...but more importantly, rapping on two ropes of different thickness, static/vs stretchy, etc. is likely to cause problems, with uneven amounts of each rope moving through your rappel device.

I think this is a myth.  Ok, yes it is possible for different sized ropes to move through the device at different speeds, but in practice it is incredibly easy to mitigate this risk.  Just paying attention to the speed of each rope through the device works.  Using an autoblock does as well.  If you keep the ends tied to you, even if they slip it is a non-issue.  Or preload both climbers on rappel, then have the first one down provide a fireman's belay so the ends can't shift.

Tim Hwrote:

Good info, Mikey, thanks for the tip.
Question for you -- is there any worry about using that line if you are climbing as a party of three, bringing up a climber on the 6mm line? What would be your vote as the primary single rope? 

F#CK YES THERE IS

Thank you all, pretty much answered my question  it appears that the consensus is that it is possible, if not entirely recommended. Once I have the money to upgrade to a double rope system I'll probably go that route, but in the meant time I may see if I can get by with some 7mm cord and a single rope for pure ice rappels with no chance of rocks abrasion. If money weren't my primary setback I'm not sure there would be significant advantages to this system as the smallest twin ropes are about 7-8mm and probably a helluva lot more abrasion resistant than regular old nylon accessory cord. 

I have caught a seconding fall on a 6mm rap line on rock. It worked ...  was not my idea but it worked. 

Dirt Kingwrote:

but in the meant time I may see if I can get by with some 7mm cord and a single rope for pure ice rappels with no chance of rocks abrasion. If money weren't my primary setback I'm not sure there would be significant advantages to this system 

Zac, I think you're probably fine doing this with the precautions you mentioned, buy long term if might be a false economy.  

Halfs are nice and deserve a place on the gear wall, but I prefer a single most of the time for various reasons.

Ballpark $100 for 70m of 7mm cord, versus $290 for the Edelrid 6mm aramid/nylon rap line.  

You're saving $190 in the short run but buying a rope with extremely limited use.  I like my tools to be multipurpose in the mountains; what if the rap route for your ice climb is on rock off to the side?  

I don't think YGD with 7mm nylon, but if you can save your pennies and buy a lighter, smaller, more abrasion resistant aramid blend rapline I think you will not regret it.

Matt Nwrote:

F#CK YES THERE IS

Looking at it from a pure ice climbing situation only; just curious if that is even an option or is just inviting trouble and not worth the weight savings and/or rope mgmt.
Do you have real world experience with these lines, all caps Matt? Examples of where these perform best from your view? Ice? Alpine? Glacier? 

Also, a Beal Opera 8.5 70m plus Edelrid rapline is 350g lighter than a pair of Sterling Photon 7.8 halfs.  

Some folks will make the argument that you can belay two seconds on the halfs.  True.  But honestly I've taken mostly to using skinny single rated ropes if climbing anything hard in a team of three, and accept the weight penalty.  Two Beal Operas feels way better to me in a team of three.

Philip Magistrowrote:

Ballpark $100 for 70m of 7mm cord, versus $290 for the Edelrid 6mm aramid/nylon rap line.  

You're saving $190 in the short run but buying a rope with extremely limited use.  I like my tools to be multipurpose in the mountains; what if the rap route for your ice climb is on rock off to the side?  

I think for most use cases the aramid rap line probably isn’t worth the money.  You can get the esprit or maxim from anywhere between $100 to $150 and they hold up extremely well and are comparably priced to 7mm accessory cord.  Having owned numerous esprit lines I’m confident in saying they are more than adequate for 99% of climbers and uses out there.  The only time I’d probably want something more burly is while hauling multi day alpine packs on sharp rock.  That has a tendency to trash small ropes.  But for use as a rappel rope the non aramid ropes are just fine on any terrain.