How thin of a rope can a guy safely rap off??

[Woodcutter]

This is more of a cascadeskiiers question.

I am thinking about the up-coming ski season, and some of the things I have in mind have some cliffs to get down.

Anyway...I'm sure I read a Dan Helmstader report where he was rapping off Shuksan on 3mm line (or maybe that was the pull-cord). I know guys who rap off 6mm line, but that's still 3lbs for a 60m line.

If 5mm is OK for v threads, could you rap on it., etc, etc, etc,.

any thoughts gladly received.

...yeah, should really go climbing & get off the internet.

Jake

[DPS]

5.5 mm Maxim Tech cord would be plenty strong and pretty light.

[genepires]

one concern is having enough friction with the small diameter rope.

 

other is resistance to cutting on edges. thin ropes have less resistance.

 

you could use very very skinny ropes but have to be prepared for both of these concerns.

[CaleHoopes]

How about bring a 30m 8mm that works with a single device (like a reverso) and then bring a tag line to pull the rope (30m of 5mm?). Then rap off the larger line and pull on the other. Gives you a limit of a 30m rap but reduces weight greatly.

 

So, seriously: http://www.justropes.com/store/p/278-MAXIM-Unity-Climbing-Rope-8mm-x-30m.aspx

 

And then just add some Perlon for the tagline - or even the Mammut Pro Cord or Maxim Tech Cord like suggested.

 

So, that would at least get you down to 3.15 lbs for the rap rope and then around 1 lb for 5mil cord (30 meters @ 19.4 g/m)

 

Then of course, you need a device that fits: http://www.petzl.com/us/outdoor/belay-devices/reverso-3 - That device goes down to 7.5mm (rated)

 

That system could work great. I get the lighter, but I think gene's comments are valid - do consider how much risk you want to buy off on.

[Coldfinger]

Some seriously good advice:

 

Stop gram counting and do the following: Close your eyes and picture yourself hurtling through the air, hitting the mountain repeatedly (breaking bones) and finally hitting the talus or ending up deep in a bergschrund where you expire slowly over several hours.

 

MAKE SURE YOU ARE RAPPING ON A CLIMBING ROPE!!!!!

 

If you want really light, either get a 30m section of Beal randonee rope and pair it with 5mm pullcord or just get a 60m twin rope. The difference being in how much rapping you will be doing. The pull cords are light but are a real pain in the ass for a lot of rapping as they tangle unmercifully and are not a lot of fun to climb if you get a stuck cord.

 

One 60m rope will get you plenty of distance and very less risk of getting stuck as there is no knot. You can even lead 30m pitches or bring it along with a single rope for full length rappels in summer rock climbing.

Edited July 24, 2013 by Coldfinger

[chris]

I sort-of agree with Coldfinger, minus the hyperbole. I just think the weight difference between the smaller diameter cords is so negligible that its dismissable, and I find twin lines to be more useful in more applications, but at 8mm or less (a new one just came out that's <7mm), they pack smaller, weigh less than my single ropes, and allow me to travel more freely.

 

I mean, I know in theory I can rappel on 5mm cord, but in practice its a snarly pain in the ass, and I would be nervous about rappelling on 5mm over sharp edges though.

 

I have a quiver of ski-mountaineering / glacier travel ropes (all twin certified), in 30, 40, and 60m lengths, which I think addresses almost any combination of team size and rappel length. The 30m Beal Rando (8mm) weighs in just under 2.5 lbs (1110 gm). My 40 and 60m lengths are Beal Ice Twins (7.7mm, one of my 60's had to get the chop). The weight difference to go any smaller is so negligible - and a smaller belay device like a Reversino almost mandatory, so I'm satisfied with that.

 

EDIT: So you inspired me to go nosing around Sterling Ropes website, which has a full range of cords that might address your question. In theory, it looks like you could rappel on something as small as 4mm, which has a failure strength of +1,000 lbs (4.7kN). At 3mm, the cord strength sharply drops off to less than 472 lbs, or 2.1kNs. Sterling does make a pretty nice 6mm cord intended for rappelling, rated to 14kN, but cautions that you need special training for rappelling on such a thin line. I think this answers your direct question - but I certainly don't recommend it!

Edited July 24, 2013 by chris

[Coldfinger]

EDIT: So you inspired me to go nosing around Sterling Ropes website, which has a full range of cords that might address your question. In theory, it looks like you could rappel on something as small as 4mm, which has a failure strength of +1,000 lbs (4.7kN). At 3mm, the cord strength sharply drops off to less than 472 lbs, or 2.1kNs. Sterling does make a pretty nice 6mm cord intended for rappelling, rated to 14kN, but cautions that you need special training for rappelling on such a thin line.

 

DO KEEP IN MIND THAT ACCESSORY CORD LOSES UP TO HALF ITS STRENGTH WHEN WET. :: :: :: :: :: :: :: :: :: :: :: :: :: ::

 

Seriously, the stuff is made for pull cord duty only, NOT TRUSTING YOUR LIFE TO!

Edited July 24, 2013 by Coldfinger

[G-spotter]

Regular belay devices don't work worth shit on skinny cord.

Even the Reversino isn't much good on 5mm.

[Coldfinger]

Regular belay devices don't work worth shit on skinny cord.

Even the Reversino isn't much good on 5mm.

 

Yeah, birthday boy ( ) is right, jerky or out of control rapping=shock loading & sawing, who's idea is this anyway?

Edited July 24, 2013 by Coldfinger

[montypiton]

if you go with anything skinnier than about 7mm, for adequate friction the O-P SBG, rigged in the maximum friction mode will work, and it's inexpensive at just over half the price of the BD-guide. if you happen to have an old figure-eight around, you can wrap the rope through it twice, and have more friction than you'll ever need. you could rap on a munter, or even use the old carabiner wrap technique (very old school)using however many wraps it takes to yield a comfortable rate of descent. or if you're utterly fanatical about the weight, leave the harness behind and dulfersitz it. with ski-clothes, the burn might not be so bad. if you opt for the dulfer, saving the weight of harness + rappel device offers the option of upsizing your rope...

[Blake]

If you are going to rappel a 9mm and a 5mm rope together, which belay device do you all think is best?

 

Is it so different in terms of friction that none will handle it?

[ColinB]

With a 5 mm rope, I've just used it as a tag line instead of rapping on it. Way more secure feeling. What situation would you need to rap on both ropes?

[Blake]

When you don't want to pull your 5mm and potentially get your knot stuck, leaving you with x meters of static 5mm cord and no rope.

[CaleHoopes]

Honestly, even with the hyperbole, it sounds like we have consensus. Get a light 30m climbing rope that can fit through a device and then attach a tag line that you DONT rap on. You will rap on the single climbing rope and then at the bottom pull your rope down on the tag line. This is a very common practice AFAIK. Something like a 8mm rope should work fine in a reverso - they are rated only to support 7.5mm ropes and larger. So, using a reverso with a 5mm would be a bad idea. I agree with Coldfinger. Don't trust your safety to cord. Also, don't forget to attach your tagline with a good knot that will work between different diameters (like a double fishermans, not an EDK).

[Woodcutter]

That's all great stuff. Thanks everyone.

I regularly use the 7.8mm metolius ropes & they rap just fine in a reverso (granted, as a pair, not singly).

 

I find it really disturbing that the static lines loose up to 1/2 their strength when wet. I mean it's wet a lot outside innit!

 

Thanks again. I reckon it's worth noting that this setup is for ski touring, so the rope is really only for rapping, not climbing. The rope often never gets used. Also the raps are often not highly exposed: there is often a snowfield below the gully/ cliff that you've elected to rap, so whilst failure is not desirable, it may not be game-over. But please note that I don't want to trivialise the seriousness of rapelling.

 

My last question is: if you're using the single rope & thin tag line combo: what folks run the rope through on the anchor (carabiner/ rap ring?) to ENSURE the knot doesn't pull through. And is it just a knot, or is there some metal hardware on the pull-cord side which definitely wont go through the biner/ rap-ring anchor.

Thanks again. Jake

[Coldfinger]

My advice is just bring half your twin set and be done with it!

 

If you are skiing sanely, you will be carrying full avy gear anyway and a partner or two and splitting up rap gear even if you need 60 m of rope will take care of weight.

 

If your party is only doing a few short raps just bring one diaper style harness (eg BD Couloir), one locker & belay device and one twin rope if weight is THAT much of a big deal.

[Bronco]

Thanks again. I reckon it's worth noting that this setup is for ski touring, so the rope is really only for rapping, not climbing. The rope often never gets used. Also the raps are often not highly exposed: there is often a snowfield below the gully/ cliff that you've elected to rap, so whilst failure is not desirable, it may not be game-over. But please note that I don't want to trivialise the seriousness of rapelling.

 

My last question is: if you're using the single rope & thin tag line combo: what folks run the rope through on the anchor (carabiner/ rap ring?) to ENSURE the knot doesn't pull through. And is it just a knot, or is there some metal hardware on the pull-cord side which definitely wont go through the biner/ rap-ring anchor.

Thanks again. Jake

 

Jake - this system isn't great for low angle raps (as you may encounter more frequently ski mountaineering) as it has a propensity to hang up on everything.

 

However, here's some more info on how to rig it with a biner to prevent the knot pulling through the anchor: http://www.supertopo.com/climbing/thread.php?topic_id=1176066&tn=0

[NateF]

You can rap on 6mm static line with a munter hitch.

Not all static line is created equal. Some is designed and marketed for the sort of use you intend, some is designed as "accessory cord", which I think is the type which loses strength when wet. I don't think you'll find something <6mm that has much strength or durability margin but who knows, there is some strong stuff out there.

[kurthicks]

As a lot of folks mentioned, I'd recommend a twin rated rope. Chop it into two sections and split the weight between you and your partner.

 

Also you might consider using a redirected rappel (Z-rappel) for rappelling on skinny ropes. In the photo below, the blue cord is the rappel extension sling. The skinny (red) rap line comes through the device, down to a biner on your belay loop, up to another carabiner on the device, then down in the normal brake position.