Half / twin rope belaying devices and friction with < 8.0 mm diameter

Hello Mountain Project forum members,

I have been reading along those lines and threads here, but now I’m looking for specific advice and accordingly have made my first post here. 

I’m currently testing the half / twin ropes I just got – the Mammut 7.5 Alpine Sender ropes. I would like your experience and recommendations for abseiling, belaying technique, ideally on half-rope technique and the belay devices you use for sufficient amount of friction / catching force on thin ropes. 

I have experience with belaying via half and twin rope technique with a Mammut Dry 8.0 system. In particular, with the Edelrid Giga Jul I have also been able to catch large falls using the half-rope technique with the 8.0 rope (fall factor < 0.3). 

I am looking for a suitable belay device for the Mammut Sender 7.5 mm. So far I have tested the rope in combination with Petzl Verso (according to the instruction manual for ropes from 7.1 to 9.2 mm) and Giga Jul. Even when abseiling, I find it difficult to generate enough friction to abseil comfortably and safely, i.e. I find it very hard to hold the position without loading the prusik. The best way seems to be without a belay device, simply with (Super-)Munter. However, for belaying in half rope technique I need to use a device, e.g. with an additional carabiner. Using the Giga Jul with a double carabiner improves the behavior to such an extent that I feel comfortable belaying using twin technique for now. 

I'm still suspicious of the breaking action using half-rope technique: if my climber falls into one of the half ropes and the friction is halved compared to falling into the twin rope, I'm afraid I won't be able to catch this fall. This applies even more if, for example, falling into the belay station with a fall factor > 1. 

What is your experience with the use of 7.5 mm ropes using half-rope technique? Which belay devices have proven successful with ropes of such diameter? Are there any particular device-carabiner combinations which you can recommend for this specific rope or ropes like the Skimmer, etc.? Would you rather go for the ATC-Guide Alpine, Nano Jul or CT Alpine Up? And how does the friction in those compare to the Reverso? 

Thanks, Im really curious to hear from you and your experience with such thin half ropes.

Use the microjul. The ropes themselves work great. Catching should be easier since the rope absorbs more of the fall.

7.5 mm twin ropes is within the range of all these devices.  The smallest rope I have used in the alpine up and the ATC-guide alpine is 8.0 mm so take my advice with a grain of salt.  The alpine up is my daily driver and I would choose that unless weight is a concern.  If weight is a concern I would use the ATC-guide alpine.  I have a nano-jul but I don't like it very much and rarely use it.  But the nano/mega juls have a strong following but not me.  I like the giga-jul much better than the nano/giga jul and your rope is within it's acceptable range.  I prefer the alpine up but it is pretty good competition. 

I’ve been climbing ice for a few seasons now with 6.9 twins. Microjul is fine but I prefer BD atc-alpine guide. 

Thx for the quick replies ...

John Sigmon wrote:

Use the microjul. The ropes themselves work great. Catching should be easier since the rope absorbs more of the fall.

Hmm, not a big fan of the Juls other than the Giga Jul ... other than that, I'm with you. Do you own the Alpine Sender 7.5?

climber pat wrote:

7.5 mm twin ropes is within the range of all these devices.  The smallest rope I have used in the alpine up and the ATC-guide alpine is 8.0 mm so take my advice with a grain of salt.  The alpine up is my daily driver and I would choose that unless weight is a concern.  If weight is a concern I would use the ATC-guide alpine.  I have a nano-jul but I don't like it very much and rarely use it.  But the nano/mega juls have a strong following but not me.  I like the giga-jul much better than the nano/giga jul and your rope is within it's acceptable range.  I prefer the alpine up but it is pretty good competition. 

Yes, but the rope diameter is also within the Reverso's range and I did not like the breaking performance of it; slip on rappelling was quite strong. The Giga Jul is stating on its side that it is working with 7.1 to 10.0 mm ropes, but half ropes are only rated from 7.9 to 9.2 mm. Accordingly, so 7.5 is too small, even though with two carabiners it kind of does (suboptimal).  

I thought about the Alpine Up, but would like confirmation from someone with the same or a very similar rope that it actually works reliably.

Why don't you like the Nano Jul and is it any different from the ATC-Guide Alpine? 

Val I wrote:

I’ve been climbing ice for a few seasons now with 6.9 twins. Microjul is fine but I prefer BD atc-alpine guide.

How does the BD ATC-Guide Alpine bite on the 6.9 mm? How much does it creep through on rappelling?

Ive used the CT Alpine up for a few years now. This past ice season I had new Sterling 7.7 Dyads. Belayed like a dream. Rappelling was fine with a normal setup. Didn't need to add friction. I can't say I caught any lead falls but top roping was fine to hold and lower. Not quite the same as the Mammut 7.5s but pretty close.

Martin Berlin wrote:

Hmm, not a big fan of the Juls other than the Giga Jul ... other than that, I'm with you. Do you own the Alpine Sender 7.5?

Not currently. I had it’s predecessor the Twilight, had the alpine sender, and have owned a few other twin/halves. Why?

Martin Berlin wrote:

Thx for the quick replies ...

Hmm, not a big fan of the Juls other than the Giga Jul ... other than that, I'm with you. Do you own the Alpine Sender 7.5?

Yes, but the rope diameter is also within the Reverso's range and I did not like the breaking performance of it; slip on rappelling was quite strong. The Giga Jul is stating on its side that it is working with 7.1 to 10.0 mm ropes, but half ropes are only rated from 7.9 to 9.2 mm. Accordingly, so 7.5 is too small, even though with two carabiners it kind of does (suboptimal).  

I thought about the Alpine Up, but would like confirmation from someone with the same or a very similar rope that it actually works reliably.

Why don't you like the Nano Jul and is it any different from the ATC-Guide Alpine? 

How does the BD ATC-Guide Alpine bite on the 6.9 mm? How much does it creep through on rappelling?

It’s totally fine ( I do back up my rappels when using twins). 

Jake woo wrote:

It’s totally fine ( I do back up my rappels when using twins).

Nice – I've ordered an ATC-Guide Alpine. Let's see. I'll report back. 

(And yes, I backup as well, but I would like to be completely in control on rappelling without the prusik biting, i.e. able to comfortably stop the slip.)

Jake woo wrote:

Ive used the CT Alpine up for a few years now. This past ice season I had new Sterling 7.7 Dyads. Belayed like a dream. Rappelling was fine with a normal setup. Didn't need to add friction. I can't say I caught any lead falls but top roping was fine to hold and lower. Not quite the same as the Mammut 7.5s but pretty close.

Let me see how the ATC Alpine performs ... 7.7 mm sounds close enough; next step :)

Jake woo wrote:

Not currently. I had it’s predecessor the Twilight, had the alpine sender, and have owned a few other twin/halves. Why?

Get a better idea of your background. As written above, Im no big fan of (Mega) Jul. What other devices have you been using?

Just use two carabiners in your device for more friction. I climbed for years with the predecessor Twilight 7.5 ropes and if the rappel was super steep or I had a heavy bag that’s what I did. Worked great.

Norm Larson wrote:

Just use two carabiners in your device for more friction. I climbed for years with the predecessor Twilight 7.5 ropes and if the rappel was super steep or I had a heavy bag that’s what I did. Worked great.

Norm Larson wrote:

[... ]Using the Giga Jul with a double carabiner improves the behavior to such an extent that I feel comfortable belaying using twin technique for now. 

I'm still suspicious of the breaking action using half-rope technique: if my climber falls into one of the half ropes and the friction is halved compared to falling into the twin rope, I'm afraid I won't be able to catch this fall. This applies even more if, for example, falling into the belay station with a fall factor > 1.

[...]

Yes, I see that and have tested that. And rappelling does work ok, as I have written. I am still worried about the half rope technique (not twin rope technique).

Norm Larson wrote:

Just use two carabiners in your device for more friction. I climbed for years with the predecessor Twilight 7.5 ropes and if the rappel was super steep or I had a heavy bag that’s what I did. Worked great.

If you need 2 carabineers to rappel then you should be using 2 carabineers to belay 

Last year Edelrid put out a new one called NanoJul.  From the photos, it looks a lot more promising than the tooth-less MicroJul.

For the love of god please don't trust the manufacturers' stated diameter ranges (OP has already figured this out, just want to reassure him he is correct).  There is no standard on how the ranges are measured, what we get is a function of the marketing department's conscience.

I want to  add or repeat some cautions.

(1) Ropes of the same diameter by different manufacturers may perform very differently in braking devices, either because the diameters aren't really the same or because of other features of the rope construction and waterproofing.  

(2) The extremes of the ranges claimed for braking devices seem to me to be very optimistic.  In particular, braking may not be good with ropes at the low end of the device specs.

(3) If you find you need two carabiners to get sufficient friction from your device for rappelling, then you sure as hell need two carabiners for belaying.

Because of all this, you can't necessarily rely on the experience of other folks.  I suggest a minimal test for belay device functionality is the controllability of a single-strand free-hanging rappel. If you can't manage that comfortably, the friction of your device is inadequate.

rgold wrote:

Because of all this, you can't necessarily rely on the experience of other folks.  I suggest a minimal test for belay device functionality is the controllability of a single-strand free-hanging rappel. If you can't manage that comfortably, the friction of your device is inadequate.

This is the point: I am struggling to create sufficient friction on a single strand, as tested on my pull-up bar. That is exactly why I am here collecting as much info as possible from you. 

rgold wrote:

(2) The extremes of the ranges claimed for braking devices seem to me to be very optimistic.  In particular, braking may not be good with ropes at the low end of the device specs.

This used be more true in the past when manufactures gave a range that was simply x.x mm to y.y mm and not breaking the range down by rope type (single, double, twin).  Now most manufactures give two or three ranges depending on rope type.  I think maybe UIAA labeling requirements might have changed. While the performance of the belay device at the edges of the range may not be satisfying they are no longer ridiculous.  I wrote black diamond in 2011 complaining that their ATC guide device was unsafe and inadequate for skinny ropes even though the rope was in the x.x to y.y range but the rope was rated a single and they assumed at time of manufacture that there were no single ropes that small.  Black Diamond released the ATC-Guide Alpine about like 8 years later.  Sadly even buying some crusty partners a new ATC-Guide alpine was not enough for them to get a clue and use it, rather they continued to use 2 carabiners to rappel and one to belay.  :( 

Often the ranges a limited by the available ropes at the time of manufacture.  Our beloved Alpine up is an example of that.  CT actually came out with a statement saying that older Alpine Ups are suitable to use with ropes narrower than what was printed on the original device when sub 9.0mm single ropes came out.  They also reduced the double and twin rope range too without changes to the actual device.  The reason they were able to do this is because the device has a fairly long slot the locking carabiner slides in and it had enough range, something non-giga juls do not have. 

About 15-20 years ago I went on a device hunt when I noticed my reverso was not producing enough friction to easily hold my partner when he was hanging on a new skinny/dry rope.  I order about 10 (include mega-jul, micro-jul, alpine smart, alpine up) devices that were on the market at the time and settled on the Alpine Up as the best of the breed.  I still buy new devices just to see if they are any better and I have not found one that I think is more reliable that the Alpine UP.  Although I have put these anti-cross load things gate bumpers on my belay carabiner which drastically reduces the device's desire to rotate around and cross load the carabiner which is the Alpine UPs major weakness. 

Martin Berlin wrote:

This is the point: I am struggling to create sufficient friction on a single strand, as tested on my pull-up bar. That is exactly why I am here collecting as much info as possible from you. 

How often are you single strand rappelling with a two rope system like this? I don’t think I’ve ever had to.

John Sigmon wrote:

How often are you single strand rappelling with a two rope system like this? I don’t think I’ve ever had to.

I think you are missing the point.  The single-strand free-hanging rappel is a minimal test of the ability of the device to hold a fall on a single strand.

As I said I typically use a micro jul or giga jul so yeah the connection between hanging single strand and catching a lead fall didnt occur to me. I figured OP was trying to simulate a rappelling scenario.

rgold wrote:

I think you are missing the point.  The single-strand free-hanging rappel is a minimal test of the ability of the device to hold a fall on a single strand.

Yeah, just for testing and emergency.

Simple assumption. If you are unable to comfortably hold a single-strand rappel you are for sure unable to catch a high fall-factor fall on a single strand (i.e. if the second rope is clipped such that it does not provide any additional support to the catch).

I got the ATC-Guide Alpine in the mean time and I am pretty pleased with the performance. I even found it to have significant friction on cords of 5 and 6 mm [which I would not rappel on, to be explicit here.]

I'm thinking about getting a second belay device. My climbing partners often use the reverso or ATC (Guide), which I am not too happy about. 

On top, I read above that @climber pat and @Jake Woo recommend the CT Alpine Up. I tried to find some reviews online, but there does not seem to be a lot of info on double rope belay in general or on specific devices. Are there more opinions here on this forum on the CT Alpine Up? 

Thx, everyone!