Autoblock or Prusik

Ancent wrote:What size cord do people use in either case (above or below the belay device)? My prusiks tend to be 5 or 6 mm, but I have used 4 mm with an extra wrap if it doesn't seem strong enough.

http://www.sterlingrope.com/c/climbing_sewn-cord_6mm-sewn-cord?action_type=switch_product&selected_cat_keys=1114670.54622.1114348.0.0&selected_product=af86f7add74cffb56e9881e7cb6c8941&redirected_post=1

I use this from Sterling, 6mm. It is more expensive than just buying cord to length, but it's sewn, convenient, and compact because I don't have to tie a double fishermans to join the two ends. Can be tied in either prussik, autoblock, or klemheist. Can be used for rigging a haul system as well.

Craig Childre wrote: I believe the problem using smaller cord is it slips too much. I use the same size you do.

Smaller cord grips BETTER. The greater the difference between the rope and the cord, the better it holds.

Ancent wrote:What size cord do people use in either case (above or below the belay device)? My prusiks tend to be 5 or 6 mm, but I have used 4 mm with an extra wrap if it doesn't seem strong enough. Can the below-the-atc autoblock methods get away with thinner cord (and still be safe) since these are not bearing the weight of the climber? I'd assume so.

In general the prusik is sized relative to the rope it is on. Too large and it won't bite; too small and (in my experience) it bites too hard.

I believe the common target is 70-80% the diameter of your rope. In practice this normally means 2mm smaller than your rope.

Could you use 4mm cord? In an emergency, go for it! At just under 4kN, you lose a lot of safety margin but it is still pretty strong. In fact I often carry a length of 4mm as emergency cord, good for a prusik or tether or whatever I need it to be. But as part of your normal toolkit, doesn't it make more sense to have a prusik that is correctly sized and can be used for anything, not just as a third hand?

But slip issues aside, the different backup methods have different concerns regarding strength, and therefore, diameter. The prusik method requires the cord to bear your weight whereas the autoblock only guides the rope through your ATC in the locked position. That said, it seems like one can get away with a smaller diameter cord for any backup that occurs under the ATC.

EDIT: Just saw the message above and I 100% agree. Just because the third hand methods allow for a skinnier backup cord does that mean that one should be carrying 3-4 mm cord, since a nice 5-6 mm would give me confident ascending, anchor building, etc and provide more function that just a third hand backup for rappelling.

csproul wrote: Smaller cord grips BETTER. The greater the difference between the rope and the cord, the better it holds.

I believe I was completely wrong! ;)

Back on point. Using the smaller cord.... considering Sprouls revelation.... an issue using the smaller cord is that it catches too often and can be hard to manage as you slide it down the rope. Also, it becomes increasingly difficult to release the greater the difference in cords.

Ancent wrote:But slip issues aside, the different backup methods have different concerns regarding strength, and therefore, diameter. The prusik method requires the cord to bear your weight whereas the autoblock only guides the rope through your ATC in the locked position. That said, it seems like one can get away with a smaller diameter cord for any backup that occurs under the ATC.

In the case we are discussing, I believe the "slip" issues are the reason any of these friction knots are used primarily. They are there for gripping the rope, like a hand, and each has a different grip strength when a load is applied. The overall strength of the cord is not the concern here.

Pretty much all the material cord used by climbers for this application has a strength greater than what most situations would call for.

In a rappelling situation with the friction knot below the belay device there should not be a considerable amount of weight being applied when hands free.

To be even more safe when hands free... make a few wraps around your leg with the free ends of the rope.

The prusik would grip the rope and be a bit more hard to loosen than would an autoblock. Each has it's place and can be used in the same concept, but there are pros and cons to each. Knowing when to apply this one or that one to make your life easy and keep you safe is the golden nugget.

Patrick Shyvers wrote:Putting the knot above the device does have its plusses, but you better know how & be ready to ascend the rope when that knot jams, so I am always hesitant to show someone that way. If they need someone to teach them about third hands, do they know how to ascend yet?

Good comments, seriously.

Someone who doesn't know how to unweight a rap device (or a hitch above the device) should not be rappelling ... or at least they should have a guide around who can rescue them.

Craig Childre wrote:One small issue with the back up above your rap device is the difference in shock loading.

As I said, I don't trust a hitch above (or below) to catch a surprise fall. So the answer to the question of whether I'd trust it to catch under shock-loading conditions should be obvious - although I suspect the risk differential is negligible compared to other risks.

For about a year, I did use a hitch below the device as you suggest. But I found enough issues with it that I switched back to the hitch above.

Bill Lawry wrote: As I said, I don't trust a hitch above (or below) to catch a surprise fall.

The hitch below, the third hand, does not do the catching, the rappel device does the catching. That as why this method, along with extending or cowtailing the rappel, has caught on.

Rick Blair wrote: The hitch below, the third hand, does not do the catching, the rappel device does the catching. That as why this method, along with extending or cowtailing the rappel, has caught on.

I know the difference.

david doucette wrote:I love the autoblock. doesn't take anytime once you know how to set it up. this is the best one; gearexpress.com/sterling-au…

The hollow block is nicer for rap backup: backcountry.com/sterling-ho…

The aramid fiber handles higher heat (for those who like to rap faster), the flat cord really gets a good bite and is a bit easier to handle (doesn't seem to kink up as much). The 13.5 is a perfect length for a 3 rap off the inner leg loop to stay out of your device used off the belay loop.

I tried the extended rappel quite a few times and prefer the belay loop myself in most situations. The one time I will extend is if I am using a ropes under 8mm with a pack on, then I appreciate being able to grab the brake strand with both hands up high. I don't drop my pack off the haul loop because it's never *that* heavy and the whole process just seems too cumbersome.

- use 6mm cord ... Itll work fine on anything from 8-10+ mm ropes ... However make sure the cord is supple not stiff

- use a kleimheist ... The reason why i say this is that i you had to teach a single knot for rappel purposes, the kleimheist is easy to remember, if you screw it up it becomes a hedden and still holds (even better) and you can use it with slings if needed ... Make sure they know how to release it

- two wraps should be fine for most thicker dual strand raps ... For thin ropes perhaps 3 wraps may be called for .... Experiment to find out what works

- generally the kleimheist below the device .... Theres been many a stuck rappel with the knot above the device

- if you need to reascent its easy enough to set a knot above the devce mid rappel with the caveat below

- if you want to extend the rap its up to you ... If you do make sure you can reach the rope well above the device to set up a sling for the foot ...

- when passing a knot its generally easier to do so with a non extended device

- for reascending an extended rap is easier to transition if you have an ATC guide or other such device .... However pulling through 2 thicker strands on autoblock ascending is a biatch, in this case a 3-1 pulley can easily be set up off the harness mid rap

- with modern harness with auto buckles, clip the inside of the leg loop for the kleimheist .... Not the buckle side itself ... If non extended

- if you have too long a cord simply use a clove on the biner to adjust the length ... Keep the fishermans on the outside or clip the loose bight to prevent pull through

- at worst if you dont have cord or sling you can always use the rope end as a friction backup with a penberthy or blakes hitch

Theres probably tons moah ... But then im sleepy right now ... And it takes MP flame wars for me to breed my best and biggest beahs

;)

bearbreeder wrote:- when passing a knot its generally easier to do so with a non extended device )

We're a bit OT now, but anyway this depends on what method you use. The knot-passing method I think is the best requires extending the device. For those who don't already know it, here's what you do:

1. Mount your regular rappel device (referred to as ATC hereafter) immediately below the knot, tie it off securely, and clip to harness belay loop. Once past the knot you'll be rappelling with this.

2. Put a Munter-type carabiner on a fairly long extension and clip it to the rope at the anchor with a Munter hitch. So when you start, the rope goes from the anchor to the Munter hitch on extension, then a big loop, back up to ATC, just below the knot, on belay loop, and then down.

3. Rappel on the Munter until you are hanging from the ATC. In order for the weight transfer to happen, the Munter has to be on an extension. (Practice this somewhere safe to dial in how long the extension has to be.)

4. Now for the cool part: you can "pop" the Munter off the rappel rope even though it is still at least partially loaded. Just open the gate on the Munter biner and...try it, you'll see.

5. Release the tied-off ATC and continue down.

No prussiks, no standing in slings, no transferring the ATC, minimal equipment, what could be bad?

Well, maybe three things. If the Munter twists your rope badly, you might have to unclip the ATC, unwind the twists and clip it back in. You could also opt to leave it unclipped while doing the Munter rappel and just clip it in when you reach it.

Rappel backup: the simplest thing to do is to install an autoblock on a leg loop to act as an autoblock for the ATC. This leaves you without an autoblock for the Munter part of the rappel. If you want one for that, you can either install a second autoblock or use a single one that you shift at the transition point.

And obviously, the method only works if there is but a single knot to be passed.

rgold wrote: We're a bit OT now, but anyway this depends on what method you use. The knot-passing method I think is the best requires extending the device. For those who don't already know it, here's what you do: 1. Mount your regular rappel device (referred to as ATC hereafter) immediately below the knot, tie it off securely, and clip to harness belay loop. Once past the knot you'll be rappelling with this. 2. Put a Munter-type carabiner on a fairly long extension and clip it to the rope at the anchor with a Munter hitch. So when you start, the rope goes from the anchor to the Munter hitch on extension, then a big loop, back up to ATC, just below the knot, on belay loop, and then down. 3. Rappel on the Munter until you are hanging from the ATC. In order for the weight transfer to happen, the Munter has to be on an extension. (Practice this somewhere safe to dial in how long the extension has to be.) 4. Now for the cool part: you can "pop" the Munter off the rappel rope even though it is still at least partially loaded. Just open the gate on the Munter biner and...try it, you'll see. 5. Release the tied-off ATC and continue down. No prussiks, no standing in slings, no transferring the ATC, minimal equipment, what could be bad? Well, maybe three things. If the Munter twists your rope badly, you might have to unclip the ATC, unwind the twists and clip it back in. You could also opt to leave it unclipped while doing the Munter rappel and just clip it in when you reach it. Rappel backup: the simplest thing to do is to install an autoblock on a leg loop to act as an autoblock for the ATC. This leaves you without an autoblock for the Munter part of the rappel. If you want one for that, you can either install a second autoblock or use a single one that you shift at the transition point. And obviously, the method only works if there is but a single knot to be passed.

Sometimes you dont even know you need to pass a knot till mid rappel

Like when you start rapping down and realize that theres a coreshot mid way =P

If one should learn a single technique it would be the standard knot pass as it can be done in any situation and much of the technique applies to reascending as well

;)

Both of these techniques are also described here: mountainproject.com/v/is-th…

rgold wrote: We're a bit OT now, but anyway this depends on what method you use. The knot-passing method I think is the best requires extending the device. For those who don't already know it, here's what you do: 1. Mount your regular rappel device (referred to as ATC hereafter) immediately below the knot, tie it off securely, and clip to harness belay loop. Once past the knot you'll be rappelling with this. 2. Put a Munter-type carabiner on a fairly long extension and clip it to the rope at the anchor with a Munter hitch. So when you start, the rope goes from the anchor to the Munter hitch on extension, then a big loop, back up to ATC, just below the knot, on belay loop, and then down. 3. Rappel on the Munter until you are hanging from the ATC. In order for the weight transfer to happen, the Munter has to be on an extension. (Practice this somewhere safe to dial in how long the extension has to be.) 4. Now for the cool part: you can "pop" the Munter off the rappel rope even though it is still at least partially loaded. Just open the gate on the Munter biner and...try it, you'll see. 5. Release the tied-off ATC and continue down. No prussiks, no standing in slings, no transferring the ATC, minimal equipment, what could be bad? Well, maybe three things. If the Munter twists your rope badly, you might have to unclip the ATC, unwind the twists and clip it back in. You could also opt to leave it unclipped while doing the Munter rappel and just clip it in when you reach it. Rappel backup: the simplest thing to do is to install an autoblock on a leg loop to act as an autoblock for the ATC. This leaves you without an autoblock for the Munter part of the rappel. If you want one for that, you can either install a second autoblock or use a single one that you shift at the transition point. And obviously, the method only works if there is but a single knot to be passed.

I often rap with an extended autoblocking device in what I call "carabiner brake mode". In this mode, I can pretty much do what you've described without 1) setting everything up at the anchor; 2) use a munter first to twist the rope. It's probably even easier to pop the rope off my "carabiner brake mode" than the munter hitch.

Step 1: rap with my extended autoblocking device with a below the device backup.
Step 2: when I get close to the knot I need to pass, go hand-free by doing a leg wrap.
Step 3: pull up rope to set up a munter hitch rappel below the knot, transition my rappel backup to below the munter hitch. Tie a backup knot below the munter if I'm feeling extra cautious.
Step 4: drop the rope, undo the leg wrap, rap till I can get my weight on the munter.
Step 5: pop the brake biner out of my autoblocking device, it helps if the rappel is low angle or if you're strong enough to temporarily lock-off with one arm above the device. You can only do this in the "carabiner brake" mode with an autoblocking device, in a conventional ATC-like rappel set up you'll most likely drop the device.
Setp 6: rap on the munter.

I've used this "carabiner brake mode" with ATC Guide, Mammut Alpine Smart, and Trango B-52. But it does not work with all autoblocking device, for example, the Mega Jul is shaped in a way to twist the rope as it enters the device, and eventually the twist will knot itself and you'll get stuck on the rope (ask me how I know...). So better test this with your device first before trusting it. Mammut is aware of this method and they're ok with it. BD on the other hand, was less than helpful (probably because the liability issues in the US).

aikibujin wrote: I often rap with an extended autoblocking device in what I call "carabiner brake mode". In this mode, I can pretty much do what you've described without 1) setting everything up at the anchor; 2) use a munter first to twist the rope. It's probably even easier to pop the rope off my "carabiner brake mode" than the munter hitch. Step 1: rap with my extended autoblocking device with a below the device backup. Step 2: when I get close to the knot I need to pass, go hand-free by doing a leg wrap. Step 3: pull up rope to set up a munter hitch rappel below the knot, transition my rappel backup to below the munter hitch. Tie a backup knot below the munter if I'm feeling extra cautious. Step 4: drop the rope, undo the leg wrap, rap till I can get my weight on the munter. Step 5: pop the brake biner out of my autoblocking device, it helps if the rappel is low angle or if you're strong enough to temporarily lock-off with one arm above the device. You can only do this in the "carabiner brake" mode with an autoblocking device, in a conventional ATC-like rappel set up you'll most likely drop the device. Setp 6: rap on the munter. I've used this "carabiner brake mode" with ATC Guide, Mammut Alpine Smart, and Trango B-52. But it does not work with all autoblocking device, for example, the Mega Jul is shaped in a way to twist the rope as it enters the device, and eventually the twist will knot itself and you'll get stuck on the rope (ask me how I know...). So better test this with your device first before trusting it. Mammut is aware of this method and they're ok with it. BD on the other hand, was less than helpful (probably because the liability issues in the US).

How do you rappel on autoblock mode in guide devices?

Perhaps step by step photos will make it clearer for simple folks like us

;)

Those pictures make it look like the wrong strands are loaded. Starting with the reverso3 petzl had instructions on how to ascend, looks like the same set up.

Edit: I didn't understand what you were trying to accomplish at first, now I see you are creating a rappel that will undo under load, pretty cool.

aikibujin wrote: It's probably even easier to pop the rope off my "carabiner brake mode" than the munter hitch.

The opposite is true. Try both methods while free-hanging and see. Or, for example,

aikibujin wrote: ...it helps if the rappel is low angle or if you're strong enough to temporarily lock-off with one arm above the device.

No accommodating terrain or feats of strength are needed for the Munter pop.

Additionally,

aikibujin wrote: You can only do this in the "carabiner brake" mode with an autoblocking device, in a conventional ATC-like rappel set up you'll most likely drop the device.

The Munter pop technique works with all other devices.

bearbreeder wrote: How do you rappel on autoblock mode in guide devices? Perhaps step by step photos will make it clearer for simple folks like us ;)

For the ATC Guide it isn't really autoblock mode, because the key component to autoblock mode is the weighted strand pinching/trapping the brake strand into the toothed channel. His particular usage isn't all that dissimilar from normal rappelling, the main difference being the alignment/rotation of the ATC.