Backing up rappells: Who does it?

johnnymuir wrote: Perhaps I am. I thought the idea was more to test the system as it is going to be used, not how things will react in the worst possible scenario.

In discussions like this, right or wrong, I usually default to the 'loss of rap control' view.

For the other view - 'consciously going hands free' - I'm not comfortable trusting my life to one hitch.

I probably shouldn't jump into one of these clusterfuck threads that distracts me from work. But I am at a loss. I've been skimming this, and I hear autoblock vs. prussik? Don't know the difference??? I've always referred to a 24" knotted loop of cord as my "prussik" and its application as a rappel backup as an "autoblock" (essentially using the words interchangeably). And then I'm reading all these tales that this autoblock won't always work??? I guess I don't use that much variation in rope size, but it seems to me that my (I think 5mm prussik) has worked as an autoblock (wrap 3 and pull) in every single application I have ever used it. I standardly climb on a 10.1, but use other's 9.1s and have never, ever had a problem.

And I know there are two ways to form the prussik knot. I use a wrap three and pull. Essentially triple-girth-hitched onto rope. It works every time. I've had other people show me that in the argument of laziness they do a simple wrap x-times method. I don't see how the 0.x miliseconds extra req'd for the former method is of needing scrutiny.

Enlighten me

gription wrote: Please make this about the question not about what back up is superior to another..

ahem...cough cough.

Mmmm apologies for my ignorance and supporting stupid thread drift. ok I am up to speed. Now maybe i'll reread and see if someone is suggesting that a prussik knot is not a sufficient backup knot, I would be astounded to find that to be the case. Seem to me you buy the right diameter cord from the get-go and you're all set.

Edit: OH Gription, it's your thread?!?! Yeah use a prussik, why not? It is very, very, very rare that I don't use one. I use prussik, cinch tight and then break the knot and keep it real loose and in my low hand. Keeping it in my low hand and down the rope it is never an annoyance. Makes for any unexpected events to go a lot smoother, and gives me peace of mind.

Tom Sherman wrote:I hear autoblock vs. prussik? Don't know the difference??? I've always referred to a 24" knotted loop of cord as my "prussik" and its application as a rappel backup as an "autoblock" (essentially using the words interchangeably).

I think this usage is becoming more and more common. I spoke this way myself earlier. But the original terminology referred to the knots, not what they were being used for.

Tom Sherman wrote:And then I'm reading all these tales that this autoblock won't always work...it seems to me that my (I think 5mm prussik) has worked as an autoblock (wrap 3 and pull) in every single application I have ever used it.

Most people don't have problems of course. That isn't the same as there being no problems.

Tom Sherman wrote: I've had other people show me that in the argument of laziness they do a simple wrap x-times method. I don't see how the 0.x miliseconds extra req'd for the former method is of needing scrutiny. Enlighten me

The "wrap x-times" is the autoblock knot. It has lower maximum holding power but is much more easily released under load. Properly adjusted, it tends to run more smoothly then prussiks, kleimheists, heddens, etc. etc. Which knot you use is a matter of personal preference, but speed of execution is not one of the considerations.

Tom Sherman wrote:Now maybe i'll reread and see if someone is suggesting that a prussik knot is not a sufficient backup knot, I would be astounded to find that to be the case. Seem to me you buy the right diameter cord from the get-go and you're all set.

Have seen 3-wrap and 4-wrap 6mm prusik fail to grab on ~10mm rope unless pre-tensioned ... many times over 13 years ... usually on a single strand of rope (but not always) ... usually when it is cold outside.

Bill Lawry wrote: Have seen 3-wrap and 4-wrap 6mm prusik fail to grab on ~10mm rope unless pre-tensioned ... many times over 13 years ... usually on a single strand of rope (but not always) ... usually when it is cold outside.

I remember being told a formula as to what diameter cord to buy, but my memory is failing me?

Tom Sherman wrote:I use prussik, cinch tight and then break the knot and keep it real loose and in my low hand.

I think its prudent:

Form Knot
Cinch Knot (dress)
Break Knot (loosen)

then again I've never just dropped the rope and see what goes so maybe i'm living a lie? But every time I go into a conscious rest, it grabs immediately.

Tom Sherman wrote:I've never just dropped the rope and see what goes so maybe i'm living a lie? But every time I go into a conscious rest, it grabs immediately.

Same. Maybe a test in order, from a few off the ground with many pads around?

Bill Lawry wrote: Have seen 3-wrap and 4-wrap 6mm prusik fail to grab on ~10mm rope unless pre-tensioned ... many times over 13 years ... usually on a single strand of rope (but not always) ... usually when it is cold outside.

IMO, 6mm is too big for a rap backup.

csproul wrote: IMO, 6mm is way too big for a rap backup.

Does your comment apply whether or not the rap backup is below the device?

Bill Lawry wrote: Does your comment apply whether or not the rap backup is below the device?

I've never used one above the device. I use it below on the leg loop and have tried it on the belay loop too. I use more like 4mm. I'm not sure I'd trust 6mm to reliably grab a single rope and you said you'd seen it slip. I've let go of the rope with a 4mm backup many times and it has never slipped any amount. I do agree that a reliable backup is probably more sensitive to a variety of setup factors and mostly people are unaware of whether or not it will work since few ever actually test the system under realistic conditions.

Edit: I'd have to look at the cord that I use to be sure if it's 4mm or perhaps 5mm, but certainly smaller than 6, especially with a single strand.

csproul wrote: I've never used one above the device. I use it below on the leg loop and have tried it on the belay loop too. I use more like 4mm. I'm not sure I'd trust 6mm to reliably grab a single rope and you said you'd seen it slip. I've let go of the rope with a 4mm backup many times and it has never slipped any amount.

Not sure whether you are pre-tensioning the 4mm every time. It would be good to know if some of these were without pre-tensioning.

Over the years, I've tried above and below the device. Always 6mm cord above the device ... probably taught that due to it seeing full body weight. I used 5mm cord for below the device but stopped rigging that way after a ~year of use for various reasons.

csproul wrote:I do agree that a reliable backup is probably more sensitive to a variety of setup factors and mostly people are unaware of whether or not it will work since few ever actually test the system under realistic conditions.

Thanks - since the topic came up of testing the system, the above is the main thing I wanted to get across. The number of important setup factors can be surprising.

I've done both: pre tensioned with the intent of hanging mid rappel, or tried completely letting go with the hitch tightened as it would be during normal rappelling.

Brian W. wrote: [Referring to Sterling Hollowblock] Question: I bought a couple of those too (one in each length) and for me, they absolutely don't work on a single line - even with 5 wraps on a 10.1 rope the autoblock just slips right through (works fine with 2 ropes). Do you have that experience with yours?

I tried the shorter hollowblock on a single 8mm line this weekend, wouldn't come even close to locking. Think it was 4 wraps, the most I could put on the rope. I'm not terribly worried about it though, the only time I rap on a single strand is in a group of 3 (tie off with a locker at the top, first two climbers simul rap w/o worry of the rope shifting, third takes 8/overhand and locker off, raps on both strands). That's pretty rare. I've been using a megajul so if the anchor is bomber I'd just set it for autolocking next time. I hate rappelling set that way, herky and jerky as hell.

I use an autoblock if I'm the first to rap on a multi pitch route and frequently in the alpine. Normal cragging days it doesn't come out. Perfect case was an alpine route in the cascades, rap went through a moat with a good squeeze against the rock on your right. Ice gave way under my left foot just as I popped through the constriction, I swung down into an alcove with a vice grip on the rope. Technique won, but if I had of smashed my right hand against a rock.....

Jake Jones wrote: Prussik Klemheist

Thank you. That's the first time I've seen the difference between kleimheist and the autoblock. I've always been a fan of the kleimheist. I always test it, and it's always worked to this point.

Every rap, every time. life is tough and sometimes short when you are stupid....
Climb big ice at the lake on skinny lines and you will become a believer. yes it works if you set it up right. the auto block adds much needed brakeing power when useing skinny ropes. biner with 5mm cord is ductaped to me leg loop. takes less than 5 sec to implement and I always have that extra peice of cord for emergencys.

I always do, its better then not and wishing you did. Like buying car insurance, and never needing it. As far as belaying goes, chances are somebody else might be around to help out, or see potential for something going wrong or a good belayer should be able to look for potential dangers prior to belaying and paying attention to the climber and anything dislodged.

I use an auto block on multi pitch , if I have to clear the rope , or it is awkward to get to the next anchor, free hanging . Don't use it on low angle slab because i weigh 100 lbs and I would never get down, situational I guess, I keep my device on a cow's tail and the auto block below it

a few points ...

first ...if you have too little friction rather than relying on an autoblock, its better to add friction the proper way

- add a second biner clipped to the belay loop and ATC

- or/and set up a Z friction system ... this is in fact a very important skill as you can set it up mid rap

the more force which is on the friction knot the more wraps you need to use, which may make some knots harder to release and the rappel jerky ... also if you use too few wraps it may not hold "hands free" especially if the ropes get muddy or icy

a friction knot backup is always easy to add mid rap if needed ... in fact this is a critical skill if the rap becomes more complex than anticipated or you need to pass a knot .... simply stop with the leg raps, tie a catastrophe knot and set up the backup

second ... its seems folks have issues with their friction knots gripping on with certain cord/rope combos ... you should ALWAYS be able to get a knot to grip ...

ive used 6mm cord just fine on anything down to 8 mm ... its simply using the proper friction knot and number of wraps ... the trick is to get supple cord which grips better than stiff cord

note that one should cut their cords a bit longer than normal so that you can get more wraps if needed ... you can always shorten it with an overhang

lets start with the "standard" rap setup with a kleimheist ... for something such as rapping on dual strand ~10mm you dont want something that grips like a bear to a honey jar, otherwise itll be difficult to slide down and your rap will be jerky ...

a 2-3 wrap kleimheist is easy to setup, works with SLINGS as well, and is almost impossible to screw up ... once shown and practiced a few times even newbies can remember it for a very long time

its easier to setup than an autoblock and less sensitive to getting it "exactly" right

the other advantage (especially for knot passing) is that its much easier to take apart than a prussik

if one needs a bit more gripping power one can simply use more wraps

now if one needs alot more gripping power then you just use and upside down kleimheist called the hedden ... this sucker grips like a killer whale latched onto a tasty seal

It is important to pass the sling through as shown by the arrows, since the opposite configuration (passing over at the top arrow and under at the bottom) will cause the knot to bind.

you can use it with SLINGS or cord ... in fact with a nylon sling a 4 rap hedden will grab onto a 8mm single strand just fine, ive used it as such for belay escapes ...

the gripping power is so powerful that the standard is ~1-2 wraps for normal cord and rope

note that this makes the hedden a POOR choice for normal dual strand raps with say 6mm cord on 10mm rope as it will stick too much ... but if you need a backup rapping off a single strand 8mm half rope it works just fine, especially with slings

now lets expand on the hedden .. to give it even more gripping power what you do is stack the coils .

heres is an unstacked hedden ... you can see that we just wrapped upwards and pulled in the end back into the hole



heres us stacking a hedden ... basically we do a few wraps UPWARDS and then wrapped the last 1-2 wraps DOWNWARDS over the upwards wraps, then pulled it into the hole ... what this does is that it cinches the coils down under load





now if you need even more gripping power ... one simply adds a tuck under the hedden before doing the wraps ... heinz prokaskha figured this out 30+ years ago ...





this will grip tighter than some MPers on multipage senseless flame threads ... here it is gripping on a thin string with a 10mm sling under body weight



note that all of these variations only require you to remember a single knot ... the kleimheist


- turn it upside down and its a hedden

- stack the coils and it grips even more

- add a tuck underneath and itll grip even steel wire

- use the same knot with slings or cord

KISS

having a knot that can grip basically anything is super important as its quite likely that your "prussik cord" that you carry will be what you use to escape the belay on a single strand when you need to ... or ascend that single thin strand

now if yr cord is basically close to the same diameter as the rope and is simply too thick ... simply untie it and use a penberthy or blakes hitch (just dont tie the sui-slide variation)

but thats another discussion that involves REI and obama ... mountainproject.com/v/pruss…

;)

Good stuff, bearbreeder.

Never thought to turn the Klemheist over and give it a wrap back across the coils. Gives me something new to test out.

Thank you for taking the time to post that.