UKC

Apologies if there's already a thread about this; I haven't been able to find one.

Im wondering what is the best prussik knot to use for abseiling, and what is/are the best to use for ascending.

I am aware of four kinds of prussik knot, which I define as follows:
Prussik: cord looped around rope, with each loop inside the previous one. Final (inside) tail threaded through first (outside) tail and clipped to load.
Klemheist/french prussik: same, except each loop below the previous one, with last (bottom) tail threaded through first (top) tail and clipped to load.
Autoblock: Same as klemheist, except bottom tail not threaded through top tail. Instead both tails clipped to load.
Name unknown: First tail is girth hitched to load before wrapping like klemheist, clipping last tail to load.


I understand there are differences in how people refer to these knots, but at least for the first three if you could use the same ones I have it will ease understanding.

Which knot is better for which purpose? Why?
Thanks,
Conor

In reply to Conor1:

The principal difference between a standard prussik and a french prussik is that the latter can be released whilst under load (by pulling down on the knot itself) whilst the former can't (when tied using the right cord onto a suitable rope). For this reason I always use, and would always recommend using, a standard prussik for the upper of two knots (the one attached to our belay loop) when ascending a rope.

French prussiks and autoblocs have the bonus of being easier to release, either when making upward progress or releasing a stalled absiel, after being loaded and for this reason I use french prussik when protecting an ab and on the lower knot (foot loop) when ascending a fixed rope.

Your probably already aware of this, but as an aside it is a very bad idea to tie any kind of prussik (typically a klemheist) using a dyneema sling. They have very low friction and as such offer bugger all grip.


Hope this helps,

Luke

In reply to lrandall:

just one point - the Klemheist and it's variation, the Kreuzklem are the only ones you can tie with a tape (or dyneema) sling - have done this once when bust ribs made it difficult to twist round to unclip my prusiks (easier to unclip a sling from around my chest) and it seems to work ok

also in the op - fwiw the klemheist and the french prusik are different knots - I think what you refer to as an autobloc is actually a french prusik

In reply to Conor1:
I use the French Prussik/Autoblock for ab as it is quick to tie/untie and easy to relese etc.

In reply to Conor1:
I use the Klemheist for abbing.

In reply to Conor1:

French prussik to ab. works well.

In reply to lrandall:

Thanks luke, this is the kind of info I was looking for.
I still don't quite understand the relationship between ease of releasing and the position in the ascending scenario, but perhaps it will become apparent when I try it out.
I can certainly see why you would use the easier to release in abseiling. Thanks.

Do I take it from your post that there's not much difference in use between french prussiks and autoblocs in abbing? Anyone have any thoughts on this? Or on the 4th type, which I've heard referred to as the best for abbing but with no explanation as to why.

In reply to Conor1:

A french prusik and an autobloc are the same thing. (Not the same as a klemheist.) You have your terminology a bit mixed up.


The 4th type you refer to seems also to be a french prusik to me, it just has one end captive. I haven't heard of it before, but if its recommended for abseiling I'd guess that's just because you can't accidentally drop it.

In reply to Conor1:

I would always use a standard prussik for the upper knot (attached to belay loop) when ascending a rope as it is this which is stopping you from sliding down the rope into oblivion, whilst the lower knot (attached to foot-loop) is just there to aid changing body position. As such the use of a more reliable grabbing knot (you won't end up sliding down your ropes should you grab and pull on it whilst standing up in your foot-loop) offsets the faff of releasing it! Have a go at ascending a fixed rope with prussiks and you'll soon see what I mean.

As is pointed out in some of the other posts, there is some confusion regarding your terminology. To thorugh my pennys worth in:

what you refer to as a Klemheist/french prussik, I think is actually a Klemheist and is principally used when using a sling instead of a prussik loop (can't say why for certain, but would guess it has something to do with the gripping abilities of the different profiles of the material).

what you describe as an autobloc is aka a french prussik.

The forth not you describe I have not previously come across, but will now have a play with (the not easily dropped suggestion makes good sense).

Whilst your looking into grabbing knots, search online for pictures of a Bachman knot. You'll see its advantages when ascending ropes but be advised it only works effectively on two strands of rope and is more easily released (in either direction!) then any of the aforementioned knots.


Have fun finding your own preference

Luke

French prussik - an autobloc, can be released while under load - so usefull for backing up an abseil and self rescue scenarios. I also use this for my foot sling while ascending a rope.

Kleimheist - different from above, hard/impossible to release under load. I use it as my top prussik attatched to my harness when prussiking (easier to slide up than the original prussik)

Original prussik - like kleimheist but harder to release when it is unloaded

Bachman - a kleimhiest with a biner integrated into it - quite slippy if not done well.

Only the kleimheist can be tied with a sling

In reply to The Rorster: should have said - when prussiking up a rope ALWAYS BACK YOURSELF UP with a clove hitch clipped to a biner on your belay loop

In reply to Conor1:

Well Conor, there's some excellent info there, but there's also a bit of mis-information... I'll try not to annoy you as I did on the other thread.

A French prussik, autobloc and Machard are the same thing. (Autobloc is a strange name, as all the knots you mention will 'auto-block'), but that's the name we have given it, probably due to the fact it's the best one to use to protect an abseil, as it can be easily released under load. It can also be used as EITHER of the knots when ascending. The argument against it, used above - that it will release if you try to pull up on it is understandable, but in fact, when putting your weight on the foot loop when ascending, you tend to make a couple of pulls on the rope and not on the prussik, so in fact makes no difference and is much easier to release to slide up. It's not altogether true that it's the knot attached to your harness that is stopping you sliding to oblivion as you should always tie in to the rope at regular intervals, so that argument against it isn't valid. It's the easiest to tie and can also be tied with a sling, despite someone saying otherwise. It will do everything the others will and more. It also has uses in other situations such as hoisting.

A klemheist shouldn't be used to protect an abseil as you won't be able to release it should you let it lock. You can certainly use it to ascend - both foot and harness, but it's more difficult to release.

A classic Prussik knot is very much superseded by the above two. It's more fiddly to tie and must be tied very neatly to make it work. It will not release under load. Forget it, other than in an historical context!

A Bachman has similar qualities to a French prussik in that it will release under load, but it's more fiddly to tie and requires an extra karabiner. If you are tempted to try one, remember that the krab is NOT a handle like a Jumar. If you pull up on it, it will release and drop you.

I don't really understand your description of the other knot...

In reply to jon:
As usual Gary Storrick can tell you more than you ever realistically wanted to know about such exiting things! http://storrick.cnchost.com/VerticalDevicesPage/AscenderDevices.shtml

In reply to jon:
Hey jon thanks for the info. Its a lot less to remember if I can just use the autobloc for everything. Although I would be anxious about grabbing the top prussik accidently while ascending, so I may try out the klemheist and see how difficult it is to release to get a better idea of the trade-off. Thanks for your input.

In reply to jimtitt:
Wow. That was way more than I wanted to know.
I even read the linked in article explaining why he wouldn't use an autobloc for abseiling. Which essentially stated over and over and over again the problem of grabbing the knot in panic and thus releasing it.

Interestingly (or not), he defines a french prussik as something different to an autobloc or a klemheist.