Prussik identification?

[Rinseout]

I just know it as a prussik but was wondering which one is it?

George

[woodsy]

french

[Rinseout]

cheers woodsy been using it for years now and never known its proper name

[ion]

It could just be the photograph but that doesn't look tied correctly to me, both ends of the cord loop look to be clipped into the crab... apologies in advance if it is just me misled by the photograph.
Here is one of many good internet references on the 3 common friction knots:
http://www.chockstone.org/TechTips/Prusik.htm

-Ian

[John Kennedy]

It's French if it wraps around the rope, and clips in to the biner.
It's a klemheist if it wraps around the rope, one end goes through the other, and onto the biner.

[garya]

It's a french prussik for sure

Gary A

[magical-steeve]

also, it looks like the prussik loop itself has been tied incorrectly, the ends should be tied together with a double fishermans knot. aswell as being a more secure knot for this application, it also makes the loop more workable.

[MikeB]

I dont recognise it as any of the usually tied prussicks - it's certainly not a French (see Ian's link) - and certainly not a Klemhist or a Bachmann. It almost looks as though the intention might have been to tie it as a Klemheist though. All that said, it looks like it will work ok for a z-drag or other boat rescue use - I'd not want to climb using it myself though.

[Torsten]

It appears to be what they are calling an 'Autoblock' on the site that is linked above...

[garya]

I dont recognise it as any of the usually tied prussicks - it's certainly not a French (see Ian's link) - and certainly not a Klemhist or a Bachmann. It almost looks as though the intention might have been to tie it as a Klemheist though. All that said, it looks like it will work ok for a z-drag or other boat rescue use - I'd not want to climb using it myself though.

Try this link for the french prussik
http://ozultimate.com/canyoning/knots/french_prusik/

Photo In ians link actually shows a Klemheist tied in cord rather that the more usual tape. The text however is a bit misleading does talk about both knots. The main different is how many loops are cliped into the carabiner.

Top and bottom loop clip to carabiner = french

bottom loop passed through bottom loop and then clip to carbiner as a single loop = klemheist

http://en.wikipedia.org/wiki/Klemheist_knot


More worring from the photo at the top of the post is the knot in the loop which has both ends comming the same way so is not using the recommend double fishermans knot. The cord has also been cut without a heat gun and not sealed. On short cords this can result in the core and sheath slipping and serverly impacting on the stregnth of the system. The loop looks a little short to work with and may leave you with little options if you have a thicker rope or need extra wraps if it is not gripping or the rope is icey

http://en.wikipedia.org/wiki/Double_fisherman's_knot


I would bin it and start again with a new loop as it does not look 100 % safe at the moment

Hope this helps

Gary Archer

[Paul Smith]

Its a french prussic, as others have said. Which is also known as an Autoblock, due to the way that it re-grips the rope when you remove the pressure from the top of the knot (which makes it slip!)

Prussics can be tied with an overhand knot as shown in the photo, and don't have to be tied with the more commonly seen double fishermans. The main advantage of the overhand is that it uses less rope/cord/tape than the fishermans and is normally easier to untie, making the cord useful for different tasks.

The Klemheist is for use when you don't want the prussic to slip and you aren't planning on needing to move it. Due to the way that you tie it, the cord bites more aggressively into the rope.

[Rinseout]

just to clarifiy I wrap the loop 5 times round the rope and clip both ends to the crab and have only just made the loop but normally tie with a reef knot not a double fishermans or overhand

[MikeB]

It appears to be what they are calling an 'Autoblock' on the site that is linked above...

Ah - well spotted. I've just learned a new prussick!

just to clarifiy I wrap the loop 5 times round the rope and clip both ends to the crab and have only just made the loop but normally tie with a reef knot not a double fishermans or overhand

Ah! Could I respectfully suggest the double f/mans or the overhand may be rather better than the reef? Which is also known as the "parcel knot" and does have a nasty habit of coming undone - - - and weakens the rope a bit! From here comes this, which seems credible:

"The "double fisherman's" it a much better choice for joining two ropes. A straight rope has a breaking strength: adding tension along the axis will eventually break the rope. When a knot is added to the equation, the strength of the rope decreases.

The double fisherman's decreases the strength of the rope(s) involved to 60-75% of the original strength. Sounds pretty bad; however, the sheet bend decreases the strength of the rope(s) to 48-58%!!

Even worse is the reef knot, aka. the square knot (which looks much like the sheet bend) comes in at 43-47% of the original strength!"

From Wiki, "The name "reef knot" dates from at least 1794 and originates from its common use to reef sails, that is to tie part of the sail down to decrease its effective surface area in strong winds. To release the knot a sailor could collapse it with a pull of one hand; the sail's weight would make the collapsed knot come apart. It is specifically this behavior which makes the knot unsafe for connecting two ropes together" (my underlining).

From my Scouting days I recall the reef knot being described as a good knot for "joining two ropes of equal thickness" - that soon got dumped when I got involved with climbing. It's ok for macrame and parcels!

I'm a fan of the Bachman - the krab makes a really good point to grip especially with cold hands. But I accept you'll need another one to link to the loop.

Mike

[woodsy]

french prissic = autoblock

[Rinseout]

I always thought a reef know tightened under pressure thats why I used correct me if im wrong

[RockRiver]

As a climber I would agree with French Prussik assessment, usually used as an Autobloc or to back-up absails.

That said, I'd never dream of using a Double overhand to Make the prussik loop in the first place for several reasons the one being A double overhand knot reduces the strength of the cord considerably (I beleave by upto 50%).

When putting a Prussic together it is always best to use a double Fisherman's knot then load it to ensure it can't come undone. I Always have at least 2 made-up in my rescue kit.

[Bards]

I always thought a reef know tightened under pressure thats why I used correct me if im wrong

With a good jiggling reefs IMHO can go tighter or come undone - they should be secure when kept under load, but not if the load is relieved. I think

they get their name from supporting 'reefed' sails i.e. sails that hang furled and out of use (hopefully meaning consistent tension) from the yard arm or

whatever that spar that sits across the mast is called. Still beats a 'granny' for general integrity I guess... ;-)

[ion]

Indeed, the auto-blok, my screw up, I never use it or teach it and thus failed utterly to recognize it. Its not a knot I'm wild about, and, especially in the context of kayaking where the primary use of friction knots is in Z-drag/pig rigs it has no redeeming feature I'm aware of, generating substantially less friction than a true Prusik or a Kleimheist.

This rather old but splendid study by a very thorough chap covers friction knots (amongst other things) in different kinds of mediums and is very good reading:
http://www.xmission.com/~tmoyer/testing ... h_Cord.pdf
Somebody else posted a similar British paper on UKRGB the other day testing polypro Palm Throw ropes with friction knots also...with some disappointing friction results I noted there I recall.

As for the flat overhand knot, it actually has a valid application but this is not it, join prusik loops formed from cord with double or triple fisherman's knots...period!
The flat over hand knot is called by the rather amusing name of "The European Death knot" in the US and this webpage covers its use and its issues:
http://www.xmission.com/~tmoyer/testing/EDK.html

[jmmoxon]

Definitely don't use a reef knot. Also never use a figure 8 knot to join ropes (as described in link the loading distorts the knot - this is the true European Death Knot). The situation described of the overhand rolling along the rope only applies when both ends are pulled apart - which is the situation when you join the ropes for an abseil, but not in the pictured French prusik, so as long as you tighten the knot it is perfectly safe, however, Double Fisherman's is preferable as it is easier to undo after loading.

The advantage of the French prusik is that it is the only one that can be slid along the rope when it is under load, by pushing back on the top of the knot.

Mike

[ssmith184]

is very good reading:
http://www.xmission.com/~tmoyer/testing ... h_Cord.pdf

It is indeed!
And the conclusion is interesting too... forget all those fancy new materials, good old Nylon is best all round! :D Cheapskates (like me) rejoice!

[joyjohn]

Try this site for various knots. Good as a teaching resource.
http://www.animatedknots.com/indexrescue.php?LogoImage=LogoGrog.jpg&Website=www.animatedknots.com

[Scots_Charles_River]

Lots of confusion and misinformation on this thread !

Think some training is req'd for some 'rescuers'.

Maybe folk should invest in a one way traxion device or a ropeman (wild country) so they
can't tie the knots wrong.

Nick

SPSA Climbing Qual. held

[jmmoxon]

Starting with:

Dr. Karl Prusik (1896 - 1961) (also spelled Prussik) was an Austrian mountaineer who is known as the inventor of the prusik knot. He died in May 1961 at the age of 65.

The benefit of the knot is that, when weighted, it grips the rope that it is tied around. When the weight is removed, it is free to slide. This enables it to be used in a number of self rescue situations or for ascending a rope.

Prusik served twice as president of the Austrian Alpine Club (OeAV), and is credited with pioneering over 70 new ascents and routes.

The knot is also seen spelled incorrectly as prussic.

[Fatboy]

Interesting that the overhand is (wrongly) called the Euro Death Knot for joining two ab ropes. The overhand with 2ft tails has been pull tested as a strong knot, with the double overhand stronger. The figure 8 joining two is the bad knot. There's an article on UkClimbing (I can't remember how to post links) that covers this, using the pull testing rig at Lyon. Also, it's worth mentioning that loading the knot in the way shown would not cause the failure implied by the article linked to.

I've seen, and used, overhand knots on Prussiks - mainly as a back up abseils. I've understood that they are sufficiently strong (again, back to the UkCLimbing article for approx % TS losses), and stable with a long enough tail, and a pre-tightened knot. They also have the advantage of sitting rather more nicely in the krab when used with a French Prussik.

[neilfarmer]

.....again, back to the UkCLimbing article for approx % TS losses)......

There is enough of reason not to use it as a joining knot, over a double fishermans knot!

Can anyone suggest any reason why we should use an overhand/.../... knot rather than a double fishermans for joining two equal diameter ropes, other than "it is easier to tie/undo/etc" which in relation to the context of the loss in strength becomes invalid?

[Fatboy]

Neil, you've lost me. All knots reduce the strength of the line. If we're still talking about climbing, the overhand knot is taught as a method of joining the ropes for abseiling. It is strong enough, stable enough, quicker to tie and easier to undo than a double fisherman's. It also snags less when being retrieved. In other words it is a better knot to use.

On another note, if the knot slips, or the rope sheath strips before the knot fails, then the knot is fine.

It would also be interesting to see at what load the boat plastic fails relative to the strength of the prussik.

http://www.needlesports.com/advice/abseilknots.htm

[ion]

Also, it's worth mentioning that loading the knot in the way shown would not cause the failure implied by the article linked to.

I've seen, and used, overhand knots on Prusiks - mainly as a back up abseils. I've understood that they are sufficiently strong (again, back to the UkCLimbing article for approx % TS losses), and stable with a long enough tail, and a pre-tightened knot. They also have the advantage of sitting rather more nicely in the krab when used with a French Prussik.

On another note, if the knot slips, or the rope sheath strips before the knot fails, then the knot is fine.
It would also be interesting to see at what load the boat plastic fails relative to the strength of the prussik.

OK, I have to apologize for introducing the flat overhand (EDK) in the climbing context because I think I have confused a very important topic here. This is not a climbing scenario, its a swift water rescue scenario where mechanical advantage is being obtained, possibly with life or death consequences, with the use of a friction knot tied using a loop of knotted accessory cord or tape. In THIS context such a "prusik loop" will be PRE-tied with a double fishermans knot, or possibly a water knot if its tape, and it will be tied that way because quite simply its absolutely the strongest way to have it tied and it needs to be done in advance. In a worst case real world situation (and I do mean real, not fictitious) you and your kayaking buddies will be confronted with one of your group pinned in the water, dead, and increasingly beyond possible resuscitation with every passing second. And you WILL have super human strength for the next 30 minutes, and you WILL pull grab handles clean out of boats, strip the sheath off multiple throw ropes, completely snap prusik loops and utterly destroy your hands in the process. No one will care if you can't undo any knots later, in fact you will throw all the ropes away because they will all be ruined beyond further use.

To suggest this:

Is significantly different to this:

and in any way equivalent in strength to this:

Is quite simply wrong and dangerous when we have people reading this thread genuinely looking to improve there understanding in this context.

As far as the French "prusik" is concerned its my belief/opinion that it provides inferior friction to the Prusik knot tied in cord or the Kleimheist tied in tape, and that this is critical in this application, and that the ability to deliberately release under load is irrelevant also in this context. I think that is well quantified by both the study I posted and also this PYB study http://www.google.com/url?sa=t&source=w ... l3lbR3eMLQ somebody else posted on UKRGB recently. I did actually go back and try this again tonight with my actual wet gear fresh off the river, just to see if I could find merit that I had failed to in the past. I came away utterly convinced I will continue to tie a classic Prusik every time in this situation with my cord loops. I would love to see a well done quantitative study of devices such as the Petzl Tibloc in this application, where its a max load rather than body load and floating static line scenario, just to see if there is something better. I say they are unproven in this application until then.

Sorry to be so bloody minded and adamant on this issue, I'd happily discuss the merits of the EDK in the climbing context in another time and place.

[TheKrikkitWars]

Ion, the main advantage of the Autobloc prussic in an water operations context is that when used as a progress capture device with a prussic minding pulley, it can be left to its own devices; the more agressive prussics often require operator intervention to "unlock" for rope to be taken in.

One thing I'm unclear on, I've always been taught to set up a french prussik in the same way as a larks foot knot (or cow hitch) but with 4 or more loops, some people seem to be implying that I should be clipping into both loops of the larks foot, which I don't understand.

[Ian W]

Wow!

Reading this thread there is some really scary information /mis -information!

Just to cover a few points.
Mechanical devices such as Tiblocs, Ropemen etc are great devices in some situations but need to be understood and used correctly (i.e if they are placed the wrong way round in a panic situation they will not work). Also the moving parts in a Ropeman would be liable to corrode if left in b.aids/boats for years on end.
I would stay stick with Prussiks and know how to use them.

As for what knot to tie them with well I use a mixture of Double fisherman's on some plus some with overhand knot. I am confident both work and have advantages.

TheKrikkitWars you are confusing the French Prussik with the Classic - read the thread towards the start and you will see the difference.

If you have any doubt or are confused about this thread get some professional training, don't rely on internet 'experts'!!

Ian W

[Adrian Shanahan]

Hey Josh,

What you are describing is not actually a French prussik, to be honest it makes no differance what you call them once its,

Easy to tie

East to un-tie

Fit for the intended application.


There are a bunch of differant types of purssiks which have differant pro's and con's.

So this is what you are doing, a basic prussik knot.






And what people refer to as a "French Prussik"






Adrian