"Directional" Fig 8 Knot - acceptable for caving ??

G

Geoff R

New member
I heard that a directional Fig 8 knot is used and accepted in climbing circles. Ive had one indication from an experianced person (couple of years ago) that it is perhaps not accepted in caving  :-\

Has anyone got thoughts in favour or against this knot.

It seems to me to be a perfectly good mid rope knot, part of the Fig 8 family and apparently easy to adjust for load sharing.

thanks 


   


 
Hatstand

Hatstand

New member
Georges Marbach and Bernard Tourte, Authors of Alpine Caving Techniques suggest it as a good knot for a mid line pulling point or somewhere to clip in with a cowstail. They go on to say it shouldn't be used to place a loop at a rebelay.

I'm not sure I fully understand but happened to have to book to hand and needed something to do while I drank my cup of tea!  :coffee:
 
SamT

SamT

Moderator
http://en.wikipedia.org/wiki/In-Line_Figure_8_Loop

"Acceptable for caving" is a very broad statement.

All knots are application specific, if you have a suitable application, then vis a vis, the knot would be suitable for it.

To my mind, its not suitable for re-belays (use fig 8 (or 9) /alpine butterfly, or mid traverse knots (use alpine butterfly).

but in some strange digging, hauling, maybe rescue situation, where you want an anchor point, mid rope, where the direction of pull is going to be back along that piece of rope, (Im thinking some sort of 2:1 haul with the pulley down by the bucket/casualty) then it seems to suit.
 
Brains

Brains

Well-known member
The main argument to my mind would be ease of untying - fig8's are notorious for seizing up solid, whereas alpine/cavers butterflys and bowlines are less prone to this, but may well have other downsides. A 3 way pull on the fig 8 can cause the knot to invert itself, but is unlikely to fail (undo).

Fig 8's were the knot of choice many years ago, the argument being they were so simple to tie and recognise as being correct. Modern rigging (tight traverse lines) tends to be easier with cavers butterfly knots, and all rigging with knots you cab undo afterwards easily with cold wet hands...
 
Cave_Troll

Cave_Troll

Active member
Brains said:
Modern rigging (tight traverse lines) tends to be easier with cavers butterfly knots
Click to expand...

Most people i know use Alpine buterflies. Cavers buterflies (aka "the knot of death") can come undone and rely on the integrity of the loop meaning they can't be used to tie out a worn section of rope.
 
G

Geoff R

New member
I dont really want this thread to get into an Alpine v Cavers butterfly discussion
except to say Im totally "alpine" minded  ;)

But back on topic ...

Problem Im having is that I cant actually see anything wrong with a directional Fig 8 for a situation where the knot is correctly loaded (in the right direction for the knot) and "if" climbers consider it OK, is there a down side that suggests cavers should not use it for rigging that may include Y hangs ?

Im open minded on the matter and would not use it until I fully understand the pros and cons  (y)

 
SamT

SamT

Moderator
How and why would you use it in a y hang  :-\

Also - what exactly to "climbers" (in inverted commas) consider it "OK" (in inverted commas) for??  Tying on to their harness ??.

I've been single and multi pitch climbing for nearly 20 years, and I've never had to use anything other than standard fig 8's (harness and belays),  bowline (big threads), clove hitch (belays)  double fishermans (tying rope slings), overhand (tying two ropes to ab)  and the odd prussik.

I know a multitude of other knots, but never ever had to use them for climbing.

Only additional ones I've used in caving are alpine butterfly, 'bunny ears' fig 8, (which I favour over bowline on the bight) (oh and italian hitch)

so go on - what are we (climbers and cavers)  to consider this knot "OK" for ??
 
G

Geoff R

New member
Sam, it was examples such as this Climbing web site and others that lead me to the perhaps questionable view that climbers may well consider this knot suitable. And my climbing friend apparently uses it.

http://www.chockstone.org/TechTips/F8Knots.htm

Quote :-

In-line Figure Eight ie Directional Fig 8
This knot can be used to anchor the rope. It's perhaps not as commonly used as the aforementioned, figure eight on a bite, but is very handy when equalising anchors

.....The finished knot should be "facing" the direction of the load. You'll note that with a bit of adjustment you can elongate or shrink the protruding loop - very handy when equalising two anchors.

Unquote

hence my question regarding caving use and peoples thoughts on the matter

:coffee:




 
G

Geoff R

New member
This is a photo from that Climbing web site if you follow the link above to equalizing anchors 

InlineEqual1l.JPG
 
Bob Mehew

Bob Mehew

Well-known member
I don't have the time to check myself, but (almost) anyone would be welcomed to spend happy few hours at Hidden Earth 08 with BCA's Rope Test Rig testing a few samples with one end tied with a "directional" Fig 8 and the other with a "standard" Fig 8.  My prediction is that the "directional" will fail in preference to the "standard" since it has only one end coming out of the knot to the load which implies it will be bent much more tightly and hence suffer more stress.  Having said that, the difference in strength between the "directional" and "standard" knots is probably academic.

Outside my experience, I wonder how easy it is to adjust to share the load between the two anchors compared to other knots and how would one go about demonstrating this?

Bob

PS -  I will put in a plug for my lecture on the results of the NCA's Long Term Rope Test at HE this year.
 
francis

francis

New member
I can't imagine that it would be any worse than using an alpine butterfly for the same purpose.

Francis
 
SamT

SamT

Moderator
Ah - I see.

however, why use that when as francis says, an alpine butterfly is equally good, if not better infact.....

Cavers use Y hangs not only for sharing the load, they are also there for 'redundancy' or back up i.e. if one of the anchors fails.

In the photo above, if the left anchor is A and the right B.

If b fails - then the load is transferred to A - leaving the Directional Fig 8 with the all the load pulling across the knot. An alpine butterfly is much better and stable (as far as I'm aware) in this situation. Hence - why cavers tend to use AB knots for Y hangs.

 
Cave_Troll

Cave_Troll

Active member
Sam, this knot is designed that you can load either A or B so if B does fail, you're not really "loading across the knot"
 
Stu

Stu

Active member
Oh goody I get to use one of my favourite sayings...

This knot - solution looking for a problem!

;)
 
Cave_Troll

Cave_Troll

Active member
indeed.
I know this knot and if i came across it in rigging i probably wouldn't mind. However as its not a knot i've tied 500 times it takes me a little while to make sure it comes out the right way up, and i've never bothered to use it.
 
G

Geoff R

New member
stu said:
Oh goody I get to use one of my favourite sayings...

This knot - solution looking for a problem!

;)
Click to expand...


There are obviously situations where alternative knots can be chosen when caving,
each having possible advantages (or disadvantages)

I just find it interesting to compare different "sport" or "work" practices that use different equipment or techniques, as Im always on the look out for improvements or learning situations.

It seems to me that a directional knot like this one (esp one that's a member of the established and easy to recognise Fig 8 family) could have a use in cave rigging, as the "pull" is often only ever going to be in one direction. Its very easy to tie, you just start making the loop in the exact opposite direction to what you finally want. 

Im not advocating its use, just gauging whether anyone knows reasons or problems in relation to its use when caving
 
Hatstand

Hatstand

New member
Geoff R said:
I just find it interesting to compare different "sports" or "work at height" practices that use different equipment or techniques, as Im always on the look out for improvements or learning situations.
Click to expand...

Indeed - which is one of the things that makes this board interesting - it wouldn't be so good if we
1) all agreed on three knots only to be used ever
2) weren't allowed to ever discuss anything more than once, only ever to review old topics  :-\
 
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