What diameter prussic cord

[simonsays]

Apologies is this has been asked before, tried a search but couldn't find an answer.

I'm looking to tap the combined wisdom of the forum....

Bearing in mind most of the srt I've done so far has been on 10mm rope what diamter cord do you think makes the best prussic loops? I have some 5mm (bought to attach to my tackle sack) that has a breaking strain of 500kg but it looks awfully thin.... Would this be any use or do I need to go shopping?

Cheers,

          Simon

 

[langcliffe]

5mm to 6mm is normally recommended. Anything thicker doesn't grip so well.

Keep away from the pies and half a ton breaking strain should suffice...

 

[Benfool]

why not take a spare jammer or tibloc instead of prussic loops? Or are you using them for some other reason other than a backup jammer?

However to answer the question, I guess 5mm will most likely be absolutely fine!

 

[cap n chris]

why not take a spare jammer or tibloc instead

What Benfool said ^^^

Especially in light of this, coming soon:....

http://www.petzl.com/en/outdoor/new-2013-products/caving

 

[Benfool]

or even a kong duck, cos it looks really cool!
http://www.starlessriver.com/shop/ascenders/kong_duck

 

[NOZ]

If you really want prussik cord - you can get it from arborist suppliers http://www.teufelberger.com/en/products/arboriculture/tools/sirius-loop.html
It is more flexible than the equivalent diameter low stretch cord.
You can achieve a similar thing by removing a couple of core strands from caving rope.

 

[pwhole]

In my big book of knots, it states that prussik cords should ideally be half the diameter of the rope being climbed up, so looks like 5mm is ideal. I guess taking a fall on two prussik cords would be very small, and so 500kg BS will probably be fine, even with the knots.

Might be a bit nasty on the wrists though...

 

[langcliffe]

If you really want prussik cord - you can get it from arborist suppliers http://www.teufelberger.com/en/products/arboriculture/tools/sirius-loop.html
It is more flexible than the equivalent diameter low stretch cord.

10mm sounds to thick for me. Even if it is flexible and grips the rope, it seems to be unnecessarily bulky.

 

[Fulk]

IMHO, and having messed extensively with prusik knots of diverse types in lots of different types of rope / cord / tape ? and having, indeed, climbed out of Eldon Hole using knots ? I'd say forget it; stick to mechanical jammers.

 

[cap n chris]

What Fulk says, but avoid these:

http://www.thebmc.co.uk/wild-country-ropeman-3-recall

 

[paul]

IMHO, and having messed extensively with prusik knots of diverse types in lots of different types of rope / cord / tape ? and having, indeed, climbed out of Eldon Hole using knots ? I'd say forget it; stick to mechanical jammers.

You don't have to use Prusik Knots: other alternatives (Klemheist, French Prusik, etc) ar a lot easier to use.

For an example (using a very quick Google search) see http://www.needlesports.com/catalogue/content.aspx?con_id=11ef054b-4ec4-4f03-8acc-9c9e00a5f8ae#prus.

 

[Fulk]

Klemheist, French Prusik, etc

That's what I meant by diverse different types.

 

[paul]

Klemheist, French Prusik, etc

That's what I meant by diverse different types.

Thought so. I added the above for maybe others to gain a bit of knowledge.

You're right about mechanical ascenders being superior when ascending a pitch using SRT but for the occasions when the excrement hits the fan and you need plan 'B' and haven't got a functioning mechanical device available, carrying a Prusik Loop (I have one which i use to carry my knife) and knowing a few useful knots can help.

Carrying a Prusik Loop as a back up is probably a hang over from my climbing days.

 

[Benfool]

Around your neck, with the knife, why dont you also have a tibloc? Seriously, these days, with the development of very small emergency jammers there is absolutely no need to carry something which you have specifically designed as a prussic loop. Indeed this is a outdated practice from moutineering and climbing and does not really apply to caving.

Anyway, if shit hit the fan, you have the rest of your SRT kit to play with. A pantin, or even a decender could easilly be turned into a backup jammer if needed. A prussic loop certainly wouldn't be my plan B, maybe Z......

 

[cap n chris]

When caving don't wear anything around your neck that isn't easily snappable. Abseiling with a cord around your neck is a really bad idea.

 

[SamT]

there is absolutely no need to carry something which you have specifically designed as a prussic loop.

Versatility (and the knowledge/imagination to utilise it) is the name of the game.  Why carry extra kit with only one purpose when the things your already carrying will probably suffice and have multiple purposes.

drawstrings for tackle bags = prussic loops/thread belays/hand lines/deviations plus many many more that I haven't thought of yet.

Never really thought about the whole round the neck thing.  Its never bothered me (knife on 4 mil cord), but I may re-consider.. :-\

where do you carry your knife chris ??

 

[NOZ]

500kg ~5kN breaking load will be doubled if used as a loop. And then reduced somewhat by the knot.
This will still leave it comfortably in excess of the 4.5kN at which a Petzl ascender will cut the sheath.
However mechanical ascenders are much faster and more user friendly for caving unless you practice with prusiks a lot and use additional equipment and/or techniques (e.g. Prusik minding pulleys, footlocking).
Gripping knot systems are very useful - if you use the appropriate gripping knot for all sorts of things though (e.g. Fast descent of a doubled rope in a canyoneering rescue).

If you really want prussik cord - you can get it from arborist suppliers http://www.teufelberger.com/en/products/arboriculture/tools/sirius-loop.html
It is more flexible than the equivalent diameter low stretch cord.

10mm sounds to thick for me. Even if it is flexible and grips the rope, it seems to be unnecessarily bulky.

This was purely an example and is available in other diameters - it was the first hit in my search.

When caving don't wear anything around your neck that isn't easily snappable. Abseiling with a cord around your neck is a really bad idea.

Why not? I carry keys on a cord around my neck and sometimes a backup light on an elastic strap, and so do lots of people I know. If it is inside your oversuit and undersuit I do not see the problem - and have never heard of anybody having a problem.
See Sam ^^^ as well

 

[cap n chris]

where do you carry your knife chris ??

In me arm pocket with me traxion.

 

[TheBitterEnd]

500kg ~5kN breaking load will be doubled if used as a loop.

Does it really count as double? Consider a loop clipped to a krab, at the point where the cord passes through the krab there is only one strand of rope.

I guess 500kg is enough though, without any doubling

 

[langcliffe]

If you really want prussik cord - you can get it from arborist suppliers http://www.teufelberger.com/en/products/arboriculture/tools/sirius-loop.html
It is more flexible than the equivalent diameter low stretch cord.

10mm sounds to thick for me. Even if it is flexible and grips the rope, it seems to be unnecessarily bulky.

This was purely an example and is available in other diameters - it was the first hit in my search.

With respect, Noz - I did check the technical specification of the Sirius Loop before posting, and according to the manufacturer, although it is available in various lengths,  it is only available in 10mm diameter.