Dyneema shock/safety cords

[topcat]

My only note is that its possible to twist my cowstail carabiner and force it to unclip from the maillon.  I don't like the idea of switching to a locking carabiner on my cowstail so I guess its just a question of likelihood of this happening/ risk.

A screw gate not screwed up is a snap.  I've come across this aversion to cowstail screw gates before, but don't understand it.  Use it as a snap if you must, but at least if you feel the need of the extra security, it is there for you.  Assuming you maintain it of course.

 

[Fulk]

Agreed, topcat; I've always used screwgates on my cow's tails; most of the time the don't get screwed up, but on rare occasions the extra security they afford makes it worthwhile (in my eyes).

 

[GT]

As previously said, for me Marks nailed this.

I really question why people use dynamic rope to their hand jammer, any dynamic loading on a toothed jammer is likely to severely damage the rope.

In my mind putting a section of dynamic rope into the system gives people a false sense of security in that the dynamic properties of the rope will reduce a load on the jammer in the event of a fall and may protect the rope. In my (simple!) mind it's easier to park that idea and use 5-6mm accessory cord and not even consider using a toothed jammer in a situation that could result in dynamic loading.

 

[ah147]

Did you stack it in Cresta run, P8?

No. The Nose on El Cap.


Sent from my iPhone using Tapatalk

 

[IanWalker]

Those of you using your long cowstail as your safety link to your hand ascender..

1. Hows the footloop attached to the ascender; maillon, carabiner or just a knot?
2. Do you have a locking carabiner on your cowstail?
3. When you clip your carabiner into the ascender, do you put it through the "other" carabiner or maillon or into the ascender itself?

I ask as I was playing about with this the other week and made a footloop out of some tape I had lying about with a maillon connecting it to the ascender.

My only note is that its possible to twist my cowstail carabiner and force it to unclip from the maillon.  I don't like the idea of switching to a locking carabiner on my cowstail so I guess its just a question of likelihood of this happening/ risk.

Since you ask... standard pair of inglesport cowstails tied with a fig-8 and two snapgate keynose crabs each on a double fishermans knot with long tails. either crab clipped to main lower eyehole on old-style petzl basic jammer (or upper pair of holes and also around the rope for sloping lines). separate footloop tied in 25mm tubular tape with small overhand loop at top connected to smallest lower hole on petzl basic using a small steel delta maillon. the small deta maillon is not part of the fall load path. the cowstail crab clips the jammer directly, and not via any other crab or maillon partly for the reason you describe.

clearly as this thread has highlighted my chosen kit setup has positives and negatives and like everything else it is a compromise of many factors. just happens that its a compromise that im happy with.

 

[IanWalker]

I really question why people use dynamic rope to their hand jammer, any dynamic loading on a toothed jammer is likely to severely damage the rope.

since you really question it i will form a response to this and your other points. i use dynamic rope on my hand jammer to reduce the dynamic loading on my toothed jammer compared to static rope, and thereby reduce the liklihood of rope damage or parting in an unplanned fall onto that jammer/rope combo. i understand there is a hazard of damaging the rope and i choose an accepted method to reduce that loading. i do not believe that 'any' dynamic loading is likely to severely damage the rope as you say. if that were the case there would be a lot more stories of broken ropes but this seems to be exceptionally rare.

In my mind putting a section of dynamic rope into the system gives people a false sense of security in that the dynamic properties of the rope will reduce a load on the jammer in the event of a fall and may protect the rope.

studies shared above show that dynamic rope *does* reduce the load in the event of a fall. it makes sense to me that this would help protect the rope. by the way i am not advocating using jammers in a planned way to catch big falls and like most people i really don't want to fall onto a jammer. but, slips on to jammers do happen in the real world and there is a very easy way of mitigating some of that risk with the method described. i don't think its a false sense of security but a considered approach to mitigating foreseeable hazards.

In my (simple!) mind it's easier to park that idea and use 5-6mm accessory cord and not even consider using a toothed jammer in a situation that could result in dynamic loading.

it seems you choose to dismiss the manufacturers instructions and put greater reliance on your own vigilance with an accepted increase in risk of human error that your non-standard use requires. thats a trade off you choose to make and i'm not forcing you to adopt any given system.

but there are foreseeable circumstances of dynamic loading onto a toothed jammer with the conventional setup that are somewhat outside of the users control. e.g. imagine prussiking up towards a bolt rebelay and when nearly there, the bolt fails, dropping you until the backup bolt takes the weight. could that occur with your setup and do you use toothed jammers? i believe it's worth considering.

further, imagine ascending a sloping traverse line that might be quite long. in that situation i would consider using a jammer on the sloping line with the aim of arresting any fall if i slip. would you consider that? likely the alternative would be clip the sloping traverse line with a cowstail and accept a zipline fall down to the next traverse anchor, and whatever uncomfortable landing might wait there. which is safer?

all the above assumes 'dynamic' load to mean any sudden loading of a rope that was previously slack, usually in an unplanned way. if you have a different understanding of dynamic fall to me then please share.

 

[Fulk]

GT:

In my (simple!) mind it's easier to park that idea and use 5-6mm accessory cord and not even consider using a toothed jammer in a situation that could result in dynamic loading.

So would you like to describe the set-up you use for prusiking?

 

[IanWalker]

In my mind putting a section of dynamic rope into the system gives people a false sense of security in that the dynamic properties of the rope will reduce a load on the jammer in the event of a fall and may protect the rope.

studies shared above show that dynamic rope *does* reduce the load in the event of a fall. it makes sense to me that this would help protect the rope. by the way i am not advocating using jammers in a planned way to catch big falls and like most people i really don't want to fall onto a jammer. but, slips on to jammers do happen in the real world and there is a very easy way of mitigating some of that risk with the method described. i don't think its a false sense of security but a considered approach to mitigating foreseeable hazards.

this aspect of my recent post:- "...a considered approach to mitigating foreseeable hazards" is too general and i would prefer to be read "a considered approach to mitigating a foreseeable hazard"

i think it is important to explicitly qualify this as being a specific mitigation to the consequence of a fall onto the handjammer safety cord (i.e. keeping us on the topic raised by the OP and the issue i was responding to in GT's post).

more generally this thread has prompted me to think again and in great detail about how my kit is assembled and used. other people's input has been very useful to this. cheers everyone 

 

[andrewmcleod]

As previously said, for me Marks nailed this.

I really question why people use dynamic rope to their hand jammer, any dynamic loading on a toothed jammer is likely to severely damage the rope.

In my mind putting a section of dynamic rope into the system gives people a false sense of security in that the dynamic properties of the rope will reduce a load on the jammer in the event of a fall and may protect the rope. In my (simple!) mind it's easier to park that idea and use 5-6mm accessory cord and not even consider using a toothed jammer in a situation that could result in dynamic loading.

To some degree I agree with you (and used to use a bit of the Beal 5.5mm dyneema core stuff for my 'safety' cord. Any fall which is more than a few metres below an anchor is fine anyway as the rope will take the load. But tests show that a FF2 onto cowstails tied with dynamic rope tied with appropriate knots (barrel knots and Fig 8) come in around the 6kN mark, while sewn lanyards are terrible and using static rope bumps the load up slightly. 4-6kN is about also the rope-tearing threshold. So I think it's not completely unreasonable to say the following:
1) It is probably very difficult to tear a sheath taking a FF1 fall onto an ascender connected by a dynamic rope cowstail
2) This is probably not true for a truly static lanyard.

So possibly it's not an entirely false sense of security - I now use a standard dynamic safety cord. Falling onto an ascender remains a bad idea.

 

[nobrotson]

I switched to using my long cowstail as an attachment point for my hand jammer some time ago and have not looked back since. This is combined with an adjustable petzl dyneema footloop. When not ascending or rigging I keep my ascending gear on a gear loop out of the way. I have never dropped a hand jammer despite being prone to this kind of fecklessness. this reduces clutter on my harness and saves weight: perfect.

Regarding falling onto jammers: early in my alpine caving career in Austria I was rigging a traverse line with my hand jammer (at the time on a separate static safety cord) and a short cowstail clipped into a progression knot as protection. I was crossing a big rock bridge and as I crossed it collapsed, leading me to swing around 5m into the opposing wall. the hand jammer was not hanging loose, and consequently did not take a big force (less than ff1). the short cowstail did not come tight. Thus the jammer was the only thing protecting me at the time. As long as you use your jammers properly (ie without the chance of a dynamic shock load) then I see no reason why a jammer shouldn't be used as protection in these instances rather than just an aid to progression as seems to have been suggested. Obviously its a good idea to back it up. However, if the jammer had damaged the rope in my case then the back-up would have been rendered void anyway as the damaged section of rope would have been above the back-up. Something to think about.

This leads onto another point: what do people think is the best way of protecting a traverse such as this without using a descender, which is sub-optimal in a number of ways (takes ages, uses a lot of excess rope, clumsy)? If bolting a new traverse (no P bolts to clip into) which is very exposed (ie few useful foot and handholds), I generally use my jammer on my short cowstail as a positioning tool backed up by my long cowstail (screwgate) clipped to a knot above the jammer (to avoid the situation I outlined above). If there are truly no real holds, I would use a skyhook for positioning, but then this has to go on a cowstail or other attachment point. this is where carrying an extra attachment point comes in handy. Obviously you can clip the previous bolt and just reach out sideways from there, but then you would end up using a shit load of bolts on a traverse line, especially if you have short arms like me.

 

[Tommy]

This leads onto another point: what do people think is the best way of protecting a traverse such as this without using a descender, which is sub-optimal in a number of ways (takes ages, uses a lot of excess rope, clumsy)? If bolting a new traverse (no P bolts to clip into) which is very exposed (ie few useful foot and handholds), I generally use my jammer on my short cowstail as a positioning tool backed up by my long cowstail (screwgate) clipped to a knot above the jammer (to avoid the situation I outlined above). If there are truly no real holds, I would use a skyhook for positioning, but then this has to go on a cowstail or other attachment point. this is where carrying an extra attachment point comes in handy. Obviously you can clip the previous bolt and just reach out sideways from there, but then you would end up using a shit load of bolts on a traverse line, especially if you have short arms like me.

A non-toothed jammer like a Shunt/Microcender?
Fig-8 descender as it's smoother?
C-rigged simple?
A running clove hitch?

 

[nobrotson]

the fig8 and clove hitch could put twists in the rope, so not ideal. Locking off a fig8 is a bit of a faff as well so I would probably not use that. I used to try the clove hitch and found it faffy and inconvenient as well. shunt is quite a nice looking bit of kit that I don't have and have never used, though I am not sure how much I would use it in caving outside of this purpose (quite a good backup option I guess). C rig could work quite well, never considered that. I think its quite good to use progression knots so that the derigger has a bit more protection as well, and it means you don't have to faff adjusting the rope lengths too much as you may do if using a descender.

 

[Mark Wright]

I use a Shunt for vertical and horizontal aid climbing unless there is somebody there to offer me a belay through, e.g. a GriGri.

The only issue with a Shunt is if you grab it or grab the rope above it if you did take a fall. Your natural reaction in a fall is to grab whatever is in front of you. I know, I've done it.

Its unlikely you would have much of a use for it outside of this application though.

A cheeper alternative is to simply use some type of Prussik knot.

I've also used a half loaded Stop which saves carrying anything else and this has worked OK for me on a number of occasions and still gives you the auto-lock facility.

Mark

 

[nobrotson]

I use a Shunt for vertical and horizontal aid climbing unless there is somebody there to offer me a belay through, e.g. a GriGri.

The only issue with a Shunt is if you grab it or grab the rope above it if you did take a fall. Your natural reaction in a fall is to grab whatever is in front of you. I know, I've done it.

Its unlikely you would have much of a use for it outside of this application though.

A cheeper alternative is to simply use some type of Prussik knot.

I've also used a half loaded Stop which saves carrying anything else and this has worked OK for me on a number of occasions and still gives you the auto-lock facility.

Mark

Never considered the idea of getting a belay but the concept appeals to me especially considering the nature of one of the leads we hope to pursue in Austria this year. Should have been obvious.

If you were to use a prussik knot is there a particular material that you would recommend using for the prussik knot, bearing in mind that you said accessory cord shouldn't take falls (which I agree with). I have used a 60cm 8mm dyneema sling as a prussik loop before which seemed to work quite well but would the dyneema react well to being fallen onto?

 

[Mark Wright]

Having a belay is probably the safest option and could be done through either a fully or half loaded Stop depending on the rope diameter and stiffness.

I would probably use something like 5mm or 6mm accessory cord for the Prussik knot. You don't have to worry about the energy absorbency as this comes through the Prussik knot slipping should there be a fall.

Mark

 

[nobrotson]

I would probably use something like 5mm or 6mm accessory cord for the Prussik knot. You don't have to worry about the energy absorbency as this comes through the Prussik knot slipping should there be a fall.

Mark

cheers, I thought as much but had never considered the material before so thought I would ask.

 

[Mark Wright]

Tree surgeons and rope rescue teams use them all the time, especially in the US.

Heres a link to one of the rope rescue equipment manufacturers with information on prusik cord.

https://www.cmcpro.com/equipment/prusik-cord-load-release-hitch-cord/#learn_more


This one shows prusik knots used in a rescue system (top right of the block of photographs on the second to last page)

https://www.cmcpro.com

The relatively low breaking strengths might be a bit misleading. When they are tied in a loop they are twice as strong and because of the number of times they are wrapped around the main rope you don't really need to worry about any loss in strength because of the knot or the lark's foot loop as the dynamic fall slippage would only ever allow a minimum of loading.

I used prusik knots over 20 years ago on the Humber Bridge. We had them wrapped around the metal handrails to stop a potentially very high FF5 fall factor. They were replaced regularly. 

Mark

 

[Mark Wright]

I've just noticed Starless River sell a complete SRT kit aimed at beginners and it has an 8mm accessory cord security lanyard and foot loop combination.

Mark

 

[Wardy]

At SpanSet we sell a variation on a lifting sling that is tested / used for choking round vertical scaffold tubes as an anchor point for fall protection.
Effectively it is a prusik used on a metal tube so locks up well, but can be slid into position.
Again whilst it is not the strongest use of the sling (to counteract this we use an over spec sling) it offers a really high level of safety as it can be placed high reducing the fall potential - Showing that whilst equipment choice is important, understanding how to get the most from the equipment you have is possibly even more important.
Which is why training for beginners is vital and discussions like this on a forum are great.
Wardy

 

[GT]

Now that things have calmed down with work I wanted to re-visit this. After the original post, and my reply and subsequent questions, rather than answering with just my personal opinion I wanted to reply with a little more substance.

So I set about running a few drop tests with a load cell and a variety of different cords between a jammer and test mass. I've had some interesting results so far, which I'll happily share in due course, however wanted to complete a broader set of test including the Petzl advocated taped lanyard (Spelengyca), 8mm semi-static (which is actually rated as an accessory cord) and the original posts question on dyneema shock cord.

I've ordered and received some of this stuff (https://www.roostersailing.com/pd/Rooster-Dyneema-Shock-Cord_106711.htm) but  the thickest I've found is 6mm with a mean breaking load of 240kg; so basically not strong enough!

So back at the original post; what shock cord did you envisage using? Could you get me a link to the cord you were thinking of using? I should get some time to re-visit and finish the testing next week and get something written up...