/ Whats the point of a daisy chain?
From what i read of the DDM tests, dyneema just doesnt take dynamic loads. So while im unlikely to dynamically load a daisy on a single pitch route, its possible on a multi. According to DMM a fall factor of 0.25 is enough to break one.
So that said, it appears a Purcell prusik is the way to go
Their intended for aid climbing.
Dyneema is perfectly safe if you rig your anchors properly without slack, but as Jacob said that isn't really what they are for.
By break, do they mean the sling itself will break, or just the stitching between the loops. My understanding is that it's the latter, so even if that fails - the stitching pops out - the effect isn't catastrophic. Even if all the loops fail, you'd just be left with a sling.
N.B. There is a danger if you clip the same crab into two loops
I've found daisy chains very useful for belays on sport routes, both single and multi-pitch.
Its a matter of preference. If you don't aid climb there is no 'need' for them at all.
Sorry, perhaps i have misled readers.
what i have is not exactly a daisy - its a series of dyneema loops individually stitched.
i think a daisy is essentially a single loop stitched at each end, then loops have been formed by stitching two sides of the dyneema together.
hopefully that makes more sense.
point being, on my kit, if a loop fails i very quickly hit the deck!
We are gonna need some links. Something like this http://www.grivel.com/products/rock/accessories/56-daisy_chain would not 'break' with a ff 0.25...
this is what i have
this is what i think Chris the tall mentions:
So you have exactly what i linked, which has a load of individual loops rated to 23kn. Don't worry, unless you are Jo Brand you won't be producing 2.3 tons in a 30cm fall. Climb away
I have one of these, they are great... I use it on multi pitch routes, when working single pitch routes, and all the time when im doing rope access work.
Keep it tight, load it up and do not fall on it. the 23kn is not a shock loading.
My wife also uses one to anchor herself when she is belaying me, not that im heavy or anything.....
It's a loading. It can take 23 kN, for 0.1s, 1s, 30s, whatever (although I assume there's a maximum in whatever standard these things comply with).
A fall can generate more than 23 kN, but that's a separate issue.
The point of daisychaining is that you can get more lesbians in a row:)
There is a difference between a static and a dynamic load... my 80kg as a static load is no problem for the sling but if i fell 30cm on to the daisy chain the force I would apply to the sling could be in excess of its 23kn rating.
This is especially relevant in this case as a direct fall on a daisy chain where one end is likely to be attached to a very solid object and the other end to you there is noting in the system to absorb the forces and as dynema does not stretch, this adds up to massive instantaneous loads.
Yes and no. Your static mass of 80kg is a load of about 0.8 kN, your fall as you correctly state could well be in excess of 23 kN. The daisy chain can still take a "shock" load of 23 kN just as easily as it can take a "static" load of 23 kN, the point is you shouldn't exceed that value. Which you could well do by falling on it.
I've owned one for 10 years. Finally used it last week to secure to when I was up a ladder doing some work on the roof. Knew it would come in handy one day!
How far would 80kg have to fall to generate 23kN?
That'd heavily depend how it decelerates. Within this context it depends on the elasticity of the ropes/slings and the fall factor.
With dyneema, which is very non-elastic, you'd either need at the very least a FF2 or a fairly long (1 metre +) FF1
So fairly unlikely to occur with a daisy?
As far as I've seen, and I know nowt about aid climbing, daisy chains are to make you look cool at the wall :D
DMM broke dyneema on a FF1 on a 120cm sling, and failed to break dyneema on a FF1 on a 60cm sling (generating 17 kN in the process). So somewhere between those numbers :)
[ there's the possibility that DMM's test might have slightly overestimated forces due to using an 80kg weight rather than a human body in a harness, which gives a bit more, but it's very difficult to know by how much ]
EDIT: worth bearing in mind that if you experience 17 kN in a fall, you've probably finished climbing for the day, even with an intact safety system :)
To be honest, once you get to those sort of forces the sling breaking is the least of your problems. Your body wouldn't withstand what the sling can.
What is likely is to achieve enough forces to really hurt yourself.
By simply reaching up past the belay to put a piece or something and falling off onto the sling/daisy you can get scary forces going, hence if you use a dyneema sling/daisy you really don't want to be falling onto it, and even with nylon ones which are more common and are a little better you still want to keep the weight on it so as not to risk much of a fall/
I think it was tests for soldiers parachutes that found a 12kN shock load was the maximum load for the human body without serious injuries (I don't know how they define "serious") I can't remember if it was the spine that fails or internal damage. Maybe a combination. It looks like the OSHA limit for a person in a full-body harness is 8kN though this is an old link(https://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=INTERPRETATIONS&p_id=20409)
All very interesting stuff.
A pretty good round up here if that interests you http://www.hse.gov.uk/research/hsl_pdf/2003/hsl03-09.pdf
If you get any where near a 23kN shock load on your body your internal organs are going to get somewhat jumbled.
Dyneema has very little stretch and so slows you to a stop instantaneously and most daisychains are made of dyneema.
Nylon has some stretch and slows you over a longer distance and so reduces the shock loading (All in a DMM video called how to break dyneema. It is long but must be watched to the end for the summary.) A PAS is a series if small interlocked sewn nylon slings, designed for anchoring yourself. (I still like the rope in my anchor system!)
thanks for all responses, great to get some debate going.
After all of this though, wouldn't it be better to use a length of rope - which has more stretch than a daisy - or a purcell prusik?
i seem to recall my daisy (or whatever its actually called) cost me near 60 quid... feels like daylight robbery now :)
Interesting link, thanks!
Before you throw it in the bin, here are three ways you can use it on multi pitch routes that have bolted belays.:
"The daisy chain can still take a "shock" load of 23 kN just as easily as it can take a "static" load of 23 kN"
This isn't quite right...
Under shock loading conditions (ie rapid application of force) significant temperature rises can be generated especially if knots are involved. This is one of the reasons why dynema is less good than nylon for shock loading (because it has a lower melting point) and partially why it is good to be a little cautious when tying knots in slings .
However, for the very short drops the standard test of a rigid 80Kg mass is not particularly relevant to the reality of a climber fall - the reason being is that a climber is not a rigid mass and the time scale of the "shock" is extended as the body deforms which lowers the peak forces. Another way to think of this is the centre of mass of the rigid weight stops very quickly and in a very short distance but the centre of mass climber stops more slowly and over an extended distance that is significant compared with the length of the fall.
Back to the OP's question - a sling is ok to connect to an anchor at a belay but try not to shock load it. I would tie a knot in a sling to shorten it and avoid shock loading without worrying too much.
Try to avoid using a sown daisy chain loop as a belay anchor because the yield strength of the loop stitching is much lower than the yield strength of the sling (2.5KN I think?) and it is possible that when holding belayer and fallen climber it may yield. In this case it will lengthen out to the full sling possible lowering belayer and climber a lot and possibly shock loading the anchors.
A daisy chain made of individual slings like this:
avoids the problem and just counts as a "sling".
Thank you... saved me a lot of typing.....
> thanks for all responses, great to get some debate going.
> After all of this though, wouldn't it be better to use a length of rope - which has more stretch than a daisy ...?
Does it really make much difference? Assume that dyneema doesn't stretch at all and rope stretches about 3%. That means with 30cm sling your getting about 1cm of 'shock absorption' extra. You have far more than that in the harness and your body (thighs & waist). OK, not a rigourous analysis, but to first approximation, the difference between dyneema and rope seems pretty small.
I did not know that (i.e. that the reason for weakness in knots in slings was temperature, rather than geometric effects as it is in rope).
However bear in mind that in the non-knotted situation, DMM achieved shock loads of over 25 kN on a Dyneema sling and didn't break it (although it must have been close!). This strongly suggests that temperature-related weakening of slings under dynamic loads is fairly insignificant - unless, of course, it's knotted. We weren't talking about knots in this thread though.
The moral of all these stories is simple.
a) Connect yourself to the anchor with something robust (rope or sling of any material, not the pockets of a standard daisy) and ideally short.
b) Do not climb above the anchor.
c) Do not allow your connection to develop a length of slack.
If you have a longer connection (whatever it is made of) this lets you break rules b) and c) more easily. As a result I never use a sling of more than 60cm as a cowstail. Even falling the 1.2m onto the sling (if I was stupid enough to climb above the anchor) would be extremely unpleasant and although extremely unlikely to break the sling might very well break the anchor or me.
It's both - I don't know how significant each factor is and I suspect many practical details matter. I also think dyneema slings is stiffer than nylon so might see high peak forces in some loading scenarios.
-I think we'll all agree that in most static uses all slings are very strong.
-I'll think we'll all agree than taking a FF2 on a 120cm sling is a bad idea. Even if the sling survives it is going to hurt the climber and the anchor.
The safety cut-off lies in-between and the key information for those that are uncertain is that slings aren't dynamic so use a dynamic rope where falls will be taken.
Haven't made a chain out if daisies for years. You put on your wrist or gang round neck.
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