Great video about strength of nylon vs. dyneema

This may have been posted before, but I don't think it has. One of my coworkers sent me a link to this video. I found it extremely informative and gave me a lot to think about without being entirely dull.

dmmclimbing.com/video.asp?id=5

Great video, right when you think you're safe, and clip into the belay with a sling, partner takes you off belay; a slip and fall and that little bit of slack in the sling can be deadly.

Interesting how a knot helps Nylon and hurts Dyneema.

Ross wrote:Great video, right when you think you're safe, and clip into the belay with a sling, partner takes you off belay; a slip and fall and that little bit of slack in the sling can be deadly. Interesting how a knot helps Nylon and hurts Dyneema.

That's why I usually wait until my partner has weighted the anchors or is in a secure place before taking them off a belay.

I suspect that the "little bit of slack" would be deadly/very painful even if the slings did not fail. If they slings held, the full force would be transferred onto your body.

Evan

I must have missed it, great video thanks for posting.

Why don't people use nylon runners/slings for gear/quickdraw extensions etc if it is stronger at taking dynamic falls than dyneema? After having seen this, I would that that I would be building my future trad rack with nylon slings?

Will Bland wrote:

Why don't people use nylon runners/slings for gear/quickdraw extensions etc if it is stronger at taking dynamic falls than dyneema? After having seen this, I would that that I would be building my future trad rack with nylon slings?

They are equally strong and just fine for Alpine draws because the dynamic rope is still in the system, which is absorbing most of the force.  If you're using them to anchor in, there is nothing dynamic in the system, which is why they are dangerous.  Dyneema and nylon are both fine for draws, the pros being dyneema is lighter and don't absorb water, but nylon is more durable and will last longer at the expense of weight.

Will Bland wrote:

Why don't people use nylon runners/slings for gear/quickdraw extensions etc if it is stronger at taking dynamic falls than dyneema? After having seen this, I would that that I would be building my future trad rack with nylon slings?

Both slings are rated at 22kn, so they are equally strong. The video and article do a good job of explaining the pros/cons of both materials. 

bkozak wrote:

They are equally strong and just fine for Alpine draws because the dynamic rope is still in the system, which is absorbing most of the force.  If you're using them to anchor in, there is nothing dynamic in the system, which is why they are dangerous.  Dyneema and nylon are both fine for draws, the pros being dyneema is lighter and don't absorb water, but nylon is more durable and will last longer at the expense of weight.

Ah, I see with the dynamic rope in the system. So really, using a nylon runner as a PAS would make more sense than the dyneema loops that are the more conventional PAS?

Very good video.  Thanks for sharing!

Will Bland wrote:

Ah, I see with the dynamic rope in the system. So really, using a nylon runner as a PAS would make more sense than the dyneema loops that are the more conventional PAS?

Yes it would.

In fact even better would be if you had a more dynamic PAS, such as self making a chain of cordelette loops, especially if it was dynamic cordelette.

Better yet, a Purcell prusik, of cordelette for a continuously adjustable, dynamically energy absorbing PAS. (If you fall on it, forces can be as low as HALF the equivalent impact as on dyneema, because the prusik will slip, absorbing energy and spreading the force over more time)

Will Bland wrote:

.... So really, using a nylon runner as a PAS would make more sense than the dyneema loops that are the more conventional PAS?

No, because if you are using the PAS correctly there is never any way that you could take a fall onto it.  The only real take away from the video is to use your PAS correctly sot that you don't fall directly onto it.

Ken Noyce wrote:

No, because if you are using the PAS correctly there is never any way that you could take a fall onto it.  The only real take away from the video is to use your PAS correctly sot that you don't fall directly onto it.

Bad situations happen though. Sometimes you need to reach high to an chor that is high above the ledge or you want to place a piece of gear or something. Sometimes people brain fart. Sometimes you trip on your super awesome ledge (where you almost don't need a PAS). There are all kinds of ways to accidentally take small falls onto the PAS

Hell even pulling in to try to clip a closer loop...if you let go you might have a 0.5 - 1.0 Factor fall.

Any of these scenarios a dynamic material helps LOADS, and there simply is not really any benefit to using a static material when the rope isn't in the system to absorb.

Jef Anstey wrote:

Bad situations happen though. Sometimes you need to reach high to an chor that is high above the ledge or you want to place a piece of gear or something. Sometimes people brain fart. Sometimes you trip on your super awesome ledge (where you almost don't need a PAS). There are all kinds of ways to accidentally take small falls onto the PAS

Hell even pulling in to try to clip a closer loop...if you let go you might have a 0.5 - 1.0 Factor fall.

Any of these scenarios a dynamic material helps LOADS, and there simply is not really any benefit to using a static material when the rope isn't in the system to absorb.

yep, all of these scenarios (that are each about as likely as getting hit by an asteroid) are great reasons to use a dynamic material.  As long as you understand the limitations of a static material it is extremely easy to eliminate the risk of any of those proposed scenarios (i.e. just don't ever unweight the pas once you are clipped into it).

Ken Noyce wrote:

yep, all of these scenarios (that are each about as likely as getting hit by an asteroid) are great reasons to use a dynamic material.  As long as you understand the limitations of a static material it is extremely easy to eliminate the risk of any of those proposed scenarios (i.e. just don't ever unweight the pas once you are clipped into it).

For real?

I understand these risks of course...but I certainly have moments unweighting my PAS...

it's not ALWAYS possible to stay weighted and still function at the anchor

I mean usually I might only end up with a foot of slack in my personal anchor...but it definitely happens...when you're hanging low below your components sometimes pulling up or moving in closer is necessary (even I shorten the tether takes a moment of slack)

Jef Anstey wrote:

Yes it would.

In fact even better would be if you had a more dynamic PAS, such as self making a chain of cordelette loops, especially if it was dynamic cordelette.

Better yet, a Purcell prusik, of cordelette for a continuously adjustable, dynamically energy absorbing PAS. (If you fall on it, forces can be as low as HALF the equivalent impact as on dyneema, because the prusik will slip, absorbing energy and spreading the force over more time)

Sterling makes a nylon PAS, called the Chain Reactor.

Ken Noyce wrote:

yep, all of these scenarios (that are each about as likely as getting hit by an asteroid) are great reasons to use a dynamic material.  As long as you understand the limitations of a static material it is extremely easy to eliminate the risk of any of those proposed scenarios (i.e. just don't ever unweight the pas once you are clipped into it).

See, the thing with accidents is you don't plan on them happening. You are at a hanging belay with your feet smeared on some small edges and the leader is trying to move around you to start the next pitch. After some mid-wall tango with your partner where you load and unload your PAS they're off. They place a piece right off the belay but it starts to cause rope drag when they're 15 feet above it. You move a few feet above the anchor to unclip it for them.They make it to the next anchor, and soon have you on belay. To get off the bolted belay station your on you lean into your PAS and unweight it to unclip it...You just got hit with 3 asteroids in one belay. 

sfotex wrote:

See, the thing with accidents is you don't plan on them happening. You are at a hanging belay with your feet smeared on some small edges and the leader is trying to move around you to start the next pitch. After some mid-wall tango with your partner where you load and unload your PAS they're off. They place a piece right off the belay but it starts to cause rope drag when they're 15 feet above it. You move a few feet above the anchor to unclip it for them.They make it to the next anchor, and soon have you on belay. To get off the bolted belay station your on you lean into your PAS and unweight it to unclip it...You just got hit with 3 asteroids in one belay. 

yet in these three asteroids as you call them, only 1 of them was actually dangerous with a dyneema PAS (neither the slight unweighting while tangoing with your partner nor the leaning in to unclip the PAS is even remotely dangerous, and if you are climbing a few feet above the anchor to unclip a piece you have just made an absolutely terrible choice regardless of if your PAS is dyneema or nylon. 

Jef Anstey wrote:

For real?

I understand these risks of course...but I certainly have moments unweighting my PAS...

it's not ALWAYS possible to stay weighted and still function at the anchor

I mean usually I might only end up with a foot of slack in my personal anchor...but it definitely happens...when you're hanging low below your components sometimes pulling up or moving in closer is necessary (even I shorten the tether takes a moment of slack)

Yep, for real.  Slight unweightings of a PAS, be it nylon or dyneema are not dangerous, even falling a foot onto dyneema isn't going to break the PAS, it might hurt you a bit (more of just being uncomfortable than hurt), but it won't kill you. A human body is actually quite dynamic and will limit the loads to a great extent, the difference between nylon and dyneema when it's attached to a human body is pretty insignificant in the case of a PAS.

Yes, it is important to understand the limitations of a dyneema PAS, but if you are climbing above an anchor while attached to any kind of PAS you have already messed up pretty badly.  

Ken Noyce wrote:

yet in these three asteroids as you call them, only 1 of them was actually dangerous with a dyneema PAS (neither the slight unweighting while tangoing with your partner nor the leaning in to unclip the PAS is even remotely dangerous, and if you are climbing a few feet above the anchor to unclip a piece you have just made an absolutely terrible choice regardless of if your PAS is dyneema or nylon. 

Good thing we always make good choices. 

sfotex wrote:

Good thing we always make good choices. 

Which is really the whole point of this video.  If we have a better understanding of the risks we can make better choices.  So many people have tried to use this video in the years since it came out to say "Oh no, dyneema is bad, don't use dyneema" when that isn't really the take away from the video at all, the video is just some useful information to help us to be able to make better choices and to have a better understanding of the consequences of our choices.  

Perhaps the moral of the video is don't let your steel masses take long, high-fall-factor, free falls directly on slings. For short (less than a foot or two), low-fall-factor falls by humans, the human body can take on a significant portion of the fall energy, reducing the force/energy transferred by/to the sling. A metolius PAS, and I presume the Sterling version, is similar to a semi-static rope in regard to its fall arrest behavior. 

Perhaps of more significant concern for the thin dyneema slings is their propensity to age rapidly: http://www.heeresbergfuehrer.at/Archiv/TextuFotos/Ablage/2016/16Gebrauchsdauer%20von%20Bandschlingen.pdf from

https://www.alpenverein.de/chameleon/public/ebefc557-b30d-8e66-6229-76efab14e96e/DAV-Panorama-4-2015-Komplettversion_26112.pdf

(German language articles...)

Definitely don't let your steel masses take long, high-fall-factor, free falls directly on old slings. Recommendation: don't let any humans take high-fall-factor falls on your anchor, regardless of the tethering technology...