difference between static and dynamic rope?

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 doc_h 15 Nov 2019

No, not that difference.... 

I'm interested to know how they differ in manufacturing methods, not in their physical properties.

Both seem to be kernmantle construction so how do they manage to make one rope that stretches a lot and another that stretches very little? Do static lines have the kern woven or plaited as well as the mantle, unlike dynamic ropes, or is it made with different materials? 

  

 Toerag 15 Nov 2019
In reply to doc_h:

Statics probably use pre-stretched fibres if they're nylon, or other inherently less stretchy materials like polyester. Dyneema / Spectra is pre-stretched, but that's quite an extreme example.

2
OP doc_h 16 Nov 2019
In reply to Toerag:

Hmm, I wonder whether prestreching the kern would tend to make the rope kink more as it would constantly be trying to reduce the length of the mantle. And wouldn't it bring the rope permanently nearer to its elastic limit so that it would break more easily when it gets additional loading?

I wondered about nylon vs polyester but have seen statics made out of either material.

I'm very surprised that I couldn't easily find any info on the Internet, hence the post.

 d_b 16 Nov 2019
In reply to doc_h:

I remember seeing a video once that I am now unable to find that suggested that they heat treat dynamic rope to shorten it. You start with something static and end up with something dynamic and shorter.

Edit: I just found a different video that says the dynamic effect is due to the way fibres are laid out in the core. 

https://m.youtube.com/watch?v=EWmzdsfeeZM&t=149s

Post edited at 09:20
OP doc_h 16 Nov 2019
In reply to d_b:

Thank you, I had seen that video. It talks about and shows the inside of a dynamic rope and also mentions what they call a 'special' rope that is 'stronger than steel' but unfortunately it does not mention ordinary static ropes. The 'special' rope seems to have a plaited kern. That's where I got the ides from in my OP that perhaps static ropes also have a plaited kern - but I've no evidence of this (unless I take one of mine apart). 

cp123 16 Nov 2019
In reply to doc_h:

Dynamic ropes have twisted cores which can untwist a little under a large load, making them stretchy.  Static ropes have braided core so less opportunity to stretch.

This video describes it here at 5 min 20 secs in: youtube.com/watch?v=HG9GaAMKxJA&t=322

Post edited at 18:51
 oldie 16 Nov 2019
In reply to doc_h:

https://blog.weighmyrack.com/how-climbing-ropes-are-made-at-edelrid/

Gives a textual explanation as well as video. I think it does not specifically mention static ropes but I seem to remember being told that the nylon yarns were twisted, woven etc so the final rope was much less dynamic. 

OP doc_h 16 Nov 2019
In reply to cp123: and oldie:

Ah ha, that seems to be it. Makes sense that the static has a braided kern.

Funny how I've gone for years using both types of ropes and although I often thought about how they must be made I'd never bothered to find out for sure until now.

Thanks to all who responded

 Wayne S 17 Nov 2019
In reply to doc_h:

When I saw the title , I thought ay up a newb question. However a very interesting question.  

Think I learnt something today.

Wayne

 Dan Arkle 17 Nov 2019
In reply to all:

Having watched both videos, twice. We have not yet been clearly told what makes the difference.

We are told that braided the core makes a rope less stretchy, and twisting the fibres makes it more dynamic. We are told that the heat treatment is very important too. 

We are not told anywhere that either /all of these are THE difference between dynamic and static rope. 

Another possible contribution could be the size of the original fibres. 


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