Rope construction

[NorcoDavid]

Could anybody point me to some information on climbing rope construction, I'm sure I have been told/read somewhere that other than the usual kernmantle design there are other types where the outer sheath is where the main strength lies, rather than the core. Could anyone confirm or deny this?

Thanks

[JLA Arborists]

http://en.m.wikipedia.org/wiki/Kernmantle_rope

[Loler UK]

HI David, not too sure where to point you for comprehensive reading as our industry probably uses the most diverse range of rope constructions, one or two of which are almost exclusively used by us.

 

Firstly you mention kern mantle, literally meaning core and cover usually used to describe a rope that has paralell core strands with a braided cover (ie the core is not braided) but this term is often misused in many ways by both us arbs & other rope professionals so best thing is to focus on more specific terms when getting into detail to save confusion

 

One of the most important things to consider/ learn is how the load is bared by the rope, for example Yale XTC 16 strand rope is one of the most popular arb climbing ropes, it has a 16 strand polyester cover that is load baring, the rope is 'cover dependant' some would say, this is unusual for rope, the core is made of several parallel twisted polyester strands which are not essential for the ropes strength but hold it firm and round for our friction cords to grip & slide smoothly along; and in use they take about 30% of the load so the cover takes 70% removing the core does not lead to significant strength loss per-say and in some configurations the lack of the core can even lead to a preferential loading pattern of the cover strands (hmm maybe i'm getting ahead of my self here back to basics)

 

Marlow gecko is a very similar rope the main difference being that the core is braided so this rope is a double braid but just like XTC 16 its a cover dependant rope at about 70-30

 

Marlow aeris is a core dependant rope with a braided cover and parallel core strands it is approximately 90ish% core 10% on the cover so the construction 'type' is kernmantle just like xtc but it loads in a VERY different way!

 

So double braid ropes that we use for climbing/ rigging could load and do load in any of these following cover:core ratios: 70:30 60:40 50:50 40:60 30:70 20:80 10:90 0:100!! some people would describe the last as a passive cover and we rarely use these in arb but I do occasionally in some specialist applications

 

there's allot more to construction than we tend to talk about, fibre types have different properties such as stretch to help absorb impacts and dissipate forces but so can the type of construction, the pitch of the fibres in any given construction type and the relations between the core & cover's different properties, there's a bit too much for me to cover here whilst i'm sat here waiting for my next group of skiers to arrive but i hope this helps you with some searching.

 

I should probably have asked why it was you were asking to point you down the most useful avenue, whoops lol, so why were you asking?

[DJP Arb]

@lolerUk that was a very informative reply and as a climber I feel I should no more about rope construction / technology than I currently do. I would be interested in being pointed in some direction for further reading in this subject. Cheers - Dave

[NorcoDavid]

As said above, very informative, I really appreciate it thanks very much for the reply!

The main reason other than general interest was simply a discussion I was having with a colleague who wasn't convinced when I said that some ropes rely more on the outer than the core saying that all ropes are mainly using the core for strength.

I'm sure I read somewhere that there were several different technical names for ropes such as cover dependant ones and core dependant ones ( I may be remembering wrong)

All in all, if I use the kit I like to learn about it and you certainly helped there

Thanks again

[Loler UK]

im gald it helped, cant really suggest further reading as i took 10,000's of snippets from 1000's of articles, instruction manuals, research papers, bsen standards and loads of advice & teaching from manufacturers, riggers, engineers and lots of other great people from in the industry, just trying to pass some of it in as it was so generously passed to me.

[NorcoDavid]

And I appreciate it, always good to learn and expand your knowledge

[Loler UK]

the most important thing is to assume nothing i suppose, check your sources, i experience allot of myth and rumour in the industry and its caught me a few times, especially earlier in my career, people who should have known better than to prostitute incorrect information given their standing in our industry.

 

i remember lolering a bristol firm and failing a 'soft' lanyard with a catastrophic snag that the climber had clearly been climbing on for some time, it was still attached to his harness with the adjuster mallioned to his harness and the snag in the active section between it and the 3-way hook spliced to the other end. His boss protested that it shouldn't have failed and explained to me that the core was in tact and the rope maintained all of its strength. setting aside the significant issues that a damaged cover on a core dependant rope presents, the rope was cover dependant the core was there to serve more or less as packing. The firm in question had not had a loler done in some time and a year or 2 later they took it in house, not a firm id be working for that's for sure!!

 

that said i've known RETAILERS give out this incorrect information to end users and even loler examiners! maybe there's a market for some further training out there lol

[nod]

Solid information Mike. As you point out, understanding of any subject matter must come through extensive scrutiny of other peoples FACTUAL messages. Only in this manner is it possible to acheive such a breadth of knowledge that clearly exists within your posts, above. However, as you know, this is clearly not the whole picture so we must continually ask questions & not take the answers for granted. :-)