ROPE WEAR IN CLIMBING AND IN LABORATORY-Giuliano Bressan

[John Paul Sanborn]

I do not know if we have seen this paper, but there are a few interesting things in it. I could not find a date, though the URL has 2002 in it.

http://personal.strath.ac.uk/andrew.mclaren/Turin2002/CD congresso/ROPE WEAR .pdf

Decay in dynamic performance of ropes due to wear

First of all let’s make it clear that it’s improper to talk about “rope ageing”; it’s only wear (or more rarely environmental effects) that causes rope degradation: in fact, contrary to all expectations, the performance of a properly stored rope does not decay with time.

The results of the dynamic tests, made on the Dodero according to UIAA standards, show that new and used ropes generate about the same holding force on the first fall. This means that wear does not affect elongation on the first fall, but leads to plastic deformation and/or breakage of filaments, which produce cumulative effects in the subsequent falls.

 

[SINGLE-JACK]

Kong ROBOT?

I do not know if we have seen this paper, but there are a few interesting things in it. I could not find a date, though the URL has 2002 in it.

http://personal.strath.ac.uk/andrew.mclaren/Turin2002/CD congresso/ROPE WEAR .pdf

Decay in dynamic performance of ropes due to wear

Does anyone use the Kong ROBOT tested in the above link?

 

[TheTreeSpyder]

Nice study; i think though if most of a rope's strength is on outside/sheath and not inner/kern we would see more strength and elastic loss on 'sheath' damage. This study covers rescue etc. lines that carry more of the loading on the kern/core than a lot of arboris'ts lines? There have been some studies stating that feline urine (acids and retaitned crystals) was more of a detriment to strength that petrol; as i understand.

i always and all ways think that we need to break these things down into elastic/dynamic and static properties and loads; as this author does hear. Elastic properties are the least understood, and they are invoked during usually the peak loading in the scenario of the impacts. Elasticity is also the more degradeable asset too. It has 3 categories of use after use: recoverable, recoverable later, and unrecoverable. Recoverable gives the recoil and that part of the elemeant can immediately be reused. But the later recoverable part of these assets can make the differance in not having that asset after a couple of hits until hours later. Taking the same hit then can spell disaster, more harshly tightened knots etc. Of curse unrecoverable, fused strands, stiff strands etc. due knot ever regain the elastic asset/ property again.

Samson Rope Inspection has some nice pics.

Samson Arborist Catalog.pdf covers about wear and rope history too. It is good to know the history of your own ropes, and inspect them. Have other lines to use, and downgrade appropriately older/more used lines to lighter loads, dragging etc. to keep that bulk wear off the 'good' lines.

Elastic dampening also depends on the load on the line as a percentage of the line strength. A 500# impact might get very little elastic buffering on a 10k line, but a 1500# impact will get lots more dampening. This is true also if we double that 10k line into a 2/1, then it takes a hit, the line and anchor/support will take more of a hit/ has less elastic dampening than the 1500# hitting on a single support line of 10k. It has 1500 on 10k, but the doubled line has 750 (per leg of support) on 10k. This is all then acentuated by the lenght of each support leg. Short leg giving less dampening, etc.

 

[John Paul Sanborn]

From what i understand; most of the cordage we use is relatively static compared to other disciplines. Do you think that a standardized modulus rating would be useful? Such as 20% of MBS at 20 ft to put the rope at realistic maximum working conditions. Or would a 10% or even 5% MBS be more realistic for regular working conditions?

 

[SINGLE-JACK]

...
Taking the same hit then can spell disaster, more harshly tightened knots etc. Of curse unrecoverable, fused strands, stiff strands etc. due knot ever regain the elastic asset/ property again.
...

TheTreeSpyder - Your brief reference to the affects of knots, above, reminded me of an uncharacteristicly short post of yours:
(http://www.arboristsite.com/showpost.php?p=1596894&postcount=36)
suggesting the use of the figure 9.

I don't want to hyjack this thread into the wrong direction but have been meaning to ask (post) you about it. Dr. Dave F. Merchant (http://www.lifeonaline.com/) states figure 9 is better and stonger than the figure 8 and offers much less stress on the rope (tie-in to this thread). Some have even suggested that it is as strong as an eye splice.

I've started to use it some and like how easy it is to un-tie after a heavy load but it's a damn big knot. I'd be interested in your opinion and other opinions about its usefullness.

 

[TheTreeSpyder]

i think the best answer is that there is no single answer; best to have many ways to go, and practiced enough to know when to deploy, based on the tradeoffs that everything has.

Fig 9. can take longer time, more line, be bulkier, can't adjust like prussik. But, easier to untie, take more load, pull inline, easier on stiff lines etc. So, to each task and it's needs an allowances; you just have another choice hear. Play with it sum allow any fascination or newness carry you deeper into knowing it better, polish and place lessons on gun belt, to draw out instantly when needed to take specific/ not all target(s) out. If everything was one size fits all, anybody could do it, there'd be no choices to make; and m'Lady and i wouldn't be using an old pair of JP's dungarees as a nice cozy, dbl. sleeping bag.

On just a simple tiedown, cheap rope, low loading/ utility grade situations, ; i'd go with Butterfly, in tese lower, less critical loading ranges that don't need adjust-ability etc. Prussick for low loading, adjust-ability, perhaps flex-ability. And 9 (or 10) for higher loading, stiffer, thicker lines(truck pull on 3:1 etc.), more critical operations, etc. But after L-earning, each time tying any; you can observe (hands as worker, and then dbl. time it by eyes being supervisor, inspector etc. as you go), recalculate, get better feel for all this; and even study all when tying any single one; once you understand the principals enough to know (most) all principals in scenario and how much of each you are factoring in and out of the formulae with each move, IMLHO.