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Seeking test data: rope on rope

Original Post
Pierce-Kenji · · Unknown Hometown · Joined Dec 2014 · Points: 5

Hello MP

I was putting it out there to see if anyone has, knows sources for, or is interested in creating, pull test data for soft-good connections in various configurations; specifically as it applies to rope.

Strength reductions in a basket hitch formation, rope-to-rope in same diameter, for example.

I'm already aware of the steep loss in strength between small-diameter items (like Dyneema slings) and higher diameter material (such as nylon slings), and the nuances of girth/basket hitch connections between varieties of slings, but I'm having a hard time finding similar data on cordage, and especially full-sized rope.

What kind of strength reductions happen when a rope is loaded across itself? Outside of the obvious abrasion damage due to friction, of course.

Thanks!

bearbreeder · · Unknown Hometown · Joined Mar 2009 · Points: 3,065

for various cord and sling widths ...

DAV Panorama 2007

DAV Panorama 2007

DAV Panorama 2007

;)

Tom-onator · · trollfreesociety · Joined Feb 2010 · Points: 790

If one consenting rope wants to hop on another consenting rope for some "action" in the privacy of a daily rate rope bag, why do we need to collect data on their knotty interaction?

Assuming both ropes are of legal age...

Avalon'cha · · your girlfriend's bedroom · Joined Aug 2013 · Points: 35
Tom-onator wrote:If one consenting rope wants to hop on another consenting rope for some "action" in the privacy of a daily rate rope bag, why do we need to collect data on their knotty interaction? Assuming both ropes are of legal age...
Eeeeeew! 5 year old ropes?
Eric LaRoche · · West Swanzey, NH · Joined Aug 2011 · Points: 25

Anyone have this info in English?

Serkan Bettermann · · Unknown Hometown · Joined Jan 2015 · Points: 0
Eric LaRoche wrote:Anyone have this info in English?
I can translate if wanted :)
Pierce-Kenji · · Unknown Hometown · Joined Dec 2014 · Points: 5

Thanks for the info!

Although, I guess what I'm looking for is the breaking strength of one cord doubled over another (basket), as in for example this scenario:

One rope is shortened by a few feet, and this small piece is tied off around a tree. The longer remainder of this rope is threaded through this and rappelled off of. What is the theoretical breaking strength of this connection?

JohnnyG · · Unknown Hometown · Joined Nov 2009 · Points: 10
Serkan Bettermann wrote: I can translate if wanted :)
yeah me too. 12,9 kN translates to 12.9 kN
Gunkiemike · · Unknown Hometown · Joined Jul 2009 · Points: 3,492
Pierce-Kenji wrote:Thanks for the info! Although, I guess what I'm looking for is the breaking strength of one cord doubled over another (basket), as in for example this scenario: One rope is shortened by a few feet, and this small piece is tied off around a tree. The longer remainder of this rope is threaded through this and rappelled off of. What is the theoretical breaking strength of this connection?
While it may not be as quantitative as you're looking for, my answer to this question is: VERY much stronger than you need for the rappel. Absolutely no need to worry as long as you're careful to eliminate rope-on-rope movement. So not simul-rapping or lowering. Folks have been rapping off cord (with no metal between them) for decades.
Pierce-Kenji · · Unknown Hometown · Joined Dec 2014 · Points: 5

Right, GunkieMike and Jake, I know that it would by a large margin hold a rappel; rappelling sees some of the lowest forces in climbing, so high degrees of strength reduction are still acceptable.

However, my interest in the specific pull test data - to failure - extend to more than just a rappel scenario. I just used that example because it was the closest common situation that could be pictured easily.

I'd like to know just how much of the rope's strength is retained, before the radii of the two bends causes the contact point to fail. I'm interested in how strong such a connection is at maximum loading, vs the same point connected instead by, say, a carabiner or other hardware.

Thanks for all the responses!

Pierce-Kenji · · Unknown Hometown · Joined Dec 2014 · Points: 5

Also interested in how much this reduction is mitigated by increasing the number of strands being contacted. It seems to me that in particular would be a more complicated measurement, as it isn't just a simple matter of doubling or tripling the bend radius.

Pierce-Kenji · · Unknown Hometown · Joined Dec 2014 · Points: 5

In other words, how capable is this connection of tolerating some real forces, not just the load of body weight.

Mr. Wonderful · · Unknown Hometown · Joined Apr 2014 · Points: 10
JohnnyG wrote: yeah me too. 12,9 kN translates to 12.9 kN
It is a shame to see such a great joke wasted on this website.
Jim Titt · · Germany · Joined Nov 2009 · Points: 490

I doubt anyone has ever tested this in a climbing scenario since it is not part of the safety chain system we use. However the rope does not fail through the tie-in points of a harness so clearly it doesn´t have a major effect.
Nobody has reported that I know of that using a bowline bend to join two ropes causes failure where the ropes cross.

Gunkiemike · · Unknown Hometown · Joined Jul 2009 · Points: 3,492
Pierce-Kenji wrote:In other words, how capable is this connection of tolerating some real forces, not just the load of body weight.
Oh please, stop trying to make this relevant when it's not. You're looking for hard numbers that are in fact TOTALLY IRRELEVANT and meaningless.

REAL forces are forces that might be generated during normal climbing activities. And what everyone is trying to tell you is that normal climbing activities will not generate the level of forces that would threaten a climbing rope.

Feel free to keep up this vision quest of yours but be honest about what it is - a purely academic curiosity with no practical relevance to anything we do.

Real forces...pfft.
Pierce-Kenji · · Unknown Hometown · Joined Dec 2014 · Points: 5

I'm sorry this line of questioning offends you.

To be perfectly honest this isn't in relation to a climbing-specific scenario at all. The rappel example was given ONLY for clarity. My mistake. Clearly it only served to cloud your perception of me. In fact the only similarity between the system I am interested in and "anything you do" is that it involves cordage. Not even necessarily kernmantle.

It isn't 'purely academic' either, as I am working on something during my extensive climbing downtime due to breaking my spine. Call it killing time if you want, but I am NOT trying to waste anyone's precious time here. Just looking for any help in a direction to continue searching.

However I had hoped that if anyone on the internet had the interest, resources, and patience for such a "vision quest" involving pull tests, it might be climbers. I guess I'm wrong.

Pierce-Kenji · · Unknown Hometown · Joined Dec 2014 · Points: 5

And Mike, if you believe this type of information is truly useless for anyone in any field, then I think what you should be saying instead is that no one has ever found any reason to conduct such tests, and that I should find someone to perform some because no data exists.

That would be completely fine, and well within my expectations. What I didn't expect was to be mocked.

Guideline #1: Don't be a jerk.

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