Edge Testing Standardization for Ropes

I don't believe it's a viable cert to offer; regardless of the properties of a given rope, subjecting a safety standard to this is outside of a manufacturer's pervue, basically part of the acceptable risk taken in technical climbing.

I guess I disagree with you Mark. I think it would be a handy thing to know when buying a rope. With the different materials and technologies I would assume that there could be instances where a 9.8mm rope would rate as high or higher than a 10.5 from a different manufacturer.

Agreed there are inherent risks in climbing, but it would be interesting to see how the ropes stack up. For example all "Dry" ropes are not as dry as one another.

Prod.

moved from Eldo accident reported in DC:

10mm ropes have ~20% more cross-sectional area over 9mm ropes. If the strands per unit area are similar, then you would have ~20% more rope strands. If you want a whopper 11mm rope, you have ~50% more rope strands than a 9mm rope.

Some ropes do have a "edge resistance" rating: factor ~2 fall over a 0.75mm radius edge. This is barely a comparable rating, since the edge is 90°. There are several ropes under 10mm with the rating (Edelweiss, Beal).
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Mark,
Are you suggesting that the edge resistance test is useless, or unnecessary, or dangerous (false sense of security)?

I think it is a useful factor in choosing between ropes: i.e. all specifications being equal (weight per length, impact force, # falls) then I will choose a rope with the edge resistance rating. I wish there were a useful measurement of the cut resistance of a rope; a number rather than a pass/fail. Again, there are several factors for choosing a rope, and I see this as another useful specification for the decision.

John Wilder wrote: rope construction really hasn't changed much since it was invented

I wonder if there is a way to embed some abrasion-resistant strands of some other material in with the nylon? It maybe would have to be woven like the kernmantle to not compromise the stretchy-ness of the rope...

Any rope experts out there?

Probably something quick and dirty that comes to my mind is that there is no real world control over what type of an edge a climber might subject their rope.

At what confidence can nylon material say edge-certified and actually resist failure from a dynamic hit on a sharp edge?

There has been a good deal of advancement in static systems (to discuss John Wilder's point also); it's almost a running joke between rescue teams about mainline failures and testing disputes. Which isn't to say rigging can't be failed, but it would really be a contaminant, rockfall, or human error to fail a system in static loading with the mainlines that are put to use in rescue.

From Sterling Rope, page 14:
sterlingrope.com/media/docu…

16. What is “sharp edge resistance”?
There are no documented cases of a rope breaking under “normal use”. The documented occurrences
of rope breakages in the field are attributed to pre-exposure to sulfuric acid or by being cut by
a sharp edge. UIAA just recently added an optional test to UIAA 101 for testing to sharp edge resistance
(UIAA 108). Many manufacturers are claiming sharp edge resistance for their ropes. The designation
of sharp edge resistance is not a guarantee of safety. These ropes can still be cut. Our inhouse
testing shows that slight variables in the testing procedure can cause even “edge safe resistant”
ropes to break on the first fall. We have recently received a letter from APAVE, the UIAA Approved
Lab that we use for testing, that their “insurance company strongly recommend us to inform our customers
that this test does not reproduce the reality and that the behavior of a rope in contact with a
sharp edge can be radically different from the UIAA 108 test conditions and results.” sterlingrope.com/media/docu…

Correct me here, but I believe the UIAA cert was abandoned.

Mark Nelson wrote:At what confidence can nylon material say edge-certified and actually resist failure from a dynamic hit on a sharp edge?

Correct me if I am wrong, but isn't that what the "edge resistance test" is - a factor 2 (or 1.77) fall on an edge with a small radius (0.75mm)? It isn't the "real world", but neither are any of the other ratings for a rope. At some point you can make a standardized test and compare relative results.

It certainly will never say "edge-proof", but is a relative factor in edge cut resistance.

While the material (nylon) is the same for ropes, construction is not.

Mark Nelson wrote:Correct me here, but I believe the UIAA cert was abandoned.

AH yes, here:

Climbing Mag
UIAA Suspends Rope Test
By Dougald MacDonald

The UIAA, the international federation of alpine clubs, has suspended certification of ropes under its “sharp edge” test, after problems surfaced at its approved testing laboratories. The UIAA Safety Standard 108 measured dynamic ropes’ resistance to cutting over an edge under the force of a simulated fall. But discrepancies were found in test results for the same rope at different laboratories.

Testing of ropes against this safety standard stopped as of July 1. Ropes already certified “Sharp Edge Resistant” will retain that status until Dec. 31, 2005, after which they can no longer be marketed this way. The UIAA is working on a new plan for rope inspections and will post updates on its web site: uiaa.ch/index.aspx.

Here also -- midway down the page

theuiaa.org/act_safety.html

I don't believe anything has been updated on this cert to give it credible standardization.

Regardless, wouldn't it indeed only serve to offer a false sense in the application of dynamic loading?

Casey Bernal wrote:10mm ropes have ~20% more cross-sectional area over 9mm ropes. If the strands per unit area are similar, then you would have ~20% more rope strands. If you want a whopper 11mm rope, you have ~50% more rope strands than a 9mm rope. Some ropes do have a "edge resistance" rating: factor ~2 fall over a 0.75mm radius edge. This is barely a comparable rating, since the edge is 90°. There are several ropes under 10mm with the rating (Edelweiss, Beal).

Are these numbers significant? Well maybe. In an abrasive cutting action such as a pendulum, cross section may play a role. In a fall onto or swinging across a sharp edge this may be less significant, imo.

All sheaths are not created equal. Manufacturers vary the weaves such as more bobbins for greater abrasion resistance and fewer bobbins for increased dynamics in a given diameter. They already know how to make ropes more durable but at the expense of dynamics such as impact force. I guess the question Mark has presented is can they give us a meaningful and objective index. I think they could. But as the durability index goes up, the impact force would go up proportionally. This is the challenge for rope manufacturers. Who cares how burly your rope is to abrasion if a lead fall generates such a high impact force that you are ripping your gear or busting a kidney. It all about balance with the current rope technology.

Greg D wrote: 9mm has a cross section of 28.27 sq mm. 10mm has a cross section of 31.42 sq mm. Only 11% more. 11mm has a cross section of 34.56 sq mm. Only 22% more than 9mm.

Those are circumferences (d*pi), not cross sections (d/2)^2*pi.

Greg D wrote: This must be some kind of new math. Sorry for the sarchasm. 9mm has a cross section of 28.27 sq mm. 10mm has a cross section of 31.42 sq mm. Only 11% more. 11mm has a cross section of 34.56 sq mm. Only 22% more than 9mm. Are these numbers significant? Well maybe. In an abrasive cutting action such as a pendulum, cross section may play a role. In a fall onto or swinging across a sharp edge this may be less significant, imo. All sheaths are not created equal. Manufacturers vary the weaves such as more bobbins for greater abrasion resistance and fewer bobbins for increased dynamics in a given diameter. They already know how to make ropes more durable but at the expense of dynamics such as impact force. I guess the question Mark has presented is can they give us a meaningful and objective index. I think they could. But as the durability index goes up, the impact force would go up proportionally. This is the challenge for rope manufacturers. Who cares how burly your rope is to abrasion if a lead fall generates such a high impact force that you are ripping your gear or busting a kidney. It all about balance with the current rope technology.

9x9x3.14 = 254
10x10x3.14 = 314
(314-254)/254 = 23%

Brett Brotherton wrote: 9x9x3.14 = 254 10x10x3.14 = 314 (314-254)/254 = 23%

In my haste I made a mistake. But you are squaring the diameter when you should square the radius. Not 9 x 9 but 4.5 x 4.5 x 3.14

brenta wrote: Those are circumferences (d*pi), not cross sections (d/2)^2*pi.

yes. My mistake. Corrected numbers.

10 mm is 23% more cross section than 9 mm.
11 mm is 21% more cross section than 10 mm

For what it's worth, from the Edelweiss web site:

I've liked these ropes for many years. They handle well, are tough, and seem to hold up for a long period of time. I can't say as to whether this makes a real difference, but it certainly can't hurt. I would be surprised if there was a way to standardize edge resistance, and if they could, would it really mean the same thing in the field? Probably not.