perlon runners?

[Colin]

For my runners, I always use single spectra slings tripled over, and I let them out when there might be rope drag. A friend of mine always uses the single/tripled system, but he uses tied perlon 6mm cord instead of spectra. He argues that on alpine climbs cord is more versatile for such things as v-threads, and retying slings for rap anchors in general. This sounds like a good justification to me, but I think that perlon is heavier, and significantly weaker than spectra. Perhaps spectra cord, or maxim tech cord are the best of both worlds? I would appreciate anyone's opinions on the subject.

[Alex]

Spectra is too slippery to tie in knots safely, so you can't take slings and tie them, though cord is another story.

6mm perlon has a breaking strength of only 1000 pounds, so this is a poor choice for runners and should only be used as rap cord, v-thread material, or prussiks.

for cordalettes I use 5.5 Gemini or technora or take your pick. Something strong.

for runners I use a combination: spectra *sewn* slings and tubular nylon webbing tied slings, to leave behind. Spectra is lighter, stronger and better, nylon is cheaper.

Best bet is to carry a good assortment of all of these things. Versatility is #1 in the alpine...

Alex

[Colin]

When I suggested "spectra cord," I did not mean flat spectra webbing. Spectra cord (5.5mm Gemini, which you use for your cordelletes, IS made of spectra) CAN be tied, and has a strength of 22kn (the same as commercially sewn slings).

[Alex]

yes. ".., though cord is another story." Sorry I did not make clear that I was only referring to spectra webbing.

As I understand it: "Whats best for alpine runners, v-threads, all-around good juju accessory material?"

Couple of considerations:

1) Strength. Yes, Spectra cord, Gemini, Maxim whatever is the best.

2) Ease of Use. Depending on exactly what, it can also be hard to cut, tie, and work with.

3) Cost. Unless you like paying 2-3$ a foot, other stuff can easily substitute for spectra cord.

4) Wear. Cord wears slower than webbing in general, less surface area to volume.

5) UV resistance. For slings left in the field, its best to use something more UV resistant. Spectra tends to break down pretty quick, but I am not sure how it is compared to other materials.

With that in mind:

Spectra cord for: things involving anchors, things where high strength is required, things you wont leave behind often or use alot of length for.

Perlon cord for: things involving body weight only, things you leave behind like rap slings and v-threads

spectra and nylon webbing for: things that require medium strength, do not suffer from continual wear, things you leave behind like rap slings and v-threads

Sorry to be long-winded

Alex

[AJ]

I know this is slightly off the topic, but I just came across a paper titled "Comparative Testing of High Strength Cord" by Tom Moyer and Chris Harmston. Chris is the QA manager at Black Diamond and Tom is an active climber and mechanical engineer from the Salt Lake City area.

Basically they set about testing various cord and webbing materials for use as cord-o-lettes. Their results were pretty interesting. The tensile strength of BD Gemini2 (Technora) and Maxim Spectra A were very high in a slow pull tensile test without any knots/bends. However, once they put a figure 8 knot in the material they decreased quickly. In their testing the hightest strength was Mountain Tools ultratape and then Sterling 7 mm nylon (perlon). Essentially the very stiff cord materials did not perform very well when tied. BD Gemini had a 60% reduction in strength when tied in a figure 8, but 7 mm nylon only had an 8% reduction (so it was still stronger than the technora material).

They went on to try double and triple fisherman's knots and found that 7 mm nylon still outperformed technora, spectra and vectran cords (barely outperformed spectra/kevlar -- the Maxim Spectra A). They also found that Double Fisherman's and triple fisherman's knots did very well in Mtn. Tools Ultratape and standard 1" tubular webbing. The testers noticed that kevlar and spectra type materials had a consistent failure mode when tied in a double fisherman's -- the sheath breaks at the knot and the slippery core unties and pulls through the sheath. This didn't happen with a triple fisherman's and the strength of the loop was higher when tied with the triple. Also, in their testing they found that Mtn. Tools Ultratape tied with a standard water knot held almost as much as tied with either a double or triple fisherman's knot which surprised them since they thought it was too slippery to hold knots (they did caution that more testing needs to be done with other brands of slippery webbing).

When they tested cord-o-lette stength they concluded that in both static and dynamic (drop) testing that 1" tubular worked best followed by Maxim Spectra A and 7 mm nylon.

Finally when they tested cyclical bending of the material they found that the stiffer cords saw significant weakening with increased cycles. 1" tubular, Mtn. Tools ultratape and 7 mm nylon saw almost no loss of strength over 1000 cycles.

What Tom Moyer concluded is that stiff cord can make a good chock cord since you desire a stiff material, but they make poor cord-o-lettes since you are never sure how much strength you have lost. He liked using webbing for cord-o-lettes like the "webolette" from Mtn. Tools since it is more compact and performed well, but it wasn't quite as strong has he wanted. However, he seemed to have a stong endorsement for using 7 mm nylon or 1" tubular since they are inexpensive, strong and available almost anywhere.

Something to think about next time you are selecting the material for a cord or webbing based system.

[Peter_Baer]

Do you have a link or reference to that paper?

[AJ]

Sorry - I only have a paper copy. This was presented at the International Technical Rescue Symposium in Tuscon, AZ last October. I tried to find it on the web but wasn't able. There is a post by Tom Moyer on Fish's web site that summarizes his report (and some other good stuff about water knots)... http://www.fishproducts.com/tech/webbing.html

Hope that helps.