Slingin Hexes

[Bronco]

I impulsivley purchased a full set of BD Hexes off of the REI outlet website that are not wired. I plan to tie them with a double fish knot using some spectra cord and my question is:

How long (distance between the hex and clip in point) do you want to tie them?

Any other advice is appreciated.

 

[Dru]

make sure the knot is about halfway down on one side of loop for smaller sizes. if placed at bottom of loop it can flip biners around and at top it can stick in crack and push hex out. best place for it on larger hexes is inside the hex...

length wise, try measuring it so a tied loop hangs from your gear loop down to mid-thigh. that avoids the hex-in-the-knees curse. i think you want about 75 centimeter lengths of cord before you begin knot-tying

of course, if you make it longer, its easier to use as an emergency prussik!!

[Griff]

I'm thinking you will want a triple fisherman's knot for that Spectra...

[Teogo]

I worked in a climbing shop for about 5 years and slung alot of hexes....1.15 meters of cord always seemed to be about right. A triple fisherman is worth considering as the knot will be a little more semi-permanent.

Some of the larger hexes--if you purchased a 10 or 11----can have the knot hidden on the inside of the hex to keep it out of the way, if you so perfer. By-the-way, I would consider replacing the cord every three years or so if you're using the peice regularly. The yarns in these high-strength cord are often spectra, and spectra does not stand up to the cycle of bending and flexing as well as some materials.

ciao

teogo

[Dru]

the downside of the triple fissureman is that it's so big it jams like a nut, in narrow spots in cracks, and either catches when you are placing or when the hex is racked on your harness....

i tied off my hexes in 1990 with double fishermens and those same knots haven't moved an inch in 10 years (admittedly for the last 5 I haven't even used my hexes but..)

[Guest]

I start with 24 inches of spectra and tie a double fisherman's. Works for me.

[dan_e]

I think Teogo is confusing spectra with kevlar cord. The old high content kevlar cord is prone to damage from repeated bending. My hexes are still slung with kevlar cord, pretty cool stuff since it's much stiffer than spectra and make for easier placements. The kevlar cord required a triple-fish, and it probably won't hurt to use the same on the spectra cord. It looks like they still make cord using some Kevlar fibers, but the amount used is probably less that the original Kevlar cord. Maxim makes this stuff "5.5 Specta/A Cord" It's about $1.15 a foot though!

[AJ]

There was some discussion of cord and webbing material back a couple months ago. It was focused on cord-o-lette products, but some of it is applicable here. See http://www.cascadeclimbers.com/ubb/Forum9/HTML/000015.html

Anyway, I came across a paper that should cause you to think twice about using a double fisherman's knot for higher strength cords. Also, it might be a good idea to replace that type of cord more frequently than every 11 years.

To quote from the previous thread:

I 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

 

 

[Retrosaurus]

Bronco,

Congratulations on "impulsively" stumbling on to a superior product. Black Diamond really dropped the ball when they started making hexes wired only.

Wired Hexes suck. The Cable springs against the sides of cracks making placement and removal more dificult. And in horizontal cracks the cable sticks out like a stiffy allowing the rope to transmit all sorts of motion to the nut.

Wired hexes look better on the shelf and on your rack and save you the extra steps involved in slinging them, but are vastly inferior when it comes to function.

Tying the not inside the hex is the only way to go. You can even go so far as to use a water knot inside when a double fisherman's no longer fits. I feel secure using this knot inside the hex as long as the ends of the knot is jammed tightly within the nut ant the tails of the knot are left as long as possible while still ramaining inside the nut so as not to interfere with endwise placement.