Sterling 5.9mm Power Cord

https://www.backcountry.com/sterling-powercord-cordelette-6mm

I picked up 5.5m of 5.9mm Power Cord. I decided to replace my thick 7mm bluewater cordalette, it is so much lighter! So far I like the way it handles, I made some practice anchors with it at home. 

My question is about any limitations or drawbacks of using this type of cord for anchor building situations? Does anyone have any input on this,  do you love it or hate it? 

I switched to powercord a couple years ago and never looked back. Like you said, it's much lighter, more compact AND rated ~19kn when full strength. When you add a knot, you reduce its strength capacity by 20-50% depending on what knot, etc. Besides general bulk, the biggest advantage for me is being able to take the full length cord and tie a figure 8 on a bight on each end. You can now connect farther away anchor points with a single strand that is still rated higher than the gear it is connected to. If you use regular 7mm cord for this, the single strand is potentially rated to a lower load than the gear you are clipping, so you wind up derating your gear (only if used as a single strand!). If you have closer proximity points, clip both figure 8 ends into the same piece of gear to essentially make a loop and use like a regular tied cordelette.

Technora core cord can lose it's strength if repeatedly folded/bended/tied over and over. This AMGA source references a study from 2000 that shows it can lose 60% of its strength. Is it still true? I don't know. But probably replace your cordelette more often if using technora core. IF anyone has updated or more info on this it would be appreciated.

https://books.google.com/books?id=EU6LBAAAQBAJ&pg=PA50&lpg=PA50&dq=technora+cordelette+climbing&source=bl&ots=j2RI4iwHHh&sig=uxGuW9iqKUekS35yMNaBbdI2BgM&hl=en&sa=X&ei=DlWMVdLcKImWyQT_mYeIDg&ved=0CFkQ6AEwBQ

Truly amazing compact cord with one real limitation.

If you have friends that really like to dog moves and work on stuff they can't do you're better off packing in burly nasty noodle cord. It will wear if you really flop around under it on sharp rock - like anyhting will.

I use it almost exclusively except for projects or routes with groups where I know there will be some sawing action going on. 

You can also carry more of it on you than the thick cord if you want. For really extreme outings you can even replace your boot laces, shoe laces, bag laces with it for emergency tat supply. 

https://user.xmission.com/~tmoyer/testing/High_Strength_Cord.pdf

Yes, repeated flexing and knotting/unknotting will decrease strength in kevlar, technora, spectra, dyneema, UHMWPE... but decrease it to less of an extent with nylon or polyester... Webbing has less abrasion resistance than kernmantle cord. 7mm accessory cord is cheap, strong, and its strength will not decrease anywhere near as fast with repeated knotting/unknotting.

Just assume 50% reduction in strength with any knots. That's just a good number to use in general with any rope, makes math easier. If you happen to over estimate the strength loss, then no biggie, its stronger than you thought.

Any high strength core you want to tie it into a loop with a triple fishermans instead of a double fishermans. Potential exception would be for cords where the sheath and core are bound in the way they are woven, such as the old mammut pro cord (which wouldn't matter as its not a kevlar/technora or spectra/dyneema/UHMWPE core). Paraloc Piranha is a sailing rope similar in construction to the old mammut pro cord, but dyneema core... Its not nice to use, has a "memory" and isn't supple like you want, just pass on it, trust me.

Re: 5.9 powercord. Hollow braid technora core, uncoated. The hollow braid construction makes splicing possible, but without a coating it unravels easily. Its very very static, like dyneema, so don't ever put it in a situation where you want it to have some stretch. Very stiff like the 5.5mm dyneema core cord. Not ideal for friction hitch use due to the stiffness, which is a shame because the high temp resistant core would be ideal to have for friction hitches. I personally prefer to keep high strength cordellettes tied up with a figure 8 on a bight on each end and deploy them in "W" style pre-equalized anchors, or a normal 3 piece anchor where both figure 8s are on one of the pieces.

Thanks for the detailed responses, lots to think about with this new cord! 

We just tested it if you want to see how it performed in knots.  The blog also has the data but the video is typically more helpful since you can see how things were breaking.   hownot2.com/post/backties  

Thanks for this testing Ryan! This shows the W fig 8 loop ends for single strand anchor legs is pushing the material right to the limit of potential max loads (ff2). And it is in fact de-rating bigger gear. This is incredible insight. 

Jake woo wrote:

Thanks for this testing Ryan! This shows the W fig 8 loop ends for single strand anchor legs is pushing the material right to the limit of potential max loads (ff2). And it is in fact de-rating bigger gear. This is incredible insight. 

This isn't all that of a revelation, 7mm cord breaks at similar loads as does edelrid tech webbing and people still use bunny ear cordelletes.

These days if you want to use a bunny ears type of anchor (as I like to) it is best to use the presewn stuff. 

that guy named seb wrote:

This isn't all that of a revelation, 7mm cord breaks at similar loads as does edelrid tech webbing and people still use bunny ear cordelletes.

powercord is rated ~19.5kn and 7mm is usually 13kn. That's a 50% difference in nominal load rating. So this isn't comparing the same thing. Plus, as mentioned above by myself and others, we have been using the W, fig 8 loop ends for our cord with the assumption it was rated above max potential loads. We have been proven wrong (gladly and thankfully). So it truly has been a revelation.

Alex C wrote:

From the perspective of making trad belays, this definitely gives me less confidence in a single-strand anchor leg using powercord with fig-8 loops on the ends. Is it reasonable to extrapolate that a double-strand anchor leg would see results similar to the tests with a 2:1 backtie, i.e. around 15kn?

15-16 kN is probably a good guess.  It depends on the knot(s) used and a few other factors, for example the 2:1 backtie test they did failed in the knot that wasn't the figure-8, and they got just less than 2X the figure-8 strength.

Moyer and Harmston (2000) tested Bluewater Titan, which is 5.5mm with a dyneema core (Powercord is aramid).  It is rated at 13 kN and broke in a loop (triple fisherman) at 15 kN and a single cordalette leg (broke at master point overhand) at 14 kN.  Powercord might test a bit higher because it has a higher single strand rating.

Just for reference, they also tested 7mm nylon (rating 11 kN), and it was 11 kN with a single strand figure-8, and ~20 kN in a loop (fisherman) and a cordalette leg (overhand).

Hyperstatic materials (dyneema, aramid, etc.) have worse knot strength than semi-static (nylon, polyester) because they don't distribute loads as well around the bends in the knot, and these lower knotted strengths are pretty consistent across tests.  Trad gear is rarely rated higher than 10-12 kN, so materials with a loop strength that exceeds this are probably all fine, depending on your personal risk tolerance.

Edit: Sterling VT-X and Bluewater Titan (dyneema core) may have better fatigue properties than the aramid-based Powercord and both are probably plenty strong for cordalettes.

Is anyone using this for top rope anchors.  How is the cut resistance?

Andrew R wrote:

Is anyone using this for top rope anchors.  How is the cut resistance?

I have used Power Cord for a top rope anchor masterpoint in a pinch but it does not inspire much confidence. <6mm cord is quite thin and for a top rope where no one is watching the anchor it is probably best to either heavily pad the edge or use something with a thicker sheath. Still better than using webbing imo.

Kyle Tarry wrote:

Moyer and Harmston (2000) tested Bluewater Titan, which is 5.5mm with a dyneema core (Powercord is aramid).  It is rated at 13 kN and broke in a loop (triple fisherman) at 15 kN and a single cordalette leg (broke at master point overhand) at 14 kN.  Powercord might test a bit higher because it has a higher single strand rating.

Just for reference, they also tested 7mm nylon (rating 11 kN), and it was 11 kN with a single strand figure-8, and ~20 kN in a loop (fisherman) and a cordalette leg (overhand).

Hyperstatic materials (dyneema, aramid, etc.) have worse knot strength than semi-static (nylon, polyester) because they don't distribute loads as well around the bends in the knot, and these lower knotted strengths are pretty consistent across tests.  Trad gear is rarely rated higher than 10-12 kN, so materials with a loop strength that exceeds this are probably all fine, depending on your personal risk tolerance.

Thanks Kyle - very helpful.  Liking my 7mm Sterling cord even more now.

Desert Rock Sports wrote:

https://user.xmission.com/~tmoyer/testing/High_Strength_Cord.pdf

Yes, repeated flexing and knotting/unknotting will decrease strength in kevlar, technora, spectra, dyneema, UHMWPE... but decrease it to less of an extent with nylon or polyester... Webbing has less abrasion resistance than kernmantle cord. 7mm accessory cord is cheap, strong, and its strength will not decrease anywhere near as fast with repeated knotting/unknotting.

Just assume 50% reduction in strength with any knots. That's just a good number to use in general with any rope, makes math easier. If you happen to over estimate the strength loss, then no biggie, its stronger than you thought.

Any high strength core you want to tie it into a loop with a triple fishermans instead of a double fishermans. Potential exception would be for cords where the sheath and core are bound in the way they are woven, such as the old mammut pro cord (which wouldn't matter as its not a kevlar/technora or spectra/dyneema/UHMWPE core). Paraloc Piranha is a sailing rope similar in construction to the old mammut pro cord, but dyneema core... Its not nice to use, has a "memory" and isn't supple like you want, just pass on it, trust me.

Re: 5.9 powercord. Hollow braid technora core, uncoated. The hollow braid construction makes splicing possible, but without a coating it unravels easily. Its very very static, like dyneema, so don't ever put it in a situation where you want it to have some stretch. Very stiff like the 5.5mm dyneema core cord. Not ideal for friction hitch use due to the stiffness, which is a shame because the high temp resistant core would be ideal to have for friction hitches. I personally prefer to keep high strength cordellettes tied up with a figure 8 on a bight on each end and deploy them in "W" style pre-equalized anchors, or a normal 3 piece anchor where both figure 8s are on one of the pieces.

Kevlar has a long history of developing weakness after repeated flexing. It has excellent longitudinal-strength-to-weight ratio and yet is brittle and has been found to crumble after repeated flexing. Other aramid fibers, such as Technora, may have the same weakness. I wouldn’t use it for situations in which knots are tied and loaded repeatedly.

Spectra (Dyneema), on the other hand, isn’t weakened by such flexing, although it is susceptible to abrasion and cutting over edges. 

It's a shame that Tom Moyers  20+ yr old work is still our Bible, but please study it.  https://user.xmission.com/~tmoyer/testing/ It's a very straightforward piece of work.

Among other things it compared 7mm nylon with Titan cord  (UHMWPE), and Technora (aramid)  cords.  Tested straight,  the hihg tech cords were stronger.  But if you tied a fig8 on the end, and tested that, the 7mm nylon was strongest!.  If you tied a loop and pulled it, the nylon was strongest!   And if you put the cord through a hole in a fixture, then rocked the fixture back and forth with a 40lb weight on the cord, and then tested the cord strength, it took only 200 cycles for the nylon to be stronger than the Technora, and 300 cycles to pass the TItan cord.

I figure that y'all are using these things either with a knot on the end, or in loops!  The new cord is more expensive, wears out faster and is weaker in use than 7mm nylon.  If you need to cut your safety margins, why not go down to 6mn nylon? It will cut cost and weight as well.

I'm sure that Teijin has improved on the aramid of 20+ years ago.  Organic chemistry has a very deep toolset. And I don't know how flexing in a knot weighted to 200lbs compares to a metal jig with 40lbs.   But the (used) Technora (Sterling Power Cord)  tested on the above referenced How-not-2 broke weaker than the Technora  Tom Moyers tested  20+yrs ago.  And despite reading too  much rc.com and mountain project over the last ~18yrs, I have never seen similar date presented on any of the newer tech cords. Save money, recycle less stuff, and wear a lighter belt, or something.

Alex C wrote:

From the perspective of making trad belays, this definitely gives me less confidence in a single-strand anchor leg using powercord with fig-8 loops on the ends. Is it reasonable to extrapolate that a double-strand anchor leg would see results similar to the tests with a 2:1 backtie, i.e. around 15kn?

Yes.  I did some tests with normal 6mm accessory cord (yet to be edited) and single strand outter legs with double in the middle (like a webolette) broke around 15kn but when every leg was doubled it was 30+ kN.  

Andrew R wrote:

Is anyone using this for top rope anchors.  How is the cut resistance?

I'm building an abrasion tester to find out!

Ryan Jenks wrote:

Yes.  I did some tests with normal 6mm accessory cord (yet to be edited) and single strand outter legs with double in the middle (like a webolette) broke around 15kn but when every leg was doubled it was 30+ kN.  

Thanks for all the testing you do and the info you provide, Ryan!

Was this test completed with a 3-piece "equalized" anchor?  If so, can you also test the individual arms of the anchor?  A single strand of 6mm with a figure-8 might only hold 6-7 kN, and that could be kinda "hidden" if we only look at the strength of the whole system.  But if the center piece was to pull, or the direction of load changes a bit and it's not equalized any more, you might become more dependent on those weaker leg(s).

Sooo in terms of three piece trad anchors: sterling 5.9 power cord, 7mm nylon, or 240cm quad length dyneema sling...  Is there a right/wrong answer?

Jason L. wrote:

Sooo in terms of three piece trad anchors: sterling 5.9 power cord, 7mm nylon, or 240cm quad length dyneema sling...  Is there a right/wrong answer?

"Right" and "wrong" answers are hard to come by without fine tuning your questions. Based on the evidence upthread and the breaking strength of dyneema slings when knotted (note that they break used material first then new material), it would appear that if you care about max strength then 7mm nylon is the clear winner. If you are willing to compromise on strength for weight then power cord or dyneema may be acceptable. You (and your partner), of course, must judge that tradeoff for yourself since it is your safety on the line. 

Personally, I own power cord and will not be throwing it out in favor for 7mm nylon until it reaches the end of its lifespan. However, I will only be using it in configurations were there are two legs per piece.