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USnavy
Apr 8, 2011, 6:49 AM
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As I understand it, Dyneema and Spectra are brand names of high-modulus polyethylene. Correct?
Now Kevlar I know is a brand name, but what type of material is it? Is it an aramid?
What is the difference between aramid and high-modules polyethylene, as it relates to climbing? I have seen cordlette made of aramid but I have never heard of a sling made of aramid where as I have seen cordelette and slings made out of polyethylene, or Dyneema as its so commonly called.
And lastly, is Tech Cord simply aramid or is it made of polyethylene, or does it depend on the manufacturer? I was comparing some 5.5mm Tech Cord to some 6mm cordelette made of aramid last night, and it was clear they are not the same, the Tech Cord was far stiffer and the core was woven in a much different pattern.
(This post was edited by USnavy on Apr 8, 2011, 6:54 AM)
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sbaclimber
Apr 8, 2011, 12:47 PM
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USnavy wrote: Now Kevlar I know is a brand name, but what type of material is it? Is it an aramid?
http://not_even_going_to_give_you_the_link
Edit: pretty much every one of your questions can be answered within two clicks of a one word search in Google.
(This post was edited by sbaclimber on Apr 8, 2011, 12:52 PM)
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MS1
Apr 8, 2011, 2:05 PM
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That chart is a fantastic resource. The difference between the first and the final column is so dramatic; nylon, which has the lowest single strand strength, ends up the strongest when tied as a cordelette and subjected to multiple load cycles.
MSCC_chart wrote: Strength Comparison of Prospective Cordelette Materials* Material Strength 1 Loss 1 Cordelette Loss 2 Strength 2 7 mm Perlon (Sterling) 12 kN 8% 22 kN 0% 22 kN 5.5 mm Spectra (Blue Water Titan) 17 kN 47% 17 kN 6% 16 kN 5.5 mm Spectra A (Maxim) 18 kN 29% 33 kN 40% 14 kN 5 mm Gemini (Black Diamond)*** 22 kN 60% 18 kN 45% 10 kN Table Key Strength 1: Tensil strength of a single strand Loss 1: Loss in strength when knotted with a figure eight Cordelette: Strength of a cordelette with one anchor Loss 2: Loss in strength after 200 flexing/bending cycles Strength 2: Cordelette strength after 200 flexing/bending cycles** |
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mattm
Apr 8, 2011, 2:07 PM
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MS1 wrote: That chart is a fantastic resource. The difference between the first and the final column is so dramatic; nylon, which has the lowest single strand strength, ends up the strongest when tied as a cordelette and subjected to multiple load cycles. MSCC_chart wrote: Strength Comparison of Prospective Cordelette Materials* Material Strength 1 Loss 1 Cordelette Loss 2 Strength 2 7 mm Perlon (Sterling) 12 kN 8% 22 kN 0% 22 kN 5.5 mm Spectra (Blue Water Titan) 17 kN 47% 17 kN 6% 16 kN 5.5 mm Spectra A (Maxim) 18 kN 29% 33 kN 40% 14 kN 5 mm Gemini (Black Diamond)*** 22 kN 60% 18 kN 45% 10 kN Table Key Strength 1: Tensil strength of a single strand Loss 1: Loss in strength when knotted with a figure eight Cordelette: Strength of a cordelette with one anchor Loss 2: Loss in strength after 200 flexing/bending cycles Strength 2: Cordelette strength after 200 flexing/bending cycles**
Yep, I use 6.5mm Dynamic Nylon Prussik cord now - giving it a whirl to see how it does.
The non-nylon cord has it's place for certain things but not cordelettes
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Gmburns2000
Apr 8, 2011, 2:23 PM
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Thanks for posting this link.
Since this is a climbing site, it is nice that we can collect climbing-relative info on this site, rather than having to "search on google." if I searched on google for all of my climbing questions then I'd have little need for this or other climbing sites. so thanks for being helpful.
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dynosore
Apr 8, 2011, 3:08 PM
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To answer the original question, about 50k daltons *snort*
aka google it!
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roy_hinkley_jr
Apr 8, 2011, 3:46 PM
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MS1 wrote: That chart is a fantastic resource. The difference between the first and the final column is so dramatic; nylon, which has the lowest single strand strength, ends up the strongest when tied as a cordelette and subjected to multiple load cycles.
That chart is a joke. Read the fine print. The final column was not derived by actual testing, the products listed are very outdated, and some of the numbers are flat out wrong.
BTW there are slight differences between Spectra and Dyneema. And there are major differences between Kevlar and Technora.
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MS1
Apr 8, 2011, 5:03 PM
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roy_hinkley_jr wrote: MS1 wrote: That chart is a fantastic resource. The difference between the first and the final column is so dramatic; nylon, which has the lowest single strand strength, ends up the strongest when tied as a cordelette and subjected to multiple load cycles. That chart is a joke. Read the fine print. The final column was not derived by actual testing, the products listed are very outdated, and some of the numbers are flat out wrong. BTW there are slight differences between Spectra and Dyneema. And there are major differences between Kevlar and Technora.
Care to point us to something better?
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mattm
Apr 8, 2011, 7:26 PM
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roy_hinkley_jr wrote: MS1 wrote: That chart is a fantastic resource. The difference between the first and the final column is so dramatic; nylon, which has the lowest single strand strength, ends up the strongest when tied as a cordelette and subjected to multiple load cycles. That chart is a joke. Read the fine print. The final column was not derived by actual testing, the products listed are very outdated, and some of the numbers are flat out wrong. BTW there are slight differences between Spectra and Dyneema. And there are major differences between Kevlar and Technora.
A joke? Hardly. How 'bout offering up better info?
3 of the 4 products listed ARE current (Perlon, Titan and Maxim Tech Cord are all available on their respective websites).
Spectra and Dyneema are the SAME material. Spectra's fibers don't have the same uniformity that dyneema's do.
Technora and Kevlar are both ARAMID fibers. Technora is much less susceptible to weakening due to repetitive flexing.
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roy_hinkley_jr
Apr 8, 2011, 8:29 PM
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You have to read the original paper by Moyer to get at the nittygritty. Lots of errors induced by static testing (creep is a bigger factor, etc) and ballpark calculations made it essentially irrelevant. Only testing one brand of 7mm was also a mistake. And 6mm cordalette cord is now available. There are several types of Spectra and Dyneema, which are made by different companies, with different characteristics. BD switched to using the Dynex name to avoid having to specify which fibers they sourced.
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FullertonImages
Apr 20, 2011, 1:57 PM
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Seems to me that there are a few big oversights in this data. First he goes on and on about the 1.66 force multiplier and how the anchor sees more force during a lead fall, but unless I'm missing something, that would be the force on the piece that catch of fall, not on the belay anchor. In many lead falls, the anchor doesn't see any ight at all. So, besides a factor 2 fall onto the anchor, the discussion of lead fall forces is mostly irrelevant. and since this is a discussion about cordelette materials, than we should only be talking about the belay anchor strength.
Secondly, it's seems to same that the tests he is referencing were only testing the single stand strength of the cordelettes, not the overall master point strength, which would have been far more useful. So even in the worst case of the tech cord being reduced to 10 kn, if you've got a three piece anchor, and with a loop of tech cord going to each piece, and all three loops captured into the master point, then you dealing with six strands of tech cord. And while that does necessarily raise the strength to 60 kn, it's definitely more than plenty. Plus, with more strands in the knot, it raises the radius of the bend for all the strands included, and therefore reduces the weakening brought on by being bent.
That's my reasoning anyways. Correct my if I'm wrong...
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tower_climber
Apr 21, 2011, 6:00 PM
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From my understanding of the article:
The discussion of the lead fall/16kN was meant to present a "worst case" scenario of how much force would be felt by an anchor.
The testing was done as follows: Pull-testing a single strand to failure. Then tying each material into a cordelette using a figure-8 and pull-testing to failure with a SINGLE anchor point (more like a runner than a true cordelette).
I think it is an interesting test with interesting results. I'd like to see it repeated with various brands of cordage because I think it would yield very useful information.
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