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  1. #41
    WV's Avatar
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    Quote Originally Posted by DemostiX View Post
    Maybe it is the same seller, "Shawn.....".
    For my first purchases from him, I won two auctions to take advantage of combined shipping. To reduce seller's costs, I told him it was fine with me to not include the cardboard he mounted the hanks on. That way he might be able to mail both hanks by First Class Mail, which has a 13 oz weight limit, and pocket a few extra $.

    He shipped promptly by First Class, and my tip off was that the lightweight mailing envelope contained the cardboard mounts. "Too light for 200+ feet of 1/8" 1500 lb line!!"

    Then I opened the package and was surprised at the visual comparison with 'spensive 1/8" Amsteel Blue I splurged on 10 feet of. Puny, sickly, and so limp!

    Seller disagreed with me, not persuade by the weight / length relationship, but immediately refunded everything, including shipping. He said he would conduct breaking strength tests of his own to confirm his listing.

    Maybe you bought line from the same spool after he had done so -- how hard can it be for amateurs to conduct such tests? A set of barbell weights, an anvil with jaws, and lever? --and he de-rated it.

    But, that Spectra (tm) sure is silky smooth and easy to run large fids through, isn't it?
    Yup - same seller. I bought from him at least a year ago, not lately. He showed a willingness to negotiate shipping and such then. I'm glad you found him fairly reasonable, too. If you decide you don't want the spectra you got from him, I'll buy it from you. I have other uses for it than full hammock suspensions, and it splices very easily. I have some 7/64" Amsteel I could swap with you, too. (Only drawback is it's blue; beware of Smurfy fingers. )
    ---
    Just re-read your post - looks like you returned the Spectra. I bought some Vectran 1/16" from him, too, and have used it for structural ridgelines. Possible swap there, too.
    Last edited by WV; 07-30-2011 at 10:41.

  2. #42
    Senior Member DemostiX's Avatar
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    Quote Originally Posted by DemostiX View Post
    <snip>

    I suppose it possible to make rope less well, such that the strands damaged each other in some disproportionate way as the rope was made smaller or larger. <snip>
    This is what has been reported to be a serious issue with early Kevlar and some other Aramid fibers in ropes. Maybe in shows up in pre-browser internet archives for backpackers.

    In use and even just in tension, the braided fibers micro-fracture, like glass, progressively. The rope looked OK, with strands intact, but it progressively loses breaking strength. If I understood the actual physical mechanisms correctly, different rope construction techniques would result in Kevlar / aramid ropes with different and better lifespans.

    This was a bummer for those who invested in Kevlar rope and rope making, because one of the nice properties of Kevlar is heat resistance, from, say, running through winches. Where better to take advantage of that but in the jacket / mantle of the rope? Exactly where it was most exposed to those micro-fractures.

  3. #43
    Senior Member TiredFeet's Avatar
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    Quote Originally Posted by DemostiX View Post
    ...................I'm just showing how the manufacturer (and likely the distributor) rate the strength of the rope. It is right there in the tables, and the basis seems to be the entirely intuitive physics of mass. ..............
    I very seriously doubt that the manufacturers are calculating the strength of the rope based on the rope diameter.

    With their resources, they can very easily just put a length in the testing machine and destructively test it. They can just as easily do this for 2, or 3 or ..... 10 samples. They then can determine a min, max and average. Samson reports all three in the specs I have seen.

    The fact that the tables show a relationship between the diameter and the strength is not indicative that they calculated the strength based on the diameter, but rather that the physical properties of the rope dictated that relationship and so the relationship is reflected in the tables.

    I think you have your thinking backwards.

  4. #44
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    i know this thread is a bit dated , someone asked if i had the decimal point in the wrong space ,so what i have is another set of 7ft dyneema whoopies, a new scale, just does ounces, here is what i have you decide, [IMG][/IMG] [IMG][/IMG] TRAV. so if i entered the info correctly on the conversion site it comes out to this ,

    0.05oz = 1.4175g

    does that look correct?
    Last edited by TRAVELER; 05-05-2013 at 11:52.

  5. #45
    Senior Member ahhhgladius's Avatar
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    it does to me.
    Glory to the Fallen, Honor to the Lost. Faith to the Missing. Carry on Forever.

  6. #46
    Senior Member DemostiX's Avatar
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    No, it is wrong.

    Your scale may be outside of its range. If you wish to measure the weight of the clothing you are wearing, you can take it all off and pile it on the bathroom scale. You will get a lousy measurement. If the scale is digital, you may get no measurement. The scale isn't meant for babies.....or gear.

    If you instead weigh yourself with and without clothing, on the same scale, and subtract, you will get an estimate taken from measurements within the range of the scale to the resolution of the scale. (Step on and off and on some digital scale. When they read identically, to the tenth of a lb /kg, it is likely because there is a memory device to report the same measurement when it is likely of the same weight, within some time interval. Make the user think it has more resolution than it really does.)

    Try that subtraction trick with this scale. And note that US Nickels of the last decades have weighed 5.0g. Use them for calibration. (Or US Quarters; newer than 1964 each weigh 0.20oz. )

    Also, note that even if the scale were within its range and it measured PERFECTLY, you are showing just one digit:
    Could be .0549999 oz rounded down.
    Could be .045 oz rounded up. Which amounts to a 9 - 11 % error in presentation; and makes the conversion to five places on metric (gram) bar look falsely precise.

    With the right scale, such as gram counters use, or even with a postal scale, 30ft of Dynaglide will be reliably differentiated, by weight, from Amsteel Blue 7/64". Someone else surely has the weight / length for the 2.2mm Samson throwline. You'll need a scale with greater resolution to tell it, just by weight from the Dynaglide.

    -------------
    As it's been awhile, I'll repeat that the sizes of line are nominal. All of the hollow Dyneema line is made of fiber of the same density. After use, the strands will be tight against one another, and it all MUST measure in true diameter proportional to the square root of its weight (per length). With small line like this the nominal size is just that, for naming. So, one maker's 2.5mm line is another's 3mm. And Dynaglide will sometimes be labeled as 2mm and elsewhere as 1.8mm.
    Last edited by DemostiX; 05-08-2013 at 12:53. Reason: resolution, US quarter weight

  7. #47
    Senior Member Mouseskowitz's Avatar
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    The couple of posts about the breaking point of Dynaglide seems to be inline with the find print on NERs data sheet.
    Tensile strengths reported are approximate averages for new, unused ropes. To estimate the minimum tensile strength of a new rope, reduce the approximate average by 10%. (The Cordage Institute defines minimum tensile strength as two standard deviations below the average tensile strength of the rope.) Stretch data tested to CI 1500-02.

    If one wanted to get technical with the weight issue they look up the specifications mentioned in this portion of the fine print.
    Compliance to the above specifications is based upon testing according to the Cordage Institute Standard Testing Methods for Fiber Rope and/or ASTM D-4268 Standard Methods of Testing Fiber Ropes. Weights are approximate and may vary +/- 5%.

    The data sheet can be found here.

  8. #48
    Senior Member DemostiX's Avatar
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    I'm warned not to rehash.

    So, just reminders: Dynaglide is explicitly a throw rope for arborists, used to haul up other ropes, saws, blocks and tackle. NERopes would not / did not respond to me about its tests for it. The only other throw rope with this high reported breaking strength seems, by description, as though it could be from the same maker. It is called Stein Safety throw line, sold in British Commonwealth countries. IIRC, NERopes is a division of a European-owned cordage maker. Maybe they are the same cord with different badges.

    The issue with weight per length of Dynaglide could have been due to the same problem I addressed a post or two back, rounding error and resolution. From early posts in the thread, you'll see those issues were insufficient to explain the misreport of Dynaglide weight. As happens in catalogs -- and I've been through lots of lots of them -- there are occasional printing errors. I look forward to congratulating the HF member who discovers the hi-tek cord which has been neglected by everyone because its weight was printed in catalogs as 35-50% greater than it really is.

    I'm happy you mentioned the Cordage Institute and its standards.

  9. #49
    Mullach' Abu XTrekker's Avatar
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    The site I bought this from called it IronWire but it is in fact Dynaglide; it is 2mm Dyneema with 1000 lbs breaking strength. I bought 50' of it and it weighs 37 grams.
    ...Thats 2.4278 grams per meter of DynaGlide or 0.74g per foot


    2013-05-08093745_zpsa09ca93b.jpg

    And to verify that my scale is accurate...7 Nickels equals 35g
    2013-05-08095836_zps9372fad7.jpg

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