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  1. #1
    Senior Member DemostiX's Avatar
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    Dynaglide weight

    Would someone here with an accurate scale weigh a good length of this, so there is no question about rounding error influencing the measurement in a major way?

    Say 30 feet (or more) on a weight-weenies gram scale accurate to a gram. (Accurate to a gram, not reading out in gram units.)

    No inference, please, and no reference to manufacturer's / seller's spec sheet, (where .1 lb per hundred feet could be as much as .149 lb rounded down. That's 49% heavier.)

    I think this is important, because Dynaglide has a break strength which brings many here to use it, and more to be attracted by some claims such as the one from Samson on its weight per length.

    I'm not asking its diameter. With hollow braid rope, that is truly a nominal dimension. Just an accurate (and hopefully unbiased) measurement of the weight per unit length.

    ------
    If personal anecdotes matter. I have some 8-strand Spectra sold to me as 1/8", but which is no heavier, by weight / length than Amsteel Blue 7/64". The Spectra is uncoated, (NOS) new old stock , and maybe as strong per weight as Amsteel. But, just as the difference between 7/64" and 1/8" (nominals) is just 1/64", the breaking strength difference between them is 800 lb, consistent with the larger line packing 50% more yarn into a length than the smaller line. And I think this Spectra has a much lower strength than the seller still insists on believing.
    Last edited by DemostiX; 07-27-2011 at 19:30. Reason: correction

  2. #2
    Senior Member rip waverly's Avatar
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    someone here put this together...not sure if it helps

    http://www.hammockforums.net/forum/a...9&d=1311746299
    "Jeff-Becking"

    DOWNTOWN BROWN!!!!

  3. #3
    Senior Member DemostiX's Avatar
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    Rip, that's just what I was referring to and responding to. We both saw it.
    Unless I find out otherwise from good measurement, I suspect the 1.6 oz per 100 ft is a calculated, inferred value, from Samson's spec sheet stating it weighs .1 lb per 100 ft.

    That's not a .10 lb /100 ft claim; that's a .1 lb / 100 ft. claim. So the only thing I'm certain of about the 1.6 oz (=.10 x 16 oz) claim is that it is not a bad inference from .05lb per 100ft rounded up, so that Dynaglide really weighs just .8 oz ( ie 23 grams) per 100 ft. That would be so ridiculous nobody would believe it. (Or would he?)

    Anyone with a good scale and a quantity of Dynaglide to weigh accurately? Maybe one of the vendors here?
    Last edited by DemostiX; 07-27-2011 at 19:55. Reason: correction

  4. #4
    GrizzlyAdams's Avatar
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    Quote Originally Posted by DemostiX View Post
    Rip, that's just what I was referring to and responding to. We both saw it.
    Unless I find out otherwise from good measurement, I suspect the 1.6 oz per 100 ft is a calculated, inferred value, from Samson's spec sheet stating it weighs .1 lb per 100 ft.

    That's not a .10 lb /100 ft claim; that's a .1 lb / 100 ft. claim. So the only thing I'm certain of about the 1.6 oz (=.10 x 16 oz) claim is that it is not a bad inference from .05lb per 100ft rounded up, and that Dynaglide really weighs just .8 oz (14 grams) per 100 ft.

    Anyone with a good scale and a quantity of Dynaglide to weigh accurately?
    I will be able to do this, later this p.m.
    Grizz
    (alias ProfessorHammock on youtube)

  5. #5
    GrizzlyAdams's Avatar
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    well now, this was interesting.

    First thing, test the accuracy of the scale. It is reported to be accurate to 0.5 grams. I put 3 US quarters on it, it reports 17g. Standard weight of a quarter is 5.67 which is surely an approximation for 5 2/3, times 3 equals 17, check.

    I measured off a length of dynaglide I have, 4 feet at a time on a 48" long measuring stick, counted off almost exactly 28 such lengths, call it 112 ft.

    Put it on my scale...wavers between 82.5 and 83 grams
    dynaglide.jpg

    So do the math and you get 74.1 grams / 100 ft, which is 2.61 oz / 100 ft.
    Known on the street as 0.163125 lbs / 100 ft.

    So the reported 0.1 lbs / 100 ft is an approximation with a large relative error.

    Good intuition there DemostiX!
    Grizz
    (alias ProfessorHammock on youtube)

  6. #6
    SmokeBait's Avatar
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    I had a 79' 6" piece of bright green dynaglide that weighed in at 60 grams. I checked my scale with the 3 quarters method (thanks Grizz) and got 17g. So that calculates out to 75.5g/100 feet and real close to what Grizz measured. I measured 20' at a time and there is room for a little bit of error in that process due to line tension and the multiple lengths measured. If I was a betting man, and I'm not, I wouldn't be surprised to see a slight difference from orange to green and even batch to batch of the same color. It's all good though

  7. #7
    Senior Member DemostiX's Avatar
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    Smoke Bait:

    Thank-you so much for your careful measurement. I'm sure Grizz appreciates the simple and independent observation as much as I do. (No smiley there, because there's no irony in it, given what I infer about Grizz from his numerous posts, videos, investigations and inquiries.)

    I'll comment further after researching some more and after others have taken an opportunity to use available instruments to measure / estimate the real mass of the line they use here on planet Earth.

  8. #8
    Senior Member DemostiX's Avatar
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    Quote Originally Posted by GrizzlyAdams View Post
    well now, this was interesting.

    <snip>

    So do the math and you get 74.1 grams / 100 ft, which is 2.61 oz / 100 ft.
    Known on the street as 0.163125 lbs / 100 ft.

    So the reported 0.1 lbs / 100 ft is an approximation with a large relative error.

    Good intuition there DemostiX!
    Grizz:
    Thanks for the credit, but there are too many years in and of schooling, and many more of practice as a demographer and statistician to credit intuition.

    And, anyway I was partly wrong, (but happy to have everyone here with Dynaglide honestly and capably address the question.) It is a disappointment to learn that rounding error alone (ie. .149999 lb rounded to the nearest .1 lb) does not explain the real weight. Or to distinguish probability from likelihood, the real weight does not explain or account for Samson's product listing. Others' credulity for this long time is something I'll take up later.

    For the record, you didn't have to employ video tech to shoot a photo of a digital scale reading for me to trust that you'd made and correctly reported a best estimate.

    Part of what I'm thinking about is how far and in what direction "if there aren't pics, it didn't happen" is taking us. Not liking it, though, I'd urge that no numbers be shown that are not significant, and by that I mean "significant" in an everyday sense of the word. We read from left to right, and what we read most recently, the digits to the right of the decimal, the least significant part, are our most recent memories. Most of that is clutter.

    Especially, thank you for staying in character, doing what Professor Hammock (and Grizz) do.

  9. #9
    Stormstaff's Avatar
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    As a noob I have a question. Is all this scientific stuff just to know how much weight someone is carrying while backpacking or such? Or is the a strength issue due to incorrect weight measurements?

  10. #10
    GrizzlyAdams's Avatar
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    Quote Originally Posted by SmokeBait View Post
    I had a 79' 6" piece of bright green dynaglide that weighed in at 60 grams. I checked my scale with the 3 quarters method (thanks Grizz) and got 17g. So that calculates out to 75.5g/100 feet and real close to what Grizz measured. I measured 20' at a time and there is room for a little bit of error in that process due to line tension and the multiple lengths measured. If I was a betting man, and I'm not, I wouldn't be surprised to see a slight difference from orange to green and even batch to batch of the same color. It's all good though
    Thanks SmokeBait for the 2nd assessment.

    The key thing to come out of this is to be careful in extrapolating out from the advertised 0.1 lb / 100 ft. I've done that myself, without thinking through how many significant digits I really had.

    Dynaglide is 50% heavier than I had previously figured. But what's half an oz per 100 ft of cord really matter…? One less bite out of a Snickers bar.
    Grizz
    (alias ProfessorHammock on youtube)

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