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  1. #21
    Senior Member
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    packability/volume/compressability a factor?

    For both backpacking and kayak camping, the volume of my gear is nearly as important as its ultra-light-weightness. I use long whoopie slings to give me options in areas where trees are far apart. Perhaps as a contribution to this scientific inquiry, I will make a set of whoopies from Amsteel Blue in the length of my dynaglide whoopies and then attempt to create an objective measurement comparison of their packability/compressability/stowability. I spent a fortune to shave barely more than an ounce off my tarp weight (spinn to cuben), and was happy to do so since the cuben tarp compresses and packs well. If the cuben tarp consumed twice the volume in my backpack or kayak hatch, I would have accepted the heavier weight of the spinn tarp in exchange for its compact compressability. Now, again, I'm assuming that the storage/compressability/packability comparison between dynaglide and Amsteel Blue becomes a factor only when you're carrying hundreds of feet of it. But it is important to measure all this stuff, objectively, and share it with our brothers and sisters so that we are fully informed consumers. Plus, for many of us, myself included, all this obsessive measurement and calculating while we're off the trail is a big part of the fun of the hobby.

  2. #22
    Senior Member opie's Avatar
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    Quote Originally Posted by DemostiX View Post
    If this is the Question



    then



    is not the answer.

    Two whoopie slings use not 100 feet, but closer to 1/4 that. The comparison is not to the magnitude of disappointment in what we thought Dynaglide weighed, but to the real difference from an established alternative, 7/64" Amsteel Blue (AB), with an average break strength of 1600lb. It is already very lightweight, something of a revolution for hanging in this hobby. It weighs 4.8 oz per 100 feet by my estimate*. So, the savings of Dynaglide over Amsteel Blue 7/64" is one 1/4th the difference in weight per 100 feet., call it 0.6 oz.

    Of course, this 0.6 oz, "one less bite out of a Snickers bar", gets the user a safety margin that is substantively significant, pushing the breaking strength from a supposed 1000 lb to 1600lb (or 1400 lb ISO certified). You, Grizz, know and will acknowledge that the 600lb strength margin in this region, for common weights of hammockers, has real value to safety.

    So, this isn't a joke about .6 oz, three quarters in a pocket.

    The question, I think, should be:
    Why was Dynaglide ever used for suspensions?

    The answers are that
    • It appeared to be far lighter than it actually is; we were fooled,
    • It was about the same price as Amsteel Blue 7/64",
    (Whether more or less expensive depends on how you treat the hank-purchase minimum.), and
    Dynaglide promised to be at or above 4 digits in breaking strength.

    (When I can, I'll report on whether Dynaglide with its putative break strength of 1000 lb, is with certainty different in its breaking strength from Zing-It (2.2) or Lash-It (2.2mm), made of exactly the same fiber, has exactly the same weight / length. Those cords have an average break-strength of 650lb, (and minimum BS of 570lb) and nobody, responsibly, is recommending them for hammock suspension.)

    Given New England Ropes (NER) marketing of Dynaglide as a throw line, I find no reason to take any more seriously their specification of breaking strength at 1000 pounds even.Their weight specification has already been shown to wrong by 60%, well beyond a margin of copy-edit rounding error. The product description states it is made of the same Dyneema SK-75 as some other products, not a further refinement on Dyneema. There is no reason, for its market, for NER to have paid more for fiber treated for purposes other than its intended use, which would value slickness and freedom from snagging among tree branches.

    *easy as it would be for folks with scales to verify weight-consciousness and trimming achievements, only Smoke Bait has joined catenary-curve-calculating Professor Hammock in coming forth with measurements.
    Dude... You need a hobby.

    But seriously.... In regards to this...

    Given New England Ropes (NER) marketing of Dynaglide as a throw line, I find no reason to take any more seriously their specification of breaking strength at 1000 pounds even.Their weight specification has already been shown to wrong by 60%, well beyond a margin of copy-edit rounding error. The product description states it is made of the same Dyneema SK-75 as some other products, not a further refinement on Dyneema. There is no reason, for its market, for NER to have paid more for fiber treated for purposes other than its intended use, which would value slickness and freedom from snagging among tree branches.
    Ive seen you on several occasions make statements or conclusions based on wrong information.

    Dynaglide, while it is Dyneema, it IS refined past what normal Dyneema is. It is pre-stretched and tension set. It has something to do with the molecules of the fibers and getting them all lined up. But Im not a molecular engineer so Im not going to even try to explain it. There is a company in the Netherlands, DSM, that has refined this process and sells a product called Dynex Dux. Size for size the Dynex Dux is far stronger than its Amsteel Blue counter. For instance, 5/16 amsteel blue has an average strengh of 13,700 while 5/16 Dynex Dux has an average strength of around 21,000 pounds. Same fiber, but more processing goes into the Dynex Dux.

    As to its strength in relation to the miscalculation on the weight... You would be wrong again. I believe Dutch pulled some Dynaglide to about 945 pounds prior to failure and I pulled a Dynaglide sling to failure which occured around 900 pounds.

    It appears you are trying to do everyone a service by propagating information, and that's a good thing. But the information you are propagating is based on incorrect information.

    Then there is this...

    It appeared to be far lighter than it actually is; we were fooled,
    I don't believe it was the intention of NER to "fool" anyone. Arborists for the most part don't care what their throw line weighs (so long as its a throw line and not a climbing line). So long as its relatively light and will follow the weight up without adding much drag. NER probably did not envision hammockers making hammock suspension out of it, nor is it marketed to the UL crowd. So to assume they need to be dead nuts with their weight accuracy is a little asinine.

    Dynaglide promised to be at or above 4 digits in breaking strength.
    I havent seen anywhere a rating above 1000 pounds. So above is a stretch. And since its marketed solely as a throw line, I fail to see the need for average AND minimum strength.

    Why was Dynaglide ever used for suspensions?
    Why did Edison keep trying after so many failures?

    Not every question needs an answer and furthermore the answer to every question wont jive with everyone a the same time. Just because it appears to not make sense to you, doesn't mean its not right for someone else.
    Last edited by opie; 07-29-2011 at 09:04. Reason: horrendous spelling
    I am not a gram weenie. , But Im starting to see the merits!!!

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  3. #23
    Senior Member DemostiX's Avatar
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    Quote Originally Posted by DemostiX View Post
    I wonder where 3 for 17 (grams) came from?!!

    For calibration and mnemonic reasons combined, maybe the best calibration unit for central North Americans is a stack of US 5 cent coins, the nickel: For a long time the standard weight has been 5.00 grams.

    Nickel = 5.00 grams.
    I'll answer my own question, and so offer another useful memory device for central North Americans, the one around nickels being close to foreign:

    Five modern quarters, such as the ones Grizz used to check the bias of his scale, weigh so close to 1.00 ounces as to be good enough for all weight-weenies. Folks here with iPad-equivalents in their hammocks at home might confirm that this is why the new weight standard for U$ quarters was set as it was.

  4. #24
    WV's Avatar
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    I like this thread. That doesn't mean I'll refer newbies to it for guidance.

    Thanks, Demostix, for starting and running with it. ("Anything worth doing is worth doing to excess.")

    Thanks, motorapido, for posting what I was going add and saying it better.

  5. #25
    GrizzlyAdams's Avatar
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    for the record...What I like about dynaglide is that it is more compact. The few times I've put it on a hammock for someone else, it has been because he has asked for it, I've asked if he feels comfortable using it, or he is prioritizing weight over anything else. I've not seen any reports here of dynaglide snapping----which it well could do under the right dynamic load, given observed < 1000 lb. breaking points.

    That all said, the difference in strength rating between dynaglide and Amsteel 7/64 is so much more significant enough over the hardly noticeable increase in weight (but distinctly noticeable increase in bulk) in a load region where accidents might happen that Amsteel is what I use to keep my 200 lb bulk in the air and off the ground.

    All the discussion about tree straps fraying and breaking have got me to thinking about upgrading from my 1200 lb test polyester straps, but as bark and a marlin spike toggle are the only things that touch my straps, I've not seen any abrasion, nor are there concentrated force transfer points like you can get with a naive placement of biner or clip (i.e., one that causes the webbing to bend). Probably I'm fine, but next roll of webbing I get will have a higher strength rating.

    My 10 year has a T-shirt I got for him at the gift shop at a rocket museum. It says "The Laws of Physics Do Not Apply to Me." Sadly, the laws of physics apply to everyone, and we all ought to be aware of the significant stresses on materials that hanging induces.



    Quote Originally Posted by DemostiX View Post
    Smoke Bait has joined catenary-curve-calculating Professor Hammock
    hey now, them's fighting words My tracing and cutting skills have more error in them than the difference between a cat curve and a parabolic curve. I'm a parabola guy through and through.
    Grizz
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  6. #26
    in it for the naps oldgringo's Avatar
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    Quote Originally Posted by GrizzlyAdams View Post
    All the discussion about tree straps fraying and breaking have got me to thinking about upgrading from my 1200 lb test polyester straps...next roll of webbing I get will have a higher strength rating.
    Right there with you, Professor.

    Every time someone posts intent to do a suspension on the cheap, I cringe. It's just a matter of time until someone gets really badly hurt.
    Dave

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  7. #27
    Yoda's Avatar
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    Interesting thread, I like the findings, and would like to see if there is a difference between the green and orange as others have mentioned! I agree with WV though I would not point a newbie in this threads direction!
    Formerly known as "Cranky Bear"....

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  8. #28
    TRAVELER's Avatar
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    i guess this is nt going to help much ,but my son weighed his 7ft whoopies when he got them and they were 0.7 grams

  9. #29
    Senior Member more's Avatar
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    Quote Originally Posted by TRAVELER View Post
    i guess this is nt going to help much ,but my son weighed his 7ft whoopies when he got them and they were 0.7 grams
    That's pretty light right there.

  10. #30
    Senior Member JerryW's Avatar
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    Quote Originally Posted by TRAVELER View Post
    i guess this is nt going to help much ,but my son weighed his 7ft whoopies when he got them and they were 0.7 grams
    You might want to check that decimal point. I'm pretty sure you mean 7.0 grams.

    Dynaglide?


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