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  1. #31
    Senior Member trekkingnut's Avatar
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    Quote Originally Posted by Youngblood View Post
    I don't think most of us understand the phrase "cross loading the spine on the crab". By 'cross loading' in this case, I assume you mean something like 'bending in on/around the tree'. 'Spine' seems pretty easy-- along the length of the carabiner. 'Crab', that one I would guess would just exclude the gate on the carabiner, or saying it another way, would just be the cast or forged piece of the carabiner?

    But I get the gest of what you are saying and have the same concerns myself, especially when folks start using lighter and lighter weight carabiners, or carabiner replacements. One of the carabiner replacements looks basically like a machined aluminum, gate-less carabiner. Regardless, it seems that the more times you cross load, or bend, these carabiners the more you weaken them as most everyone is familar with the concept of metal fatigue and has probably intentionally broken some wire or flat piece of metal be repeatably bending it back and forth. Do climbers replace carabiners after so many uses like they do climbing rope?
    the lightness of the crab shouldnt make much difference, its just lighter because new materials have been used and newer techniques that allow the tensile strength to be higher but the overall weight to be less...

    I know climbers who have used the same carabiners for years and years.... i've never seen one break... though there are pictures of broken ones on the net, generally from incorrect loading... so i really cant answer that question exactly... i know that i wont be replacing any of mine any time soon...

    it is possible that if you are using an aluminum carab that if you drop it then it could form a micro fracture and this would severely weaken it... this isnt possible with steal... so if its something that bothers you, maybe sacrifice the weight a tiny bit and go for a steal one instead?

  2. #32
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    Quote Originally Posted by trekkingnut View Post
    the lightness of the crab shouldnt make much difference, its just lighter because new materials have been used and newer techniques that allow the tensile strength to be higher but the overall weight to be less...
    I was referring to cases where they are lighter with less strength than climbing rated carabiners, not cases where they were lighter with equivalent strength.
    Youngblood AT2000

  3. #33
    Senior Member Jsaults's Avatar
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    Worst case scenario

    This drawing represents, in my estimation, a worst case scenario. Lets assume that:
    1. Treee is 6" in dia.
    2. Weight applied to the suspension line is 200# (hanger weight @ 30 degrees from horizontal)
    3. The tree supplies NO friction to the webbing (I know, I know - how does the web stay up? Magic!)

    I am not going to dabble in physics (not qualified!) but it seems to me that in example B the load to the carabiner's minor axis cannot be very great - at most, 200# divided between the backbone and the gate.

    ANyway, there is a lot of anecdotal evidence that this system works. (Yes, I know that "The plural of anecdote is not data). My only reservation, coming from a Big Guy is that I will not use wire-gate 'biners.

    Jim

    Edit: Here is what the loading looks like using Slap Straps. Note that the 'biner is taking the load through it's major axis.
    Attached Images Attached Images
    Last edited by Jsaults; 07-29-2010 at 12:00. Reason: better diagram

  4. #34
    sclittlefield's Avatar
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    Quote Originally Posted by Youngblood View Post
    I was referring to cases where they are lighter with less strength than climbing rated carabiners, not cases where they were lighter with equivalent strength.
    Here's a good example of they type of biner Youngblood is referring to. I just started carrying non-climbing rated carabiners that are rated to (at least) 1100lbs (4.89kN). They're lighter weight and smaller than most climbing biners, but sufficient for hammock use... IF USED PROPERLY.

    They're sold with this caveat:
    Note: Carabiners are exceptionally strong when loaded in the correct orientation. However, when a carabiner is loaded incorrectly (across its minor axis, with the gate open, over an edge, etc.) it can fail under extremely low loads, even body weight or less. It is critical to place and orient your carabiners correctly.
    DIY Gear Supply - Your source for DIY outdoor gear.

  5. #35
    jons4real's Avatar
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    Quote Originally Posted by PapaSmurf View Post
    Here's a photo that might help explain.


    The above photo was used from this source.
    http://alpineinstitute.blogspot.com/...-on-trees.html
    Thanks for the picture, you cleared it right up. I can't imagine why someone would ever load a biner that way????
    "What one Man can do, another can do!"
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  6. #36
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    Quote Originally Posted by Jsaults View Post
    This drawing represents, in my estimation, a worst case scenario. Lets assume that:
    1. Treee is 6" in dia.
    2. Weight applied to the suspension line is 200# (hanger weight @ 30 degrees from horizontal)
    3. The tree supplies NO friction to the webbing (I know, I know - how does the web stay up? Magic!)

    I am not going to dabble in physics (not qualified!) but it seems to me that in example B the load to the carabiner's minor axis cannot be very great - at most, 200# divided between the backbone and the gate.

    ANyway, there is a lot of anecdotal evidence that this system works. (Yes, I know that "The plural of anecdote is not data). My only reservation, coming from a Big Guy is that I will not use wire-gate 'biners.

    Jim

    Edit: Here is what the loading looks like using Slap Straps. Note that the 'biner is taking the load through it's major axis.
    Only fig, C would be acceptable, A & B would cross load. What you do with your hammock is up to you I am only highlighting the incorrect use of how some are using them.

  7. #37
    Senior Member Jsaults's Avatar
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    Acceptable vs Common Practice

    Deer Man, I agree with you that in life-safety terms the only "acceptable" loading is via teh major axis. Carabiners are rated on their monor axis only to show how much strength they might have during an application such as a lead climbing fall.

    But in reality many many hangers use 'biners just the way they are shown in my figures A & B with no failures. In fact, I will buy you a draught of your favorite legal beverage (Guinness? Other?) if any member of HF has suffered a groundfall due to a gate failure on a climbing-rated carabiner.

    Anyone have a gate failure? Now is your chance to pipe up! (And NO, I am only offering to buy Deer Man a draught!).

    Jim

  8. #38
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    Jsaults,

    I agree with you, the chances are very slim but it could happen. it may be a better choice to use a small clevis as this will load in various directions, I am not trying to ban the use of crabs just make people aware of their correct use.

    Whatever method you use enjoy it!

  9. #39
    Senior Member mtncmpr's Avatar
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    What exactly do you term "a gate failure"?
    ...And then one day you find, ten years have got behind you.
    No one told you when to run, you missed the starting gun... "TIME" by Pink Floyd

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  10. #40
    Senior Member Jsaults's Avatar
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    "Gate failure"

    The classic, dangerous form of failure is when in a climbing application a load is applied outwards to the gate, usually causing the notch to distort/shear or the pins to break and allowing a rope to pop out of the carabiner.

    For hammock purposes it would probably be limited to a distortion of the gate/body interface causing the gate to bind or sieze. Even in the case of such a failure as long as there was tension on the suspension straps you would likely not hit the ground.

    As Deer Man noted, such a failure is extremely serious when life safety (climbing, arborist, fall protection) is involved.

    We are on the other end of the spectrum, as evidenced by how small and light Dutch Clips are. Of course, if you are hanging on a cliff or in a tree then it would be prudent to leave the Dutch Clips behind. ANd include a harness!

    Jim

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