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  1. #1
    Alamosa's Avatar
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    Constrictive effect of Tree Huggers

    There have been a lot of threads talking about the different impacts of a single line verses webbing verses wider webbing, so I really don't think that needs to be re-hashed here.

    However, in all of the discussions it seems like we focus on the forces of tension applied with the hammock line on the tree. In addition, there has to be a big constrictive effect that is being applied to the tree and hence to the bark and underlying layers.

    So, the question for all of tree experts, from a constrictive force view, is there a big difference to the impact on the tree in the way the line is attached to the tree? This crude chart shows some connection methods (certainly not exhaustive) to be considered in our conversation.

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  2. #2

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    Far from being an expert, I can't see constriction affecting anything serious about the tree's function such as the flow of water and nutrients through it. Maybe some flakey bark might be damaged but that's it (unless a carabiner is squeezed against or rubbing on the bark).

  3. #3
    in it for the naps oldgringo's Avatar
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    The first (leftmost) is how I suspend my tarp...not sure how well it would hold a hammock.

    The remaining two are choker hitches...the one on the far right is preferred, while the center rig will derate the webbing, and in some cases, damage it, leading to failure.

    As for loads, I can't say. That is one for the engineers.
    Dave

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  4. #4

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    Quote Originally Posted by keg View Post
    Far from being an expert, I can't see constriction affecting anything serious about the tree's function such as the flow of water and nutrients through it. Maybe some flakey bark might be damaged but that's it (unless a carabiner is squeezed against or rubbing on the bark).
    Short answer to your question is the left one is probably worst. The right one will induce a twisting slippage force so the middle is probably best as the point where the strap goes tangent to the trunk defines the load area.


    Long answer:
    The problem is crushing the cambium layer under the bark. That is the active growing layer that passes the sap up and down the tree to distribute nutrients. The thickness varies with the tree type and size. If the cell walls collapse recovery after removing the load is not instantaneous. If you want an example of what happens lay your hammer on a wood scrap. Then back off and hit the scrap as hard as you can. It gets obvious from there.

    The problem created is the amount of force in a given area. For a fixed load, you in your hammock. Whatever is wrapped around the tree sets the area. The wider the line/strap the lower the area load. Skinny lines like amsteel don't have much area so when you divide that by your weight the number can get very high. Conversely when you use a strap the area is much bigger so the load for a given area is much lower.

    This is further complicated by the idea that force distribution is not around the whole tree. something more than 1/2 the diameter gets most or all the load.

    The real world practical side is putting a 50 lb kid in a hammock with no slings is probably a non issue. When 300 lb dad sits on the hammock the picture changes radically.

    Probably some of the smaller folks can pick big trees with no real damage. OTOH the bigger the person and the smaller the tree the higher the unit load and the more likely to cause a problem. The safe answer is to use a strap and not worry about it.

    There is an ancillary issue with very small tarp ridge lines. Same idea plus wind load on the tarp.

  5. #5
    bonsaihiker's Avatar
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    I feel the need to offer some perspective on this topic. I have dealt with the cambium layer many times with my "other" hobby. Tree cambium is pretty resilient stuff. Yes, it is only one cell layer thick, but this cell layer can regenerate to an amazing degree. In bonsai, air layering is a method to propagate plants in which you remove the cambium layer in a ring around the branch, then surround it with a moist medium and wait for hormones from the leaves to generate roots at the girdled section. In theory it's simple, but in practice it can be difficult to achieve success. This is due to the resilience of the cambium. If you miss removing even the slightest "bridge" of green, the wound will heal over and you will get no roots. If you don't make the wound large enough, the cambium will meet as it heals from either end and, once connected, will proceed to heal the entire wound. I've had a wound close and the layer fail on a 3-inch diameter dogwood which had (I thought) ALL the bark and cambium removed in a 3-inch strip all the way around the tree. One year later I removed the medium as I had not yet found roots, and found...bark. Now, the procedure did leave a scar there (I'll try again someday), but you wouldn't notice it outside of 10 feet away. More importantly, the tree never skipped a beat and showed no problems whatsoever during the entire time it was girdled.

    Having said all that, I don't worry about using tree straps. I deploy mine in the third method above, as per Dutch's instructions (I use Dutch Clips), more to avoid stressing the clip than worrying about the tree. I don't see any reason to use line only, but if I did I would expect more surface damage to the bark (which is dead tissue) than to the cambium (unless the bark is very thin) which is also unacceptable from a "leave no trace" perspective.

    Anyway, that's my $0.02.
    --Scott <><

    "I fish because I love to; because I love the environs where trout are found, which are invariably beautiful... because, in a world where most men seem to spend their lives doing things they hate, my fishing is at once an endless source of delight and an act of small rebellion; because trout do not lie or cheat and cannot be bought or bribed or impressed by power, but respond only to quietude and humility and endless patience...." --Robert Traver

  6. #6
    Dos's Avatar
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    you know what bonsaihiker?
    i am going to print out in a word document of your first paragraph of your post
    for any and all park rangers who have an issue with me hanging.

    ty

  7. #7
    Senior Member Captain Smiley's Avatar
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    Okay, I'm good now. I can count on my 2" seatbelt tree straps causing absolutly no damage and leaving no trace whatsoever. I'm a happy hanger indeed. Thanks Bonsaihiker, youdaman!
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    Anything else cost far too much.

  8. #8
    Senior Member Jsaults's Avatar
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    I believe that SOME constriction is needed

    Otherwise there is a tendency for the dudpension straps to want to slide down the tree (as in the first drawing). probably not an issue with oak trees having rough bark, but might damage smooth-barked varieties.

    Then again, I am not an arborist so I am just pondering this from a layman's viewpoint.

    But something that does concern me is the use of Zing-It for tarps, combined with Tarp Flyz or figure 9s where a tug "saws" the 1.75mm line across the tree's bark. Again, rough bark probably holds up reasonably well, but I am sure that smooth barked trees can be damaged. I have been threading 2 or 3' piece of stripped 550 cord over my tarp tie-outs to act as a buffer between the Zing It and bark. Maybe overkill, but I sleep well.

    Jim

  9. #9
    Alamosa's Avatar
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    Thank you everyone for your comments. I know we have a lot of other threads that deal with the thin line vs. web issue, so I did want to stay away from that completely here.

    It is just more of the tourniquet effect on the tree that was interesting me. With the strap either going through a loop, biner, clip, etc., it becomes a constrictor around the tree that we are applying 100 - 1000 lbs of force to (depending on hang, angles, hanger, etc.).

    Now I know we have had lots of mentioning of trees growing through wire, nails, etc. It reminds me of the ladies who have worn their wedding rings so long that they can not take them off. Their fingers have grown around the restriction, but in that case, the restriction stayed the same size and the finger slowly grew - much like wire wrapped around a tree that eventually gets embedded.

    Take a wire and wrap it that tightly around another finger and apply a force to it and you would have a tourniquet that would quickly kill the finger.

    Now if the cambium layer is tough enough that this constriction for a relatively short period of time (a few nights) is not an issue, as bonsiahiker mentions, then that is a good thing.
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  10. #10
    in it for the naps oldgringo's Avatar
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    As in so many things, the gap between what I think and what I know is wide and deep.
    Dave

    http://www.uark.edu/misc/xtimber/rna/pattonsbluff.html

    It has always been my private conviction that any man who pits his intelligence against a fish and loses has it coming.
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