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  1. #1
    Senior Member SGT Rock's Avatar
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    Random thoughts: a case for smaller tree straps?

    Howdy all. I haven't been posting much because I have been working a ton of hours lately. It's nice to still have a job considering...

    Anyhow, while I was working about 90 hours last week a spark of a thought crept into my head about tree straps. It was probably ignited by a set of Dutch's new Dutch Clips I got in the mail. And before I start I must say there is a good chance what I am saying isn't correct because I am not an engineer. It is also probably going to be a little controversial for some because it pokes at the conventional wisdom - but I do that a lot and have been successful with things other folks said would never work.

    So this it: maybe 1/2" wide tree straps are better than 1" wide straps.

    There I said it.

    Now follow this logic. It may be flawed...

    Imagine your single line load is about 200lbs and you have the choice to use A) 1" strap 6' long, B) 1/2" strap 12' long. They both weigh the same in this thought experiment, so there isn't any real weight advantage. The mass should also be about the same too, so no space savings inside your pack going either way. So which is better for the trees?

    Ask me two weeks ago and I would have said A. Now I'm not so sure.

    If your load is 200 lbs on the line, then the surface area of the strap distributes it over the outside of the tree. So if your tree is 22.93" in diameter, that means the circumference is going to be roughly 72". With strap A you can wrap it around once, which means you have 72" of surface area for the strap. That would be about 2.77 lbs/in^2 under the strap. Not bad for the tree at all. Lets say you used strap B but wrapped it around the tree twice - still 72" of surface area so the weight per in^2 is still the same. The 1/2" strap is just as safe for the tree, you just have to wrap more.

    Lets say you are stuck with a tree 11.48" in diameter. The circumference is now just slightly over 36", so you can only get one wrap with the 1" strap, and the surface area is just slightly over 36", so you are now putting about 5.55 lbs/in^2 on the tree. Still not bad. But if you used a 1/2" strap you can wrap the tree three times! That means your area is now 49" of area and the weight on the tree is only 4.08 lbs/in^2 - the 1/2" wide strap actually protects the tree better than the thicker strap. Hmmm....

    The math also has other interesting breaking points like at 7.7" diameter you put 4.15 lbs/in^2 with the 1" strap with 2 wraps max, but the 1/2" strap can get 5 wraps and is down to 3.35" lbs/in^2. At 45.8" diameter (that is a BIG tree) you cannot even begin to get around it without using some sort of extender, but the 1/2" strap can get around it once. And with all that area covered, it only puts 2.77 lbs/in^2 on the tree. A couple of weeks ago I wouldn't dream of hanging off a 1/2" strap on any tree, but now if I were to go to some redwood forest I would probably make some big honkin' 1/2" straps.

    OK, so I admitted I am not an engineer, so there may be some flaw with my math somewhere. I know this also doesn't take into account for some overlap of the wraps which is going to happen at some points with either strap - so there is the real world factor that would change some of these numbers.

    So what are your thoughts?
    Last edited by SGT Rock; 08-27-2012 at 08:19. Reason: misspelling - been up for 24 hours, sorry about that.
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  2. #2
    Very interesting and insightful SGT Rock...My only question for now (need to give this more thought) is how much force is applied with only "1" wrap of the 1/2" webbing? Sorry I stink at math so I won't even attempt to figure this out!

    I ask as most that use straps only do a one wrap and go, so this may be ingrained in our heads and if such a thing were to be done (remember repetitive training and muscle memory) what would happen? Would this actually damage/hurt the tree somehow? When we get in our hammock and shift around (or attempt Shug like acrobatics) would this cause damage or hurt the tree?
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  3. #3
    Senior Member angrysparrow's Avatar
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    I don't doubt that some of your observations are correct, especially concerning multiple wraps distributing the suspension load over a greater surface area.

    I think where it may break down a bit is simply in observation by others. Or partial observation, as it were. How many people are going to see that you're using 1/2" straps, and think that's all that they need to use even with smaller trees... With the push towards more minimal suspensions, I've no doubt that it wouldn't be long before someone started using only 1/2" straps that were as minimally short as some of the 1" straps that are carried now. That might work just fine on larger diameter trees, but would probably leave scars on smaller ones.

    I've never heard anyone argue that 1" webbing is any kind of optimized standard that is the best ratio of strength vs surface area. It was more a matter of hammockers using materials that were at hand, rather than developing a standard. But, by erring on the side of caution with slightly wider straps, it makes a good case for hammocks to be observed as LNT-friendly to land managers and park-staff. That seems like a small price to pay for good relations.

    Again...no doubt that 1/2", used correctly, is enough for some situations. But carrying a slightly wider strap (and encouraging others to do the same) might be better for hammockers at large, as they gain acceptance in more settings.

    JMO
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  4. #4
    Moderator Nighthauk's Avatar
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    Sgt. Rock I have a basic understanding of what you are talking about. And while you are probably theoretically correct on the math, I think there is one issue missing. While your math indicates the full length of the strap and the pressure spread out amongst the full length, I believe that you will not get equal pressure the full length due to friction. So you would still have a greater psi on the 1/2" strap initially no matter how many times you wrap the 1/2" around the tree then you would with the 1" strap.
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  5. #5
    Senior Member ShadowAlpha's Avatar
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    I have no clue math is not my friend. Wanted to say HELLO! Gotta work when u have it. That's what I been doing.

    1/2" straps sounds good!

  6. #6
    Senior Member SGT Rock's Avatar
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    Quote Originally Posted by Cranky Bear View Post
    Very interesting and insightful SGT Rock...My only question for now (need to give this more thought) is how much force is applied with only "1" wrap of the 1/2" webbing? Sorry I stink at math so I won't even attempt to figure this out!

    I ask as most that use straps only do a one wrap and go, so this may be ingrained in our heads and if such a thing were to be done (remember repetitive training and muscle memory) what would happen? Would this actually damage/hurt the tree somehow? When we get in our hammock and shift around (or attempt Shug like acrobatics) would this cause damage or hurt the tree?
    It depends on the diameter of the tree really. The bigger the tree, the less it affects it. Once I started thinking about this it made sense based on my observations. I'll answer the question using a few different diameters...

    Lets say we have the tree we could wrap around 5 times: the 7.7" diameter tree. So 7.7 x 3.14 = 24.18" circumference. Since the strap is only 1/2" wide that would mean there is only 12.09" of surface area under the strap to distribute the load. 200/12.09 = 16.54 lbs/in^2. Is that enough to hurt a tree? I don't know that answer and it would probably vary by tree. I'm going to guess on a tree that small you would want to wrap multiple times anyway. I already do.

    At 22.93" diameter the circumference is 72", and the area is 36". So the load would be 200/36 = 5.55 lbs/in^2, you are probably not going to hurt that tree.

    At 11.48" diameter the circumference is slightly over 36", so the area is only going to be about 18". That means the load would be about 200/18 = 11.11 lbs/in^2. I'm guessing this is going to be about where the breaking point for load is generally going to be. at this diameter this is my general go-to size for most hangs, and I'm going to say at this diameter I would wrap twice at least. But would that load hurt the tree? I don't know.

    At 22.96" diameter you would have to only wrap once with these straps I am using in the example. At that diameter the load is going to be 5.55 lbs/in^2.

    All that said, this is only true if my model is correct. When calculating ground pressure you divide the load by the surface area covered. I imagine that for a strap load on the tree the same math would apply.
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  7. #7
    Senior Member SGT Rock's Avatar
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    Quote Originally Posted by angrysparrow View Post
    I don't doubt that some of your observations are correct, especially concerning multiple wraps distributing the suspension load over a greater surface area.

    I think where it may break down a bit is simply in observation by others. Or partial observation, as it were. How many people are going to see that you're using 1/2" straps, and think that's all that they need to use even with smaller trees... With the push towards more minimal suspensions, I've no doubt that it wouldn't be long before someone started using only 1/2" straps that were as minimally short as some of the 1" straps that are carried now. That might work just fine on larger diameter trees, but would probably leave scars on smaller ones.

    I've never heard anyone argue that 1" webbing is any kind of optimized standard that is the best ratio of strength vs surface area. It was more a matter of hammockers using materials that were at hand, rather than developing a standard. But, by erring on the side of caution with slightly wider straps, it makes a good case for hammocks to be observed as LNT-friendly to land managers and park-staff. That seems like a small price to pay for good relations.

    Again...no doubt that 1/2", used correctly, is enough for some situations. But carrying a slightly wider strap (and encouraging others to do the same) might be better for hammockers at large, as they gain acceptance in more settings.

    JMO
    I sort of agree with this. Although I do think 1" is probably pretty optimal even if it wasn't the most handy stuff around. 7lbs per square inch isn't a lot of pressure.

    And I do see the point of the minimalist taking it to far, it is always a temptation to cut some grams.

    But on the other end of it, if the truth was a 1/2" strap is actually better for the tree than a wider strap, then wouldn't it be better to actually use it and educate people about it? Seems like using them for appearances sake is less in line with actual leave no trace ethics.

    Quote Originally Posted by Nighthauk View Post
    Sgt. Rock I have a basic understanding of what you are talking about. And while you are probably theoretically correct on the math, I think there is one issue missing. While your math indicates the full length of the strap and the pressure spread out amongst the full length, I believe that you will not get equal pressure the full length due to friction. So you would still have a greater psi on the 1/2" strap initially no matter how many times you wrap the 1/2" around the tree then you would with the 1" strap.
    I've thought of that. I think there is probably a mechanical advantage at some points, especially if you are using some ring/buckle designs where folks have the buckle against the tree. Or maybe where there is some sort of metal "fulcrum" for lack of a better term. The friction would also be a factor since the tree bark will grip the strap. BUT if you have a single wrap, this friction would be focused on smaller areas since you don't have a lower friction surface to act against. If you have multiple wraps where a few start to overlap each other, then the top straps, where you are most likely to have the most force, are allowed to slide easier over the other strap material which will actually relieve the stress. I think that is true anyway. I'd like to design an experiment to test this but have no idea how to do it.


    Quote Originally Posted by ShadowAlpha View Post
    I have no clue math is not my friend. Wanted to say HELLO! Gotta work when u have it. That's what I been doing.

    1/2" straps sounds good!
    Work is good. Especially because just a month ago I was supposed to get laid off.
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  8. #8
    Senior Member Mustardman's Avatar
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    Your model is incorrect - the vast majority of the force will be on the first wrap, due to friction as mentioned before. The multiple wraps afterward will primarily help keep the strap from rotating around the tree, and not bear nearly as much of the weight.

    It's an easy experiment to try - take two small digital scales, wrap a strap around something large with a decent amount of friction and over one scale on each wrap, and look at the forces.

  9. #9
    Senior Member SGT Rock's Avatar
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    Quote Originally Posted by Mustardman View Post
    Your model is incorrect - the vast majority of the force will be on the first wrap, due to friction as mentioned before. The multiple wraps afterward will primarily help keep the strap from rotating around the tree, and not bear nearly as much of the weight.

    It's an easy experiment to try - take two small digital scales, wrap a strap around something large with a decent amount of friction and over one scale on each wrap, and look at the forces.
    Well I'm not sure. If the first wrap was done under load it would be true, but if the first wrap or two is fairly loose, then the top one starts getting the load and would have to somehow work that load down. Depending on the friction that wouldn't necessarily happen.

    As to the scale, I don't have a digital scale that goes up that high. Mine max out at around 3 pounds. But putting a scale under the strap would create an uneven distribution of pressure wouldn't it? Wouldn't that point that the scale pokes out have a higher pressure than the rest of the wraps?
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  10. #10
    Senior Member angrysparrow's Avatar
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    Quote Originally Posted by SGT Rock View Post
    But on the other end of it, if the truth was a 1/2" strap is actually better for the tree than a wider strap, then wouldn't it be better to actually use it and educate people about it?
    Sure. But it's not quite there yet.

    Quote Originally Posted by SGT Rock View Post
    Seems like using them for appearances sake is less in line with actual leave no trace ethics.
    It's not 'for appearance sake'. The wider the straps, using the same number of wraps, the more surface area they cover. That's beneficial for the trees, and in turn for LNT.

    Sadly, many hammockers aren't educated about LNT (and probably won't be). But they do follow and use the same gear and techniques that they see others using... So, by simply promoting gear that is LNT friendly...some of it rubs off.

    I'm not making a counter argument to using or exploring 1/2" webbing. I'm just saying that there's probably an education component to it, and it will be missed by some observers.

    Looking forward to seeing your tests.
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