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  1. #21

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    Quote Originally Posted by cmoulder View Post
    Empirically, perhaps one could make a rough, direct measurement using a luggage scale to tug the straps right where they contact the tree. With somebody in the hammock, of course. Which would require me to find someone almost as insane as I to assist.

    The more I ponder it, however, the less inclined I am to be worried about it unless using marginally rated straps.

    I suppose your professional colleagues have some simple formula to calculate actual number. In my little doodle below, assume that the hang angle in both cases is a perfect 30° and that the tree is 1 foot diameter.
    I decided to nerd out a bit this morning and ran some quick numbers and for force in the strap you are 100% correct.

    I made the free body diagram below though I used the angle between the straps rather than the angle off the tree as that will depend on the size of the tree as well. This is just for the union of the straps. If you isolate that section (what a free body diagram is) the forces in x and y
    have to be equal or the system will be in motion (unbalanced force = acceleration). And hopefully nothing is moving. It is pretty straight forward statics which is really vector calculus which is mostly trigonometry. To get the force in the two legs of the strap sine is used.

    https://www.hammockforums.net/galler.../3/8/5/fbd.jpg


    I dumped this in excel and made the following graph of force in the strap vs. angle for a 200lb load. How this equated to a person’s weight is a different matter and though about a 30° hang the load in each strap is about the same as the persons weight even though there are two of them but by the same rules above it ends up doubling the vertical load (sin of 30° is 0.5).

    https://www.hammockforums.net/galler...e_vs_angle.jpg


    For the load on your strap itself, this angle is pretty important. And for the constriction on the tree. I wonder what the strap ratings mean when they say up to '400lbs'. I am guessingthey mean 400lbs tensile load per strap. Though if I ran these same numbers for a 400lb person the numbers here would be doubled. Inthiscase,i you cinched your straps tight (140°) the load in the strap itself would be 600lbs.

  2. #22

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    Quote Originally Posted by cmoulder View Post
    Empirically, perhaps one could make a rough, direct measurement using a luggage scale to tug the straps right where they contact the tree. With somebody in the hammock, of course. Which would require me to find someone almost as insane as I to assist.

    The more I ponder it, however, the less inclined I am to be worried about it unless using marginally rated straps.

    I suppose your professional colleagues have some simple formula to calculate actual number. In my little doodle below, assume that the hang angle in both cases is a perfect 30° and that the tree is 1 foot diameter.
    I decided to nerd out a bit this morning and ran some quick numbers and for force in the strap you are 100% correct.

    I made the free body diagram below though I used the angle between the straps rather than the angle off the tree as that will depend on the size of the tree as well. This is just for the union of the straps. If you isolate that section (what a free body diagram is) the forces in x and y
    have to be equal or the system will be in motion (unbalanced force = acceleration). And hopefully nothing is moving. It is pretty straight forward statics which is really vector calculus which is mostly trigonometry. To get the force in the two legs of the strap sine is used.




    I dumped this in excel and made the following graph of force in the strap vs. angle for a 200lb load. How this equated to a person’s weight is a different matter and though about a 30° hang the load in each strap is about the same as the persons weight even though there are two of them but by the same rules above it ends up doubling the vertical load (sin of 30° is 0.5).




    For the load on your strap itself, this angle is pretty important. And for the constriction on the tree. I wonder what the strap ratings mean when they say up to '400lbs'. I am guessing they mean 400lbs tensile load per strap. Though if I ran these same numbers for a 400lb person the numbers here would be doubled. In this case, if you cinched your straps tight (140°) the load in the strap itself would be 600lbs.


    Not sure why the images ended up so small. For being an engineer I am frequently pretty bad with technology. I guess that makes me an old engineer...

  3. #23
    Senior Member cmoulder's Avatar
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    Ha! Thanks for figuring that out. I actually do love graphs... after someone else has done the heavy lifting to crunch the numbers.

    Yeah, I think those webbing ratings are all 'straight' tensile strength, independent of extra force from loading angle and loss of strength from knots, hardware, etc. Hence the generic 5x rating recommendation for suspension. And why I'm going to be reeeeeally careful with those 900lb straps.
    Five Basic Principles of Going Lighter (not me... the great Cam Honan of OZ)
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  4. #24
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    Quote Originally Posted by cmoulder View Post
    Ha! Thanks for figuring that out. I actually do love graphs... after someone else has done the heavy lifting to crunch the numbers.

    Yeah, I think those webbing ratings are all 'straight' tensile strength, independent of extra force from loading angle and loss of strength from knots, hardware, etc. Hence the generic 5x rating recommendation for suspension. And why I'm going to be reeeeeally careful with those 900lb straps.
    Good reason to run the strap straight off the side of the tree and let the friction of the wrap ease any stress on the securing end.

  5. #25
    Senior Member cmoulder's Avatar
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    Quote Originally Posted by TominMN View Post
    Good reason to run the strap straight off the side of the tree and let the friction of the wrap ease any stress on the securing end.
    That's what Dutch recommends for the Dutch Clip.



    For me, it makes it awkward to also align the tarp ridge line off to the side so I'll continue centering the knots on the tree.

    Plus, when I've actually tried this with a Dutch clip and with knots, there's still a tendency for the knot to center itself on the tree when under load, especially with trees that have smooth bark.
    Five Basic Principles of Going Lighter (not me... the great Cam Honan of OZ)
    “If everybody is thinking alike, then somebody isn't thinking.” ~ Gen. George S Patton

  6. #26
    Senior Member jcksparow's Avatar
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    When tree girth and spacing allows, I usually double wrap around the tree for all the reasons others have listed. Less likely to slip when I first load the hammock, and it always seemed like a good idea to spread the load on the tree over as large an area as possible. Started getting into that habit after I hung in a Virginia State Park that required 2" straps (which I didn't have) and they allowed me to wrap my 1" straps 2-3 times instead. Plus I carry fairly long straps for my primary suspension, and wrapping the tree a few times is a nice way to use up some extra length so the webbing isn't dragging on the ground.
    "Now and then we had a hope that if we lived and were good, God would permit us to be pirates." -Mark Twain

  7. #27
    Senior Member cmoulder's Avatar
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    Quote Originally Posted by jcksparow View Post
    When tree girth and spacing allows, I usually double wrap around the tree for all the reasons others have listed. Less likely to slip when I first load the hammock, and it always seemed like a good idea to spread the load on the tree over as large an area as possible. Started getting into that habit after I hung in a Virginia State Park that required 2" straps (which I didn't have) and they allowed me to wrap my 1" straps 2-3 times instead. Plus I carry fairly long straps for my primary suspension, and wrapping the tree a few times is a nice way to use up some extra length so the webbing isn't dragging on the ground.
    Looks as if you've been doing the right thing all along. It has given me some food for thought, at least.

    Funny thing, when I was playing with the other single wrap and V adjustment and so forth I also did the double wrap and it ended up kinda wonky. So I'll have to play with that some more. But maybe you've encountered this and have a suggestion or 2!

    Five Basic Principles of Going Lighter (not me... the great Cam Honan of OZ)
    “If everybody is thinking alike, then somebody isn't thinking.” ~ Gen. George S Patton

  8. #28
    Senior Member tflaris's Avatar
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    I use this method but I have a HH

    https://youtu.be/YcVcKdt1P10


    Sent from my iPhone using Tapatalk

  9. #29
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    Quote Originally Posted by tflaris View Post
    I use this method but I have a HH




    Sent from my iPhone using Tapatalk

    There sure are a whole lot of ways that easier and more user-friendly, especially when it comes time to tweak the suspension.

  10. #30

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    Quote Originally Posted by cmoulder View Post
    Looks as if you've been doing the right thing all along. It has given me some food for thought, at least.

    Funny thing, when I was playing with the other single wrap and V adjustment and so forth I also did the double wrap and it ended up kinda wonky. So I'll have to play with that some more. But maybe you've encountered this and have a suggestion or 2!

    That would be three wraps under my terminology (mileage may vary). And that is what I was referring to with the three wraps being a pain to adjust the height. Walking the loops up the tree is a tedious process.

    as for the HH tree straps, I have an HH as well as my WB though I switched the suspension to a continuous loop with becket straps from WB as I liked them so much better. I have now been down the hammock path for only a few months and already own two and think of trying out a ridgerunner. And been contemplating learning to sew as I really like my BB XLC but it could be a couple inches wider. I’m going to start with a gear loft for the HH my partner uses. I can do hand cut dovetails. Sewing can’t be that much harder.

    And FWIW, I will never go back to being a ground dweller unless the situation requires it. I know I am preaching to the choir here but the hammock is vastly superior. I am just disappointed it took me 52yrs to figure that out.
    Last edited by Sean McC; 09-16-2021 at 16:51.

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