a brief primer on the hang angle
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- เผยแพร่เมื่อ 19 ต.ค. 2024
- The stress on a hammock suspension depends on the 'hang angle', the angle of the cord from hammock corner to the tree relative to the horizontal line. Professor Hammock uses graphical demonstration to explain why it is that shallower hang angles induce greater stress. Watch the video to get brief visual primers on force, vectors, and statics which together lead to the demonstration.
Wow, finally an answer that totally explains and demistifies this magic 30° angle. Thanks for taking the time and explaining so profoundly.
I loved this video very much as it clarifies the concept of the main forces involved in hanging a hammock in an intuitively accessible way that is really easy to understand. Thank you for taking the effort.
Thanks for watching!
I've always had to work hard at math, but with the hammock example it makes perfect sense! Thank you!! I love getting these explanations.
I'm also assuming that the trig rules applies to a non-continous ridgline(desired sag). I hope I asked that correctly.
Wow, I did not know the thumb/finger/angle trick! Thank you!!!
I was pretty amazed when I first saw it pointed out. Of course, the problem always is that the angle you want to measure takes form only after you're laying on your back in the hammock .... you need a friend to do the eyeballing
I guess it is better not to form a pistol but rather stretch out all you four fingers to the front, since this gives them a more stable position towards your thumb.
My math kept telling me that a wall can handle the force pulling it out if I put an eye in a reinforced stud. Now, I watch this and start to worry again. Thanks again for the video!
I think there is a body of experience suggesting that eyebolts in studs are OK, but yeah, your connection points need to be at a distance relative to the length of your ridgeline and ceiling height to not induce a flat hang angle. If your space is amenable to it you can finesse the issue pretty well by suspending a rail like you see in self-supporting hammock stands. The rail gets suspended (force straight down) from the walls (or ceiling), the hammock get suspended from the rail, and those nasty compression forces are taken up by the rail, not the walls or studs.
I got it! So I'm about halfway through but I just came up with a little limerick for myself.
"In my hammock the force of my gravity multiplies the same number of times as the run of my cord is over its rise."
It's a little clunky but feel free to improve on it and take it!
Thanks for the inspiration, this problem has been driving me crazy because I didn't know how to do the trigonometry and figured it had something to do with a sign angle and blah blah blah blah blah blah blah I just couldn't get an estimate in my head. Feel free to let me know if I'm way off base here, but I feel like as long as my run is 3X my rise, and I am 200 pounds, and my para cord doesn't really break till 800 pounds, then I'm fine! If I don't move too much :P
10:20 is what you are looking for
Thank you for this video. Very good stuff! Easy to follow explanation of the matter...
great, thanks for watching and commenting!
How would this look with a structural ridgeline? The line angle from the tree could change at the point where the ridgeline is connected, especially with lower hang angles.
Would the vectors stop at the ridgeline?
yes, it changes, it is more complex, you do a cancelation of forces model where the rope to the tree, the ridgeline, and the rope to the hammock come together. I _intend_ to make a video on the structural ridgeline...but don't hold your breath..
Excellent explanation! One of my favorite authors, Isaac Asimov, had a way of explaining the most complex ideas in a manner that was easily understood by laymen. I'm certain that he would have enjoyed this video. If you have not read it, you might enjoy one of his books, The Ends of The Earth ( it's non fiction).
Joel Braswell... thanks! Much appreciated. It will not surprise you that Asimov is one of my favorites too; I am honored by the comparison.
What about 40,45 and 50° if 30 is not possilbe because of space?
You'll need a titanium step-ladder to attach high enough to attach so that angles this steep pull the ends apart. At least, that's what my thought experiment tells me....
The more obtuse the angle the less stress you put on your lines.
A marvelous job of illustrating the concept! Thanks for taking the time and effort. There's so much misunderstanding out there on this. Maybe for part deux you could add a structural ridge line which is a whole nuther can of worms.
Indeed, I had intended to do more talking about loading a suspension that has a structural ridgeline with tension before even getting the hammock. I originally intended to cover sheer. But my gut feeling in the end was to keep it simple. Would like to carry on with real hammock and suspension and measurements. All I gotta to is stay at home long enough to work in the filming! Thanks for watching
About two years ago, I have made a hammock calculator that includes the forces on the structural ridgeline and the hammock body.
If you are interested, you'll find it here: docs.google.com/spreadsheets/d/1Yu9Reh3w5IZZLzn2vg6pjzFP3cIrhOcZpXsnzAHDA4I/edit#gid=1509228599
In case, you prefer metric measurements, use this version: docs.google.com/spreadsheets/d/1BMXKUdT-25tV-WqfkNcM3wPCmQL9pEOHF9eXkTO-CTs/edit#gid=1509228599
Great video! Just a quick word about the graphic at 7:47 : I think that this is a bit misleading. The "force on suspension" label looks like it is applied to the wrong vector; it should be the tension in the suspension which is drawn as the red vector parallel to the suspension line pointing away from the mass. Stings, ropes, thin cables, etc. to within a pretty good engineering approximation can only carry tension forces (not shear or compressing) so any force in the suspension lines must be parallel to the lines. But nice video to walk everyone through some basic high-school physics that they may have never had, or which they may not remember.
Oh, OK, I see you're using the other suspension cable and summing the vectors. Please ignore me! Thx
I see you got the intent later. Glad you appreciated the approach. Vector pictures really help illustrate the underlaying concepts.
Grizz, because the hang angle is pretty much defined by the depth and span of the catenary curve of my ariel (in my case it comes out at 23.4 degrees), can you think of a more elegant design solution for a bridge to reasonably approach 30 degrees? Would a deeper curve or a shorter span in my next iteration be "better", or is that 126% on my amsteel a reasonable trade-off for my perfect hammock lie?
Go with what you've got. I didn't get into it in this video but I find that a shallower angle (approx. 25 degrees) is needed for a proper hang with a bridge hammock, at least one of mine. So your experience is the same as mine. Amsteel with a working load of over 1000 lbs can take it, no problem.
Thank you, sir. I'll continue to rest easy with my Robin Goodfellow. It's good to see new wisdom contributions from you again.
Hammock tension multiplies the same as it's run over it's rise.
Great video, but as a historian there is no way I would be able to sleep in my hammock thinking of math!
the math is there to put you to sleep....
This video was made to teach Tinny from Minibulldesigns about hang angles.
Ahhh, now I know why 30 deg, thanks for that,
now if we can just figure out the basis for the rule of thumb suggesting the ridgeline be 83% of the hammock length...actually, it might be related to this 30 degree rule. Perhaps if you're laying flat in a hammock whose ridgeline is 83% the length of the hammock then the hang angle of the hammock body is about 30 degrees. Maybe...
83% of 10 foot 9 7/8 inch's = er...83% of 3.3m = 2.73m... boom, a win for us metric fools :)Just for our American cousins who don't like metric, unlike the good professor, that's 129.875 inch's. Off the top of me head !
Well, in fact, the cosine of 30° would lead to 86.6% of the hammock length for the length of the ridgeline. However, since we want to have a certain amount of tension on the ridgeline, we are going to shorten it a bit: around 83% seems to be a good starting point.
AWESOME!
(degreed engineer)
30 degree engineer?