Measurement and calculation or practice and theory

**dirtwheels** · 06-18-2012, 13:32

You're right, I had that backwards! But what does utilizing 2 points of attachment do to the equation.

Originally Posted by Ramblinrev

The linked tool does allow you to change the angle. Slide the weight up and down with the cursor. I don't know the physics cause I'm not a mathlete but I have had my supports bend when strung tightly and not bend when I hang loose. All other factors are the same. That says to me the closer you get to horizontal the more stress is placed on the supports. That is consistent with the models presented.

**DemostiX** · 06-18-2012, 13:33

OP: I'm all for discovering with one's own eyes and a fishing scale that a bit of trigonometry is worth learning because the trig predicts so well the distribution of forces, the physics, of the situation.

**gridge** · 06-18-2012, 14:30

Originally Posted by DemostiX

OP: I'm all for discovering with one's own eyes and a fishing scale that a bit of trigonometry is worth learning because the trig predicts so well the distribution of forces, the physics, of the situation.

Tinny did exactly that - using a scale. I think his conclusion was that the angle doesn't make that much difference within attainable angles...

www.youtube.com/watch?v=y_vlngxmxrM

**gmcttr** · 06-18-2012, 14:46

Originally Posted by dirtwheels

Not to be argumentative, but it that is accurate the force on the shoulders of 2 guys carrying a 200 pound guy in a gurney would be about 400 #'s that seems high. Too bad you can't change the angle! Given your linked tool it would seem that an SLS would be a much more efficient way to hang a hammock. By that I mean one could use rope rated to carry less weight.

I think I have a project to try this in a scaled model using a fishing scale to make measurements.

You're missing the fact that "2 guys holding up a girl by her elbows as she holds them tightly by her sides or two guys carrying a couch or 2 guys carrying a 200 pound guy in a gurney" are all examples of the load/force being placed straight down on the support. Suspend any of them by a rope on both ends stretched out between two guys and it all changes.

**Ramblinrev** · 06-18-2012, 15:05

Originally Posted by gridge

Tinny did exactly that - using a scale. I think his conclusion was that the angle doesn't make that much difference within attainable angles...

www.youtube.com/watch?v=y_vlngxmxrM

With all due respect to Tinny... his forte is stoves and for that he is excellent. He is way off base when it comes to hammocks. I wouldn't put much stock in his views on rigging. He just doesn't get it.

**gmcttr** · 06-18-2012, 15:15

Sorry for the lousy quality pics.

Book hanging straight down...
IMG_2440 (Large).JPG equals 7 lbs IMG_2441 (Large).JPG

Book suspended as a hammock with lots of sag...
IMG_2442 (Large).JPG equals 3lbs 10 oz each end IMG_2443 (Large).JPG

Book suspended as a hammock flattened out...
IMG_2444 (Large).JPG equals 10lbs 3oz each end IMG_2447 (Large).JPG hummmm...but the book only weights 7lbs.

I'm convinced.............how about you?

**Roe Ring** · 06-18-2012, 15:19

Originally Posted by Boothill

this might help

http://www.hammockforums.net/gallery...l_original.jpg

boot

This is a great chart. Its logical to think that a 200lb weight in a hammock would place 100lb through each end/suspension, but this is far from true. It's fairly well accepted that with your suspension set at 30*, the forces in each side of your suspension will be equal to the load/weight in the hammock. As the suspension angle lowers, the forces in the suspension increase greatly.

That's about as much maths as my head can take, so I just accept it and get on with the relaxing bit ;-)

Atb

Mark

**gmcttr** · 06-18-2012, 15:20

Originally Posted by Ramblinrev

With all due respect to Tinny... his forte is stoves and for that he is excellent. He is way off base when it comes to hammocks. I wouldn't put much stock in his views on rigging. He just doesn't get it.

Agreed. In the video, he only changed the hang angle a few degrees because "he couldn't get in it if it was higher". I guess it didn't occur to him to lower the straps to where he could hang it as tight as desired.

**Roe Ring** · 06-18-2012, 15:22

Originally Posted by gmcttr

Sorry for the lousy quality pics.

Book hanging straight down...
IMG_2440 (Large).JPG equals 7 lbs IMG_2441 (Large).JPG

Book suspended as a hammock with lots of sag...
IMG_2442 (Large).JPG equals 3lbs 10 oz each end IMG_2443 (Large).JPG

Book suspended as a hammock flattened out...
IMG_2444 (Large).JPG equals 10lbs 3oz each end IMG_2447 (Large).JPG

I'm convinced.............how about you?

I'm in! Great demo.

**Ramblinrev** · 06-18-2012, 15:33

Originally Posted by gmcttr

Agreed. In the video, he only changed the hang angle a few degrees because "he couldn't get in it if it was higher". I guess it didn't occur to him to lower the straps to where he could hang it as tight as desired.

I suspect some of this depends on the suspension system used. I have never used whoopies so I can't comment on that. However with the Hennessy lashing system I can not hang the hammock terribly tightly. But with my webbing/ring buckle I can just about make the webbing twang if I want to. The question of "attainable angles" becomes more complicated when you try to compare a variety of suspensions.