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06-10-2010, 20:00   #21
matto
Member

Join Date: Apr 2010
Location: Upstate NY
Hammock: WBBB 1.0 dbl/DIY
Tarp: OES std/DD Hattarp
Insulation: Burrow & CrowsNest
Suspension: Webbing/Whoopies
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Quote:
 Originally Posted by Youngblood That is because the load of your body weight is spread out over more of the hammock when you are laying versus sitting. That causes the angle(s) of the hammock fabic to change. This is more difficult to visualize when the ridge line is attached directly to the hammock knots as opposed to a ridge line that is attached a few inches above the hammock knots. We often state that a structural ridge line sets the sag angle but that is not exactly right. It sets the ratio of the ridge line length to the length of the hammock fabric (plus any suspension line) that it is attached in parallel with. How you distribute the weight (sitting versus laying and also laying down the center line versus laying on diagonal) while you are in the hammock causes the angle(s) of the fabric to change and this in turn changes how much force is on the ridge line.
*slaps forehead* Thanks Dave! Excellent explanation. Now I'm having a 'duh' moment.

I still think it's interesting that the force diagrams can't fully explain the ridgeline tension vs. comfort question. My gut tells me it has to do with the fact that the models (at least the ones I've seen so far) idealize the human body as a point load. In reality, we're complicated assemblies of different weight pieces of meat attached by hinges. (Hey, I'm a civil engineer -- not a doctor.) Getting a better handle on the weight and distance ratios of the pieces might explain it and be useful for figuring out the ideal hammock end cut shape too.

Maybe if I get really bored someday I'll build a "simple" pressure distribution from something like this.... http://www.smf.org/articles/hic/USAARL_88-5.pdf. After that I'll just fire up the finite element program and... wait, would this earn me credit towards my Bachelors of Hammockology?

Quote:
 Originally Posted by MikeM I just throw up my suspension at arm length, eyeball it and then wiggle around inside the hammock until I feel just right.
I do that too. And the fact that the equations don't keep me awake is what makes me an engineer and not a scientist.

06-10-2010, 20:56   #22
TiredFeet
Senior Member

Join Date: Sep 2007
Location: MD
Hammock: TeeDee Bridge Hammock
Tarp: Customized JRB
Insulation: Down or IX
Suspension: Whoopie Slings
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Youngblood - really nice to see you back. It's been a while and I missed your insight as in this post. I have seen all the diagrams and gone through the math with TeeDee and my GF and I know they understand what is happening, but you stated it so well that I think I'm understanding it now.

Quote:
 Originally Posted by Youngblood That is because the load of your body weight is spread out over more of the hammock when you are laying versus sitting. That causes the angle(s) of the hammock fabic to change. This is more difficult to visualize when the ridge line is attached directly to the hammock knots as opposed to a ridge line that is attached a few inches above the hammock knots. We often state that a structural ridge line sets the sag angle but that is not exactly right. It sets the ratio of the ridge line length to the length of the hammock fabric (plus any suspension line) that it is attached in parallel with. How you distribute the weight (sitting versus laying and also laying down the center line versus laying on diagonal) while you are in the hammock causes the angle(s) of the fabric to change and this in turn changes how much force is on the ridge line.

06-10-2010, 22:47   #23
Youngblood
Senior Member

Join Date: Dec 2007
Location: Doraville, GA
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Quote:
 Originally Posted by TiredFeet Youngblood - really nice to see you back. It's been a while and I missed your insight as in this post. I have seen all the diagrams and gone through the math with TeeDee and my GF and I know they understand what is happening, but you stated it so well that I think I'm understanding it now.
Thanks TiredFeet.
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Youngblood AT2000

 06-14-2010, 08:53 #24 piponss Member     Join Date: Jun 2010 Location: shirley. ny Hammock: warbonnet blackbird Tarp: superfly Insulation: not sure yet Posts: 61 to many smart people here for me lol lol but im sure i will be in the same boat when i get mine so just to say i read this entire thread and loved it thanks guys for doin all the brain work,,, hopefully i will just hang my wbbb and the rest will take care of itself lol lol lol if not well i will come here for the info thats for sure

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