- Ed Speer got me thinking about how strong the supports of a hammock

need to be to support myself. I started thinking vectors and trig.

This is the result. If my analysis is wrong, please point out the

error, otherwise you will begin to understand why the webbing needs

to be stronger than anticipated.

For these purposes, I will assume I weigh 200 pounds.. Actually I

weigh a little less than that, well most days, without any clothing

on...

If I hung my weight from two straps hanging directly above me, each

strap would have 100 pounds of weight to support. However, if I am

hanging from the trees in a hammock, the supports are not vertical.

They pull at an angle. The weight that must be supported (the pull

of gravity) in the downward direction is still 100 pounds for each of

the straps, but that 100 pounds is the vertical vector of the pull

actually pointed from the tree to the support point on the hammock.

One way to calculate the pull is to use trig. The sine of an angle

is the length of the opposite (vertical) side divided by the

hypotanose of a triangle, where the angle is the angle from

horizontal to the cord going up to the tree.

If the angle is 45 degrees, (bannana hammock) then the sine of 45

degrees is .707 If that fraction is inverted one gets 1.41, and the

result is that each cord/webbing is supporting a pull of 141 pounds

in order to support my 200 pounds.

If the angle is 15 degrees (a lot more reasonable for a camping

hammock) then the sine of 15 degrees is .259, its inverse is 3.86,

and the cord must support a pull of 386 pounds.

If the angle is 10 degrees (pretty tight for a hammock) the sine of

10 degrees is .174, the inverse is 5.76 and each webbing strap needs

to pull with 576 pounds to hold up my 200 pounds.

AND THAT IS without any swinging, moving, bouncing, or the like...

So, like Ed says, make sure the webbing will hold up 600 pounds. If

you want a pretty good test and can not get a straight answer about

the strength, string up the hammock tighter than you would normally

tie it up and give it a good sit. If it does not break, it will

likely hold you forever at a more modest support angle.

Oh, by the way, the hammock is also stressed with the same pulls, so

don't go breaking the thing just to test the straps.

Oh, and don't get hurt trying this at home... put something soft

under the hammock, like a bunch of snow.

Rick Message Wow Scott--actual numbers instead of book quotes! Your testing is interesting to say the least--thanks muncho...Ed-----Original Message-----**From:**subypower [mailto:a9144me@...]**Sent:**Tuesday, September 16, 2003 6:49 PM**To:**hammockcamping@yahoogroups.com**Subject:**Hammock Camping Re: Breaking Strength of support webbing/rope/cord`well i guess i get to defend myself now... but i did an experiment to`

prove either way so here it goes:

took my mayan hammock, strung it up with a scale on one end

put 30 lbs ( loaded pack )in the hammock, and change angle of hammock

record numbers

well here it is ( all angles aprox. ):

30 17 lbs

45 22 lbs

15 37 lbs

well I was wrong and bow to everyones master hood

but it is not as bad as the math says it is... never doubled the

original weight on each end but did increase past the weight

so in retrospect a 200 lb person would put about 250 lbs per side at

15 or so degrees and the standard rating i have heard is 4 times

working load should be the min breaking point, so you want 1000 lb

straps ( 4 times is also the DOT rating for pressure vessels )

so i go now bowing out the door

scott`To unsubscribe from this group, send an email to:`

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