Step 5:

Now you have your brand new Duct Tape Hammock.
Just go outside, hang it up and enjoy the breeze...

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SOTILAS says: Nov 2, 2010. 12:40 PM

Look at that rod bending!

sitzikbs (author) in reply to SOTILASNov 2, 2010. 11:23 PM

what rod bending?

SOTILAS in reply to sitzikbsNov 3, 2010. 1:43 AM

step5: 2nd picture.

sitzikbs (author) in reply to SOTILASNov 3, 2010. 12:24 PM

hmmm... you are correct. i didnt notice it earlier.
but it held my weight fine.
i suppose for future reference you should use a rod with a bigger diameter or different material (like aluminum for example)...

gmyers2112 in reply to sitzikbsNov 4, 2010. 7:35 AM

Aluminum rods (tubes) not good for this. More later if you're interested.

Basic problem:
Because all of your weight is bearing between the tiangulated ends of the rod to the center of the cord, it forces the rods to bend. If instead, each line of duct tape had a corrosponding line extending beyond the rods and were then tied together at a central point, that would eliminate most if not all of your torsional bending. Also, based on past history with duct tape, weight and time, you need to doulble your longitudinal lines (not make them double thick, make more of them). More distribution of weight equals less weight based damage to each line of tape equals longer lasting. ANd it has the added advantage of being more comfortable because of a finer mesh in your hammock.

sitzikbs (author) in reply to gmyers2112Nov 4, 2010. 9:24 AM

i understand what you say and you are correct.
However my solution works too since the bending stress is in reverse relation to the moment of inertia of this rod (the higher it is the smaller the stress). Plus, the yield strength is higher in relation to the material you choose (wood is weaker than aluminum and aluminum is weaker than steel).

gmyers2112 in reply to sitzikbsNov 4, 2010. 11:09 AM

yes, your hammoks works so long as you don't gain any weight or have that nice looking blond chick sit in the hammock with you, but the inherent weakness is obvious in the bend and the bend shows stress that isn't necessary. Simply by balancing that load the bend goes away and the stick will never break.

On the aluminum subject: An equal sized "rod" of aluminum would be prohibitively expensive for a duct tape project and surprisingly heavier than you'd expect; steel even more so. If you used a tube of aluminum, you'd have greater tensile strength in straight compression but the bend your picture shows in section 5 would be disastrous for a tube. A) once bent, the tube would stay mostly deformed and lateral strength would be reduced exponentially. B) at some point the bend would create a kink in the tube and the bent part would shoot through the back of the hammock rider's head with the force of his weight driving it. This tragic and horrific death can be avoided by balancing the load correctly.
:)

G

sitzikbs (author) in reply to gmyers2112Nov 4, 2010. 12:48 PM

some easy stress calculations could tell us exactly the required measurments.
if you would like i can calculate what tube diameter and thickness is required to hold a 100 kg person with a safety factor of 1.5. would you like me to calculate it?

But you are right, for the common DIY guygirl, balancing the load will work fin.

gmyers2112 in reply to sitzikbsNov 4, 2010. 1:11 PM

I think we've probably already spent more time and effort discussing it that it warrants. If you're happy with it and you feel safe, who am I to nay say ye? I drew up a diagram of what I was talking about in terms of extended lines, etc. (though I'm certain that you grokked my intent), If you'd like to have it and or post it for your readers, I could send it to you in a pdf. Else if, cheers.

Gary

binary in reply to gmyers2112Nov 4, 2010. 2:33 PM

wow. i feel like i am watching an episode of big bang theory.

thanks for the intelligent banter! lol.

great and fun project!

i'm penny btw. lol.

sitzikbs (author) in reply to binaryNov 5, 2010. 1:15 AM

LOL, and who am i ? sheldon ?

binary in reply to sitzikbsNov 5, 2010. 12:23 PM

lol. no....i think you are leonard. leonard tends to look at things in another way when presented with a different idea or more efficient idea. he also admits when he might be wrong. sheldon on the other hand...

gmyers2112 in reply to sitzikbsNov 5, 2010. 7:41 AM

If we're choosing, I'm Leonard (most normal, doinkin Penny - formerly) or Stewart (the comic book seller)

sitzikbs (author) in reply to gmyers2112Nov 5, 2010. 5:31 PM

we cant all be leonard... i can settle for being raj, though i talk to girls fine...