Thursday, September 8, 2011

How To Lie in a Hammock

It's not junk food. It's not driving slightly over the posted limit. It's not carrying a few extra pounds around the middle. It's not chlorine or fluorine in the drinking water. It isn't those overhead high-voltage power lines (an awe-inspiring monument to what separates Man from the animals: his ability to make electricity). Neither is it drinking from plastic bottles, cooking salty food in a teflon pan, or licking cholesterol-based pork-flavored frosting directly off of aluminium pots. It's not even duct-taping a dozen active cell phones to your head and calling all of them at once. None of these things can actually kill you.

Stress is the real killer. Do something about stress, and these other risk factors take care of themselves. Ignore stress, and you're caught in a non-stop game of whack-a-mole with a never-ending stream of environmental health hazards, many of which you can do nothing about.  But what can your average Joe do about stress?  Plenty.

When men are relaxed, composed, well-rested and get the required amount of sleep, they perform better on the job, have stronger marriages, have better relationships with their kids, fewer car accidents, fewer health problems, more hair, and a longer schwanz.

(Well, probably.  We haven't actually tried to get data on that last one.)

Men, it is virtually YOUR DUTY as a husband or father to go lie in a hammock. RIGHT NOW!

Here's how to make hammock-time a safe and enjoyable means to a longer, happier life, rather than the painful, embarrassing Funniest-Home-Videos experience it has the potential to become.

1. Find two stout trees in a quiet location that are 12 feet apart and each at least 8 inches in diameter. I strongly advise against hammocks slung on a metal frame, between posts of a patio, or on hooks screwed to a wall or ceiling. No hook, eye bolt or screw from a hardware store will do the job, and 2x4s or even 4x4s are not suitable. You need trees.

If the trees are too close together, your bum will drag on the ground. If they are too far apart, your bum will drag on the ground. Weird, isn't it?  It's paradoxes like that which motivated me to study physics and mathematics in the first place.  The really important questions in life.

2. Get two pieces of strong rope, half inch diameter give or take, about 5 feet long, but long enough to wrap around your trees three times with a foot or two left over. Tape and melt the ends to prevent fraying (if natural fiber, tape or lash the ends and apply glue).  I like to wrap the rope in tape at the cut before I cut it, to forestall any unraveling.

3. One end of the rope attaches to the loop on the end of your Hammock as shown. Pass the end through the loop, behind and around the hammock cord, and then under itself. Do not make a more complicated knot than this, because a) it will not hold any better, b) it will be more stressful on you and on the rope.  The secret to hanging in there for the long haul (physically and metaphorically) is to manage stress and keep things simple.
Second pass: goes under first pass.

4. The other end of each rope is wrapped around a tree at about head-height like this. The second pass goes under the first, on the side of the tree facing directly away from the other tree. The third pass makes a loop which is put under the second pass as shown. Why a loop? When it starts raining you can pull this end of the rope and have your hammock stowed away in seconds flat. Again, don't try to make the knot more complicated. If done correctly, the rope will break long before this knot ever lets go. The bark of the tree provides friction against the rope, so don't attempt this on metal poles, smooth timber posts, or on anything other than a natural tree, or with anything other than twisted multi-strand rope.
Third pass: loop held by second pass.

5. See that the hammock hangs approximately as shown (below). If it hangs too slack, it will be uncomfortable. If it doesn't hang enough, you could break the ropes and end up with a bruise on your backside and your ego.

A Catenary.
6. Lie diagonally across the hammock, not lengthwise. Hammocks are more stable this way, and you will not flip over and fall flat on your face to the utter glee and amusement of anyone who happens to be videoing you on their cell phone.

An empty hammock forms a geometric shape called a Catenary. It is the solution to an elliptical integral equation which has no simple algebraic form. It is one of Nature's most beautiful shapes, in my opinion. Interestingly (well, to me anyway) it is also the shape assumed by a thin, flexible elastic object, such as the blade of a saw, when the ends are pushed towards one another.

When a typical 200 pound man sits in the middle of a hammock, how much tension is on each rope? Would you say one hundred pounds, which would be the total weight shared evenly by the two ropes?  No! This is why many hammocks fail.  The rope tension is actually much higher than that. If the trees are 12 feet apart and the total hammock length is 15 feet, then the rope tension is 167 pounds. If you shorten the hammock by 1 foot, the tension increases to 194 pounds. Taking another foot off makes it 260 pounds. I'll leave the details of the vector geometry for the reader to do as an exercise.

As the hammock is shortened so that it doesn't hang down at all, the force theoretically approaches infinity. But long before that happens, the trees lean inwards to reduce the tension, or the rope stretches slightly, or something breaks.  Again, do not use metal hooks, screws, bolts, hangers, eyes, or anything from a hardware store other than good, honest rope and two solid trees in a quiet location.  If these steps are followed to the letter, I personally guarantee you total relaxation, longer life, better health and significantly fewer incidents of public humiliation. Or your money back.

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