Aug 152018
 

Hammock Research

Hammock with bamboo stand (Hammock Universe)

A few years back, I stayed at my cousin’s house in England. She had a backyard hammock, so I tried it. I was tired (jet lag) and the big hammock was so comfortable that I immediately fell asleep.

Recently, we were given another hammock, about six-feet long with a fold-out frame. I hoped it would transport me to the same ecstasies of comfort. I tried to get into it, but fipped myself onto the grass. After several attempts, I managed to place myself in the middle of the hammock. It was nowhere near as comfortable as the one I’d tried in England. The sides curved, but the lower section was stiff and hard.

This got me curious about hammocks, and I’ve been researching different models, to see if I want to buy one that will Suit My Purposes… whatever those turn out to be.

A hammock seems a simple thing, but buying one and setting it up is more complicated than I realized.

It seems that most hammocks fall into one of two broad categories – those designed for camping, and those designed for use in a backyard. Typically, the camping type are lightweight and designed to be strung between trees, whereas the backyard type are larger and often hung from a heavy stand.

Of course, there’s some overlap here. You could use a camping hammock in the back yard, if you have something to attach it to.

Some camping hammocks

The camping hammock is intended to be carried in a pack, so it has to be strong but light. The better hammocks are made of lightweight ripstop nylon, similar to parachute cloth. Ripstop means that strong threads are woven through the thin fabric. If the fabric is punctured, it will only tear as far as the nearest thread – rather than, say, ripping wide open and letting the unfortunate occupant onto the ground. Of course, you pay extra for the light weight and compact form.

Some campers use the hammock in place of a tent. They climb into the hammock, with a mosquito net enclosing it, and a fly (tentlike sheet) over the top.

There seems to be a consensus that a single hammock is a good choice for backpacking and camping, but that for increased comfort, or backyard use, a double hammock is the way to go.

ENO

Disappointingly, this ENO is unconnected with the avant-garde music producer. It stands for Eagle’s Nest Outfitting, a US outfit. Their double hammock is very popular.

On ENO’s Canadian store, prices are $90 (CAD) for the double hammock, or various fancy print options for $100. Available for less on Amazon. There’s a wide range of colours.

Kammok

I checked various online forums, and people who are snooty about ENO hammocks often prefer Kammok. Kammok appear to be well made and cost a little more than ENO.

Kammok’s standard double hammock is the Roo Double. This comes in seven colours. Selection on Amazon.ca is poor, but Mountain Equipment Co-op carries it for $125 (CAD). They have it in sky blue or orange.

Like many hammocks, the Kammok includes only the hammock itself, with carabiner clips at each end. In the pictures, the clips look like plastic, but they’re actually “aerospace-grade aluminum”.

Hennessy

Another interesting choice is Hennessy hammocks. These are designed as a substitute for a tent, and include a fly (the tent bit) and mosquito mesh and the suspension ropes to hang it up. If you were thinking about buying those add-ons anyway, the Hennessy system is about the same price, and the mesh is permanently fixed to the hammock, rather than having to be strung on afterwards.

The Hennessy comes in two versions. One has a zipper along the side. The other – the “classic” – has a Velcro seam along the bottom through which you climb in. One owner commented that he once set the head of the hammock higher than the foot end. During the night, his body slid forward towards the Velcro gap and the hammock “birthed” him. Let’s all point and laugh. Hahahahaha.

And you’ll need… fasteners…

For most brands, attaching the hammock to anything requires extras. For example, if you want to tie your Kammok to a tree, you’ll need to by a set of their “Python” straps. The Python is a long strap made from two strips of webbing joined together at various points along their length to make what are basically a series of loops. You wrap the strap around a tree, feed it through its own end loop, then fasten the hammock to whichever loop puts the hammock at the correct 30º angle.

Fastening a hammock to a stand usually requires a length of chain. It’s sold as a kit, or you can buy a couple of 2-foot lengths at a hardware store.

And you’ll need… a mosquito net…

For most hammocks, this giant, half-moon of mosquito mesh is an optional extra. It surrounds the hammock, and fastens with zippers and drawstrings, leaving no holes hungry insects can get through. It’s strung up separately, so the mesh stays well above your head. For some brands, this costs as much as the hammock itself. A few camping hammocks have the mosquito net built in.

Backyard hammocks

These hammocks are designed for casual lounging and often come with a frame made of steel or wood. Weight is less of a consideration here.

Some hammocks have spreader bars at one or both ends. This makes the hammock flatter, but also more likely to tip when you get into it. Hammocks without spreader bars take on a banana shape.

My friend Karen swears by this Mayan hammock from Lee Valley. It’s 13 feet long, very durable, and comes in bright colours.

Hammock Universe also sells a similar (possibly identical) hammock. It also comes in a larger family size, which supports over 800 pounds of human biomass.

I found Hammock Universe to be pretty good for backyard hammocks. They have a wide range of styles, ship from Canada, and their hammocks seem to have informative and positive reviews from buyers. (They seem like real reviews, although it’s hard to tell these days.)

Deadly hammock physics

The obvious concern with a hammock is that a rope or fixture might break, sending the hammock and occupant falling to the ground. So, don’t string up a hammock more than 18 inches from the ground, and don’t arrange your spike collection underneath it.

However, the real risk with hammocks is more subtle. When a hammock is mounted on two trees, the pull of gravity on the hammock and its occupant creates a horizontal force on the trees, pulling them inswards. This force is quite low if the hammock is saggy, but if the ropes are made tighter, so they become more horizontal, the inward pull on the ropes and trees quickly becomes very high.

This online calculator shows some figures. (Enter the numbers in the boxes below. The various forces appear in the picture at the top.)

If a 200-pound man (or two 100-pound teenagers, or a sack of 100 two-pound kittens) lies in a hammock at a saggy 45-degree angle, the horizontal force on each rope and each tree is 100 pounds. (There’s also a downward force of 100 pounds on each tree, but that’s less of a concern, for the same reasons that pushing on a tree is more likely to bring it down than climbing it.)

Tighten the ropes a little, so the hammock lies at a 30-degree angle, and the horizontal force increases to just over 173 pounds. This is the angle most people recommend for a hammock. Ropes, hammocks, and healthy, mature trees should be able to deal with this kind of force.

At 20 degrees, the force jumps significantly to 274 pounds.

At 15 degrees (that’s it, get it nice and tight now!) it’s up to 373 pounds. This is getting dangerous.

And if your quest for a flatter hammock leads you to tighten the hammock to a 5-degree angle (that is, 5 degrees from horizontal), when you lie down in it, the force pulling inwards on each rope is 1143 pounds.

At three-degrees, it’s close to a ton.

These are colossal forces, and people don’t have an intuitive grasp of the risks. If you’re lucky, ropes break and you fall. If you’re less lucky, trees or posts break, you fall, and the tree falls in the direction it’s being pulled – right on top of you. There are plenty of reports of hammocks that have toppled trees, posts and brick pillars, all of which come crashing down on their occupants.

People will recommend “good strong rope” – but whatever rope you use, you’re up against the harsh laws of physics. If you want to string a hammock to trees, choose live trees with trunks at least four inches wide, and a rope angle of no more than 30 degrees. If you want to lie more horizontally, whatever you do, don’t be tempted to tighten the ropes, or those horizontal forces will soar. Instead, try lying diagonally. Or buy a bed.

This YouTube video from Inside Edition shows some hammock accidents, and offers some tips, but they miss the point about those potentially huge horizontal forces. The worst accident involved sturdy ropes on a sturdy hammock. It demolished a brick column on the front of a house and paralyzed the occupant.

If you could string the hammock up perfectly horizontally, the force on the supports would be INFINITE. Yes, I said infinite. You could level continents with a hammock.

Remember Alexander the Great slicing the Gordian Knot? That was a hammock knot. Cutting it set Asia adrift. Probably.

Hammock Stands

The easiest way to mount a hammock is between two live, sturdy trees at the correct angle (see above), but trees aren’t always available in a backyard.

Hammock stands provide a relatively safe way of supporting a backyard hammock.

The cheapest options are three-beam stands, comprising a simple arrangement of three straight pieces of coated steel tubing, with a couple of bars fastened sideways to make a base. It looks like a piece of exercise equipment. The angles of the beams distribute the force along the length of the steel tubes, which is a sturdy arrangement. (If you mounted the same beams as posts, a tight hammock would easily bend or snap them.)

I find it slightly offputting to know that, if the hammock were to fall, my back would land right on the steel bar below. But hopefully this doesn’t happen too often. A setup with two bars on each side is also available – although those bars could could also hurt you if you fall off the side of the hammock. Danger lurks everywhere in hammock world!

In a higher price range, you can get wood or aluminum stands, usually forming an arc. It’s an elegant-looking arrangement. Some of these would look very nice indoors, but the biggest ones take up as much space as a small motor boat. So be sure to move the motor boat out of your bedroom before moving the hammock stand in.

The stands vary in length, typically from about 9 feet to 15 feet, measured straight across. Obviously, the stand should be longer than the lying surface of the hammock, and most of them are, but extra length in a stand will allow the cords of a larger hammocks to spread more, and should make it slightly more comfortable. Hammocks with spreader bars always need a longer stand.

Vivere seems to be a common name in hammock stands. Their stands are are available on Amazon and elsewhere. They assemble with nuts and bolts. (The most common complaint on Amazon seemed to be about missing or damaged hardware.)

Hammock Universe sells a 15-foot steel frame that breaks down into fairly short bars that just clip together. It’s as utilitarian (ugly) as every other steel frame, but the assembly method means it disassembles down into smaller parts, making it easy to take apart and move. They also sell a arc-shaped bamboo stand, which, they claim, is more durable than the hardwood stands from other manufacturers.

My Choice

I checked quite a few online sites. In the end, I ordered through Hammock Universe. They got good reviews, and were very quick to answer my questions.

2018-08-15

 Posted by at 8:51 am

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