Rigging a No-sag Hennessy Hammock Tarp

My first camping hammock was the Hennessy Expedition Asym. It was the hammock that converted me to staying off the ground when I went camping. However, I was often frustrated that I couldn’t keep the stock tarp taut, particularly when I got in the hammock. I could make everything look amazing and beautiful on the outside, but once I got inside, the hammock settled and the tarp went slack. Limp. Frumpy.

hanging-hennessy-no-sag-merged1

My solution at the time was to remove the tarp from the hammock and pitch it separate from the hammock, but there are still a few advantage to having the tarp connected to the hammock suspension:

  • Easier set up and take-down (especially when using a sleeve or SnakeSkin style stuff sack)
  • No conflict between hammock and tarp suspension
  • The tarp is always centered over the hammock
  • No abrasion with tarp line on the tree bark
  • Lighter (ounces to grams)

Connecting a tarp to the hammock suspension isn’t restricted to the Hennessy Hammock models. You can tack on a tarp to any hammock so long as the suspension extends long enough to provide a connection point. For example, you can connect a tarp to whoopie slings using a prusik knot on the non-moving side of the adjustable loop.

hanging-hennessy-no-sag-merged2

The ‘trick’ to rigging a no-sag Hennessy Hammock tarp—to keep the tarp taut even when the hammock is loaded—is all in how you hang the hammock. Traditionally, the Hennessy is shown being pitched very tight across the anchor points. However, the tighter you pitch the hammock, the higher the horizontal “pulling” forces, which in turn, stretch the suspension components more. That stretch lengthens the suspension (a lot or a little), which changes the hypotenuse and the point where the tarp used to be, thus making it slacken.

Also, if the trees on which you are hanging are small, those tighter pitches can also pull the trees in slightly, further adding slack to the tarp.

Instead of pulling the suspension tight and “as level as possible”, hang the suspension at a 30° angle. This minimizes the horizontal pulling forces and minimizes the change between the original hang angle and the final angle once loaded.

hanging-hennessy-no-sag-merged3

The tarp connection point can also placed further up the hammock suspension, which keeps the tarp taut when the hammock is loaded.

I often add elastic shock cord to tension the side tie-outs of my tarp. This can help take additional slack out of a tarp (especially if it has been raining, which can stretch nylon material). This is an optional step, but it can help in some cases.

But, don’t take my word for it—give it a try and tell me what you think.

Perfect-Pitch-Hennessy-Hammock-Tarp

 

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71 responses to “Rigging a No-sag Hennessy Hammock Tarp”

  1. RGB Avatar
    RGB

    The basic premise behind this proposed method is wrong.

    The hammock ridgeline is not a rigid pole. It is a flexible rope. In recent designs it is probably sheathed UHMPE (Spectra or Dyneema),which is fairly stiff by rope standards, but nonetheless a flexible rope. The hammock floor is attached at the ends of the ridgeline. This results in the floor/ridgeline system sharing the load of your body in the hammock. If you doubt this (and you don’t mind destroying your hammock) pitch your hammock low, put a strong mattress below it, get into the hammock (which should be just above the mattress when loaded) and cut the ridgeline or the hammock floor: either way you will drop onto the mattress!

    Therefore, with a load in the hammock, the floor/ridgeline system will not be straight. It will follow a catenary curve along with the remainder of the suspension system. The slacker (more V) in the suspending lines, the greater the curve in the floor/ridgeline system.

    A well-designed asymmetric hammock (like a Hennessy) has the insect-net and floor cut so that when you lie at the intended angle, your body is supported in a curve less than that along the axis of the ridgeline. But if you use more than the designed V in the suspending lines you will get more curve in the floor/ridgeline, more sag in the insect netting and more sag in your body, no matter how you lie in the hammock.

    More V in the suspending lines means less tension on the suspension system when the hammock is loaded. Good, but the system is designed for the tension that will result from the method specified by the manufacturer. There will inevitably be some curve under load because of stretch and tightening of the suspension components under tension. If you start with more V (say 30º instead of 5º before weighting the hammock) it may lower a bit less when loaded, but it will still lower because there will be a substantial increase in tension which will lengthen the suspension system. You can tie the tarp further out along the hammock support lines (and you must do so if you want the tarp to start out tight), but when the hammock lowers under your weight, the tarp will still sag. It may sag a bit less, and you may not notice it for a while if you have pre-tensioned a stretchy (eg silnylon) fabric, but it will still sag.

    If you do not want net in your face and excessive curve in your body, follow the hammock suspension method (and angles) specified by the hammock manufacturer. If you do not want a slack tarp, do not connect the tarp to the hammock lines. Suspend the tarp from separate lines to the hammock support trees. You do not need heavy tarp lines or extra webbing, as the tension in the tarp lines is not high enough to damage the trees. It works best to tie the tarp slightly below the hammock support lines. Then when the hammock lowers under your body weight, there will be a slight gap between the hammock ridgeline and the tarp above. You can save weight (if desired) by removing all of the unnecessary prusiks, plastic rings, hooks and ‘snake-skins’ from the hammock. If desired, you can save even more weight, and get a pitch that stays tight, with a (more expensive) cat-cut spectra tarp.

    1. Derek Hansen Avatar

      Thanks RGB. I think you missed the math. The hang angle of the hammock is set, and the ridgeline prevents it from being pulled too tight, BUT you’re right — you DON’T want to sag it too loose or it loses all kinds of benefits, most importantly is the comfortable lay. The point I’m trying to make is in line with your logic — the suspension and fabric stretch, and it’s worse if you try to hang it TOO TIGHT. The compromise is to hang the suspension at an angle slightly more acute than the hammock angle so that the tarp doesn’t sag when you get in. The illustrations in my book help. And I’m sorry for the LATE reply. My WordPress instance had cached all comments and I’m now just getting to them. I’m sure by now you’ve long since made a decision!

  2. Derek Hansen Avatar

    Yes. Please check their website.