1. ## Advanced Hammock Theory - Illustrated

Sub Title: The relationship between hammock size, diagonal sleep angle, hanger height, and hammock sag angle discussed.

Sub-sub title: Math majors needed!

Background

I can accommodate up to three hammocks inside my home, and over the past few months I have enjoyed resting, lounging, and sleeping in a climate controlled environment. While not a lab, per se, I have found that I experiment more with my hammocks, testing sag angles and various hammock accessories. In the field I'm less finicky, just 3 paces, reach, and hang.

One thing I've been pondering in my testing is whether there is a relationship between the size of my hammock, the pitch angle, and how diagonal I can lay in my hammock.

The Theory

Late last year (2010), thexuprising posted an interesting question about the Nano, a small hammock measuring 9 × 4 ft (2.7 × 1.2 m). Among the responses was one from Mister Dark on how he found the best diagonal for this small hammock by pitching it tighter than the recommended 30 degree angle.

In my own testing, I found the same thing to be true. Like many of you, I have several hammocks, some "normal" size (5x10 ft), and some small like the Nano. One thing I found in my testing is that at some hang angles, depending on the hammock size, I would get "sagging" fabric on the sides (The Wall). When I changed the sag angle, not only would the sagging fabric change, but where the "natural" diagonal lay angle would also change.

Some forum members have referred to this "natural" diagonal lay angle as "dialing it in" or "find the sweet spot."

For example, I found with jumbo-sized hammocks, a deep sag was preferable and enabled an almost perpendicular lay. Trying a wide sleeping diagonal on a small hammock and my feet and head fall off the sides. This is obvious on one hand simply because there is less fabric wherein to lay.

I think the idea of this "sweet spot" (the right diagonal lay) has everything to do with the relationship between hammock size, sag angle, and height of the person.

For example, my kids get the absolutely flattest lay in my large hammocks and have a very obtuse diagonal lay. I've often said to myself, "wow, what would it be like to have a hammock that large for me (in proportion to my size)?

I found this curious and the more I tried different configurations, I came up with these postulates:

1. The larger the hammock, the deeper the sag.
2. The smaller the hammock, the shallower the sag.
3. The deeper the sag, the more obtuse diagonal lay angle (more toward perpendicular to the hammock).
4. The shallower the sag, the more acute the diagonal lay angle (more toward parallel to the hammock).

I realize that a typical and valid rebuttal to this theory is for everyone to just find the sag angle that works for them, after all, hang your own hang. In practice, this is absolutely true. Personal preference will trump scientific notions. I, for one, do not bring scientific instruments in the field to get the right hang angle for my hammock, I just hang. However, while I might not use instruments in the field, this theory (if true) may influence how I hang in the field depending on what hammock I take with me.

Future Study

I'm not sure if there is anyone out there who has access to complex scientific 3D modeling software, but I would love to see if my theory can be mathematically validated.

To help visualize my thoughts, I drew up an outline showing the relationship between occupant size, hammock size, hang angle, and diagonal sleep angle.

Now it is time for the peer review! What are your thoughts?

~derek

2. This is interesting. While I am a mathematician, I don't have access to this type of 3D software. Maybe i can ask around, or one of the engineers will have access.

I will have to try experimenting with tension/angle vs diagonal direction and see if I can replicate your results. thanks for posting this.

3. The first thought I had is a Sailmakers spinnaker design software?

The modulus of the fabric in the 3 planes must be readily available from manufacturers, especially for spinn, cuben and parachute nylons.

4. ## Ridgeline

Love your illustrations; but, now have a headache thinking about the math. Long ago, my math was pretty good; but, that was before everyone started wearing shoes and I now need to take off my shoes to count change

Just this weekend, I was testing a friend's BlackBird and going thru what you are postulating here. May I suggest that you MUST also consider the structured ridgeline (if so equipped). I found my sweet spot with a shallower angle; but, the ridgeline was way too taut... I am just under 6 feet (shrinking with age). Found that my guesstimated 30 degree hang caused the BB to "bunch up" under my legs from the knees down which was uncomfortable; i.e., leg(s) were over that "bunched-up" fabric and cutting off circulation. Felt that almost immediately.

Shallower angle (and TAUT ridgeline) solved that discomfort.

Just my two cents. (Didn't even have to take off my shoes! Actually I did since it's a friend's hammock)

J.D.

5. A great start would be a "sticky" cataloging hammock shapes and characteristics in table of data. Not so different from what several mfg do in helping (?) customers choose among models.

6. I like to set up all of my hammocks with a structural ridge line. This way I can always pitch it "tight" to ensure the same sag. I do find your data accurate. I pitch my Deep Jungle XL with more sag than my Blackbird. The experimental analysis is sound!

7. One idea I didn't articulate well is the idea/theory that each hammock has its own "sweet spot" based on the occupant and other factors. Like a tarp with cat-cut edges, if not pitched correctly, it will sag and fabric will be loose. When pitched correctly, all sides are taut.

My theory suggests that when the proper hang angle and diagonal sleep angle are matched with the hammock size and occupant size, the fabric will be appropriate taut on the sides.

That's not to say you can't sleep comfortably any other way, just that there is an optimal spot based on those several criteria: occupant height, hammock size, sag, and diagonal lay. Theoretically.

Thanks everyone for your thoughts and recommendations. I realize this is probably more theoretical than practical, hence the "Advanced Hammock Theory" -- maybe this is the 300-level coursework?

8. I know I've seen HUGE Brazilian hammocks where people were completely perpendicular in them. Like this

I think the width plays a big part though.

9. I slept in my grand trunk ultralight once pitched tight because I set it up for my kid and switched with her in the middle of the night. This is the only time I've fallen from a hammock. It wasn't so much a fall as a slingshot throw from the hammock. I just offer that as an anecdotal story of how pitching tight with less fabric is somewhat less stable..

10. The hammock I made for my son is 10.5' and he is roughly 40" tall. The hammock is 60" wide. I put him to bed and set him at an angle, maybe 40 deg. When I check on him during the night and morning, he is almost always perpendicular to the hammock ridge line.

Since it's been only a week since he's been sleeping in it, does he eventually get to this point because it's more comfy or because his weight shifts him to that position?

I have always thought about making a hammock wider than I am tall and see how it feels. But most fabrics are only 60-65" wide. I'm 74" tall. Hense my dilemma. I have thought about sewing two together, but I just haven't yet. Would the seem detract from the comfort? I know I can't be the only one to think of this?