Originally Posted by TeeDee
Also, your rule of cos(31) ~ 6/7, is usable for a single sag angle. You than have only one thing that you can adjust to achieve your desired hammock height - how high you place the tie off points, i.e., the tree huggers. By limiting yourself this way means that where I go, you would have to pass by a LOT of otherwise suitable hang spots and spots that would be better than the ones you could use. I would guess that on the maintained trails in the US this is probably not a problem though.
The sag angle can vary, the 31 degrees is a target used to set the geometry. You can leave the tie off height alone and adjust the suspension length to get the hammock body at an acceptable height above the terrain. If you do that and the sag angle is not within an acceptable range, then you can adjust the tie off height. Of course depending on your suspension system and how it is attached, adjusting the tie off height may be easier to adjust or the suspension length may be easier or they may be about the same.
There are several levels to this issue. There is getting it in the ball park, so to speak, and there is getting it fine tuned, or just right. I'm under the impression that some folks routinely start off tying off the hammock on the low side and have a tough time getting things in the ball park. I suspect that a lot of those folks don't have a good understanding of the geometry, forces and stretch involved (because if they did they wouldn't do it that way), could care less about that, and may never understand that.