This discussion has been moved from another discussion at the request of another poster. Both variable and fixed length ridgelines were used by Mayan Indians which are credited for having invented the hammock about 1,000 years ago.
Below is a reenactment of the typical hammock setup used by travelling Mayans
I agree the line in the photo does not do what TH's ridgeline does, but it does have the potential to set the sag.
Is the pic below a structural ridgeline? It definitely limits the sag of this Thai hammock. Granted, it does it in a different way than the HH, but it does by design make it so the hammock will set up the same every time.
While HH certainly has one type of structural ridgeline, I really don't think the idea of a structural ridgeline should be limited to HH's method. There are many ways that have been used for centuries to set the sag and those are virtually all some sort of structural ridgeline - be they wood, bamboo, webbing, cord or some other material.
-------------- after someone questioned the above being a structural ridgeline
Are you saying that simply setting the maximum length that the ends of the hammock body can attain is not what sets the sag or not a structural ridgeline (even if it is a permanent part of the hammock as in both pics above)? As you note, in the second pic, the hammock is not acting as a structural ridgeline, but that it easily could is apparent.
-------------- after someone opined that unless the ridgeline was shockcord or very weak, it was a structural ridgeline:
I'm fairly sure shock cord wasn't around 1,000 years ago . The ropes used to make the travel version of the Mayan hammock were woven as single rope to a point just before where the hammock body attached. The rope was then split and the ridgeline formed from one portion of the rope and the rope portions were rejoined at a point just beyond where the over end of the hammock body was attached. It is inconceivable that the Mayans would have made the upper portion of rope so weak as to only be sufficent to hold up bugnet -- they were using heavy animal hides or large leaves cut from local flora for rain protection.
---------------- after someone suggested I get a lawyer and challenge the HH patent:
Some of the manufactures may want to research Mayan hammocks and challenge the patent(s), but I have no dog in that race.
I'm not trying to find a way to challenge TH's patents, but to understand what does and does not constitute a structural ridgeline and how it could be implemented. I'm not a manufacturer so it would serve no purpose for me to challenge TH's patents. My sole motivation for entering this discussion was developing a thorough understanding the concept of a structural ridgeline and considering all ways to implement it in my designs - designs which are DIY projects with features not needed by most hammockers. I design for myself, Mother Nature and a handful of others with disabilities or back problems.
In the first pic, the ridgeline limits the length the hammock body can attain because it is shorter than the hammock body. What makes that piece of rope that connects the just above the hammock body ends different from a rope that connects in the whipping itself? If I used the piece of rope holding up the bugnet to determine how far my hammock body would be stretched, would it miraculously become a structural ridgeline?
Are structural ridgelines load bearing (do they actually take on some of the weight when the hammock is occupied?) or do they simply serve to limit the maximum distance the hammock body can spread (and incur strain from holding the supporting cord or webbing in the proper place)?