The rating of dyneema line limits is usually quoted on best case slow stretch testing.
In tests there is a large difference between fast stretching fail tension and slow stretching fail tension.
Kites can build tension rapidly
1 Like
I guess he may be on to something, but then again I think these tests are slightly unscientific and maybe missing some points.
Speed of changing pulling force seems to matter according to the video.
For a tether seeing varying forces over time, and often close to breaking strength, I would assume the fibers would settle, possibly having somewhat the same effect as pulling slow/fast as shown in the video.
The splice would reduce the strength of the rope by an undetermined amount. I would prefer a large radius capstan to terminate the ends of the rope. The smaller radius loops (radius of the metal shackle) and also the small diameter loops (diameter of the loop at the end of the rope) really invalidate these tests in my opinion. Small diameter gives us a pretty high angle in the «eye shape» of the tensioned loop. This again puts additional forces on some fibers of the rope. Those «shorter» fibers are likely to break first, even though the break happens some distance from the splice and loop.
There are other factors such as wear and aging and exposure to chemicals and light that affect strength. These must be taken into account. Maybe these are separate effects, maybe not entirely.
—
I am thinking about another effect that may have bigger impact for AWE; the surface of the rope becomes rougher with use, effectively increasing [well, probably] the tether drag. This would not affect dimensioning of tether diameter much, but it could limit performance.
1 Like