Rope is one of the most valuable items to have in the wilderness, and this ancient method of creating it produces very good results. Even today some commercially made ropes are wound with the same process. Other natural fibers can be used to create rope (some being much stronger than grass), and this method will work equally as well with any other flexible material. Grass does tend to become brittle when dry which could weaken this rope, but even then it does maintain some strength. In moderate humidity weakness from drying should not become an issue at all.
Note that for best results, each of the two tails of the rope should be twisted an equal number of turns as they're wound. That will ensure that the two coils wind around one another tightly and in a double helix pattern. If one side is twisted less than the other it will tend to stay straight, while the more twisted side coils around it like a spring. When I first started winding the rope in the video you can see I didn't do a very good job twisting both strands evenly for the first few inches, and one side was coiled more than the other. Try to avoid that, as it will be a weak point.
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