If you are setting out to make bow drill cordage, you are probably better off using the same amount of fibers to make thicker string, but this could be helpful if you already had cordage; whether natural or man-made that might not be durable enough to stand up to the rigors of ember creation on its own. I’ve shown a method for reverse-wrapping cordage into 4-ply to make it tougher, but I love when I can make things simpler instead of more complicated; and this is one such instance. There is nothing revolutionary here; I’m still doubling it over and twisting it, but instead of taking the trouble to reverse-wrap it, I just tied it into a loop and twisted it before wrapping it around my hand. This seems to keep it together at least as well as making proper 4-ply cordage and the extra twists involved will make the cordage more flexible as long as you don’t over-do it. This is some old nettles cordage that I made for fishing line; and it has stood up to four embers with this method so far. This set was a particularly troublesome piece of western red cedar driftwood that had more moisture in it than I expected. I had to use more speed and pressure than normal but the cordage still held up great. Another big factor here is the multiple wraps around the spindle. This keeps the cordage from slipping, which abrades it and will lead to it breaking eventually. Tilting the bow so that the cordage doesn’t run over itself is just as necessary. The natural cordage part of a natural cordage bow drill is the easy part. Making it work with your set is much trickier, so I hope this is helpful. Natural Cordage Playlist https://www.youtube.com/watch?v=CPfmLCFtoDI