Friction fire practice. My original intent was to use all naturally found materials from scratch. I started off making everything from Longleaf Yellow Pine (common here in Florida) and Saw Palmetto fibers for the bowstring. I used dried Pine sap as a lubricant for the bearing-block.
Well, it didn't go according to plan. As I was prep'ing the set a thunderstorm was rolling in and it started raining. I did bring the materials home and tried again later, but just couldn't make it happen. So, I resorted to using a proven Laural Oak set with an in-line roller blade wheel as a bearing-block to at least get a coal and blow it to flame.
So, I ended up cheating, but what I was most interested in was how well the natural cordage bowstring held up. Surprisingly, after countless attempts today it never broke and is still usable.