Experiment in Arrow Rotation
To ascertain the rate of arrow rotation in flight, the following experiment was performed:
Two arrows having similar feathering were joined by a yard of coarse silk thread, so arranged that the revolution of one took up the slack of the thread paid off by the revolution of the second. They were shot at a sand bank simultaneously from the same bow, one above the other, by which means it could be determined how many revolutions each arrow performed.
From a 50-pound bow with English target arrows three revolutions were made in 10 yards and six revolutions in 20 yards. Some arrows failed to make this number and registered only 3½ revolutions to 20 yards.
For two of Ishi's hunting arrows, the highest average at 20 yards was 4½ revolutions from a 50-pound bow. My own heavily feathered hunting arrows from the same bow at 20 yards averaged 4 revolutions.
It may therefore be stated that an English target arrow shot from a 50-pound bow traveling at a rate of 120 feet per second, revolves at a rate of once every 3½ yards, or approximately 12 times per second. It was very apparent in conducting this test, and in shooting in general, that some individual arrows, due to peculiarities or fault of feathering, do not rotate thus rapidly nor evenly, and some not at all.
In testing many aboriginal arrows, the irregularity of their rotation and flight is a striking exposé of the crudity of their construction. Arrows having feathers all from one wing of the bird and properly placed on the shaft always rotate toward the convex side of the feathers. A single feather from the opposite wing may prevent this rotation.