However, in the opposite direction the rod will cut the air better due to the sharp edge created by two planes meeting at an angle, and the resistance will be less; its construction is "unsymmetrical". This will cause the rod to wear unevenly in the two planes and, also, the "stiffening edge" gets the bending right across a glue line.
The FOUR-sided rod has its advocates and some rod makers offer " Quad Rods ", probably by image profilation.The four-sided rod concept is sound , but the broader front areas are less aerodynamic and will meet heavier air resistance than the other two . The rod must batter air / wind at such an extent that the casting can be felt as less distinct.
However, if side-stability is of big importance the four-sided is theoretically the best.Of course the ROUND configuration would be ideal, but for obvious reasons no split bamboo rods come in that shape.