Usually the arrows are made of wood, carbon, aluminum and fiberglass as well as combinations of carbon and aluminum. Each of these materials has advantages and disadvantages. The important matter is that the arrow need to be light and unbreakable as much as possible. An important property is the elasticity of the arrow, which is indicated by the spine value. There are two slightly different methods of measurement. In simple terms, the arrow is placed on two bases (26 and 28 inches apart), and then weights of 2 pounds (lbs) and 1.94 pounds (lbs) are placed in the middle. The deflection in 1/1000 inch is then the so-called spine value. A high spine value results from a strong deflection and high elasticity of the arrow.
When the arrow is fired, the tendon strikes straight ahead, while the arrow must twist around the middle of the bow. Depending on the construction of the arch, a slightly softer or harder arrow is needed. In this case, the pulling force of the arc or the acceleration of the arrow plays a decisive role. After shooting, the arrow bends several times in the air until it takes a quiet trajectory.
A too hard arrow flies too far to the left and one too soft too far to the right. In addition, a too soft arrow could break if the deflection is too strong.
The arrow must therefore be adjusted to the bow and must not be too soft or too short to prevent injury to the hand holding the bow.