Arrow spine refer to the measurement of how much an arrow shaft bend when an arrow is shot from a bow. The arrow spine are important in that the flex of the arrow shaft will determine whether the arrow shaft travels straight to the target or whether the arrow shaft fishtails and does not reach the target. If the arrow’s spine dont match the setup of the archers bow, the arrow will fishtail and will not hit the target.
Many archer fail to achieve accuracy with there arrows because they often guess at the correct arrow spine for their bows. There are two primary way to measure arrow spine: static and dynamic spine. A laboratory measures static spine by hanging a weight from the middle of an arrow of a standard length to measure how much the arrow shaft bend.
How to Choose the Right Arrow Spine
The higher the number on the arrow spine, the less flexible the arrow shaft; indicating that stiffer arrows is needed for bows with heavy draw weights. Dynamic spine is a measurement of how much an arrow shaft bend as it is launched from the bow. The archer can affect dynamic spine by the release of the arrow, the length of the arrow shaft, and the weight of the arrow point.
Arrows of different weights or lengths from different archers can require different arrow spines for optimum performance. Draw weight is one of the first factor in selecting the proper arrow shaft for an archer. An archer with a light draw weight will require flexible arrow shafts, whereas an archer with a heavy draw weight will require arrow shafts with more stiffness to accommodate the force of the draw.
Arrow length can affect arrow spine as well; shorter arrows have more stiffness then arrows of a longer length. An archer with a twenty four inch arrow shaft will require different arrow spines than an archer with a twenty nine inch arrow shaft. The type of bow that is used can also indicate the arrow spine that should be used.
Compound bows require stiffer arrow spines than recurve bows, as compound bows use mechanical releases of energy to launch the arrow. Recurve bows of medium flex are typically used, as recurve bows rely upon the archers paradox to allow the arrow shaft to bend around the bow. Longbows require arrows with more flexibility, but arrow shafts made of wood may be more variable in the arrows that they produce.
Crossbows typically require very stiff bolts to be used with them due to the high tension of the prod of the crossbow. Arrow groups will be less accurate at a distance if the incorrect type of arrow spine is use with any given type of bow. Additionally, the materials of the arrow shaft can influence the arrow spine that the archer should use.
Arrows made of carbon are the most common due to there light weight and available flexibility levels. Aluminum arrows are typically use for target shooting indoors due to the consistent performance of the arrows made of this material, but are heavier than carbon arrows. Wood arrows are used for traditional archery, but exhibit more variability in the arrows that are launch.
The weight of the arrow point can affect the spine as well; arrows with heavy points will exhibit more flex in the arrow shaft. Thus, archers using arrows with heavy points will require stiffer arrow shafts to compensate. To ensure that the arrow spine is set correctly for an archers setup, there are some tuning procedures that should of been performed; one such test is the paper test.
The paper test measure the way in which an arrow shaft tears a piece of paper. If the arrow shaft is too rigid, the arrows will tear the paper in a way that indicates the spine is too stiff. If the arrow shaft is too flexible, the arrows will tear the paper in a way that indicates that the spine is too weak.
You can adjust the performance of the arrow by adjusting the nock height of the arrow, the brace height, or the length of the arrow shaft. In order to select the correct arrow spine, there are steps that can be followed. First, determine the draw weight and draw length of the archer.
Second, determine the weight of the arrow point. Third, refer to a spine selection chart that indicates which arrow spine should be used for the archer based off the draw weight, draw length, and type of bow. Finally, purchase arrows of that spine and perform the tuning tests to ensure that the arrow spine is correct for the archer.
Following these steps will ensure that when the archer lines up the arrow with the target, the arrow will travel in a straight line and hit the target; increasing the archer’s accuracy.
