Arrow spine are the measurement of how much an arrow will flex when it is under pressure. Arrow spine is important to archery because if an archer use an arrow with the wrong arrow spine it will cause the arrow to wobble or fishtail, but if the arrow spine is correct the arrow will be able to travel straight towards the archer target. While many may try to choose arrows based on the look and price of the arrows, choosing arrows based off arrow spine is the most effective means of ensuring that the arrows will accurately hit the target.
To understand arrow spine, it is first necessary to understand the archers paradox, which is a phenomenon of how an arrow bends around the riser of the archers bow. When an archer releases the bowstring, the arrow does not travel in a straight line. Instead, the arrow must bend around the riser of the bow to leave the bow.
What Is Arrow Spine and How to Choose It
If the arrow is too stiff, it will not bend enough and will hit the riser of the archers bow. If the arrow is too weak, it will wobble excessive as it travels towards its target. Placing a weight in the center of the arrow measure the static spine of an arrow.
Arrows with a higher static spine will be weaker arrows, with lower static spine being stiffer arrows. The spine of arrows range from 200 for the strongest or stiffest arrows to 800 for the weakest or most flexible arrows. The archer should match the spine of the arrow to the archers draw weight and the length of the arrow.
Arrows that are longer have less flexibility than shorter arrows of the same material and stiffness. Additionally, arrows with heavy draw weights require stronger arrows with lower spine numbers than arrows with light draw weight. Carbon arrows are available in most arrow shops and are a common choice for many archers, though wooden and aluminum arrows is also available.
The weight of the arrow point will also impact arrow spine. The standard arrow spine is measured with a point weight of 100 grains. If an archer uses a lighter weight point, it will act as if the arrow is stiffer, requiring a higher arrow spine number.
Should an archer use a heavier point, like a hunting arrow with a heavy broadhead, it will act as if it are weaker, indicating a lower spine number for the arrow. The type of fletching for the arrow can also impact the arrow spine that an archer should use. For example, feathers tend to be more forgiving in their flight than plastic arrow vanes, which require more precise matching between the bow and arrow spine.
One way to find the ideal arrow spine for an archer is by using a selection chart for arrows that includes a graph of draw weight for the bow versus arrow length. The intersection of the archer’s draw weight and arrow length will indicate the arrow spine that the archer should use for their arrow. For instance, if an archer has a 36-pound draw weight with a 28-inch arrow length, the arrow spine number indicated on the graph will be around the 400 range for arrows.
The materials used to construct the arrows will impact the flight of the arrow. Carbon arrows are used for their relatively low weights and their ability to travel at fast rates of speed. Aluminum and wooden arrows are heavier but may travel in more straightly lines.
Additionally, there are hybrid arrows that use different materials to increase the precision of the arrow. The archer should always purchase arrows in matched sets such that the arrow spines are within five points of each other. Additionally, the arrows should have a forward-of-center balance (FOC) between 10 and 15 percent.
Such a balance will ensure that the arrow is stable in its flight without overflexing. After the archer has chosen the arrows to use, the archer should tune those arrows so that the arrow spine is correct for the archers bow. One means of tuning the arrows is to perform a paper test in which the archer shoots an arrow at a sheet of paper from a distance of six feet.
If the arrow tears the paper such that the two tears extend to the left or right of each other, the arrow spine is too weak. If the arrow fishtails on the paper, the arrow spine is too stiff. Another means of tuning arrows is to compare how well bare arrows travel to the distance of 10 yards compared to the flight of fletched arrows.
This will allow the archer to adjust the plunger tension and brace height of the bow to ensure that the arrow will travel accurate. Ensuring that the arrow spine is correctly matched to the bow and the arrows are properly tuned will allow for the arrow spine to work correctly with the archers bow. Using arrows with the correct arrow spine will result in the arrows grouping together more close when the archer shoots them.
