What is an Arrow Chart?
What is Arrow Spine?
The primary purpose of an arrow chart is to help you find an arrow shaft with the correct spine, or stiffness. The longer your arrow and higher your draw weight, the stiffer an arrow you will need. The reason for this is because when you trip your release the forward momentum of your string applies such great force to the arrow that it flexes both as it is leaving the bow and during flight. Too much flex (weak arrow) or too little flex (stiff arrow) will adversely affect your arrow’s flight and accuracy.
Before we get in depth about what exactly arrow spine is, let’s distinguish the difference between static spine and dynamic spine. Static spine is how stiff an arrow is and how resistant it is to bending. You can easily determine the static spine of an arrow by placing it two points apart at a known distance and apply pressure with a weight at the center of the distance. How far it drops, or it’s displacement from the center point is the spine. For example, if you were using a 29 inch arrow and placed it on two posts carefully measured 28” apart and applied a 2 pound weight to the middle of the shaft and measure how far the shaft drops that would give you the shaft’s spine. If the arrow deflects 0.300 inches, it is said to have a “300” spine. Likewise if it deflects 0.400 inches, it is weaker and said to have a “400” spine.
Dynamic spine is how the arrow shaft actually bends when fired. This is influenced by several factors including stiffness, arrow fletching, nock weight, string force or point weight among others. Dynamic spine is nearly impossible to calculate because of the amount of force and flex being exerted down the shaft after being shot.
Once an arrow is released from a bow, it flexes drastically. An arrow that flexes too much or too little is a problem; however, an arrow that flexes too much is a more troubling concern. A weak arrow magnifies the smallest error made by the arrow after being shot and can be nearly impossible to tune properly – especially with broadheads. An arrow that is too stiff, or doesn’t flex enough, doesn’t present as big of a problem with accuracy and tuning. When it comes to arrow shafts, using one that is too stiff is far better than one that is not stiff enough.
An easy way to determine whether or not your arrow is too stiff or too weak is to do a little paper tuning. If your arrow hugs the left then your arrow is a bit too stiff. Conversely, if your arrow hugs the right then your arrow is too weak. Unfortunately, this trend goes unnoticed by most archers simply because they have no knowledge on arrow spine. They simply blame it on poor shooting or poor form. For more information about paper tuning make sure to visit PaperTuning.com.
Shaft material also plays a role in spine consistencies and inconsistencies alike. Generally speaking, aluminum arrows offer the best spine consistency, however their spine will break down very quickly, in as little as 10 shots in fact! The spine life of carbon arrows on the other hand is much, much longer. It takes hundreds of shots with a carbon arrow to begin to wear down spine consistency. Friction is the primary cause for the breakdown of a carbon shaft. The friction needed to stop an arrow when shooting it into a target will gradually wear down the outer layer of carbon on the shaft and thus decrease the spine consistency. Aluminum shafts break down for different reasons. The constant flexing of an aluminum shaft upon release of the arrow and target impact quickly takes its toll on aluminum, a notoriously brittle metal.
Arrow Spine and Effect on Broadheads
Since we are assuming that your use of an arrow chart will aid you in determining your hunting arrow, it’s important to know how arrow spine and broadheads work together. As was mentioned earlier always shoot an arrow that is too stiff in regards to arrow spine as opposed to one that is too weak. A stiffer arrow tipped with your hunting broadhead is more forgiving and will tune much better than an arrow with a weak spine. This is particularly useful information when shooting fixed blade broadheads. As many of you know fixed blade broadheads can be difficult to tune because they are subject to wind planing. However, with your new found knowledge of arrow spine you may find that it isn’t your broadhead, but possibly your arrow. Keep this in my mind when sighting in your hunting arrows this fall. Remember, a stiffer arrow will favor the left when shooting while a weak arrow favors the right.
Arrow charts are an extremely useful tool made available to archers. They are able to provide exact information in regards to which arrow you should be shooting based on your specific criteria and measurements as well as what you will be shooting for (competition, 3D, big game hunting, etc.). This information will allow you to better tune your bow and arrows and increase your shooting confidence as well as your hunting success this fall. Just remember that arrow charts are only a guide to selecting the right arrow shaft. Some bows may tend to favor a weaker arrow, while others may favor a stiffer spine. Feel free to experiment with various arrow weights, spines, and point weights until you find the combination that works best for you. All major arrow manufacturers will have their most recent arrow charts posted online for your use. Below is a collection of links to current arrow charts as of the publishing of this article.
All major arrow manufacturers will have their most recent arrow charts posted online for your use. Below is a collection of links to current arrow charts as of the publishing of this article.
Easton Archery, Carbon Express, Gold Tip, Victory Archery, Beman, Carbon Tech