One of the cool things about archery are the processes around it. On one hand, it’s science. You are dealing with physics, aerodynamics and energy transfers. On the other hand, it’s an art; a human working with machines. Your form, mental state and decision-making all factors into the equation of a perfect shot. Bowhunting and archery terms can get technical. Arrow spine is one of those terms that can seem technical on the surface, but can be easily explained. Here is what arrow spine means and how it affects the flight of your hunting arrow.
The spine rating of an arrow is simply a measurement of its stiffness. The same Easton arrow comes in a variety of stiffness: the lower the number, the stiffer the arrow. For example, a 330 arrow is stiffer than a 500 spine arrow. There are two kinds of spine (stick with us, we promise not to get too technical). There’s static spine, which is how an arrow reacts when an 880-gram (1.94 lbs.) weight is suspended from the center of the arrow. The arrow must be 29” in length and supported by two points, which are 28” apart. The number of inches the arrow deflects or bends X 1000 due to the weight is the spine size or measurement of an arrow. So, a 500 arrow bends .5-inches when the weight is applied.
Then there is dynamic spine, which describes the way an arrow reacts from the stored energy of a bow as it is shot. Too many factors determine the way an arrow is going to react when shot out of the bow, and because of the nearly unlimited variables in determining dynamic spine, Easton hunting arrows are measured using static spine. You can manipulate the dynamic spine of an arrow and make it act stiffer when shot from a compound bow by decreasing peak bow weight, point weight or the point/insert combination, using heavier bow string material or adding more strands to the string, heavier vanes, heavier serving material and/or nocking point and shortening the length of the arrow.
Ok, now that we’ve determined what the spine of a hunting arrow is, why is it important? If you do not have the correct arrow spine for your bow set up, you are going to get erratic arrow flight and poor shooting groups. Having the proper arrow spine is key to optimizing the grouping of your arrows and for the best possible accuracy. Shooting an arrow that is not stiff enough, or a group of arrows that vary in stiffness, will cause you to be less accurate. An under-spined arrow will veer right, while an arrow that is too stiff will favor slightly left.
All this said, how do you choose the proper spine of your hunting arrow? Well we have crunched the numbers for you. On nearly every wall of archery shops around the world is the famous Easton arrow selection chart. It’s the gold standard when it comes to picking the best hunting arrow. Follow the “variables” portion of the chart carefully, and most of all, provide accurate bow weight (measured!) and accurate draw length data. The main reason a hunter chooses the wrong arrow with the chart is because people often guess at these instead of measuring.
The Easton Promise
Easton hunting arrows, produced with our advanced technology and manufacturing processes, deliver uniform spine between all arrow shafts of the same size, and 360 degrees around each shaft. With Easton, you know that your next arrow will fly like the last.
Spine is so important to arrow accuracy, Easton goes far beyond the rest of the industry to ensure you receive both the specified spine and matched weight for every shaft produced in a given model. There are reasons Easton shafts have been used to win every Olympic podium since 1984 and set world records. Spine consistency is one of them.
Other Notes On Arrow Spine
- Usually as an arrow weight increases, so does the stiffness. Thus, a heavier arrow will be stiffer.
- As the largest carbon buyers in the archery industry, Easton works directly with the companies that make the carbon fiber to obtain only select material lots which are as close as possible to the exact stiffness needed for a given design. Using only select materials from the world’s premiere carbon fiber manufacturers, and continually testing the materials as they are prepared for use, minimizes most of the carbon fiber variation.
Now that you know how important a properly spined hunting arrow is to your setup, use the arrow selection chart to be sure you are shooting an arrow with the right stiffness. That will take care of the physical part of the equation. Knowing that Easton produces the most consistent arrows with the highest quality materials will help your mental game and is one more reason to fill your quiver with Easton arrows this hunting season.