Accuracy in archery is dependent on many factors, one of which is shooting the proper arrow. The perfect arrow will have a spine that will allow it to correct its paradoxing (flexing) very quickly in flight which increases accuracy and consistency. Before we jump right to selecting the perfect arrow for your compound bow, let’s look at two important terms, static arrow spine and dynamic arrow spine.
What is arrow spine?
An arrow’s spine is the stiffness of the arrow. An arrow that has a strong spine doesn’t flex very easily while a weakly spined arrow flexes with ease. The spine of your arrow while it’s not being shot is called static spine. This is the spine or flexibility the arrow has when it leaves the manufacturer.
How is an arrow’s static spine measured?
An arrow’s static spine is measured by supporting the arrow at 2 points exactly 28 inches apart. Once supported, a 1.94 lb weight is hung from the center of the arrow. The amount the arrow bends or deflects at the center point is measured in inches. If an arrow sags 1/4 of an inch, it’s spine will be 0.250″ or .250. If a weaker arrow deflects or sags 1/2 of an inch, it’s spine will be 0.500″ or .500.
Some manufacturers relay this spine measurement straight to the product. This is done by including the spine measurement right in the arrow name. For example, a Black Eagle Carnivore 300 has an arrow spine of….? Yeah, .300 spine. Some manufacturers make up their own numbering system. An archery arrow program will have the real spine value in it’s database so whether the manufacturer’s number on the shaft isn’t really too important.
Dynamic spine and how to adjust an arrow’s dynamic spine
Arrow’s also have a dynamic spine. The dynamic spine is the spine of the arrow while it’s being shot. There are a three main factors that influences your arrow’s dynamic spine. Those factors are:
The length of your arrow
The longer your arrow, the weaker the dynamic spine. Think of a pencil. How easily can you flex a brand new long pencil? Yeah, it’s pretty easy. Now try flexing a pencil that’s 3 inches long. Not so easy. With arrows, it’s the same. If you want to adjust your arrow’s spine, you can shorten your arrow. This decreases its ability to flex. You can do the opposite too; you can choose to shoot a longer arrow to get a weaker spine. The key is knowing what spine you need… and that is why archery software is a powerful tool.
Adjusting tip weight
To decrease (weaken) your arrow’s dynamic spine, you can add more tip weight. To increase (stiffen) the arrow’s spine, you can decrease your tip weight.
To understand this, picture holding a car antenna and pushing two different objects. The first object you’re going to push is a bowling ball. Will the antenna flex? You bet it will. The heavy tip weight (bowling ball) made the spine or flexibility of the antenna very weak. Now picture pushing a ping pong ball with the antenna. Will the antenna flex? Not so much. The lighter tip weight (ping pong ball) allowed the antenna to maintain a stiff spine.
The flip side affects arrow spine as well. You can add weight or reduce weight to the nock end of the arrow as well. If you add weight to the nock end of the arrow, you will stiffen the spine. If you reduce weight from the nock end of the arrow, you will weaken the spine.
Increase or decrease your compound bow’s draw weight
Fast bows demand a stiffer arrow shaft. They impart more stress to the arrow during a shot cycle so the arrow has to be stiff enough resist too much paradoxing (flexing in flight).
Slower bows require a weaker shaft. There is less energy transfer to the arrow so the arrow has to be weaker in spine so it does still flex some.
If in either setup, the spine is too weak, it will result in poor consistency and accuracy. The same can be said if the arrow’s spine is too strong. If the arrow isn’t allowed to flex or paradox just the right amount, it will be nearly impossible to achieve optimal accuracy and consistency.
Properly spined arrows are more accurate and penetrate deeper
The bottom line is better performance. Having the right spine in an arrow will optimize accuracy and penetration. The accuracy is achieved because the arrow flexes the proper amount early in flight. This keeps fishtailing or wobbling to a minimum and allows the arrow to straighten out quickly. When an arrow is flying, well.. straight as an arrow, it can transfer maximum energy into its target. This is the equivalent to driving a 16 penny nail into a 4 x 4 with one swing of the hammer.
An arrow that doesn’t have the right spine and is still paradoxing at the point of impact will not penetrate like it should. This is due to the kinetic energy being “twanged” out of the arrow as it burrows in. If you have that one buddy that is always complaining about never getting a pass through shot on a deer or elk, this could be one of the reasons. Another example of how this works is by observing how far an arrow will penetrate into a target at different distances. You may be surprised that your arrow may penetrate more at 40 yards than it does at 20 yards. How can this be? Well, at 40 yards, that arrow has corrected its flight 100% and doesn’t lose any kinetic energy during penetration.
For a nice look at some arrow paradoxing in flight, check out this slow motion video of arrows in flight.
Old and new methods for finding the correctly spined archery arrow
In the 1980s, arrow charts were introduced which gave archers an educated guess at which arrow may suit them. The charts would have various draw weights on the left and arrow lengths on the top and all the archer would have to do is match up both of their settings and purchase the arrow the chart suggested. Although this was helpful at the time, the arrow chart has become outdated.
The design / technology of compound bows has drastically changed in the last decade and this can be seen in the annually increasing speeds of the bows. You can have two bows which are set at the same draw weight and same draw length, but they each require a different arrow. Why is that? The answer is because each bow has a unique power factor which is calculated using a the IBO speed of the bow and the bow’s specs.
So how do you know what archery arrow will react well with any given bow?
The best answer is to embrace technology and either buy an archery program for your computer or go to a pro shop that uses one. These programs are very advanced and eliminate the guesswork regarding arrow selection.
Below are screenshots from the OnTarget’s “Software for Archers”. This software is an impressive cutting edge program which, when mastered, will aid any archer in achieving the perfect setup. Due to all of this programs features it may be a little intimidating at first, but once learned, it will become your favorite and most used tool when setting up equipment.
Selecting the right arrow with archery arrow software
1. Select the equipment you will be using
On the equipment tab, with Database Selections chosen (bottom of the screen), select the equipment that you are going to use. After finding your bow, arrow shaft, fletching choice and nock choice, be sure to click apply in each category’s frame. This will send your information to the next screen that which we will be using, the My Setup page.
2. Enter the specs for your equipment
After selecting your equipment from the Database Selections page, click the My Setup tab at the bottom of the page. On this page you will enter your own personal specs such as draw weight, draw length, arrow shaft length, fletching weight, etc.. If you are unsure of needed information such as fletching weight or nock weight, you can do a quick internet search and find the information. Once you have input all of your information, now would be a good time to use the “Save User Record” feature. This will allow you to use the “Load User Record” at a later date which will populate all the data that you have input. Once you are finished with the My Setup page, click on the Spine Match page.
3. Check the spine reading
On the Spine Match page, you will see the arrow that you selected and personalized in steps 1 and 2. You will also see a couple of frames of information from the My Setup page with information related to your bow specs, weight on string, arrow and fletching values. You can tweek the information in these fields to change the spine of the arrow you are using.
The archery arrow that I selected from steps 1 and 2 appears to be too weak as indicated on the colorful spine graph. The indicator arrow is over the weak end of the graph. On the Spine frame (top center), in the comments box, the program has suggested alterations of my equipment in order to correct the spine of the selected shaft.
4. Dial in on the perfect archery arrow spine
By altering your equipment specs with the suggestions in the spine frame and then clicking recalculate, you will notice a change in the reading on the colorful spine graph. In some cases you can make a couple adjustments and achieve the perfect spine but in this case you will notice that in the results list there is an arrow that is perfect for my setup, the Quest Thumper.
For my setup (bow and archery arrow specs), the Quest Thumper is already a perfect match. It weighs in at 400.7 grains which is right at 5 grains per pound of draw (required for most bows to be under warranty) and shows the spine as being perfect. I also know that this arrow will fly at a speed around 339.5 FPS with 102.4 ft lbs of kinetic energy which is not too shabby!! I can now check the Export Arrow Info box, click the export all data icon just above the equipment tab, and then save this arrow to my User Record.
When using this method, you can eliminate “the wrong arrow” as being a factor in tuning. For more information on the software we used on this page visit http://www.pinwheelsoftware.com/.
So now you know how to select the perfect arrow, but how much should you spend? Is it worth it to spend the extra money for top shelf arrows? Is there a difference? Read below for our take on this issue.
Cheap Arrows vs Expensive Arrows
Often times I am asked what kind of arrows I prefer for whitetail deer, elk, mule deer, 3D, field archery events, indoor events, etc. My answers have returned many different responses. The response that inevitably leads to a lengthy discussion is “Man those are expensive; Why don’t you use cheap arrows?” Let me explain.
As we show on this website, there is a smart way to choose the best arrow for your particular setup; with archery software. Yes you can buy a cheap arrow and simply go off the chart on the box but you will be missing out on the benefits of a better performing arrow.
Differences between cheap arrows and expensive arrows
After inputting all of your specs into an archery program like OnTarget2, you will see the differences between cheap arrows and the higher quality pricy arrows. For instance, you can have two arrows that spine perfectly but have the following differences:
- Quality of materials is different – Cheap arrows will often be made of less consistent materials leading to arrows not flying the same.
- Weight differences – Cheap arrows will always be heavier per spine in comparison with more expensive arrows.
- Performance – This is the most important factor. An arrow that is made of higher quality material (straightness and durability) will perform better in the field. The more expensive and typically lighter arrow will also allow you more room for error when it comes to yardage estimating.
Conclusion on cheap arrows vs expensive arrows
Its worth it to spend the extra couple of dollars and purchase the more expensive, better performing arrows. They fly better, they fly faster, and they last longer. If you’re an archer who is trying to be the best you can be, spare no expenses. Never leave the potentially poor score or missed animal due to the fact that you saved $14.95 on a half dozen arrows.
Other useful facts on today’s archery arrow
Common weights of components
- 3/16″ diameter peep sight weight = 8 grains
- 1/4″ diameter peep sight weight = 10 grains
- D Loop weight = 6-8 grains
- brass string nocks = 5-7 grains
- Blazer vanes = 6 grains
What are grains?
Grains = the unit of measurement when weighing arrows and its components. a good electronic grain scale can be purchased off Ebay for under 10 dollars and is a nice item to have for the serious archer. Most manufacturers require you to shoot an archery arrow with a weight equal to 5 grains or more per pound of draw.
If you are shooting a 70 pound bow, then in order for the bow to be covered under most warranties, you must shoot an arrow (including tip) that weighs at least 350 grains. Too light of an arrow will not absorb enough of the energy of the bow and may result in the bow eventually failing due to the lack of an energy transfer.
Most current bows which are tuned can shoot an arrow as close as possible to the 5 grains per pound of draw rule and still have plenty of kinetic energy to kill a whitetail deer. When hunting bigger game, heavier arrows are preferred by some but speed is then sacrificed.
When choosing the length of the arrow, consider that the arrow should be at least a 1/2 inch forward of the arrow rest.
Summary on choosing the right archery arrow
Archery arrows are not cheap; if you want to buy an arrow with the proper spine and as close as possible to the 5 grains per pound requirement for maximum speed, access an archery program or someone who owns a program. Most quality pro shops will have one. Buy a 1/2 dozen to save on costs and shoot at different bullseyes on targets when practicing to ensure you do not damage your arrows. Robin Hoods (result of an arrow being shot into another arrow) are a nice conversation piece, but they can get expensive. Good luck!