Arrows Series – Part 7: Center Shot and Archer’s Paradox

Now that you have determined the arrows you should use you need to fine-tune your bow to maximize your arrows consistency. Most people think that once you set up a plunger and a nocking point it is all good to go, however that is not the case. The center shot of your arrow is one of the most over looked things when setting up a bow.

The center shot is where the arrow rests on the bow when looking behind it.  When setting up your center shot the arrow needs to be completely behind the string. Most traditional bows do not have a cut-away in the riser and the arrow has to deflect around the handle with something called archer’s paradox.

Archer’s Paradox: The term was coined by Robert P. Elmer in the 1930s. The paradox refers to the phenomenon that in order to strike the center of the target, the arrow must be pointed slightly to the side of the target. Modern use of the term has caused the interpretation of it to be corrupted and the bending of the arrow is often considered incorrectly to be archer’s paradox.

In order to be accurate, an arrow must have the correct stiffness, or “spine”, to flex out of the way of the bow and return back to the correct path as it leaves the bow. Incorrect spine results in unpredictable contact between the arrow and the bow, therefore unpredictable forces on the arrow as it leaves the bow, and therefore reduced accuracy.[1] Additionally, if an archer shoots several arrows with different spine, even if they clear the bow they will be deflected on launch by different amounts and so will strike in different places. Competition archers therefore strive not only for arrows that have a spine within a suitable range for their bow, but also for highly consistent spine within sets of arrows. (Wikipedia)

For an Olympic archer, ideally your set up should be 100% behind the string. Some people actually require the arrow lean a little to the opposite side of your riser so that the arrow can get past the bow without hitting it. You can reduce the effects of “Archers Paradox” by adding spin to the arrow by fletching your vanes or feathers with an offset or helical. It is critical that the arrow must have the correct spine so it can bend around the bow, so the fletchings do not touch anything for consistent arrow flight.

Therefore, once again I stress, for proper safety and best performance, arrows need to match your entire bow setup.

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Arrows Series – Part 4: Spine, Flex and Stiffness

Before we discuss the topic of arrow spine, for proper safety and best performance, arrows need to match your entire bow setup. If you change draw weight, draw length, limbs, riser size, etc. this will affect you arrows. You may need to adjust the arrow length or require different arrows.

Arrow Myth:  An arrow is always straight.

Arrows SHOULD be perfectly straight when not in motion. However, when an arrow is released the force applied from the string causes the arrow shaft to be compressed against the resistant static weight of the arrow point and therefore bends.

Newton’s First Law of Motion: Every object in a state of uniform motion (rest) tends to remain in that state of motion (rest) unless an external force is applied to it.

Since the force applied is greater than the  resistance (weight of the tip), the arrow is propelled forward, and the shaft continues to flex and oscillate as it straightens itself. Arrow shafts that are either too stiff or too flexible will not fly well and will impact the accuracy of your shots or fail causing damage and/or injury. Therefore, we need to manage the flex properly so the arrow does not make any contact with the bow, or your arrow flight will be affected.

Important Tip: Arrow spine refers to the arrow shaft’s degree of stiffness (how much the arrow resists being bent) and is called spine deflection.

Basic Rule 1:  Shorter arrows act stiffer and longer arrows act more flexible.

Basic Rule 2: Powerful bows require stiffer arrows and less powerful bows require shafts that are more flexible.

Basic Rule 3: The heavier the tip equals greater the resistance, therefore the greater amount of compression.  So, a heavier tip causes the arrow to flex more and a lighter tip increase the stiffness.

According to the American Society for Testing and Materials (ASTM) the modern standards (ASTM F2031-05) an arrow’s official spine deflection is measured by hanging a 1.94 lb. weight in the center of a 28″ suspended section of the arrow shaft and is used for aluminum and carbon fiber arrows. (I believe original AMO standard has a basic guide to use for wood arrows spine determination and uses of 2 lb. and 26” section for standard measurement.) The actual distance the 1.94 lb. weight causes the shaft to sag down is the arrow’s actual spine deflection

For example, if a 1.94 lb. weight causes the center of a 28″ arrow to bend down 1/2 inch (.500″) the spine deflection would be .500″.  Stiffer arrows will bend less and more flexible arrows with bend more.

Almost every arrow manufacturer has its own numbering system and there are no universally agreed spine sizes among the various arrow manufacturers. Simply, the lower the deflection measurement equates to a stiffer arrow and higher the deflection measurement the more flexible the arrow. Manufacturers can number, size, and market their arrows anyway they want, as long as they provide the deflection data and test using the industry standard method.

Fortunately for us the engineers have already done the math for us and manufacturers provide spine selection charts. You are able to select an arrow based on your draw length and draw weight.

So when selecting arrows a good rule of thumb is that lighter draw weight, shorter draw length and/or lighter tip weight equals LESS arrow spine OR heavier draw weight, longer draw length and/or heavier tip weight equals MORE arrow spine.

Arrows – The Series (This time, it’s personal)

Since arrows are extremely important for an archer, I thought I would do a couple of blogs about arrows starting with the various components. I will be focusing on arrows for recurve target archers, since there are a lot of articles about arrows for both compound and traditional archery already. Selecting the correct arrows for your best performance is not simple task. There are tons of things to know and understand and it may require some trial and error. In this first blog we will start with the basic components.

An arrow is comprised of four major components the shaft, the point, the nock and the fletching.

Shaft : The shaft is primary structural component of the arrow and all other components are attached to it. Originally arrows shafts were made from wood however new shafts are made from aluminum, carbon fibre or both.  It is very important to properly match the arrow stiffness (or spine) to the archer for the best groups. Spine, or stiffness of the arrow, references how much or little the shaft bends when compressed through the shot and it typically matched by using the archer’s draw length and the bow poundage.

Fletching : Glued towards the back of the arrow, fletching are the airfoils for the arrows designed to stabilize the arrow in flight. Traditionally made from real feathers, target arrow fletching are now typically either plastic feathers or plastic vanes. Most target arrows have three fletches that are attached with a slight twist to help the arrow spin and stabilize faster in the air.  The quicker and more stabile the arrows is, the more consistent your groups will be.

Point : The point, or arrowhead, is the functional part of the arrow that is inserted and glued to the front end. It provides the weight and is typically made of various types of metal include tungsten.  Target points are usually bullet-shaped and designed to penetrate target butts easily without large amounts of damage.

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Nock : Found at the rear end of the arrow, target nocks are typically made of plastic. They are inserted, capped over or combined with separate medal pins inserts and held in place by friction. Target nocks are designed to gently pinch the bowstring to hold it in place when the bow string is drawn.

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Over the next few blogs we will dive deeper about these components, various discussion concepts like center shot, arrow indexing and numbering your arrows in upcoming posts and help understanding things like spine and Archer’s Paradox.

Remember, this blog is not meant cover everything about arrows. I am still learning and visit my coach regularly to help me develop my understanding about everything archery. I encourage you to share your knowledge and experiences so we can all develop together.

Remember Cartel Doosung offer a wide variety of arrow lines including aluminum and carbon fiber including their new line of Arista arrows for young archers. If you are in the market for some new arrows check my earlier blog about selecting and purchasing arrows.