The 5 Stages of Arrow Flight
Stage 1: Draw Cycle/Power Stroke
The draw cycle dictates how the cams transfer energy from the bow to the arrow. The rounder the cams, the smoother the draw, the smoother the transfer of power. On the flip side, the less round the cams are, the more dramatic the draw cycle feels, and more aggressive the transfer of power.
When viewing the draw curve graph, the longer and flatter the top of the graph is, the longer the bow remains at full draw weight and the longer the duration of power. Also, the higher the let off, the more drastic the change from holding weight to top weight is. To compare, a traditional bow has no let off. So, on release, the bow is at peak weight when at full draw and drops in a continuous flow from peak weight to 0 weight. This creates a more even transfer of power and the BEST BEHAVING arrow possible, which we’ll get in to in the “reaction” stage of arrow flight.
When a bow is more aggressive, the arrow and broadhead can’t behave together. Since the broadhead is the heaviest component, it’s harder to “move” than the shaft itself. SO, the longer the duration of peak power, the bigger the difference in movement is between the broadhead and the arrow. This causes MANY problems in the behavior of the arrow which we’ll discuss next.
Stage 2: The Arrow's Reaction to the Power
As hinted at prior, the longer the power stroke or duration of peak power, the worse the arrow behaves. Additionally, the higher the FOC, the worse the arrow behaves. But why?
Because peak power is prolonged and the arrow doesn’t have a chance to decompress, the arrow is forced to flex more and more, creating a longer duration of recovery as well as issues with the launch of the arrow. The more the arrow flexes, the more of a chance the arrow has to literally BOUNCE off the arrow rest on release.
Higher FOC only compounds the issues above. The more weight there is in the front of the arrow, the more the arrow has to “work” to move that weight, as per the “laws of physics and inertia.” To simplify, heavier objects require more force to be moved, which means the arrow has to flex MORE before it can move that weight.
Any one of the issues outlined above can cause issues on their own. However, when you have more than one happening at the same time, the problems COMPOUND. Think about it…if a more aggressive cam causes the arrow to flex more, and higher FOC also causes the arrow to flex more, then both together would cause an even larger magnitude of flex.
To compare, we must look at the behavior of an arrow from a traditional bow. Trad bows don’t have any letoff which means you’re holding peak weight at full draw. Upon release, the bow is only at peak weight for a single instant, and then decreases to no weight in a linear fashion. This gives the arrow a chance to decompress and the broadhead an opportunity to “Get moving” as the power decreases.
Stage 3: Arrow Recovery in Flight
An arrow is considered “recovered” when it’s relatively done flexing. It’s important to note that an arrow doesn’t really ever stop flexing completely. An arrow’s “recovery rate” is the time/distance it takes an arrow to recover from the moment it’s released from the arrow.
The faster an arrow can recover, the less energy it loses in flight, the more accurate the arrow will be, and the more consistent each arrow will fly from arrow to arrow.
“By the Numbers”
Let’s assume we are using a bow with a common setup (30” Draw length, 70# draw weight, 80% Letoff.) Here are the average recovery rates for each of the arrow shaft diameter classes
.300 Class - 16 yards
.246 Class - 18 yards
.204 Class - 20 yards
.166 Class - 23 yards
Things that will INCREASE the distances: Increasing draw weight, increasing Let Off, Increasing point weight or weight in the front of the arrow, more aggressive cams
Things that will DECREASE the distances: Stiffer arrow, shorter arrow, shorter draw length, less weight, less FOC, Lower let off, or less aggressive cams.
Stage 4: Arrow Stabilization
An arrow is considered to be “stabilized” when it reaches a tight rotation in flight.This helps an arrow maintain trajectory and direction in flight.
In the case of aluminum and MAXIMIZED carbon arrows, the spine of the arrow is completely linear down the arrow, allowing for PERFECT rotation in flight. This creates a GYROSCOPIC rotation in flight with is the most perfect rotation possible.
In the case of MOST carbon arrows, the spine isn’t linear but rather corkscrews around the arrow shaft from one end to the other. This means the arrow is forced to have what’s called an “elliptical spin.” In simple terms, this means the arrow spins in a pattern similar to that of an atom diagram (add an atom diagram to the right.)
Stage 5: Impact/Penetration
What happens when an arrow impacts a target mostly applies to hunting applications where transmission of energy from arrow to target is required for success. The arrow is the medium that carries the energy with the broadhead being the leading edge or point. At the moment of impact, the way an arrow is manufactured, build, and balanced will DRASTICALLY determine how the arrow behaves.
The higher the FOC, the more weight the arrow has towards the front/ leading edge. Offers extraordinary directional control which means the arrow is extremely forgiving to arrows that are not build well, bows that aren’t tuned properly, and flaws in the shooters form.
High FOC
However, as mentioned earlier, high FOC (15% or higher) also negatively affects the performance of an arrow. The higher the FOC, the more prominent these behaviors are. On impact, these performance flaws rear their head. Firstly, higher FOC causes arrows to take the longest to recover, which means the likelihood of the arrow still flexing at impact is higher. Second, since the arrow isn’t impacting perfectly straight, tons of energy is lost at the moment of impact because the transition of power isn’t linear. Lastly, because all the weight is upfront and the shaft is just along for the ride, the rear end of the arrow is instantaneously forced to flex on impact. This only adds to the energy loss.
Medium FOC
On the other hand, more balanced arrows (10-12% FOC) offer less directional control, but better performance in flight and upon impact. When the weight is more balanced, the arrow works more like a pile driver where the back of the arrow and the front of the arrow work together to transfer energy in a more linear fashion when compared to an arrow with higher FOC. This also allows the arrow to flex less on release and recover faster, making for a more “controlled” impact. It also allows for better penetration at shorter distances because the arrow recovers faster AND does not flex as much on impact.
Highly-Balanced Arrows (Low FOC)
Lastly, highly-balanced arrows (7-10% FOC) offer the least amount of directional control and forgiveness. However, they do generate the fastest recovering build, the most linear impact, the least amount of flex on impact, and the best performing arrow as it relates to the 5 motions discussed in this chapter of the "Science of Arrow Flight." ALl of these factors combined allows the entire arrow to work as one upon impact, transferring the most amount of energy to the target.
Think of it like a 10-car train driving straight into a solid wall:
If all the weight is in the first car or two, the trailing cars will derail and fall off the tracks in all directions. This is exactly what happens to the shaft and energy on an arrow built with high FOC. Similarly, if the train impacts while it’s going around a bend, the rear cars will also derail. This is what happens with an arrow flexes on impact.
Now consider all the weight evenly distributed between the first 5 cars. More of the cars will remain on the tracks, but some energy is still lost at the rear of the train.
Lastly, consider all 10 cars having an equal amount of weight in each. Upon impact, the train not only stays completely in tact, but each car will crash and “pancake”into the car in front of it. This is EXACTLY what happens with energy transfer within the arrow when a highly-balanced arrow impacts the target.
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