Troy Fowler’s life goal is to become a “professional small boy” just like Peter Capstick. Well, in reality, he’s a father to three great kids, miraculously remaining married for 30+ years while employed in a boring corporate fashion. He annoyingly asks “why does that do that” way too often. If you’re a bowhunter - he answers many topics on his YouTube channel - The Ranch Fairy.
When it comes to your bowhunting setup, knowing the “Kinetic Energy” of your arrow allows you to know how much energy that arrow possesses due to motion, from being shot by your bow.The “Momentum” tells youhow much force it will take to stop your arrow when it reaches its intended target.
Kinetic Energy and Momentum Arrow Calculator
Kinetic Energy and Momentum Calculator
Arrow weight Value must be between 250 and 1000 grains.
move slider or enter value
Arrow speed Value must be between 100 and 500 Feet Per Second.
move slider or enter value
If you know your arrow’s weight (in grains) and your arrow’s speed (Feet Per Second), then you can use our Kinetic Energy and Momentum calculator above to find out each! Simply move the sliders or enter the values in the blanks. And, if you really want to take a deep dive into the Kinetic Energy of arrows, check out what the Ranch Fairy is up to below…
Kinetic Energy And Bowhunting (How I Got Here)
As you may already know, the ‘ole Ranch Fairy (that’s me) is quite out of the norm in his measuring of arrow systems. (If you aren’t aware, I am definitely one of the strange ones in the bowhunting world.)
Anyway, just to set the record straight, the biggest overlap between Dr. Ed, the Ashby Bowhunting Foundation, and the Ranch Fairy is simple: We want to know the highest performing projectile for all impact points to pass through the animal you are hunting.
The first time Rocketman said, “well, Troy, a bow is just a spring with fixed Kinetic Energy,” I thought… BLASPHEMY!
But, from what I understand, he is right.
The bow can’t “make” more KE. It is what it is.
BUT, you can change the arrow and gain some…..so hang on. Let me set the table here…
A bow is just a spring with a fixed Kinetic Energy. It can’t make more kinetic energy than what it already possesses.
KE Arrow Testing
On a basic level, radar measures a projectile’s speed over distance.
The testing unit that we used measures 5 total distances. So, if you want to shoot 60 yards, the computer divides that distance into 5 increments.
[NOTE TO SELF – you need to put the target further than 60 yards to capture the flight speed. To address this, we placed the target at 70 yards. Because, if impact is at 60 yards, the data would be flawed for velocity testing because the target stops the arrow at a yardage that it should be being measured.]
The top line is the launch velocity. The change in velocity is super boring… Until you look at the 60 yard impact KE.
The gap in the data sets shows the significant reduction in KE over distance. However, you see that gap narrow as arrow mass increases.
As you can see, in all the above graphs, the launch KE is relatively constant, but alas, further away, at 60 yards, with higher mass projectiles, we see something worth pondering. (Well, only if you think math is correct!)
What are the results telling us? (Please pardon the steam coming out of my ears)
So, despite my heavy arrow bias, (I’m not much of a hair splitter), increasing launch KE 3-6 ft/pounds is really boring.
But the lower line, at 60 yards, is worth chewing on.
If you search around, many of the wide mechanical broadheads suggest KE’s of 45-60 ft-lb’s. Now, they don’t go out on a limb and say, “that will create a pass through, or break bones.” It’s just a recommended impact KE.
Formula for Kinetic Energy: K.E. = 1/2mv2 (where m=mass of object and v=velocity)
And be clear, just like the firearms world, this is launch KE, maximum velocity. This is because a projectile can’t go faster once it leaves the muzzle or the string… It’s always slowing down.
Silly aerodynamic drag.
Now in a vacuum… oh wow, throw in some zero gravity and guess what?
It still doesn’t go faster….. it would maintain launch velocity and you wouldn’t be able to breathe to test it.
Some adult field points and some, ahem, “super weenie points.”
There have been multiple companies and YouTube personalities showing fixed blade vs. mechanical pressure testing on deer thoraxes and other items simulating a critter. They use very complicated mechanical devices down to something as simple as a bathroom scale.
Let’s just say, the HUGE differences are eye popping.
It’s not half a pound or 3, it’s exponential. The “precision” of the device doesn’t matter when the difference is 40 pounds. Please search those tests up, because I know you’ll go do it anyway.
When it comes to arrow penetration, harder things push back harder… you can just blame Sir Isaac Newton for that and keep my hate mail down!
First, let’s make sure we all understand what “quartering away” looks like. Since a large number of bowhunters are after whitetail, that is the example I will use.
Yeah, Yeah, there can be severe quartering, or more toward broadside but quartering. Here’s the simple way to know IF THEY are quartering. Look at the front legs. If you see daylight, it’s quartering.
If a deer is facing away from you and you can see daylight between its front legs… it’s quartering away.
Why the quartering away shot is best
Now that we have that settled, let’s discuss why this shot is the best shot angle. I’ll set this up in order of operation.
They are looking away
Put simply, the act of drawing a bow requires movement. The animal is looking away from you, so that puts you at a significant hunting advantage.
The ears are pointed the other way
So, there’s some debate on a quartering away shot being better because a deer’s hearing would be reduced with its ears pointing away as well. A deer’s ears are cupped, so theoretically, if you make noise, this position would in fact be better.
My example above, of course, has an ear rotated back, just to keep me honest. Anyway, the ears aren’t toward you and that can’t be a bad thing!
The lethal part of the critter, any critter, is exposed in a quartering away stance
In the quartering away stance, there are no shoulder blades or ribcage to hit in most cases, even from a treestand. But, the big “kicker” here is that the arrow is traveling forward. Physiologically, and FACTUALLY, the arrow will be moving toward the more lethal parts of the animal.
So, a little anatomy lesson.. Below is a basic diagram of the broadside of a deer:
Now, you’re going to have to play along with me in this diagram and just imagine the deer is quartering away.
Each “arrow” represents a shot angle (from top to bottom), i.e. a tree stand, low tree stand, or downhill and ground level. That’s why I have the “arrows” as long as they are. They represent a possible wound channel.
But, no matter if the arrow hits the rear of the lungs or the middle of the lungs, the arrow is constantly moving toward the heart, lungs, and major vessels. This is key to WHY!
So, why does this matter Fowler??
Well, I’ll tell you.
Keep things moving forward, folks
The most forward part of the animal, (where all 3 “arrows” intersect and I have placed the “broadhead” in the picture above), include much larger vessels and airways.
Put simply, “it’s legit,” but it’s a bit more complex than that. So, here’s the redneck version…
Your potential to cut “bigger stuff” increases exponentially every inch that the arrow moves forward (let’s hope you’re shooting an adult arrow and hitting the Earth after blowing through).
Anyway, with the quartering away shot, Joe Bowhunter’s success percentage goes up and tracking distance goes down. WIN!
The wound channel is long
It’s pretty simple: The wound channel of a quartering away shot is long.
I laugh when I see these “wound channel” measurements. Mostly to justify a 3” wide mechanical penetrating only 9”.
Mathematically, sure, I get that. But come on man. Can’t we just shoot through a deer?
Let me step off the soapbox now and give 2 examples that will be pretty clear.
So, let’s get down to my level.
I am a simple guy. Below is a basic sponge. It’s an excellent lung example because it’s full of air and holes that represent blood airways and blood vessels, they’re longer than they are wide, and because, well, everybody has handled one.
A perfectly normal lung, with no damage, would feel very similar when compressed.
This sponge and tape measure help to illustrate wound channel length during a broadside shot.
And now, using the same methodology, a quartering away shot.The wound channel on a quartering away shot is longer than that of a broadside shot.
As you can see in the picture above, we get really long wounds with a quartering away shot. Again, the larger vessels and heart are forward, so that’s improving per the “lethal part of the critter” discussed in #3 above.
I’m not saying that broadside shots are bad, so stay on the rails here, this is a quartering away discussion!
But, just look at that wound length. I think it’s pretty clear.
Why the longer wound channel matters
Now, another thing your favorite professional bowhunting guru doesn’t recognize is basic physiology. Now, to be fair, few of them have had a cadaver to help clarify why this works.
The largest percentage of vessels in the deer or other animal are going lengthwise, (i.e. front to back in the lung), and have a little wrapper around them.
Imagine that sponge is inside a balloon but yet stays the same shape. The balloon is perfectly adhered to the outside of the sponge. This means all the air and blood have to enter and exit somehow. That “somehow” is tubes. And all the tubes go in and out of the front of the lungs and then to the legs, neck, head, etc.
That’s a fact. Separate systems for oxygen and blood, with their own committed tubes, running ’round God’s cardiothoracic plumbing system.
As an example, if you didn’t have pipes in your house, water would go everywhere. We have clean water pipes and plumbing pipes doing two separate things. But nope, the water comes in from the city, runs in a big pipe, then enters your house, in smaller pipes, then leaves.
In a lung, the air and blood flow is lengthwise because the entry and exit is in the front.
Just. Like. That.
A quartering away shot is more devastating than a broadside shot because the the blood vessels are running to and from the front, which is where we want that arrow headed!
Where to aim on a quartering away shot | Tic-Tac-Toe!
So, you can use this simple example for any shot angle.
Imagine the board from tic, tac, toe. The front legs are the vertical posts. Imagine a line running on the spine (we prefer not to hit that). Then, another line on the brisket.
Now, shoot the middle of middle box. On any angle, the middle box widens or narrows. Shoot the middle of the middle box.
An imaginary tic-tac-toe board can help provide guidance on where to shoot when taking a quartering away shot.
Trust me, I am not trying to cause a problem with all this heavy arrow stuff.
I was failing.
The Ranch Fairy and promotion of high FOC (Front of Center) arrow systems began because of failure at impact.
High FOC Arrows | How and why they began to matter
Ok, so here’s the abridged version of how and why high FOC arrows became so important to me.
I really like fishing, bowhunting, and shotguns. (Of course, after 30 years of marriage – and still going – Mrs. Fowler is awesome too).
So anyway, I killed a 150” deer in 2009 and just lost interest for “deer” hunting. I became an adult along the way (which surprised me too), had kids, and helped them become quite competent adults and outdoors folks.
Do you want exit wound when encountering humerus breaks, shoulder blades, and spinal columns? High FOC is the answer.
I did NOT, however, lose my love for hunting mature, feral hog boars. They are every bit as challenging as a cagey whitetail, with additional features. Mostly, they suck up arrows like a vacuum and run off laughing.
When you ask the guys at the local shop why they get away so often, they say something like, “big boars are just tough.”
So, I jumped off the bridge with high FOC arrow builds and never looked back. What did I have to lose?
Fast forward 7 years and hindsight being what it is, bowhunting is very simple… bowhunting is 100% equivalent to what happens at impact.
And, how much penetration your arrow achieves will increase your success; not the bow, stabilizer, or whiz bang back tension release, or a miracle peep sight.
The broadhead and arrow kill the animal.
Which one is best? Let’s move on.
Murphy’s Law (Anything that can go wrong will go wrong) certainly applies to bowhunting. But, what if we could have things go RIGHT more often?
What is a high FOC arrow?
So, Fowler “land the plane man!” Get on with it… “what is a high FOC arrow?”
Now, before we continue, you must realize that FOC or “front of center” is the measure of how much total arrow mass is in the front. The industry says 8-12% FOC is normal.
A high FOC arrow starts around 15% and can go up to 30%.
Just as a comparison, we are talking about 100 grain points vs 300-350 grain points.
So, I’d agree wholeheartedly that 8-12% is normal FOC. But that doesn’t answer a simple bowhunting question. “Is that the optimal arrow FOC from bow to animal i.e., “in flight” or is it the optimal arrow FOC to get through the deer, hog or other animal?”
The industry just leaves that as an assumption while moving on to bow tuning and other shenanigans.
How to calculate the FOC of an arrow
To determine the front of center (FOC) of your arrow, first install the inserts, points/broadheads, wraps, vanes, nocks, etc that you will be using on the arrow shaft. Once you have completed your arrow setup use the equation in the graphic below:
Divide the length of the arrow (indicated by “L” in the graphic above) by 2.
Find the balance point. (The balance point is where the arrow balances perfectly on your finger or other object). Mark the balance point and measure the distance from that point to the bottom of the groove of the nock (this distance = “A” in graphic above).
Subtract center of the arrow measurement (calculated in step 1) from the balance point measurement (calculated in step 2).
Multiply the result from step 3 by 100.
Divide the result from Step 4 by the arrow’s overall length (L). This result will be the FOC of your arrow.
If you don’t want to take the time to do the math to find your arrow’s FOC, you can always use an FOC calculator. Just be sure your arrow has the inserts, points/broadheads, wraps, vanes, nocks already installed.
Finally, the jump to these higher FOC arrow systems almost requires you to buy better broadheads, made of great steel.
It’s not uncommon to have tool grade steels. The heads are machined, one-piece, and .08 thick.
They are solid. No fail points – (Rule #1 – Structural Integeriy… CHECK!)
For the bowhunter, this discussion may seem a bit off the rails. I would agree. The FOC town has an idiot, and I am he.
However, my pig killing stats have gone to almost 100%. Literally, if one gets away, I made a non-vital hit, and that’s on me.
But, the adult arrows don’t fail anymore. My arrows don’t break, the broadheads don’t bend or dull on impact, and penetration is almost always into the dirt (unless I hit a big off-side bone, which usually breaks, and turns the pig into a three-wheel drive unit. Pigs have short legs, so from an elevated position, its common to hit the ground before it passes through.)
In closing, I am vitally aware a “normal” arrow system kills millions of critters a year of all sizes.
Mechanical broadheads, the same. I got that. I’ve done it.
But, what if you had an arrow system you knew, for a fact, was going to achieve an exit wound in the absolute highest number of situations – all impact side humerus breaks, shoulder blades broken, and spinal columns snapped with almost 100% efficiency?
What if we accept Mr. Murphy is still alive and well, but we used a tool to level that playing field?
The next time you see your hunting arrow, you should ask, “Is my arrow system capable of almost any impact point OR only if I have perfect shot placement?”
Bowhunting is 100% equivalent to what happens at impact. And, how much penetration your arrow achieves will increase your success.