From the outside, archery looks like a simple case of physics.
Pick up bow. Pull back on the bow string. Release the bow string. Hope for luck.
But bows have evolved beyond what you used in your high school gym class or the replicas in action films. A bow can now be complex, relying on a more sophisticated system than ‘aim and fire.’
A compound bow is one such bow. And these bows allow archers to actually hit their target more often than not.
How does it work, you ask?
Let us break it down for you. Here’s everything you need to know about shooting a compound bow.
Compound Bows vs Traditional Bows
Bows shoot arrows by tapping into the leverage, which is a mechanical advantage that allows it to store energy in the limbs when drawn.
That leverage is why a bow shoots an arrow far faster than you can throw it.
A traditional bow stores this energy directly in the limbs. When you draw the quiver further back, it gets hard to pull. The energy manifested here allows the arrow to fly further upon release because the energy is transferred.
However, when you pull the string all the way back, you’re using a lot of energy. This is because you’re holding the weight from the bow in your own hands. It’s not only hard to do, but it’s inefficient.
When you’re trying to manage 70lbs of weight, you’re less likely to be accurate. You’re also more likely to feel fatigue much faster.
Compound bows are different. The best way to break down their differences is to go through the most important parts of the bow.
The Basic Parts of a Compound Bow
A compound bow includes a pulley or lever system designed to create a more energy efficient and accurate bow.
There are a few parts that are important to note.
Like all bows, this type of bow has limbs. Most models have limbs made of composite materials. The limbs are important to mention because they store the bow’s energy. The cable system may keep the bow tense, but that tension lives in the limbs.
These models also have something called a riser. This is the central mount for the different parts of the bow. The limbs, quivers, sights, and stabilizers are all mounted here.
A common configuration also includes the cam also known as the wheel. Cams vary in shape depending on the design of the bow. They’re found at the end of the limbs to store energy.
Most manufacturers describe a cam according to its let off. A “let off” is the amount of weight you end up holding when you draw the bow. So, if the draw weight is 70lbs, you’re holding 70lbs in your hand on a traditional bow.
However, if you’re using a bow with a cam that has a let off rating of 70%, then you only have to hold 21lbs of that weight.
The cam provides an opportunity for you to stop struggling with the heavy weight of a traditional bow. You have more time to focus, take careful aim, or wait for the target. Basically, it’s the difference between setting up the perfect shot and struggling.
Finally, there’s the bow string. Every part of the bow is designed to facilitate an efficient transfer of energy that makes it easier to shoot an arrow, including the strings.
The string on the bow you choose will likely be constructed from high-modulus polyethylene. The materials allow for minimal stretchability while retaining strength. Effectively, it facilitates the rest of the bow in transferring energy from the bow to the arrow as smoothly as possible without losing too much energy.
There’s also a second benefit to these strings. Temperature and humidity have less of an effect on these strings, which also allows for greater accuracy.
Let’s Talk Physics: How Arrows Fly Faster
Thus far, you’ve learned that the addition of the pulley or lever system and the cam allow for a more efficient transfer of energy from the bow to the arrow.
You’re not focused on holding the whole weight of the bow in your hands. So, you’re able to set up the perfect shot. However, there are more benefits than an increase in accuracy. They also allow the arrow to fly faster.
An arrow fired from the standard longbow will travel at a speed under 200 feet per second. Meanwhile, a compound bow sends an arrow flying at up to 370 feet per second.
The efficiencies that remove the weight from your hands allow for the arrow to fly faster as well.
You already know that energy = force x distance.
So when you pull the pulley system, you’re pulling one pulley at a time. Because both pulleys on the bow meet at an axle, both move together. Thus, pulling the long pulley forces the smaller pulley to move with the same energy.
However, when the shorter pulley is pulled a shorter distance using the same energy, it creates more force.
Basically, the pulley system multiplies the amount of force you apply to the bow. The bow itself is able to store that energy with less exertion from you. Thus, the arrow can fly farther with less effort.
Buying a Faster Bow
The let off rate of the cam is one way to determine what speed a compound bow will shoot an arrow at.
When a bow has a lower let off rate, it stores energy in the string. Thus, the arrow will fly at a higher speed.
Higher let off percentages shoot arrows at a slower pace. However, higher let off rates mean it’s easier to hold the weight of the bow. So, you’re trading a slower pace for an easier shot.
Conclusion
The qualities of efficiency and speed are the same across the spectrum when you’re buying a compound bow.
Whether you’re buying a man’s bow or a woman’s compound bow, you’ll find that these bows are always easier to shoot, more accurate, and generally more fun to use!
Check out any of our other reviews to learn more about compound bows and find the best one for your needs.
