Basics : A Guide to Compound Bows

Anthony Cote
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How it Works

A compound bow, also known as a recurve bow or simply compound, is a modern bow that uses a set of cables and pulleys connected to the ends of the bow to help mechanical advantage when drawing a string. Typically, the bow string is drawn back by the archer moving a thumb called a finger tab, which is connected to the string.

A compound bow, is a derivative of the older flat-bow design. This is a sort of bow that is flared outwards, rather than being circular.

Today, there are numerous different designs of recurve bows and compound bows. Some of these cutback bows create a compound twist.

There are several reasons to why compound bows, rather than recurve or longbows are used in competitions. The reasons range from accuracy to force.

Compound bows typically lean towards the more powerful of the bow types. Why this is true is perplexing, as compound bows are thought to be less efficient than longbows.

The compound bow seemingly increases energy by multiplying it, thus reducing the force needed to draw it. What compounds do is add mechanical advantage to a bow. The concept of compound bows came about in the 1960´s. Its creator was a man by the name of Dr. Charles Paris.

The Let-off Principle

The let-off principle that compound bow archers commonly refer to is the reduction of overall tension in the bowstring prior to release. In a nutshell, it is the opposite principle of how draw-weight works.

Draw-weight is basically the weight of the string after it is drawn; the initial draw-weight of a compound bow is the weight it requires to fire when it is not drawn in any way.

With compound bows, the let-off is the amount of draw weight released when the bow is at full draw, this can range from 50% of total draw weight to 70% or more. With the let-off at 50%, the peak draw weight is 200 pounds. With the let-off at 70%, the peak draw weight is only 140 pounds.

The let-off range that is ideal for a given archer has a lot to do with the bow design. Shooters with more experience shooting compound bows will prefer a more aggressive let-off range. As you get more experienced, you will notice that a good let-off can make your shooting more consistent.

The Back Wall

The back wall is the part of the bow where the handle is located and where it's secured against the archer's body. The back wall is intended to give shooters the best possible grip and allow the archer to hold the bow steadier. Some archers choose to customize the back wall to better fit their needs.

The pocket is attached at the front of the back wall and acts as another spot to hold the bow steady.

Riser

The riser is the part of the bow in between the limbs. The riser adds a lot of weight to the bow which gives it its power. The riser is also the part of the bow that shooters look at as an indicator of quality, because the stronger the riser, the longer the bow will last. The riser is designed to move with a shooters body and it is usually made out of aluminium, which is a light weight but strong metal.

Limbs

The limbs create the power of the bow. They are made smaller near the grip and then get larger as they get to the riser.

Limbs, as well as a good riser, are what determine the power of a bow. If a riser is made of strong material but the limbs are too weak, the bow will break and if the riser is made of strong material but the limbs are too strong, the bow will be hard to pull.

Arrow Speed (IBO)

The most basic thing you need to know about is arrow speed. The game you are hunting with the bow will dictate the speed you want. If you are hunting deer, you want to go at a minimum speed of 300fps. Bear is at 330 and elk is at 340.

The speed in feet per second (FPS) is measured by an organization called the International Bowhunting Organization (IBO).

There is a lot more to a hunting bow than how fast it shoots the arrow though. There are many factors that go into making a good hunting bow. First and foremost it needs to be a smooth shooter for you. This means it should be quiet, and vibrate as little as possible. Any vibration is felt in your hand and makes the bow less accurate for you.

Another factor is the draw weight of the bow. This is basically how heavy the pull is when you draw the string back. This affects accuracy and power for a number of reasons. A heavier draw weight means the bow will shoot a bit slower, but it will hit harder. The other factor is that a higher draw weight is safer for you and your child.

If you want to hunt with an archery bow, it must be able to hold a certain draw weight. This is usually at a minimum of 20 pounds. Any kind of a compound bow is already drawn at twenty pounds so this isn’t an issue.

Brace Height

A compound bow is made up of four sections: The Riser, Limbs, Cams, and Grip. The Riser is where the limbs attach, the Limbs are attached to the Riser through the Cams or Limb Cuff. The Grip is the piece you hold onto for aiming.

Riser

The Riser is the part of the bow that houses the Limbs. The Riser ends just before the Grip.

Limbs

The Limbs are the part of the Bow that house the Cams. They are also what the arrow sits atop when nocked.

Cams

The Cams are what actually bend when you pull back. They are held in place by the Limb Cuffs. There are usually two types of Cams, A Vertical Cam and a Fletch Cam. The Vertical Cam is what does the actual bending. It is attached directly to the Limbs and is the part that the arrow sits atop. The Fletch Cam is located directly below the Vertical Cam. It is wide and short, and it holds the Fletch and Fletch Plates (where the Fletch sits).

Grip

The Grip is the part of the bow that you hold onto when shooting.

Axle to Axle Length (A2A, ATA)

The A2A or ATA measurement is the measurement of the bow compound limbs from the center of the string at the grip (back of the bow) to the center of the string at the riser at full draw. Another way to think of this measurement is from the center of the string to the outer most part of each limb.

A shorter ATA length bow will usually provide more speed at a shorter draw length because the limbs are more parallel to the string (as they pull the string back towards the shooter), and because the limbs are shorter it makes the bow a little more forgiving due to the fact that it is less off center. A longer ATA bow will generally provide a longer draw length when compared to a shorter ATA bow. Longer ATA bows offer a slightly longer arrow path and less hand shock, and also a little less speed because the bow is more off center during the arrow cycle.

Draw Weight

Draw weight is the main contributing factor in how difficult a bow is to shoot. It is measured in pounds. The amount of energy it takes to draw the string back to full draw is the draw weight. The higher the draw weight the harder the shot is to pull back, but the shot is going to be more forceful once it is released.

Because of this, the bow you choose will be largely influenced by your body weight. If you have a draw weight of 30 pounds you will have to be fairly strong to shoot a bow effectively. The average male bow user is a draw weight of 40 to 50 while the average female bow user is a draw weight of 25 to 35.

Draw Length

Draw length is how long you pull the string back, from full draw to your face. The more you are able to pull the string back to your face the better control and accuracy you will have. This is how you get your arrows as straight as possible that essentially help your arrows go where you want them to.

Draw length is measured in inches from the belly button to the end of your nose. Draw length can only be adjusted so much because otherwise it can put stress at awkward angles on your back, shoulders, arms, and hands. You could be crippling yourself if you adjust your draw length too much.

Efficiency

Efficiency is the single most important factor when choosing a compound bow. As technology continues to advance, so do the designs of compound bows.

Older designs have been improved and newer technologies are being introduced offering increased efficiency of bows.

At some point you will have to decide how much efficiency you should sacrifice for less weight, or for the sake of having a more traditional bow which is less efficient.

Many things can affect the efficiency of a bow. The amount of materials that make up the bow is a big factor, as is the design of the riser and bowstring. These two are the main components of increasing arrow speed.

The type of limb tips and how the limbs are constructed, affect speed as well. Mass weight and the amount of mass weight in the limbs affects the balance of a bow.

If a bow is too heavy, your energy will not be transferred as efficiently, which will cause a slower arrow speed. The limbs of traditional bows are heavier due to their design.

This means that the limbs themselves are made of a type of material that is heavier, whereas the limbs from a compound bow are made of a lighter weight material. They are constructed of layers of different materials only allowing a small percentage of the limbs tip to make contact with the string. This is also how the tip speed of a compound bow is increased on the string.

Cams

In the compound bow world the term “cams” is used interchangeably with “levers” or “craiges”. It is important for a new archer to know what is meant when someone says the word “cams”. Compound bows include a bow string, cables and a cam separately. Compound bows are also referred to as “levers”. These levers are the things that draw back the bowstring.

So as we can see from the prior definition of what a compound bow is, a compound bow is a few separate components that are put together to make one working product.

The bowstring is the piece that holds all the components of the compound together to make the bow. The cam of a compound bow is made up of two separate components, the cam and the cam cable. When the bow is drawn these two components begin to separate. The cam cable is attached to the end of the cam. The cam cable is what is responsible for holding the bowstring when the bow is drawn. This is what begins the process of releasing the arrow. You can also think of the cam as the trigger of the compound bow.

Two Cam

Traditional compound bows are made of three individual parts: the riser, limbs, and string. Three-cam bows are usually customized to a specific person, whereas two-cam bows are usually designed to be used by a wider range of people.

Two-cam bows are set at a specific draw length and weight and are not adjustable. While three-cam styles are set up with a cams in a neutral position, meaning the bow limbs are fully drawn. This results in three total draw lengths: full, half, and quarter. This also means that three-cam bows can be adjusted to fit a wide range of draw lengths.

The main difference between two-cam Vs three-cam bows is in the attachments. As you can see, the two-cam bow is just one attachment with a string and a riser. Two-cam bows are usually one-piece.

This attachment is usually the heaviest part of a compound bow and may be heavy to carry. This makes two-cam bows more difficult to shoot than three-cam bows.

Three-cam bows have a system of attachments that make the bow easier to carry and shoot. A three-cam bow can be compared to the limb structure and design of a recurve, and it is more similar to the traditional bow.

Single Cam

Single cams are great for beginners, traditionalists, and hunting non-pressured deer. They are very quiet when fired and due to the minimal moving parts they are a little stronger than their dual cam counterparts.

The biggest downside to the single cam is that they only have five or six inches of adjustability, making them difficult to shoot at long distances. The single cam has one string and two wheels that it uses to block the limbs when the bow is drawn.

Dual cams have more than six inches of adjustability. So they're great for newbies or for long range shooting. The dual cam has two strings. Both strings run the opposite direction of each other and come together at the top. One string pulls while the other pushes against the opposite limb.

When choosing a compound bow, the technology used is not as important as the shooter (you). Research the equipment and find the best compound bow for your wants and needs.

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Hybrid Cam

Hybrids are a middle ground and will generally get the best of both worlds, at least depending on what setup you are using. Some are rather mild, while others, for the sake of simplicity, have been known to decrease the draw cycle strength significantly. You'll also find that the cams are different in hybrid bows in terms of the amount of let off they produce, with some only having 70 – 80% let off, as compared to the full 80 – 90% let off with all other types. The cams can vary in terms of timing as well. Full draw cycle timing is particularly aggressive compared to the shorter timing of most other bows.

Another consideration is the axle-to-axle measurement with hybrids. Since they occupy the middle ground of not being a compound bow nor a recurve bow, the difference in length of the limbs is passed off onto the handle, making it longer than a bow with the same limb span. The width of the hybrid is between the average compound bow and the average recurve bow, but closer to the recurve bow than the compound bow. Though they are longer than average, the axle-to-axle measurement is actually shorter than average.

Binary Cams

Compound bows are manufactured with 2 different draw length settings. They can be adjusted between the maximum and minimum positions with 2 draw length adjustment modules. Binary cams are 2 different cams that are mechanically linked together. They move exactly together, so there is no window of opportunity to adjust one or the other "just a little". The primary advantage of binary cams is that the bow's draw length (length of the bow pull from start to stack) is significantly longer than the draw length of a single cambered bow. This longer draw length is called the letoff. Simply put, the letoff is the amount of hold-weight at the end of the draw.

Draw Length

The Archery is one of the most ancient weapons. The archer, as the name suggests, shoots the arrow with the bow. From a long time ago, archery was considered to be a man’s sport and was mandatory in every army.

Bows and arrows were replaced by guns, but is it still being used in the army? The answer is yes. However, as competition and individual sports, it is being carried out in an area where everyone can freely use them.

The bow has been used in many fields of sport. Among all these sports, it is used the most in the field of archery. It should be understood that using a bow for a bigger distance needs the more experience the bow shooter needs to have. A compound bow has a lot of advantages and disadvantages. We will discuss all aspects of it in detail.

Compound bows have been used as a replacement of the ancient bows. It is the most famous invention now used in archery. The main advantages of compound bows are:

  • Feather, reduced set up time
  • Finger levers, reduced stress to handle
  • Cams, moveable pulleys reduce shoot and string movement

These features make bows fast, lightweight and accurate.

The bow has a certain length known as the length of the string:

The Riser

The riser is the area of the bow that is arced and curved to help create more balance. What many people assume is the actual piece that shoots the arrow is actually just the middle piece of the bow. When you shoot an arrow you have one piece that is called the riser, which is typically canted in the center. Then you have the tips of the bow, which are attached and then you have your limbs, which hold the string.

The riser is what most bow hunters are concerned about because it will dictate the accuracy and the type of bow. It is located right below the area where you will put the string. When you shoot the bow, the string animates the limb in a back and forth motion. The string wraps around the riser and acts as the axis of rotation. The accuracy and setting of the bow is largely determined by the riser, especially the accuracy and stability of the bow.

The most common risers are the ones that are canted to create a balance. This means that part of the bow is bent backwards. This reduces the weight distribution so that the string is more aerodynamic and allows a bow hunter to release the arrow from a stable position.

Depending on how the riser is canted determines how the bow is released when it comes to accuracy. The farther the riser is canted forward, the more accurate the bow is.

The Limbs

There are two types of compound bow limbs, single cam and dual cams. Regardless of which type you choose, both mechanisms attach to the riser via a cable system consisting of a cable guard or string stops, a cable swivel, barrel and cable rollers, a cable slide, and a cable hook-up block. The difference between the single and dual cams is that the cable system travels through two cam mechanisms in the dual cam bow, as opposed to the single cam bow where the cable system is connected directly to the cam. To understand how the single and dual cam systems work and what the advantages and disadvantages of each are, it’s important to understand the most important parts of the limbs; the bowstring, the let-off, the draw weight, and of course the cam system.

Compound bows require specialized strings, cables, stabilizers, etc. You don’t want to rotate through an old pair of worn out socks or a frayed rope to restring your bow.

A good quality string will allow for easy maintenance, a longer lifespan, and better accuracy. Choose a lightweight string for smaller bows, and bulkier heavier strings for larger bows. Some strings have specialized features like being noise free (to keep stealth hunters happy), serving as a rest for camouflage, attached to built-in silencers, and being temperature flexible.

Stabilizers and Cables

Both stabilizers and cables must be chosen for strength, weight, and authenticity. Some cables come with special attachments, to make attaching the cable easier.

Stabilizers are not limited to just vibration reduction, they also serve another role “ reducing wind. Wind can be distracting to the bowhunter and make accuracy hard to achieve.

Bow Quivers

Bow quivers come in a wide variety and size. Some bow quivers are made to be detachable, while others are more permanent fixtures to your bow. Quivers are made to not only protect the arrows but also to display the arrows. Bow quivers are also made to be quiet in the woods. Be sure to choose a quiver that is made to suit your bow, and your type of hunting.

Sights

Grip and Wrist Sling

If you don’t already have one on hand, there are some great thumb grips (see the Browning Grip A Sling on page 59 as an example of a thumb sling) that are common on both compound and recurve bows, they don’t cost too much, and they help your left arm rest firmly and feel much more comfortable.

If you can believe it, this is one of those things you should purchase before you even buy the compound bow.

A wrist sling is more than just those loops that hold your bowstring while you have your bow strung. They’re basically little belts that help hold your bow from moving around in your hands, and they also hold your forearm and wrist steady.

Keep in mind that even though these items are on the basics list, they are absolutely worth the money you will spend on them. If you have the money burning a hole in your hand, it is likely that a solid thumb sling will improve your shot considerably, and they can be tight or loose around the wrist.

In Conclusion

A good compound bow can make a good deer hunter out of a less confident archer. But a beginner will want to know a little more about them before they start shopping. Allow me to be your guide on the journey to finding the right bow.

Before you buy your first bow it's important to understand how to judge quality, what to buy, and what to know. This guide will give you an in-depth overview of the best bow reviews and why they are the leaders in the direct cam technology industry.

Now that you've gone through this guide you should find yourself well informed on what the best bows on the market have to offer.

Now get out there and start your journey to be the best archer in the world.