Why Do Compound Bows Have Three Strings?

Many modern archers use a compound bow. These bows have not been around for anywhere near as long as the more conventional recurve or longbows but even so, they are hugely popular.

But if you have ever tried a compound bow, you will have noticed that there is more than one string; in theory. What you are actually seeing is the bowstring and a set of cables.

A lot of people who are new to archery find it difficult to understand why there are three strings, or a string and a cable on a compound bow. In short, it is because they operate in a different way to more traditional types of bow.

In this article, we are going to look a little more closely at the workings of the compound bow  and why it is designed the way that it is.

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What Is A Compound Bow?

Traditional types of bow typically have a bowstring attached to the limbs; this simple design goes back thousands of years but in the 1960s, a new type of bow, the compound was invented.

Drawing a bow is known to take quite a lot of strength and holding that draw weight as you aim at your target can be extremely demanding.

A compound bow works on a system of cams and cables which, at full draw, take a significant amount of the draw weight, making it much easier on the archer.

When you look at a compound bow, it is not difficult to see that this piece of equipment is vastly different to the types of bows you are used to seeing in movies like Lord of the Rings or Robin Hood. One of the key differences is the extra strings.

However, it is important to keep in mind that these are not strings in the same sense as your bowstring, but are cables which help to draw the bow.

How Do Compound Bows Work?

Before we get into the details of the mechanics of the compound bow, let’s put it in as simple terms as possible.

Compound bows work on a system of cables and cams that place a force on the limbs as you draw the bow.

But of course, it only takes a quick glance at a compound bow to see that there is a lot more intricacy to the process. For those who have only ever seen a traditional bow, these modern pieces of equipment could look extremely complex, but they are easier to use and are often favored by new archers.

On the limbs of the compound bow, you will see cams, these are wheels that work in conjunction with the cables; which some people may mistake for being additional bowstrings.

When drawn, these cams are able to store energy in the limbs of the bow. You will often be told about the let off of your compound bow and this refers to how much energy is stored when you pull the bow back.

For instance, if you purchase a 50lb bow with a let off of 50%, you would only need to take 25lbs of the draw weight and the rest would be stored in the cam system.

Types Of Cams

Now that we have established that these extra two bowstrings are in fact cables that attach to a cam system in order to draw the bow, it is essential that we understand the various types of cams.

Firstly, there are single cam bows which have a longer bowstring and two cables. You will find a single cam located on the bottom limb of the bow and an idle wheel at the top. Your bowstring is connected in a loop around this wheel and also to the cam at the bottom.

On this design, there is also a buss cable which is used to load the limbs, giving the impression that there are three bowstrings.

Alternatively, you can get a dual cam bow, in this case, there would appear to be three bowstrings, but two of these are cables. Unlike the single cam bow, this design features a cam on both the top and bottom limb, with cables attached to each.

This is a more common design but it is important to have the bow perfectly in sync as the two cames must line up and move in unison.

For this reason, these bows have what is known as a control cable which runs between the two cams and allows them to move at the same speed as one another.

Does This Make Them Faster?

One of the critical things in archery is speed, along with accuracy and consistency, of course. Many people would assume that because of the way a compound bow is made, it would be more effective than a more conventional design.

A lot of it is down to the skill of the archer, but there is a lot of suggestion that a compound bow can fire arrows at much greater speeds than a recurve or longbow. In fact, in some cases, it has been noted that compound bows can fire up to twice as quickly as traditional models, owing to the mechanical advantage.

Conclusion

When you look at a compound bow, it looks like a complex piece of equipment and those who are new to archery might be surprised by the apparent presence of three bowstrings. Surely, that’s not right?

Well no, it wouldn’t be right for a bow to have three strings but compound bows do not have this feature. What you are looking at are actually cables which form part of a cam and cable system that allows these types of bows to take a portion of the draw weight.