July 05, 2018
In my previous column, we discussed why you should be shooting small-diameter arrow shafts. I listed the many reasons skinny arrows are better than fat arrows: they penetrate better, they drift less in the wind, they require less fletching and they maintain downrange velocity better.
I also want to convince you to add weight to the front of your arrows, regardless of diameter. Almost all the things that are improved by using a skinny shaft can be further improved by using a heavier point and/or insert.
Weighing the Benefits
Within reason, the more weight you add to the front end of an arrow, the better that arrow will perform. Think of grabbing one end of a loose piece of string and throwing it like you would a baseball. The string is not going to line out and fly in a straight line. However, if you tie a lead sinker to the end of that string and throw it again, the string is going to follow the weight in a straight line. This may not be a perfect analogy, but it helps illustrate the concept. An arrow in flight follows the same principle as the string. The more weight you put on the front end of the arrow, the better the rest of the arrow is going to follow the point. The steering effect of the fletching is also improved by a heavier point.
Another benefit of a heavy point/insert is the more weight you put on the front of the arrow, the less the wind will affect the flight of that arrow. With a lot of weight up front, the wind may cause the fletching end of the arrow to oscillate back and forth in flight. However, the point will not oscillate nearly as much and will move in a relatively straight line (horizontally speaking) to the target.
Using a heavy point will also make the arrow more forgiving. An arrow with a higher FOC will move the fulcrum point farther forward on the arrow, giving the fletching more leverage. This improved leverage allows you to use smaller vanes to maintain the same steering power. Using smaller vanes is a good thing, because many of the good aspects of hunting arrow performance are inversely proportional to the total surface area of the arrow. In other words, the less surface area, the better the arrow will function.
More weight in the front of the arrow also helps improve penetration. The added weight keeps more of the kinetic energy pushing the arrow in a straight line upon impact, especially when impacting a non-uniform target (think deer). Imagine two arrows that weigh the same. The first arrow has most of its weight in the front end of the shaft (heavy point weight), and the second arrow has most of its weight in the back end (heavy fletching/nock). When the front-loaded arrow hits the non-uniform target, the shaft itself will bend very little. However, when the back-loaded arrow hits the non-uniform target, the shaft will bend a great deal. This is because the mass and momentum of the back end of the arrow keep it moving forward, bending the shaft. Much of the arrow's kinetic energy will be used to bend the shaft rather than contributing to penetration. (Think of a pole vaulter. As the front end of his pole hits the ground, his weight, attached to the back end of the pole, causes the pole to bend.)
It's important to use a relatively stiff shaft when using a lot of weight in the front end of the arrow. The dynamic spine (stiffness) of the arrow decreases as weight is added to the front of the arrow. The dynamic spine is a measure of how stiff the arrow acts as it is being accelerated by the bowstring. The more weight on the front end of the arrow, the weaker the shaft will act. The static spine is a measure of the shaft's stiffness at rest. The static spine will remain the same no matter how much weight is added to the front of the arrow.
As mentioned above, when the arrow decelerates (hits the target), the opposite holds true. The more weight on the front of the arrow, the stiffer the shaft will act. Again, this is important because the more the shaft bends, the less it will penetrate, because the arrow's energy will be used to bend the shaft rather than pushing the broadhead deeper.
There are many ways to add weight to the front end of an arrow. Back in the day, I used lead birdshot mixed with 24-hour epoxy. I placed it right behind the glue-in points of my target arrows or the inserts of my hunting arrows. One problem with this method was the distribution of weight wasn't always perfectly concentric, which lead to accuracy issues. It was also difficult to make every arrow weigh the same. Another problem was the epoxy would eventually break down, and the pellets would rattle around inside the shaft.
I've also used multiple inserts to increase the front-end weight of my arrows, but that gets expensive. Many arrow manufacturers now offer brass or stainless steel inserts for their arrow shafts. These inserts weigh much more than aluminum versions and have the advantage because they are concentric and of a consistent weight. Some even have break-off tabs on the back end so you can customize the amount of weight you are adding, while others have threaded back ends that allow for the addition of even more weight in standard increments as desired.
One of the easiest ways to increase the weight on the front of your arrow is to use a heavier point or broadhead. I've used 125-grain broadheads exclusively for quite some time now. In many cases, going to a heavier head means going from an aluminum ferrule to a steel ferrule or from weaker/thinner blades to thicker/stronger blades. This added strength and durability is yet another benefit of shooting arrows with added front-end weight.