Hunting Shafts and FOC
With all the arrow brands on the market today and every model and variation they offer, it is enough to make even the most savvy bow hunters' heads spin when it comes to selecting a shaft that fits their needs. Shafts come in all sorts of different spines, weights and diameters. So the question is, which shaft will work best for you and how should you build it for your style of hunting?
Several of today's bows are pumping out IBO velocities north of 330 fps. Speed has become a major selling point and there is nothing cooler than watching an arrow leave a bow string with blistering speeds. However, over time I have found that when tuning a hunting setup the 280 to 290 fps range is a really good speed. Especially if you are a fixed blade shooter like myself. Once you get close to the 300 fps mark the fixed blades want to start planing and tuning gets a little more tricky. If you insist on hunting with higher speeds with good accuracy mechanicals may be your best bet to maintain both speed and accuracy and also may save you some tuning headaches.
When I look at the listed velocities of today's bows I see them more as stored energy rather than speed. Kinetic energy in ft/lbs is how we measure a bow's energy and can be calculated using this formula:
(Velocity X Velocity / 450400 X Arrow weight in grains = Ft. Ibs)
Our goal is to maintain this energy as long as we can during the arrow's flight. To do this I set my bow to my desired draw weight and start adding weight to my arrow. By adding weight to my arrow I will lose velocity but the kinetic energy will stay the same and actually maintain down range momentum better. When it comes to down range bone crushing penetration, momentum is the driving force and what you want to maintain throughout your arrow's flight.
For hunting whitetails here in southern WV I try to target around seven grains of arrow per pound of draw weight on my arrow. So with my current setup with a Halon 6 at 63 pounds I like my arrow to be around 440 grains. Fortunately that puts my arrow speeds around 280 fps.
When it comes to selecting an arrow, I try to focus on a well built shaft that has the correct spine for my setup. Next I try to find an arrow that is slightly lighter than the others. By choosing a lighter shaft I can add weights where I want to get the desired results I want. When adding weight to an arrow I am extremely conscious of my FOC or Forward of Center. There are several inserts on the market today that allows you to add or take away weights. By doing so you can completely tune your arrow to the bow and still shoot your favorite broadheads.
FOC is an area a lot of bowhunters overlook and it is actually the one thing that will provide them the most when they take to the field. A slightly higher FOC will give your arrow more stability and greatly increase penetration. Be mindful that adding weight to the front of the arrow it will also require a stiffer spine arrow. So if you plan on increasing the FOC you may want to consider stepping up to the next size spine on the arrow selection charts. A higher FOC will also take some of the workload off your fletchings during the arrow flight. This will allow you to shoot a smaller or more low profile vane so your arrows are less likely to be influenced by cross winds and drag. This is especially helpful if you are a long range shooter. The analogy I always use is when you vertically balance a broom stick on your hand, your hand is doing the work of the flecthings. It is constantly working to keep everything in line. When you add weight to the tip the amount of effort that is required from your hand is greatly reduced.
FOC plays another huge role in penetration. Most hunters seem to get hung up on kinetic energy and speed for penetration. Mostly because this is what is advertised within a bow's spec sheet. When it comes to penetration momentum is the driving factor, kinetic energy is the amount of force that is available to drive it. To convey and maintain this energy from the bow to the target requires mass. Without mass you will have blistering arrow speeds but the kinetic energy will be spent on drag throughout the arrow's flight rather than carrying it and dumping it upon impact of the target. When a higher percentage of your arrow's weight is closer to the front of the shaft so is the amount of it's stored energy. This allows a higher amount of energy to be released at the moment of impact. It will actually will bust through flesh and bone while dragging the rest of the shaft in the target. If the weight is further back on the shaft, the mass or stored energy will have to push the arrow into the target. This could cause the arrow to flex on the moment of impact causing it to lose energy and penetrating power outside of the target. This flexing of the shaft upon impact could also allow the arrow to be deflected more easily on a bone sending it off track through the animal.
Without a doubt arrow selection and setup plays a huge role in your success in the field. With a little understanding of each of these elements you can build a tailor made arrow to your bow and your style of hunting that can help increase your odds of success!