Arrow Fletching And F.O.C. Balance
Fletching Choice: Recommendations
We strongly suggest you choose fletching that will yield more accuracy rather than more speed, especially if you're a bowhunter. Before you choose your fletching type, it's important to consider how difficult your arrows will be to stabilize in flight. If you only use your bow for recreational target shooting with field points or target nibbs only, a 2-3" fletch will probably be sufficient. Field points are easy to stabilize. But broadheads are another story. If you shoot broadheads (particularly large fixed-blade broadheads) which often tend to fly erratically, a larger fletch will be essential to achieving good arrow flight and consistent groups. If you shoot mechanical broadheads, you can get by with a little less. There probably isn't a true right and wrong here, as fletching material is essentially a personal choice. But here is general chart to help you select a reasonable fletching option for your setup.
Click here for larger image.
Front of Center Balance
If you've ever played a friendly game of darts, you've surely noticed that the dart is designed so that it's heavy in the front, and light in the back. If the dart were weighted the opposite way, with the tail being heavier than the tip, it would literally spin around and hit the target tail-first. Obviously the ballistics of a dart and an arrow are a bit different, but the underlying concept is similar. A projectile's flight is most stable when most of the projectile's mass is positioned Front (or Forward) of Center [FOC]. As such, an arrow should be heavier in the front than in the back. But how much? Where's the "perfect" balance point?
This is another hotly debated issue among archery enthusiasts. In fact, some of the self-proclaimed chat board gurus seem intent on beating the FOC issue to death. So before we get into this, we need a quick reality checkpoint. If your FOC is really really out of whack, it's an issue. But don't spend too much time splitting hairs about whether your FOC should be 9% or 10%. If your FOC is reasonable (7-15%), your arrows will function as they should. And don't assume that the mathematical average (11%) of the recommended 7-15% range is somehow the best score. It doesn't work that way. The ballistic physics for FOC include some rather elastic variables that make finding an "mathematically optimal" FOC very difficult to declare and prove. To make matters worse, we even see a variation in how FOC itself is calculated (some include the tip of the arrow in the length measurement, some stick with the AMO arrow length measurement). So don't pull out your scientific calculator on the FOC issue. It's not necessary. Just choose a reasonable value and move on.
Fortunately, most common arrow components tend to yield finished arrows well within the recommended 7-15% FOC range. The only real danger of slipping off the FOC precipice is if you use really heavy fletching and super-lightweight target nibbs, or if you choose small light fletching and a jumbo tip weight (or a heavy brass insert). For common arrows with basic vanes or feathers, aluminum inserts, and 85-125 grain tips, chances are your FOC will come out just fine.
With all that said, it is generally believed that an arrow with a high FOC will fly well, but with premature loss of trajectory (nose-diving). While an arrow with a very low FOC will hold its trajectory better, but it will fly erratically. So again, another trade-off for you to consider.
If you balanced a standard raw arrow shaft (no components), the balance point would be the middle of the shaft (0% FOC). But since tips and inserts at the front of the arrow are usually heavier than the fletching and nock at the tail, most finished arrows balance somewhere just forward of the middle. So computing FOC is pretty basic. In the example on the left, the 30" long arrow has balance point that is 3" forward of the arrow's actual center (15"). So its FOC is 3/30 or 10% of the total arrow length forward of the arrow's physical center. Example 2: If a 28" arrow balanced 2" forward of its physical center, you would compute the FOC as 2/28, or 7.1%. Easy!
So when you order your custom arrows, keep FOC in mind. If you choose heavy 5" vanes and an anorexic 50 grain tip, you'll likely have an FOC that is too low. On the other hand, if you choose 3" lightweight feathers and a jumbo 175 grain tip, you'll likely have too much FOC. So try to avoid opposite extremes at the ends of the arrow, and choose an arrow setup that will give you an FOC balance of roughly 7-15%.
To help make this whole process a little easier, this page includes an easy-to-use simulator. Just select the values and components, and you can compute your estimated finished arrow mass and FOC like a pro. We suggest you take a little time to experiment with the calculator, and learn how each variable affects FOC balance.
Before moving on, you should be clear on the following:
1. What are the different type of fletching materials?
2. What are the pro's and con's for vanes and feathers?
3. What is the difference in a straight, offset, or helical fletch? Which is better?
4. What size fletchings will provide the best stabilization for my particular setup?
5. What is Front of Center Balance (FOC)?
6. What is the recommended amount of FOC for proper arrow flight?
Jon Henry is an avid outdoorsman who enjoys both hunting and fishing. He has been shooting and competing in archery for almost 40 years, and began competitive archery in the NFAA at age 12 as a youth. He was a sponsored PAA pro archer for several years, and before that competed for 15 years in both the NFAA and NAA. Jon retired from competition about 8 years ago, due to a series of shoulder injuries that impacted my ability to sustain competitive performance.
Jon is in his mid 50's, and still very much enjoys shooting his bow and now crossbows as well. He is taking a great deal of his experience gained from building and tuning archery equipment and applying it to crossbow shooting, since they are very similar in many respects.
Jon's goal is to help as many new shooters gain a solid knowledge of their equipment as possible, so that we can continue to grow the sport of target shooting and hunting with a crossbow, until it becomes as popular as the other traditional forms of archery.
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