Arrow Fletching And F.O.C. Balance
By Jon Henry
Glued near the rear of most arrows are 3 (sometimes 4) feathers or plastic vanes, arranged in an equal pattern around the circumference of the shaft. These parabolic-shaped pieces of material (sometimes collectively called the "fletching") serve to help steer the arrow during flight. If the tail of the arrow is precisely following the tip during flight, the fletching slices cleanly through the air without changing the arrow's path. But if the arrow's tail isn't perfectly following the tip, friction occurs between the air and the fast moving fletch - pushing the fletch (and the tail of the arrow) back into proper alignment with the arrow's tip. So the fletching helps to stabilize and correct the arrow's flight. Easy enough!
Of course, all fletching materials aren't created equal. Arrow fletching is available in a number of different shapes, colors, types, thicknesses, lengths, etc. And they can be applied in different configurations: straight, offset, or helical (spiral). So how do we know which ones to pick? Should we go with feathers? Or vanes? Would a bigger fletch do a better job than small ones? Is one more durable than another? What are the trade-offs? Well, let's start with the easy ones.
STANDARD VANES (Duravanes/Rubber Based): Vanes are made of soft flexible plastic and are the popular choice for today's archer. They're inexpensive, easy to apply, quiet in flight, available in almost any size/color, and they can be easily fletched in a number of different patterns (straight - offset - helical). Since vanes are impervious to water, they make an excellent all-weather choice for hunting. In addition, they're also relatively durable. Vanes can be crumpled and abused (up to a point of course) and they still pop back into shape ... or they can be heat-treated with a hair dryer and made to pop back into shape. Either way, vanes aren't nearly as delicate as feathers.
However, compared to feathers of the same size, vanes are heavier - as much as 3X the weight of a comparable length feather. And since most vanes have a smooth surface, they don't "dig-into" the air as well as the rougher surface of feathers. So all other things being equal, vanes don't stabilize arrow flight quite as well as feathers. But don't make too big of a deal out of the vane's limitations. For the vast majority of applications, they're more than sufficient for the task.
SPECIALTY VANES (Blazer Vanes): The standard Duravane style vane is an enduring staple item of the industry, and it's the most widely used type of vane, BUT ... someone is always trying to invent a better mousetrap. So specialty vanes make a splash in the archery market periodically (Quikspin Vanes, Blazer Vanes, Spin Wings, Bi-Delta Vanes, FOB's, etc.). Of course, the "improved" vane designs tend to come and go over time ... but the one specialty vane that seems to be hanging tough is the increasingly popular Blazer Vane, by The Bohning Company.
The Blazer Vane is a small stiff 2" vane which is more plastic-like (urethane based) than rubber. Its claim to fame is three-fold. First, it's a little tougher than rubber-based vanes, so it stands up to Whisker Biscuit abuse without distorting or wrinkling. Secondly, the surface of the Blazer Vane isn't smooth, it's textured slightly to "bite" into the air better than smooth vanes. And finally, the manufacturer claims that the unique shape of the vane - specifically the straight leading edge - provides some kind of aerodynamic benefit.
Now, with all that said, we shouldn't get too carried away here. A 2" vane (regardless of the advertising wizardry and technical hoo-hah) is still a 2" vane - with the surface area of a 2" vane. So realistically, a claim that 2" Blazers can outperform standard 4" Duravanes might be a technical stretch. Nonetheless, Blazer Vanes are small, light, look cool, and seem to work well enough. Over the past few seasons, we've begun to see our customers opting for Blazer Vanes more and more often. Roughly 32% of our 2009 arrow orders went Blazer.
The only obvious downsides to Blazer Vanes are increased cost (roughly +$5 p/dozen arrows over standard Duravanes) and the fact that they can be very fussy to fletch. In spite of Bohning's claim that "Blazer Vanes are chemically treated to promote proper adhesion ...," the day to day reality is somewhat different. After building literally thousands of arrow sets with Blazer Vanes, we can confidently say that fletching Blazer Vanes is a pain in the neck. If you don't have just the right glue, the right temperature, the right humidity, the right phase of the moon, and the right music playing in the background, they don't stick. If you're a home fletcher, keep this in mind before you decide to go Blazer.
FEATHERS: Of course, feathers are the original arrow fletching material. When it comes to design, you just can't deny that mother nature knows best. First, feathers are very light. Three 4" Gateway feathers weigh just over 8 grains - compared to 24 grains for three 4" Duravanes. This means your arrows fly faster with less loss of trajectory downrange. Feathers also have a natural texture that effectively bites into the wind. So feathers do a particularly good job at stabilizing large broadheads and finger-released arrows. And archery feathers have a natural curvature to them (left-wing or right-wing, depending on which side of bird they're from), so they help arrows to spin in flight - which also aides in arrow stabilization. As a matter of achieving the best possible flight, it's just hard to beat a feather.
But feathers are not for everyone or every application. Firstly, feathers are rather expensive. Basic 4" feathers can cost four to ten times as much as comparable vanes. But remember, archery feathers aren't a synthetic product - they are made from the primary flight feathers of turkeys (usually). They must be harvested, cleaned, dyed, cut, sorted, inspected, etc. As you might imagine, this is a labor-intensive process. So archery feathers cannot be mass produced with the same kind of speed and automation as plastic vanes. So they cost more. And the fancier the feather, the fancier the price tag.
Feathers also require a little more care from the user. If you rough handle your feather fletched arrows, they won't respond well to the abuse. Feathers can be bent, crumpled, split, and degraded when they make high-speed contact with other surfaces (like arrow rests). And while a little steam and finger-rubbing can sometimes resurrect defunct feathers, they just aren't as tough as synthetic vanes. So you have to treat them well if you want them to last.
Finally, we should mention weather and the feather. We hear many archers remark that they don't want feathers because of the weather. This is probably an exaggerated prejudice. Feathers are certainly an outdoor product, designed for outdoor use. But not all feathers are the same. The answer to the question "What happens when a feather gets wet?" depends on what kind of feather you're talking about. Fluffy down feathers (like in your pillow) will soak-up water and flatten down like wet hair. But primary flight feathers, like the feathers used for archery, have a much more rigid structure, made from keratin (the same protein found in fingernails), with interlocking rows of barbs, barbules, and hooklets. This interlocking lattice-work allows primary feathers to generally retain their shapes even when wet. So don't assume that a wet feather is automatically a ruined feather. But do consider the weight of the water. A wet feather obviously weighs more than a dry feather, which means your arrow will weigh more and will fly differently when its feathers are wet.
If you are the kind of hardcore hunter who might sit for hours in the rain, you might want to consider waterproofing your feathers. Gateway Feathers offers a waterproofing powder specifically formulated for the task. Or if you want a quick and easy solution, pick up an $6 can of tent or boot waterproofing spray at Wal-Mart. Many archers report this works just as well, and only takes a minute to apply.
Another factor that determines the effectiveness of your fletching is the TURN of the fletch. If your fletching is arranged in a helical (spiral) pattern - like a boat propeller - your arrow will rotate in flight. Much like a football that's thrown with a perfect spiral, an arrow will fly straighter and be more stable if it rotates in-flight. Aerodynamically, a helical configuration is clearly a better choice. However, a helical fletch may not always be appropriate or necessary for your particular bow setup. For example, some arrow rests will not provide enough clearance to allow a helical fletch to pass thru without contact. In this case, many archers use an offset fletch, where the vanes are still straight, rather than in a spiral pattern, but they are slightly turned on the shaft to promote some rotation in-flight without compromising fletching clearance. For very unforgiving arrow rests with limited clearance, or for competition target setups that don't require much stabilization, the straight fletch may be the best option. Take a look at the diagrams below and the corresponding pro's and con's associated with each fletching configuration. When you order your arrows, you'll need to select one of these options.
Click here for larger image.
Please note that some types of fletching can only be fletched certain ways. Feathers generally come in a right-wing or left-wing pre-formed helical shape. So feather fletching will be right-helical or left-helical. Forcing a feather into a straight clamp to produce an offset or straight fletch is not recommended. Also, some specialty vanes, like NAP's Quikspin Vanes, should not be fletched in LH configurations. If you are a fan of the short 2" Blazer Vane, please note that the turn of the fletch will be much less noticeable. Even when fletched with a full helical clamp, a short 2" Blazer Vane will appear to have only a slight offset.
Right or Left?
If you choose to go with an offset or helical fletch, the arrow will rotate in flight. But which way should it rotate? Right or left? The answer is, sometimes it matters, sometimes it doesn't. So here are a few things to think about.
An arrow with a right turn will rotate clockwise (as viewed from the nock) during flight. An arrow with a left turn will rotate counterclockwise. So what's the big difference? With most modern setups ... nothing. One is as good as the other. The only major difference is that left-turn (counterclockwise) arrows tend to impact the target and loosen your tips, while right-turn (clockwise) arrows tend to impact the target and tighten your tips. Otherwise, it really makes no difference.
Nonetheless, the traditional wisdom that RH shooters should shoot a right turn fletch and LH shooters should shoot a left turn fletch still exists. Unfortunately, this thinking is a leftover rule of thumb from the days before compounds and the center-shot cutaway riser. It doesn't apply to modern compounds. But, if you shoot a traditional bow OR you have an old-fashioned flipper or plunger style rest on a non-center-shot riser bow, this is still good advice for achieving the best vane/feather clearance. If you shoot a modern compound with a bolt-on arrow rest, we suggest you choose a RH turn fletch - as a few broadheads and other arrow components are designed to work best with RH rotation.
Fletching Size: How Big to Go?
Most vanes and feathers are available in several different sizes. The most common are the 3", 4", and 5", with the 4" being the industry standard for most applications. However, you may decide a little larger or smaller fletch is better for you. Here are a few things to consider.
Weight: If you're concerned about your finished arrow weight or your F.O.C. balance (more on this in a moment), it's worth noting that your choice and size of fletching material will have a significant impact on both of those attributes. Take a look at the chart below to see how much your fletching choice will add to your finished arrow. Since all of that weight is going to be concentrated in the rear of the arrow, heavy fletching material means a you'll also need more tip weight to maintain a good F.O.C. balance.
Click here for larger image.
In addition to the TURN of your fletching, the second factor that determines how much stabilization you can expect will be directly related to the total amount of surface area of the fletching material you select. Larger fletching will have more surface area, small fletching will have less. The more surface area, the more contact the fletching will have with the surrounding air and the more effective the fletching will be at correcting the arrow in flight. So this is a trade-off between stability and speed. Most bowhunters choose the larger 4" fletching to get better broadhead flight, while most target archers opt for smaller fletching material to optimize speed. Of course, the choice is up to you.
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.