Carbon Arrow Basics & Measurement Standards

Arrow spine charts

SIMPLIFIED ARROW SPINE CHARTS

Some arrow manufacturers have very complex charts which take many variables into account. But other arrow manufacturers offer a more simplified chart with an arbitrary number system, like the sample chart on the right which just references draw weight and arrow length. If you go by the simple chart method, then you’ll need to apply a little common sense – particularly if your bow setup isn’t exactly ‘average’. For example, if you shoot a typical 310 fps compound bow, with normal 100 gr tips and 75% let-off, the simplified chart works fine. If you know your bow is set for 60# and you use 29″ arrows, you just follow the dots on the chart and choose the 2000 spine size. Easy! But what if you shoot a very aggressive speed-bow with a 350 fps IBO Speed? In that case, your bow will have more output than the average 60# bow. You might need to accommodate by choosing a little stiffer spine like the 3000 shaft, right? And what if you prefer a heavier 125 grain tip, what then? We appreciate the easy reference of simplified charts, but they’re not always the best utility. If you would rather not use the simplified method, then we suggest you get to know the concept of actual spine deflection. And don’t worry. It sounds a lot more complicated than it is.

WHAT IS ACTUAL SPINE DEFLECTION?

There is a difference in an arrow’s published spine size and the arrow’s actual spine deflection. Published spine sizes can be anything (a number system, color codes, letters of the alphabet, etc.) but an actual arrow spine deflection is expressed as a direct technical measurement. According to the modern standards (ASTM F2031-05) an arrow’s official spine deflection is measured by hanging a 1.94 lb. weight in the center of a 28″ suspended section of the arrow shaft (not to be confused with the old AMO standard of 2 lb. and 26″). The actual distance the 1.94 lb. weight causes the shaft to sag down is the arrow’s actual spine deflection. For example, if a 1.94 lb. weight causes the center of a 28″ arrow to sag down 1/2 inch (.500″). Then the arrow’s spine deflection would be .500″. Stiffer arrows will, of course, sag less. More limber arrows will sag more. So the stiffer the arrow is, the LOWER its spine deflection measurement will be. The more limber an arrow is, the HIGHER its spine deflection measurement will be. Make sure you understand the relationship of spine deflection and stiffness. A lower number is stiffer. Many customers get this backwards. For example, an Easton 340 (.340″ deflection) is dramatically stiffer than an Easton 500 (.500″ deflection) – not the other way around.

STANDARDIZED SPINE CHARTS BASED ON DEFLECTION

We suggest it is far more reliable to reference the deflection data on standardized charts. These charts are normalized for modern compound bows with IBO speeds between 280-330 fps. For faster bows, read chart one block down and to the right. For slower bows, read chart one block up and to the left. Chart not applicable for traditional bows. Again, please note actual arrow spine deflections do not necessarily match the manufacturer’s marketed spine sizes. For example, a “Carbon Express Maxima 250″ has an actual spine deflection of .404″, not .250” as the sizing suggests. Never assume an arrow’s published spine size matches the arrow’s actual deflection. Look up the real deflections and base your choice on that.

BASED ON THE GOLD STANDARD

WHY HAVE SO MANY SPINE SIZE SYSTEMS?

The next section is technically exhaustive, but worth the read. Once you know about spine deflection measurements, picking arrow shafts will be easy from now on. To understand the issue of arrow spine deflections and why they aren’t just standardized, like tire sizes or plumbing fixtures, you must understand something about the history of the arrow industry. The gold standard for rating arrow spine has always been Easton’s fitment charts. Before carbon arrows hit their stride in the 1990’s, practically every archer in the world had at one time studied the little blocks on the Easton chart, trying to decide if the 2219’s, 2413’s, or 2315’s would be better (remember?). The basic rating system wasn’t really hard to understand. The first two numbers were the arrow’s diameter (in x/64th’s of an inch) and the second two numbers were the shaft’s wall thickness (in x/1,000th’s of an inch). So a 2315 was an arrow shaft with a 23/64″ diameter and a wall thickness of .015″. Easy enough. But what did that really mean? The rating system had nothing to do with arrow spine, directly anyway, and the numbering system wasn’t necessarily sequential. A 2315 arrow was actually heavier and stiffer than a 2413 arrow. A 2219 was surprisingly heavier than a 2512, but not as stiff. And a 2314 and a 2315 oddly weighed the same but had different deflections. Okay, it wasn’t so easy. But Easton’s engineers crunched all the numbers and the handy aluminum arrow charts solved all the woes with their nice little organized blocks.

CARBON ARROWS SCREWED EVERYTHING UP

Then carbon arrows came along and made things easier … almost. Since carbon arrows had a much broader ranger of application, there was no need for 10 to 15 sizes of the same arrow. For most carbon arrows, 3 to 5 sizes covers virtually every application. So Easton simplified the sizing system by basing the sizes on actual spine deflections. Easton’s familiar carbon arrow spine sizing system (500, 400, 340, 300) is basically the arrow’s spine deflection x1000. So a 500 shaft is a .500″ deflection. A 340 Easton shaft is a .340″ deflection and so on. So forgiving the shift of the decimal, the Easton spine sizing system matches up nicely with actual spine deflections. Unfortunately, the system is somewhat counterintuitive. For Easton/Beman arrows, the lower numbered shafts are actually the stiffer heavier shafts, and the higher numbered shafts are the more limber and lighter shafts. This naturally goes against the bigger is more line of thinking. Since most people don’t know how spine deflections are obtained, or why they matter, some archers will simply buy the “larger” size for heavier bows and “smaller” sizes for lighter bows. Of course, this is completely backwards. So everyone ended up back at the Easton charts studying the little blocks again. And why not? No archery pro-shop is complete without a big Easton chart on the wall. So why mess with tradition?

CARBON ARROWS TAKE COMMAND OF THE MARKET

Turns out, Easton wasn’t the only player in the carbon arrow game. In fact, they were one of the last to join-in when they purchased Beman in 1995. By that time, Gold Tip already had a five year head start with their popular graphite arrows. And Gold Tip had really simplified things with an easy 3 size system, the famous 3555, 5575, and 7595. The system was intended to be self-explanatory. The 3555 roughly fit a 35-55# bow, a 5575 fit a 55-75# bow, and a 7595 fit a 75-95# bow. At least that’s how most archers understood the sizing. But it didn’t always work out that way. The Gold Tip arrows had spine deflections of .500″ (3555), .400″ (5575), and .340″ (7595) respectively. So for example, a 53# bow shooting a 30″ arrow actually required the 5575 spine (per the Easton gold standards anyway) instead of the 3555 that Gold Tip’s sizing convention might suggest. So it wasn’t long until Gold Tip published their own charts (yes, with the little blocks), based essentially on the Easton spine deflection data. To be fair, Gold Tip’s system really wasn’t so bad, comparatively anyway. There was worse to come.

MUDDY WATERS

Not to be outdone, Carbon Force Arrows, a division of PSE, decided to really simplify things and make their sizes completely sequential … 100, 200, 300, and 400. So the larger the number, the heavier and stiffer the arrow. Fine! But this scrambled all of our brains even worse because their arbitrary sizes actually overlapped the actual arrow deflections. The Carbon Force 100 has a .500″ spine, the 200 has a .400″ spine, the 300 has a .340″ spine, and the 400 has a .300″ spine. Try to wrap your noodle around that! And just as our grey matter started to congeal from Carbon Force, Carbon Express reinvented their generally understandable 30/50, 45/60, 60/75 system (similar to Gold Tip’s system but with the same drawbacks) to a system that’s not just arbitrarily sequential (150, 250, 350), but varies from shaft to shaft. Their Maxima 250, for example, has a spine deflection of .404″, but the Maxima Hunter (camo) 250 has a spine deflection of .417″. Oh boy!

ALL CROSS-REFERENCING LEADS BACK TO EASTON

We’re not trying to toot Easton’s horn, but it boils down to this. Whether you like Easton arrows or not, Easton is the big dog in the arrow market. And Easton’s competitors don’t want to be seen as “copycatting” Easton by following Easton’s sizing format. They want to be unique and develop their own marketing and sizing system for their products, even if it ultimately leaves us all confused. There are well over a dozen popular carbon arrow manufacturers who sell carbon arrows in the U.S., and all of them are trying to sing their own tune. Just imagine if you went to buy a new set of P225/60R17’s for your SUV but the various tire brands were sized using different systems (Red60-400, 6022/175, SUV522/6017). Absurd, right? It would be a nightmare behind the counter trying to cross reference all that. But that’s exactly how we do it in the archery industry. It’s still the Wild West in our little niche market and everybody wants to be the new sheriff in town. For archery enthusiasts this is both good and bad. Competition and innovation will continue to keep prices low and product quality high, but we’ll all have to continue to put our thinking caps on when we shop for arrows.

NO UNIVERSAL SYSTEM – GET USED TO IT

There are no universally agreed spine sizes among the various arrow manufacturers. But the system of actual spine deflection is universal, because those measurements are guided by industry standards. That’s the only apples-to-apples system that applies to every brand and model of carbon arrow. As long as the various carbon arrow manufacturers provide their spine deflection data (and they test using the industry standard method), manufacturers can size and market their arrows by any system they like, and we can still reference the proper application from the gold standard Easton charts using actual spine deflections.

Arrow straightness sells

DOWN TO THE THOUSANDTHS

What makes one carbon arrow cost $149 a dozen and another cost $69 a dozen? There are a number of ways a particular carbon arrow might be perceived as a “premium” arrow (cool graphics, clever nocks/inserts, special materials, flashy marketing, etc.), but nothing affects the market value of a carbon arrow like advertised straightness, where the difference between the penthouse and the trailer park is just five thousandths of an inch. An arrow that’s advertised to have a +/-.001″ straightness is automatically an elite pro-grade arrow worth big bucks. An arrow with a lowly +/-.006″ straightness is the entry-level hunter grade arrow which is sold as a basic commodity. Make sense? Most carbon arrows are advertised to have a specific straightness tolerance between .001″ and .006″. You won’t find many arrows with straightness tolerances outside that range. This is what the customer base expects and accepts. So that’s what we get, and the pricing is fairly linear and predictable from +/-.006″ to +/-.001″. The straighter the arrow, the more expensive it typically will be. Does that make sense mathematically? Probably not. The entire spectrum spans a few widths of human hair. Nevertheless, that’s the carbon arrow market – where straightness is king.

HOW TO THEY MEASURE THAT?

Before we get too deep into this topic, it’s worth noting that there doesn’t seem to be an accepted universal method for HOW arrow straightness is measured. Per ATA/ASTM standards, arrow straightness should be measured along the full length of the shaft minus two inches. But as we understand it, this is NOT how things actually go inside the industry. On a number of occasions, we have heard arrow companies accuse each other of cheating their straightness measurements – either by measuring only short sections of their arrows, or by obtaining their straightness numbers via undisclosed measurement methodologies. Every arrow manufacturer is absolutely sure their numbers are accurate and their competitors’ numbers are fabricated. If you think the bow business is cut-throat, you should witness how the arrow companies go at it behind closed doors. To avoid being shanked at the next trade show, we’ll stay neutral and assume that everyone’s’ arrow straightness numbers are reasonably honest. But just be advised, there are certainly some cowboys in this market. A tolerance of +/-.001″ is good work for a CNC mill on aluminum alloy. The idea that a piece of thin flexible tubing can hold that tolerance along a full 28″+ length is, well, quite fantastic.

STRAIGHTNESS CLASSES: GOOD, BETTER, BEST

Arrows are essentially priced on the good – better – best model, like many products. We all know how that works. Maybe you just want the regular, or maybe you’re a premium high-octane kind of buyer. Well, let’s examine the typical straightness “classes” of arrows and see how this works. Most standard-grade carbon arrows have an advertised straightness of +/-.005-.006″. These shafts are usually marketed exclusively to the hunter and beginning archers. For the purposes of big game hunting and general target use, standard-grade shafts are more than adequate. A typical human hair is about +/-.002″-.004″ in diameter, so even a basic carbon shaft of +/-.006″ straightness is quite remarkable, and much straighter than you could possibly perceive without specialized equipment. But these “basic” arrows sell cheap (under $80/dz typically). To entice buyers wanting something a little better, most arrow shaft manufacturers also offer mid-grade shafts which will have an advertised straightness of around +/-.003-.004″ along with a moderate pricing premium. But for the real experts, for the high-octane buyers who only get the best, every arrow maker has their pro-grade shafts which claim a straightness of +/-.001-.002″, which is truly outstanding. As you might expect, these premium grade arrows fetch a premium price (+$130/dz). If you’re the kind of buyer who spares no expense, then by all means, buy the straightest shaft you can find. But before you shell out the green for a +/-.001″ shaft, there are couple things you might want to know.

CUT FROM THE SAME CLOTH

The difference in a +/-.006″ shaft and a +/-.001″ shaft is more razor-thin than you might think. Today, most carbon arrow shafts are constructed by taking very thin layers of carbon sheets and rolling them up into perfectly straight tubes (usually 6ft. long or so), much like you might roll-up a big map. The layers are wound around a metal mandrel, then the carbon tubes are heat-treated to bond all the layers together. When the heating process is complete and the carbon tubes cool down to room temperature, they are cut into sections (raw shafts). Some of the shafts, particularly those that come from the center of the roll, retain their ±.001″ straightness while other sections distort slightly from the heating/cooling process. As we understand it, the results vary from run to run and day to day. In most cases, even the manufacturer doesn’t know how the day’s crop of shafts will come out. But once the shafts are made, the manufacturer measures the straightness of each shaft section and sorts them accordingly for banding and sale. One sort may be named and marketed as one arrow, another sort as something else. For example, the Beman Bowhunter +/-.006″ and the Beman ICS Hunter +/-.003″ are just two different sorts of the same shaft – same raw materials – same construction technique – different wrapper. Same is true for the popular Gold Tip Hunter ±.006″, Gold Tip Hunter XT ±.003″, and the Gold Tip Pro ±.001″ shafts. They’re not different arrow shafts. They’re just different cuts of the same raw product.

CAREFULLY GUARDED SECRETS

Small variations in the daily manufacturing environment (humidity, pressure, air convection patterns, etc.) along with tiny deviations in the characteristics of the raw materials ultimately determines the straightness of the finished product. On one particular day, the manufacturer might yield an entire batch of +/-.001″ shafts, or an entire batch no better than +/-.006″, or even a mixed bag of straightnesses, all from the very same processes and materials. The finer tricks of the trade are carefully guarded secrets, as the art of consistently building straighter arrow shafts is literally a technical exercise in splitting hairs. But make no mistake, arrow manufacturers would rather avoid the +/-.006″ days. The more ±.001″ days a manufacturer has, the more money they can make. Why? Because straighter shafts are worth more in the marketplace, whether they cost more to manufacture or not. So don’t be fooled into thinking that your set of $129 +/-.001″ pro-grade shafts are somehow fundamentally better constructed, stronger, or made from finer high-tech materials than basic $69 a dozen +/-.006″ hunting shafts. This is seldom the case. Most of the time, the difference in their regular unleaded and premium is just a few thousandths of an inch. There is even some discussion suggesting many of today’s +/-.006″ shafts aren’t really +/-.006″ shafts at all. They’re better than that – mostly +/-.003-004″ shafts. But since arrow manufacturers sell a LOT of entry-level shafts, they need product to fill those orders. If enough of the crooked +/-.006″ shafts aren’t available, they build-out the entry-level shafts with the next best sort. Ha! Free upgrade. Who doesn’t love the sound of that?

Does arrow straightness matter?

OF COURSE IT DOES

From a pure physics standpoint, yes! Arrow straightness certainly does matter. We all remember how a bent aluminum arrow fishtailed and corkscrewed wildly. Yes! Straighter arrows undeniably fly more accurately. In long-range laboratory conditions with a mechanical shooting machine, the straightest arrows with the best spine consistencies will always group best. But try to keep this issue in reasonable perspective. You are not a mechanical shooting machine. You don’t shoot in laboratory conditions, and you probably don’t shoot at extreme distances (100+ yards). The straightness difference in a +/-.006″ arrow and a +/-.001″ arrow is mathematically minuscule. We’re not talking about the kind of distortion you would see in a bowed 2×4 at Home Depot. We’re talking about tiny hair widths. So we have to admit, the real world benefit of a +/-.001″ arrow probably has more to do with selling arrows than shooting arrows. The truth is, only a handful of the world’s archers actually have enough shooting skill to truly differentiate between a very good +/-.003″ arrow and a “pro grade” +/-.001″ arrow. And within the typical bowhunting range, any difference would be practically imperceptible. Nonetheless, bowhunters tend to attribute their successes or failures to their equipment rather than to their actual skills. So owning and shooting a set of professional grade +/-.001″ arrows may provide some bowhunters with an edge in confidence, even if the actual technical advantage is negligible. If you’re one of the many archers who believe that success is only one more purchase away, buy whatever arrows you like. Just remember that super-straight arrows won’t correct poor shooting form. In the end, the benefits of a good practice regimen and proper bow tuning will FAR outweigh the benefits of shooting expensive arrow shafts. But don’t tell the arrow companies we said that.

ARE CARBON ARROWS STRAIGHTER THAN ALUMINUMS?

Yes and no. While a carbon arrow’s advertised specs may be no straighter than a typical aluminum shaft, carbon arrows resist distorting and “bending out of shape” much better than aluminum arrows. Though an aluminum shaft may BEGIN with a similar +/-.003″ straightness, its straightness quickly deteriorates through normal use and handling. So after a few months of use, your aluminum arrow set may contain a few arrows that are at original specs and some that are grossly out of straightness. Carbon arrows generally do not retain this kind of “memory” after being stressed (bent). So your carbon arrow set stays much more straight and uniform – even with heavy use. Some archers even joke that there are only two states of a carbon arrow: straight or broken, but never bent. While that’s not entirely accurate, it does help to illustrate the point.

SPINE CONSISTENCY PROBABLY MATTERS MORE

Remember how we mentioned the cut-throat squabble about arrow straightness? Well, the same is true for spine consistency, and this spec is sometimes discussed as a matter of manufacturing tolerance. So we’ll mention it here. If you test for spine deflection while slowly rotating the arrow, the spine deflection should remain constant. No matter which direction you bend the shaft, it should be equally resistant at all points, right? Nope! The wound layers of a carbon arrow will often have a seam somewhere inside the circle (unless the shaft is filament wound). This seam creates an imbalance in the spine consistency of the arrow, such that the arrow is a bit more stiff at one point around the circle. It’s unfortunate, but the process by which carbon arrows are manufactured inevitably results in some imperfections. And if you want to get really technical, most arrow shafts aren’t even perfectly round for that matter. But the important question is, does it really make a difference? From a pure physics standpoint, yes. But again, few shooters have enough skill to notice small variations. For the weekend bowhunter and backyard enthusiast the issue is largely inconsequential. But that doesn’t stop the arrow companies from bickering about who has the best spine consistency and accusing each other of spine crimes. After all, every arrow company wants YOU to believe that their arrows will give you a technical advantage, even if that’s a little distortion of the truth. Again, we’ll avoid the internal melee here by not pointing fingers, but if you wish to know more about spine variance, check the forums. There are a few forum regulars out there who own spine testing devices and Hooter Shooters. And they’ll be happy to disagree with us on this issue. Despite the debate, consumers remain surprisingly blasé about spine consistency, and most manufacturers struggle to make technical hay about their spine consistency specs. Most buyers are just fixated on straightness.

Arrow diameter madness

THE NEEDLE AND THE SWORD

Here is another issue that probably gets more press than it deserves – arrow shaft diameter. The mainstream hunting arrow market is dominated by the 9/32″ and 5/16″ ICS style shafts. If you haven’t held a modern carbon arrow, they’re about the diameter of a Bic Pen or a #2 Pencil. This “standard” diameter carbon arrow has been around for more than two decades. We like them. They work. Some arrow manufacturers never stray far from this convention (at least for the hunting market). But others are constantly trying to push the narrative that smaller diameter arrows are better (and worth a pricing premium of course). Sometimes they’re referred to as Slim or Micro-Diameter or even Ultra-Micro Diameter and they are typically 1/4″ to 17/64″ O.D.. Since small diameter shafts don’t accept standard nocks and inserts, they all come with their own propriety components (and associated headaches). But that’s okay. The small-diameter shaft promises to be “harder hitting” and “deeper penetrating”, and as a strict technical matter that might actually be true. The tip of a needle certainly penetrates flesh more easily than the tip of a sword. Nevertheless, we submit there’s some monkey business in such marketing. If a “micro-diameter” arrow is .250″ (1/4″) and an ICS standard shaft is .3125″ (5/16″), then we’re really talking about a maximum difference of just 1/16th of an inch – about the thickness of a dime. Is it really possible this 1/16th of an inch could make such a profound difference in hunting penetration? Hmmm. We will leave the final conclusion to your good common sense, but we suspect this is another situation where the benefits of a “premium” product are more apparent at the cash register than in the treestand. The best selling aluminum arrows of the 80’s and 90’s were all in excess of .343″ O.D. So perhaps the standard ICS style carbon shafts are already small diameter arrows. But as long as consumers see micro-diameters as an innovation, the current narrative is likely to continue.

Plastic vanes or real feathears?

FLETCHING BASICS

Glued near the rear of most arrows are 3 (sometimes 4) plastic vanes or feathers, arranged in an equally spaced pattern around the circumference of the shaft. These parabolic-shaped pieces of material (collectively called the “fletching”) serve to steer and stabilize the arrow during flight, like fins on a rocket. If the arrow is flying perfectly straight, 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, and if you want your arrow to fly where you aim it, you need some. But which kind? 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 at the top.

STANDARD PLASTIC VANES (RUBBER BASED)

Standard 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. If they do manage to get wavy or stretched out of shape, they can be easily heat-treated with a hair dryer to make them pop back into shape. So vanes are clearly the low-maintenance choice. The only major downside is weight. Compared to feathers of the same size, vanes are heavier, as much as 3X the weight of a comparable length feather. And it’s also worth considering how the smooth surface of a vane doesn’t “dig-into” the air as well as the rougher corrugated surface of natural feathers (nature knows best perhaps). 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.

SPECIALTY VANES (HIGH-PROFILE)

The standard vane is an enduring staple item of the industry, and it’s the most widely used type of vane, but in our industry 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 high-profile (aka,Blazer) vane. There are a few variants, but the high-profile vane is typically a 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 any marketing wizardry and technical hoo-hah) is still a tiny 2″ vane – with the surface area of a 2″ vane. So realistically, a big aerodynamic benefit claim might be a technical stretch. Nonetheless, high profile 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 short high profile vanes more and more often. The only obvious downsides are increased cost (roughly +$5 p/dozen arrows over standard vanes) and the fact that they can be fussy to fletch (which is generally our problem rather than yours). We’ve fletched countless thousands of these high-profile vanes and we can tell you one thing for certain. If you don’t have just the right glue, the right temperature, the right humidity and the right music playing in the background, they might not stick. If you’re a home fletcher, keep this in mind before you decide to go with the stiffer high profile vanes. They can be a pain in the neck to work with.

FEATHERS (TURKEY FEATHERS ACTUALLY)

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″ standard vanes). This means your arrows fly faster with less loss of trajectory downrange. As we mentioned, 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. Feathers also 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 times as much as standard vanes. They are made from the primary flight feathers of turkeys (usually). They must be harvested, cleaned, dyed, cut, sorted, inspected, etc. And this labor-intensive process costs money. So archery feathers cannot be mass produced with the same kind of speed and automation as plastic vanes, and the fancier the feather, the fancier the price tag. Apart from the pricing premium, you should be aware that feathers require more care from the user. If you rough handle your feather-fletched arrows, you’ll likely ruin your feathers in short order and they will need to be replaced. This isn’t to say that feathers are entirely delicate. A little steam and fiber-rubbing can sometimes resurrect defunct feathers, but they simply aren’t as durable as synthetic vanes. And feathers absolutely will not tolerate high-speed contact with hard surfaces (they don’t particularly like Whisker Biscuits either). If you want to shoot feathers, you need to treat them well and make sure your bow is tuned-up correctly.

DON’T FEATHERS GET WET?

Yes and no. We hear many archers remark that they don’t want feathers because of the weather, but 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.

Fletching turn

STRAIGHT, OFFSET OR HELICAL?

Another factor that determines the effectiveness of your fletching is the turn, or angle of the fletch on the shafts. 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 pros and cons associated with each fletching configuration. When you order your arrows, you’ll need to select one of these options.

STRAIGHT

Pro: fastest flying vane configuration
Pro: least amount of air resistance
Pro: works with any arrow rest
Pro: minimal fletching clearance problems
Con: less stable at long distances
Con: less stabilization for broadheads
Con: best used in a well-tuned bow

OFFSET

Pro: better broadhead stabilization.
Pro: minimal air resistance in flight
Pro: works with most arrow rests
Pro: stable flight to intermediate distance
Con: needs more fletching clearance
Con: loss of velocity (tiny)MOST POPULAR CHOICE

HELICAL

Pro: best broadhead stabilization
Pro: most consistent arrow flight
Pro: increased overall distance accuracy
Pro: corrects flight attitude problems
Con: loss of arrow velocity in flight
Con: fletching clearance problematic
Con: not compatible with containment rests

A FEW LIMITATIONS

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 always be helical. Forcing a feather into a straight clamp to produce an offset or straight fletch is not recommended (distorts the cupped shaped of the feather). Also, if you are a fan of the short 2″ high profile vane, please note a few degrees of offset over a short 2″ span will not be obvious with a visual inspection. As you might imagine, this causes some confusion (and customer service drama). So we generally sell and fletch 2″ high profiles in the straight configuration only.

WHAT ABOUT RIGHT VS 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 regarding flight. The only major difference is left-turn fletched 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 belief that RH shooters should shoot a right turn fletch and LH shooters should shoot a left turn fletch still persists. 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. If you shoot a modern compound with a bolt-on arrow rest, choose a RH turn fletch and call it a day. 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, by all means, match the fletch and the hand. We generally don’t list LH turn options on our online ordering system (to avoid confusion), but if you want a LH configuration please call 877.410.7811 and we’ll talk it over.More fletching choice considerations.

FLETCHING SURFACE AREA

The larger your fletching, the larger the surface area and contact patch with the wind. So a larger 4-5″ fletch certainly has some aerodynamic advantage when it comes to correcting unstable arrow flight. If you shoot a big gnarly fixed-blade broadhead, or if you’re a finger/traditional shooter, you should definitely get the larger fletching material. You’ll need it. But if you shoot a well-tuned modern compound with a mechanical release and expandable broadheads, a 2-3″ fletch will be plenty. A jumbo fletch on a prime modern rig is arguably just dead weight.

FLETCHING 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 an impact on both of those attributes. Three standard 4″ vanes will add about 24 grains to your total arrow weight. Three standard 3″ vanes are about 19 grains, and three of those fancy high-profile vanes weigh in at roughly 18 grains. As we mentioned earlier, feathers are notably lighter (about 9 grains for three 4″ feathers and 6 grains for three 3″ feathers). So if getting the fastest possible arrow speeds is a critical consideration for you, this is a no-brainer. Nothing is going to go faster than feathers. But let’s keep this in reasonable perspective. Shaving 10 grains of arrow mass equates to a 2-3 fps speed increase on a typical modern bowhunting rig. So the difference in a “heavy” 4″ vane and a lightweight 3″ feather, realistically, will be just 6-8 fps at the chronograph. Whether or not that’s a critical difference is up to you to decide.FOC (Front of center balance)OPENING THE CAN OF WORMS` We mention this issue with a certain degree of caution, as it often provides more of an academic exercise than a pragmatic way to select arrows. If you’re not familiar with the concept, FOC (front of center or sometimes forward of center) refers to the balance point of the arrow, end to end. If you’ve ever played 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 flip 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 on the leading side. As such, an arrow, like a dart, should be heavier in the front than in the back. But how much? Where’s the “perfect” balance point? Most experts suggest a balance point of 7-15% front/forward of center.

BEFORE WE WADE IN

We should get in a quick reality checkpoint before we discuss this. If your FOC is really really out of whack, it’s an issue, but most common arrow components tend to yield finished arrows well within the recommended 7-15% FOC range. If you’re buying typical hunting arrows, it’s going to be a non-issue. Move on. 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 macho man 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.

HOW IS FOC COMPUTED?

If you balanced a standard raw arrow shaft (no components), the balance point would be the middle of the shaft (0% FOC). But since tip + insert at the front of the arrow is usually heavier than the fletching + 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 right, the 30″ long arrow has balance point that is 3″ forward of the arrow’s physical center. So its FOC is found by dividing the shift of the balance point by the total arrow length (3/30) or 10%. This means that the arrow’s actual balance point is 10% forward of where it should be if both ends were weighted equally. Get it?

DOES IT REALLY MATTER?

Yes. 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 you might think of this as a trade-off to consider, but again, if you’re ordering standard hunting arrows, the FOC exercise will almost certainly be academic. It’s a problem that really isn’t a problem until we make it one. Nevertheless, this is a commonly debated issue among archery enthusiasts. In fact, some of the self-proclaimed chat board gurus seem intent on beating the FOC issue to death. We submit it’s a dramatically over-analyzed topic. There! We said it.

DONT READ THIS PART

If you’re going to join the FOC math club warriors, 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 a “mathematically optimal” FOC very difficult to prove. To make matters worse, there are a couple variations on how FOC itself is calculated (some include the tip of the arrow in the length measurement, some stick with the AMO arrow length measurement, etc.). If you want to get out your scientific calculator and give the ballistic physics a whirl, more power to you. But be advised, most people inside the industry, including the arrow manufacturers, routinely roll their eyes when customers start talking about FOC. We’re not saying you shouldn’t be aware of it, but just be advised, you’ll be “that guy” if you make a big deal about FOC at the pro-shop counter.Trends & recommendations

THE POPULAR CHOICES

Just so you know, the 3″ offset vane is king. If we fletch 100 dozen arrow orders, at least 50 of those orders will be for 3″ offset vanes (in bright colors). The next 30 orders will be for 2″ high-profile vanes (in bright colors) and the remaining 20 orders will be a mixture of 4″ vanes, feathers, straight and helical turn fletching. We’re not suggesting you jump off a fletching bridge just because your friends do, but we thought it might be helpful to know what most bowhunters are actually buying, and that is 3″ offset bright colored vanes. They work.

FLETCHING COLORS

Oddly enough, we frequently have dialogue with customers about fletching colors. While the color of the fletch might seem incidental and inconsequential to some, others regard this as an important choice. Frankly, we’re not sure if it makes a difference or not. It’s unclear whether or not your choice of fletching colors might cause you to get “busted” in the woods. Could a deer spot your flo-yellow and red vanes? Maybe. Perhaps brown and green fletching is best for bowhunting, but we can’t be sure of that. However, we can be sure about what humans can see best. Every archer has had the experience of an arrow that seemingly disappears into short grass or leaf litter, despite an exhaustive search to find it. And if you do manage to finally find it, you’ll likely have your fletching colors to thank. Bright colors, particularly colors which contrast with colors in the woods (like hot pink and blue), are easiest to locate in the forest. With all that said, we can’t confidently say which colors are best for you, but we can tell you what other people buy. The most popular fletching colors, by far, are flo-green and flo-orange. White, red and yellow are also popular, but nothing comes close to flo-green and flo-orange. When we order fletching supplies, we literally quadruple the quantities for those two colors. The least popular color – brown. Nobody ever picked brown. We stopped stocking brown a couple seasons ago. There’s just no love for brown.

Arrow mass & safety standards

THE BASICS

The actual weight of your finished arrow is also very important. Arrows which are too heavy will fly too slowly and with too much loss of trajectory. Lighter arrows fly more quickly, but arrows which are too light can damage your equipment. So you’ll need to know a thing or two about arrow mass and industry safety standards before you start sorting through those GPI specifications. How heavy should your finished arrows be? It depends. Let’s start at the top. First thing, the weight of an arrow (as well as projectiles in most shooting sports) is customarily measured in GRAINS. Grains (gr) and grams (g) are totally different units of measure. So don’t confuse them. The grain is a British system unit – based on the weight of a grain of barley. A gram is a metric unit. So let’s just try to just forget about grams for now and focus on grains. A grain is very small unit of weight (only 1/7000th of a pound), so if you would like to have the ability to accurately weigh your own arrows, you’ll need a specialized scale. You can purchase an archer’s scale that’s specifically calibrated in grains for under $50. However, when you order custom arrows from Hunter’s Friend, your arrow set will arrive already weighed and certified by one of our professional arrow builders.

ARE LIGHTER ARROWS BETTER?

This is always a hotly debated topic. Before we wade in, you should understand lighter arrows fly faster with less loss of trajectory. A faster arrow won’t necessarily penetrate better, but it will make it to the target more quickly. For some bowhunters and 3D shooters, this is a great benefit. A bow that shoots very fast is often described as “shooting flat”. The “flat” part is a reference to the natural rainbow-shaped parabolic flight-path that all arrows invariably take. A faster arrow travels with less perceptible arc, so it is described as shooting “flat”, although “flatter” might be the more accurate word. Either way, a fast flat-shooting arrow is something many shooters seek in a bowhunting or 3D rig. In the current archery market, speed sells. Right or wrong, it’s a fact. Like in many industries, archery manufacturers are under constant pressure to make things go faster. As a result, each year brings a new bumper-crop of lightweight arrow shafts, better string materials, more efficient bow designs, friction-reducing components, etc. Again, there is some disagreement on this issue, and we’ll hammer out the pros and cons in a moment, but the main idea is, lighter arrows go faster – sometimes dramatically faster. Heavy arrows go slower. So if you want your bow to shoot “flat”, lightweight arrows are going to be a must, but like with most things in archery, there are trade-offs to consider.

IS THERE A LIMIT? HOW LIGHT IS TOO LIGHT?

Shooting an arrow that is too light can be dangerous, both to you and your expensive compound bow. Shooting an underweight arrow has a similar effect as dry-firing your bow. Without sufficient arrow weight, the string and limbs of your compound bow move too quickly and violently. It’s like putting your car in neutral and flooring the gas pedal. The bow needs the resistance of the arrow to slow it down – so it doesn’t “rev” out of control. Of course, an underweight arrow will fly like a rocket – generating unbelievable speeds. But anyone who does this is just asking for trouble. Modern compound bows aren’t toys. They generate a tremendous amount of energy and should be treated with the same respect you would give any dangerous weapon. The vast majority of serious compound bow failures are not caused by manufacturer defects, but rather by dry-firing the bow or shooting dramatically underweight arrows. For your personal safety, and the longevity of your bow, we strongly recommend you follow the IBO Standards regarding minimum arrow weight.

THE BIG 5 GR/LB STANDARD

The International Bowhunting Organization (IBO) sets a 5 grains per pound standard that’s pretty simple to follow. Arrow weight (in grains) must be at least 5X the bow’s draw weight. So a 60# bow should shoot no lighter than a 300 (5 x 60) grain arrow. Simple enough. Another authority in the archery industry, the Archery Trade Association (formerly the AMO), also publishes an arrow weight recommendation chart called the AMO Minimum Arrow Weight Chart. The AMO chart is a bit more complex and takes more variables into account (brace height, bow efficiency, cam design, draw length, etc.), but it is less widely used today. If you have a modern compound bow from the last 15 years or so, it’s probably safe to assume the IBO standard applies. Since the IBO minimum arrow mass standard applies at 3D courses, many competitive shooters setup their arrows to weigh exactly 5 grains per pound. This keeps them just within the rules while providing the fastest possible arrow speeds. However, bowhunters often choose more moderate arrow weights – though certainly not always. Either way, please be aware of this hard safety minimum and never shoot an underweight arrow.

FISH AND GAME LAWS

We strongly suggest you check your state regulations before ordering your hunting arrows. A few states still require a minimum total hunting arrow mass and/or a minimum GPI for a hunting arrow to be legal. Always respect your state’s rules and regulations, and be advised that your state’s rules and regulations may change from year to year. As a sportsman, it’s your responsibility to know the (current) laws where you hunt and to make sure your equipment is in compliance from season to season.Speed & kinetic energy

SPEED! GLORIOUS SPEED!

Fast cars, fast computers, fast wide receivers, fast-drying paint, fast-acting weed-killer – if it’s fast, we love it. And when it comes to our archery equipment, it’s no different. Show most guys a brand new bow, and their first question is likely to be “How fast does it shoot?” Right or wrong, speed is a major consideration for most archers. And it’s great to see how advancements in materials and design technologies have made today’s compound bows better, faster, and more fun to shoot than ever before. Of course, there will always be a few dissenters in the crowd, those who’ll loftily claim they don’t care about speed. But the market trends don’t lie. Archery consumers are taking advantage of these innovations, buying high-performance bows and speed-boosting gadgets by the trainload. And nothing yields such a predictable and significant increase in speed like a good set of lightweight carbon arrows. So let’s examine the pros and cons to shooting lightweight arrows. Let’s find out where they help, where they hurt, and where they don’t really make a difference.

ARROW MASS VS. SPEED

When all other variables are constant, arrow speed has an inverse relationship with arrow mass. Of course there is a point of diminishing returns, but as arrow mass increases, arrow speed decreases. As arrow mass decreases, arrow speed increases. Your bow will only generate a certain amount of energy (given its particular settings), and it uses that energy to get the arrow moving. The less the arrow weighs, the faster that energy can make the arrow accelerate. The heavier the arrow, the less acceleration is achieved. Interestingly, a bow transfers energy into a heavier arrow more efficiently than it does into a light arrow (more on this in a moment). Nonetheless. the rule still applies, lighter arrows go faster – heavier arrows go slower. But by how much? We’ll show you …

REAL WORLD EXAMPLE

To illustrate this point, we prepared 7 arrows, ranging from 350 grains up to 500 grains in precisely 25 grain increments. We grabbed our demo PSE Stinger-X from the pro-shop and headed to the chronograph room. The bow was set for exactly 70 pounds of draw weight and 29 inches of draw length. With no additional fanfare, we then fired each test arrow through the chronograph and recorded the results. We weren’t trying to do a serious scientific speed test, but rather to just illustrate the point about arrow mass vs arrow speed, and the results are pretty predictable. As you can see, as arrow mass increased – arrow velocity decreased. If you work out the KE, you might notice how, mathematically, the inverse relationship isn’t exactly linear, but the trend is clear. Got it!Is faster necessarily better?

DEPENDS HOW YOU LOOK AT IT

From a standpoint of accuracy, you may find that lightweight arrows will yield some surprising benefits. No matter how fast an arrow is, it will begin to lose trajectory the moment it is released from the bow. As it succumbs to the effects of gravity and air resistance, its flight path (trajectory) changes and the arrow eventually begins to drop back to earth. Arrows which fly more quickly hold their trajectory better than slower arrows. So archers who shoot lighter-faster arrows will have less need to adjust for distance – since the faster arrows will hold a “flatter” trajectory within a given distance. We’re not suggesting slower arrows fly more erratically or unpredictably – not at all. In terms of predictability, a slow arrow is just as accurate as a fast arrow.  But a faster arrow allows you to make more mistakes in yardage estimation. If you mis-estimate a deer to be 25 yards away, and it is actually 30 yards away, even the fast arrow lands a little lower than expected, but it “misses” its mark by a smaller margin than the slower arrow. Since a heavier arrow would nosedive more quickly, a five yard mis-estimation would result in a more dramatic miss. So whether you’re a hunter or competition 3D shooter, you may find that faster arrows actually add a little error-buffering into your yardage estimation. Of course, if you always shoot a known distance, there would be no advantage – but that’s not bowhunting.

DUCKING THE ARROW

Hunters may also find that a faster arrow gives game animals less opportunity move out of position. When you fire an arrow at a game animal, the sound of the bow travels much faster (about 1100 fps) than the arrow. So the game animal will certainly hear the sound of the bow before the arrow arrives. During that time, the animal has a brief opportunity to lunge, jump, squat, or otherwise get out of the way. For example, an alarmed deer will often “crouch” in preparation to jump. This crouching motion makes it appear the deer has attempted to “duck” the arrow, when in fact the deer is just loading its muscles to jump and flee. As a result, many bowhunters tend to miss high, shooting the arrow over the deer’s back or impacting above the kill-zone. Of course, there are several factors that come into play (the alertness and athleticism of the deer, your distance and angle from the target, the amount of noise from your bow, etc.) which can affect how quickly a deer responds to the sound of your shot. But one thing is for sure. The faster your arrow arrives at the target, the less time the deer will have to react. So in that respect, faster is indeed better.

MORE SPEED USUALLY MEANS MORE NOISE

We hate to be party poopers, but blazing arrow speeds come with some undesirable side effects – like increased noise. It’s to be expected, as faster moving things make a bigger disturbance in the surrounding air, but that’s not all. Bows transfer less energy into lightweight arrows than they do into heavyweight arrows, and that means a little more energy is available to create unwanted noise. If you doubt the idea, just pick-up a 1,000 grain fiberglass bowfishing arrow and fire it through your compound bow. Your bow will hardly make a whisper. Now, this isn’t to say +/-50 grains is going to make a dramatic difference. The noticeable effect will vary bow to bow, and if you shoot a high-quality modern bow that’s already pretty quiet, the difference will probably be minor. On the other hand, if your bow is already noisy, even when shooting your heavyweight aluminum arrows, shooting ultra-light carbon arrows will guarantee you a virtual harmonic train-wreck.

TAMING THE BEAST

As with any bow, noise output depends on several things – some of which you can control. If you’re diligent about maintaining your fastener torques, and your bow has a handsome compliment of string silencers/stops, dampeners and a good high quality stabilizer, noise output might not be an issue. Nevertheless, noise is an important consideration for bowhunters, and you’ll have to weigh the advantages of flatter trajectory against some increased noise. For what it’s worth, most modern equipment bowhunters tend not to choose the very lightest shafts. Bowhunters tend to prefer mid-weighted shafts (Easton Bloodline, Gold Tip Hunter, Beman ICS Hunter, CX Predators, etc.) which yield moderate finished arrow weights. And while there is no single formula to fit every bowhunting application, our average custom arrow order (for men’s hunting bows anyway) yields a finished mass of around 400 grains. Now, if you’re not a hunter, bow noise is inconsequential. For competition 3D shooting, where noise and penetration really don’t make a difference, lighter arrows with flatter

trajectories are definitely better. But if you’re a bowhunter, it’s something to think about.Speed vs kinetic energy

OH BOY! THE KNOCK-DOWN POWER DEBATE

Here’s where the debate gets heated among enthusiasts. With all other variables constant, a bow will achieve a bit more knock-down power when shooting heavier arrows. So some bowhunting enthusiasts will dismiss the benefits of faster arrow speeds and flatter trajectories, and claim heavier (and more deeply penetrating) arrows are the most ethical choice. As ethical bowhunters ourselves, we can’t entirely disagree, but we have to keep this issue in perspective. Mathematically, there is an indisputable difference. The real question becomes, is it significant enough to make a difference in the field? Or is this debate just academic? To understand this issue, let’s look at the basic physics. How much penetration, or knock-down power, a projectile has in the shooting sports is generally expressed in ft-lbs of kinetic energy. Arrows which impact the target with more kinetic energy will penetrate the target more deeply than arrows with less kinetic energy. Kinetic energy is the energy of motion. Any object which has motion has kinetic energy. It’s not really so complicated to compute. Kinetic energy depends on just two variables: the mass of the object in motion and the speed of the object in motion. If we convert the data from our PSE Stinger-X test into ft-lbs of kinetic energy, we can confirm that the bow transfers energy more efficiently into heavier arrows. Fine. But are those extra ft-lbs a dealer-breaker? Do you really need to squeeze out every ft-lb you can get? Is the loss of arrow velocity worth the extra knock-down power? Those are questions you’ll have to answer for yourself. Here are a few things to consider while you mull it over.

CONSIDER YOUR TARGET

Before you make your decision in the speed vs. kinetic energy debate, you should consider your target – and the energy is takes to ethically harvest that animal with a bow. If you’re hunting smaller athletic animals, say pronghorn antelope, which are particularly alert and skittish, a faster arrow would surely be best. Hunting smaller game doesn’t require as much knock-down power, so getting the arrow to the target quickly will increase your chances of success. Other the other hand, if you’re pursuing a 600 lb. elk, you’ll be less concerned about the animal “jumping your string” and more concerned about getting optimal penetration. So if you hunt large heavy game, a heavier arrow may increase your chances of success. Like many issues in archery, the speed vs. KE debate is one that may never end! Every hunter seems to have his own opinions on the proper techniques, strategies, and ethics of big game bowhunting, and what applies to one hunter may not necessarily apply to another. But don’t make a mountain out of a molehill. If you have a hot-rod modern compound bow producing 70+ ft-lbs of KE, and you only hunt whitetail deer, the speed vs. KE debate is largely academic. No matter what arrow you shoot, you’ll have practically twice the energy required to harvest deer. In fact, at 70+ ft-lbs, you would have plenty of power for even the largest North American game species. But if your bow isn’t such a hot-rod, or if you shoot low poundage and/or a short draw length, the KE issue may be a hair worth splitting. According to Easton’s field chart, the amount of KE you’ll need varies by the species you intend to hunt. Obviously, the larger the game, the more KE you’ll need. And regardless of the power of your bow, you’ll still need to land your shots in the boilermaker. If you hit an animal in the shoulder, all bets are off. But assuming you do your part, Easton’s recommendations gives us a place to start. Of course, these recommendations aren’t absolutes, nor are they guarantees of success.KINETIC ENERGY RECOMMENDATION15-25 ft-lbs | Small Game (rabbit, groundhog, etc.)
25-41 ft-lbs | Medium Game (deer, antelope, etc.)
42-65 ft-lbs | Large Game (elk, black bear, wild boar, etc.)
65-80 ft-lbs | Toughest Game (cape buffalo, grizzly, moose, etc.)To give this some perspective, refer back to our PSE Stinger-X test. Would our bow be capable of harvesting a Whitetail Deer? According to the chart, yes, easily. A properly placed arrow impacting with 70+ ft-lbs of KE is likely to generate a clean pass-thru on a deer, with plenty of energy to spare. So the advantage of the extra knock-down power could be considered overkill. But as many of we bowhunters know, things don’t always go as planned. Sometimes a little extra power might come in handy. Again, this is a personal choice. If you think those extra ft-lbs might make the critical difference, go with a little more shaft weight.The nerdy physics stuff

HOW IS KINETIC ENERGY COMPUTED?

Kinetic energy of an arrow can be found by using the formula KE = (mv ²)/450,240 where m is the mass of the arrow in grains and v is the velocity of the arrow in fps. If you remember your basic physics formulas, the KE equation is normally mv ²/2, but the archer’s KE formula contains a special conversion (/450,240) which just sorts out all the units and converts v and m, in fps & grains respectively, to output a solution in standard ft-lbs. All have you to do is square the velocity, multiply by the arrow mass, and divide it all by 450,240. Easy! Here’s an example. Let say your bow setup shoots a 400 grain arrow at a respectable 250 fps, the computation of your kinetic energy or “knock down power” will be:KE = (mv ²)/450,240
KE = [(400)(250²)]/450,240
KE = [(400)(62,500)]/450,240
KE = 25,000,000/450,240
KE = 55.53 ft-lbs

WHAT ABOUT MOMENTUM?

In the shooting sports, kinetic energy is the accepted standard for describing the energy, or power, a projectile can deliver at the target. There’s practically no discussion within the shooting sports industry to question whether or not kinetic energy is the most inappropriate mathematical model. Nevertheless, we feel obligated to mention momentum here before moving on. Kinetic energy and momentum aren’t the same thing. Some years ago, we received a letter from a gentleman who emphatically insisted that kinetic energy was NOT the best mathematical predictor of hunting penetration with a bow and arrow. He claimed the industry standard expression of kinetic energy was “short-sighted” since the benefit of speed is exaggerated by squaring velocity in the equation (we didn’t make up the equation BTW) and that the KE model applies better to high-speed projectiles like bullets. He explained (at some considerable length) that momentum was clearly the better model for archery. With over 16 years in the archery industry, we have yet to see an archery product rated in kilogram meters per second. But in the interest of leaving no stone unturned …

MOMENTUM VS KINETIC ENERGY

We dug around – and he was right. There are a few sporting enthusiasts who apparently dispute the convention that KE is the best measurement for predicting hunting penetration with a bow and arrow. There just aren’t many of them. The momentum argument goes like this …--> Kinetic Energy = Mass x Velocity x Velocity / 2
--> Momentum = Mass x VelocitySince velocity isn’t squared in the momentum formula, arrow mass and velocity play more equivalent roles – momentum increases directly as velocity increases. In the kinetic energy model, energy increases as the square of the velocity. So if you recomputed our chart to show momentum, the energy differential (between the light and heavy arrows) would be much more significant. The heavier arrows would show a major increase in overall momentum (23% more instead of 6% more using our PSE Stinger-X example), and you could therefore conclude that heavier arrows would indeed yield dramatically better hunting penetration. Sounds logical, doesn’t it? In fact, the application of this mathematical model would be a poke in the eye for speed freaks everywhere. It would be hard to argue that lighter arrows are better if they really resulted in 23% less penetration at the target. That would be a pretty major sacrifice. We bounced this idea off a few of our engineering friends inside the industry. They mostly just chuckled at the supposition. Eh!

IS THERE A PHYSICIST IN THE HOUSE?

Right or wrong, the shooting sports have a number of traditions and conventions regarding technical measurement. And the potential lethality of a projectile (whether from a firearm or bow) is traditionally expressed as a function of KE (ft-lbs). As such, most sporting enthusiasts have some comprehension of ft-lbs. Unfortunately, a momentum rating in kg m/s or lb ft/s would surely leave many of us scratching our heads. Given the dramatic difference in the two methodologies, it seems unlikely that KE has remained the standard of the shooting sport’s for so long – especially if the model is so entirely incorrect. There are a lot of talented engineers and technical professionals in the archery and firearms industries. So either they have ALL somehow missed it, or the momentum model doesn’t necessarily apply. Is there a physicist in the house?