As bow velocity reaches its limit, hunters must decide if they'll continue… CHASING SPEED
By Frank Miniter
When Holless Wilbur Allen cut the limbs off a recurve and added wheels and cables to create the first compound bow in the 1960s, he launched an arms race to build the fastest hunting bow possible.
First, we should note that this need for speed is your fault. Okay, maybe not you specifically, but it is what the majority of hunters have always clamored for. At some point in the evolution of the automobile, the consumer’s first question about a car went from “How fast does that sucker go?” to the more sensible “How does it handle?” Bowhunters have yet to fully make this turn toward sanity. As a hunter hefts a new compound bow, he still reflexively asks the guy behind the counter at the bow shop, “How fast is this thing?” This, of course, is the cue to the savvy retailer to exclaim, “No deer is going to jump the string of that bow!”
Of course, many of the bows now considered “pure shooters” would have been labeled “speed bows” just a decade ago, when an honest 300 fps was considered fast. New materials and a lot of smart engineering have allowed bows to evolve a tremendous amount in just a few years. And this year, BowTech and PSE introduced compounds they claim will fire arrows at 360 and 370 fps, respectively. Bow design has come so far so fast, in fact, that many people in the industry are now pointing out that, given the available technology, we are reaching the limits the laws of physics place on cams and cables pulled by a human arm.
Before we dive into the future of the bow, we should note that while engineers have found some remarkable ways to make bows shoot faster, the way we arrive at a bow’s speed has also changed. Roughly 10 or 12 years ago, the accepted calculation used to test bow speeds shifted from AMO (Archery Manufacturing Organization) to IBO (International Bowhunting Organization) standards. Both AMO and IBO require a bow to be set at a 30-inch draw length, but they differ on two major criteria. The AMO standard requires a bow to be set at a 60-pound maximum draw weight and that the bow shoots a 540-grain arrow (9 grains per pound). The IBO standard, in contrast, sets a bow’s max draw weight at 70 pounds shooting a 350-grain arrow (5 grains per pound).
The IBO standard quickly gained acceptance, mainly because consumers simply didn’t understand the difference between the two rating systems. If you started talking about all the kinetic energy a high AMO rating portends, all but the most informed would shake their head and beg you to keep it simple. Consumers assume that when manufacturers give a complex answer, they’re usually seeking to deceive. The IBO standard translated to higher speeds, so most bowhunters were more impressed with that rating and marketers responded. (We should also note that while the 30/70/350 standard to measure bow speed is widely known as “IBO speed,” these are the recommended standards of the Archery Trade Association.)
We're hitting a wall. Without another big technological breakthrough, we can’t make bows much faster without compromising how comfortable they are to shoot.
Now, perhaps you bought a new compound with a listed IBO speed of 338 fps, but when you used it to shoot arrows through a chronograph, it clocked only 319 fps. The first culprit could be your draw length—remember that the IBO standard is 30 inches. As a rule of thumb, for every inch you shorten a bow’s draw length, you lose about 10 fps. A draw weight set under 70 pounds and an arrow weight of more than 350 grains will also slow down your bow.
And don’t bother looking online for videos of bow manufacturers speed testing their bows to verify their claims. This isn’t to say they’re just making up the speeds they list—there are too many savvy bow gurus out there for any company to get away with that. But they use perfectly tuned bows, arrows without fletching, fall-away rests, and other “tricks” to coax every bit of speed they can out of their bows’ cams, cables, and limbs. Basically, the ratings that manufacturers print are achieved under perfect-world conditions. (Case in point: None of the speeds in the "Speed Trend" chart above were as fast as the manufacturers' ratings for their bows.)
Is 400 Possible?
Yet the question remains: Can a compound bow shooting at the current IBO standards push an arrow to 400 fps? Mathematically, we’re told, the answer is yes. We’ll leave out most of the complicated math tossed at us by egghead engineers, but the bottom line is that while IBO standards place a limit on the maximum amount of energy a fully drawn compound bow can store and potentially release into an arrow, it’s theoretically possible for a 70-pound bow set at a 30-inch draw length to propel a 350-grain arrow at 400 fps. We’ll illustrate how, but first we should say that without some new technological breakthroughs (which, mind you, engineers tell us are not outside the realm of possibility), you wouldn’t want to shoot such a beast—especially in a hunting situation.
Unless you’re one of those guys who names his biceps, you must first acknowledge that the compound bow isn’t powered by an engine, but instead is a hand-drawn machine—and at some point, the output from any hand-drawn device will max out. When this happens, the speed race will slow to fractions of feet per second gained not by more aggressive cams, shorter brace heights (meaning longer power strokes), and such, but rather through things like reduced friction within cam cycles and slicker cable slides. “We are close to max efficiency right now. We’re hitting a wall,” says Blake Shelby, vice president of sales and marketing at PSE. “Without another big technological breakthrough, we can’t make bows much faster at IBO standards without compromising how comfortable they are to shoot.”
To generate enough speed via IBO standards to bust the 400 fps barrier, a manufacturer would need to optimize the power stroke to the point where just about every pound of stored energy is transferred from the bow to the arrow. (To determine the power stroke of a bow, you subtract the brace height—or the perpendicular distance from the bowstring to the pivot point of the handle at rest—from the true draw length.) ATA standards subtract another 1¾ inch for the grip. So if you’re shooting a bow with a 30-inch draw length and a brace height of 5 ¼ inches (like PSE’s new Full Throttle), the power stroke of the bow is 30 minus 5¼ minus 1¾, or 23 inches.
A longer power stroke means that the peak draw weight must be held over a longer distance as the bow is drawn. This results in more stored energy in the limbs that is then transferred to the arrow when the string is released. If a compound bow is set at 70 pounds of draw weight and the cams are set to start at 70 pounds and maintain that 70 pounds all the way through the power stroke with no let-off (ouch!), there could—theoretically—be enough stored energy in the limbs to spit an arrow out at 400 fps. But the bow would have to be lubed and tuned perfectly for it to operate at near perfect efficiency. It couldn’t lose any energy to vibration, noise, or friction; all the energy would need to be transferred to the arrow. Forget having a comfortable valley at the end of the draw stroke—the bow would be fighting to get loose like a wild colt from beginning to end. On top of that, you’d need a minuscule brace height, perhaps even shorter than the Full Throttle’s 5 ¼ inches. Talk about daunting.
As bow speeds plateau for the time being, bow makers are spending more research-and-development dollars in an attempt to appease hunters looking for more than just the next super-fast compound. Elite Archery’s new Energy is a good example of a bow made for the masses, with a forgiving 7-inch brace height and a plenty-fast IBO speed of 335 fps. There are countless quality bows from almost every bow manufacturer that fall in the 310 to 340 fps range. They differentiate themselves by things like enhanced ergonomics, lighter weight, improved vibration dampening, and better cams.
In fact, just about every cam on the market has a draw stroke that is optimized on computer-aided design software, such as SolidWorks. Some cams are optimized for speed, some for comfort, but most are optimized with a combination of the two. CAD software can show engineers the stress points within a cam, and even cycle and shoot a bow virtually on a computer screen.
In 2011, Hoyt revolutionized the light-bow category with its Carbon Element, a bow that weighs a mere 3.6 pounds naked and which utilized the newest technology available at the time to attain greater strength than traditional risers. There are more than 40 different carbon components in each Hoyt carbon riser, fully integrated and co-cured to create a single immensely strong but lightweight structure.
After Hoyt introduced the Carbon Element, many of its competitors were quick to invest in carbon technology in order to be a part of the light-bow segment. BowTech’s Carbon Overdrive and Carbon Knight, for example, weigh in at 3.3 and 3.2 pounds, respectively, stripped down. Hoyt has continued to add to its line, and this year introduced the Carbon Spyder, a 30-inch axle-to-axle bow with a 6 ¾-inch brace height that shoots 332 fps. The Spyder, like its predecessor the Element, weighs 3.6 pounds naked.
“The technology that we use to build carbon risers is an extremely high-tech, advanced, proprietary technology,” says Randy Walk, president of Hoyt. “After a tremendous amount of research and development, including 18-plus years of working on carbon bow prototypes, we discovered this technology to be second to none. It allowed us to bring a carbon bow design to the market that we believed in with 100 percent confidence. It was a marathon, but as with the other R&D marathons we run, it was certainly worth running and the outcome was so rewarding.”
A lot of bow manufacturers could similarly, and justifiably, boast about their technology, quality, and push to be the best. The bow business is small compared to other sports industries, but it’s loaded with passionate people who are quick to disparage innovations that aren’t flawless. And while the industry is small, its sports are growing by leaps and bounds.
- Old-School Compounds
- Old-School Compounds
- Old-School Compounds
In 2010, U.S. bowhunting license sales hit an all-time high of 3.64 million. A nationwide survey by the ATA found that 18.9 million Americans participated in archery and/or bowhunting in 2012. With an eye to the future, many bow manufacturers have wisely invested in the popular National Archery in the Schools Program.
“The person selling the most bows right now is Katniss Everdeen [the heroine of the Hunger Games books and movies],” says PSE’s Shelby. “Thanks to Katniss, we can’t make enough traditional bows right now.”
If the bow industry can help some of these newcomers transition to competition archery and bowhunting, a legion of new archers will head to the ranges and forests in the coming years. And with an increase in demand for newer and better bows, the next generation of bow enthusiasts could push bow makers toward design innovations that will make the quest for the elusive 400 fps compound bow seem quaint.
Illustrations by Robert Prince
Photos by John Hafner, Archeryhistory.com
Bow Test 2014
Every year the Outdoor Life team puts the newest compounds through the most stringent test in the industry. See which bows took home top honors.
Train to Hit
The traits that separate elite bowhunters from the masses are attention to detail and rigorous training. Here’s how they push themselves to the next level.
Hunt Barnyard Bucks
Bucks that live to see four years of age have a handful of secret hideaways, and chances are there’s a barnyard among them. Here's your game plan.