For every action there’s a reaction. Physics (the science of mechanics) and archery have a lot in common. When tuning a hunting bow, every adjustment made to the bow causes the arrow to react accordingly.
The goal of bow tuning is to achieve smooth, quiet, and accurate arrow flight. Easier said than done, bow tuning is an art in itself every hunter who carries a stick and string must embrace.
Despite those who are forever looking for the easy way out, there are no shortcuts to bow tuning. Bows also have a tendency to go out of tune gradually, making it difficult to notice lost performance and accuracy.
Those who shoot frequently at leagues, IBO shoots, or backyard ranges will find their bows need adjustment regularly to maintain the delicate balance required for consistent accuracy. High-speed compound bows with aggressive cams and overdraws, and/or high letoff bows must be tuned more frequently than those bows with round wheels or energy wheels.
With these realities in mind, bow tuning should be considered an ongoing process or necessary evil as the case may be.
As they say, timing is everything. The timing of a bow refers to how the wheels or cams break or roll over when the bow is drawn. Ideally the wheels or cams should break simultaneously.
When a bow goes out of time, the wheels or cams lose this delicate balance. If a bow is seriously out of time the arrow will exit the bow with a dramatic tail-high orientation. Arrow flight is distorted and it becomes nearly impossible to maintain consistent shooting accuracy.
It takes the trained eye of a bow technician to determine if a bow is out of time and make the necessary adjustments. The timing is checked at full draw. A bow vise is used to take the pressure off the cables so they may be adjusted.
Normally one cable must be shortened slightly to correct the problem. This type of work is best handled in an archery pro shop by technicians who deal with timing problems regularly.
“Cable stretch is the main reason compound bows go out of tune,” says Professional Archery Technician, Kim Fortelka. “The more times a bow is shot the faster cable stretch occurs.”
Not surprisingly high-speed bows that feature cams tend to go out of time much quicker than bows equipped with wheels or energy wheels. Cams put considerably more strain on the cables, bow string, and limbs.
“Single cam bows like the Mathews Solo Cam are the least likely to go out of time,” adds Fortelka. “Because these bows operate using a single continuous cable, timing isn’t a problem.”
As with all bows, single cam models experience cable stretch with age and use. When the cable in a single-cam bow stretches there’s a loss of speed and performance, but the bow doesn’t go out of time. Other manufactures including Jennings and PSE have introduced single- cam bows and more are sure to follow.
The arrow rest has a profound impact on arrow flight. The rest must be adjusted so the shaft passes out of the bow without a sideways whip or the vanes making contact with the cable, rest, or bow riser.
“Arrow rests are adjustable for sideways movement much like the windage adjustment on an open-sight rifle,” explains Fortelka. “When adjusting an arrow rest strive to achieve a true center shot where the string, rest, and riser are in perfect line.”
Most hunters use a bow square to line up the rest with the string, then they shoot an arrow through a piece of paper stretched onto a frame. Depending on the tear the arrow makes as it passes through the paper, minute adjustments are usually needed to achieve a true center shot. Ideally the arrow should pass through the paper with a bullet-like hole.
The type of rest a hunter uses depends on his or her shooting style. Release shooters require a shoot-through style rest like the popular Bodoodle or TM Hunter. This style of rest allows maximum vane clearance when shooting high letoff bows or bows equipped with energy wheels or cams.
Tab shooters are better served with a cushion plunger type rest. The cushion plunger features an adjustable tension that helps compensate for the inconsistencies associated with finger shooting.
Nocks and Vanes
It may also be necessary to adjust the arrow nock to insure the vanes or feathers don’t make contact with the rest, cables, or riser. When attaching glue-on nocks, put a drop or two of Fletch Tite adhesive onto the arrow taper, slide the nock into position and spin the nock a couple times to spread the glue evenly. Then snap the arrow onto the string and turn the shaft until the vanes or feathers will pass out of the bow without touching the cable, rest, or riser.
“Adjustable nocks like Easton’s Super Nock come standard on the XX78 Super Slam shafts,” says Fortelka. “These adjustable nocks allow the hunter to index for vane clearance by simply rotating the nock in its special bushing. Adjustable nocks make arrow tuning a simple procedure.”
The use of plastic vanes or feathers can also have an influence on bow tuning. Plastic vanes are more durable, but feathers are more forgiving and deliver better arrow flight when a release isn’t as crisp as it could have been.
Release shooters who shoot high-speed bows will find plastic vanes the ideal choice. The five-inch Bohning Low Profile vanes are an excellent match for high-speed bows.
Those who shoot with their fingers are wise to select turkey feather fletchings. The natural texture of turkey feathers helps to grab the air and quickly stabilize an arrow.
“Using too stiff or too light an arrow spine is one of the leading causes of bow tuning problems,” explains Fortelka. “The spine or stiffness of an arrow makes a big difference how the shaft flies.”
The more poundage a bow generates the stiffer the arrow spine required to achieve accurate flight. Aluminum arrow spine is indicated by two numbers that appear on the shaft. The first two numbers represent the outside shaft diameter in 64ths of an inch. The second two numbers indicate wall thickness in thousands of an inch.
A 2117 shaft is 21/64 of an inch in diameter and features a .017-inch wall thickness. Carbon and carbon/aluminum arrows are normally rated for a specific bow poundage rather than being rated by diameter and thickness.
The archery hunter’s task is to choose the lightest possible arrow spine that has adequate stiffness to ensure accurate arrow flight. If too heavy or stiff an arrow is selected the hunter will sacrifice valuable speed. If too light an arrow is chosen, the shaft will flex dramatically when shot and lead to erratic arrow flight. Hunters who shoot too light an arrow also face potential damage to bow limbs and risers.
Easton, the world’s largest producer of aluminum arrows, publishes a free chart that helps hunters select the proper arrow spine for all compound bows. The chart takes into consideration the type of shaft, shaft length, broadhead weight, peak bow poundage, and whether the bow is equipped with round wheels, energy wheels, or speed cams.
A conservative guide, the Easton Shaft Selection Chart is a good reference point to begin from when selecting hunting arrows. As a rule of thumb, those hunters who use a mechanical release can normally shoot one or two spine sizes below the Easton recommendations with good success; tab shooters are wise to select a arrow spine that closely matches the recommendations in the Easton chart.
Graphite or carbon arrows are rated for peak bow weight. Those who shoot carbon arrows are wise to follow the manufacturers suggestions when selecting an arrow of the proper stiffness.
Graphite arrows tend to be a little stiffer than aluminum and because of their smaller diameter these shafts enjoy a bit more speed and slightly better penetration than aluminum arrows. Carbon arrows are also a little more durable than aluminum shafts.
Those who choose graphite arrows must match them up with an arrow rest made specifically for the thin diameter of carbon shafts. Graphite arrow users must also keep in mind that these shafts require special nocks and inserts, made specifically for carbon arrows.
Most compound bows come with a monofilament serving or wrap over the bow string. This serving provides a place to attach string nocks without damaging the bow string.
“Monofilament servings are fine for shooters who shoot with their fingers but they quickly wear through when subjected to a mechanical release aid,” Fortelka says. “Release shooters should serve their string with a fast flight braided material. This durable serving material holds up well to the abuse of mechanical release aids. Adding a fast flight serving also keeps string nocks from moving once they are squeezed down tightly.”
Release shooters should consider installing a cushion nock on the string that holds the arrow securely onto the string. Bows with a short axil-to-axil measurement require a cushion nock to prevent the arrow from popping off the string at full draw.
Fingers vs. Releases
Hunters who use a mechanical release aid enjoy more consistent shooting accuracy. A mechanical release allows for a smooth, crisp, and consistent arrow release shot after shot. Furthermore, when a release shooter makes a poor release, the shot is still likely to impact the target within a couple inches of the intended point of aim.
Finger shooters often suffer from the human element of hunting. A poor finger release generated by anxiety or excitement can send an arrow several inches off target and result in a clean miss or worse yet a crippling wound.
Those hunters who hunt with wheel bows can get good results shooting with fingers. Bows equipped with energy wheels or action cams are more difficult to shoot accurately and should be matched up with a release aid.
Hunters who choose bows that feature a let off of 70, 75, or 80 percent should also be using a release aid. High letoff bows put an enormous amount of torque on the bow string and limbs upon release. To insure accurate arrow flight the hunter must use a mechanical release that delivers smooth, crisp, and consistent results.
During the tuning process it will become necessary to shoot an arrow through a single sheet of paper taped or attached to a frame of sorts. The hole the arrow leaves helps to pinpoint bow tuning problems. When the bow is tuned properly a bulletlike hole will appear in the paper, indicating that the arrow point and fletching entered the same hole.
Paper tuning is an art in itself. Reading the tears takes a little practice and some guidance. Keep in mind that the following guidelines are for right-hand shooters only.
A downward tear in the paper indicates the nocking point is too low. Move the nock upwards on the string 1/16th of an inch at a time and try additional shots until the low vertical tear is eliminated.
An upwards tear indicates the nocking point may be too high. Lower the nock 1/16th of an inch at a time and make additional test shots. If the upwards tear persists there is likely a clearance problem. Clearance problems exist when the vanes or feathers contact the rest, cables, or riser.
If the tear goes to the right, chances are the arrow spine is too stiff or the arrow rest is adjusted too far to the right. Sometimes an archer who grips the bow tightly while shooting will torque the bow and cause a right-side tear.
If the tear goes to the left, most likely the arrow spine is too weak or the vanes made contact with the rest or riser.
A diagonal tear indicates more than one problem exists. First, adjust the vertical problem by adjusting the nock and then correct for the horizontal tear.
Broadhead tuning is the final step in setting up a hunting bow. Fixed blade broadheads are not likely to impact a target in the same place as field tips. For this reason a bow must be sighted in to shoot broadheads.
The first step towards broadhead accuracy is to select arrows with vanes that feature a slight helical or twist. The twist in the vanes causes the arrow shaft to spin and stabilize in flight. If the vanes or feathers are straight the broadhead may steer the arrow and lead to poor accuracy.
Indexing the broadhead on the arrow shaft is an easy way to achieve consistent broadhead flight. To index a broadhead, screw the broadhead into the aluminum insert and take a couple test shots.
The broadhead may catch air and steer the arrow off target. Heat up the insert until the adhesive melts and turn the broadhead and insert 1/4 turn. Let the arrow cool a moment and make another test shot. Continue this process of indexing the broadhead and insert until the arrow flies true.
Getting consistent arrow flight from a fixed-blade broadhead can be a time consuming and frustrating experience. Two blade broadheads like the Patriot, Delta Rothhaar, Zwickey, and Bear Razorhead are likely to provide better arrow flight than fixed three- and four-blade heads.
Low profile heads like the NAO Razorbak are also easier to tune than broadheads that feature a large cutting diameter.
The new open-on-impact heads including the Rocket Mini-Blaster, Game Tracker Stiletto, Vortex, and Rocky Mountain Gator fly like field tips and open to a huge cutting diameter on impact. An excellent choice for hunters who use graphite arrows or high-speed bows that are difficult to tune with fixed-blade broadheads, open-on-impact heads operate using a simple lever principle that’s foolproof.
The cutting diameter of open-on-impact broadheads is much larger than fixed-blade broadheads. Some models cut a hole as large as 2 3/4 inches across! Not surprisingly it’s more difficult to punch an open-on-impact broadhead clean through a deer or other big-game animal. The extra blade-cutting surface increases friction and leads to slightly less penetration when cutting through tough hide, tissue, and bone.
Those hunters who use these new broadheads should shoot bows that feature at least 60 pounds of peak draw weight. The more weight the hunter shoots the more likely the open-on-impact head will pass through both sides of the animal. If the arrow doesn’t pass through the resulting blood trail may be spotty and difficult to follow.
Tuning a bow is a process that requires the hunter to take a close look at his or her arrows, arrow rests, vanes, nocks, the type of compound bow, and those ever-popular broadhead brands. Collectively these items must complement one another if the arrow is to fly like a bullet.