Bulletproof Bow Tuning
October 28, 2010
Properly tuning your bow could spell the difference between shooting your next big buck and shooting at it.
Bow tuning is about as real as Snow White is to most archers. They think that it is either a fantasy to tune their own bow, or they hope the fairy tale will come true and Prince Charming will ride up and do it for them. What they usually end up with is someone from the Flintstones whose knowledge dates back to the Stone Age, and they are worse off than when they started: Their bow still isn't tuned, and they are more confused than ever.
Here are 12 simple steps to bulletproof bow tuning that any archer can do themselves with a few simple tools.
I should first note that you should not attempt to tune a new bow straight out of the box. The strings and cables will stretch as you start shooting, and any tuning that you do will be out the window 10 to 15 arrows later. The same is true of a bow that has just had a new string or cable put on. Shoot the bow, break it in and, most important, make sure that you are familiar with the bow and how it feels from the beginning of the draw all the way through the recoil after the shot before you try to do any serious tuning.
SELECTING THE RIGHT EQUIPMENT
Most bowhunters these days are shooting mechanical releases that not only provide greater accuracy but also give the archer more leeway when selecting an arrow. Easton's arrow charts, or the ones provided by other manufactures, are good resources for selecting an arrow, but they are by no means accurate in every case. For example, most arrow charts only take into account the arrow length and the bow's draw weight, draw length and point weight. Some cams are more efficient than others and will transfer more energy to the arrow, changing the spine. The material and number of strands your bow's string and cables are made out of will also greatly affect the bow's performance, which is a direct correlation to the bow's affect on the spine of your arrow.
Immediately after having a proshop time the cam(s) or before shooting a new bow, dab a drop of white out on both side of the cam under the limb and draw a line parallel to the limb. In the future you will have a visual indication of whether or not the cam is in time.
All of this sounds rather daunting, but it is not. There is a light at the end of the tunnel, especially for archers shooting a mechanical release. High-speed video has shown that when shooting a mechanical release, there is very little bend on the arrow (spine) when compared to a comparable setup shot with fingers. This gives the release shooter the advantage of shooting virtually any arrow. An arrow that is a couple of sizes under- or overspined should tune without a problem, but keep this in mind if you are having difficulty getting the bow to tune later on; you may eventually have to change arrows.
Begin the setup process with the tiller. The tiller is normally measured from the point where the limb meets the riser out to the string. Recently, most companies have been recommending stretching a piece of string between the axles and using this line for your tiller measurement. Especially on one-cam bows, this method will prove to be much more reliable. The actual distance of the tiller is not important. What is important is that the measurement on the top limb equals the measurement of the bottom limb. If it does not, the tiller can be adjusted by tightening or loosening one limb bolt or the other until both tillers match exactly.
Before you begin tuning, make sure that you have the correct arrow rest for the style you shoot. When shooting a mechanical release, the force on the arrow bends vertically, requiring a rest that has a vertical spring tension. Popular examples would be any of Golden Key Futura's TM Rests, Bodoodle rests or a host of variations on the lizard-tongue design. Another popular rest style that works well for bowhunters shooting mechanical releases is the new drop-away design. Finger shooters, on the other hand, will exert a side-to-side force on the arrow and need some sort of cushion plunger or Berger button to counter the horizontal force applied to the arrow as the fingers release the string.
Most bows have some adjustment for draw length. If you plan on using a release, make sure you check your draw with the release you plan to shoot. Note: Never draw a bow back using a mechanical release without an arrow on the string. Also, be sure your arrow is pointed in a safe direction when checking draw length. Finger shooters often draw the bow to the corner of the mouth. This allows a solid anchor and leaves enough back tension for a good shot. This is also my preference for release shooters. The string should come back even with the corner of the mouth to about 1⁄2 inch past that point for those who anchor below the chin. Ensure that you have a comfortable draw length before going on with the tuning process. If you have to change the draw length later, you will have to start the entire tuning process again.
The top tear shows where the arrow went through the paper, nock lef, i.e. the nock end of the arrow went though the paper to the left of where the point entered. The bottom hole was after the arrow rest was adjusted showing an ideal paper tear.
If your bow is new and hasn't had any arrows shot through it yet, take some white correction fluid and mark the cam. Otherwise, retime the cam or get your local proshop to time it before you start any serious tuning. Paint a patch on the cam under the limbs. When the correction fluid dries, draw a line parallel to the limb on each side. Now you will have a visual marker to instantly check your cam or cams to see if they are still timed. Likewise, when re-timing the cam(s) you will go back to the same starting point.
Next you will need to set up your arrow rest and nocking point. Adjust the arrow rest so that the center of the arrow's shaft goes through the center to upper 1⁄3 portion of the hole where the rest attaches to the bow. Then crimp the nocking point on the string or tie the string loop as appropriate. With the arrow nocked, sight down the back of the arrow and ensure that you can see between the fletching and the arrow rest. If you cannot, you will have a clearance problem that will make it impossible to get a solid tune later. Check the orientation between the arrow fletching and the rest. If it does not look as though it will clear, adjust your nock appropriately.
The exact placement of the center shot (the left right alignment when the nocked arrow sits on the rest) will vary slightly from one bow to the next depending on the
design of the cams, limbs and riser, but it is easy to find. When possible, read the bow's manual for advice on where the center shot should be. The center shot on most, if not all, bows should be between center and 3⁄16 inch to the left of center for a right-handed bow. To find the center shot, first paint a small strip of the limb with correction fluid or a piece of masking tape just above where the limb meets the riser. Measure the limb and place a small vertical mark at the center of the limb. Make another mark 3/16 inch to the left of center (for right-handed shooters). Next, do the same for the opposite limb. With the arrow on your arrow rest, line up your bowstring along the marks (either center or 3/16 inch off, according to your bow's manual). When the string is aligned with the marks, it should also bisect the center of the arrow shaft. If it does not, adjust your arrow rest accordingly.
Proper setup on a peep sight is one of the easiest and most overlooked aspects of bow tuning. Using a string separator or bow press, install the peep into the string, but do not tie it into place. Then, with an arrow on the string and pointed safely downrange, draw the bow and come to a comfortable anchor with your eyes closed. When you open your eyes you should be able to see through the peep without moving your anchor or the bow. If you cannot, let down, adjust the peep and redraw the bow with your eyes closed. When you can draw, anchor and see through your peep without changing your anchor, tie the peep solidly into place. I prefer to use dental floss to tie in the peep sight. It is lighter than serving material and is less likely to slip--two important advantages. Never shoot a bow without tying the peep into place. The oscillations of the string could propel a loose peep sight back into your eye. Safety glasses should always be worn when adjusting a peep sight.
TIME FOR TUNING
The first step to tuning is to make sure that the arrow is coming away from the bow cleanly. The easiest way to do this is a powder test. Take a can of foot powder and spray the back seven or eight inches of the arrow. Also spray the arrow rest and the shelf (the flat part of the bow under the arrow rest). Shoot an arrow into a solid target, and carefully remove it for inspection. Check the arrow rest and shelf. If any new marks have shown up in the powder, you are getting fletching contact and need to either rotate your nocks or change the spring tension on your arrow rest and repeat the test. Also check the arrow. Depending on the type of arrow rest, you will have one to three stripes where the arrow rode down the rest. Make sure that all of these lines do not come in contact with the vanes. If they do, you will have to rotate the nock on the back of the arrow.
Paper tuning gives a great visual indication of what the arrow is doing when it leaves the bow. Standing about six feet from a piece of paper, you shoot an arrow through the paper and read the resulting tear. It is similar to taking a photo of the arrow as it is leaving the bow. First make sure you are using a straight arrow. I cannot begin to tell you the number of hours I wasted trying to tune a slightly crooked arrow. If you fail to remember this step, be sure to wear a hat to keep yourself from pulling all of your hair out.
To set the tiller, stretch a piece of string between the axles and measure from the point where the limb meets the riser to the string. The actual number does not matter, but both the top and bottom measurements should be equal at the beginning of the tuning process. The tiller may be offset later during the tiller tuning process.
From about six feet away, shoot the arrow through the paper. Ideally you will have a single hole measuring the diameter of the arrow with three small tears where the vanes went through. Shoot the same arrow two or three times and look for the consistency in your tears. Just because you get the results you want once does not mean you can ignore the rest of the tears. If the tear is vertical, or at an angle, adjust the nock height first. If the point of the arrow appears to have gone through the arrow lower than the nock end, lower the nock or slightly raise the arrow rest. The good news about paper tuning is if you go the wrong way, you will see the tear getting worse. If this happens, simply adjust in the other direction.
Once you have a tear that is completely horizontal, you will need to adjust the arrow rest in and out. Whereas when the tear matchs the direction the arrow needs to be moved on a vertical tear, it is the opposite on a horizontal tear. For example, if the tear shows the nock end to the right of point, move the arrow rest (point) farther to the left. Again, you do not have to remember all of this from the top of your head. If you get a bad tear, move the rest 1/8 inch in either direction. If the tear improves, you are going the right way; if it gets worse, move it in the opposite direction.
When you start tearing bullet holes, or close to them, less than 1/2 inch from about six feet, step back a couple of feet and try it again. As the arrow oscillates or porpoises through the paper, it is possible to tune to a harmonic where it is straight as it travels through the paper giving a false reading. With an indication of a clean tear at two different distances, you are assured that the arrow is traveling out of the bow straight and true.
For most archers the only thing left to do after paper tuning is to set the sights. For those who truly want the most accurate and forgiving setup, you need to also group tune. While I highly recommend paper tuning and feel that it is a critical part of the tuning process, the only thing it guarantees is that the bow is extremely accurate from six feet. (Unfortunately, all of the bucks I have taken have been from distances far greater than six feet.)
After paper tuning, shoot and set your sight pins. Then shoot a group at your maximum-accurate, distance, noting any arrows that were simply bad shots on your part. Next, shoot another group but remove 1/4 turn from your top limb. Check to see if the group gets better or worse. Repeat this test in 1/4-turn increments until you reach one full turn. Then return the top limb to zero and repeat the test for the bottom limb in 1/4-turn increments. Using a different target, such as paper plates, each time you adjust the tiller should leave you with a visual record of the bow's groups with different tiller settings. Set the tiller to the measurement that grouped the best overall, and adjust your sight pins to this new setting.
|BULLETPROOF BOW TUNING|
- Pick the proper arrow.
- Select the proper rest for your style of shooting.
- Adjust the bow for an even tiller.
- Adjust the draw length.
- Time the cam(s) and mark them for future reference.
- Adjust the nock height.
- Adjust the center shot of the arrow rest.
- Set the peep sight for the proper height.
- Perform a powder test for vane clearance.
- Paper tune the bow from two different distances.
- Group tune the arrows by adjusting the tiller.
- Record all measurements for future reference.
RECORD THE DATA
The last step is to record everything. Measure your draw length, arrow length, brace height, nock height and tiller, record the results and keep them in your bow case. Then make sure to mark your sight, arrow rest, cams, cable guard, everything you can think of is marked with correction fluid so you can instantly see if anything has changed or moved. Also, by recording all of your bow's data once you know you have a solid setup, you will have an excellent starting point the next time you have to make changes and retune the bow.
Your bow is a tool like anything else; you will get out of it what you put in to it. To properly tune a bow it will take at least a day--probably more--but I can guarantee you will see a difference in your groups. It does not matter how good the driver is; if his car is not setup and tuned properly on Saturday, he won't be in victory lane on Sunday. The same is true for your bow. Put in the time to tune it properly, and reap the benefits when that big buck walks out in front of your stand next fall.