Compound Bow Technology|Paper Tuning Tips

Today's bow hunters and archery fanatics want their compound hunting bows to be smok'in fast, have smooth draw stroke, lightweight, compact, quiet, easy to tune, and forgiving. To get a compound hunting bow with a certain set of characteristics, you'll likely have to sacrifice some others. Ultimately, you will have to decide which characteristics are most important to you and choose the compound bow that best fits your needs. The technology with today's bow and arrows have significantly advanced over the past five years. It is hard to say that there are a lot of bad compound bows out there. They all have "kill" in them. It is important for you to take the time to shoot several different compound hunting bows to see which one fits you the best. The content below will help you learn more about the compound bow you are shooting or help you learn more about a compound bow you may purchase in the future.

What is difference between Solid vs Split Limbs?

Solid limb advocates claim that solid limbs offer better torsional stiffness and more accurate than split limbs. Split limb advocates claim that split limbs are more durable and produce less hand-shock than solid limbs. Over the past ten years limb type was used as a key selling feature for compound bows. Makers of split limb bows would tell you how much better split limbs were than solid limbs, while their competitors did the exact opposite. But over the years, many of those manufacturers have cross their

own lines in the sand, and changed some, or all, of their bows to split from solid, or to solid from split. In spite of the seasonal marketing hype, many bow manufacturers are willing to switch back and forth as situations warrant. For example, Bowtech had always exclusively used solid limbs. Although, in 2007 Bowtech introduced 2 new bows utilizing split limbs to accommodate a new riser design. The same flip is true for PSE and Mathews, traditionally solid-limb proponents, who have recently introduced split-limb bows in 2007 and 2009 respectively.

Where the rubber meets the road in the field, solid and split limb bows perform similarly. Whatever your preference, limb type should be a minor consideration compared to the other bow design characteristics we've discussed. Weigh this bow attribute lightly. Beyond the aesthetic appeal, it probably doesn't matter. The type of limb installed on any particular bow is probably the limb type that works best with that particular riser, limb pocket system, and cam system.

Understanding difference between Binary - Single - Twin - Hybrid Cams

In 2005 the Binary Cams were introduced by Bowtech Archery, the binary cam is a modified 3-groove twin-cam system that slaves the top and bottom cams to each other, rather than to the bow's limbs. Unlike single and hybrid systems, there is no split-harness on a binary system - there are just two "cam-to-cam" control cables. This creates a free-floating system, which allows the cams to automatically equalize any imbalances in the limb deflections or string and control cable lengths. In therory, this self-correcting cam system has no timing or synchronization issues and should achieve perfectly straight and level nock travel at all times.

Single Cams also known as a Solocam, the single cam system features a round idler wheel on the top of the bow and an elliptical shaped power-cam on the bottom. The single cam is generally quieter and easier to maintain than traditional twin cam systems, since there is no need for cam synchronization. One draw back of single cam systems is they do not offer straight and level nock travel, which can make some single-cam bows harder to tune. Some are very fast and aggressive, others are quite smooth. Many are easy to adjust and have convenient let-off choices, and others don't. But most single cams do offer reasonable accuracy and a good solid stop at full draw. Overall, the smoothness and reliability of the single cam is well respected. And the single cam is today's popular choice on compound bows.

A Twin Cam system is sometimes called a "Dual Cam". The twin cam system features two perfectly symmetrical round wheels or elliptical cams on each end of the bow. When these cams are synchronized, twin cam systems offer excellent nock travel, accuracy, and overall speed. Twin cams do require more maintenance and service to stay in tune. While the maintenance issues are a draw back of the Twin Cam, the only disadvantage to twin cams is the tendency for increased noise (compared to typical single and hybrid cams). Even with that said the twin cam is still the cam system of choice for many serious shooters.

Over that past several years the Hybrid Cam system has gained a lot popularity. The hybrid cam system features two asymmetrically elliptical cams: a control cam on the top, and a power cam on the bottom. This system is put together with a single split-harness, a control cable, and a main string. Hybrid cams claim to offer the benefits of straight and level nock travel, like a properly-tuned twin-cam bow, but without the timing and synchronization issues. One of the benefits of hybrid cams require less maintenance than traditional twin cams. They too need to be oriented (timed) properly for best overall efficiency and performance.

		When you pull the string of a compound bow, the limbs of the bow are squeezed inward. The energy you supplied to draw the bow is stored in the limbs, as potential energy, until you release the string. Upon release, the potential energy is transferred into the arrow as kinetic energy, as the limbs "spring" back into place returning the string to it's original position. Careful examination of this process of storing and releasing energy is what gives a compound bow its performance characteristics. There are only two factors that determine how much "power" your bow will have: 1) The amount of energy that can be stored in the limbs during the draw stroke. 2) The amount of that potential energy that can be successfully transferred into the arrow upon release (efficiency). So, how is one bow capable of a 320 fps IBO Speed, while another only shoots 280 or 305 fps? Well, it's all about energy storage. The key ingredients to arrow speed are draw weight, draw length, and arrow mass. The amount of energy a bow stores also depends upon the (geometry) of the cam or wheel design, the bow's let-off percentage, and the bow's brace height. The power stroke represents your effort. The power stroke begins as you pull the string back from the resting position and is completed when the bow reaches full draw. Each bow will have a different power stroke depending upon its settings and cam characteristics. Power strokes which are longer, higher, or wider will result in increased energy storage and arrow velocity.

		One of the major ways to increase the amount of stored energy during the power stroke is to shoot a compound bow with a higher maximum draw weight. All other things being equal, a 70 lb. bow will store more energy and shoot faster than a 60 lb. bow. The maximum draw weight of the bow is typically determined by the stiffness of the bow's limbs. Compound bows come in a variety of maximum draw weights, but the most common are the 50-60 lb. and 60-70 lb. versions. When you may purchase a bow with 70 lb. limbs, you can generally adjust the draw weight 1-10 lbs. down from the maximum weight. Keep in mind that a 70 lb. bow, turned down to 60 lbs., will not perform as well as the same bow in a 60 lb. version operating at it's maximum draw weight. Bows perform at their peak at or near their maximum draw weight.

		High poundage bows require heavier, stiffer archery arrow shafts. While they will generally generate more energy at the target, they may not necessarily generate much faster arrow speeds at IBO standards. Lower poundage compound bows can use lighter, more limber hunting or target arrow shafts. IBO standards allow 5 grains of arrow weight per pound of draw weight. Forexample; a 70 lb. bow can shoot an arrow (safely) as light as 350 grains. Now lets consider a compound bow set for 60 lb., should not shoot no less than 300 grains. When set for IBO minimum standards, many bows are only marginally faster in the 70 lb. version vs. the 60 lb. version. Since a 70 lb. bow must shoot the heavier arrow, the savings in arrow weight offsets the loss of energy storage during the powerstroke. A bow that is accurately set-up for best speed, a 60 lb. version of most bows will perform within 10 fps of the heavier 70 lb. version of that same bow.

		The longer your draw length, the longer your bow's power stroke will be - and the faster your compound bow will shoot. As a general rule, 1" of draw length is worth about 10 fps of arrow velocity. So if your particular bow has an IBO speed of 300 fps, and you intend to shoot the bow at 28" draw length - you should expect an approximate 20 fps loss in speed right off the top. Shooting a long draw length will most certainly deliver more speed. The trade off for shooting a bow with a long draw length is a considerable amount of control. In many cases it can be a bad trade-off. While you will have more speed with a long draw length you need to consider the fact that your accuracy could be compromised. In the field speed is important but confidence is the most important factor. If you are not consistently shooting well and are not 100% confident in your set up. It could mean the difference between harvesting that animal or going home frustrated.

		Brace height is an important factor in the energy storage equation. A bow's brace height is the distance from the string to the pivot point of the bow's grip. You can think of brace height as how close the string will be to your wrist when the bow is at rest. The closer the string is to your wrist, the more work you have to do to get the bow drawn back. If you're drawing a 6" brace height bow back to a 30" AMO draw length, you'll have to pull the string back a total distance of 22.25" before you reach full draw. But if the string rests farther back from your wrist to start, say the bow's brace height is 8", then you'll only have to pull the string back for 20.25". The bow's brace height also figures into how LONG the bow's powerstroke will be. As a matter of energy storage, a short brace height bow stores more energy and shoots faster than a tall brace height bow (all other things being equal). So brace height has the same affect on total powerstroke length as does the bow's draw length setting. The only difference is that the brace height determines where you start and the draw length determines where you stop. But unlike draw lengths, brace heights aren't adjustable. You can't change your bow's brace height later, should you change your mind. (A bow's AMO draw length is measured 1.75" beyond the grip pivot point. A bow's power stroke distance is found by subtracting the brace height and 1.75" from the AMO draw length.) Even though short brace height bows are faster bows they aren't automatically favored because a bow's brace height has a profound effect on the bow's forgiveness and shootability. Short brace height bows are generally less forgiving and require more skill to shoot accurately. Since the arrow is in contact with the string for a longer distance and period, there is more opportunity for any glitches in your shooting form (hand-torque, trigger punching, etc.) to have an effect on the arrow's flight. Longer brace heights have the opposite effect, limiting the effects of form glitches. If you shoot with absolutely perfect form and technique, a short brace height bow will be just as accurate as it's longer brace height cousins. Although, you have average skills and are prone to occasional goof-ups, a bow with a little longer brace height will yield better accuracy in most shooting situations. The average new compound bow has a brace height of approximately 7". Bows with shorter brace heights (5-6.5") will be faster but less forgiving to shoot. Bows with longer brace heights (7.5-9") will generally shoot slower but will be more forgiving to your errors. Many bow hunters tend to avoid short brace height bows (anything below 7 inches).

		Short Draw Length Archers and Brace Height If you are a short-draw archer (27" draw length or less), you have an advantage regarding forgiveness on your compound bow. A bow which has a 6" brace height and is set for long 30" draw length will have 22.25" power stroke. This means the during the shot, the arrow will remain in-contact with the string for approximately 23-24" (including string follow-through) until the arrow finally releases. This would generally make for a rather unforgiving setup. But that same bow in the hands of the short-draw archer will be considerably more forgiving to shoot. If a short-draw archer shoots the same bow at 26" draw length, their power stroke will only be 18.25" long. So the short-draw archer's arrow gets off the string in a shorter distance providing the short draw archer some "built-in" benefits of forgiveness.

		If you've ever shot a heavy recurve or longbow, you've certainly noticed that you're holding back the maximum draw weight just when you come to full draw, so you must aim and release the arrow quickly before your muscles weaken or begin to shake. The original compound bow was designed to eliminate this issue, by offering the shooter more time to aim and release the arrow. In contrast with the traditional bow, the draw weight of the compound bow decreases (sometimes dramatically) just as you come to full-draw. This is known as LET-OFF, which is controlled by the geometry of the cam system. Early compound bows featured a 35-50% let-off. Today's compound bows have let-off in excess of 75%. A bow with a 70 lb. draw weight and 80% let-off will require the shooter to hold back only 14 lbs. once the bow reaches full draw. Holding back such a small amount of weight, the shooter has the luxury to take more time aiming and releasing the arrow. A disadvantage to a high (over 75%) let-off cam is a small reduction in arrow velocity vs. a lower let-off cam system. All other things being equal, a bow with 65% let-off will shoot faster than a bow with 80% let-off. The difference in speed between a 65% let-off vs. 75% let-off is usually only a few fps. Fortunately, many cams use interchangeable modules which give you the option to easily switch between different available let-offs. Some cam systems even offer adjustable let-off right on the cam without the need for additional modules.

Nocking Point

Check your nocking point and rest to ensure they adjusted properly. Adjust the rest so the center of the arrow's shaft goes through the center to upper 1/3 of the hole where the rest attaches to the bow. Then crimp the nocking point on the string or tie your string loop but not too tight so you can't move it. Next use a level on the arrow to make sure that it is level with the sight window. Then check your center shot. The center shot on most compound bows should be between center and 3/16" to the left of center for a right handed compound bow. To find the center shot, take a piece of masking tape and place it just above where the limb meets the riser. Measure the limb and place a small mark at the center of the limb. Make another mark 3/16" inch to the left of center, and then do the same for the next limb. With the arrow on the rest, line up your string along the marks. When the string is aligned with the marks it should bisect the center of the arrow shaft if it does not adjust your rest accordingly.

Peep Sight

Peep sight is a simple fix but is often over looked. With the peep in the string but not tied into place. Nock an arrow and draw your bow 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 does not occur adjust until you can.

Fletching Clearance

One of the first steps is to make sure there is no contact of your fletching to either your rest or riser. A good way to do this is using the powder test. Spray the back six or seven inches of the arrow, and also spray the rest and the shelf. Shoot your arrow at a target and carefully remove it for inspection. Check the shelf and rest. If any new marks have shown up you are getting contact from the fletching. Depending on where the marks in the powder are depends on what you should do to correct this. If the marks are on the rest, or in contact with your fletching, rotate the nock to eliminate contact with your rest. If there is contact with the shelf, change the spring tension on your rest then repeat.

Paper tunning will work for all styles of shooting. The following is a guideline for clean arrow flight. There are a number of ways to set up your frame to do your paper tunning. One example, is to use several stakes with newspaper attached to the them. Another is cutting out a square in a cardboard box in the front and back. Then secure newspaper over the opening. Position the set up far enough away from your backstop so the arrow can completely clear the paper. Stand about ten feet from the paper and make sure your arrow is level as it flies through the paper. Fire a test shot and read the results. Compare the holes you have made in the paper to the diagrams below. Procedures for correcting the tear are listed next to each diagram. Please note that tuning procedures recommended for finger shooting often differ from those used for release shooting. You will find that the arrow spine reaction is different for fingers and release, therefore, the procedures for correcting the different disturbances vary. See the diagram below to make the appropriate adjustments.

Arrow Perfect Hole

This pattern shows clean arrow flight. The point and fletching
impacted the same location. Your bow is now ready to shoot or you may want to continue and try some of the super fine tuning methods.

Arrow High Tear (fletching tears above point)

Factors to consider:
-Move nocking point down
-Improper vane clearance
-See if arrow fletching is hitting the rest
-Wheels may be out of time.
-Check wheel timing
-Arrow may be too limber
-Adjust the launcher arm as necessary
-In this situation the Bow Weight, Arrow Spine, Arrow Length,Spring Tension should be fine

Arrow Low Tear (fletching tears below point)

Factors to consider:
-Raise the nocking point
-Wheels may be out of time
-Check wheel timing
-In this situation the Bow Weight, Arrow Spine, Arrow Length,Spring Tension should be fine

Arrow Right Tear (fletching tears to the right of point)

Factors to consider:
Note: If you are left handed follow these instructions in reverse.

FINGERS Shooters:
-Stiff arrow.
This problem is cured using the following methods:
a. Increase peak weight.
b. Use a heavier point.
c. Select a more limber arrow.
d. Lighten cushion plunger tension, or use a weaker spring on shoot around rests
e. Make small incremental rest adjustments towards the bow.

RELEASE Shooters:
-Arrow rest is too far to the right.
Move arrow rest to the left.

EITHER STYLE:
-Too much pressure on the cable guard
Rotate cable guard for minimum fletching clearance
-Irregular or inconsistent shooting form
See a qualified archery coach or professional and have them check your technique
-Clearance problem - See that arrow has adequate fletching clearance.

Arrow Left Tear (fletching tears left of point)

Factors to Consider:
Note: If you are left handed follow these instructions in reverse.

FINGER Shooters:
-Weak arrow or a clearance problem
This problem is cured using these methods:
a. Reduce bow weight
b. Use a lighter point
c. Select a stiffer arrow
d. Increase cushion plunger tension or use a stiffer spring on shoot around rests
e. Make small incremental rest adjustments away from the bow .

RELEASE Shooters:
-Arrow rest is too far to the left.
Move the arrow rest to the right.
-Arrow is too stiff.
Decrease bow weight or select a weaker arrow.

EITHER STYLE:
-Arrow is not properly clearing cables. Rotate cable guard for minimum fletching clearance.
-Clearance Problem - See that arrow has adequate fletching clearance.

Paper Tuning Perfect Hole

Paper Tuning Arrow High Tear

Paper Tuning Arrow Low Tear

Paper Tuning Arrow Right Tear

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