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Lesson 1 Choosing the right TARGET equipment
1.1
Ideal target bow characteristics
Key aspects to look for in a target bow
38” axle to axle or more – 40” or better is ideal
7” of brace height or more – 8” is ideal
IBO speed rating of 300 FPS or better – 310 or better is ideal
Integral grip design with a slim throat
Minimal cam valley in the draw cycle, but enough that the bow does not feel uncontrollable
Positive draw stop design.
65% Cam letoff
Axle to Axle
Axle to axle is the measurement between to 2 axles on the bow where the cam eccentrics rotate on the limb. Figure 1.1a
Figure 1.1a
The axle to axle measurement is significant for several reasons. The longer the axle to axle, the more inherent lateral stability the bow will have. Lateral stability is associated with your ability to cant the bow left or right while at full draw. Canting the bow will cause left & right impact point variables especially at longer distances.
The longer your axle to axle is, the less string angle you will have at full draw. Excessive string angle from shorter axle to axle designs can cause a multitude of accuracy issues including nock pinch as well as difficulty anchoring. Axle to axle becomes more of an issue for longer draw length archers. As the draw length increases, the string angle increases dramatically.
Axle to axle length is less critical for shorter draw lengths up to 26”-28”, however when you get into the 29”-31” draw length range, longer axle to axle lengths become much more critical.
Brace Height
Brace height is the static measurement between the throat of the bow grip & the bowstring at rest. Figure 1.1b
Figure 1.1b
Brace height is the single most important factor in accuracy & your ability to be consistent. Think of brace height as the “Manageability Factor” for any given bow. The bigger the brace height, the easier it will be for you to repeatedly manage that bow! 7” in brace height is our suggested minimum, however 8” is ideal. The draw back with higher brace height bows is that you end up sacrificing speed as you increase the brace height. 1” of brace height is typically equated with 10FPS of speed in any direction. This is due to the fact that the brace height determines the “Power Stroke” of the bow. As you get below the 7” brace height range, bows become increasingly difficult to shoot in a consistent manner.
Speed
IBO speed rating is a standard that allows you to compare all bows using the same measurements. Standard IBO speed is based on 70 lbs of draw weight, 30 inches in draw length, using a 350 grain arrow. This is a ratio of 5 grains of arrow weight per pound draw weight. Shooting a bow with this 5 grains per pound ratio is often referred to as “Grained Out” since this is the lowest manufacturer suggested grain per pound ratio.
You will hear a lot of folks talking about how speed does not matter when it comes to target archery, especially when it comes to indoor shooting. We could not disagree more! Speed should not be considered over axle to axle or brace height, but it should certainly should be factored into your decision. There are a few reasons that speed is a concern when it comes to target archery that you should be aware of. A faster bow allows you the flexibility to shoot a heavier & more stable arrow. A faster bow also gets the arrow out of “The System” more quickly. What this means is that the longer the arrow is on the string, the more time there is available for your human actions to affect the impact point of the arrow before it hits the target. A faster bow will get the arrow off the string more quickly adding a positive effect of forgiveness to the setup. The actual time frame in comparison is only fractions of a second but the effects are quite obvious.
You can estimate that for every 1” of draw length under 30” in draw, you will lose 10FPS from the IBO standard rating.
EXAMPLE:
A bow is rated at 310FPS IBO.
You can expect the following speeds at 5 grains of arrow weight per pound of draw weight-
30” draw - 310 FPS
29” draw - 300 FPS
28” draw - 290 FPS
27” draw - 280 FPS
Grip Design
Most of today’s modern target bows have an integral slim throat grip built into the design of the riser. Here are several examples of desirable slim throat integral grip designs. Figure 1.1c
Figure 1.1c
Slim throat integral grip designs provide several desirable characteristics that allow you to be more consistent.
Minimized lateral surface area which means you are less likely to be able to torque the grip while at full draw
Narrow contact point creates a pressure point in your hand allowing you to consistently located the proper grip position by FEEL
Optimal grip angle allows for even distribution of vertical hand pressure in a consistent manner
We suggest that you test the grip designs for several manufactures & choose one that feels like HOME to you.
Cam Valley
A valley that is TOO LONG creates a SPONGY sensation at full draw. This creates a sloppy sensation where it is difficult to reach the actual draw stop at full draw.
A valley that is TOO SHORT makes it very difficult to hold the bow against the draw stop without exerting too much effort. This creates a tugging sensation where the bow wants to constantly come off of the back wall & collapse. This is often referred to as an “Arm Ripper” because it feels like the bow is trying to rip your arm out of it’s socket!
A desirable valley is obviously a happy medium between these 2 scenarios. You want just enough valley to allow you to feel comfortable & confident at full draw, while having zero SPONGE.
Draw stop
Most of today’s modern target bows have a positive draw stop built into the cam eccentrics. Some designs are obviously better than others. When properly applying back tension to your shooting, it is important that there is no “SPONGE” in the draw stop. The more solid the draw stop, the more accurate & consistent the bow will be. If you are shooting with a PUSH/PULL shot execution, a solid draw stop is KEY in your ability to properly execute the shot.
Draw stop designs range from cam posts that contact the cables at full draw, to cam PEGS that contact the limbs at full draw. On a Dual cam or Cam & ½ type systems, the cam timing is critical to the way the bow feels at full draw. If the timing is not correct & both cams do not hit the draw stop at the same time, the back wall will feel spongy & you will often see inconsistent arrow groupings as well.
Positive draw stops that contact the limb should be configured so that the draw stop makes contact slightly before the bow reaches the peak of the valley.
Cam Letoff
Most target bows are going to be configured with anywhere from 65% - 80% let off. The higher the let off, the less tension there is on the bow string at full draw. This means that the bow string is much more susceptible to human induced forces such as torque from release aids, and string to face contact. Any minimal force implied upon the string is amplified & results are translated to anomalies on the target face such as poor overall arrow grouping & random FLYERS.
Less let off means that there is more tension on the bow string at full draw making it far less sensitive to outside influences.
Less cam let off means more holding weight at full draw. The holding weight of your bow is an important factor because it will assist in off-setting the mass weight of your bow at full draw. We will discuss this concept more in depth along with balancing your bow in a separate lesson.
1.2
Draw Length
When you are choosing a target bow, it is important that the draw length is correct for you. In Section 1 – Lesson 6, we broke down the steps & details associated with finding your correct draw length. Once you find your correct draw length it is important that you have a way to effectively measure & track this information. You need to be able to track possible changes in your equipment, and you need to be able to compare your correct draw length to any new bow that you are considering purchasing. Although most manufactures specify that they use AMO standards when stating draw length, the reality is that there is often a large variable not only between manufactures, but also between different bow models from the same manufacturer.
Manufactures use what is called an AMO standard method of specifying draw length which is the TRU-DRAW plus 1 ¾”. Figure 1.2a
Figure 1.2a
TRU-DRAW is the measurement from the throat or (Pivot Point) of the grip to the back of the bowstring at full draw. Even though most manufacturers leverage the AMO standard, often times there are significant variables between manufacturers as well as from bow to bow in regards to TRU-DRAW vs. the stated AMO draw length. Keep in mind that when a bows draw length is adjustable by swapping or adjusting modules, often times the settings between the high & low end do not equal exactly ½” as stated. Along with that concept, keep in mind that the actual draw length of any given bow can vary from the AMO standard due to incorrect timing, cam position, as well as string stretch.
TRU-DRAW is the measurement of the actual physical draw length on any given bow which you can use to then compare draw lengths between bows in order to find the correct fit. This information will allow you to find your correct draw length on any given bow.....
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