Draw Length
The most important factor for consistent and accurate shooting is having the correct draw length set on your bow. It’s important to realise that a couple of millimetres matter when it comes to draw length.
To measure your draw length, there’s two options:
- Actual Draw Length
This is the draw length used in the industry and is measured horizontally throat of the grip to the string at full draw and then add 1 ¾ inches to the measured value. This method doesn’t take the D-loop length into account. - Practical Draw Length
This is the one that really matters, and there’s no official term for it. It is measured horizontally from the throat of the grip to the D-loop at full draw. This takes the D-loop length into account, making it more practical to work with.
This is the value, together with the length of your D-loop, you’d like to repeat between bows, if possible.
The initial draw length is normally set by:
- Draw Length specific Cams.
- Draw Length specific Cams with screw-on Modules and optional Draw Stops.
- Draw Length Specific Cams with Adjustable (rotating) Modules.
Options for fine tuning draw length include:
- D-loop length
- Twisting/Untwisting the String & Cables
D-loop Position & Length
The D-loop position influences both hold and arrow-flight. Moving the D-loop up and down the string will change the way the bow holds on the target, as well as the position relative to the centre of the rest.
A too high D-loop will likely result in high bobbing or a floating pin, like a too long draw length, while a too low D-loop will cause the pin to drop out of the bottom of the aiming point.
Moving the D-loop up the string will cause the impact point of the arrow to lower on the target, and moving the D-loop down will raise the impact point of the arrow on the target. Be mindful not to miss the target due to this while testing, thus moving the D-loop more than one rotation around the string is not advised.
It’s not suggested to move more than about 7-10mm from the centreline through the Berger-holes up or down, and not far enough down to cause the arrow to impact the rest.
Note that changing the D-loop position will impact your cam timing.
A short D-loop may have the effect of raising the archer’s elbow, effectively causing the archer to pull the D-loop attachment point up. This is in some ways like having a too high back shoulder.
You may benefit from a longer D-loop if you have a good anchor point of the string relative to your face, but you’d like to lower your elbow position.
The other issue you may encounter with a too short d-loop is that it may input torque into the bow string if the release aid angle is very high relative to the string.
Tiller
Tiller refers to the calculated difference in actual distance between the upper limb to the string and lower limb to the string measured from the base of the limbs, usually where the limb and riser meet. It is measured at a 90-degree angle to the string.
The recommended is to start at 0mm tiller, meaning the top and bottom limb bolts would be screwed in an equal amount if the limbs have the exact same tension. Changing the tiller allows for slight imbalances in the limb strength between top and bottom to be negated by varying the tension in one limb by adjusting the bolt. It can also be used to purposefully introduce an imbalance between the top and bottom limbs.
This would affect both arrow flight and the way the bow holds steady at full draw.
This level of fine tuning is usually reserved for extremely consistent & accurate high-level archers.
Cam Synchronisation & Timing
Cam timing and synchronisation is important as it will influence the arrow flight as well as how stable the bow holds on target.
Consult the manufacturer of the bow for the optimum settings for the cams, including the location of any cam position or timing marks.
It is possible for cams to be synchronised but not timed correctly. It is not possible to be out of timing and synchronised.
Sometimes an archer may have a specific personal preference for one cam to stop rotating slightly before the other, e.g., the top cam stopping first to allow the bow to “pull upwards” as the bottom cam still rotates. Please note that this can influence arrow flight and result in vertical inconsistencies if the archer isn’t very consistent against the back wall.