"Let off" on a bow refers to the significant reduction in the amount of weight an archer needs to hold back at full draw, primarily found in compound bows. This mechanical advantage allows an archer to hold the bow at full draw with much less effort, aiding in aiming stability and reducing fatigue.
Understanding Let Off in Archery
Let off is a unique feature of compound bows, which utilize a system of cams (or wheels) and cables to achieve their mechanical advantage. As an archer draws a compound bow, the draw weight increases to a peak, but as the cams roll over towards the end of the draw cycle (at "full draw"), the draw weight dramatically decreases. This reduction in holding weight is what is known as "let off."
The let off for compound bows is typically expressed as a percentage. This percentage indicates the amount of the peak draw weight that is "let off" or reduced at full draw. For example, if a bow has an 80% let off, it means that at full draw, the archer is only holding 20% of the bow's peak draw weight.
Practical Example
Let's illustrate with a common scenario:
Characteristic | Value |
---|---|
Peak Draw Weight | 60 pounds |
Let Off Percentage | 80% |
Weight Reduction | 60 lbs * 0.80 = 48 lbs |
Holding Weight | 60 lbs - 48 lbs = 12 lbs |
In this example, an archer drawing a bow with a 60-pound peak draw weight and 80% let off would only need to hold back approximately 12 pounds at full draw. This drastically reduced holding weight makes it much easier to hold the bow steady, aim precisely, and maintain good form for extended periods.
Benefits of Let Off
The primary benefits of let off for archers include:
- Increased Aiming Time: With less weight to hold, archers can spend more time on target, refining their aim without muscle fatigue setting in quickly.
- Improved Accuracy: A stable holding position leads to more consistent shot execution and, consequently, better accuracy.
- Reduced Fatigue: Holding significantly less weight allows for longer practice sessions and makes hunting or competitive shooting less physically demanding.
- Easier Hold in Challenging Conditions: It's particularly beneficial when shooting from awkward positions, during cold weather (when muscles tire faster), or during long hunting waits.
How Does It Work?
The let off mechanism is engineered into the design of a compound bow's cams. As the string is drawn, the shape of the cams causes the leverage to change, effectively reducing the force required to hold the string back once it reaches the "valley" of the draw cycle. This mechanical advantage is why compound bows can store a lot of energy for powerful shots while still being relatively easy to hold at full draw.