What Is Compound Bow Let Off – Working and Adjustment

Imagine you are looking for the perfect compound bow to buy at the archery store and the assistant asks you your let-off percentage, or you are scrolling on an online store and find 75% let-off in the specifications section. Now you might wonder, “What’s let-off?” No worries, I’ll explain!

I will first introduce you to the concept of bow let off, how it works and then I will cover relating details such as factors affecting bow let off, advantages and disadvantages of bow let off and how to choose the right let off.

What is Bow Let Off?

Bow let-off is a characteristic unique to compound bows, distinguishing them from traditional or recurve bows. Let off refers to the point in the draw cycle where the bow’s cams rotate, allowing the archer to hold less weight when fully drawn. This mechanical advantage eases the strain on the archer while aiming, leading to a more comfortable shooting experience.

Let off Percentage

The let-off percentage represents the percentage of draw weight reduction at full draw compared to the peak draw weight. For instance, a bow with 80% let-off at 70 lbs peak draw weight will only require the archer to hold 14 lbs at full draw (80% of 70 lbs).

The Mechanics of Bow Let-Off:

The cam system is a critical component in compound bows that enables the bow’s let-off functionality. The cam system consists of two primary components: cams and cables. The asymmetrical shape of cams is the key to this concept. Both components play a vital role in controlling the bow’s draw cycle and determining the let-off characteristics.

Working of Cams in the Draw Cycle:

Compound bows utilize a system of cables and cams to store energy, resulting in powerful arrow propulsion. The cams, found on both ends of the bow, play a crucial role in guiding the bowstring during the draw cycle and generating stored power.

As the archer begins to draw the bowstring, the cams rotate slowly, incrementally increasing the draw weight. During this initial phase, the archer overcomes the resistance from the bow’s limbs, which possess elastic properties and naturally want to return to their original position.

The unique elliptical shape of the cams facilitates a smoother draw for the archer. As the bowstring is drawn back, the cams contribute to bringing the bow limbs closer together, thus storing energy for the shot.

As the draw cycle continues, the cams eventually reach a significant point called the “let-off position.” At this critical moment, the cams’ shape and orientation undergo a transformation that leads to a substantial reduction in draw weight.

The let-off position marks the shift in draw weight from the archer to the bow’s limbs. This transition results in a considerable decrease in the effort required to hold the bow at full draw. As a consequence, the archer experiences increased comfort and stability, enabling them to maintain a steady shooting position.

Once the bow reaches full draw, the draw weight is mainly transferred to the bow’s limbs, allowing the archer to achieve exceptional power without having to bear the peak draw weight.

The incorporation of cams and cables in the compound bow design gives rise to a unique feature known as the “valley” or “let-off.” Approximately halfway to two-thirds through the draw cycle, the cams “roll over,” drastically reducing the draw weight that the archer holds at full draw compared to the peak draw weight. This let-off position enhances shooting comfort and precision, making it easier to achieve accurate shots.

This draw cycle curve is the complete explanation of bow let off. Initially the archer pulls the bowstring and the draw weight increases exponentially. Then after reaching the peak weight the shape of cam changes and all the draw weight is shifted to the limbs. After the shape of cam changes like shown in the picture above, the draw weight drastically reduces after a point known as let off.

Different Types of Cam Systems and Their Impact on Let-Off:

Here are some characteristics of different types of cam systems related to let off. If you are interested in knowing more, here is a guide about the different cam systems

Advantages and Disadvantages of Bow Let-Off:

Advantages of Bow Let-Off:

Reduced Holding Weight:

The primary advantage of bow let-off is the significant reduction in holding weight at full draw. With a high let-off percentage, archers need to exert less effort to keep the bow drawn, leading to enhanced comfort and stability during aiming. Reduced holding weight allows archers to hold the bow steady for more extended periods, crucial for consistent and accurate shooting.

Increased Accuracy and Stability:

Bow let-off plays a pivotal role in improving shooting accuracy. By reducing the effort required to hold the bow at full draw, archers experience less muscle fatigue, enabling them to maintain a steady aim for precise shots. The minimized tension in the muscles contributes to greater stability, resulting in more consistent groupings and better overall shooting performance.

Enhanced Comfort and Endurance:

The reduced physical strain on the archer’s muscles due to let-off allows for a more comfortable shooting experience. This is especially beneficial during prolonged practice sessions or while waiting for the perfect shot during hunting. Archers can focus more on their aiming and form without the distraction of muscle fatigue.

Better Shot Timing and Follow-Through:

Bow let-off facilitates better shot timing and follow-through. Archers can concentrate on their release technique without being rushed by the need to hold the bowstring at full draw. This contributes to smoother shots and helps maintain proper form, further contributing to accuracy and consistency.

Disadvantages of Bow Let-Off:

Speed Trade-Off:

One of the main disadvantages of high let-off is the potential trade-off in arrow speed. As the draw weight decreases at the let-off position, the stored energy in the bow decreases too, resulting in slightly slower arrow speeds compared to bows with lower let-off percentages. Archers who prioritize arrow velocity over comfort may opt for lower let-off percentages to achieve higher arrow speeds.

Limited Holding Time:

While bow let-off allows for increased comfort and endurance, there is still a practical limit to how long an archer can hold a drawn bow. Even with reduced holding weight, a continuous full draw can lead to muscle fatigue over time. Archers must find a balance between their let-off percentage and their physical capabilities to maximize shooting performance.

Adjustment Complexity:

For some archers, the process of adjusting bow let-off to suit individual preferences can be complex. Compound bows with adjustable cams and modules may require professional assistance or in-depth knowledge to fine-tune the let-off percentage accurately. Incorrect adjustments could negatively impact shooting performance and safety.

Preference Variability:

The ideal let-off percentage is subjective and varies from archer to archer based on shooting style, discipline, and personal preference. While some archers may prefer a higher let-off for comfort and stability, others may opt for a lower let-off to maintain higher arrow speeds and feel more connected to the bow’s draw cycle.

Factors Affecting Bow Let-Off:

Draw Length and Let-Off:

The draw length directly influences the let-off percentage, affecting how the bow feels at full draw. If you draw both bows to their full length, the bow with the longer draw length will likely have a slightly higher let-off weight reduction. This is because the cams have more room to adjust and reach their optimal let-off position. Finding the right balance between draw length and let-off is essential for optimal shooting performance.

Draw Weight and Let-Off:

The draw weight of a compound bow affects the let-off percentage. Higher draw weights often come with more let-off to make holding the bow at full draw easier, while lower draw weights might have less let-off because the effort required to hold the bowstring is already manageable. Higher draw weights often result in higher let-off percentages, making it easier for archers to hold the bow steady.

Cam Design and Let-Off:

Different cam designs offer varying let-off characteristics. Some cams provide a smoother draw and more aggressive let-off, while others may be more forgiving or adjustable. Understanding the cam design’s impact is crucial for selecting the right bow for individual needs.

How to Adjust Bow Let-Off:

Adjusting bow let-off in a compound bow requires careful attention to the cam system and its specific design. To achieve the desired let-off percentage, archers can typically make adjustments using cam modules or rotating the inner and outer cam positions. However, before attempting any changes, it is essential to refer to the manufacturer’s guidelines and user manual for the specific bow model. Some bows may require the expertise of a professional bow technician for precise adjustments.

Archers should start by determining their preferred let-off percentage and then proceed with caution, making incremental adjustments while regularly testing the draw weight to find the optimal setting. As let-off adjustments directly impact shooting performance and stability, it is crucial to ensure proper tuning and maintain a balanced setup for a safe and accurate shooting experience.

Let-Off and Shooting Performance:

Impact of Let-Off on Arrow Speed:
Bow let-off can influence arrow speed since a higher let-off percentage usually results in a decrease in arrow speed. Archers should find the right balance between let-off and arrow speed, considering their shooting style and discipline.

Let-Off’s Influence on Arrow Trajectory:
Let-off affects how an archer holds the bow during the shot, which can influence the arrow’s trajectory. A smoother draw and reduced holding weight enhance stability and improve the consistency of arrow flight.

Considerations for Different Archery Disciplines:
The ideal let-off percentage may vary depending on the specific archery discipline. Target shooters may prefer higher let-off for comfort and precision, while hunters may opt for slightly lower let-off to achieve faster arrow speeds.

How to Choose the Right Let-Off:

Let-Off for Target Archery:

In target archery, where precision and consistency are paramount, selecting the appropriate let-off percentage is crucial for achieving steady aiming and accurate shots. For target archers, a higher let-off percentage is generally recommended, usually around 80% or more. Here’s why:

Recommended Let-Off: Approximately 80% or higher.

Reasons:

1. Comfort and Stability: Target archers often spend extended periods aiming and executing shots during competitions or practice sessions. Higher let-off significantly reduces holding weight, allowing archers to hold the bow steady with less fatigue. This enhanced comfort and stability contribute to improved consistency in shot placement.
2. Aiding in Fine-Tuning: Target archers require precise aiming and shot execution. Higher let-off allows them to focus more on their form, release technique, and aiming without being overly concerned about holding the bow at full draw. The let-off assists in fine-tuning their shot process and ensures a smoother execution.
3. Consistency in Practice: Consistency is key in target archery. With reduced holding weight, archers can consistently replicate their shooting form and release, leading to tighter groupings and better scores.

Let-Off for Hunting Archery:

In hunting archery, where quick and accurate shots are essential, the let-off percentage may differ from that of target archery. Hunting situations require bows with higher kinetic energy for maximum arrow speed and sufficient penetration. Therefore, a lower let-off percentage is often preferred for hunting bows.

Recommended Let-Off: Around 65% to 75%.

Reasons:

1. Arrow Speed and Kinetic Energy: Hunting archers often prioritize arrow speed to reduce the chance of animals reacting to the shot. Lower let-off percentages ensure that more energy is stored in the bow, translating to higher arrow speeds and improved penetration upon impact.
2. Faster Follow-Up Shots: In hunting scenarios, archers may need to take quick follow-up shots if the first shot does not result in an immediate kill. A lower let-off percentage allows archers to hold the bow at full draw with less effort, enabling faster and more accurate follow-up shots if needed.
3. Increased Connection to the Bow: For some hunting archers, a lower let-off percentage provides a more connected feel with the bow throughout the draw cycle. This can help maintain a heightened sense of control and awareness during the crucial moment of the shot.

Final Consideration:

While these recommended let-off percentages are a general guideline, individual preferences may vary. You need to test different let-off percentages personally and find the one that best suits your shooting style, physical capabilities, and intended archery activities. Regardless of the archery discipline, choosing the right let-off ensures a more enjoyable and successful archery experience.

Frequently Asked Questions (FAQs):

Can let-off be changed?

Yes, many compound bows allow let-off adjustments through cam modules or positions.

What is the best let-off for a bow?

Target archers often prefer a higher let-off (around 80% or more) for stability, while hunters may opt for a lower let-off (around 65-75%) for arrow speed.

What is the let-off on a compound bow?

Let-off on a compound bow refers to the percentage reduction in draw weight at full draw.
Example: If a compound bow has a 70% let-off, and its peak draw weight is 70 pounds, the archer would be holding only 21 pounds (30% of 70 pounds) at full draw.

What does 85% let-off mean in a bow?

85% let-off on a compound bow means there will be a weight deduction of 85% at let-off. For example, with a compound bow with a peak draw weight of 60 pounds, the archer would be holding just 9 pounds (15% of 60 pounds) at full draw.

How does let-off affect arrow speed?

Higher let-off can slightly reduce arrow speed compared to lower let-off bows due to decreased stored energy.

Is a higher let-off always better for accuracy?

Accuracy depends on multiple factors; some archers find a lower let-off more beneficial for better control and consistency.

Can let-off adjustments affect bow performance?

Yes, improper adjustments may lead to inconsistencies and affect shooting performance. Seek professional help if unsure.

Conclusion:

Bow let-off is a game-changing feature that sets compound bows apart from other bow types. It provides archers with reduced holding weight, resulting in increased accuracy, comfort, and endurance during shooting sessions. Understanding the mechanics of bow let-off, the role of cam systems, and how to adjust let-off percentages are essential for optimizing shooting performance.

When selecting a compound bow, factors like draw length, draw weight, and cam design should be considered to find the ideal let-off setup. Whether you are a target shooter or a passionate hunter, bow let-off can significantly enhance your archery experience.
For expert tips on selecting the perfect compound bow, don’t miss our article on The Ultimate Guide to Choosing a Compound Bow.

So, take your aim with confidence, and explore the world of compound bows with let-off. Remember to experiment and fine-tune your setup to achieve your best performance on the archery range or in the field.