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Performance Analysis of Flex Fletch Pro 2.5 at Various Helical Angles

Posted by Eric Newman- PNL Testers on Dec 12th 2024

Introduction 

In archery, fletching plays a pivotal role in stabilizing arrows during flight, directly influencing accuracy and consistency. Helical angles affect the spin imparted to the arrow, theoretically impacting both velocity and stability. The degree of impact on velocity depends on the aerodynamic efficiency of the fletching. In this study, arrows were configured with Flex Fletch Pro 2.5 vanes set at five different right helical angles (1°, 2°, 3°, 4°, and 5°). All arrows were fletched in a 3 fletch configuration. The test arrows, built using Black Eagle Carnivore 350 shafts with a total weight of 377 grains, were shot over distances of up to 60 yards. A LabRadar Doppler chronograph measured velocities at intervals, and fluid drag was calculated based on aerodynamic principles. The results were analyzed to determine how different helical angles influence velocity loss and drag. 

Drag, the aerodynamic resistance that opposes an arrow’s motion is an essential factor in understanding fletching performance. Drag influences the arrow’s velocity loss and overall stability during flight. This study examines how drag behaves when different helical angles are applied to the Flex Fletch Pro 2.5 vanes. 

Methodology 

Arrow Build and Setup 

 Arrow Shaft: Black Eagle Carnivore 350 spine 

 Insert: Ethics 50gr aluminum 

 Field Point: Ethics 100gr 

 Fletching: Flex Fletch Pro 2.5 at 1°, 2°, 3°,4°, and 5° helical angles 

 Weight: 377gr (minor variations: ±0.4gr across configurations) 

 F.O.C.: (Front of Center) 16.8% 

Measurement Tools 

 Velocity: LabRadar Doppler chronograph 

 Fluid Drag Calculation: Based on measured velocity drop-off and aerodynamic principles. (

 Drag force (Fd) was calculated using the equation . Where ρ represents air density, vis arrow velocity, Cd is the drag coefficient, and A is the cross-sectional area. This calculation helps assess how aerodynamic resistance affects the arrow’s velocity across different helical configurations. 

Weather at the time of the test 

Results and Analysis 

Velocity Loss 

Data Set of the fletching at 1° Table 1 displays the average velocity (fps) for a six-shot sequence with the Pro 2.5 set at 1°.

Data Set of the fletching at 2° 

Table 2 displays the average velocity (fps) for a six-shot sequence with the Pro 2.5 set at 2°.

Data Set of the fletching at 3°

Table 3 displays the average velocity (fps) for a six-shot sequence with the Pro 2.5 set at 3.

Data Set of the fletching at 4° 

Table 4 displays the average velocity (fps) for a six-shot sequence with the Pro 2.5 set at 4.

Data Set of the fletching at 5° Table 5 displays the average velocity (fps) for a six-shot sequence with the Pro 2.5 set at 5. Table 5 Velocity test Flex Fletch Pro 2.5 set at 5°

 Comparison of the Pro 2.5 and the various degrees of helical.

 In Table 6, we examine the velocity lost by comparing the different degrees of helical over a 60- yard test distance, as visualized in Figures 1 and 2. 

The results indicate that increasing the helical angle from 1° to 5° results in minimal variance in velocity loss. This suggests that accuracy and grouping consistency factors will be more significant when selecting a helical angle.

Fluid Drag

Since drag can influence arrow velocity and stability, analyzing fluid drag across various helical angles helps determine if increased spin affects aerodynamic resistance. The following results illustrate how drag changes with different helical configurations.

The minimal differences in drag observed across helical angles suggest that the Flex Fletch Pro 2.5 vanes are designed for aerodynamic efficiency. This allows archers to select helical angles based on stability and grouping needs rather than worrying about significant velocity loss due to increased drag.

Fluid drag (), expressed in Newtons (N), was calculated for each configuration at 20-yard intervals. The results are shown in Table 6 and visualized in Figure 3

Figure 3: Fluid drag across distances for varying helical angles. Key observation: Fluid drag values across configurations are consistent, suggesting that the helical angle's influence on aerodynamic resistance is minimal.

Discussion 

1. Velocity Consistency: o The differences in velocity loss across helical angles (1.2 fps) suggest that the aerodynamic profile of the Flex Fletch Pro 2.5 is highly optimized. This consistency may be attributed to its shape and material, which minimize disruptions in airflow regardless of helical configuration. (additional testing would be needed between other brands to verify) 

2. Fluid Drag Insights: o The negligible differences in fluid drag across helical angles (variations <0.001 N) indicate that changes in spin-induced drag are likely marginal compared to baseline aerodynamic drag. This implies that archers can select a helical angle for other priorities, such as stability or grouping, without concern for speed loss. 

3. Comparison to Literature: o Previous studies have shown that increasing the helical angle typically enhances stability but can increase drag. This study's findings challenge that notion, as drag differences were minimal even at 5°, suggesting that Flex Fletch Pro 2.5 has a unique aerodynamic efficiency. 

Conclusion 

The findings confirm that archers selecting a helical angle for the Flex Fletch Pro 2.5 can focus on factors like stability and grouping consistency without sacrificing velocity or aerodynamic performance. This study highlights the versatility of the fletching design, making it a reliable choice across different setups. Future investigations into the interplay of helical angles, spin stabilization, and arrow flight accuracy could provide even more actionable insights for hunters and competitive archers. 7

Limitations 

The test focused exclusively on velocity and did not account for accuracy or flight stability, which are critical for real-world applications. The single arrow build used in this study (Black Eagle Carnivore 350 spine, 377-grain total weight) provides valuable insights but limits the generalizability of results. Variations in shaft stiffness, weight, or environmental conditions, such as higher winds or extreme temperatures, could affect performance. Additionally, the exclusion of field accuracy testing leaves an important question open for future research. How do helical angles influence grouping under diverse conditions? 

Future Directions 

Proposed Future Research: 

 Accuracy Testing: Conduct accuracy tests (grouping) at varying distances to assess the practical effects of helical angles on precision. 

 Broader Arrow Types: Evaluate additional arrow shafts with different spine ratings, weights, and materials. 

 Dynamic Conditions: Include tests in varying wind conditions to determine how helical angles influence crosswind performance.