1. What is Arrow Spine?

Arrow spine refers to the stiffness of an arrow shaft, measured by the amount of deflection (in inches) when a 1.94 lb weight is suspended from the center of a 28" arrow supported at two points 26" apart. Proper spine selection is crucial for accurate arrow flight.

2. How Does the Calculator Work?

The calculator uses the spine formula:

Where:

• \( Deflection \) — Measured deflection under load (inches)
• \( Weight \) — Applied weight (lbs)
• \( Length \) — Arrow length (inches)
• \( Constant \) — Material adjustment factor

Explanation: The formula accounts for how different materials and lengths affect the arrow's stiffness.

3. Importance of Proper Spine Selection

Details: Correct spine is essential for optimal arrow flight, accuracy, and consistency. Arrows that are too stiff or too weak will not fly properly and can affect accuracy.

4. Using the Calculator

Tips: Measure deflection with arrow supported at two points 26" apart. Apply known weight (typically 1.94 lbs for standard measurement). Enter arrow length and select material type.

5. Frequently Asked Questions (FAQ)

Q1: What is the standard spine measurement method?
A: The standard measures deflection with a 1.94 lb weight on a 28" arrow supported at 26" span.

Q2: How does arrow length affect spine?
A: Longer arrows act weaker (more flexible), shorter arrows act stiffer. The effect is cubic (length^3) in the calculation.

Q3: What are typical spine values?
A: Common spine ratings range from 300 (stiff) to 800 (flexible) for adult arrows. Lower numbers indicate stiffer arrows.

Q4: How does point weight affect spine?
A: Heavier points make the arrow act weaker, lighter points make it act stiffer. This calculator doesn't account for point weight.

Q5: Why different constants for materials?
A: Different materials have different stiffness properties. Carbon is generally stiffer than aluminum for the same dimensions.