Overview
Restorative lift refers to the aerodynamic forces that help stabilize and re-align an arrow's flight path following a disturbance or initial misalignment (e.g. an out-of-tune bow or torqued shot). While direct measurement of aerodynamic lift in free flight is extremely challenging, this study used controlled horizontal misalignment to quantify the arrow's ability to recover (or not recover) from an imposed angular deviation. The result is a practical, real-world proxy for restorative lift based on observed group position at distance.
Test Environment and Setup
- All testing was performed indoors at the Easton Salt Lake Archery Center (Easton Foundation), Salt Lake City, UT, under the same controlled conditions used for drag and velocity measurement.
- An Easton Archery custom shooting machine was used to ensure precise, repeatable shots and to eliminate human error.
- For this protocol, the Hoyt AX-2 29 bow was intentionally set out of tune and consistently torqued horizontally to produce a nock-left tear of approximately 1.5 inches at 15 feet. This setup induces a consistent horizontal launch angle error across all test arrows.
Arrow and Broadhead Types
- Two field points
- Two Sevr 2.0 mechanical broadheads
- Two Iron Will Wide fixed blade broadheads
Each arrow was shot at a 70-yard target using the same shooting machine and out-of-tune bow setup.
Impact Measurement and Image Analysis
- Each group of arrows was photographed at the target using a Lumix S5MII camera, positioned consistently for all shots.
- A 36″ piece of tape was included in every photo for scale calibration.
- Photos were converted to PDF and analyzed with Blue Beam software. A digital marker was placed on each arrow impact, and the X-coordinate (horizontal displacement) was recorded.
- To correct for slight camera alignment variations, a fixed reference point was marked on the left side of the target and its X-coordinate was also recorded.
- Only horizontal displacement (X) was considered; vertical displacement (Y) was not analyzed for this study as there was variation in drop due to aerodynamic drag.
- A scale factor was applied using the tape reference, and the horizontal distance from the fixed point to each arrow impact was computed in inches.
Data are presented as horizontal deviation from the reference point for each arrow and broadhead type.
95% confidence intervals were computed based on the t-distribution, with degrees of freedom equal to the sample size minus one, to appropriately reflect the increased uncertainty associated with small sample sizes.
Interpretation as Restorative Lift Proxy
Less deviation from the fixed reference point indicates greater aerodynamic correction (restorative lift) of the initial misalignment, resulting in more controlled arrow flight. Conversely, greater deviation suggests less restorative effect and less ability for the arrow to recover from the induced horizontal angular velocity.
While restorative lift was not measured directly, this protocol captures its effects through repeatable, measurable outcomes at 70 yards. Results are compared across vanes to assess differences in aerodynamic stability and recovery.