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Airfoil Research

A project log for ArduAOA

Use BLE enabled Arduinos to collect Angle of Attack (AoA) information and display

tklenketklenke 11/24/2023 at 16:010 Comments

Ideally we will collect data from the unit and calculate our cruise AoA, landing AoA (1.3 Vso) and stall speed Vso from empirical data.  But to get started I looked into the theoretical AoA information for the PA-18 Supercub, our intended test bed. 

Found The Incomplete Guide to Airfoil Usage to determine the airfoil in use on a PA-18, which is the USA 35B.  Found NACA Report 233 on the airfoil as well as listing in Airfoil Tools

Reynold's number

Been a hot minute since I calculated Reynold's number, so asked to phone a friend.  Need to vet this but here's a start.  

Certainly! Let's calculate the Reynolds numbers for the given velocities:

  1. At 35 mph (15.65 m/s): Re=(1.225 kg/m3)⋅(15.65 m/s)⋅(1.6 m)(1.81×10−5 Pa\cdotps)Re=(1.81×105 Pa\cdotps)(1.225 kg/m3)(15.65 m/s)(1.6 m)  Re≈1.76×106 Re1.76×10^6
  2. At 50 mph (22.35 m/s): Re=(1.225 kg/m3)⋅(22.35 m/s)⋅(1.6 m)(1.81×10−5 Pa\cdotps)Re=(1.81×105 Pa\cdotps)(1.225 kg/m3)(22.35 m/s)(1.6 m) Re≈2.51×106 Re2.51×10^6
  3. At 70 mph (31.29 m/s): Re=(1.225 kg/m3)⋅(31.29 m/s)⋅(1.6 m)(1.81×10−5 Pa\cdotps)Re=(1.81×105 Pa\cdotps)(1.225 kg/m3)(31.29 m/s)(1.6 m) Re≈3.51×106 Re3.51×10^
  4. At 110 mph (49.16 m/s): Re=(1.225 kg/m3)⋅(49.16 m/s)⋅(1.6 m)(1.81×10−5 Pa\cdotps)Re=(1.81×105 Pa\cdotps)(1.225 kg/m3)(49.16 m/s)(1.6 m) Re≈5.50×106 Re5.50×10^6

So something like 2,000,000 to 6,000,000

Airfoil Tools gives us the following plots for Re 500,000 and 1,000,000

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