This video explains what the Reynolds Number is, how to calculate it, and how it affects the flight performance of gliders. An experiment is shown to demonstrate how changing the Reynolds number of a glider affects the distance it flies.
Links:
Glider build video:
https://www.youtube.com/watch?v=YzqS_NjTxps&t=4s
Air density and viscosity (by temperature):
https://www.engineeringtoolbox.com/air-absolute-kinematic-viscosity-d_601.html
Air density and viscosity (by altitude): https://www.engineeringtoolbox.com/standard-atmosphere-d_604.html
Timecodes
0:00 - Intro
1:11 - What the Reynolds number is
2:03 - How to calculate the Reynolds number
3:20 - Effects of the Reynolds number on the parasite drag coefficient
4:10 - Reynolds number demonstration
5:52 - Conclusion