Effect of Longitudinal Ridges on the Aerodynamic Characteristics of an Airfoil

Here's a Cub airfoil with allegedly STOL gadgets. Not sure what to make of all this - I assume they're serious and sober. Reynolds Number of test about 20 m/sec or 45 mph .

https://www.researchgate.net/public...the_Aerodynamic_Characteristics_of_an_Airfoil

Gary