Old 11-15-2020, 06:02 AM
  #21  
franklin_m
 
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Originally Posted by astrohog View Post
That exit hole would be more effective with a small lip extending downward As seen in the picture below.
(CORRECTED)
Astro is correct here. Mechanical things like these lips function to redirect airflow in order to expand the low pressure area downstream ... which enhances the airflow through the cowl.

These and other air exits are sometimes placed on the bottom of the aircraft for the simple reason that air flowing through those fins often pick up dirt and minor bits of oil and other fluids, and most owners would rather have that dirt on the bottom of the plane than on the sides. However, that is not universally true either.

Below is an example of the other low pressure areas on that same cowl, which sure looks like it's a super cub.


Last edited by franklin_m; 11-15-2020 at 09:03 AM. Reason: Corrected - brain f*rt