In article . com,
"Steve S." wrote:

I'm looking for input regarding the amount of air to blast through a
cockpit to offset the effects of solar heating under a large canopy.

...............

So, the crux of the question: Based on your gut, personal observations
or, in a perfect world, empirical data--how often do we need to have
an air changeover to keep a cockpit at a reasonable temp in hot sun?


Remember, too, that air can travel forward on the fuselage, from rear
stagnation points. If the canopy is well-streamlined, a port on the aft
end of the canopy will provide ventilation to the back of your head,
because pressure there is higher than on other parts of the plane.