How did you arrive at 1.5%?

L = Wcos(theta)


Come on Greg, you're telling me that wings in wind tunnels have no
induced drag? That's ridiculous. How about if the wind tunnel was
1000 miles long by 10 miles high - would the wings in that wind tunnel
have induced drag? (I seem to remember this same argument a few
months ago)


Argument? No, Todd Pattist and I attempted to educate you on this
subject, but apparently failed.

The size of the wind tunnel is irrelevant. What matters is that the
wing tips are flush against the walls of the wind tunnel. This
produces 2-D airflow, rather than 3-D. In 2-D flow, there are no wing
tip vortices and thus will have no induced drag.

(If you would read something other than Aerodynamics for Naval
Aviators, you'd understand this.)