I extend an invitation for the aeronautical/ fluids/ physical/ mechanical/ etc. types among us to opine on why the once promising and highly-touted technology of bicambered airfoils has not resulted in tangible products that we can use in our avocation.  In other words, what's wrong with it?

Greg

 

It's patented.

 

However, one could say that the wing with reflexed flaps used in the Lancair 300 series is a form of semi-demi bi-cambered wing.  It does indeed reduce drag in the reflexed regime (upper air reattached at the flap), pitching moment and lift changes notwithstanding.  

 

I once had a "dog-bone" prop made for an experimentally registered heavy ultra-light that did use the bi-cambered construction concept for the blade surfaces (hence the dog bone looking cross section).  I used it once - never again. It delivered some thrust at max RPM and less noise.  It delivered no thrust and little noise at less than max RPM (except for my screams on the short test flight). 

 

I am sorry that this is not the engineer's reply you are seeking.  Perhaps the wind tunnel doesn't work the same as flights in earth's atmosphere.

 

Does rain pool in the concave upper portion whilst parked?  Does that later freeze on a cold day and, uh, break things?  Does it accumulate ice on the front and back parts of the airfoil if flown in icing conditions?

 

Grayhawk