RE: FlyFly BAe Hawk 90mm EDF
Jyri,
Most rotors are not symmetrical so they can't be reversed but the FlyFly rotor is symmetrical so it works. What our friend from Australia is missing is that it still spins in the same direction so the stators inside the housing remain efficient. Try not to confuse turbine requirements with EDF requirements because they often differ. Most notably is the air intake requirement which is why EDF conversions of turbine-powered jets has not taken off.
Many people have their favorite ways to do things and sometimes harp on maximum efficiency but there are often many solutions. The ducted fan that comes with the FlyFly models is very usable and there is no need to replace it. Notice the promotion at the end of the post for Extreme RC in Australia.
Regards.