Convert rear to pusher prop in forward motion?

[cchance27]

Just wondering why not transition the rear prop into a pusher prop during forward flight? Seems its almost setup to work if you used the same pod style from the form in stead of the arm from the back

[StephenCarlson]

Sorry for the delay. My stance is... no, it is not appropriate to have all the motors participate in all modes of flight. Each motor/set is specialized/optimized for their respective role. It is important to realize that each motor/rotor has a Thrust-Available curve (see Introduction to Flight by John D. Anderson Jr., Chapter 6.4), with zero-velocity static (hover) thrust on one edge intersection, and the pitch-speed (near-zero thrust force) occurring on the orthogonal edge intersection. Adding forward-flight rotors will increase total thrust available, but the pitch speed for each rotor remains an individual attribute, and if the rear rotor is optimized for hover, its pitch speed will be rather low, to that point that having it try to participate in forward flight is actually quite wasteful and even damaging to efficiency. The MiniHawk already, with just two 5-inch props on the front, is capable of climbing vertically. Really, it needs smaller motors on the front that are tuned for 20m/s, but the prop discs must be large enough to contribute correctly during hover, so we are a bit stuck with 5-inch props and inefficient forward cruise.