Once upon a time, some rotor rooters spent many evenings drinking beer and discussing rotorcraft ideas. For years the only outputs from this group were 'letting off gas' and mad dashes to the urinal. Finally, their ultimate craft evolved and, quite naturally, they called it the 'Fart-n-Dart'.
Head Turner ~ Seriously, one of the features might be of interest.
They designed the fuselage so that it was aerodynamically in balance about its vertical axis. By doing this, a wind from any direction would not yaw the craft. This allowed the yaw control to be handled by a very small tail rotor
[The smaller the better. Infinitely small being infinitely better ~ but that's another story. 
]
In forward flight they need more "drag' at the rear of the craft to hold the course, of course. To achieve this they had a vertical stabilizer with a small chord. The trailing edge of the vertical stabilizer had a slat, similar to a rudder but this slat only slide forward and aft. It did not pivot. As the craft's forward velocity increased, this trailing edge slat extended back. This increased the vertical stabilizer's chord and resisted unwanted yaw. During rearward flight the chord decreased.
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The helicopter was not a big seller. Some say it was because too much time was spent in the engineering department and too little time in the marketing and legal departments. A few suggest that it might have been the name.
Anyone have additional information on the 'Fart-n-Dart'?
Edited to record publication of concept ~ OTHER: Aerodynamics - Rotorcraft Concept - Variable Vertical Fin