One of the most enjoyable aspects of aeromodeling is exploring how far I can twist the common perceptions of aircraft design. Whether through radical asymmetry, cartoonish caricatures, or outlandish adaptations, my experiments often reveal that the limits of "airworthy" stretch far beyond what we are used to.
My tests usually only serve to satisfy my own curiosity. Yet, unusual design traits can sometimes provide unique benefits. For instance, I've heard that builders of pylon racers will occasionally configure their models with only a single aileron for roll control. It may sound trivial, but that is a radical departure from the norm. The vast majority of RC models have two ailerons - one on each wing, moving in opposite directions.
Like full-scale air racers, RC pylon racers fly at top speed in a counter-clockwise path marked by tall pylons. Although I've never actually seen a pylon racer with just one aileron, I've heard that this set-up provides adequate roll authority while making the airplane simpler and lighter (i.e. faster). Some even say that the adverse yaw caused by having an aileron on only the starboard wing actually makes these racers track through those continuous left turns better. [Adverse yaw occurs when unequal aerodynamic drag of the deflected aileron(s) makes the airplane yaw opposite the direction of roll…usually an undesired effect.]
While I do not often fly pylon racers, the potential weight, simplicity, and cost benefits of a single aileron set-up in a sport plane intrigued me. I decided to build an airplane with just one aileron to see how it would perform. Coincidentally, my model would have the aileron in the racer-preferred starboard wing. However, I would be asking my model to turn both left and right!
The model that I chose to build is the Parallax, an asymmetric park flyer I designed a few years ago. I already had a partially-completed example on my workbench. Most of the airframe was built, but the ailerons were not yet configured. So I knew that it would be a perfect candidate for my one-aileron experiment.
As expected, omitting the port aileron provided the obvious benefits of not having to purchase or install a second aileron servo, the necessary extension wire, or the relevant control linkages. Granted, the cost savings is not huge. Yet, when viewed as a percentage of my overall investment in the model, it's significant. The same can be said of the weight savings. This was my seventh Parallax build, and the lightest by more than an ounce…thanks in part to the omitted aileron.
When discussing the center of gravity (CG) for airplanes, we tend to focus solely on the fore-aft balance point. Yet, on an asymmetric model such as the Parallax, lateral balance is also an important consideration. The model is not any more sensitive than "normal" airplanes to lateral imbalance, but the unusual distribution of components means that good lateral balance can never be assumed. So I was attuned to the potential lateral balance effects of the absent aileron servo and kept everything in check.