Trimming a model plane for hands-off straight and level flight is the first thing we do upon launching a new or unfamiliar R/C plane. Many of us don't give it another thought after that; but periodically we do notice quirks about our airplanes when we attempt aerobatic maneuvers. Often we pass off these quirks as part of our planes' ``personality'', but more often it is an imbalance that can be readily fixed... by trimming. In this two part column, we'll explore basics of R/C model trimming as well as the most esoteric trimming tests designed for competition aerobatics. The idea for this series blossomed from a ``Trimming for Precision Aerobatics'' table mailed to me by John Defile (well, I *think* it's Defile - it looks like the Postal Service dropped the envelope in acid before putting it in my mailbox; please correct me if I'm wrong!).
It's the Big Lie. We've all heard it, and many of us have even said it ourselves - ``It flew right off the drawing board - no trim needed!'' All planes need to be trimmed in one way or another, even within a flight to reflect changing flight patterns (climbout, cruise, gliding). Even full scale planes have trim tabs for just this purpose! But just the flight controls themselves don't tell the whole story... they're not the only things that matter. What about wing and stabilizer incidences? Dihedral? Downthrust? Tail alignment? Often we eyeball such things, and trust that the model designers knew what they were doing. But maybe what you want to do with your model is not what the designers had in mind! Then, the ball's in your court...
Let's start with the basic stuff first.