I am going to disagree with one of my learned friends above.

It is perfectly possible to make turns with a rudder providing the wing has dihedral.

Many of us old timers started flying radio control with only one channel and that was rudder.

This is one of the most well known small [ almost indestructible ] one channel models the Sharkface designed by Eric Clutton.

There has been a resurgence of interest in flying rudder only models in the UK with the availability of reliable single channel outfits using a single modern servo which mimics the control we had.

I flew my Sharkface with a sequential escapement powered by a long rubber band which had to be wound before ever flight. If the last press was right rudder the next press was left then the next press was right.