Ford 15-P a great success?
They built exactly 1. It didn't fly much and little to no test data survives to be called successful. After several test flights it had an accident and was put into storage, never to fly as a fixed-wing aircraft again. It might have done much better if it had a vertical tail for yaw control, but I can't say for sure. The fuselage flew later as an autogyro. I'm assuming it had a rudder and fin at that time.