(by Fred Talasco) Brief: A BT-60 based upscale of the classic ESTES Blue Bird Zero, designed for 24mm, D, E, and F motors. Construction: Parts are very basic and are available from Balsa Machine Services. Balsa cone and fins, paper BT-60 body tube and motor mount, and letramax centering rings. Once you have the measurements, this is a straightforward build. You can download the ...