I have just 3d printed a Footy. The website linked to details of a cassette system for the servos but also used something called a Stollery Power Arm. This is a curved wire extension to the servo arm with a sliding fitting to which the sheet attaches. Arm fully forward, slider at front, sail all out, arm fully back, slider moves close to the servo and sheets in. The system seems to rely on a curved wire but unfortunately the attached pictures are a bit indistinct and I have not been able to find any more detailed explanation of how to set the arm up. I suspect that the curve is critical. Probably T&E.
Anyone know of any better source, preferably with diagrams?
The Footy was printed as proof of concept mainly, but I would like to complete it as a fun project and already have most of the bits needed as 'left overs '.