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 '.

I used this cassette for years when I was footy-ing. The curve itself isn’t mega critical (I have bent the wire around my knee in the past!) but the small wire ring with the sheet attached needs to move up and down the curve easily so a constant bend is essential otherwise it ‘sticks’ at a position which is bound to be wrong!

I also trialed making the curve from softer wire so the biggest rigs eased out when it flexed in gusts to avoid over straining the smaller (lighter) servos. I can send photos when I’m next up in the garage..

Found this plan on the Guildford site for the Bug3 footy with details of the power arm

https://guildfordmyc.co.uk/wp-content/uploads/2015/02/BUG3_Construction_Notes.pdf

It’s used on the Bottle boat too (different gauge of wire though) so that might be worth searching for..

Thanks both.