I did think about that Eddie, though it would be tricky. I'm printing with very low infill to keep the weight down, so most of the strength comes from the 3mm stainless steel capillary tube running down the thickest part of the airfoil section and through which I thread the wire of the flails. Additional prop blades on wouldn't have that stiffening, so they'd be a bit vulnerable. All hypothetical for now though; when I fitted up that super-optimised airfoil with the wire and weights and tested it, everything got very bumpy and unstable, even though the flail itself was well balanced. Possible that I increased the pitch too far (it's effectively quite a low Reynolds Number, so couldn't rely on the NACA graphs) and unwittingly set up some vortex-shedding induced vibration that's being amplified by the wire & weights
. Too many complex forces at work I think!
Anyway, need. to. step. away. from. this. problem. for now - otherwise I will get too carried away and run out of time for all the other things I need to get finished before AWS61. So for now I'm going to stick with my initial basic airfoil prop (only a couple of grams of downforce but runs really smoothly) and instead concentrate on losing a few grams from the body so I can fit a 3s lipo, instead of the 2s. Did some tests with 3s yesterday and that really makes a heck of a difference, both to the speed of spin-up and to the driveability at full flail-force.
Meanwhile, the second half of the SpinTwins is progressing nicely. After half an hour with a cheap prop-balancer, a file, and a lot of luck, I managed to get the blade really well balanced, so there's very little vibration. The tiny 1304 brushless motor had quite a long shaft, which was only threaded half the way down, so I extended the thread all the way with an M4 die and shortened the shaft.
First attempt at a foot was a bit off - need to shorten the vertical bit of the dog-leg, then the blade should be nearer the horizontal.
I was going to call the 'Spin Twins' bot-lets 'Tuffers' and 'Swannee', after England's erstwhile spin-bowling attack - but since I suspect cricketing references will be lost on some roboteers, we're leaning towards "X-Axis" for the horizontal spinner and "Y-Axis" for the vert. Might have to call the resultant cluster "The Cartesian CoordinAnts" instead...