Worth a pause in the proceedings to evaluate where we've come from, and where we are headed... what pilots call a progress log, or plog.
First and foremost, and as Robert Burns would say of the best-laid plans of mice or men, the airframe would not fit through the workshop door... although as I point out, better to be stuck outside the door than inside. And this also points to the potential benefit of an airframe that can be readily dismantled.
And so it may, ultimately. The upper quad has a central recess that allows it to rest securely on top of the phone-box (the dome you see here being cosmetic and merely a means of protecting the avionics). Meanwhile the lower quad has a central void that allows it to slide into position around the base of the phone-box, which really is the base as it appears here. In turn this transfers the static load of airframe and payload directly to the ground, allowing for a lighter build altogether.
Bolted afterward to the sides of each quad, those X-braces that you see secure the whole assembly. In theory therefore, once removed the airframe can be reduced to three modules able to negotiate the narrowest of passages. This counts in the long run, Hexa's single-seat eVTOL for example requiring not inconsiderable machinations in order to move it around (see below).
Failure of the previous prototype under flight-test was due to the undue flexibility of its airframe, and thus this one has been redesigned to be shorter, stiffer and lighter: It therefore forms the basis of whatever follows it going forward. At the same time its skids are easily modified so that the airframe could support octocopters instead of quads ~ that's sixteen motors in place of eight for those of a nervous disposition.
This counts for eVTOLs, incidentally. The (eight-motored) Vertical Aerospace prototype was recently destroyed following failure of two motors, or 25% of its installed power. To contrast that with conventional aviation, British Airways once flew a 747 to the UK from Los Angeles following 25% (i.e. one) of its engines failing shortly after take-off.
Accordingly for the purposes of maximum rigidity at this stage, all three modules of our 'DRONE are riveted together.
Finally, what happened to the four-pronged layout used so frequently in the past as against this more conventional arrangement with 'panniers' either side, not dissimilar from H-format racing drones albeit with the 'H' rotated through ninety degrees? Well the benefit of building and rebuilding at various scales is that strengths, weaknesses and practicalities of designs emerge that might not otherwise. You cannot beat lived experience, which is why YouTube is awash with 'ten worst' videos.
And this design from my own point of view ticks all of the right boxes, not least the ergonomics of flying an upright operator. What you see forms the front of the box will eventually hinged down to form a ramp, incidentally, so as to allow ingress and egress whilst still forming a shear-web to enhance the rigidity of the whole in flight. Aircraft are ever a delicate balance betwixt undue rigidity and undue flexibility and like all of us, are essentially somewhere on the spectrum.
A further reason too for flying this prototype as a 'whole' is that the flight computer fixed in the dome of the phone-box is wired to the lower quad in order to operate as an X-8 configuration. Ultimately I want that control duplexed so as to accommodate rapid assembly and disassembly, in order that we've an eVTOL that can be deployed by a single operator... and I don't see any others out there that fit that particular bill. Yes, Jetson's fabulous aircraft (like Blackfly's) can be wheeled out the garage, but I don't see the component part of either being racked on its walls any time soon.
Should this prove to fly ~ and I want it to fly better than any other at least in terms of outright manoeuvrability ~ then we'll scale up to full-size mannekin with motors that are currently surplus to requirements and somewhat larger, along with 27" propellers in place of 22". And then if that can be satisfactorily demonstrated ~ which should get us all excited ~ we'll up the power again along with the payload until such times as I'm up there myself.
Should it not fly to spec though, the towel passing your head is mine being thrown in.
