Sunday, July 25, 2021

CGI Fridays

Appears I'm not the only one to have considered the benefits of propellers pitched vertically above and below accommodation, a proposition I've long supported and for which I've produced any number of iterations. I've also been told that I need to up the quality of the renders and feature them in operational visualisations like the one on the left above, so I figured I'd take a closer look at the NeXtuas 'iFly'.

The relevant patent filed back in 2017 does indeed relate to the configuration, though whether it was envisaged back then as a means of transporting people I could not be sure. It may appear in the text but is omitted from the abstract and diagrams, where it would be were it considered the 'killer app'... no pun intended.

The video evidence of it ever having flown as intended is scant, the screen-capture showing it flying with the original skids, which I'd guess you'd have to retain. So many of these eVTOL projects exist only in pixellate form that it's worth the due diligence as investment is generally being sought, but this one does at least have a basis in fact.

As someone who's been there ~ and is still there ~ I would suggest that more tangible evidence is required before either VCs or SPACs are petitioned.

But that didn't ever do the likes of Vertical Aerospace any harm, did it? What they had instead however were financial friends in London, a billionaire owner and a matching investment from the UK government which rarely places it beyond a safe bet ~ and via Rolls Royce if required, which it bailed in '71 and looks set to do again.

Tuesday, July 20, 2021

Karman Ghia

Chance upon the TV news at around the time Jeff Bezos is being launched into space from Texas, and although they cover the launch they don't stick around for a moment more of the albeit short-lived flight in what looks unnervingly like a super-sized dildo. Which would suit a strap-line which reads, "We fucked planet Earth, where's yours?"

In fact Will Lighthorn (sic) who heads up the UK's space endeavour ~ a vanity project if ever there was one ~ says the billionaires are doing us a favour by dumping whatever needs to be dumped in space now that Earth is, like Will himself, full of shit.

This is madness, and something you'd hesitate to call civilisation: the remedy for shit on our door-step being to look for another planet to leave more on... or leave morons?

But the difference between the numbers interested in such ventures now, as against in 1969 when kids stayed up all night, is telling. Literally blink, and you've missed it... which is consolation if nothing else for anyone working in a warehouse instead.

(The views expressed here are not those of the author, but of the author after a glass of Pinot Grigio. He admires every billionaire's efforts to launch humanity into space, or indeed to offer the author a job in his warehouse if things get desperate.)

Monday, July 19, 2021

Epic Fail

I scale up to the 32" cubed that would be required to accommodate the propellers of the same length (real, Jim, and not as we know fascia-board) and can see straightway that the requisite stiffness is going to be more bother than it's worth. Fortunately this exercise has only cost me a couple of quid for pop-rivets, and as Edison said, I didn't fail a thousand times, but discovered a thousand ways it wouldn't work. Answers deliberations of recent days, to the extent underslung propellers remain the way to go.

Sunday, July 18, 2021

Cogito Ergonomics

Looking at the common airframe used in both the underfoot quad posted July 9th of this year and the overhead quad posted two days ago on July 16th, the reason that the latter has the more compact footprint is clear from the diagram above. It includes 32" propellers and a 12" centre-section, just large enough to fit the mannekin's seat.

There's not much space there for dangling your feet, unless you want them sliced like salami. Put the quadcopter overhead and the problem is solved, however. Remarkably the weight of each airframe (the single-decker and the cubic or double-decker) turns out to be the same at 8.40 kilos, but then the former has a 42" square footprint and the latter only 25".

Nonetheless I still figure that upping the footprint of the cubic 'copter to 34" square and using the preferred 1/16th gauge alloy section that I can still bring the airframe in at around 15 kilos, which allows for two battery packs and the motors and ESCs and is still under the regulation 25kg for a regular drone... but without the seat and dummy.

There would though be an argument for getting it flying sans payload, and afterward registering to as a large remote-control model (of which some in the UK exceed 100 kilos under the same scheme). The great benefit of the design however is modularity, in that the drone used in the single-decker version is the self-same that can be fitted up top.

In practical terms this means that the quadcopter can be flight-tested independently and afterward supplemented by either the seat and dummy (albeit with the restricted leg-room), or else raised into the overhead within the outline of the double-decker. At the end of the day therefore it would be for prospective operators to decide whether those propellers are preferred overhead at the cost of the extra weight.

Certainly from the point of view of safety that is the better place for them to be, while at the same time providing for a more compact footprint altogether. What is intriguing about the outline pictured here though is that it would still accommodate a passenger stood within a booth instead of seated, which again is a matter of personal preference. (It also begs the question as to where to fit avionics, though apparently flight-control computers can be operated inverted, so that they might be fixed beneath the base).

It's a dilemma with designing electrical air vehicles though: with helicopters there was certainty from the outset, with their main-rotors above and tail-rotors at the rear.

Now though we are cast into confusion, and Mourning Becomes Electra. 

Saturday, July 17, 2021

Carbon Fever

Carbon-fibre tubing has its advantages in constructing drones. It certainly goes some way to explain the price-rise once you shift from the injection-moulded plastics used in domestic quadcopters toward commercial types dedicated to surveys or to filming for the likes of the BBC.

When it comes to using it ~ as I clearly could ~ for personal air vehicles however, it is much like the choice between buying a Maclaren instead of a Mustang (or in my case a seventeen year old Suzuki Jimny).

For your benefit, here's a rough formula I use to remind myself of its properties:

3 : 7 : 21

This is because compared to (non-aviation) aluminium tubing it is three times lighter, seven times stronger, but twenty-one times more expensive... even given the recent hike in global non-ferrous metal prices.

You could argue that because of that superior strength I could reduce the dimensions of the various struts involved (and therefore the cost) but to some extent that process is self-defeating. For as Brunel discovered whilst building London railway bridges using timber, doubling the depth of material involved alone quadrupled its strength.

In fact it was while I was flying for an airline in Germany, with leisure time invariably spent designing and building, that I was first introduced to a length of carbon-fibre tubing at a light-industrial concern of the kind that the country has in abundance.

I was astonished... light as a feather and unbendable despite being only wafer-thin. It is though useless for the rapid-prototyping on which until now I have been engaged, in which I've used and re-used the same sections of sheet and tubular alloy constantly.

It will happen at some stage, however, if only because carbon-fibre and my airframes were meant for each other:

                                            All I want is a room somewhere

                                            Far away from the cold night air

                                            With one enormous chair

                                            In a carbon-fibre airframe

                                            Oh, wouldn’t it be loverly?

Friday, July 16, 2021

Cubic Copter

With the few props left from the presentation I make a mock-up for my own benefit and it's a testament to the methodology that it's so simple. Specially pleased with the blades, cut from fascia-board that would otherwise be wasted on a conservatory. As helicopters go it looks a lot of fun (of the kind which seems to have got lost along the way). If the weight is kept in check it's a safer place for the propellers, and may yet be the one I choose to prototype at full-size.


With a hundred people viewing the online sales pitch it turned out I was joint fifth on the day, having secured the votes of 6.30 of them. That's statistics for you, but as was pointed out by the organisers ( though many applicants are called few are chosen. Was also a good practise for whenever it might have to be done again, which thankfully might be in person, which is altogether easier and more entertaining.