Elevator Pitch

Time to start setting our ducks in a row, and as I'm back early from the day job it's into the workshop for some C of G calculations. And afterward it's a bottle of red, cheese straws and salami during write-up: aerodynamics is fun if approached from the right angle.

Accordingly I park the 'Black Ops' drone on a length of tubing, which shows that the centre of gravity is around 7" aft of the forward bulkhead thus:

This I knew from prior builds, the excess weight of those booms and the skis they support pitching the prow down. I'm reluctant to foreshorten these however as they are going to be necessary when it comes to tackling rougher sea-states. Here tho' is what happens when we add the power-bank at the rear:

This pitches the C of G nicely central, the motors acting as a counterbalance. We've much practise at counterbalancing in Europe, for when we built the cathedrals some thousand years ago the bells that weighed several tons apiece had to be able to be swung by someone like Quasimodo. If you don't know who he is, incidentally, in the words of Will Young I think you better leave right now.*

What follows from this is the fact that the lift-motors being equidistant from that C of G, they ought to have no material effect on shifting it. It in turn means I can use tins of tuna instead, as I'm running out of motors here:

This is what fellow aerodynamics refer to as either the sweet spot, or dog's bollocks, because it means that if it launches into the air off the crest of a wave it is literally disinclined to pitch either downwards or upwards.

We're having to design for flight as well as planing on water here too, and note that for hovering flight from land to sea, what we want for a quadcopter is the mass of the craft to be pitched at the centre of all four corners of lift... and fuck, if it isn't here?

The bad news ~ and there's always bad news in life to counterbalance the good ~ is that for the 'lift' prototype we are going to need ballast at the rear to maintain this status quo. This however is standard MO for aircraft, so for instance if you remove a radar from the nose of a fighter jet you may need to fit a lump of lead in there in order to sustain the trim.

Broadly speaking aircraft designers are years ahead of marine architects, who have mainly to figure out what goes where whilst keeping the ship on an even keel. This is why fast boat design has become a bit shit in the 21st century, for whereas the Italians used to pitch motors centrally in their superior power-boats, now it's about hanging heavy-weight outboards on the back-end and having to build longer, heavier hulls to suit.

US excels at big and Japan small, whilst as ever the Brits are born to compromise. 

* Ed. Don't, it's the wine talking. Bear in mind The West Wing was powered by cocaine.

Vertical Flight Society

Renew my subs in order to keep my hat in the vertical ring: Sikorsky's a homburg, mine a flat cap in tribute to legendary local steam-head Fred Dibnah.

What the Hex?

Set the airframes out to dry over the weekend and was discombobulated by a knock at the door from the local PD who'd reports of witchcraft from more than one of the neighbours. Eventually they agreed they could remain there so long as I didn't plan to dance around them naked again.

The black drone is to be fitted with lift-motors to raise it into hover, and the grey solely with pusher-propellers to evaluate its ability to plane on water.

Not happening in a hurry unless the men in black appear, though subsequently each config will be combined toward self-launch and skimming flight clear of any surface.

Spot the Difference: TELEDRONE BOX

I realise in the small hours that sub-consciously all I have done is to take a design I optimised by trial-and-error, and made it the basis for a boat instead.

Adolf Hitler and Margaret Thatcher are said to have been people who went to bed wondering how to invade Denmark or the Falklands, and wake with the solution.

On a happier note Paul McCartney ~ who lived not far from here ~ is said to have woken one day with 'Yesterday;' fully-formed, to the extent he could not believe it did not already exist and had to be persuaded otherwise.

Ed. Yesterday his previous drones seemed far away, now it looks as though they're here to stay.

Spot-the-Difference: LIFT + CRUISE

I'd challenge anyone to guess, but one of these is the original and the other me-too configurations of LIFT + CRUISE ~ to the best of my knowledge.

Earliest to the table and resident of fondly-remembered Mountain View in California is Wisk. This venture is a collab between Boeing ~ who know an aircraft when they see it ~ and one of the Google twins whose attention was drawn many years ago to the prospects of eVTOL machines.

They set a trend that every other air taxi project has followed since, in that it began life as an array of lift-motors that was soon superseded by prototypes with a pair of wings and lift-motors that could be vectored so as to provide forward thrust. Those connected with conventional aviation knew that pure lift from anything less than the sizeable dimensions of a helicopter rotor was both expensive and inefficient, though like teenagers the newer entrants to the field had to learn the hard way.

There was considerable argy-bargy when Archer (at left) appeared to have copied the design, not least because many of its employees had been poached from the prior effort. Again there is nothing new under the sun, as Fokker did the same to the UK manufacturer Handley Page when they turned the Herald into the decidedly successful Friendship.

They have however kissed and made up, which leaves the only UK entrant standing in the form of Vertical Aerospace (centre), a recipient of the bulk of taxpayer funds in this field despite its founder having coined it in our broken energy market... and you thought the Russians invented oligarchs?

Ed. what the author is trying to say is that he wishes the project every success, and is fully prepared to eat humble pie on livestream as and when you meet in court.

Limbache (stet)

I chance upon a video produced in Ukraine by a man who does engines and his wife who speaks English, who together get to tear down the engine from a Shahed 136, notorious in its use both there and in the Gulf; to the extent it has been reproduced by the US on the basis that 'If you can't beat them...'.

Perhaps not surprisingly given the performance of their engines in WW2, the engine is a Limbach 550 produced in Germany, but with parts like bearings originating in places as far away as South Korea and Japan. A truly international effort, parts that adapt it to fitment in the drone are sourced from China, India and even Europe.

The vloggers point out that these parts vary greatly in quality, and assembled in a way that suggests whoever does so has little or no knowledge of how the engines work.

The wooden propeller is around two feet in diameter to suit the RPM of the motor, which is set to the maximum of around 7,500 rpm. An electrical generator is fitted, although as the ignition is self-sustaining by use of a magneto, this is presumably to keep those batteries powering the electronic components responsible for navigation and target acquisition.

Limbach themselves do not advertise a price, but other websites do so for drones in particular and charge between $17,500 and $20,000. The manufacturer is reticent and advertise the two-stroke engines for sport, recreational and experimental use... adding the following rider:

If you would like to implement projects in the fields of aerial observation, surveying, aerial photography, telecommunications or environmental protection, simply contact us – we can present interesting solutions jointly with you and our partners.

Whether or not agents in either Iran or Russia contacted them to say "We're minded to use your engines to take out random targets at a distance and would very much like to work together on a solution to our mutual satisfaction. Needing thousands."

The engine in the video has its serial number milled out to conceal its origin, though increasingly it would appear the units ~ given numbers required and PR fallout for its manufacturer ~ are now reproduced in home-grown versions to an altogether lower standard, as might be expected in the circs.

They are in all fairness only expected to last an hour at most, and I doubt anyone is returning the goods with the original packaging should they fall short of this (or any other) target?

Black Sabbath

Six lengths of stripwood transformed by the addition of a tile-backer centre-section and what's left of the uPVC skirting used as skis; these are more flexible than the wood on the water-borne prototype, as this airborne version is ideally a little lighter.

Accordingly it features 18mm square-section booms as against 21mm beside those lighter skis, and as a result this chassis weighs in at 10.50 pounds instead of 13.00.

I've gone for black in this case as it's what you'd expect of an experimental quad, in view of the fact the pusher-props and motors at the rear will be omitted for testing. I also had a leftover can of matt black, though it expired long before it was empty ~  something old cans of paint are prone to do and generally when hardware stores are closed, just to piss you off a little more.

I've one more centre-section to dispose of that will feature vectoring rear props, so that it needs only four motors in total. It will though be destined for a museum of our choosing rather than be developed at this stage, as separate lift and cruise motors are easier to implement.

These need neither actuator nor flight-controller, as lift-props sub for collective and pushers an element of conventional cyclic in driving things forward.

Ed. the post's title stems from the fact it is (a) black and (b) Sunday.