Wooden Warfare

In the news recently, reversals in the conflict in Ukraine involving incursions deep into Russian territory by one-way attack drones. I'm rarely taken seriously in the UK, using as I do foam and timber within a culture more used to sitting on it's ass watching F1 cars built from carbon-fibre racing in an effort to accelerate global warming.

YouTubers in the US tho' often rely on Home Depot to prototype wholly new designs made possible by advances in electric motors. And this combination between modern 'soft' tech and traditional 'hard' ware is being used to advantage in places where conflict is accelerating progress, not least in war: for what seals the success of such drones is combining their use with AI that figures out how best to route them to avoid anti-aircraft fire.

For the drone above is responsible for any number of incursions and is made in what used to be wooden-furniture factories. Short of materials during WW2, the UK turned to wood to build the 400 m.p.h. Mosquito that was made by emigre Italian furniture-makers long established in London's northern suburbs. At the same time, the wooden Hurricane destroyed more of the Luftwaffe than the Spitfire, whilst the wooden-winged German V1 was infinitely more successful than the V2 rocket at a 25th of the cost.

I recently visited a factory that produced bumpers for Bentleys in view of the fact it was closing down. The machines to produce injection-moulded bumpers are half the size of a house and as heavy, and emblematic of the fact that at least in parts of the world not at war we needn't produce anything for ourselves, nor know how to do so.

But the evolutionary biologist Richard Dawkins has recently speculated that technical progress may now be outstripping our ability to adapt to changes that follow, given that prior generations could have expected to live essentially unchanging lives. Aldous Huxley wrote that 20th century citizens were effectively the first to experience speed per se ~ we could be the first to experience the unimaginable speed of change.

Black Ops

I forsake the studio for the car-park around the corner, it being a budget project from the get-go. At eight kilos fitted out with batteries and ESCs to boot, at 85% the thrust to weight ratio should approach unity. In theory that means it should be able to climb vertically and while that might be fun, it's not what it's designed for.

Motoring Tips

Square pegs not fitting round holes, what I've done here is pop a similar-sized dowel on the end of the upper spar and secured with a screw before mounting the motor as seen here.

The towel-rail bracket is a tiny bit larger than the dowel, which allows for the smallest amount of gimbaling under thrust. I convene a power-plant meeting including myself with a variety of hats on, and point out that Saturn Five rockets also had nozzles that were not rigidly fixed.

Nonetheless as we're dealing with a few pounds of thrust rather than eleven million, I elect for a compromise and squirt an ample amount of bathroom silicone into each of the housings.... this will allow just a modicum of play as those mighty motors are spun up at 'T minus 3 seconds'.

Mounting Tensions

I want the axes of each motor aligned with the uppermost spars of each pontoon, and in line with my 'left-over' and 'home-build' ethos my attention turns to surplus towel-rail brackets. These I fasten to the backside of each motor with epoxy that has been hanging around the workshop like a bad smell.

We are helped in all of this by the fact that these motors will power pusher propellers that are actively trying to pin them to the superstructure, as opposed to tractors that are actively trying to pull them apart. The UK's land speed record holder Richard Noble briefly manufactured a light aircraft called the ARV, and the one pilot I knew who flew it told me that once after take-off its propeller separated altogether from the engine.

I realise that Boeing for instance would not borrow bathroom fittings to secure power-plants, but we're rapid (-ish) prototyping here, aren't we? And besides, I'm told that Lotus themselves ~ who build in composites ~ actually glue their own motor mounts to the body with epoxy. And what's good enough for them...

Meanwhile these babies are in the kitchen oven where the glue will set quicker, and afterward we'll use self-tapping screws as part of a 'belt and braces' approach to life.

Lift, Off.

Here we can see the arrangement of the lift motors, pitched 11.25" off the back end of each upper spar and with the same clearance forward. I like to think that these are to be optional, like the preference for two or else four wheel drive on your choice of car.

Thinking about the pros and cons, bear in mind how we saw yesterday that the stock two-motored cat weighs in at 8.00kg... well these four babies along with the required equipment (including batteries) add a further 3.20kg, which is a forty percent uplift.

That's a lot of extra cost and weight for the facility to fly your craft over to the water, and subsequently to facilitate shallow (or next to no) water operation ~ but then that's horses for courses, isn't it?

Meanwhile if you're asking yourself whether these lift motors can earn their keep, well at 75% grunt they're lifting about 3.20kg in themselves, or four times their own weight.

You can see though how vectoring propellers hit the spot, by reducing the additional weight by fifty percent... although not quite, in view of the added weight of all that is required for vectoring.

It is worth noting that among personal eVTOLs, nearly all have fixed motors viz. Hexa, Pivotal, Jetson and Ehang whilst flying taxis are practically all vectoring types. What it tells you is that where vast budgets are available from corporate investors, developers have taken the plunge and taken the added burden of vectoring upon themselves in the hope of flying further and faster than the competition.

That's not something we need worry about, which is the joy of building boats instead.

(And the props will be removed now, though I'll mark each spot for future reference.)

When I'm 6.4

Been so many cuts and splices that I go for a complete rebuild and take the oppo to go down the Imperial measure route, so that the three flotation panels are each one foot by three. The upper spars are extended to the full eight feet and split 3:3:2 twixt front and back either side of said panels. The lower spars therefore remain five feet apiece and support hydroskis of eight and a half feet in length, so that their trailing edges provide cover for the propeller tips that will be mounted to align with those upper spars, which are extended so that:

    (a)    there is room for four 22" props for hover, fore and aft of flotation panels.

    (b)    there is accommodation for a tailplane and fins, should they be required.

The machine will be painted black, because the best quality tins of spray paint I have left over in the workshop happen to be that colour. Also, should we go down a carbon fibre route then we'll know how it will look in advance I guess?

The chassis as seen weighs 6.40 kilos and each power-pack (viz. battery, ESC, motor and propeller) amounts to 0.80 kilos, so that the boat with a pair of electrical motors is just eight kilos in all.

This means as a rule of thumb the craft weighs around one kilo or 2.20 pounds per foot of length, whilst the last time I looked power-boats weighed a hundred kilos per metre or 67.69 pounds per foot.

Losing Traction

Farmers in the mid-West up in arms with having machinery lie unemployed for sake of a chip to fix one or other component, to the extent they're ordering copy-cats online from Eastern Europe to avoid two-hundred mile round trips to dealerships. Raised in an age when you could fix points with a nail-file or sub fan-belts with stockings, it is hard for me not to agree with the view that complex systems are prone to collapse.