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.

Iron Man Challenge

Wondering what proportion of the weight of a boat is generally afforded the engine, I draw up some scratch stats based on a UK powerboat in the shape of the Iron 647. 

Though I'd be interested in knowing what proportion of the empty weight of airliners is occupied by the engines, it's not easy knowing because manufacturers rarely split the engines from the airframe in the specs.

Interested to see that in either case (with the cat confined to a pair of cruise motors) it's about a quarter of the gross. Batteries are included in the electrical USV, although these would be unlikely to last much more than twenty minutes am guessing and so I've discarded any reference to range or endurance that as yet are unknown. That said am unsure whether these were listed for the 647 either, the target customer likely to be a circumnavigator of say the Isle of Wight on a sunny day.

Speed I've pro-rata'd from the length of the craft, or the time to cover its own length. In the second case, again, it's as much an aspiration as an aspirated record.

The takeaway however is the fact that even with the avionics thrown in, the cat is a comfortable hundred times cheaper than the powerboat.

I discussed this with the man who heads the sales of BAE's maritime division, pointing out that the RIBs they use as a platform cost an arm and a leg. His point though being that given the extraordinary cost of the sensors on board (I recall that some third of a million was quoted for just one of them) that the cost of the platform was a bagatelle.

To me that says something about the cost of those sensors in the scheme of things. In the modern world ~ take satellites or drones for instance ~ most things trend towards a multiplicity of much smaller and cheaper units of production altogether.

With its 'quicksink' guided bomb, the US has demonstrated that even carriers are now sitting ducks that can be eliminated by munitions not one hundred times cheaper, but several millions times so.

Interesting times, but for now BAE have an expensive pension fund to maintain at war readiness.

As things stand though, their takeaway is that their's works and as yet mine doesn't...

Digital Commoner

Am not one to obsess over stats, but feedback from the Digital Commons is of special interest to one graduate of geography like myself, as it makes for a snapshot of a kind that prior the internet would barely have been possible.

Looking then at a variety of papers and bearing in mind some have had a head start, it is interesting to note that pictures are still worth a thousand words. Of the half-dozen airframes I may have circulated by which means we might be elevated by super-sized drones, the one appearing here has proven by far the most popular... and the only one downloaded by commercial helicopter (and bizarrely, access platform) manufacturers.

The runner-up meanwhile is a paper describing how people we might recognise might also be used as a means of secure access to computer systems. Yes, we all recognise Ronald McDonald, but would I recognise your grandmother?

The spread around the world reflects our common cultures too. For instance in the US two downloads in San Fran and Mountain View relate to the means of human carriage, whilst at Wharton on the East Coast it's the secure means of access. In the UK there are three dozen downloads local to me, tho' just one (on secure access) in Whitehall... the heart of UK government and its military headquarters.

In Europe one paper that springs out is a personal favourite (but no-one else's) in the form of a self-tilting wing to expand the range of drones. And downloaded where? At Lviv, to the rear of Ukraine's war-zone. And Tel Aviv, the heart of Israel's research into means of war or self-defence depending on your viewpoint? The human-flying drone.

In China, a mix of downloads split between the drone and the secure access system.

In Singapore, however, a royal flush in the form of interest in self-tilting wings, drones for human carriage, secure means of access and the latter specifically intended to sub for conventional numeric key-pads.

Finally from Jakarta exclusive interest in drones in the shape of the above, but also a lone download on what I called a virtual quadcopter... which basically describes how props running in the same direction can be overlapped like a Venn diagram so as to make airframes altogether more compact without nearly the same loss of thrust as that experienced by the common co-axial system.

Post a paper yourself and see how what you consider the ugliest of ducklings amongst your work may be to others a beautiful swan.

(Ed. what bollocks this guy writes...)

Mind the Gap

If land vehicles are excluded from the GvK diagram, then a large triangular "gap" appears, spanned by merchant ship, destroyer, and commercial airplane, with airship being the lone inhabitant of the gap. After the GvK diagram became more widely known to marine engineers, a large number of designs were promoted to fill the gap, such as planing boats, hydrofoils, hovercraft and ground-effect vehicles, without success.^[5]

Extract from Wikipedia's entry on the Karman-Gabrielli graph that compares efficiency of different types of transport versus their speed. The triangle described is bounded by jet airliners (very fast but relatively inefficient) through merchant ships (very slow but very efficient) to destroyers (altogether faster than the previous at considerable costs in terms of efficiency.

The 'sweet spot' central to the triangle is inhabited by the airship, which shares the efficiency of the merchant ship whilst encroaching upon the higher speeds. As noted in the entry, the only other means of travel that combines this speed and efficiency is those maritime craft that largely get out of the water.

Hydrofoils meet this criteria, but have largely fallen from favour because of damage to which they are prone by flotsam and jetsam. The tide is turning though with electrical powered hydrofoils, whose re-amplified efficiencies are making the damage issue the more sustainable.