Tuning Up

Sign off purchase of tins of tuna with which to sub for motors as we progress toward shakedown tests involving transport, besides PR shots for the website.

As a matter of fact these are almost indistinguishable from the real thing once they are sprayed up, and make for a tasty snack for your teams afterward.

Motors are mounted (from forward left, clockwise) to turn in directions CW, CCW, CW and CCW.

Or as per photograph: Soy & Ginger, Lemon & Thyme, Red Hot Chilli, Soy & Ginger.

Back to the Future #25

With the decision made on transportation viz. directly mounting at the rear of a 4x4 in preference to use of a flatbed trailer, a hard-mount is affixed to the underside of the cat in order to facilitate the operation. Note the addition of the struts previously posted, which serve to stiffen the rear end of the hydro-skis, which as you will recall are in this case made of lengths of extruded uPVC ordinarily used for skirting board.

Weighty Matters

Big day because I've to decide whether or not to give the go-ahead to the second prototype that is dedicated to hover. A while since we did this, but it's back on the scales for one of the four power-packs comprising ESC, motor and battery-pack. This comes in at a rounded .75 kilos, of which .35 belongs to the motor itself.

Meantimes the boat weighs in at a rounded 5.00 kilos, so we're looking at an all-up weight of around 8.00 kilos or about eighteen pounds... not bad for an eight-footer.

Turning to the tables provided by T-motor themselves ~ invariably optimistic ~ the section on the 280kV motor appears below. This is the slowest variant of the motor and it produces 280 r.p.m. per volt, whilst the alternatives provide over 400 r.p.m.

This requires the largest recommended prop turning slower, which is more efficient at the cost of needing more torque and overheating the motor... in the table every combo lists a working temperature except this one, which simply says 'HOT'.

Nonetheless we'll be burning these babies in a do-or-die effort to get this thing off the ground, even if it means throwing more volts into the ring. Indeed the figs here relate to 24V packs and we've only 22V, so there's capacity in hand to up the stakes with bigger battery-packs (whilst I'm loathe as ever to part with the cash).

Accordingly pick up your tables and we'll go through them together, if I could ask Gromit to assist please with the laser-pointer?

First off, my friends at Axis Aerospace recommend the motors run around 65% to provide room for differential thrust in hover. Nonetheless in ground-effect there's an element of stability anyway, as motors nearest the ground during any tilt provide the greater thrust and essentially correct the situation... I like to think.

As race-director on the day however I'll mandate use of 75%, for which the figure in the table is a mighty 3300 grams of thrust. Dividing by 24 and times 22 (as life is linear) we still clear 3025 grams. Thus with four motors we're looking at twelve kilos of lift for eight kilos of boat... in fact even at 60% we should have lift-off, Houston.

We're therefore cooking on gas and all eyes turn to me (both cats!) as I green-light the project, and the room erupts in whoops and hollers that I pre-recorded on the laptop for the occasion. The question for the next bored meeting (stet) is whether I ask my electrical engineering friend to wire the motors for a NASA-style static thrust test... or go straight to Axis and get them wired for flight as well as sound?

I like 'Plan A' as the entertainment value is through the roof, not least because of the pond there too where we could conduct static flotation tests. As doughnuts are finished off and the last of the coffee is drained, however, our moon-shot must turn its attention to how we get the cat from A to B in either case.

It ain't going to be easy, and if any one of you is feeling the need to drop out at this stage then see me afterwards and I'll knee you in the groin and wish you well.

Struttin' Our Stuff

Realise the second prototype (to be dedicated to hover) has uPVC skids that look too flexible altogether at the back-end, unlike their timber counterparts on #001.

They look to need stiffening with struts, and at first I was afraid ~ I was petrified ~ but now I hold my head up high recalling how the prototype Hawker Hurricane and Me-109 needed struts at the tail-end too!

To do this I've a couple of old fibreglass tubes which I've cut down to 350mm, and afterward squirted filler in either end to provide purchase for a pair of wood-screws.

One thing I've learned as I've got older is firstly always to use sun-screen, but also to avoid nuts and bolts wherever a simple screw will do.

The problem with droopy members is they'll sag in the hover, springing upward if submerged.

Nonetheless a search on that term at sharing site YouTube has put me in touch with a Dr. Nora Hayes, who says she can fix anything for just $300 per hour.

Great... and who knew an MD would be interested in maritime drones too!

If anyone is interested in an annual strut-meet where surviving Hurricanes and Me 109s are flown in for me to try out while owners get to sit in my drone, contact me. 

Proto Typing

Not all plain sailing, as I hoped to build a cat round this bod to hang in a small boat collection somewhere; but turns out the knockdown paint I bought for a pound a can is not all it seems. Far from the matt 'NATO Green' it appears on the tin, it does so as 'Kermit the Frog' gloss.

Clue was probably the tin featuring a ride-on lawnmower, of dubious use to NATO.* 

Nonetheless it was an excuse to consign it to the bin, not really liking its proportions and having altered them for each prototype.

It did impress tho' by resisting all efforts to dismantle it for disposal: centuries from now it will be unearthed by robots, one asking what it was and another replying some loser's flying boat?

As Basil Fawlty said, however... Well that's cost me, hasn't it?

* Currently the UK does provide these ride-on lawnmowers in support of its allies.

Beasted

I'm loving this race down the Californian coast between the home of Mr. Beast and an unnamed restaurant, and while I don't have a reservation I do have some that relate to taking a Jetson instead of the car?

Firstly, as is apparent from the arrival there are few restaurants I know in the UK willing to clear the car-park of revenue-paying customers and barricade the public (beside upgrading the home insurance) in order to facilitate one of them landing. 

What happens subsequent (at least where I live) is the diner would spend less time worrying about Mr. Beast, and more about whether his ride has been stolen or vandalised ~ intentionally or unintentionally by all those selfies. The restaurant will though have someone keep an eye on it, likely soon a robot, as happens already at those restaurants that charge sufficient to attract only the wealthy?

The sad fact is, most of the Michelin-starred restaurants that people who can afford a Jetson are likely to visit are in places like London, which were designed for Roman carriages. You do get the odd one in the nearby countryside where the people who complain about helicopters live: the reason the one between Heathrow and Gatwick was shut down.

Furthermore, the people travelling to them ~ as I did once ~ will be doing so from Wimbledon, where they've room for tennis courts but neither room for helipads nor the council's permission to use them ~ and that's dead in the water, even if you are not after flying the cliff-line.

For the problem plaguing every form of personal aerial transport has been just this ~ the last mile ~ and only recently the VFS forum has been alive to the fact that the longer it takes to travel to a 'vertiport' to take a flying taxi, the less people will be inclined to use one at any cost.

And then as we pursue actions that ensure we'll be loathed by adherents of one sort of religious or national affiliation or another, there is the question of security.

Few of us need stand in line to get frisked prior driving to the restaurant, but the attraction of bringing down high-value targets like flying taxis (Concorde withdrawn this way, no matter the excuse) might spoil the evening if the handbags' contents have to be decanted from the get-go.

Which brings us to the Jetson, which is a DIY kamikaze pilot's dream and able to be steered at whichever high-class target with high explosive aboard and few fears of interception. And as often as not, the people inclined to do that will be the ones with petrodollars to pay for it... as they generally are at the best London restaurants.

And so we love the dream, we really do, and I'd rather be in a Jetson flying down the coast to meet Mr. Beast for eggs Benedict instead of sitting here in bed eating toast and marmalade with my stuffed Paddington bear.

But you and I know that ~ like fucking Sabrina Carpenter ~ it ain't going to happen.

Ed. note to lawyers, that's 'fucking Sabrina' active and not descriptive... and if Sabrina's reading, the author says he's willing to travel.

YASA Dabba Doo

Jet engines are notoriously thirsty at ground-level and I used to marvel at how the APU (which provides ground services to an airliner prior start) required a tenth of the fuel in the cruise that it did prior departure.

Accordingly this motor will allow airliners to taxi prior take-off or after landing with engines shut down. It was an issue at Heathrow ~ then the world's busiest ~ where we'd sit in line for upto forty minutes prior departure.

That's the good news. The maybe-less-so is that the Oxford academic who invented these axial-flow motors sold the company to Mercedes, not least because these things can turn out 1,000HP quite happily.

Ed. Bear in mind Germany does invest in manufacture and has the funds to do so, whereas in the UK we prefer property or gambling.