Screwed

I've limited resources in terms of time, energy and enthusiasm (beside cash) and so the choice of how to rig the frame for testing on water is not to be pooh-poohed... I leave pooh-poohing to the water utilities here in the UK.

There is ever a balance in prototyping between ambition and overreach, as often as not the simpler solutions proving the better pathway to follow in order to provide for a proof-of-concept; the concept here being that many boats are better off T-shaped.

There are six reasons for mounting contra-rotating props at the rear of the boat:

(a)    as with torpedoes it is the best guarantee of proceeding in a straight line

(b)    it eliminates the need for a separate rudder surface

(c)    it counterbalances the nose-down pitch that we've seen at rest in water

(d)    it allows in due time for a seat up front in potential crewed versions

(e)    it is easily vectored in order to adjust trim on the plane

(f)    I love the smell of turbines in the morning

I shall be using two means of fixing the motors, each of which appeared among the annals here somewhere or other. The forward-facing motor will be bolted directly to the cross-bar, a better name for which I've yet to come up with and which may yet go to Survey Monkey (with the prize being a monkey).

The rear-facing is more of a push-fit, which suits a pusher-propeller: to the rear of the motor I have glued a wardrobe support-bracket, and this slips over a wooden 'boss' or dowel where it is secured with oodles of adhesive and a grub-screw.

Note to self: never fly in an airliner whose jet-engines are fitted by these means.

It's beginning to look not so much a lot like Christmas, as something fairly fast?

Sweet Gene Willson

Who else to have been entrusted with the safe return of England's 'Lionesses' but a national treasure in his own right?

Blue Robotics

Meantimes back at the scale I'd prefer to inhabit ~ not least because of its potential ~ the Blue Robotics story is of interest. Guy in LA trashes a surfboard and decides, as you do, to try to sail it to Hawaii under solar power alone. Realises that nobody makes suitable thrusters (motorised props) and finds that there is sufficient latent demand in the wider world to produce the first six hundred in his garage and to sell them on.

Aerial drones are ubiquitous platforms for capturing video, but increasingly they are used for ancillary roles in surveying, inspection and reconnaissance. Aside from me, few people want an FPV powerboat that can be driven from a sofa near the seaside; though there's a burgeoning demand for maritime drones for hydrographic surveys on or under water at a reasonable cost.

The fact is, these things ~ like their airborne associates ~ fulfil roles that previously did not exist, being unaffordable. The model above retails at £5000 here, altogether cheaper than chartering boats and crew.

When it comes to drones then (a) waterways and seas are under-exploited and (b) there's money to be made from successful maritime designs.

Though as with all successful enterprises nowadays, it's best begun as a bit of fun.

Deep-osits

In retrospect the mistake I made with experiments over many years with electrified means of flight, was imagining that it was ever going to be cheap. The front-runners seen here ~ developed in Europe, the US and UK ~ are all taking deposits up front for deliveries from hereon in, although Pivotal (centre) lead Jetson (above) and are far ahead of Axe (below).

Broadly however in terms of pricing the Jetson starts at around $150,000, the one looking like a flea from $200,000 and the spindly one an eye-watering $350,000.

They are a part however of an aviation/boating ecosystem that considers $100,000 as a bargain-basement price for anything you can sit in that moves.

There are though a lot of rich people out there, and if I had the disposable I'd want one too. If you are considering one, and I doubt anyone reading this is, I can offer a little advice that stems from a lifetime in and around aircraft.

Firstly, they haven't started crashing yet and are not immune to accidents that even a computer won't get you out of. I began my flying career sat with a parachute built into the seat, and I think I'd still want something similar strapped to my backside in the event of flying any of these.

And the temptation to fly low in each of these ~ watch the promo vids ~ is contrary to a century or more of aviation practice that views considers height to be the best possible insurance against death. The Jetson has two propellers at each corner for redundancy, but inadvertent collision with unseen elements of the urban landscape means you are going down... and doing that from 50' or 100' feels much like 1000'.

On balance, which would I choose? Well helicopters have always been about specific roles and flexibility of use, while fixed-winged aircraft have always been about going places. The Jetson is therefore a great means of hopping between your super-yacht and the shore, or else flying for pleasure.

It is and always will be, however, decidedly limited by physics in terms of range and endurance. Add wings as Pivotal have done, and you can reduce the power used in vertical take-off and landing from 80% to an extraordinary 10%... helis like Jetson recover only a fraction of that efficiency once in forward motion.

The one advantage I can see for the Axe in conventional terms would be its ability for rolling take-offs and landings. The most successful fixed-wing VTOL in practise was the Harrier jump-jet, but its fuel-consumption in the hover ~ where it was near twenty times less efficient than a helicopter ~ was significantly reduced during what were called short-field take-offs and landings with nozzles nearer 45° degrees 90°.

What eVTOL developers have found from flight trials is that near-vertical take-offs and landings burn through a sizeable proportion of fuel reserves, which is probably why they all still feature wheels.

Whether it makes the Axe worth almost twice the Pivotal or three times the Jetson I shall leave to you, but clearly there are people out there that do.

The joker in the pack as ever, though, has to be the Chinese. As a paid-up member of the Vertical Flight Society I cannot help noticing that ALL the latest developments in means of personal mobility like these stem from thereabouts. They are in process of making the global market for EVs their own, and I see no reason why this need not be extend into spaces soon to be occupied by PAVs or 'personal air vehicles'.

They may yet be altogether more affordable in fulness of time, like the family car.

Whether it happens while I'm still about is questionable, so I'll just keep droning on.

Clutterfuck

This nice man, at https://www.youtube.com/watch?v=QX68_FZl8UE explains how it is that the Russian Black Sea Fleet has been largely confined to port whilst its senior personnel have been fired over losses which their replacements have proven equally helpless at preventing.

Aerial drones are comparatively simple to shoot down ~ unless their numbers prove an issue in itself ~ because they are relatively easily detected by radar, and shot out of the sky by radar-controlled means.

Apparently this is not nearly so easy when it comes to drones that move on water, because the sea is as adept at reflecting radio waves as it is the light waves that make for all of those sunsets captured on our holidays.

What this means is that once within anywhere upto about 1000 metres from a ship, drones are really only detectable by sight... which at night means not at all.

We could be living in an age where lots of big things looking for each other with a view to kill is replaced by lots of smaller, like mammals fighting over territory that dinosaurs once ruled. At the outbreak of both world wars, military leaders were also seen as dinosaurs... and I suspect that they still move among us.

As yet though drones have dominated air rather than sea, building as they do on a rich heritage of RC hobbyists flying model aircraft and more recently multicopters.

In contrast, the reason maritime drones still look like scaled-down boats is that little thought has been expended on how they might be improved.

A situation that may yet be set for a sea-change.

Skewered

Here's another top tip for eliminating fasteners: laminated XPS of the kind we're using at present is easily fastened with either tooth-picks, cocktail sticks or indeed kebab skewers. Titter ye not, as Frankie Howard may say: the latter are almost indestructible, being from places prone to hurricanes where plant-life has evolved to bend and not to break.

Kebab skewers are harder to source once summer aisles are depleted at the store, where you should check with staff that they are suitable for flight in ground-effect. An alternative is Aldi Wagyu Beef Kebabs at just £3.99, including four skewers that I shall be stress-testing in the lab once I'm done eating. 

Wickesepedia

In an effort to make the build simpler and quicker, besides eliminating brackets and fasteners, I've looked again at a Wickes product called NoMorePly. It's extruded polystyrene (XPS) sheet laminated both sides so as to eliminate plywood... as the name suggests.

It is designed to be suitable backing for tiling, but it meets our purposes admirably: easily cut, lightweight, robust and waterproof from the get-go.

I've cut the 600mm by 1200mm sheet into four and devoted two parts to either side of the deck, a third to the keel and another to stabilisers that we'll see soonest: the split along its length being 280/280/320/320mm.

I secured the keel the last time I used this material with a plain abutment and was not entirely happy with the result. Here then I have carried it through the deck like a 'dagger board' so that filets of adhesive can be applied to all four corners where the parts intersect.

It's not the fastest adhesive you see here, but then neither is it the most expensive. If you're in more of a hurry, fast-setting epoxies can be used instead.

The sheet weighs 3.74kg or eight pounds and is black, which saves on spray-paint.

And £17 per sheet is not a bad price to pay for a hull, all things considered.