Skirting the Issue?

This is where the rubber meets the road, or rather the uPVC the water. With the angle section (which am not convinced we need) applied to the inside edge of each sponson we clamp the ski in place, with the bevelled edge of the skirting-board set toward the outside edge of the catamaran.

Because of this ~ 'til I call the manufacturer to complain that their skirting-boards are endangering lives at sea by having only one bevelled edge ~ I have had to mark them 'left' and 'right'.

Disgraceful.

Hydro-Skiing Lessons

I get many emails asking "Master, tell us how long our hydroskis should be... for we do not know?". In the workshop I flexed one end of the skirting-board up and saw that it was good. Looking at the other I said that from henceforth, six feet shall be removed. And because no skirting-board was made that was not five metres, each was now 125" long. And they were sore amazed, and went upon their way.

Hydroski Beat

I wander around the corner to the lumber yard in search of hydroskis, and tell them I'm looking for something to raise a twenty pound catamaran onto the plane at around ten knots. The store-hand points to uPVC skirting-boards: a chamfered 95mm type to accommodate drift. It should ideally be double-chamfered, and I suggest he mentions this to the manufacturers.

To attach it to the pontoons they have some 25mm angle too... happy days.

Keep it Simple, Stupid.

I publish an outline of what I consider to be the best arrangement of a self-launching boat with fixed power-units, to silence those worms which will doubtless appear from within its woodwork to say they'd thought of it first.

It may yet be the outline used for testing, not least because we've all the equipment on hand to build it right now... which for types with vectoring propellers we've not.

Secondly electrical 'air taxi' development has proven that types with separate lift and cruise propellers are as successful as others with vectoring propellers, and simpler.

Thirdly we have to factor in the consideration that I'm lazy and like a human flash of lightning, have always followed the path of least resistance.

(Actually there's a fourth, that being that yesterday's for all its advantages looked a bit of a dog, whereas this looks the dog's bollocks.)

N.B. references to dogs' testicles are indicative of excellence in the UK.

Quadrophenia

By these means I figure we can vector all four motors, allowing for the most efficient modes of operation. A benefit of this for our immediate goals is that I can now build two separate boats with the motors left over from my dismantled personal air vehicle. One will have motors driving the craft forwards for testing on water, and the other the motors mounted horizontally for testing in the hover. Incidentally, should there not be enough thrust for the latter, we can borrow two motors from the former and fix them around the centre of gravity of the latter.

Cookin' on gas, or electric which is even cleaner...

Six of One and Half a Dozen of the Other

 

I've reduced the beam to around one metre, which am happy with because material like carbon fibre spars tend to be cheapest to source around that measure. I think it looks better too, with a length to width ratio of 3:1, beside the fact the structure is strengthened by the reduction.

Nonetheless the thorny question of where to locate the motors rears its ugly head in a decidedly mixed metaphor, and either way it is looking like six at this stage instead of four.

In the developing world of flying taxis there are three principal modes of flight:

(a)    A multicopter with four or more horizontal propellers.

(b)    A set of horizontal propellers and a perpendicular propeller for forward flight.

(c)    A mix of fixed horizontal propellers beside vectoring propellers for forward flight.

(a) is out of the question for boats, because it requires a significant forward tilt when it transitions to forward flight, and that is the last thing you'd want in a fast-moving boat. It is also decidedly inefficient.

(b) has much to commend it. because it is as simple as it gets and was in fact among the first solutions for eVTOL aircraft.

(c) is the 'smart' solution, used by the likes of Archer and Joby among others, although vectoring mechanisms add weight and complexity.

I would like the 'lift' motors purely to add lift in the absence of a controller, but there are two problems associated with a simple lift arrangement like the hovercraft in the absence of separate controls for lateral motion.

For In the sci-fi 1960s era they thought we'd all be driving to work in a hovercraft if not a flying car, but the problems when they tried it were that weights like a suitcase set apart from the centre of gravity meant that the craft would float in that direction once airborne. Another issue was that for similar reasons, the thing would slide off the camber of the road into the kerb from the get-go.

Accordingly if you've four or motors raising say a boat into the hover, then it needs a flight control computer to adjust the thrust of each motor to balance these adverse forces out.

At this stage we can run with six motors (as seen down the starboard pontoon), with the rear-most helping out with the heavy lifting and vectoring once in water through ninety degrees to provide the forward motion.

Or we can adopt the arrangement seen on the port pontoon, where four motors are fixed to the float for hovering and a further motor is fixed to the rear to push it along once waterborne.

The first arrangement looks elegant and provides all six motors for launching the boat into the water, but from experience building super-sized drones, has problems written all over it.

The second, although an ugly duckling in comparison, is a fairly bog-standard solution. It also has the benefit at a larger scale ~ with me sitting on it in prospect ~ that all of the electrical components would be within reach without falling into the water,

At this stage of development the aim has to be to inspire, as Benz with the car and the Wright brothers the plane.

It's a boat... It's a plane... It's Superman!

Yes, I come with it too.

Foam Fatale

The seat's just for fun... for I know only too well that adding people to eVTOL aircraft makes life immeasurably harder and less remunerative altogether.

This is the craft without its hydro-skis, and really a look-see with which to form a first impression. I like the integrity of pitching the deck mid-height, but dislike the fact the upper half of the floats are redundant: worse still, they make too large a keel surface. 

The craft could be narrower to fit the trailer more easily. These apart though, we could be on our way to inventing the self-launching boat.

I may yet mod the pontoons and narrow the beam, but each are jobs for the weekend: "Drone was not built in a day" as they say.

The foam incidentally appears on the outsides of the pontoons and underside of the deck: I like the idea that foam panels could be clipped into place to suit the buoyancy.

N.B. That's me hanging from the rafters top left...