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Here is how it looks from its best side. A block at the stern is reserved for the rudder, which if retained inboard allows for the boat to be stood upright for storage.

Aside from this displacement has been adjusted by use of a diagonal sheet of foam, which should pitch the motor clear of the waterline at rest.

The keel could in theory be sandwiched by rectangular sheaths of plastic sheet; whilst this would look rather better it would complicate the aerodynamics.

The reason a cat is a simpler build is the total absence of asymmetric effects deriving  from a single propeller. This produces a swirl in the direction of turn that impinges on the tailplane (or hear the keel), rotating the craft around its axis unless compensated.

Conventionally this compensation has taken the form on single-engine aircraft thus:

    (a)    offsetting the engine mount

    (b)    offsetting the tailplane

    (c)    rigging the wings at different angles of incidence

Tricky eh? The only means of compensation available to this bad boy will be input via the rudder.

Whether this will require the speed of a flight-control computer remains to be seen.

Circular Logic

Pursuing what my uni mate used to call 'the path of least resistance', I wonder if the boat could be tested under power but without a rudder.

In doing so I come across a pastime dating back practically a century... now pursued solely by old men in waders.

As I'm signed up to the fraternity on both counts, I look a little closer and it involves running hydroplanes ~ some powered by airscrews ~ around a pole on a tether at up to 100 m.p.h.

On the same day whilst doing what I like to call 'research' on YouTube I discover that the Russians have switched to communicating with drones along lengths of what is effectively fishing twine, in order to avoid jamming... and who knew they had reggae parties anyway?

The above video was taken at Verulam lake in St Albans, a place I knew well when I had money. Needless to say it's been banned there since, as it is a trifle noisy (while middle-class dog-shit isn't).

Accordingly it is now pursued only in Essex or at a lake in the East Midlands. I make a note of the dates and contact details, if only to find out how to fix a pole in the water.

I take my son to things like dog-racing and demolition derbies, simply because going forward the earnest desire of our nation is to be left at peace to watch TV. One of the few pastimes that has yet to be banned, it is also in tune with Labour's ongoing effort to pay people to do nothing.

Eureka!

I visit the static flotation lab ~ which some people insist on calling the bathroom ~ to see how my technicians (Ed. he hasn't got any) are progressing with tests designed to raise the motor clear of the waterline at rest.

Key findings include:

    (a)    We need a new plug because the water-level has dropped overnight

    

    (b)    We need a deeper bath because the rig is occasionally grounding out

    (c)    It appears the strategic distribution of foam does meet requirements

Altogether that's what I wanted to hear from the team, and like Elon Musk I fist-bump them all before departing the lab.

My only concern is that this rig is ballasted by a drill-bit along the bottom edge that you can see in the picture, whilst dead weight is something I want to avoid entirely in the proof-of-concept.

The what-goes-where of foam, ballast and payload however awaits testing of the boat itself and to this end I've bought a new set of waders from Decathlon.

Whether testing takes place under the watchful eyes of doggers and fishermen on the local pond remains to be seen... there are locals who hire their indoor pool for kids' parties and I'm wondering whether that's the better option?

All in all a good end to the week, so I skip the yoga class and eat a doughnut instead.

Re: Boot

If you're German, you'd get that (Ed. 'boot' is German for 'boat').

Did though mock up something like this but stabilised by outriggers, but it was to use a technical term: shite. I thus figured it was not necessary and that the mono could be adapted to suit.

And what appeals about it over the cat is the fact it needs only one motor and given my experience with T-motor's great-kit-no-backup business model, anything that reduces my reliance on electronic speed controllers is good in my book.

(It will though need a rudder, but servos are old hat and I've used them in the past.)

The previous mono having been broken up for parts, this I knocked up in a half-day using leftovers from around the workshop. It's six feet long, two wide and one deep.

As it's half boat and half plane, however, I'm having to design for both contingencies and as you will know, most aircraft have motors (and the C of G) pitched forward for stability. Thus the motor will appear as previously advertised: out front of the deck.

As it stands, the C of G sits around a foot to the rear of the centre-post, where you can see I've balanced the craft on a length of dowel. After fitment of the motor that is likely to be around six inches aft of that leading edge, which is ideal for those times when it breaches the surface like a wooden whale.

We have seen from previous flotation tests that these things sit nose heavy at rest in the water, though I think I've a solution for that which we shall investigate sooner in place of later ~ in fact I've not let the water out of the bath so as to test the notion.

The battery meanwhile represents useable ballast that can be located to adjust the C of G to best suit operation at rest and on the plane, with the benefit that unlike fuel tanks their weight and centre of mass do not alter as energy is expended.

As seen here it weighs 2.90 kilos or 6.40 pounds... one pound for each foot of length, which is not bad comparing to other monohull watercraft.