Mostly MOSA

Modular design has long been the foundation of sound systems engineering approaches to enable rapid, efficient and reproducible designs that facilitate upgrades in complex systems like those found in the aerospace industry. Although modularity and interoperability have long been requirements for US military weapon systems, the Department of Defense (DoD) only recently required a Modular Open Systems Approach (MOSA) for major acquisition programs, including for vertical flight aircraft. MOSA is now enshrined in law as part of the National Defense Authorization Act for Fiscal Year 2017.

The precipitating reason why this became a requirement in US code is debatable, but the facts aren’t. As technology spirals shorten, systems become more complex, and the cost of procuring and sustaining weapon systems increases exponentially. Operational overmatch in the current and future operational environments is heavily dependent on faster technical upgrades, increased interoperability and, probably most important, affordability during the entire lifecycle of a major weapon system.

Extract from Forbes. Extract from me, Abrams tanks have been withdrawn from front-line use in Ukraine due susceptibility to attacks by drones costing ten thousand times less.

In an age when flat-pack cardboard drones operate on the front line, whilst we won't be seeing DIY and modelling material among the principal players, we can imagine them performing in expanded roles as extras.

Imperial Rule

I switch to Imperial measures as they are a whole lot easier than millimetres to use as a means of scaling the outline up or down. Why might you want to do this? Well your trailer might be wider or narrower than mine and as the width across the outsides of the skis is the determining factor here, the remainder can be scaled in proportion with just a simple brain and a pocket calculator.

Lessons Learned

(This my C of G calibration equipment, incidentally... move the craft back and forth on the garden hoe until it appears balanced, as here.)

What though are the takeaways from Phase One of the build?

(a)    We've too much buoyancy and can revert to 20mm foam panels instead of 25mm

(b)    Ditto, so we can lower the deck back to amidships where it will assist level trim

(c)    The bar up front can come off pending fitment of lift motors

(d)    All wooden spars can be sourced locally as they are all sub 2.40m (eight feet)

I may offer this prototype 001 along with the electrical kit to whomever would like to wire it and try it for themselves. That said, I'm probably the only one in the UK stupid enough to spend my time doing this sort of thing.

Static Buoyancy Test

Red-letter day as we take to the water, eventually. The local fish-pond is peopled with too many anglers and the pond in the woods over the motorway is peopled by doggers according to my risk assessment and collection of videos.

Has then to be the canal, where I'm pleased to see that it doesn't sink, tho' it looked that way for a moment as it nosed into the water. Your inclination like mine is to feel that the craft is nose-heavy, except that it is perfectly balanced around the centre of the side-panels and centre-deck.

What is raising the back end ~ itself not an issue as it will raise the props clear of the waterline ~ is the buoyancy in the wooden spars and foam skirting board back there. I shall take the bar off at the forward end, however, as it saves 0.3kg and that is 3.5% of the gross weight and not to be sneezed at... it will also make it easier to carry.

Pre-Launch Weigh In

With 1.50kg of ballast at the back end to sub for a pair of power-plants and associated electricals, the ship weighs in at dry-dock at a mighty 8.50kg or nearly 19lb, so we can expect a final gross weight of circa 20lb when we're wired up and good to go.

From the side panels alone my team in the lab are predicting 9.5kg of buoyancy up to the base of the centre-deck, which if fully submerged should provide a further 7.0kg.

Teledrone's CEO comments, "Assuming there are no icebergs in the fishing pond ~ and the forecast is clear ~ our calculations do indicate the prototype will remain afloat."

Devil's in the Detail

Took a while to figure out how to attach the skis and at either end I've done so with a small angle-bracket. Those at the prow, as here, need to be bent with a mole wrench to match the lie of the hydroski once flexed. Then you'll need to flip the craft over to fix the ski to the bracket with a 4 x 12mm pop-rivet. Use a washer beneath the head of the rivet so as not to penetrate the softer foam core of that skirting-board material.

Power-Rail

I've reduced the beam to fit the trailer. so the dimensions are now 2.50 by 1.00 metres to the outside edges of the skis. At the same time I've extended the upper spars on the pontoons to 2.0 metres in length, which provides for a pair of pylons at the stern to support either each of the motors, or else a removable power-rail that supports the motors instead... as seen here.

There are numerous advantages for this arrangement, not least that in our case it can be used to inset the motors so as to reduce the overall width of the craft. Eventually I would like telescopic arms so that the motors and propellers can be retracted for the purpose of mooring; but then there are folding propellers out there that address such issues equally well.

Here you can see that a power-rail 1.20 metres or four feet wide provides measure of protection from the propeller disk, by at least flagging up the extent to steer clear of.

Jackin' Off

And I can't wait to use that as a chapter heading in the forthcoming ops manual, but I've made further mods to the pontoons specifically to support the power-plants, and the easiest way to drop and re-fit a pontoon is with a car-jack. In conformance with our 'Home Depot' methodology, swapping out a hull has to be simple as changing the wheel of a car.

Simpler in fact, now those tyre bays use pneumatic drives to over-tighten the nuts.

Anyone beside me figure they're in cahoots with roadside assistance?

Weight-Loss Program

A rebuild to reduce the length to eight feet, for two reasons: firstly I need to reduce weight (it's now down to 6.2kg) and secondly with laminated-foam skirting supplied in five metre lengths, this allows for a pair of hydroskis from a single purchase.

At the same time the flotation panels and centre-deck are now 100 x 33 centimetres each, because carbon-fibre sheet and spars retail in metres for when we migrate from wood.

Nonetheless wood is the go-to material for rapid prototyping like this, and if nothing else reducing the dimensions by 20% in a day does demonstrate its versatility.

Next we'll fit motors at the rear, and then drop it into water for a static flotation test.

That'll be in the canal, where a brass band will be present besides a marquee for tea and scones.

Finally the reduction does make it easier to carry, and happily it still fits through doorways albeit on its side.

Weigh-In

Pays to keep an eye on it at every stage of the game, and our proof-of-concept we saw yesterday weighs in at 18lb or 8.2kg.

It also pays to bear in mind that the largest flying-boat closest to commercial service in the shape of the Saunders-Roe Princess was hamstrung by use of Bristol Proteus engines that were rated at 3,500 HP and actually produced only 2,500 HP.

On a somewhat smaller scale I review the performance figures for the T-motor U7's earmarked for use, being the only ones I have lying around the workshop.

My favourite part of the table is the last column, where the operating temperature is normally listed but here simply says HOT.

Well each power-pack in the shape of battery, ESC and motor weighs in at 0.7kg, and the upshot is that with all six motors fitted viz. four for lift and two for cruise, in order to hover we shall have to drive the lift motors at 75% from the get-go.

Things are improved slightly in view of the fact we'll be operating in ground-effect, tho' this only compensates for the drag on propeller efflux induced by the pontoons, aside from the fact that manufacturer performance figures are generally suspect.

Beyond the boat itself weighing 8.2kg, six power units weigh 4.2kg, four weigh 2.8kg and two alone would weigh just 1.4kg.

In turn this might mean that we'll need two prototypes, one to demo the hover and another the cruise i.e. one with just four lift motors and another with just two for cruise demos alone.

(It is at such times as this as you will see the benefit of vectoring propellers, because if the two cruise motors could help with the heavy lifting, you've improved that ability by 50%.)

Nonetheless it is what it is, and as it happens mulling on this overnight I like the idea of going metric and basing the kit-build solely around one- and two-metre lengths of spar.

Beside this reducing the buoyancy, it will make the craft more portable for deployment by an individual besides reducing that basic weight a little...

... and every little helps.

N.B. Thrust appears in grams in the fourth column along from left.

The Unbearable Lightness of Ski-ing.

Well good progress on the day, and it looks a reasonable test-bed for our concept viz. a boat that might elevate itself into the air and hover over to launch itself upon water.

I am especially pleased that the entire build is 'Home Depot' doable (or 'B and Q-able' here in the UK), and I view this as the best use of two lengths of uPVC skirting-board that I've ever seen.

There are a few things I shall change come the next build, but as Ol' Blue Eyes once sang, too few to mention.

Automobile designers talk about the 'stance' of a vehicle, and whilst this one here is not spot on to my eyes, it ain't far off.

That skirting incidentally is simply screwed to the underside of the sponsons and then secured with a sliver of sanitary silicone.

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...

Naval Gazing

An aerial view here of the mighty shipyard, the two pontoons sprayed up in battleship grey. There are two reasons for this ~ one being that naval aircraft are this colour and so too are prototype aircraft.

The principal reason for the choice for our own selection of this livery is (a) it's cheap and (b) the dust gets everywhere and is better grey than otherwise.

As it dries quick, too, we may yet get the superstructure rigged today.

N.B. The weight of the pontoons and centre-deck amount to 6.50 kilos (14.40 pounds).

Stern Words

Been on two minds about it, but decide to extend the runner at the base of the frame toward the rear in support of a longer hydroski and so as to help protect the propeller.

Besides this it means that the mass is better balanced along the length of the craft, which is something I want at every stage of development.

This involves a splice at the base of the frame ~ about where that pencil is ~ and the insertion of a longer length of spar.

We can move on now to mounting the deck, and to do so I've located a T-bracket at the three-quarter level to take the best advantage of the buoyancy provided by each of the pontoons.

I had intended to pitch the deck at the mid-point, but we'll see how this pans out as it can always be adjusted in light of the static buoyancy tests.

Riveting Stuff, Not.

I secure the backboards with half-inch screws, which are plenty cheaper than rivets. You don't need to space them out with a rule, but simply fix one in each corner and one in the middle, and then two more in the spaces in between. You can continue the process indefinitely... it's probably how the Universe was made.

Note to self: spray-on glue is useless.

All Square

We're on a roll here, and so I continue on to construction of the centre-deck. Being a simple child, I've made it four feet square. The foam board that you see will be its soft underbelly now we've gone with the decision to stick with the mismatch between the wooden spars and the foam. On the plus side it leaves us with enough of the latter (at a cost of £20) for s second prototype.

Which in turn means we can demonstrate one in HVR mode and another in FWD mode at sea.

Exciting, but not as much so as the chocolate cake I'm about to eat.

 

100% Proof of Concept

I think we can run with what we've got, as there's no design more flexible than this. Accordingly although the spars are 20mm and the insulation board 25mm thick, we can still use it so long as the softest sides in the form of unprotected foam occupy the innermost parts of the boat viz. the inside edge of each pontoon and underside of the centre-deck.

It means the structures are not as rigid as they could be, but sufficiently so... which is all you want in a proof-of-concept. It will mean tho' that the pontoons are handed in this case, and eventually you'll want them to be interchangeable.

Here I've taken one of the longest spars at three metres and located it along the top edge of the sheet of plywood, with around 46" projecting forward to support the ski and 23" at the rear, to protect the 22" propeller disk in horizontal mode.

Then I've made a frame from the remaining spars before spraying the ply with sticky glue and setting it all in place. By way of 'belt and braces' there are screws driven in at either corner (as illustrated by the screwdriver). Finally as with all my signature dishes I've run a bead of silicone around the perimeter of the insulation board and filleted it with my forefinger.

Leave to set over night, along with the right-hand pontoon (this here being the left).

One Step Forward and Two Back

This is another reason for living a project-free life: despite the timber specification on the website being 25mm x 25mm, I look at it thinking it's very thin as inches go... and yes, it's 20mm x 20mm.

Which naturally does not match the foam I've just bought, which will need returning.

If I complain I know they'll just say it's PAR (planed-all-round) and that I should have guessed that the measurements listed would be nominal.

But they're not, are they, because they're precisely 20mm: so why not call it 20mm timber? 

Because that would be too easy, wouldn't it, they adapting to us and not we to them?

I would call to ruin their weekend, but they finish at noon on Saturdays so I'll save it for Monday morning when they're at their lowest ebb.

Fortunately there is 20mm thick foam sheet out there, but I'll need to travel to get it.

I call myself as chief designer to say that I just cut buoyancy by 20%, and then put my chief designer hat on and choke on my cappuccino.

Imagine what might have happened were the Titanic built like this...

Foaming at the Mouth

Here's the flooring insulation board at the heart of our machine, from a timber yard so close that I can walk it home above my head... good in view of the fact it's raining again.

I note that it's yellowed around the edges, a lengthwise crease betraying the fact it's been bent at some point.

"This is supposed to be aerospace quality!" I yell at the guy.

"It's how we lost the f**cking COLUMBIA!!!" I roast him.

All in all, a good start to the weekend.

Spar Therapy

Use a good timber yard and they'll have a variety of lengths from the wholesaler, and we ideally need an uncut three-metres for each uppermost spar in the pontoons. Our keels are effectively on the topside, unusually for boats.

Accordingly I figured we'd need a pair of ten-foot (3.0m) inch-square (25mm) lengths, although we are likely to use nearer nine-feet for each.

We also need four eight-foot (2.4m) spars for the remainder of the frame, one for each pontoon and two for the centre-deck assembly.

The timber has cost less than £100, which does not usually go far when you're into sailing anything nowadays ~ so well done me.

The spars are stock redwood and planed all round... or square, actually.

Varnished Truths

Once your okoume panels are safely home, they need sealing with either (eponymous) sealer or a 1:4 mix of white spirit and yacht varnish as I've used here. Always keep the area well-ventilated, and stop if you see over-sized pink rabbits.

In fact I've done this in my 'sterile' manufacturing facility, where the air is filtered so no particle larger than two microns can be found.

There's a nest of ants though.

A Big Day Out

I head to the boat-builders in the Lake District, with the heater on because it's only July here in the North of England. I like what I see, which appears well up to my own wood-working skills.

I leave with six identical panels of 1.50mm three-ply sheet okoume wood, having had a Scotch Pie and coffee while the cutting took place. The grain runs lengthwise, which is not something I'd considered, along the sides of each panel. Sheets of three-ply under two mil thick seem unreal, and the owner said the mill doesn't like making them for that reason... they're difficult to get right.

I leave a happy man, the scent of okoume filling the car. Phil had said that since the UK left the EU their exports have dropped from 40% to nearer 5% ~ another way in which the politicians help our small businesses. Exports further afield tho' included body-shells for speed trials in Arizona (for cars I guess and not boats).

The sea-going kayaks in the photo weigh just 18kg fully-fitted, apparently lighter than could be expected of any composite construction. It being a one-stop-shop for all my timber needs, then, I let Phil know I'll be back for customised hydro-skis.

(Admittedly he'd looked sceptical at the outset, when I explained I wanted my boats to be able to fly themselves to the sea-side.)

Altogether a worthwhile trip though, eh Gromit?

King of the Swing... ing-Arms

Notwithstanding my suggestion that we test the craft in the hover first, it is actually a better idea to test it initially as an airboat. This is because (a) any quad can be made to hover and (b) tuning it is expensive, not least because it requires four motors in lieu of two besides a flight-controller.

What you see above therefore is two alternative positions for fitting a motor to each  pontoon, and not a recommendation for a pair of propellers... although it might be.

In order to test whether the boat performs better with a mid-mounted pusher or high-mounted tractor, we shall replace the swinging arm with a fixed king-post as seen in the diagram.

It shortens the overall length of the craft to nine feet, for it's the motion of the swing-arm to the horizontal that extends it to ten.

It's a revolutionary boat, but assembled with good old-fashioned joinery skills... good to know then that I was useless at woodwork at school.

But can we build it? Yes Bob, we can.

Oh, We Do the Okoume... Oh, We Do the Okoume!

I've been browsing the web in order to choose a sheet laminate for the sides and deck of our flying boat. An obvious choice is carbon-fibre, seen as sexy by most designers, but only so you can wave it like a Rolex to show how rich and clever you are.

Sheet alloy is comparatively cheap, but the first site I looked at in Nottingham wanted £50 for the material and over £400 for delivery. WTF, I asked them... you sending it on a summer holiday?

Am drawn however to this nice man's hardwood ply up in the Lake District, which is as inexpensive an option as any, beside drawing upon a rich tradition of boat-building. As a consequence I plan to take the trailer up there and join him in a tot of rum and a few "Ahaaars."

Somewhere though a monkey has woken up and is wondering where it's tree has gone.

RIB-tickling Inventions

Possibly the most influential innovation ever on water, the inflatable boat dates back almost two hundred years (and that coming from the UK unless you count hanging on to the bloated corpse of a seal). What made it the most populous form of watercraft ever, however, was the addition of a plywood floor by a headmaster in Wales with the assistance of his sea cadets.

For you just never know whether something will succeed, unless it's one of mine and then you know it won't.

This is a picture of the very first rigid-bottomed inflatable, recently restored.

4-4-2

The principal obstacle to building the SLB is currently the fact that I'm tired of life and leap out of bed each day thinking, Fuck... is this all there is? To the extent I've drafted a promo vid in which I walk on stage in a black Miyake polo-neck and say, "Hi! I'm the CEO of TELEDRONE and I'm here to tell you how tired of life I am. Can't you just give me the money anyway, and save me building the boat?"

Nonetheless it's therapeutic ~ like a jig-saw for idiots ~ principally because it doesn't involve seeing other people. 

So this is how I'll outline the catamaran, based on a construction using a single sheet of plywood.

Three outlines arise from this draft as to how the prototype should be tested viz. (a) in the hover (b) moving on water and (c) transitioning from one state to the other.

Though the most sensible would be to test it on water, the more expensive option of getting it to hover first may make for better PR, because nobody on Earth has seen a boat carry itself from the driveway into the water.

4-4-2 incidentally is the classical formation for the outfield players in a soccer match. As it refers to previous designs, however, I've always found that the ideal ratio of width to length is between one to two-and-a-half, and one to three. Thus the outline above has hulls ten feet long, divided between forward, midships and stern at 4', 4' and 2'.

It may turn out to that it is in fact able to skim across (albeit calm) water even in the absence of those rear propellers being vectored for forward thrust.