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 Extract from me, Abrams tanks have been withdrawn from front-line use in Ukraine due susceptibility to attacks by drones costing ten thousand times less.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