Day Boat #15

In your choice of two of the four holes in the motor that we could have used ~ in accordance with 737-MAX methodology ~ make sure the wires appear on top of the deck.

Spoiler alert: because the width of the laminated keel coincided with that of the motor-mounts, the spar would not 'sit' as required. I contacted Airbus at Broughton who, after running the data, suggested I hit it with a 2lb lump-hammer.

 

Day Boat #14

To mount the motor, pop the forward spar and mark it with an asterisk to make sure that it goes back on the same way and all the screws line up. Then at centre I've countersunk a recess for the back end of the drive-shaft (which protrudes for reasons best known to T-motor), along with a couple of 2mm holes at 30mm apart.

Note the spacers on the bolts to prevent them piercing the windings if possible... tho' they did anyway, because the U7's a fairly shit design.

Day Boat #13

As with the laterals, leaving the ski connected to the hub will flex it around the base of the keel and in either case this is not what we want as the adhesive cures. Again we can release the ski temporarily, though to keep things moving along we can also apply ballast to the boat stood upright, and clamp or tape the deck temporarily. To avoid the expense of a clamp you can also do this with the boat remaining inverted with weights both applied to the ski and used to apply pressure down each side.

I realise that involves the expense of purchasing a range of weights, but these are much more easily shifted come January on eBay than the alternative... I've yet to meet a woman who'd like a 36" screw-clamp at any time of year, but live in hope.

This completes construction prior 'fitting out' and applying the line's luxurious livery. Reviewing progress ~ which allowed for a coffee ~ I see the metadata spanned the time between 09:30 and 14:30, or five hours. Nice work if you can get it?

Day Boat #12

The keel is doubly-secured with a filet of adhesive along its lengths, best viewed at floor level as here to ensure the best possible grab. Past experience shows silicone to be adequate to this purpose, as anyone who has tried to remove a bath-tub from the wall will appreciate.

Day Boat #11

When I cut the hub from an unplaned four-by-one inch (100x25mm) plank that was hanging around the workshop, I truncated the tip of the triangle by a fraction so as to leave a void between the foremost parts of each spar, into which I've dropped a dowel (with thanks to our sponsor, IKEA) by way of a snubber to hold the ski in situ whilst a two-inch screw is driven into the block. By altering this position along with the extent to which the screw is driven, the curvature of the ski can be adjusted.

In fact by altering the angle between the sides of the hub you'll do much the same with the curvature of the laterals; for the simplest however the curvatures here are broadly representative of their flexure when simply brought to the same point.

What I do as a belt-and-braces means of securing this front end is simply to squirt a dose of adhesive into the void... those that foam slightly are ideal for doing this. By these means the attachment is prevented from working loose so that we can avoid that dreaded 'Hydroski Fire, Severe Damage or Separation' drill' when in operation. 

Day Boat #10

To round the ski ~ a length of laminated skirting board ~ I've drawn around a tin of paint and then jig-sawed the forward end to suit. The ski has been mounted with an inch (or 25mm) overhang at the rear, so as to provide a basis for the rudder-post. Once this is done, the ski has been screwed into the forward and rear posts of the keel prior to flexing at the bow and attaching as shown next.

Day Boat #9

The laterals have been screwed to the hub at the front end and both here and along the edges of the underside of the deck we've (what do I mean, we?) a bead of glue to help secure. The laterals do tend to bow thereabouts, so ideally you'd release the spars from the hub prior and whilst curing overnight. Here though we'll press on...

Day Boat #8

These laterals are a moveable feast, but we've got to start somewhere and so I've gone for six feet. I've built such models over many years and experience suggests that an overall length of between 2.50 and 3.00 times the length of the deck looks about right... so this is pushing the upper end of the scale.

Here I've used strip-wood of around an inch and a half by an eighth (40x4mm) and cut them down to match the length of the uPVC hydroski that I've used previously. Setting the boat on a line feature to centre the prow, sketch out the template either directly onto a length of timber or else a paper template.

Day Boat #7

After truing up the keel using the set squares, drive a screw through the brackets to secure and run a filet of adhesive down either side.

If you are likely to pull things apart to pursue mods, use bathroom silicone instead.

Now's a good time for a coffee and without sounding too much like Alan Partridge I have chosen a Krispy Kreme pistachio-flavoured ring-doughnut, and a Dolce Gusto.

Day Boat #6

With temporary ~ or I may let them stay on if they're good ~ brackets in place we remove the keel and run a squirt of adhesive to take up the slack, because the 'lie' of my keel would frankly be described as 'fairly shit' by those same master-builders.

Day Boat #5

In a move the master-builders of our gothic cathedrals would admire, the keel slips into place without a mortice-and-tenon in sight. Instead foam is glued either side, in sections here as I'm scraping the foam barrel.

Day Boat #4

Meanwhile back at the deck ~ ensuring its 25" length runs left to right here ~ I pop a screw into each corner of the spars that form our leading and trailing edges.

Do not add any more screws at this stage, because that allows the spars to bow out if necessary when the keel is inserted. Also do NOT glue the leading edge spar as it will need to be popped off later in the day to install the motor. If you do, don't come crying to me.

Day Boat #3

Here's mine and note I've made the screws clear the upper edge, which will be sunk into the deck. I've used colour-coded screws to show which end will face forwards. I'm not sad enough to paint screws, incidentally: they're a leftover from prior builds.

Day Boat #2

Apply the reverse side of the keel, and drive a screw into each corner to engage the keel-posts... not too near the end so as not to split the wood, kids.

Day Boat #1

(N.B. occasionally Google updates Blogger but screws it up at the same time, like when you decorate and knock the paint over the carpet. During this period I shall resort to using the Verdana font instead of the preferred Work Sans. Get over it...).

Fresh from revising the template for the original prototype appearing on the website I collect the materials to suit in order to rebuild it with a modified keel to suit a 22" propeller... of which like Del Boy I've eight in the garage. The materials of choice on this occasion are Wickes' 3.6mm plywood and B&Q's 25mm-square timber spar, as each do one product but not the other. Fortunately they share the same retail park, where you can also purchase (as I did) McDonalds sausage-and-egg and flat white.  

The first step is to cut according to the 23/25" template, using the former for a keel and the latter for a deck. The former will be double-sided and we lay out each keel-post along with the 25mm insulating foam, and underlay each with a dust-sheet. This is because these are spray-glued in place and I don't want to stick to the floor afterwards.

Missing a Trick?

The latest build being a work in progress, I pause to kick it around in order to compare and contrast it with the plywood build which still features at www.teledrone.com. The gut feeling is that the first remains the better structural build, though while reviewing the templates I note an oversight, which in the event means I can replace the original pair of alternative patterns with the above... which suits all purposes. Sometimes you need to step backwards in order to go forward.

Pin Number

I've had a number of emails (Ed. in his dreams) asking for ways to keep fore and aft sections of the keel aligned during assembly, which reminded me of an old technique that I used to use back in the day. It's the best use I know of for cocktail sticks except for drinking cocktails with Maraschino cherries on the end of them. Alternatively there are kebab sticks for larger projects, which you can get free at BBQs whilst no-one is looking.

Lateral Thinking

Broken off from DIY around the house to fit the laterals here, which I figured could be done at the same time as setting the keel in view of the fact it'll be curing overnight. A pair used before are re-purposed here: quarter-inch laths standing 1" (25mm) proud of the 20mm insulation board to allow for an adhesive filet.

I've left a 20mm overhang at the trailing edge to accommodate a rear spar, which with the keel will support the rudder-post.

Wickesipedia

And thar' she blows! In fact I'm so pleased with it that I draft a press release:

Marine architect and CEO Colin Hilton commented: 'I'm delighted with the outcome of the switch to supplier, though coming from Egypt we'd worried it were pyramid sales. It suits our purposes ideally and is a piece of piss to cut and paste.'

Wicked Wickes of the North

The go-to store for marine architecture so far as I'm concerned has to be Wickes, and while I was there to buy plywood I came upon sheets of pre-laminated XPS (extruded polystyrene) with a scrim of netting and cement. It addresses the need for something better insulated from heat and cold than plasterboard, so expect to see more of it.

I have though been on to the web authors to highlight it's ideal application to marine drones, or at least in my garage. And while I am not altogether happy with the text ~ I wanted its low radar signature emphasised ~ it passes muster.

Note too that it is produced in Egypt, and as a result is likely to be available globally. An alternative is pre-laminated PVC sheeting of the sort subbing for plywood in areas like signage. 

I was offered a container-load whilst flying airliners in China, but then we all have regrets in life.

(Ed. the loser was also offered bitcoin at $1000 a pop).

Sea Change?

A fictitious email in my inbox asks for a good-news story about drones as a way of relieving the burden of reading about them dropping bombs on people's heads?

And here it is. A shark fisherman in Florida uses a drone to drop bait because though he should normally use a kayak, he is prone to seizures... nor can he swim, which is better news for the sharks than for him.

On this day last week however a young lady was swept out to sea by a rip-tide and her friend earnestly looked for someone who could (swim). This would likely have resulted in two people drowning in place of one, and so instead our hero used his drone to fly a circular life-preserver out to sea and in reach of the hapless swimmer.

I like to think that this is something we could put our boat to some such use as ideal means of getting life-saving and location equipment to the drowning pending rescue.

It is unlikely to happen any time soon however, because the RNLI is awash with cash, it being among the most beloved charities in the UK. Their inflatable boats cost nearly a quarter-million pounds apiece... a price resulting from a captive market so much as anything else.

It's called Paradigm Theory and one of the few I recall from university viz. nothing changes until the people making decisions literally die off and the newer generation is open to newer ways of thinking.

Started out happy though, didn't we?

Wood Working

A way ahead of the UK in its thinking ~ understandable given its proximity ~ Germany not only builds drones in materials like plywood, but is building a distributed network of manufacturing sites to supply them in great numbers. The UK policy is importing its needs, which is of course the worst possible preparation for defence and the reason it had to import US assistance wholesale during WW2.

For the figures are astonishing. Between them Ukraine and Russia have deployed some four million drones during the course of the 'special military operation', which eclipses the number of aircraft deployed in WW2 by a very large margin. WW2 effectively gave us aeroplanes as we know them today, and the current conflict could be said to have done the same for drones.

Ukraine purchases as many as 10,000 drones per month from DJI to supplement the 100,000 that some of its factories already produce. Meanwhile Germany's Helsing HF-1 seen above is financed largely by the founder of Spotify, so many of you are involved in one way or another; the author of Linux via which you may be reading these words did point out that all technology conflates military use and entertainment.

The Russia's Molinya (inset) also features plywood and alloy tubing, and is available via Italy as a scale model that you can own for yourself for less than $100:

Neighbour's dog annoying? Take it out with a drone! (Munitions and goggles extra).

Not so SS-UAVe.

... as it appears.

In the video drones emerge from a mothership perpendicular to a 300-knot airflow as gracefully as doves taking wing from the hayloft.

They probably figured nobody would notice?

And they won't.

Wood Works

Seen here at the Hovercraft Museum on the south coast of England, what eventually became of the wood-and-fabric radio-controlled model first tested by the inventor of the first practical type. One weighs 300 tons and could carry 400 passengers and 60 cars... can you guess which?

The overwhelming impression left by a visit to the museum is what can be achieved by inventors, hobbyists or companies with a little wood and alloy along with engines borrowed from elsewhere.

Development of this type of vehicle was funded effectively by the UK government, though the chances of it still funding individual enterprise of any sort are decidedly slim. The two types of uncrewed drones recently flaunted by the PM, for example, were developed by individuals in New Zealand and Portugal.

Within my own lifetime ~ in so far as any form of transport is concerned ~ we've gone from an imperial power supplying the means of locomotion to the wider world, to one being supplied by such powers elsewhere. Drones tho' do upend the game at least for a spell, during which people like you or I may steer things in one direction or another.

POC #36

There's an alternative template here that allows for a greater choice of airscrews, with a deeper keel and wider deck. See if you can spot which one, for now our work begins in earnest...

POC #35

The 20 x 6" propeller ~ a beautiful piece of German craftsmanship ~ is fitted using a single bolt in the form of the spinner. It's a fine looking vessel, Sir, and no mistake!

POC Flotation Test #2

The craft returned to the water after re-fitting the keel with a foam insert throughout. Unladen it provides a surplus of buoyancy that I've never liked the look of, it seemingly dead in the water.

This is solved however by adding a 2.50 kilo battery-pack that sets the waterline about level with the underside of the deck.

The answer going forward tho' is to provide for a keel that can be flooded to a variable extent in order to suit the battery-pack of choice, which will be essential for the POC as I want to run with the lightest pack and so flood the keel to suit the waterline that appears here on the right.

An advantage of the design is that this dead weight of ballast will be released once on the plane, whereupon water in the keel will simply drain away; sustaining the claim of this outline to be the most efficient high-speed craft ever, ever, ever (no backsies).

POC #34 (retrofit)

I've opened up the keel to add more foam by releasing the ski at the forward end and removing the silicone filet along with the two retaining bolts upon its underside; then afterward reversing the process. With the silicone or adhesive providing much of the support for the ski it's a good idea to set it level as seen here so that it sets overnight with the craft standing true.

POC Flotation Test #1

No excuse really on a day like this not to don waders and get back to the pond, where more debris has been tipped by the locals in an effort to deter youths from carrying out static flotation tests: but I've suffered for my art, and now it's your turn.

Pleasingly the craft floats level, with its motor kissing the waterline... with a few lilies, Monet would have been happy painting this one.

Situation improved by rear-loading the deck with a 2.50 kilo battery-pack that is good for around twenty minutes, the craft looking like it's champing at the bit.

What I have to do now is replace the diagonal (forward-biased) foam in the keel with a rectangular panel that I hope will make little difference here, yet make building easier and reinforce the end result.

Spoiler alert: experience suggests that unladen this will raise the deck clear of the water but settled on one side ~ and look a bit shit ~ tho' I figure with the battery-pack added normal service will be resumed. Don't worry about liquid ingress to the motor, incidentally, as these things run submerged.

The boat weighs 9.50 pounds without the battery and with its C of G six inches aft of datum (the forward edge of the deck.) As the motor produces the same thrust it may be among the few naval aircraft able to accelerate vertically, or at least in theory.

Nice if it works.

POC #33

For those of you who have included biased buoyancy in the form of foam sheet added nearer the forward end of the deck, you will recall that we included a 'blow-hole' for the evacuation of air from the void at the rear of the keel. This hole in the monoski is to allow for the ingress of water upon launch, so as to pitch the craft nose-up at rest.

"Achtung Spitfire! Schnell, schnell... fullen sie die Ballasttanks! 

Wood Work

"MENZ two-blade propellers upto 20" diameter have an 8mm drilled hub, those with a diameter of more than 20″ have a 10mm drilled hub."

And armed with such guidance we can now move on with a choice of wooden propeller (though I recommend not telling people your having a MENZ).

POC #32

The best feature of T-motor's U7 is the fact it has an adapter for conventional props, liberating us from the need to buy carbon-fibre types that are either cheap but have to be sourced from China, or previously imported by dealers who will be caning you.

Multicopters on this scale call for carbon-fibre because they firstly require substantial airframe stiffness so as not to disrupt the onboard flight controller (which I know to my cost) and secondly because they struggle for range and endurance and need every weight-saving measure possible regardless of the expense... another reason that they cost silly money.

A further reason for departing from propellers suited to commercial drones is that they are optimised for hover, which is what most of them spend much of the time doing; whereas the (air)boat we are building is more like a slow aeroplane with a pitch that is adapted to significant forward motion.

This is one reason for instance that the propeller recommend for this 280KV motor ~ 20x6" ~ is difficult to source, because it is too fine a pitch for a propeller of that size fitted to fixed-wing aircraft. The good news is that there is a multitude of propellers of 18" and below in a range of different materials and with a wide range of pitches.

Another reason to avoid propellers for conventional drones is that they come in pairs (clockwise and counter), whereas for cashflow reasons if nothing else we need only one, don't we? And if we do need a spare, it has to run run in the same direction, doesn't it?

It being Sunday morning in the UK, consider that as being the sermon... turning now if you would to your hymnbooks?

Nothing about invention is easy incidentally, and nor is RC as straightforward as it may appear. The U7 adapter provides for a metric 6mm drive-shaft but comes with a collet that allows fitment of a prop with a 5/16" (8mm) centre-hole. Large propellers may come with a 10mm centre-hole or else none at all... drill these yourself at your peril.

Prop Swap

There is a time in the life of every father and son when you have to sit down and say, 'We need to talk about propellers'.

Accordingly the basic facts are up there for you to print off and discuss with friends behind the bicycle sheds, but here are a few pointers for when it comes to fitting out our (experi-) mental maritime drone.

Longer wings are more efficient. Swifts for instance have relatively long and thin wings and they never need to come to ground, sleeping and having sex in flight, which I had thought only airline pilots could do.

As propeller blades are rotary wings it follows that the larger the blade and the slower it's rotation the less energy they require to produce the same amount of lift (or thrust if we're talking forward motion as with the boat). A helicopter is up to twenty times as energy efficient as a VTOL jet in the hover, which is why jet-packs for people will only ever be rich-boys toys.

Turning to motors, these have a KV rating that specifies the RPM per volt and ours are the slowest of the three available for that model. Looking at the recommendation on the handout, you can see that the slowest motor is paired with the largest propeller at 20". Turning a smaller propeller faster produces more thrust, but there is a sweet-spot at which the motor is best matched to voltage and propeller, and that is using the 18" instead of the 16" propeller.

We have as drag-racers say, however, 'race what few brung' and in our case it is a 22" carbon-fibre propeller, a 280KV motor and a 22.2V battery-pack. What we have also brung, however, is a boat with only 10.5" clearance from the motor axis to the monoski and therefore we have to swap the 22" carbon-fibre propeller on hand for 18" or 20".

Given the 20" provides the greater thrust (four kilos instead of three flat out, albeit off the back of 24V) then we may as well run with that?

Given too that the prop will penetrate the waterline in part at some stage, that rules out carbon-fibre whose properties ~ like the price ~ are rarely forgiving. Anyone who knows me, too, will know that I don't want to steer further revenue toward the same people who supply ESCs and motors that are not easily paired.

The happiest takeaway from this is that our motor comes with an adapter to suit regular RC props that simply screw on with a single bolt, the way wheels on sports cars used to back in the day. This in turn opens up a plethora of options in terms of propellers on the market, all of which (like that pictured) are four or five times cheaper than carbon fibre too.

Nicks in alloy props can be sanded out, whereas carbon-fibre propellers have to be thrown away... we call it progress, which is why the planet will be here long after we've gone.

POC #31

In lieu of a cleat at the bow I've gone for a rubberised electrical conduit-clip, although alternative fitments that work here include a Go-Pro camera or (pictured) a 1:24 scale model of Kate Winslet and Leonard di Caprio... each available from among our merch.

POC #30

Unlike the Titanic's rudder ~ 80' tall and weighing a hundred tons ~ this was altogether easier to raise into position. It's a mock-up made of spare aluminium plate fixed to a length of fibreglass tubing with electrical conduit clips and 4mm pop-rivets. The top end will be fixed to the steering-gear but is held in place here by a two-inch screw. I want the 'throw' of the rudder to extend to nearly ninety degrees so that the boat can be stood on end for storage: one over the Titanic even if the lounges don't compare.

POC #29

Here's a view of the lower bearing for the rudder-post. Don't be tempted to grind any excess off while in place like I did because the 6mm bolt will get hot and melt the ski.

POC #28

Here's the reason for that one-inch (25mm) overhang at the stern, because the ski will support the lower end of the rudder-post. I'm pleased we've got one of these, because no vessel is complete without one: the Titanic's post was operated by steam-powered steering engines, but I'm hoping to get away with an electrical servo.

POC #27 (retrofit)

And here's why: I've dropped a 'snubber' in the form of a 6mm bolt into that space so that the front end of the ski is held in place whilst a 40mm screw is driven through to connect with the hub. All of these will be snap-on fixtures in the fulness of time, with IKEA eating their hearts out. Leaving the snubber in too will ensure you never have to ask your co-pilot for that HYDROSKI Severe Damage or Separation checklist.

POC #26 (retrofit)

I've re-done the hub and at the same time dropped it a little to match the fact that at the rear the laterals stand proud by a quarter-inch (5mm). Leave a void at the apex for the subsequent step.

POC #25 (retrofit)

I used 'pre-loved' 25mm timber spars as laterals, and here I've decided to swap these out with 6 x 34 x 2400mm spars from Cheshire Mouldings (product TM681 for those in the know)... reason being that as with elsewhere on the craft there's a lot to be gained from a sliver of silicone or adhesive in terms of doubling up on the fixture of parts.

These are fitted off-centre so as to provide a lip along either side of the deck where a filet of silicone can be applied. Adhesive is many times the strength of silicone, but is an irreversible join for one thing and around twice the weight for another. Either way it should be applied with laterals disconnected from the hub and set vertically so as to prevent them from flexing, and for a really close fit you can pinch the laterals as here. 

POC #24

With the craft inverted and ideally benched, apply a filet of silicone or adhesive at the junction of the keel and ski, on both sides. I've used silicone as it is easily removed if I should need to open up the keel to alter its buoyancy.

POC #23

With it weighted some more, slide the key forward to obtain the required flexure and measure off the tail level with the rear of the deck viz. 1" or 25mm beyond the keel.

POC #22

Loosely fit the front the ski with its remainder weighed down on the keel's underside.

POC #21

Using your 'laser levelling' equipment to check the bow runs true, fix the hub to that lateral that has already been cut to length and rig up the other before connecting it.

POC #20

Open the template out a little to make it easier to work with.

POC #19

To fashion a hub at the prow, spec the angles out on a length of timber.

POC #18

The curvature of the monoski can be adjusted in any of three ways:

    (a)    by adjusting the stiffness along its length by artificial means

    (b)   a wedge at the prow which adjusts the angle of projection

    (c)    by adjusting the dimensions of the craft generally

I am going for the easiest option of the three and altering the length of the craft as it appears currently. The deck is 24" wide and 26" long and I want the overall length to be around two and a half times the length of the deck.

To enable this I reduce the length of the laterals to 67" or 1700mm and the reason this measure is two inches (or 50mm) over is that these will be lost to the curvature of the prow.

POC #17

Bolt the laterals to the forward spar prior to attaching it to the deck.

POC #16

Use a laser level or ~ as here ~ a joint in the floor to tee up the laterals.

POC #15

Affix the end of each lateral to the rearmost spar using the means of your choice.

POC #14

Rivet or screw the rear spar in place, depending on whatever floats your boat.