I once spent a morning with a high-falutin’ barrister from some stupidly expensive London chambers. I was due in crown court as an expert and he wanted me up to speed before some equally expensive defence barristers got their teeth into me and ruined his case. But he wasn’t with the programme himself because he’d been drafted in at the last moment to replace another who’d gone sick and wasn’t in the least bit au fait with such things as GPS navigation and sonar systems, so, on arrival he was given a three-quarter-inch-thick sheaf of papers to learn and chucked in at the deep end. This he flopped onto the desk, having bid a hurried hello, and proceeded to strum through it at impossible speed with one hand like Johnny-5 soaking up ‘input’ whilst making coffee with the other. Still reading, he struggled free of his overcoat and jacket then lowered himself into a seat and sipped his brew. Twenty minutes later he looked up and started asking me questions, his coffee barely touched.
What rapidly became apparent was that, from a cold start, he’d digested every detail and was already ahead with dates, relationships, happenings and circumstances whilst I struggled from the off to keep up with him as he probed and questioned and designed his courtroom strategy. I felt as though I was in the presence of a superior being – a very superior mind, at least.
He was mind-bogglingly clever – some people just are – and when I was a kid some people were mind-bogglingly thick too, but it’s not allowed nowadays…
Youngsters of our modern age may be treated as though they’re brainless but woe betide them if ever they try to do it for real.
When I was at school we had Biggles – now where’s he got to, you may ask?
Who else read the ninety-odd, oft-preposterous volumes by Capt. W. E. Johns as a young boy and absolutely thrived on them? I did. So where is Biggles today?
Erm… bit of a problem with the do-gooders nicking our books, I’m afraid. You see, Biggles and Algy and Ginger weren’t overly fond of anything Aryan, or Teutonic and occasionally looked askance at anyone not pure-bred European either. They smoked cigarettes and women were just that in their world – women – and such thinking must be thoroughly stamped out nowadays.
You could argue that Biggles is a kids’ book and early-stage xenophobia may set in but what about Huckleberry Finn? That had our American cousins in a proper quandary for ages because one of the lead characters is named after Guy Gibson’s dog – soon to be posthumously renamed for the new movie, I’m reliably informed – but Twain’s work is part of the fabric of American society so what to do? What they did was serve up a bowdlerized version with a view to getting more youngsters into Twain. This terrible disrespect of great literature was then justified by arguing that anyone interested would soon read the original anyway therefore nothing is lost. So give them the original in the first place, you fools! How stupid is that?
Of course, modern students are utterly incapable of realising that what happened in the book they’re reading might not necessarily be real, which is why readers of Harry Potter are often scraped off the front lawn with a smashed broom wedged up their sphincter and so much as a sniff of Macbeth causes whole classes of English literature students don tartan skirts and start unseaming innocents at the bus stop from the nave to th’ chops. See what I mean about treating people as if they’re thick?
When I was at school we had swots, nerds and bookworms on the one hand and duck-eggs, thickets, dimwits and knackers on the other. Then you had the rich kids with lunch money to burn opposed by those who smelt a bit funny but were endlessly adept at parting said lunch money from the rich kids. Life was so much simpler then with the nuggets bound for grease-monkey or can-laddie duty in the pits or shipyards and the clever ones off to college to be clean people like doctors or accountants. There were those who couldn’t write their name but were good at woodwork so that was OK – joiner for him. And others who would have their leg off with a tenon saw if left unsupervised for five minutes – bureaucrats in the making, every one of those. But now look at the state of the place.
Don’t ever mention anything that sets one apart from the next. Being rich, for example, is a no-no because that makes the poor feel all victimised, and being poor is equally verboten because it has some sort of negative social stigma attached. Being blind isn’t a disadvantage; it’s just an alternative lifestyle, as is having no legs or no brain. Don’t mention religion unless you plan to include them all and if marriage is on the agenda best you work out all the possible permutations of two (and it’ll soon be three – you mark my words) humans doing the wild thing before opening your mouth. Anything vaguely different or exciting is being mercilessly bleached out of mankind during childhood in an effort to expunge even the faintest hint of stereotyping thus forging the most glorious irony... the bland, standard-issue non-person.
Their very own stereotype!
I’m afraid that little Johnny is just not allowed to be stupid any more. In fact, he’s not allowed to be anything at all. No matter that he may be a square peg, he will go into that round hole even if it means having educational psychologists look up his bottom with a microscope and extra spelling lessons though he’s clearly going to sign the marriage register with an X. Teacher will never, whatever she does, admit that Johnny won’t fit the allotted pigeonhole or be able to tick the boxes on her target.
So – here’s a simple test. Should teacher tell you that little Johnny is ‘helpful around the classroom’ you can forget about paying expensive specialists to diagnose which previously undiagnosed syndrome is impeding his path to being the next Prime Minister. I’m afraid he’s just thick as pig’s poo and will be going to work in a boiler suit.
There, that’s that dealt with…
But the reason I got to thinking about all that stuff is because learning is a strange thing that waxes and wanes and pulses like a strange light in our workshop. It no more follows a rigid set of rules than falling in love. You know… we’ve all seen it, the Perrier-bottle-shaped bloke with a goddess on his arm or the suave, surfer type latched onto something that looks like she morphed into a partridge at an early age. It’s all very peculiar and when our lot set out on a new adventure, whether it’s sorting a gas turbine or mending air intakes, we never know until we get into it just who is going to take on the job and make it their own – it just has to come out in the wash. Along this often stony path, as Donald might have described it, we’ve had to learn how to recover wrecked material, fix systems, design tooling, negotiate with sponsors, entertain our audience and now we’ve had to learn how to make sponsons from scratch but they're not just floaty boxes stuck on the sides, they're actually serious pieces of engineering in their own right, as Donald Campbell historian, Neil Sheppard explains.
I'll let Bill cover the actual build of the sponsons, what I will attempt to cover here is their history.
Bluebird's two outrigged sponsons, and their attached planing shoes form the two forward planing points of Bluebird K7, and as such are responsible for transmitting significant loads and stresses to the main hull of Bluebird. Although the actual load bearing part of the sponson remained pretty much unchanged throughout their life, their appearance changed significantly as K7 was modified to extract more performance and extend it's safe operating envelope.
Bluebird K7 was designed as a conventional three-point hydroplane supported on a three-point stability triangle. Unlike Crusader, however, the Ventnor convention was adopted as in previous prop-riders such as K4, i.e. two forward and one aft plane (replacing the 'prop'). There are advantages and disadvantages to this method, but in hydrodynamic terms the former far outweigh the latter. Pitching stability is improved with two planes forward, and the extreme front loadings are halved compared to a single front plane. Transition from the displacement to the planing phase is improved by the two sponsons, which increase lift forwards of the CG.1, 2 Directional control is also improved because an aft rudder can be employed, yielding better low-speed control and reduced loading because it is further from the CG than one mounted forward as on Crusader. Even more importantly, since it is behind the CG it introduces a positive stabilising moment in yaw.
There are, however, also disadvantages. Firstly, the craft is prone to a phenomenon called 'tramping' whereby disturbances in the water’s surface can induce an alternate rocking movement about the axes of the stability triangle. The nose of the craft therefore describes a motion with both rolling and yawing components. This results in an overall increase in incidence (pitch-up) of the craft which is proportionate to the severity of the tramping, i.e. the tramping amplitude.
K7's upper sponson fairing's were initially shallow non-load bearing semi streamlined aluminium structures with a perceptible gradient running front to back, so minimise aerodynamic lift, and move the aerodynamic centre of
pressure back towards the area directly above the end of the planing shoe. Following initial trails at Ullswater in 1955, when K7 proved unable to successfully plane, it was decided that K7 displayed too much aft buoyancy,
and not enough at the front, and that the siting of the forward spar connecting the front of the sponson with the nose of the main hull was too low. A major redesign was called for, which involved lifting the forward spar, and alerting the pick-up point and associated fixing between sponson and front spar. This necessitated the inclusion of towers, approx. 10 inches tall to connect the two structures. The fairing's were redesigned to shroud these towers, and now incorporated two 'humps' at the junction of forward spar and sponson. This modification proved successful, and K7 was able to break the WSR 4 times in the period 1955 - 57. The modification however meant a deterioration in their aerodynamic lift characteristics, making Bluebird more prone to pitch up, and lowering the angle of pitch at which K7 would take off.
With this in mind, as the speeds got higher, in 1958, the Norris Bros, in conjunction with Prof. John Stollery decided to redesign the upper part of the sponsons, to incorporate deeper fairing's along their full length, and rid them of their unsightly hump. This not only improved the look of K7, it also had a significant effect on reducing front end aerodynamic lift. These were cleverly designed by Ken Norris so that their upper surface presented a negative incidence to the air stream, thus increasing aerodynamic download and reducing lift, which was reduced by nearly 60% at level trim and by ≈35% at = 6° pitch.
This configuration proved very successful at raising Bluebird's safe operating envelope beyond 250mph, and remained essentially unchanged for the rest of K7's life. It is interesting to note that K7 suffered the odd ding throughout its life, and the sponsons, and spars being outrigged from the main hull, and therefore exposed suffered more than the rest of the boat. The Starboard sponson aft fairing was creased in 1957, during her transit back from the USA, and in December 1966, K7 suffered two bird strikes which afflicted both port side spars.
The surfaces in contact with the water in a hydroplane referred to as 'planes', 'shoes' or 'wedges' and their design is of crucial importance to the craft. They need to produce maximum lift to support the weight of the hydroplane, but to do so with a minimum of drag to allow the craft to achieve the highest speed possible with the thrust available. The surface area of the planes in contact with the water, the so-called 'wetted area', and their immersion depth depend on the angle the wedges present to the water’s surface and on speed. As speed increases, both the wetted area and immersion depth reduce as the upwards force required to support the weight of the boat is generated by 'sweeping' across a greater surface area of water in any given second. At very high speed, the wetted area is relatively small, around 10–20 square inches, and the immersion depth is around 0.1". The planes have a flat profile As Bluebird's planes were flat, they had a dead-rise angle of zero degrees. Because of the very high and frankly bludgeoning forces, the planes need to be very strong. They also need to be very rigid so that they maintain consistent planing performance in the face of severe buffeting. Additionally, their design was such that they minimised pitching oscillations (porpoising) if the craft encounters disturbed water.
The specific hydrodynamic data to design the wedges were derived from NACA technical data.On the basis of the expected loadings, the angle of attack of the front wedges was chosen to be 3.75° and the rear 2.5°. The length of
the wedges was designed to be 72" and their width 12". This configuration resulted in a theoretical drag/lift (D/L) ratio of 0.08.13 The reciprocal of this ratio L/D is therefore 12.5 and is defined as the 'planing efficiency'. This figure means that the planes produced 12.5-times as much lift as drag. However, in discussions between the Norris brothers and Tom Fink it was felt that the planing efficiency would, in practice, be lower than this.
Following Bluebird’s crash, Ken and Lewis Norris and their associates performed extensive analysis of the crash itself and the performance of the craft on the final run.Included in this is a detailed re-working of the calculations of lift and loadings at the planes in the light of more up-to-date NACA technical data published in 1957. At a speed of 312 mph and a loading of 1,780 lb for each front plane and 1,070 lb for the rear, the wetted area for each front plane was 13.2 square inches and 12.6 square inches for the rear. The immersion depth was a tiny 0.072" at the front and even less at the rear, 0.046". From this, it is possible to conclude that the wedge angles were too steep for optimum performance of the craft, particularly when operating at speeds in excess of 300 mph. It is important to reflect here that the original Bluebird K7 configuration was designed in 1954 on the basis of planing data available at the time.It could be argued
that the sponson fairing redesign in 1958 offered an ideal opportunity to make modifications to the wedges, but perhaps this was not considered because K7 appeared to be performing very satisfactorily during that period. Also, Bluebird only had an anticipated life of a few more years and, perhaps, two more records. In addition, it would have involved significant engineering effort – and considerable cost – to carry out the work at a time when Campbell was focusing all-out on his Bluebird CN7 LSR effort.
A full description of K7's structure, and the forces acting upon the boat can be found in my book, Donald Campbell, Bluebird and the Final Record Attempt.
Creating the sponsons has been a very long job, in actual fact it began way back in 2006 as soon as the boat was donated, lock, stock and barrel to the museum. At last that gave us the security to crack on with the expensive stuff.
But the first problem was understanding exactly what had to be built. It’s easy enough to look at the pictures and think you get what’s happening but in all the time we’ve been doing this we’ve only ever found a handful of images offering clues to what goes on inside a sponson and not one of those tells the complete story. Then we had a heap of drawings that only served to confuse. The sponsons were drawn several different ways, as were many parts of the machine. There’s multiple ideas for such items as the main frame, spars and planing wedges and with the boat fully clothed you’d never know what was inside. That wasn’t a bother with the main hull and spars because we could simply have a look but it didn’t help much with the sponsons. Then there was the theory that the original sponsons were still in existence, buried somewhere on the old Norris Bro’s site at Burrell Road. Now wouldn’t that be nice – if someone could just take us to wherever that’d happened and we could dig them up. But we never really bought into that theory.
Think about it, a pair of 13ft canoes, each one so heavy that it’d take a couple of blokes to lift it and made of scrap metal that could be readily turned into cigarette and beer tokens. Imagine the size of the hole needed to bury them. It’d take a few blokes a few hours with time enough to wonder why they were burying money and surely there’d still be someone around to tell the tale who wasn’t counted in and wished they had been.
Those sponsons are in the foundations of the new building, we were told. So what did the building inspector have to say about that? It’s a nonsense to suggest that anything of such material value would have been binned by working men then or now.
Another tale had them vanished in the night when half of the yard was sold off to Ready Mixed Concrete leaving them marooned on the wrong side of the fence. Ex-Norris Bro’s employees were extensively interviewed in the quest for clues and gradually the most likely account was pieced together. It seems that towards the end of 1967 (as Christmas approached and the staff wanted a few extra quid) the sponsons were lying about the place as was the fuselage and wings of XM691 so it was suggested that the whole shebang be carted off to Coley’s scrapyard and weighed in. Ken was consulted and agreed and a day or two later a truck arrived and took it all away. In fact I knew all of this already because back in 2001 I’d asked Ken what happened to the sponsons and he told me they’d gone for scrap. So, barring a miracle, the originals are long gone and are probably in our fridges at this very moment wrapped around Coca-Cola and supermarket lager. Never say never, mind you, and in the meantime we had a couple of corners missing off our boat. It was time to get down to business.
It soon became apparent that at least one constant ran through all the available design data – the sponsons are rectangular in cross-section and along their whole length is stationed a series of bulkheads of varying sizes, while running down each corner is an aluminium extrusion in the form of a 90 degree angle formed to follow the sweeping contours of the sponson. If you took a slice through the middle of a sponson this is what you’d see.
Those extrusions became our first problem. You see, they’re a non-standard size and even if they weren’t they’re certainly not available in the material specified. It was easy back in the day because Britain was developing the V-bombers and everyone in the alloy business was vying with one another to be the top supplier so just about every conceivable grade was readily available in every possible size and section. Fast forward half a century and you can have about six sizes in five grades and get around that in the design stage, Mr Designer.
Well that was no bloody use! Try to rationalise what was specified to what’s available today and you may as well start from scratch and design the sponsons all over again. What people seldom realise is that each sponson is a small boat in its own right with its own weight and balance considerations and it has to perform accordingly. You’d never dream of rebuilding an aircraft for flight by throwing whatever was available into the wings, would you. It was actually easier to go in search of the real material than to start thinking about how to redesign the parts with modern stuff so that all the numbers stacked up.
So where to buy inch and a half by inch and a half by three-sixteenths angle-bar in DTD 363D alloy? It simply doesn’t exist.
The answer was surprisingly simple – have it made. It sounds ambitious but in actual fact it turned out to be quite straightforward. We were put in contact somehow or another, I forget now, with a bloke called Pete Isom at his company, Transtar Metals. Pete could not have been more helpful. He speaks fluent metal and it wasn’t long before we were talking to a mill in California, which seems to be the aerospace alloy capital of the world, by the way. All we had to do was pay for the tooling and, in exchange, they would ship us eight extrusions of the required section in the preferred material. They got to keep the extrusion dies and we got to keep the material and everyone won. In the end the material worked out at about a hundred quid a length and it was exactly what was specified on the shopping list.
Next came the sides, bottoms and tops for the sponsons, which are just big, rectangular boxes, at the end of the day, but they’re almost thirteen feet long too and that’s a smidge over your average 8ft sheet. In fact, nowadays, even an 8ft sheet is becoming a rarity as they’re fast replaced with 2 x 1m sheets that, on occasions, we’ve had to weld together to get a piece big enough for the job at hand – the top skin for the air intakes being a notable example.
Nothing daunted, Pete found us some long expanses of imperial material thirteen feet in all and, along with two cardboard tubes of extrusions, there arrived one day an equally long pallet containing the outer skins for our sponsons. And that’s where matters rested for a few years. We weren’t ready to build sponsons but whether or not we could was a problem solved. With that in the bank we went onto other things.
Roll the clocks forward to the middle of 2012 when we more or less had the main hull and systems nailed and the time came to revisit the sponson question.
We’re in the habit of bringing an area of the boat to a state where we know and understand it and have a feel for what it’s going to take to finish it then we leave it alone. The constantly shifting sands of the rebuild keep it interesting and morale at a permanent high as is the quality of the job, which, of course, has to be absolutely exemplary.
It was suddenly sponson time.
Another job we did many moons ago was to take the original drawings to our friendly, local laser cutters (who also happen to have a superb water-jetting setup) where we digitised and properly scaled everything in order to cut some tooling. We made it from the finest grade of 25mm plywood and cut it out with water.
Water-jetting is an amazing process using extremely high-pressure water mixed with powdered garnet to smash the material at molecular level. I’d seen a solid four-inches of 316 stainless sliced like sponge cake and slabs of hammer forged titanium cut into blanks for replacement hips as shards of lightning shot from the cutting heads and a water bath the size of a small swimming pool boiled above its bed of pure white garnet sand. So our plywood was cut like tissue paper.
The tooling was dragged from beneath the bench, dusted off and readied for action.
The horizontal part of the tool set up on the bench. Note the sweeping curve of the aft end of the sponson. The actual structure ends with that upstanding bulkhead you see clamped to the tool; the rounded end of the tool represents the thin-walled end-cap to be made along with the sponson tops. There’s also an extrusion lying along the right-hand edge – the one and only example that we didn’t have to form into exotic shapes. And that was the next problem – how to form the extrusions.
Now then… I am forever being asked about aluminium. It’s a mysterious substance that does all sorts of weird things when you leave it alone for a long time or heat it up or allow it to corrode and one detail we missed was that, when this stuff was delivered, it was heat-treated to a condition called T-6. Or, in plain speak, hard as buggery! T-0 is soft as butter and 6 is about as far as you can go. There was simply no way we were going to be able to work the stuff without it either snapping like a carrot or giving us a collective coronary from the effort needed to bend it so we had to get the fight out of it and to this end we took it to Bodycote in Stillington in Co. Durham.
Where the boss, Barry Mavin, agreed to take our extrusions and anneal and furnace cool them all the way back to T-0 and beyond.
“How soft do you want them?” he asked.
“Soft as you can make them,” I replied.
Hmmm. We maybe ought to have put that on a slightly more scientific footing because what Barry and his crew did was turn our 13ft angles into liquorice bootlaces that we couldn’t pick up in the middle without them bending under their own weight. What a hell of a job we had getting them home on the roof of our small van! This was not going to be a long-term problem, however, because that weird aluminium stuff hardens as fast as you bend it or even if you leave it alone for a long while, so the bootlace effect would wear off eventually but not before we got the shapes we wanted.
So… home they came and the next job was to find a way to bend them.
We decided to make a set of rolls especially for the job. It’s a simple principle. You mount a pair of rollers a short distance apart then fix a third above and between them that you can wind up and down. You also arrange a handle so you can crank round the upper roller to feed your material back and forth then you thread a length of material between the three and wind the top roller down to push a slight bend in it. Next you turn the handle whilst inching the centre roller downwards to increase the bend until you have the curve you require.
We found just the thing we wanted on t’ Interweb and the guys who’d designed it generously let us have the CAD files to cut the endplates because that was pretty much where we departed from a tool they’d originally designed to bend steel tubes.
Our sponson-extrusion rolling tool... Just building this was a major exercise but well worth the effort. The endplates were lasered from 10mm steel by our pals at MTechnic down the road, a thoroughly excellent company who also water-jetted the plywood for us.
The machining we did in-house, making the rollers from high-impact plastic with ball bearings at the centre. The centre carriage is moved up and down on a hefty chunk of M20 studding and the rollers are designed to bend bits of sponson and nothing else.
It worked brilliantly from the get-go and completely justified the thought and effort put into making it. We also had exactly eight extrusions from a requirement for exactly eight extrusions so we had to get every one right first time and could afford no waste.
And, lo… bending extrusions was suddenly simple – well it isn’t, actually.
You see, the problem is that, though it’s easy enough to bend it in one plane with the rolls, no matter what you try it’ll always deviate a little (in direct proportion to the extent of the bend you wanted) at 90 degrees the wrong way. What you then have to do is roll it again to eradicate the part of the bend you didn’t want, which then partially undoes the bend you did want so you have to increase that, which re-introduces the bend you didn’t want that you then have to get rid of all over again and so on. Now remember that the material had just been annealed to make it soft but that it rapidly hardens again when you start bending it about so you can’t just keep at this tooing and froing or you’ll end up back at the heat-treatment plant with a thirteen-foot aluminium scythe looking a bit of a plumb.
The answer was to push quite a severe bend against the direction of the unwanted deviation before pushing the bend we did want so the two cancelled each other out leaving only the shape we wanted. We got very good at this very quickly and it saved a lot of work.
We pushed the extrusions to somewhere near using some basic pieces of tooling with excellent results… The only downside was that they weren’t quite long enough so pushing the more extreme curves right to the ends was made difficult by running out of extrusion. We got it but it was troublesome.
Having proved out that process we then had to put some of the other componentry together before we could continue. Each sponson has a series of bulkheads down the centre with the extrusions let into the corners. The drawings called for joggled corners but the material spec called for nightmare-hard tin that hates to be joggled and, no matter how we tried to do it, it resulted in an ugly and inaccurate job. We decided that if we could use our laser cutting and water-jetting facilities then the bulkheads could stand Some TIG welding here and there in the interests of accuracy rather than the basic application of brute force and ignorance. We knocked up a small press-tool and made a stack of these things. Pringles, I think we called them.
Then we cut and folded a set of bulkheads and formed a hole in the middle using a wooden tool as per the 1954 instructions.
Next we deviated from said instructions by cutting the corners out and welding in a Pringle instead.
It was a lot of faffing about but by doing it that way we could keep the tolerances very tight. Then we realised that the table of sizes for the bulkheads actually included the thickness of the outer skins – something that wasn’t obvious – so it’s a good job we spotted it when we did. So we had to modify every single bulkhead… Never mind, do you want it now or do you want it right?
By now we were beginning to see something slightly sponson-like emerging and thus far it had been reasonably simple and straightforward. That was all about to change.
If you look carefully you’ll see that a couple of the small bulkheads up in the pointy end have been cut and welded back together. They were especially tricky to get right and it was simpler to cut and shut them than to make new ones. Once they were exact all trace of the mod’s was buffed away.
Once this got going properly we found that making sponsons could really only support two or three people because of the need to fully understand what was going on. We also found out very early in the process that making two sponsons at the same time only copied mistakes from one to the other. A far more efficient approach was to take one of them to a certain stage then use the experience gained to bring the other to a similar condition whilst applying lessons learned. It wasn’t the sort of job that could be handed over to the next person who walked through the door so small teams would take a part of it and make it their own and this often resulted in some of us being between jobs. So what to do as this process inched carefully forward?
Well… You know how all the tinware down K7’s left hand side survived because it got squashed against the frame and everything down the right got blown out in a shower of shrapnel never to be seen again? This effect manifested itself on the sponson tops, which are just big, empty voids made of thin skins with lightweight formers inside, by crushing the left one leaving it mostly floating on the surface with air trapped inside while the one from the right was shredded and scattered like a handful of leaves.
Scroll forward to 2001 and nothing makes a juicier sonar target than a big, crumply piece of tin so they lit up like beacons on the lakebed and were quickly hoovered up by the divers. They were brought home then carefully stored away under the stairs in the workshop soon to be forgotten. Another sizeable chunk was also left clinging to the front spar as it glanced off the water then hurtled on ahead and this was the only part showing above the mud and was therefore the only reason we were able to locate the spar. It too went under the stairs.
Then, one day, we found ourselves looking at a redundant sponson tool and thought, we know what we can do with that, let’s build a sponson top on it…
Here’s a more or less a complete sponson top with formers and a rather lovely end-cap that popped off in one piece… it was like finding treasure all over again and was set upon with great enthusiasm. First we mended the formers and popped them on top of the sponson for a look-see. This ends up being more spooky than informative usually.
There you go – three original formers. They allowed us to check back with the drawings to find out if they matched and therefore whether or not we could trust the drawings for the ones we didn’t have. They did and we could.
Next job was to clean and straighten some tin. This is the bit that went flying with the spar. Because the spar got shoved out to the right it went straight through the sponson top like a cocktail stick through a pickle and speared this part well and truly. Only a few shreds clung to the other end but we’ve saved them all the same.
It took some sorting… We knew what it was and what shape it was supposed to be but it had been unfolded from the inverted ‘u’ shape it once was then formed into an other ‘u’ shape with its spine at ninety degrees to the original – very confusing!
It’s the forward section from just behind the upper nose of the sponson, where the front spar passes through. See the cutout for the spar.
And from the other side…
If you look carefully you can just see the little raised oval bashed outwards from the inside to clear the end of the spar. Its still there and was the main feature that allowed us to work out how to put the thing to rights.
Then there was the pair of pieces seen below. Originally one part but now torn roughly down the spine and with most of their shape blasted out.
We cleaned, mended and glued them back together but first we were able to retrieve some priceless historical data and interesting artefacts like the A from ‘DO NOT STAND HERE’ that was painted on the flimsy sponson top.
And the remains of the arrow that once denoted where not to stand seen here pointing to the right with its point missing.
Those pieces are carefully recorded and put away against the day when we need to put those features back onto the finished boat. Then we got the rest of the paint off and went about the serious business of mending. The material is deliciously soft and simple to work with. It just pushes around with a hammer. For example, we had to shift a massive stretch at the front edge of a seam so we pulled the edge into a series of tucks to get the radius closer to what was wanted then stuck a patch of new material ahead of it.
Next we spot welded the bottoms of the tucks into the patch.
Notice the difference in height between the patch and the metal behind the tucks. But that metal now has nowhere to go. It’s trapped and that’s the secret of shrinking metal – give it nowhere to escape to when you hit it. After some light tapping to get the height down to about half what it was the joint was fully welded.
Then the welds were dressed back with a die-grinder and the excess metal shrunk back into itself with a hammer and dolly.
Much better – just needs a round of fettling and filing and it’ll be good as new.
Some parts we didn’t have, like the very front section so we made one of those from scratch. It was only supposed to be a piece of tooling but it turned out OK so it was fettled into a useable part.
And finally we mended the end cap and wheeled a new section to fill in the gap.
It’s very much still a work in progress but we’ve basically sorted every shape and how to make a new one for the other side so now this job is parked again while we do the final fix on a real sponson that we can use to do the final fix on its sponson top.
Here’s the other sponson at quite a late stage of construction.
But this is where it got difficult. The sponsons have to bolt to the spars but good old Ken and Lew were hedging their bets with overall weight, balance and buoyancy of the machine so they designed a means to move the sponsons fore and aft through three positions placed nine inches apart should this prove necessary. As it happened they soon discovered a tendency for front-end heaviness so the sponsons went as far forward as the design allowed and remained there throughout the life of the craft; but the alternate mounting points were all in there, redundant but contributing weight and considerable strength to the overall design. Nothing else for it, we had to follow.
The ends of the spars taper where they bolt into the sponsons so they mount onto the tops of a choice of three pairs of frames spaced more widely at the inboard side of the sponson than at the outboard. Nor do these frames have folded over flanges around the outside with Pringles welded into the corners because they’re made of even more ridiculous, Californian alloy that bends through 90 degrees about as well as a digestive biscuit. Instead, they rivet to the extrusions with attachment angles that, because they fit to the insides of the extrusions leaving them three-sixteenths of an inch short of meeting the outer skins, then need a packing strip to make all the material thicknesses correct again. The result is six frames at each end to pick up the spars with each frame comprising nine separate components and an extra frame at the back for luck making seven in total – one frame having four attachment angles and four packing strips – every single part fabricated to fit at a peculiar angle because the frames taper towards one another to pick up the spar whilst having to fit within a constantly changing shape at either end of the compound-curved sponson.
Now for the tricky part – they were never drawn.
Yes, all you get on every drawing is a position for where they go and a material spec’ but beyond that you have to make it up as you go along. I’d bet there was a big litter bin in the corner of the Norris Bro’s. drawing office into which went a few attempts at working out all the angles and dimensions before they simply drew a big space and said make all those bits fit in there and fill any large cavities with ‘Loy’ filler when you’re done. They knew what it was going to be like.
I’ve long had a theory that Bluebird’s ‘tramping’ was the physical manifestation of her misshapen sponsons fighting one another for equilibrium and the more I see the more I think that’s actually true.
Here you can see how it all goes together. See the spar frames, their corners dressed to clear the extrusions and their attachment angles carefully fabricated to precise angles to mount them. Then notice the packing strips lying on top of the attachment angles but between the extrusions to bring the stack-up heights back to where they need to be to allow the outer skins to be riveted flush.
Here you can see the aft-most spar frame mounted within a section of the sponson that tapers both from left to right and top to bottom. The frame is also angled relative to the sponson centreline so it has to be taller on the left then on the right because its end lands under the extrusion further up the hill on the left than it does on the right. And no two of its attachment angles or packing strips are the same either.
Now we could have modelled all of these parts and had the frames lasered at least but that would have been as much work as cutting them out and hand fettling them – something I think folk sometimes forget.
It would be a different matter were we running a few of these off and could afford a throwaway prototype or there was a possibility of future orders but these are very likely to be only the second pair ever created in the history of mankind so there’s a compromise to be reached between investing in design, manufacturing and tooling and the fact that it’ll only ever be utilised one time. At the end of the day it comes down to an economy of tooling, extreme care in the build and the MKI eyeball.
Eventually we got there and a full kit of sponson parts amounted to about 180 separate components.
As ever, Bettablast painted everything horrid green…
Notice that the packing strips are drilled in the middle so they not only take up ten times more width than they would have if they’d been drilled at one end but they spun like windmills in the oven so they had to be kept even further apart. We were popular for taking up the whole oven unnecessarily. They looked good when they came out, though.
Then Mike landed the job of sorting them all into kits of parts, fortunately they were all carefully stamped so putting them into sets for the next phase of assembly wasn’t too tricky and a good opportunity to give the next generation some early training in the way of things.
It then didn’t take long to put it all together with pins and have a look at the complete structure. To this point we’d completed a section then deburred all the bits, stamped them so we could work out which was what then bunged them in a box ready to go. It was only when they all came back that we got to finally put it all together.
A work of art…
Now we could assemble complete spar frames for riveting…
See how it works? The frame is a flat plate then four angles fix to that, the verticals on one side, horizontals on the other. And finally a packing strip is fitted to fill the gaps between the extrusions and bring the outside of the frame flush to allow the outer skins to be riveted on. But look how cluttered and fussy it gets at the back and imagine trying to get that little lot all true and square and to dimensions that aren’t even provided.
One of the extrusions has been removed here so we could load the frames starting with the rearmost. The front spar frames are just as complicated.
It’s little wonder that these things laughed at the crash. They are incredibly tough yet one person can still lift a whole sponson. They’ll put on weight when the outer skins are fixed and I recon by then it’ll be a struggle single-handedly and it’ll definitely take two once the planing wedges and shoes go on because, of course, the upper structure is only half of the story. Its purpose is to mount the surfaces on which the boat will actually run over the water and they are a different matter altogether.
To the underside of the sponsons is fixed two great slabs of aluminium. The forward, sloping section has what’s called a ‘shoe’ attached to it whilst the rest is covered by the ‘float wedge’.
The shoe is about an inch thick at its inboard edge and a bit less at the outboard edge. The idea being, presumably, that any water is thrown away from the machine and the inner edges of the shoe act somewhat like a keel. It seems that neither design objective was ever met, though, because a plate was added later covering the shoes making them marginally wider whilst incorporating a folded down blade along the inboard edge. We’ve not looked at that modification at the time of writing.
The wedge is exactly that – a six foot long wedge machined from a solid block of aluminium. Where shoe and wedge meet they form a step like that under the F-19 bulkhead to break up the water flow and introduce air to unstick the wedge from the water.
Now here’s the problem. What can you think of that has a 6ft long machined part in it? Certainly not your car or lawnmower or microwave oven – more like an aircraft or a submarine, something that maybe a government or aerospace contractor might ask for, not a gang of volunteers with an old tin boat. What we needed was a slab of metal six feet long, fifteen inches wide and seven inches thick and a machine big enough to swallow it whole and cut it to shape. Rolls-Royce sprang to mind. They make lots of big bits and we’ve always enjoyed excellent relations with them despite the fact that they never could officially help us. We thought of Vickers or BAE or whoever they are these days because they are rumoured to have made the originals and may have been tempted into a second pair for old time’s sake but, then we started asking around the doors and the name MKW came up.
Who? Having worked in engineering on Tyneside for many years the name rang a dim and distant bell but our paths had never crossed yet now people were telling me about satellites and wind turbines and CAT scanners being made just a few miles up the road. They weren’t kidding! We had a genuine defence contractor making things to go into space at the end of the road. I felt like growing a big pair of stupid ears and making donkey noises but it seemed a better idea to say hello and ask the question.
I called the boss man, Michael Wright, and asked nicely whether he and his company would be interested in helping out. We were soon graced with a visit by Michael and MKW’s chief commercial man, Rahmon Nassor. Michael seemed quiet and thoughtful while Rahmon made us laugh with his quick wit and dry humour. All we could do was show them around then wait to see whether they’d help.
The answer came some days later and negotiations were opened. Whichever way you look at it, it was a big job. To take the old drawings and pull them into a CAD model would be time and labour intensive. Then to turn that into a program to cut the metal and get it right in one go represents another big effort. Running simulations to check the various operations and tool-paths to eliminate potential catastrophe would take time and care too and that’s before a skilled operator at the helm of a half-million-pound machine could be handed a block of metal and given the green light; but eventually, and to our great joy, they agreed to help; but it all depended on us being able to get hold of four big lumps of material – two for the wedges and two for the shoes.
We agreed to get onto this problem straight away so, in the meantime, the CAD dept. at MKW got on with the computer work and soon we were watching computer simulations of our wedges being machined.
Piotr – or, as he’s affectionately known to his mates, ‘Peter the Pole’ showed us just exactly how the big machine would cut and curette the unwanted swarf from yet to be formed cavities in our wedges whilst the programmers and I went over the drawings trying to second guess the parts that Norris Bro’s. had conveniently ducked.
This was all jolly wonderful but at this time the big chunk of ally that their program was cutting like crazy only existed in cyberspace. It was time to go back to our old friends at ThyssenKrupp to try and acquire the thickest slab of tin any of us had ever seen.
Put simply, this was beyond the boys and girls who supply our regular sheets – way beyond. The question of suitable material had to climb higher, then sideways to a different division, and once again we traded. We supplied a box of goodies to auction for their chosen hospice charity and, in return, we got an excellent deal on our great slabs of metal.
On the left are the two chunks for the wedges one atop the other with the billets for the shoes on the right. Each one of the wedges weighs 350kg in this state but most of that would end its days as swarf. The delivery ticket says it all.
There you go – take a look at the dimensions of the things! And it’s not just ordinary aluminium either. It’s near as makes no difference the exact, modern day equivalent of the original Birmabright BB5 with the same heat treatment. Spot-on as ever.
Now all we had to do was get it to MKW and wait for some down-time on their machines because, as usual, this was the deal. It’s one of the main reasons that we cannot possibly say when the job will be finished. When will our benefactors have down-time on expensive machines into which they have invested many millions of pounds when down-time is the very last thing they want or need? Christmas proved the answer and one day, Rahmon called to say we had a slot on the big new Mazak machine – we dashed up there to see the first cutting of the metal. The first, K7 planing wedge in over half a century was about to be born.
As yet untouched – a solid lump measuring 6’ x 15” x 7” and if you don’t know what that last bit means ask your dad.
John, the machine operator, soon had it clocked in then the programs so carefully designed by the CAD dept. began to run in sequence to cut a planing wedge from the billet.
Sounds easy, doesn’t it. The reality was sixty hours of machining and that’s without programming and simulation time. How do you say thanks for this kind of support? Nothing ever seems adequate.
The machine munched and munched until the difficult part was finished.
This is the part that’ll never been seen – the side that bolts once and for all onto the underside of the sponson structure. The holes serve to both bolt it down and to get some weight off it. There’re a couple of dozen fixing holes then over 450 lightening holes, no two of which are the same depth. The side walls are only 3/32nd of an inch thick and the lower face only a quarter inch.
From here they went onto the machine the other way up to have the wedge-shaped profile machined. The machine has a 6m bed yet the smallest tool it can handle is a dental burr!
An almost finished wedge with the shoes in the background. There’s only a few more op’s to do on this one at the front where it meets the shoe. It’s also worth remembering that the originals weren’t made this way. The technology simply didn’t exist. These would have been literally months of work for a man in a dust coat and a big, hand operated milling machine.
The shoes are a similar thing of beauty.
Once again, cut from solid lumps, and notice two things about them. One, the slight difference in thickness from inside to outside. Here they’re stood in their correct relative positions to one another. The second point is that the pair of ribs one up from the bottom are angled towards one another – this is so that they lie along the lower faces of the foremost toast rack and can be bolted into the spar frames. It’s a gorgeous design and brilliantly executed by MKW.
There remained only one test – to see whether the sponsons, built in our workshop by amateurs, mated to the shoes and wedges made off-site by aerospace and defence contractor, MKW.
To be continued