Thursday, October 6, 2011

Running Away to the Air, 5: Wooden Wings

Have you ever been told that "The wings of the Spitfires that won the Battle of Britain were made of British Columbia spruce?" Probably not. Chances are, you're not British Columbian. It's untrue, but you might have been persuaded by more plausible versions,such as that it was the Hawker Hurricane or De Havilland Mosquito. (And you will have heard stories about this.) Actually, BC's aeronautical-grade lumber was staked in a frenzy of ration allocations in 1942, and went into machines like this and this.  But who wants to hear that? Certainly not anyone who has ever lived north of the Skookumchuk.

Because you've felt the November rains.

And you've gone out to the cut blocks in old crummies smelling of wet rain gear. I remember being told, rather arrogantly, in Toronto in the early 90s, during one or another manufactured standoff in the woods, that my interlocuter would prefer to see Vancouver Island evacuated and turned into a nature preserve.

(The scenery isn't from Vancouver Island, but it is authentically straight out of the cutblocks, so here's the Be Good Tanyas again illustrating the point.)

It's because there's just not a lot of people out there (some half million, but far fewer than that on the northern half) and a great many trees. Old time boosters used to dream of integrated regional development, that the sawmill would bring houses and schools, and hobby farms, and garages, then real farms and factories; finally a Gothic city hall and a militia regiment and a university and a cathedral.

It didn't work out that way. Perhaps it might have. Perhaps it was starting to happen in the 1920s, but then it stopped, sometime in the 1920s. Some mills still run, but they shed more jobs all the time. The rest have shut down, sweeping their towns away with them: Ocean Falls, Gold River... Sometimes the community fails, sometimes it doesn't. People have to live somewhere.

It's like history reached just so far, like the tide.  So it's some consolation that we floated out a few wooden wings before it was too late. Does it matter whether it was for Spitfires, or Hurricanes, or Mosquitoes, or these? They all played their part.

I almost gave up on this post. We've past the anniversary of Operation Typhoon, and all the old German excuses about the quality of Russian roads are being dredged up again, as though "we couldn't campaign" is an excuse an army can use. So I thought about writing about armies, and roads, and pavements. But I wanted to check whether I've used some of my quality anecdotes already. Besides, this morning, a CBC sportscaster talked about wooden aerodynamic test models of the Avro Arrow: wo Canadian patriotic urban myths in one. And on top of that, going through my notes on the wartime run of Aviation, I came on one of Robert Neville's editorials from the fall of 1944, patiently explaining why the rapidly rising national debt didn't portend a postwar apocalypse, that the crucial thing was maintaining economic growth, not stringent austerity.

Now, you've never heard of Robert Neville. He certainly doesn't have a Wikipedia page. He's just a former editor-in-chief of the McGraw-Hill stable of technical monthlies who cranked out wise, thoughtful editorials each month for many years. Now, he's gone and forgotten, and the same things still get said, again and again,   into the same dull, uncomprehension. Thinking about Robert Neville is a reminder, if a reminder were needed, that people have been patiently saying wise and sensible things for many years. And that we've been ignoring them and substituting our own preferred narratives.

For example, that the RAF somehow "forgot" that you could make planes out of wood (presumably over five years in the late 30s, because allegedly in 1932 it was still building wooden planes indistinguishable  from the aircraft of WWI), and was blindsided by the wonderful Mosquito when it appeared out of nowhere in 1939. It's not true. And not true in a usefully informative way.

The brand-new RAF ended the First World War with an enormous quantity of aircraft, spare parts, and continuing  production contracts. This was good, because the RAF was supposed to be doing its share of global euphemising duties. There were a great many out-of-the-way places needing a good round of euphemising, and, amazingly enough, not many  bombers with which to do it.

Or not so amazing, because the Air Officer corps consisted very largely of old artillery men who saw exactly this coming. It wasn't about the planes, any more than it used to be about guns. It was about getting the weapons where they were needed and keeping them working once they were there. It was about technicians and storage facilities and transportation and workshops. As a means to an end, planes made out of wood didn't make any more sense than caissons made of wood used to make. Wood rots when it doesn't suddenly crack and splinter.

Against this, you can offer two main arguments. The first is that wood is actually quite strong for its weight. But this is actually quite a weak argument. Good quality wood, well-assembled, is quite strong for its weight. And if money is shorter than planes.... The second argument is that wood is very cheap to assemble into structures. Insofar as assembling a workshop, this was obviously true. The machine tools that one needs to work on wood do not have to be very powerful, and this in turn means that they can be quite adaptable. Someone might lose a finger, but, in general, there's a lot you can do with a table saw. By someone who is quite good at using a table saw, that is.

And yet... You can actually buy metal in much the same way as you can wood. Or, actually, in more ways, because metal is cast in molds, rolled in rollers, stamped in hammers, and forged in dies. Wood grows on trees and gets milled into planks, boards, and sheets. The steel mill can supply you with the same, and throw in (cheap) bars and angles in the bargain. So if you want to drop the cash on tools that work metal the same way that a woodshop's tools work wood, you can do pretty much the same things with metal as you can with wood.

And so that's what the brand new Air Ministry asked for in 1920. The same planes that it already liked, just made with metal instead of wood. Obviously this wouldn't change their looks any, because the planes were just space-frame structures faired with doped cotton and rigged with external wires and struts. It might improve their structural strength, but, in 1920, the Air Ministry had precious little ability to actually measure such things, anyway. Doing that sort of thing was definitely on the table, but, in general, what you did was hang sandbags off the edges and corners of a plane until you were confident that it wouldn't fall apart in mid-air. An SE5 or a Snipe or a Brisfit that had had its internal frame of wood replaced with an identical one of metal might be heavier as a result, but you could always shave down the metal bits until the weights were comparable, and if it took as many sandbags to make the frame flex as before, that was fine with everybody.

And if that sounds crazy, bear in mind that thousand-hour pilots were, in general, fantasies of things to come. A short-service RAF pilot could expect to go up in one of these things a few hundred times at most, always in one that someone else had flown before. The crazies who flew newly-delivered planes for the first time are the heroes of early British service aviation. You can read some of their spectacular stories here: and in general here. Bullet point summary: these guys were very good at getting themselves out of trouble in mid-air.

So the 1920s went on, and the British aeronautical design firms got more sophisticated in line with rising performances. The shops that survived into rearmament added, by slow increments, more expensive equipment: furnaces, ovens, forging presses. The first naive and sometimes disastrous experiments with metal-skinning, driven as much by lack of aeronautical-grade long-staple Egyptian cotton as anything else, gave way to partially-monocoque structures with carefully-analysed webs of braces and struts that allowed thin and light skinning that resisted twisting and shearing forces without external wire braces. It's all very interesting if you're into doing fairly complex engineering math without a calculator, and Lutz Budrass has actually worked on the subject, bless his soul.

The skinning issue raises an important issue. I've hitherto been somewhat dismissive of the idea that wood has remarkable virtues as an aeronautical material. In general, we're going to need to build back to this point.  But this is certainly not the case for substituting plywood for metal skinning. You don't have to have a particularly good-quality plywood to have a better rigid aerodynamic fairing material for lifting bodies than metal. In fact, long before certain writers got it in their heads that wood="backwardness"="British," the more common complaint in the trade journals was that British aviation safety regulations weren't permissive enough of the new plywood grades that were, in fact, rapidly changing the nature of the product in these years.* (I think that the complaints that I'm vaguely recalling appeared in The Aeroplane rather than in Flight, conveniently saving me the trouble of searching them out in the online resource.)

But, to take another tack here, there was an overarching concern here to constrain the Air Ministry. Skilled hands make planes. And, as Hugh Tenchard saw so clearly, the industry was only going to expand if the Air Ministry produced those hands. So the technical future of the RAF went back to RAF Halton's Number 1 School of Technical Training. The concept was very simple. Boy apprentices would come to RAF Halton and enjoy a subsidised education leading many of them into the air force. The remainder, and all retired LACs, would go into industry. All that the Air Ministry had to do, then, was persuade parents to deposit their tow-headed boys in the Ministry's tender hands.

It's interesting, I think, anyway, that at the time of the first Entry, the Air Ministry was dividing the boys up into "fitters" and "riggers." "Fitter" is a Britishism for "mechanic," and that's practically all that you will see in the short British Pathe film linked to above. It makes sense. Although the Air Apprentice programme soon started producing electricians and instrument makers, engine maintenance dominated air maintenance. And, of course, there were lots of jobs for "fitters" in civilian life and industry. (A word of advice from personal experience: don't eat at a restaurant that employs a cook that's been through the Air Apprentice programme. There might be a reason that he's a short order cook instead of working in industry.)

But what about "riggers?" Imagine --and I'm pulling this out of my ass in terms of understanding how the RAF came to use these particular labels-- a Napoleonic caisson bogged down by the side of the road with a broken spoke. You have two problems here. One is that someone is going to have to "fit" a new spoke into the wheel. The second is that someone is going to have to "rig" up some kind of arrangement to unweight the tire so that the fitting can be done. I've seen countless pictures of rigs of this kind, although I still haven't found an Internet source. (Look here for some nice reproductions if you can get to the library.)

None of them survive today, of course. That's kind of the point of "rigging."  It's inherently temporary and requires regular maintenance. The most permanent object I can think of that might be built (in part) by a rigger is one of the old-fashioned floating military bridges that has to be flexible in one place and rigid in another. Given that the RAF ultimately evolved out of the ballooners of the Signals Corps, and thus in turn out of whatever lost-in-the-mist-of-time corner of the British Army gave birth to the ballooners, this might be the direct line of descent. Or not. The early aeroplanes, with their wires and their sheets of shrinking and stretching doped cotton over wooden structures, required careful attention from riggers.

Now, I'm fascinated by riggers. I was honestly not even aware of them as skilled workers until I ran into a Handbook of Rigging in the engineering section of UBC's old Main Library. (Remember when you could go into a library and just look at books? You don't? You young punks today.) It was written as a textbook, although who might take a course in rigging I do not know. The Wikipedia article tersely informs me that rigging is an industrial activity involving ropes and cables and stuff, that it originated with sailors working the rigging (although in reality the actual "riggers" were old sailors who did their work in port), and that it's one of the few industrial occupations still taught entirely by apprenticeship. The link to a trades training site from the article is dead, and that to the ongoing National Geographic series on large rigging projects suggests that it has a pretty low profile for a reality tv show. Overall, the impression one gets is that, as an occupation, rigging chooses you rather than you choosing rigging. If I'm right, it's a social trick that preserves jobs for father's sons while making sure that rigging is done safely and for high pay rates.

But that's not the kind of "rigging" that was taught at RAF Halton. By the 1920s, the word had come to mean carpentry on planes. Here we see the inherent problem with an Air Apprenticeship scheme. It's not enough for the Air Ministry to articulate a need. The parents have to be persuaded that this is the right course for their children. And, as it happens, they did not see carpentry as a future for their children, and Halton could not recruit enough young riggers.

The panic of rearmament changed things slightly. Several wooden aeroplane projects were pushed ahead. I've already noted the Avro Anson, but its main wartime role was as a navigational trainer. That doesn't require performance, just a nice, large, reasonably quiet cabin with a window. There was an attempt on a wooden bomber --in the sense of using cheap and relatively "high-performance" plywood skinning, with even more innovation in the form of a tricycle undercarriage-- and an even more tentative try at a fighter.

And then there was the Mosquito, and it turned out that everyone was wrong, right?

Wrong. It's interesting to note that attempts to copy or reverse engineer the Mosquito failed in both the United States and Germany. There's even a question mark hanging over Canadian-made Mosquitoes, although I've never heard anything bad about the Australian version. This is because wood, used in this way, is anything but an easy material to work with. The main structure of the Mosquito was a shell of 0.427" balsa (a South American tropical hardwood) sandwiched between 2 0.062" 3-ply spruce or birch plywood skins. Balsa can vary between 5 and 30 lb/sq. inch, so careful timber grading was a must. The glue used was in part an organic material, casein, hot-pressed in forming presses to shape the pieces; in part a synthetic resin. Reinforcement was by stringers of either shaped composite, or particularly strong hardwoods. Highly stressed portions were padded with an early plastic, Bakelite, reinforced by fabric. Five-ply spars were reinforced by stringers made of an actual B.C. product, Douglas fir. Although there might have been Scottish Douglas fir plantations  by this point.

The things that stand out here are the use of very large, very thin veneers, and the complex composition of the actual composites made of this veneer. Part of the Mosquito, a good part of it, was made of wood. But of wood products that could have never existed without cutting-edge (literally) machine tools --the great planers that made these veneers. And part of it was made of plastic. If there was one word a young man needed to hear in 1940 about the future, it was "plastic!"

So here's the thing: the Mosquito was both made of wood, and a highly complex, even futuristic design, pointing to a distant future of military aircraft made of carbon fiber composite materials. (Again, literally!) It's an interesting example of the feedback between social, industrial, and military change. Whatever other technical and strategic factors were in play, in peacetime, the RAF had to move away from wood. Society wasn't interested in training carpenters to the skill-levels needed anymore, and in the absence of such skills, it didn't make sense to send wooden aeroplanes off to the frontiers of empire.

But who is to say that that loss of interest isn't linked to those same technical and strategic factors? My gut hunch is that it is up to institutions such as the Air Ministry to see these trends and drive them; and that is why its 1920 decision to abandon wood was right, while the detractors who demanded that plywood be given one more chance were wrong. War changed that calculus; but in the end it did not change it in terms of retrogressing aviation manufacture to the plywood-and-steel-spar age. It pushed it forward onto the threshold of the plastic age.

If you've noticed, I think that war plays a special role in driving technological change. I'm going to throw it out there that the reason is that it is so largely agonistic. Many considerations kept the Air Ministry from ordering Mosquitoes in peacetime. In wartime, all that mattered is that they promised to be faster than German warplanes.    

*T. M. C. Wegener, “European Progress in Hot-Press Bonding of Plywood in the Last Ten Years,” Trans. ASME 60 (1938): 69–76. There are good reasons that so many of my footnotes are concerned with plant-derived industrial materials.

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