Some of you just aren’t getting this, are you? OK – let me explain. The thickness of our tinware is measured in Standard Wire Gauge, or SWG for short. All of our bolt fixings are either BA or UNF. Our material spec’s are to DTD or the old L-standards and our rivets are in sizes ranging from 3/32nd of an inch to 5/32nd. Our aeroplane was built and then forcibly dismantled again in 1940s Britain and in attempting to un-crash it we must effectively transport ourselves back to those times and work with the numbers, tools and traditions of the day. That’s why our gear comes from the shed-bound tool boxes of long dead old boys via eBay and we’re having it built by girls while the men get on with the dangerous stuff. And, in keeping with our recreation of the war effort, your contribution is also needed and top of the list is that you stop calling our diary a ‘blog’.
Blog is the sound you make when your head is so full of snots and cold that you can’t speak properly and is less a word than a rather vulgar noise.
This is a bloody diary! OK?
Hopefully you’ve got it this time… so where were we?
We’d stuck a skin back onto the outer extremity of our tailplane, or as I heard it referred to the other day by a proper aeroplanologist, a ‘top slab’, but again it was a cheat because that skin hadn’t really been crashed because it was stuck to a big chunk that broke away intact. The next skin inboard from it was properly hacked at by the bread knife, though.
Bit of a bad do – sliced right through the middle and with bits missing. The splits were easily mended. Just a good clean then some hot metal glue.
Cleanliness is everything when you’re mending this stuff. It needs an awful lot of kneading after the welds go on to make sure you have one, homogenous piece of tinware and the slightest inclusion or impurity will cause it to crack straight away once you start working the metal, which is partly why we called time on working the night-fighter leading edge and gave it to Elvis. Not so this time – we’re honing our skills.
But mending the outside skin was only half of the problem. There remained the small matter of the gaping chasm inside where all the stringy-ribby stuff had been scattered to the four winds.
The bread knife made short work of that little lot. It must have gone through the paper-thin structure like it wasn’t there and of course it’s all needed to support the correct shape. Working with it in that that condition soon becomes a dull ache in the testicles because every part relies on every other part for its strength and matters deteriorated badly once everything was smashed in two leaving the severed stumps flapping about. It took a bit of a while to put it back using salvaged bits of this and that from other Barra’ tails but to our surprise it looked pretty good when it was done and the strength gradually crept back.
All we had to do then was mend the outside, rivet it on and the job was a good-un.
Gluing the halves of the skin back together was straightforward but inserting the missing pieces did all sorts of peculiar shrinky-type things that took some putting right (we expected that and have an evolved plan for next time) but it came good eventually.
What seems to work nicely with this material is to dress off the welds once complete then wheel a soft crown into the repaired area. What that does is stretch the metal making it a little thinner but also a uniform, smooth shape. The other effect is a gradual work-hardening but that’s not a problem because the trick is in then heat-shrinking it back to flatness, which anneals and thickens it again whilst effectively kneading the welds into the native metal until it’s as though they never were.
Trouble was, we couldn’t really fasten it on because it pretty much closed off access to the aft mounts where the tailplane bolts to the sticky up bit and as each of these comprise about fifty pieces, forty of which aren’t needed and all of which have been in a crash, we decided to build them first.
Here’s one and it’s ridiculous, it really is. It could have been built with half as many parts and still be unnecessarily complicated. On the plus side it’s bloody strong despite all its mistreatment. Every part has been completely stripped, blasted, etch-primed, painted silver then reassembled. The bolts are new but that’s the only concession and if we’d been able to salvage an original set of bolts they’d have gone back with it.
There’s a small plate that joins the left and right inboard skins that also closes access to both mounting points so we had to build the pair before the skin could go on.
With the mounts nailed on, Lou and Gillian soon melded themselves into a formidable riveting team and the boys were chased out of the workshop for the rest of the evening while they carried out a conversation through a sheet of age-old ally to the rhythmic hiss-pop of the rivet gun.
One interesting side effect of the soft condition we’ve reduced the metal to is that even the softest solid-rivet remains way harder than native Baddacooda so in certain conditions using them leaves you with more of a deep-buttoned sofa than an aeroplane. So there’s rather more blind rivets than we’d envisaged but the suggestion that we heat treat all the parts before assembly to restore their mechanical properties thus allowing meticulous use of the correct rivets wasn’t met with whoops of delight by the museum’s chief in charge of purse strings.
Nonetheless, the result was pretty good…
Nowhere near as glamorous but equally dedicated, Al and Tony (another of our long-term Bluebirders) steeped and soaked all the monkey bars and tailwheelery in the caustic bath until the whole inventory was muck and grease free.
With it all cleaned we were about to mix up some molasses moonshine but for many years we’ve enjoyed the most amazing and dedicated support from Chemetall Trevor.
Trevor brings mystifying chemicals for us to try out, the most famous of which is our Harry Potter paint stripping bath that never runs out or stops working. Those of a Bluebird disposition will tell you that we’ve been raving about it for ever – because after eight years it still hasn’t stopped stripping paint. That just isn’t natural, is it.
This time Trevor brought us a pot of something that is supposed to vanish rust just as effectively as molasses but without turning our workshop into a Mecca for every wasp within a hundred mile radius – summer is on its way, after all.
As a minor aside, I once did the factory tour of the place where Malibu is made. It’s in Barbados beside a beautiful beach and, open-topped in the blazing sunshine, is a tank of molasses about forty feet across and tall enough that you have to climb a flight of metal stairs to get up for a look. The brown, syrupy gloop is mechanically stirred by a rotating blade but it goes slowly allowing literally million of hungry insects, who probably think they’ve alighted in bug Nirvana, to land undisturbed on its surface only to be folded into the mix by the passage of the blade moments later. Next time you have a Malibu and Coke check the bottom of the glass for bluebottle carapace…
We’ll report in due course on how the Chemetall chemical cocktail works on our rust but in the meantime this is the sort of thing it’s up against.
Meanwhile, we kept adding bits to the tailplane.
Hayley has almost finished her formers for the leading edge.
Having riveted everything together she was doing some working out for a series of triangular cutouts in the sides of the formers where a stringer passes through. They don’t appear on our drawings but they are definitely cut into the few original parts we have from that side and the stringers were recovered from the wreckage too so Hayley modded the parts accordingly but when asked how she’d worked out the positions she just looked at me as though I were stupid, did a spot of origami with her drawings that I was supposed to follow, and said,
“It’s easy, it’s just like a dressmaking pattern…”
Yeah. I nodded in fake understanding and went off to find something manly to do that her girly brain couldn’t hope to comprehend. Some hope of that!
Aerospace Rob has been busy too. There’s about a thousand million rivets to sneak in here and there holding parts that clearly weren’t needed for anything, but the heads are visible on the outside so there’s no point putting the useless pieces in the bin if they’ll go back on the inside so Rob has been methodically working his way through the snagging – all eighteen feet of it. That’s feet as in metres, a bit like diary as in blog.
One of the later pieces to go back on was the front mount to go with the two at the back to complete the set.
Now then, boys and girls, study the above picture carefully and put up your hand when you think you know what we did next.
Yup – we just had to spanner it all together to see what it looked like.
There was a little more to it than that. You see, when we took it apart, much of the mounting gubbins had shims here and there to take up slack clearances but it could as easily have been the other way with something too tight to assemble and we’d rather know now than after all its clothes are on so up there on the end of the sticky up bit it went.
No problem at all.
With the barest tickle of the rubber mallet all the fixings glided smoothly home and we had a complete Barra’ tail.
That’s going to look rather good with a coat of paint (and no filler). There’s some nice little fairings to close the gaps where vertical meets horizontal and they’re very squashed so they’ll be a delight to mend in due course but in the meantime we had to take it all to pieces again because it just took over the workshop and when we threatened to turn it through ninety degrees and double the rent the FAAM thought we ought to dismantle it too.
Just the outer skins to stick back on now so we can safely sign off for March in the knowledge that, although there’s still not a whole Barra’ in the world yet, at least there’s a tail.
We’re off to the museum next week to kick through the drifts of crashed tin in search of fuselage bits. The big tube from where the gunner sits to where the tailwheel goes is the next piece to tackle and we want to start pulling it down and cleaning parts sooner rather than later because we know what we’re doing now (to a large extent) and reckon we can time finishing the tail with starting the tube.
It has to be simpler than the tail too.
’til next time…