We made the fabric for the fuselage some while ago, but today I’ve been fitting it, using the lacing hooks I attached last week.
We’ve also modified the arrangement at the bottom of the ply cover.
Originally the plan had been to extend the ply to the bottom edge of the top longerons and fasten it to the fuselage frame using little brass screws which passed through the lacing hooks, doing two jobs at once. The downside of this is that if we ever needed to remove the ply cover we’d have to unlace the fabric as well, and that’s something one doesn’t want to do unless it’s absolutely necessary, since it will shrink as soon as the tension is taken off it, and you won’t get it back on again…
The drawing isn’t absolutely clear how the bottom edge was done, but by referring to the parts list, we’ve established there was a separate fabric edge strip, and the photographs clearly show a piece of half round wood as well.
So we made up a strip of fabric with lacing hooks in it, and shortened the ply by about 15mm. The fabric strip is now glued to the fuselage frame, and in fact the lacing hooks have been screwed to the frame as before, while the ply is attached with another second row of screws that go through the half round wood moulding you can see in the picture. The result looks just like the photographs, and is also more easily removable.
I then stretched the fabric over and fastened it using the lacing hooks all round, and the result is very satisfactory, as you can see. It seems a little tighter than I’d remembered from before, but should be okay, I think. There are a couple more leather patches to go at the bottom front corners, and the front edge lacing hooks will have to be fixed on, but that’s a job for next week.
We’ve been puzzling for a while about how the fuselage fabric is attached to the ply cover.
The bottom edge of the ply has to be fastened to the fuselage longeron, and you also need the hooks to which the fabric will be laced.
The photograph from the parts list shows some reinforcement – probably a piece of half round moulding – which doesn’t appear on the parts list.
A photograph, either of 1263 or 1264, shows the edge reinforcement and the fabric lacing.
The reinforcement wasn’t shown on the parts list, and we were a bit puzzled about how to (a) fix the ply to the fuselage, and (b) attach the lacing hooks.
In the end, I decided to use little no. 3 brass woodscrews through the centre of the lacing hooks which would do both jobs at once, which they did, but we were left with another tricky problem. If we ever wanted to remove the ply cover – to get access to the petrol or oil tanks or the pipework and valve actuating linkages for instance – we’d have to unlace the fabric before taking the ply cover off. This is something to be discouraged, because the dope will continue to shrink the fabric throughout its life, and if you leave it unlaced for 24 hours, you may never get it back on again!
So I took another look at the drawing.
This showed that there was a part 17 – edge strip, and when I checked on the parts list, part 17 was shown as made of fabric.
I’m still not 100% clear how it was all done, but we’re going to use a piece of ordinary half round along the bottom edge of the ply, which has been shortened to finish about halfway down the longeron, and the fabric edge strip will be glued to the longeron itself, under the ply cover, with the lacing hooks riveted to it exactly as they will be to the fabric cover itself. This will look pretty exactly as it does in the photographs, and will have the added advantage of allowing us to remove the ply without disturbing the fabric.
Work continues on The Tank. As I’ve said before, it’s one of the most complex items to fit – it has to be made to match the rest of the airframe at the bottom, front and back, and the top is on show, so there’s no hiding place!
Yesterday I got both fuel taps piped up and the handle linkages connected to the cockpit. All of that was very straightforward, since most of it had been done already.
Today I had a bout of panic about the mountings. The tank has two channels at the bottom which are made of very thin steel. They are so thin we are convinced they will fracture from fatigue almost immediately, so I spent much of the morning dreaming up alternative ways of securing them to the fuselage. Then Rick came to give a hand and immediately spotted that this job would be done more than adequately by the side shields which are attached to the tank and also to the airframe!
Today we’ve mostly been working on the fit between the tank and the ply cover behind it. It’s a question of taking very, very careful measurements, and trimming back the ply very slowly, on the basis that it’s a lot easier to remove ply than to put it back afterwards! As usual with all the really tricky stuff, it’s Rick we rely on, and we do look as if we are making solid progress on that front. We hope to have it sorted tomorrow, so that we can move on to the front of the tank, where another problem has raised its head.
The difficulty is that the plywood engine former (the more or less circular bit just behind the engine) was made from a drawing from a later model of Scout, and we hadn’t appreciated that it was made to fit a later model of cowling. The net result is that it’s about 5mm big all round, and reducing it in size in situ isn’t very straightforward. On the other hand, it does give us the opportunity to adjust it so that the cowling will match the exact shape of the tank which is pretty important visually.
But as I say, that’s a job for tomorrow. Sufficient unto the day…
Big day today.
The petrol tank, which is the most complex fabrication on the aircraft, was offered up to the fuselage for the first time.
Ian Harris and Rick have been sweating blood over this for the past month, and so it was a very nervous moment for us. Thankfully, it all went pretty well according to plan, though until you’ve tried it you don’t realise how many things there are for it to bump into.
Designer Frank Barnwell was obviously aware that he needed to fit as much petrol on board as possible, and made the tank as BIG as he possibly could. The result is that it’s a very close fit at the front, bottom and back, and we had to spend ages making sure it wasn’t going to contact anything.
But after a bit of jiggery pokery we convinced ourselves that actually it’s a d*** good fit, and when it’s finally in place it will look perfect.
I visited Ian Harris yesterday where he and Rick were hard at work on the petrol tank.
One of the oddest features of the design is the back edge of the top cover. The picture below shows it more or less straightened out and you can see two things.
First, because the tank is more or less semicircular in cross section, and the back is sloping to match the slope of the cabane struts, the back edge is curved.
Second, the edge has been doubled over onto itself.
We don’t know why it’s been doubled over like that, but we’d spent weeks worrying about how to make that doubled-over edge, and considered abandoning it altogether, making the flange of the rear end stick outwards instead of inwards, and making it out of a separate curved strip of steel that would be soldered to the top cover.
In the end, Ian decided to do what it said on the instructions, and folded it over our wooden former to get the initial fold in the right place, then continued tapping it all the way over, and finally running it through the rolls to even it up. The result is absolutely perfect, and only took about half an hour, apparently! It’s also much easier to form around the back end than we feared.
So now we just need to find out what it’s for…
By the end of the day, the tank was as you can see. The sump and mounting channels are permanently riveted and soldered to the bottom, and the top and bottom are permanently riveted to the back.
So what’s left to do – in order – is:
Rivet the rear baffle plate to the top and bottom.
Rivet the front baffle plate to the top and bottom.
Rivet the front plate to top and bottom .
Solder the filler neck in place (it’s just loose at the moment).
Easy. Except that each rivet has to be fiddled into place from the inside using a pair of tiny pliers. Then you hold it in place using a magnet while you move the tank over a specially-built anvil, consisting of a long piece of steel bar, about 30mm x 75mm, clamped to a very solid post on the floor and a machine tool, to leave sufficient overhang to reach the full length of the tank. On the end of it is mounted a ‘set’ – a tool like a punch with a hollow nose which the head of the rivet sits in. Once you’ve got that all in place without dropping the rivet, pop a copper washer over it and rivet it in place using a hammer and a LOT of skill, as one false move will send the rivet crooked and it will have to be very carefully drilled out before starting again.
It probably only takes about three good taps using another set on the top to complete the process.
Now take a look at the number of rivets in each seam, and you begin to get an idea of the time and effort involved in making the b***dy thing.
But it, along with the propeller, will be the piece de resistance of the build, and we think that we’re looking at another two or three days to completion.
A month ago I made a list of outstanding jobs which went into as much detail as I possibly could. It ran to three pages of closely-packed words, and I sacred everybody with threats that it had to be completed and we mustn’t lose focus.
Since then, Theo’s been up for a day, taken some work back with him and got it all completed. This means that for the first time since 2009 there are no Bristol Scout parts in his house.
And today I actually came home at 1530, since there was nothing more I could do in the short term.
It’s a very strange feeling; for the last five or six years, we’ve been climbing the hill, with no sight of the summit. We’ve said vaguely that we hoped to have it finished by the end of a particular year (2012 was the first one, I note!) Suddenly, we’ve come over a ridge and there is the summit, and the idea that it will be ready to fly in May seems entirely practical. Of course it’s nice, but it’s also a rather unsettling feeling.
Theo has made up the cable connections for the shoulder straps for the modern harness. I’ve cut the slots in the back of the cockpit for them to fit through, and they are now fitted and complete.
The ply cover is now covered in fabric, and awaiting completion of the petrol tank before it’s finally fitted. I’ve started sewing the leather cockpit surround to the ply cover with copper wire.
Rick and his partner Marian are well on with a protective sock for the propeller, and is ordering a HUGE socket with a torque wrench for bolting the propeller boss to the engine.
He’s also making progress with the instrument panel. It had developed a bit of mould, but it’s all come off with a light sanding, and we’ve got the captive nuts to go on the back.
The next big event is to fill the oil system and see if it leaks, and I’ve got castor oil on order. The tank is about 32lt capacity, but at about £10/lt I’ve only ordered a part tankful!
Of course the most important work is the petrol tank, and Rick and Ian got two days at it last week, some of which was filmed. They’re working on it again on Thursday, and I’m told there’s a possibility it might be finished, though I think that’s a bit optimistic. Nevertheless, it’s certainly getting close.
And then we have to connect up the last bits of petrol piping, and we can take it outside and see if we can start the engine…
All civilian aircraft are required to have registration letters so that they can be easily identified. That’s why they all have the BIG letters on the underside of the wing, on the side of the fuselage and / or on the tail fin. The requirements are all in CAP 523, if you want to check it out.
So if you want to apply military markings – and that includes every warbird on the display circuit – you have to apply to the relevant arm of the military for special dispensation to use their markings, and they check carefully to see that you aren’t planning to surreptitiously start an uprising by impersonating the real thing.
Thus our aircraft will have a civilian registration applied to it – G-FDHB, using Granddad’s initial – but we want to use exactly the original markings from 1916, and this week we got permission from the Deputy Assistant Chief of Staff (Air Engineering) at Whale Island in Portsmouth officially giving that permission. It officially allocates serial number 1264 to our aircraft, which is great news. I’ve sent the letter off to the CAA, but it means that we are officially allowed to apply the exact original markings, and the only place the civilian registration will appear is on a small metal plate which has to be attached to the airframe somewhere.
No-one has ever offered a satisfactory explanation for this form of identification; it’s not as permanent as the serial numbers on cars, for example, which are welded permanently in place or etched into the engine block. These can be bolted to the airframe, and thus can be easily removed. I understand they were originally intended to aid identification when the thing crashed and caught on fire, and everything including the occupants were fried to a crisp and completely unidentifiable, and it occurs to me to wonder how many times they have actually proved useful…