In the run-up to the LAA Rally we’ve been working to try and make it look as complete as possible, and today Rick finished the instrument panel and got it fitted to the aircraft. Here he is trying it out for size.
The original drawing showed a relatively uncluttered display but the very large map holder seems to squeeze everything into the edges. The map holder is made to the dimensions on the drawing, and we know it’s right because it matches the folds in Granddad’s original map.
One thing that’s immediately apparent once the cockpit surround is in place is that actually reading the instruments is strictly for midgets, but the Air Speed Indicator (the only modern instrument) and the tacho are the only essential ones and they are the easiest to see.
As well as finishing off most of the fabric covering on the flying surfaces this week, Theo’s taken a look at the wheels.
Almost all WWI aircraft wheels were based on motor cycle wheels with spokes. They were fairly strong, relatively cheap and were easily replaceable. But for aircraft use all those spokes created loads of drag, and so they were covered with fabric. I understand that in those days you could get tyres with little wire loops in the sidewalls to which you could lace the fabric cover.
The Scout didn’t use that system. The drawing says that the motorcycle tyres – ‘heavy motor cycle smooth tread – were wired on. We’re not quite sure what that means, but ours, as bought from the Vintage Motor Cycle club, are beaded tyres, which means that the inside edge of the tyre has a bead which sits inside a groove in the rim.
The instructions for the fabric are; ‘Covering as used on Bristol Monoplane (that must have been the Coandă monoplane, not the M1C) wheels. Side covers sewn to fabric strip round rim.’
We’ve struggled to understand this, but thought perhaps a strip was laid inside the rim underneath the inner tube, which then stuck out each side, to which the main cover was hand sewn.
The trouble with this is that the tyre bead won’t sit as securely in its groove, with the risk that if there’s any sort of drift on landing the tyre will come off, and very likely tip the whole aircraft on its nose…
(Beaded or clincher tyres were famously insecure, and came off at the slightest provocation.)
Other people use Superseam cement to glue the fabric direct onto the rim, but ours seem very small for that and in any case the paint is dissolved by the acetone of the cement, so that idea was kicked into touch.
Another cunning plan used by others is to use a ply ring (about 25mm wide) round the outside to which the fabric is glued. Holes are drilled in the ply so that the two – inside and outside – can be stitched together through the wheel spokes using standard ribstitching techniques. The knots in the ribstitching won’t be entirely authentic, but will replace the hand stitching that was on the originals, and the covers can easily be removed and replaced if they get damaged, and that’s the cunning plan we’re working on now.
We’ll let you know how things progress.
This week has seen the completion of most of the work on the flying surfaces. We’ve managed to re-cover one wing, finish off all the ribstitching, apply rib and edge tapes throughout. There are still inspection openings to be fitted to the wings, and they’ll need a couple of final coats of dope to be applied, but we’re going to leave that until we see what (if anything) can be done with the wrinkles in the fabric.
But when Theo brings the wings up to the fuselage on Bank Holiday Monday ready for the LAA Rally the weekend after, it’s likely to be the last time they’ll be down in Dorset, and poor Theo’s going to be suffering withdrawal symptoms.
I checked the photographic record, and we first started cutting timber in November 2009, so Theo’s had bits of Bristol Scout here for nearly five years, and the house is going to feel very empty; in particular, the space behind his sofa that has housed the wings for so long.
There will still be plenty of work needed, but he’ll be coming up to Shropshire for it, and in the meantime he’s going to be getting plenty of time in on his own aircraft to keep his flying skills honed for the date we get to fly the Scout…
We finished up the last bits in perfect time on Saturday afternoon, leaving time for us to pop up to Spetisbury Rings, the ancient hill fort just above the village, where Theo’s stepchildren had organised Music and Merriment, a one-and-a-half day music festival raising money for the local hospice in memory of their mother. It was an astonishing feat of organisation for two people, and – with the co-operation of the weather gods – a HUGE success.
It was a wonderful way to round off a successful week.
And did the wing recovering work better than before?
Well, here’s the tale in pictures.
We’d decided to put more tension on the bag than we had before. We used a combination of clamps and staples and tried to make sure the spanwise tension in particular was as great as possible, so that the fabric wouldn’t be pulled onto the spars in between the ribs.
We glued the inboard end of the wing first and then the aileron cutout.
The following morning, we steeled ourselves and took up our paint brushes, applying a 70:30 mix (70% dope, 30% thinners) to the fabric, trying to put it on as lightly as possible to avoid the unsightly drips which had disfigured a couple of the other wings.
At this stage, the fabric was drying at the far end where we’d started and was still wet at the near end, and it was clear that the damp bit was still nicely taut and even across the tops of the ribs, with little or no dipping in between, but the dry end was starting to form the dreaded wrinkles again, and by the time it was fully dry, it had formed the familiar pattern across the whole wing.
But the die was cast; we are now committed to this covering, and if it’s not considered acceptable for flight, we will presumably have an extremely expensive static display, and the story that it is representative of how it might have looked after a year’s service in the eastern Mediterranean!
We’ve carried on and completed the ribstitching on all four wings ready for the LAA Rally, and will not apply the final coats of non-tautening dope until we’ve discussed the situation as thoroughly as possible.
When I got to Theo’s, we had a difficult decision to make. The covering, as you will know from previous posts, was a somewhat stressful affair, and while we feel they are generally acceptable, there was one that gave us particular concern. In fact it was the last wing to be done, and the problem was – at least in part – down to the tape we’d used on the woodwork before covering. Everywhere else we’d used ½” cotton tape – the same as for ribstitching, and while it was laborious to apply, since it had to be stuck on with dope or cement, it did the job of preventing colour leaching through from the wood into the fabric. When we’d needed more, we’d spotted some special self-adhesive anti-chafing tape on the LAS website, and bought a couple of rolls on spec. It was an order of magnitude easier to apply, so we decided to go with it. We’d also been so pleased with the tautness of the fabric when it was glued onto the frame that we eschewed the use of water to tauten it (in line with one of the conflicting bits of advice we’d had).
Unfortunately this led to a less than satisfactory covering. Something in the self-adhesive tape gave a yellow tinge to the fabric where it came in contact, and the lack of water spraying led to unacceptable sagging and also creasing of the fabric, so we decided to bite the bullet and recover the wing. We had the materials to do it, so it was only a question of our time, and we felt there was enough of that available to allow us to do it without putting too much pressure on ourselves.
In fact the job’s gone very well, and within a day we’ve cut and sewn the fabric, applied the ½” tape to the structure, glued the bag to the wing and watered it ready for doping tomorrow morning. By now we’re getting pretty slick at all those parts of the operation and it’s only the actual doping itself that remains something of a black art. We’ll let you know how things go on.
In the meantime, I had something of an inspiration today, and Theo has awarded me the ‘Hero of the Day’ medal. You may remember that I’d found that making frayed-edge tape was simpler than I’d expected; a craft knife clamped in a Workmate acted as a slitter, and teasing the threads out was relatively straightforward with a little practice. This worked fine when I was cutting 2in and 3in tapes down to size. It’s less easy if you’re trying to make tapes from spare bits of fabric because it’s almost impossible to slit the fabric exactly down the line of the weave, and this makes teasing out the edge threads to leave a nice neat tape almost impossible.
But the solution is blindingly simple. Tear the fabric into strips about ¼” wider than the nominal width of the tape. It will always tear exactly along the line of the weave, leaving the edges nicely frayed to the correct width. Then iron the tape to get the edges to lie nice and flat, and job’s a good ‘un as they say!
I stopped off at Hercules propellers in Stroud on the way down to Theo because we need to work out how to attach the Bristol logos to propeller and struts. These are original Bristol transfers, and they aren’t the water-based ones that you get with Airfix kits. These are fixed using gold size or Copal varnish, and the instructions are very scary. I’d bought some and Rupert Wasey had acquired some practice ones, so we had a go and it doesn’t seem quite so terrifying now we’ve done a few.
The face of the transfer is attached to tissue paper, which is then fixed to waxed paper. The reverse of the transfer has gold on it, and it’s this which is visible when you take the transfer out of the packet. Gold size is applied with a finger (‘NOT a brush’) onto the back and left to go tacky. Then you pop the transfer onto the surface, making sure you position it absolutely accurately because the tacky size won’t allow you to move it at all. Rub the waxed paper with a circular motion moving outwards to force any air bubbles out, but making absolutely sure you don’t try to move the transfer at all. Then carefully separate the waxed paper from the tissue paper and gently lift the waxed paper away. This is the first time you’ll see the final design of the transfer through the tissue paper. The size is water-based, so now you press (DON’T rub) with damp (not wet) cloth to moisten the size enough to make sure there are absolutely no air bubbles. You’ll see the benefit because the tissue paper becomes almost completely translucent. That done, you can start to apply a wetter cloth which should separate the tissue paper from the transfer and allow you to slide it gently off the transfer. There will be size left on top of the transfer, and you can remove that with a mixture of water and turpentine until it doesn’t feel sticky any more. The size takes a while to go absolutely hard, so treat the transfer with care for some time afterwards, and preferably paint a coat of varnish on top to protect it.
I left the wing struts with Rupert and he’s going to do them as well as the propeller now he’s got the technique.
Of course we had to go and look at the propeller as well, and it is simply breathtaking, even though it’s lacking the final coats of lacquer. It should be ready for the LAA Rally at Sywell on 29-31 Aug, and I hope you’ll come and say hello to us there. The Scout won’t be complete, but it won’t be far off, and the pressures building to get it ready for the big day.
The ply hoops are needed to mount the ply cover on. This is one of the scarier jobs, since it requires holes for the cabane struts, cabane rigging and oil tank lid, all of which appear in more or less random spots in the middle of the ply.
Obviously this was a job for Rick, and while it’s taken a couple of days to sort, the end result is not quite a work of art, but more than just a job well done.
Each of the holes is precisely placed, and, despite being weird shapes, there’s a pretty even gap of 3mm or less around each. Fitted, it makes the fuselage look altogether more complete, and is a huge psychological boost.
One of the things we noticed as we were doing it was how very much smaller the cockpit opening was than before, so we were understandably keen to see if we could still get into the bloody thing! Happily it proved possible, even for myself (I’m the tallest of us) and to prove it, Rick demonstrated the technique for getting out.