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84. Comparisons

17/11/2013

While we were delivering the magneto, we took the opportunity to visit the RAF Museum at Hendon, which is only just around the corner.

All the aircraft were of interest to us, but of course we were particularly interested in the contemporaries – and immediate predecessors – of the Bristol Scout, in case there were lessons we could learn.

We’d arranged with the curator to have an escort to get a close up look at the aircraft in the Graham-White hangar, which is where the majority of the First World War aircraft are displayed, and this enabled us to look in detail at the Sopwith Tabloid, which first flew while Frank Barnwell was drawing up the Bristol Scout, and the BE2B, which was being manufactured under licence at the Filton 100 years ago. Other aircraft we were interested in included the Bristol M1C monoplane and the Bristol F2B Fighter that came shortly after the Scout from the desk of Barnwell.

The Sopwith Tabloid preserved at hte RAF Museum, Hendon

The Sopwith Tabloid preserved at the RAF Museum, Hendon

We checked out the Sopwith Tabloid first. First flown in November 1913, exactly 100 years ago, it was – like the Scout – designed for speed, with the smallest wings and the biggest engine. Unlike the Scout, it was originally designed as a two-seater. And even more unusually, the seats were arranged side-by-side. Clearly this means a wider fuselage than usual, and that was something designers tried to avoid, since it obviously created more drag and slowed the aircraft down. Thus the Tablet’s cockpit was only 1m wide (3ft 3in), requiring the two occupants to be slim and on good terms! It had a very unusual cowling which was intended to reduce drag compared to the usual bluff-fronted cowlings usually fitted, and small (7.77m or 25ft 6in) wingspan. The undercarriage was of the common skid type to prevent the very common noseover accidents of the period. Early test flights took place in mid-November, but it’s unlikely that Barnwell would have used any features from its design, since its first public display was not until 29 November, and Barnwell started producing detailed sketches for the Scout a couple of weeks later. Nevertheless, its sparkling performance (only just under 90mph with an 80hp Gnôme engine, would certainly have given Barnwell pause for thought. He may well have felt that the Scout, with its even tinier wings, had a good chance of exceeding that figure.

But it was certainly interesting to look at the differences.

The most obvious one is that cowling, and with the wisdom of hindsight, it seems likely that this was a major reason for its excellent performance. A bluff-fronted fuselage shape not only creates drag in having to push the flat front through the air, it also means that the inner part of the propeller is pretty ineffective, and the turbulence it creates generates additional drag all the way down the rest of the fuselage. Today designers of light aircraft will spend huge amounts of time and money on the shape of nose of the aircraft, knowing that it pays great performance dividends. The original Scout cowling was also odd, and I wonder if Barnwell had copied the concept of a half-cowling from his boss Henri Coandă, who seems to have favoured a similar arrangement, albeit with rather more fluency than Barnwell’s first effort, and with a strange horizontal seam at the level of the top longeron which would have made it very difficult to manufacture.

The Coanda-designed Caproni-Bristol machine bought by the Italians. and manufactured at Filton while Barnwell was there. Did the design of the engine cowl influence Barnwell?

The Coanda-designed Caproni-Bristol machine bought by the Italians. and manufactured at Filton while Barnwell was there. Did the design of the engine cowl influence Barnwell?

Bristol Scout Prototype cowling.

Bristol Scout Prototype cowling.

The undercarriage on the Tabloid looked very much less substantial; the diagonal bracing was only half the strength.

And the Tabloid used wing warping for roll control. It’s not a particularly effective means of control, particularly at higher speeds, and the fact that the wings can twist reduces their structural integrity too.

But the rest of the structure looked pretty comparable.

The Geoffrey de Havilland-designed BE2B that was being manufactured under licence by the B&CA at the time Barnwell was designing the Scout

The Geoffrey de Havilland-designed BE2B that was being manufactured under licence by the B&CA at the time Barnwell was designing the Scout

The next on the list was the BE2B. This aircraft had been designed by the incomparable Geoffrey de Havilland at the government-run Royal Aircraft Factory and by 1913 was being manufactured under licence at the main Bristol works at Filton. It’s traditionally supposed to have been a dog of an aircraft, but in 1912 the original BE2 had been vastly superior to all the private venture aircraft entered in the Larkhill trials to find an alternative military machine. It’s just that by 1915 it had been completely outpaced by developments in aerial warfare.

Despite its somewhat gangling appearance from a distance, close up it’s clearly a very robust design, with cable bracing all over the place, and while the big distance between the wings might look ungainly, it helps to make them more efficient. Although there was little in the overall design where one could definitely trace a connection, there were one or two details which are similar, and which Barnwell might have copied from the BE2, though they might equally well have come from elsewhere.

BE2 Tip skid

BE2 Tip skid

BE2B Cockpit, with brass stick and map holder

BE2B Cockpit, with brass stick and map holder

These included the underwing skids made of Malacca cane. Landing these early machines was fairly unpredictable, and often ended in a groundloop – an uncontrolled turn that gets tighter and tighter, during which the wingtip could easily scrape on the ground. Skids of Malacca cane were easily replaceable and a lot cheaper than repairing the wing itself! Those on the BE2 are virtually identical to the Scout. And in the cockpit there are a couple of features that have some similarity. One is the use of brass tube for the control column. Like a number of other design features, this one seems hard to justify, since the brass is heavier than either steel or aluminium for the equivalent strength. But it’s there on the BE2B, and so it is on the Scout. The other common feature is the map case, so that you don’t have to hold the map on your lap or risk having it blown over the side if it was loose. The one in the BE2 is a lot bigger than that on the Scout, but it’s just possible this was something picked up by Barnwell on his trips round the main works. Unfortunately it doesn’t give us any clue as to how the Scout one was made; we have a general arrangement which gives overall dimensions, and we’ve been able to compare those with the fold lines on Granddad’s original maps, but it would seem we’re unlikely now to be able to tell how the map case was made and we’ll have to design our own.

Next we checked out the Bristol Monoplane, which was Barnwell’s next project to reach the production line after the Scout, but that doesn’t seem to have an instrument panel at all – in fact hardly any instruments, and those dotted more or less randomly around the cockpit. We’d already looked in detail at the M1C at Shuttleworth, and it’s clear Barnwell re-used Scout components in the Monoplane design; the elevator horns and the tailpost are obvious examples.

Bristol F2B

Bristol F2B

In some ways, though, the most useful comparison was with the Bristol F2B Fighter, which, although it significantly post-dates the Scout, retained a number of features in common with it, and one in particular has been of great assistance to us.

It was also particularly useful that the Museum’s F2B is partly uncovered, enabling us to get a close look at the internal structure.

The seat on the F2B is identical to ours.

The seat on the F2B is identical to ours.

Perhaps the most obvious similarity is the wicker seat, which is identical to ours. We were able to see the same type of joint in the longerons, using copper boat nails, and similar metal fittings at the junctions.

F2B longeron joint

F2B longeron joint

By that time, they’d moved on to threaded rod for the diagonal bracing, which, although used on later Scouts, wasn’t the same as 1264. We also paid close attention to the lacing used to attach the fabric to the fuselage; Shuttleworth’s advice is to use modern glues and make the lacing a sort of sewn-on decoration. I don’t think we’ve made a definite decision on this, but the Bristol’s fabric was absolutely immaculate and we took lots of close-up photos for future reference.

F2B whipping on a spliced joint shows us how it should be knotted all the way up. I'd better undo the stuff I've done, then!

F2B whipping on a spliced joint shows us how it should be knotted all the way up. I’d better undo the stuff I’ve done, then!

The foothole is also more or less identical, and while we were confident we had all the information we needed, it was good to see it corroborated. We also took note of the rest of the covering, since this is something we’re going to have to face up to in the very near future!

The wing section looks somewhat similar to the Scout's, with the very flat top between the spars

The wing section looks somewhat similar to the Scout’s, with the very flat top between the spars

One feature we hadn’t expected was the aerofoil section used for the wings. I’ve noted before how peculiar the section is on the Scout, and how it was supposed to be one developed by Coandă, but the one on the F2B looks quite similar, with the strange flat top between the two wing spars. I’ve not been able to establish the details of the F2B wing section, but it would be interesting to know more details.

The magneto switch comes straight out of an Edwardian house. Thankfully, there's a shop in Ludlow which sells exactly the same sort

The magneto switch comes straight out of an Edwardian house. Thankfully, there’s a shop in Ludlow which sells exactly the same sort

One other feature we photographed was the ignition switch. This engine presumably had twin ignition, and so the switch has two handles; ours only has single ignition, and we can find a switch of identical design from a local store that specialises in period house fittings.

F2B inspection panel

F2B inspection panel

But perhaps the most useful detail was the inspection panels in the wings to enable one to get at the aileron cable pulleys. Again, we had a general arrangement with gave the size, and the parts list told us what they were made of – and I’d made a test example to prove the concept, but the F2B has obviously identical ones, and so we took lots of photos to ensure ours were the same, and suddenly all the uncertainties were resolved!

Of course, the standard of workmanship on the museum pieces is quite immaculate, and I think we felt a little overawed by it; ours is certainly airworthy, and may even be more representative of the standard actually seen in WWI, may not be quite as neat as theirs. We’ll do our best, though!

Talking of workmanship, the exhibit that took our communal breath away was the hull of the 1930s Supermarine Southampton flying boat. Rescued from an east coast river, where it had been converted into a house, it is all wooden construction, and its elegance and beauty frankly defy description. All I can say is that I’m glad we aren’t trying to restore one of those to flying condition!

Supermarine Southampton flying boat hull. There are five different types of wood used in its construction.

Supermarine Southampton flying boat hull. There are five different types of wood used in its construction.

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From → History, Research

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