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12. Comparing with the Opposition

01/02/2012

As I said in part 3 of this blog, In January 2007 we went to see Leo Opdyke’s Bristol Scout, now hanging in the FAA Museum at Yeovilton. It was this visit that pretty much set the whole exercise in motion.

You may remember that he built it in the basement of his house in Poughkeepsie, NY, over a fifteen year period, only to have the engine fail on the second flight in 1975. The airframe is now largely uncovered so that you can see how it’s made, and this was ideal for us.

Curator David Morris lent us a cherry picker in order to get a close-up look at it, and we found a very high standard of workmanship throughout.

Leo Opdyke’s Bristol Scout hanging in the RNAS Museum at Yeovilton

You can see how it’s a wood frame, with metal brackets at all the joints and masses of wire bracing across all the diagonals to keep it rigid.

The wings have internal bracing wires, but external ones too. All of them have bottlescrews for adjustment, and apparently it’s the devil of a job to get them all adjusted correctly!

From our point of view, it proved that there was nothing that required complex manufacturing techniques; essentiall, pretty much everything could be made at home.

The following year, in Jan 2008, we were able to go and take a look at a contemporary WWI aircraft, the Sopwith Pup, that was being rebuilt – strangely enough, also at Yeovilton, but on another part of the airfield.

This particular aircraft is original. It was built in 1917, survived WWI, and became a civil-registered aircraft, G-EAVX, and is slowly being restored by Kelvyne Baker and his team.

Sopwith Pup G-EAVX at Yeovilton

The first thing you notice is how very similar it is to the Scout. Wood frame? Check. Wire bracing? Check. Biplane layout? Check. Ply wing ribs? Check. 80hp le Rhone engine? Steel tube empennage (the tail surfaces)? Check. The major difference (not apparent from the photos) was that the Pup (having been designed a year after the Scout) was fitted with a single machine gun. So we should be able to learn from their experiences.

When we asked what problems they’d had, Kelvyne showed us the replacement wing spars they’d had made.

Sopwith Pup G-EAVX – banana-shaped wing spars!

You can probably see that the middle piece of timber has got a very distinct bend in it. This was going to be the main spar for one of the wings, and is now probably useless, though it might be possible to straighten it by clamping it to a flat surface and leaving it in a temperature and humidity controlled environment.

There are circumstances where you need to deliberately bend wood into shape, and in those cases, we resort to the ancient technique of steaming the wood – leaving it cooking in steam for several hour until the fibres are softened, then bringing it out and quickly clamping it to a slightly tighter curve than you finally need. Leave it to cool down and dry out, and when you take it out of the clamp, it will straighten slightly, but still retain most of its curvature. The art is in anticipating how much it will straighten!

Then in Sep 2010 we went to Batley in Yorkshire to visit Bob Richardson and the team at the Northern Aeroplane Workshop, to see the Sopwith Camel that they are building in the back of a disused car showroom.

This aircraft is a very long-term project, but was finally starting to look like a completed airframe when we visited.

Sopwith Camel at Northern Aeroplane Workshop – Theo Willford and Bob Richardson in the background

The Camel was a development of the Pup, and the design dates from late 1916, and yet the first thing you notice when you see the airframe is that it looks very, very similar. Sure, it’s got a bigger engine and two machine guns instead of one, but – given that the first powered flights in Europe had taken place only eight years previously, it’s amazing how much the design of aircraft had matured and stabilised. Partly, of course, it will have been down to the fact that the War Department might be naturally conservative, but wartime is traditionally  the spur for radical development, and yet all British aircraft in WWI used the same basic construction method, and the majority continued to use the rotary engine , which gave the best power-to-weight ratio.

The Bristol Scout could do 95mph and could climb to 10,000ft in 18 minutes. The Sopwith Pup could do 97mph and made it to 10,000ft in 14 minutes. The Sopwith Camel, generally regarded as the supreme fighter aircraft of WWI could do 115mph, and (with a 170hp engine) could climb to 10,000ft in less than ten minutes.

Which makes the Bristol Scout – designed in late 1913 – all the more remarkable.

 

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From → Research, Technical

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  1. 17. Ringing the Changes « Bristol Scout

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