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5. Replica or Reproduction?


There was one last link in the chain of information. Leo Opdyke had told us that a set of plans had been drawn up by Stan Teachman, using the original Bristol drawings obtained by Leo. Stan was a modeller, and the plans were intended to give detailed assistance to those who wanted to build fully accurate models of the Scout. Leo didn’t have the drawings, but gave me Stan’s contact details, and I wrote, only to discover that Stan had died some time before.

The Bristol Scout replica built by RAF Apprentices in the 1960s, currently housed at the Shuttleworth Collection.

But once again, serendipity came to the rescue. I had discovered that the only other Bristol Scout replica in the UK – the one built by RAF Apprentices using modern materials and never intended for flight – was being restored by one Keith Williams. When I contacted him, I discovered that he had the original ink Teachman drawings! We came to a deal, and while we have to be careful to cross-check them against the originals, they are easy to read and provide an excellent way of understanding the general layout of the machine.

Incidentally, we were able recently to see Keith’s restoration at the Shuttleworth collection. Even though it’s not intended to be accurate, it gives an excellent idea of the size and sit of the finished article. I was slightly perturbed to note, however, that the RAF apprentices had made a very significant engineering blunder. On a biplane, the wings are braced by diagonal wires. Those going from the bottom of the fuselage to the top wing are called ‘flying wires’, since they do all the work in the air, while those going from the top wing in the centre to the outside of the bottom wings are called landing wires, since they hold the wings up on the ground.

The Bristol Scout was one of the first to have double flying wires, to give added security in the air. And yet the replica has double landing wires and single flying wires! Ah, well.

One of the first questions you need to decide when approaching a project of this type is the degree of care with which you want to replicate the original aircraft. Generally there are three classes into which they might fall.

A rebuild is one which can be said to be an original aircraft. To fall into this category, you need to have at least one part which can be shown unequivocally to have been part of the original aircraft. The most extreme example of this is the maker’s nameplate, around which you then reconstruct the entire machine from scratch.

You might think that’s a bit absurd, but you should bear in mind that an aircraft which is unquestionably original may have very few – if any – original parts. Aircraft are light weight and highly stressed, and over the years parts will naturally have been replaced due to wear and tear, corrosion, or accidental damage. No-one questions their authenticity, so you can see that the scenario suggested above isn’t significantly different; it’s just that the replacement process (provided you can show that the aircraft has been rebuilt according to the original design and materials) happens all at once, instead of over a period of years.

A reproduction is also built exactly like the original, but can’t demonstrate that crucial link with the original aircraft, either through one part (like the nameplate) that’s unquestionably original, or through continuous history.

Leo Opdyke's machine is an example of a reproduction, since the manufacture follows the original design exactly.

A replica is a machine which makes one ore more concessions to modernity, and differs in some distinct way from the original. For many machines, it’s the original engine that is the sticking point; they are very difficult to get hold of, and difficult and expensive to operate if you do. But original airframes can be pretty impractical too – the undercarriage will be very fragile by modern standards; linen fabric can sag in damp weather; a wooden tailskid is quite impractical if you need to operate the aircraft anywhere other than on grass. So a replica can involve substantial redesign – even to the extent of using modern welded steel tube construction instead of wood, and a relatively modern radial or in line engine to replace the original rotary.

We had to decide very early on which route we were going down. We spoke to Ernie Hoblyn who flew a replica Sopwith Triplane at air displays, and he said that, even with a modern engine, the Tripe was difficult to operate owing to its limited (well, basically non-existent) crosswind capability.

If you haven’t come across the problem before, here’s a quick rundown. An aircraft flies because of its speed through the air, not over the ground. So it’s always best to take off or land an aircraft facing into the wind. That way the wind gives you a head start in achieving airspeed, even before you start moving. Conversely if you take off downwind, the wind is actually hindering you, so that you have to go much faster over the ground in order to get flying speed through the air.

But even worse is when the wind is blowing across your takeoff path – the crosswind situation. An aircraft is designed to fly straight ahead – otherwise it would be almost impossible to steer it. But if you try to take off or land with a crosswind, there will come a point where the wheels are taking you in one direction and the wings are trying to fly you in another, and the result is undignified and usually expensive.

In WWI all airfields were broadly circular, meaning that you could take off and land in precise alignment with the wind, and avoid the crosswind problem. These days virtually every airfield has one or two runways only, making the operation of these early aircraft much more problematic.

Ernie also said that a replica was only really useful as a display machine; even with a modern engine it was usually to impractical to be used for sport flying, and it wasn’t of interest to museums, since it wasn’t historically accurate.

For us, the problem was fairly easily resolved. We wanted to build and fly my Granddad’s aircraft, not something that looked a bit like it. We weren’t particularly interested in display flying. And we were interested in being able to pass it on to a suitable museum once we’d flown it a few times. And now, finally, we had the information to be able to say hand on heart that every part of the machine would be exactly as in 1915.

Curiously, this also led to another benefit. In the UK, if you’re building an aircraft yourself, you need (except for certain very lightweight types) to be able to demonstrate that it complies with modern airworthiness standards.

For aircraft built before any such standards existed, this clearly isn’t appropriate, so the rule is that you must be able to show that what you’re building is identical to a production aircraft. If you make any changes – by installing a modern engine, for example, or building the airframe out of modern materials – you have to demonstrate its airworthiness by means of complex calculations, load tests and possibly air testing as well. By sticking religiously to the original design, we could avoid all those complications.

So, the decision was taken.


From → Technical

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