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63. Confusion

04/08/2013

While the whole point of the exercise is to build an absolutely accurate rebuild of the aircraft my grandfather flew, we have to make any number of small concessions along the way, particularly if it’s going to be cleared to fly. Most of these are invisible – the use of chrome moly instead of carbon steel, and modern glues instead of the old animal glues.

Some are visible and for safety reasons; the reinforcement of the main spar at the strut fitting, the use of modern turnbuckles; but we can’t avoid them and the differences are at least documented.

But one that continues to puzzle me is the little matter of the heel trough, since we’ve had to make a change (albeit minor) without understanding how the original was configured.

Detail of photograph from the original parts list

Detail of photograph from the original parts list

Photograph of our machine showing the heel trough raised a little

Photograph of our machine showing the heel trough raised a little

If you look at the picture from the original parts list and compare it with the photograph of ours, you’ll see that we’ve had to raise the front of the heel trough about an inch. If you don’t, you find the big carry-through cable passing through the side pieces and just where your heel needs to be when you apply rudder.

With the heel trough in its position as shown on the drawings, your heel snags on it.

With the heel trough in its position as shown on the drawings, your heel snags on it.

There’s absolutely no doubt that the carrythrough is required and in the right place; I could show you all the individual drawing details and the parts list, and it would have been an essential part of designer Frank Barnwell’s original design concept. If you leave it off, you’d need to beef up other bits of the structure, otherwise the flying loads in bumpy conditions could pull the fuselage apart…

But we are pretty convinced, looking at the photograph from the parts list, and also from assembly drawing XD773 that the carrythrough wasn’t fitted in practice. Drawing XD753 showing the fitting at CB with the hole for the carrythrough bolt, and details of the bolt itself is dated 14 Nov 1914, as is XD773, so it’s not a matter of a later change of design.

Detail drawing of the fuselage fitting showing the carrythrough

Detail drawing of the fuselage fitting showing the carrythrough

Arrangement drawing showing the heel trough but not, apparently the carrythrough.

Arrangement drawing showing the heel trough but not, apparently the carrythrough.

And if someone from the assembly line came to Barnwell and said ‘Excuse me sir, but the heel trough doesn’t fit with the carrythrough’, would he just say ‘Oh, well, leave off the carrythrough then.’? Doesn’t seem very likely, does it?

Anyway, we’ve decided to include the carrythrough and raise the heel troughs just enough to go over the top. We reckon that provided you wear shoes with a sharply defined heel, they shouldn’t slip over the top of the rudder bar. If it continues to be a problem, you could imagine wearing some sort of spurs to ensure there’s no problem.

Heel trough

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From → Building, Technical

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  1. 88. Confusion resolved. | Bristol Scout

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