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15 Jan 1914. Thursday.

16/01/2014

Two sketches today, and you’ve seen one already, but here it is again, because there are a couple of interesting points to make.

558 Arrangement of Controls 15-1-14

559 Special Cable Fittings 15-1-14

The first is of historical significance, in that it’s always been supposed that the prototype Scout fuselage was inherited, along with its serial number, from the SB5, which was a project designed by Henri Coandă for the Italian government, and abandoned partway through construction when the contract was cancelled. The serial number (SN183) is clearly the same and was used throughout the construction for the Scout, but here is the only evidence of a bit of the SB5 actually in use, since the note at the bottom shows that the tiller bar came from that project.

The next is the note just above it about the ‘U clip of 20swg steel put on in place of armouring for splice end.’ The front of the longeron was made of ash and the rest in spruce. There was a splice joint between the two, and you can see it detailed in the top sketch. Making that joint was tricky, since you only had animal glues which were weak and unreliable, so they used copper rivets – i.e. boat nails – as well. It was then whipped with twine. This note appears to indicate that Frank, at least, was considering using some sort of ‘armouring’ for the splice joint, and that this clip would replace it. You can see that a U clip like this would add to the security of the joint, and I wonder if he used something of the sort on the prototype? If so, they went back to the standard practice – boat nails and whipping twine – for the C Scout.

And finally, we need to look at the wholesale changes that were made in the control system for the C Scout.

To make this easier to see, I’ve included the equivalent arrangement drawing for the C Scout (XD 773).

XD773 Arrangement of Controls

The first thing you note is that the rock shaft is now mounted below the fuselage. This seems odd, on the face of it, since the rock shaft bearings would have been much more prone to dirt and dust, and it was necessary to make a complicated aluminium cover for it. It will increase the leverage of the stick by a couple of inches or so, which might have been important if they were very stiff, but it seems unlikely. The only positive I can see is that it would certainly make it easier to get at for maintenance. The double bushes in the rear bearing are retained, so it’s still very difficult to get the rockshaft to move freely.

The next thing is that the hand control stick extends below even the rock shaft. I think the reason for this is that the pulley that was there before would have got in the way of the wood fuselage frames and they had to come up with an alternative solution. It’s not a good one; the angled cable run from the bottom of the stick means that the tension in it will vary greatly between the centre and the ends.

And finally the tiller has moved aft several inches to be mounted with the font rock shaft bearing. Personally, I wish they’d left the tiller where it was, as it would have given me sufficient knee room, but maybe it was felt that the new position was better for the average pilot, and certainly Rick and Theo aren’t complaining about it’s new position.

All in all, it’s a rather mysterious set of changes, and it’s one of those times when one wishes one had a time machine…

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