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89. Alignment

01/01/2014

One of the things we’d always understood to be a big problem was tightening up all the cables bracing the fuselage.

Fuselage bracing wires

Fuselage bracing wires

There are lots and lots of them, and it’s popularly supposed that it’s one of the trickier bits of building the fuselage, since an adjustment on one will have unexpected consequences somewhere completely unexpected.

I can see that this might be true for a fuselage where most of the wires are already tightened, but in our case, working from scratch, it seemed to go pretty smoothly.

The first thing was to tighten each set of diagonal wires going transversely inside the fuselage so that each frame was perfectly square.

Next we went to the front of the aircraft (station A) and made sure the front engine mount was perfectly at right angles to the longerons by adjusting the wires in the first section.

Then we chocked up the wheels so that the top of the front engine mount was perfectly horizontal using a spirit level.

We went to station B and checked the top was exactly parallel with station A. You adjust this by carefully tweaking the wires in each panel (top, bottom and each side) – tightening one and loosening the other – until the top of station B is perfectly horizontal. Once this was okay, we tightened each wire the same amount until there was sufficient tension.

Thereafter, we went back, section by section. We made each wire just taut, then checked that the top wasn’t twisted using a spirit level across the top longerons, and adjusting all four wires (top, bottom and each side) as necessary. Then we checked using a string line against centre marks at each station that it wasn’t bent sideways (adjust the top and bottom pairs) or up or down (the side wires). Finally, we tightened everything down the same amount until there was sufficient tension on all the wires.

Perhaps we had an easy ride, but it seemed okay to us!

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