Monday 2 May 2011

Which drawing is the correct drawing?

With the lower ribs all complete, and the basic spars completed, but not cut to length, it was time to do an initial assembly of the lower wings, to work out where the fittings would go, as well the drag / anti drag wires, and the general assembly.
Right Hand lower wing trail assembly
While this was a very encouraging photo, it would be another 6 months before this wing would be glued together! If someone had told me that when I did this trail assembly in October 2010, I would never have believed them.
next step was to work out where the ribs would go, and mark for the various fittings, plywood doublers, wires, and hardware.

and this is when I found out nothing really measured up...

I had been using a general arrangement drawing apparently based on the EAA replica wings, and approved by Matty Laird back in the late 70`s.

Unfortunately on examination, the rib spacing dimensions on this drawing did not match either the EAA rib spacing as measured on the airplane, or the Rib spacing on the Paul Matt drawings, (previously assumed to be the most accurate of the Super Solution drawings)
so which one was correct?
Well, I decided that as the EAA drawings had more details than any other, they would be the "correct" drawings, but the various reference differences were quite significant
I have also found each potential change has a snowball effect, and predicting just how much it changes the follow on process is not very easy.
Well, with a rib spacing determined, and the general assembly worked out, it was time to take the ribs back off, and start on the fittings, and doublers.

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