rib spacing

[Dalton]

So I'm building a set of wings for a BC-12D and I have the factory drawing for the wing design, for the stamped rib post war wings. My question is should I transfer the rib positions for the old spar locations, or go by the measurements on the print? I match drilled all the holes from the old spar to the new spars and all of those seem to be right on as far as measurments go, but the rib locations are off, in some cases as much as a quarter inch based on the witness marks from the old spars. I believe that the wings are as delivered from Taylorcraft because of the stamps on the spars and original TAC markings throughout the spars. Thanks much in advance

[Scott]

I believe the drawing you're referring to is actually an updated version of the truss rib wing. Problem is many of the updates made when the factory switched to the stamped ribs are not on that drawing. So for example it shows false ribs aft of the rear spar, and the spacing and lateral reinforcement at the front strut attach location are not shown. (Just going from memory here, which is risky for me these days!)

The ribs were positioned on the spars at the factory by a jig. I recall some inconsistencies when I reassembled mine based on my original TAC spars.

I ended up positioning and squaring up some key ribs first eg the root riib aileron bay ends, strut location ribs etc. You can verify locations with the leading and trailing edges and aileron cove and also use string to visualize the drag wire locations. The height of the ribs on each spar is also quite critical and for this pay close attention to your original spars.
S

[Dalton]

Thanks Scott, I sent you a message