Today I started mounting the steel doublers required to beef up the wing attach points on the left wing. The manual calls out for two doublers, one on the inside top and inside bottom of each spar. Apparently, there was a mistake at the factory and the rear bottom hole was drilled oversize for some unknown reason. After a call to the factory discussing the repair, it was suggested that I add another doubler on the bottom outside of the spar. I asked if there was any reason not to add them at all stations to beef up the wing attach points? The answer was no so I asked for another set of doublers so I could "double" up on all of them. This will give twice the wear surface for the bolts and pins, can't be a bad thing.
So, I began by preparing the eight doublers for installation. I had to drill out, using a #40 bit, the three rivet holes and the 5/16" bolt holes in each doubler.
Next, using the 5/16" bolt to align the top doubler with the spar, I clamped it in place and used the #40 hole in the doubler as a guide to drill through the spar. Once drilled, I cleco'd it in place which clamped the doubler while I drilled the remaining two holes in the spar. I then placed the second doubler on the inside of the spar aligning it with the bolt and the clecos previously installed. Once both doublers were in place, I used a #30 bit and match drilled the rivet holes.
Once all the doublers were drilled out, deburred, sanded and cleaned, I mixed just enough Hysol to do two of the doublers at a time since they are top and bottom of the same 5/16" hole. I gooped the Hysol on the mating surfaces of the doublers a put them in place using a #30 cleco in the middle rivet hole to secure them for riveting.
I repeated the process for the remaining doublers and left them to cure overnight.
