This is the lower section of diaphragm that has been sanded on the forward side to remove the surface corrosion. The rub strip on the aft edge has done its job and has been fretted away in several locations. It is going to be replaced. (image via Pioneer Aero)
A close up of the rub strip on the aft edge showing how it has been worn away. This has happened in several locations and is going to be replaced. (image via Pioneer Aero)
This is the lower section of diaphragm. The rub strip on the aft edge has done its job and has been fretted away in several locations. It was originally spot welded on. Here it is being carefully chiseled off with no damage being caused to the diaphragm itself. You can see the accumulated oil and grime from years gone past. This is only seen under the sections that have loosened from use, but almost none on the tightly riveted and spot welded parts. (image via Pioneer Aero)
This is the lower section of diaphragm after the old rub strip on the aft edge was removed, but prior to the refurbishment of the underlying material. The remains of the spot welds which can be seen here were carefully ground off and a replacement piece of rub strip fabricated which will eventually be riveted in place. (image via Pioneer Aero)
The various sections of the diaphragm have all been sanded or bead blasted as required to remove all of the dirt, old oil and surface corrosion. Replacement rub strip sections can been seen at the lower right; they are now ready to be primed prior to having the repairs riveted together and the new Dzus springs and anchor nuts riveted in place. (image via Pioneer Aero)
More progress forward of the firewall is taking place! Pioneer Aero is continuing to work on the dish pan, addressing several areas which show signs of wear. The engineers who originally designed the Dauntless anticipated some of these locations where metal vibrates against metal, installing rub strips at those spots to create a barrier of sacrificial metal which could be replaced, when needed, during routine maintenance.
These rub strips were attached via a combination of rivets and spot welds. The team at Pioneer Aero carefully chiseled them off to allow the installation of replacement parts. It is interesting to note how the rub strip actually did its job in several places, with the original device more or less rubbed through.
Pioneer Aero technicians also sanded and  bead blasted the dish pan components, to remove eighty years of accreted dirt, oil and surface corrosion. You can see the replacement sections of rub strip alongside the original, cleaned-up pieces. All of these sections are now ready to be primer-painted before having the repairs riveted together and the new Dzus spring and anchor nuts installed.