Texas Flying Legends
By Chuck Cravens
This is a dimensionally stable, machined, cast aluminum toolingplate commonly called MIC-6 (MIC-6 ® is a registered trademark of Alcoa).
This month didn’t happen to have a great many visible changes to the P-47, so we will be brief this time.
Last month we saw the wing attach fittings ready to be magnetic particle tested and cad plated. Those finished parts are back. The other main project right now is building a fixture to begin assembling the forward fuselage.
Part number 89F11989, “Hinge Fitting Station 148 3/8th Cross tie-lower fuselage” is shown in side view here.
This would be the bottom side if the fitting were mounted in the fuselage.
Here we have the upper fuselage wing attach fitting from the same fuselage station. It would be mounted directly above the one in the preceding shots.
Another view of the upper attach fitting shows the appearance after all the heat treatment, Magnafluxing (magnetic particle inspection) and cadmium plating have been accomplished.
The same wing attachment parts, part number 89F11989 and number 89F11990 are shown incompletely finished form in this photo.
These wing attach fittings connect the cross tie that runs through the fuselage to the wing itself. They are machined from billet steel because the original forgings would be cost prohibitive in a small batch. It would take the better part of a million dollars to have forged blanks made for the eight unique parts plus a few spares necessary for one airplane. Billet machining cut that cost by a factor of 30.
The engineering drawing for the lower cross tie is depicted here. This Republic Aviation Corporation engineering drawing is where the fabrication shop starts the process of creating the finished part. You may need to enlarge it on your screen to read the various notations. If you look carefully , there is a smaller drawing of the part located below and to the left of the main drawing. This is an alternate form of the part, number 89F11989. The difference is that the fluted grooves on the edges of the tapered section are omitted. Since our P-47 had these alternate wing attach fittings, they are what we made.
89F11988 and 89F11987-2 are installed at fuselage station 99 5/8ths, so these are the forward wing attach fittings, upper and lower respectively.
Individual image of the upper forward attach fitting is depicted here.
Of the four different wing attach hinge fittings, the forward lower one looks to be the most complex to make.
The tooling plate will be used as a base for the P-47 fuselage fixture. It will be perfectly flat, leveled and therefore useful to measure up from and keep things ”true to the world” as the assembly is done.
The completed tail cone frame, covered in protective plastic, reflects off the tooling aluminum base plate.
This material will make up upright attachment stations on the fixture that will have the shape of fuselage former ribs. One is already cut and visible atop the blank material.
The fixture was rendered in CAD before starting. This is how it will appear when finished.
This rendering shows the lower fuselage mounted in the fixture.
Another view shows us the forward end of the lower fuselage in the fixture.
Eventually the upper fuselage will be built in the fixture and attached as it is assembled.