4.0 Hours –
Today, I’m back to work on the cabin frame, and I achieved my goal for the day of finishing the installation.
The first thing I had to do was to finish fitting the brackets that tie the frame to the F-705 bulkhead. I had already set the position of these brackets, but due to the curvature of the fuselage, the aft end of the brackets overhangs the edge of the fuselage. The brackets must be filed until the shape matches the fuselage’s contour so that the skin will lay flat against the brackets. Removing the excess material was relatively easy…a few passes on the belt sander, then some time with the vixen file. Eventually, the contours matched and I was able to move on.
The aft ends of the cabin frame brackets overhang the edges of the fuselage by just a bit. They have to be contoured to match the curve of the fuselage.
After some filing, the brackets follow the edge of the fuselage nicely.
The plans have a specific order for drilling all the holes in the brackets. First, the skin is clecoed into position and the forward two holes are drilled using the forward holes in the skin as a guide. For now, these holes were only drilled to #30, but they’ll be enlarged and tapped for #8 screws later.
The forward holes are drilled through the brackets using the holes in the skin as a guide. These will be enlarged and tapped for a #8 screw later on.
After drilling the forward holes through the brackets, the cabin frame is put back in place so all the holes can be match drilled through the frame.
Next, the skin was pulled back and the aft holes were drilled. I already had these holes drilled in the brackets, so it was just a mater of transferring the holes to the cabin frame. These holes were enlarged to #12 for #10 screws.
The aft holes are enlarged to accept a #10 screw.
The next step was the fun one. I had to countersink the brackets for the screw heads. I ended up doing this by hand because the curvature of the brackets made it tough to position a countersink cage. Anyway, after a lot of hand cranking, checking the depth, and cranking some more, I had some nicely countersunk holes. At this point, I moved the skin back into position and checked to make sure it would lie flat against the brackets. It did, so I moved on.
All of the holes are countersunk. The aft screws will be behind the skin and the forward screws will be visible from the outside. The aft countersinks have to be a bit large since the surface isn’t flat.
Another view with the skin and all the screws in place. The fit is perfect.
The right side of the frame as seen from the front. I’m pretty happy with the fit of the skin/bracket/frame. It would have been nice to get the bottom to look a bit nicer, but it was a lot of work just to get it to what it is!
Finally, the holes on the inside of the frame have to be drilled. Again, this was fairly simple…locate the position and drill. Each side of the frame was drilled for two AN3 bolts.
The final step was to drill the holes on the inside of the frame. Two AN3 bolts per side.
I decided to go ahead and prime and paint all of the cabin frame parts now. Once the paint dries, I’ll assemble them, but then the assembly will get set aside for some time. Putting it on the fuselage now would just make it be in the way. Now that the frame is done, its time to move back to the forward fuselage and work on the sub-panel and panel assemblies.
Filed under: Center Fuselage, Construction, Fuselage Tagged: cabin frame, center fuselage, fuselage, RV-7
