Sat Mar 7 2009

Fuselage miscellaneous

A couple days ago I used one of the milling machines after work to mill out the notch in the center support of the flap weldment. The milling cutter left a big wad of fuzzed / melted plastic at the edges.

However, a few minutes with a utility knife and a file took care of that.

After cutting the block in half, I positioned it on the weldment and marked the tunnel cover at the edge of the block. This cover needs cut out in the corner so that you don't have to remove the block to allow removal of the cover.

Kerin's out of town for the weekend, so Snickers has been hanging out with me in the shop.

Here's the cover after trimming the corner out. Note that to determine the width of this notch, I drew a centerline along the line of #8 holes then measured 13/32 from that line to define the edge of the cutout. Since the block is 3/4 inch wide and the holes are on center, that should allow 1/32 extra clearance.

The side clearance looks great. The end clearance is a bit much, but doesn't look too bad. It's on the order of 1/16 inch.

After that I decided to do the remaining work required to fit the flap actuator cover. I'm glad I ordered this stubby 1/4 threaded shank drill for my angle drill...

...because I needed to fit it between the front channel of the flap actuator cover to transfer drill through the side skins.

Next, I needed to notch out the side of the flap actuator cover to allow clearance for the head of the AN-4 bolt. It looks like the bolt head will fit in a 1/2 inch diameter hole, so that's the size I'll notch out the side plate to.

In order to do a nice job of notching out this side plate, I wanted to use the unibit, but the hole is too close to the edge. I knew I'd really mess this part up if I just went at it with the unibit, so I decided to use a piece of scrap .063 thick aluminum as a backer plate.

After drilling a 1/4 inch hole in the backer plate, then matching and clamping it to the side plate...

...I was ready to drill with the unibit.

Gah! The unibit grabbed the edge of the thin sheet. Apparently I should have sandwiched the thin sheet between two scrap pieces of .063. 20/20 Hindsight. Sigh. Hopefully the radius on the corners will eliminate this unsightly problem.

Here's the finished notch. It came out reasonably well, but you can see the sheet is slightly deformed where the bit grabbed the edge.

After clamping the F-785A in position and reinstalling the tunnel cover, I held the F-785B in position to mark it's desired location. Then I removed the tunnel cover and F-785B and used the holes in the tunnel cover to drill through the flanges of the F-785B bracket.

Putting the pieces back in the airplane allowed me to drill through the F-785B into the F-785A. Note the magnet holding the F-785A to the F-785B bracket.

After that I match drilled through the F-705 rear spar bulkhead into the top of the F-785A channel. I later opened these holes up to #19 for a pair of #8 screws, but didn't get a photo.

Next I match drilled the F-785A to the side the side covers.

I had planned on match drilling these F-758 brackets to the front channel of the flap actuator enclosure, but the holes are off by a half of a hole (possibly a little more). It looks like I'm going to have to custom fabricate two new F-758 brackets. Grr.