<June 29, 2008>

Baggage Ribs & Miscellanous Fuselage Drilling

With the family due back in a few hours, the pressure was on to accomplish what I wanted to. On the to-do list today was some miscellaneous fuselage drilling and the baggage ribs.

Just below the fuel tank attach bracket is where a flush screw penetrates the skins and lower longeron. I didn't have a #12 piloted countersink so I used my standard #30 countersink on the hole first, with the goal of then enlarging it with my #12 reamer. I tested this by first drilling a #30 hole in some thick scrap aluminum, then countersinking the using a #30 cutter, then enlarging the hole with the reamer. It seemed to work fine, so I went to work on the fuse. This picture was taken after I countersunk, but before I englarged the hole.

Edit: I forgot to install the F-796 Tank Attach Brackets before drilling the hole. Oh well, I will have to do that later.

After reaming the hole with my #12 piloted reamer (pointy tip), the screw fit beautifully.

I then enlarged the pilot holes for the fuel vents to 7/16".

Same here too… the fuel vent lines get enlarged to 7/16".

I needed to drill 1" holes in the side skins for the fuel line grommets, but I didn't have a step-drill that large, so a quick call to my A&P/Machinist neighbor yielded me this monster. It's big, real big! I figured out which step to use and put some tape around it before drilling. There was no 1.000" step, but there was one slightly smaller and slightly larger. I chose the smaller one as I figured when I deburred the hole it would get a little larger.

My plan worked! After deburring with a little sandpaper and some Scotchbrite this hole measures 1.000" on the digital caliper. It doesn't need to be that accurate for a rubber grommet, but it is nice to know I did something right.

I then installed and drilled the F-722 and F-724 Baggage Bulkheads. When I drilled the F-724s through the skin and corner ribs I noticed that the inboard holes were very close to the edge of the flange. I am going to have to look into this. Actually, I made a small goof on one side. I drilled the bottom flange before I had the part completely clecoe'd and drilled to the side skin. This resulted in the part moving during drilling and a misalignment of the outboard hole (pictured). To solve this I am probably going to cut off the tab and fabricate a new wider version which will solve my goof and the edge distance issue with the inboard rivet.

I installed the F-750 Aft Baggage Covers and drilled them to the bulkheads.

With all the interior drilling now almost done, I took some time to look over the fuselage and take note of all the spots I hadn't drilled yet. I was quite surprised to find there were lots of places that hadn't been drilled, one of which is the skin to the F-715 Outboard Seat Ribs and F-623 Corner Ribs. So out came the drill again.

With the seat ribs drilled and clecoed to the skins, I could now drill the top flanges of the ribs to the seat floors. This wasn't hard, but it did require the angle drill.

I then drilled the far aft row of holes where the forward side skins overlap the aft side skins. For some reason I hadn't done this already but I don't think the instructions ever said to do it. I found a few other rows of rivets that hadn't been drilled yet either. I don't know if I missed something, or if it was the directions again, but I took care of it now while the fuselage was still assembled.

All done (drilled). The instructions say that that there is a small "laundry list" of tasks to accomplish before final assembly, but before I start the list I thought it would be a good time to step back and admire the big picture. OK, that's enough for today. The wife should be home soon so it is time to go clean up the mess I have made in the house.