A tough day

With the 71 - 73 matched holes drilled, the piece of aluminum (the F-1204D AFT BULKHEAD for those of without a program) gets removed and all of the new holes need to be duburred. That doesn't take long, although the holes on the inside edge of the center section have to be deburred by hand - the deburr bit that I use in my drill won't fit in there.

I considered quitting for the night after finishing that up because it hadn't been a terribly good day. In fact, it had been a rotten day. It was one of those days that everything I touch breaks, falls down, gets riven asunder by abnormally potent paranormal forces, or, as in the case at work, doesn't function correctly because I was in a hurry to get it done before leaving for vacation and did it very stupidly. Seriously, how distracted do you need to be to create a database distinctly for the purpose of supporting an automated report emailing system for the corporate bigwigs but neglect to actually put in a column to store email addresses?

Yeah, it was that kind of day.

After the holes are drilled and deburred, the bulkhead and a few other little pieces get riveted to the center section. The different holes require different rivets in different locations, so I marked the type of rivet to be used for each hole directly onto the bulkhead to avoid mistakes:





Some of the holes across the top are filled with AN470 style rivets (round head on top), but others take the AN426 flush head rivet. You know flush rivets are coming when you're instructed to machine countersink certain holes. The directions weren't super specific about which side of the center section was to be countersunk, but since the very next sentence has us dimpling the same holes in the bulkhead that is to be riveted on, it was pretty obvious that it was the outside of the center section that was to be countersunk.

What wasn't quite as obvious immediately was why there was a tolerance (.2544 - .2566, going from memory) provided for the diameter of the outer rim of the countersunk hole. Usually you just countersink far enough that the rivet sits flush. It didn't take me long to realize that it was to provide room for the inside of the dimpled skin to fit. I have a nice piece of sheet metal that Ted loaned me that has various sized holes drilled into it, so I just used the 1/4" hole to gauge the correct size of the coutersunk holes.

I'm not sure why only those holes get flush riveted in the first place, as opposed to the entire top row being flush riveted, but I'm guessing it is because that portion of the bulkhead with be very close to the edge of the fuel tank. Round head rivets could work against the side of the fuel tank and cause leaks. That's my guess, anyway. I'll find out for sure someday.

With the skin dimpled and the center section underneath the skin countersunk, the rivets lie pretty flush:



Those are just sitting in there, not yet squeezed. There are a few little parts that need to be prepped an riveted onto the assembly at the same time. I'm not in any huge hurry - last time I squeezed that many AD4 sized rivets I gave myself a third eye in my forehead when the rivet squeezer flew back and whacked me. That's the kind of thing that you remember for awhile!

Finally done with the %#^&@ 72 holes

Except there were only 71. No matter how many times I count, I can't find the 72nd hole. There are an additional two #11 size holes to drill, but if you count those you get 73.

72? It just ain't happening.



This was my first time using the new workbenches and they worked out just fine. They are just benches, after all. They're expected to work.

There are interesting parallels between building the benches and building an airplane, distilled down into these ten observations:

#1: It always takes longer than you think it will.
#2: Measure twice, cut once is good advice, but it's harder than it sounds.
#3: Countersinking is one of those things where it is possible to get too much of a good thing.
#4: You can't have too many clamps.
#5: You will be your own harshest critic.
#6: Having the right tool for the job can mask personal skill inadequacies; good tools are worth the money.
#7: It can be functional without being pretty.
#8: Always include the cost of fasteners in your estimates. They're cheap per unit cost, but you need a lot of them. See also: Clecos.
#9: Following the letter of the plan may not always be the best path, but shortcuts should be taken with thought, planning, and caution.
#10: It good to be done!

I was going to write a nice little article for the EAA magazine tying in the way those all dovetail with building the plane, but it seems that EAA doesn't accept member contributed articles anymore. A pity, that, but indicative of the direction EAA has been heading for awhile now. It's a big business now and is losing its grassroots feeling. To date that has been most readily observed at Oshkosh every year as it becomes more and more corporate-ized. It's not all bad; there are a lot more restrooms and conveniences, but in other ways, most notably the complete homogenization of food concessions, it's not nearly as nice. It's the same with the magazine: it's a much more attractive and professional looking periodical, but it has lost the "member newsletter" feeling. An improvement? Arguable; it depends wholly on what you want EAA to be.

Or, and this is at least equally possible if not more so, they simply moved the contribution guidelines to the deep, dark reaches of their web site where I just can't find them. I suppose I ought to just write it up anyway just for the fun of it.

In any event, the air drill was definitely worth the trip(s) to the hangar and the working conditions have been pleasant tucked back in the corner behind the RV-6, but I'll be happy to get back down to the basement where I can keep more regular hours.

Compressed air drilling?

In the immortal words of Mick Jagger, "it's a gas gas gas!"

Having had my fill of drilling holes through the quarter inch thick aluminum side of the center section with a relatively slow turning battery-operated drill after just five painfully slow holes, I thought it might be worth the effort to un-cleco the assembly and haul it up to the hangar where I could use an air drill.

I was right.

It's not much of a drill - it was a $38 special at Harbor Freight - but it gets the job done far more rapidly than the battery drill. I knocked out an additional thirteen holes in the half hour that I had available before leaving for Easter dinner.

With eighteen of the holes done, I'm 25% through this job. Another couple of hours of drilling should do it.

I'll be glad when it's done, figuring (possibly naively) that this is my best chance to ruin the it-has-to-be-expensive-just-by-looking-at-it center section.

Drill, Baby, Drill

I started match drilling the 72 holes that will be used to rivet a relatively flimsy bulkhead to the anything-but-flimsy center section today. I started out by removing the Harbor Freight springy clamps and replacing them with cleco clamps because the cleco clamps hold things together a lot tighter. Just how tight they hold was something I'd soon learn through up-close and personal experience. (In the parlance, they call that previous sentence "foreshadowing," and it is often accompanied by ominous orchestral music in movies. In lieu of that, just hum an ominous tune. Thank you.)



If you go get a magnifying glass to look at that picture, or even better just click on it for a larger version, you will note a couple of odd things. First, you will see the number '60' written in the bulkhead with a Sharpie(tm) pen. There are 72 holes to be match drilled but, as always, the devil is in knowing exactly which 72 holes are to be drilled. There are a couple that get drilled to a different size, you see, so those aren't counted in the 72. I thought I'd count the holes that I thought were included in the set and see if I reached 72. As a kind of verification, you see. What could be the harm in that? Better safe than sorry, as they say.

As I was leaning across the table counting, I reached the end of the range in which I could touch each hole. I grabbed the Sharpie to mark how far I had gone, and then attempted to record the count. As I was leaning on the center section, one of the cleco clamps got bumped. It spun around on the metal and clamped itself to the meaty part of the palm of my right hand.



I'm here to tell ya (so you aren't tempted to try it for yourself): that frikking HURTS. And where were the cleco pliers to I could get that thing off of my hand? Beats me! They're never around when you need them. Once I finally found the pliers and got the clamp off of my hand, I decided to commemorate the event with a little note on the bulkhead.

That ought to explain why my bulkhead says "OUCH!"

I took a break and came back later to start on the holes. I have, at this point, exactly five of the 72 done. The problem is that my battery operated electric drill turns slower than an air drill and it takes a period measured in actual minutes to drill each hole. And it's tiring! I can only do a few at a time, so this is really going to take awhile.

Plus there's that whole thing about the hand that I use to push the drill with: it still frikkin' hurts.

Slowly I turned....

I only had a brief opportunity to work on the plane, what with getting re-situated after our vacation and taking puppy Cabot to the vet for his third set of shots. And there was the matter of attending a racing event in support of Schmetterling's sister company, 8105 Racing. As a sponsor of sorts, I felt that I really ought to be there to represent the aviation arm of the conglomerate. This early in the racing season, it's already starting to get dark by the time the cars come out for their qualifying runs, which I only mention in defense of the graininess and sub-par focus of this picture:



I only stayed for the heat races so I don't know how things went in the feature, but it appears that the new, more powerful engine he's using this year is just what he needed to be able to run with the pack. Unfortunately, the new chassis isn't quite dialed in yet and he lost a lot of ground coming out of turn 4. There's a notable dip down into the apex of that turn and my theory (which is just that as I have never driven a NASCAR modified, nor have I driven so much as a tricycle around the Kil-Kare track) is that the car gets light as it climbs back out of the dip, causing a "loose" situation out of the turn as the car gets light on its wheels. None of the drivers seem to drift out to the wall for the very short straight before turn one; they seem to pinch the car down to keep it more in the middle of the straight. Again, with never having driven on the track myself I don't (and can't) know the reason for that. In any event, he finished his heat race in the second half of the field.

All I was able to get done on the fuselage was what seemed like it would be an easy step, but actually wasn't. The idea is to cleco the bottom skin onto the center section to ensure that the center section bulkhead that was clamped into place is correctly positioned. It ended up being a two-man job performed by me alone. I had to first situate the whole thing upside down in order to have access to the holes to be clecoed. I also needed to prop up the ends of the bottom skin:





I wasn't 100% sure if I had the skin right side up or not, but those elliptical openings will eventually be access ports and it seems like the covers should be recessed into the skin so they are flush:



Then I had to ever so slowly and carefully roll the thing back over to avoid damaging the skin. The airplane skin, that is. My own skin got a pretty nasty cut on my index finger when I scraped it against the sharp edge of the aluminum. I also had to find a way to prop it up so that it wasn't resting directly on the clecos. I did that with some scrap 2x4s I had laying around in the shop. What a great argument for never putting forth the effort to throw stuff away!





Now I just need to work up the nerve to drill those 72 very important holes!