A brief break

For various and sundry reasons, and none of them truly adequate, I haven't been flying the RV-6 as much as I ought. Last night was clear, calm, and compellingly conducive to completing a competency-enhancing collection of quality practice landings, so rather than absent myself to the basement shop to labor over cold, cantankerous aluminum, I carried myself to the airport for some flying.

It's good that I did, if my first landing was any indication. Had I gone any longer and let my skills atrophy any further, I might actually have literally left parts of the airplane on the runway rather just thinking that I might have. Fearing the obvious threat of permanent damage, the plane behaved much better for the remainder of the evening.

I was back at it tonight, but only briefly. The sum total of tonight's efforts was getting a set of doublers partially attached to the bulkhead that I've been working on. These are moderately tricky in that they use a few different rivets and, as is getting to be the norm, have collections of holes that are to be kept rivet free.

First there were some #4s to be squeezed:





Once squeezed, the #4 rivets get covered up with the doublers. That was kind of weird - typically any rivet that will have something on top of it is a flush rivet, but these fit up into the "folds" of the two doubler halves:



These doublers provide the strength required to hold the second set of wing spar tabs. Obviously there's going to be quite a load transferred from the wing roots through to the fuselage from these tabs, judging from the dense packing of holes that will be filled with #4 solid rivets.

I pulled the dozen blind rivets in each set of doublers but left the #4s for another day.

Squeezing all of those is going to be fun. Maybe I'll go flying again...

I have seen my future....

... and it is (prepare yourself!) nutplates. Shocking!

After retrieving my Uni-bits from the hangar, I was ready to start preparing YAB. What's a YAB? Oh, that's "Yet Another Bulkhead." I left out a letter or two in the interest of brevity.

Twenty-three nutplates. Two countersunk holes each. Plus another six #30 holes to be countersunk with the 120° bit. That means CS-4 blind rivets instead of squeezed #4 rivets sometime in my future, so there is that. But it still added up to fifty-two holes to be countersunk.



I shouldn't sound so down about it - I actually like countersinking. The micro-countersink thingy has a solid feeling of precision mixed with get-outta-my-way brute force that I somehow find enjoyable to use. But still... fifty-two! That naturally left a lot of metal shavings scattered all over the work bench, so I somewhat absently lit up the powerful shop-vac to apply some housekeeper's suction to the mess. As I was vacuuming around, I heard and felt a thunk in the hose and saw something larger than a metal shaving go flying up the nozzle. I thought it must have been one of the little lengths of cut up wooden paint stirring sticks that I keep around to support thin aluminum when I cut it with the band saw. I was thinking of just letting it go at that, but thought better of it and opened the vac to see what I had netted.



Oh. A little plastic bag filled with the three not-currently-in-use countersink bits. I would have never found those!

Retrieved:



The countersinking had taken up most of the hour that I had to spend in the shop, and I hadn't even gotten to the part where I needed to use the Uni-bit! I didn't figure that part would take too long, though. I don't like using the Uni-bit for precisely the reason that I thought the job would go quickly: they make a big hole very quickly. It actually takes quite a bit (heh) of caution to avoid going a step too far and making the hole too big. The big hole on the left would have to be finished by removing the small amount of metal at the bottom of the hole. That would be done with cutters and files.



Starting with the big hole:



Even though the larger bit on the right has a 7/16" step, I thought it would be safer to use the more tapered bit on the left for the 7/16" holes because it would give me a wider step between holes, hopefully providing the buffer I'd need to keep from over-drilling the holes. The big bit worked fine on the 3/4" hole since that was the maximum diameter of the bit anyway.





I put the filing off for last. The plans suggested a round file for that. I ought to look into getting one. I just used my little jeweler's files - that took awhile!



I finished it up just as my hour expired.

Rolling along...

This morning I riveted yet another brace to the posts that hold the bushings that hold the pins that hold in the wings that will hopefully reliably hold my fragile skeleton aloft over central Ohio.

Oh, and I met an old lady that swallowed a fly. I won't go into why she swallowed a fly...

The directions for riveting in the braces insisted that four holes remain free of rivets. In light of my utter and complete failure to do so with a rivet hole yesterday, I've applied another layer of protection to my reminder process:



Clecos with duct tape! If that doesn't do the trick, nothing will.

Note also that I have started a new practice: I also put a few rivets in along with the clecos because they are just ever so slightly thicker than the clecos. They force the parts into the exact alignment, rather then the almost exact alignment provided by the clecos.

With the brace in place to hold the posts rigid, the only remaining thing to do in that area is to install the rollers that the wing spars will (see if you can guess.....) roll across as they are slid into the side of the fuselage.



That was all fairly routine, but the next step was anything but. I've assembled any number of bearing assemblies thus far, and it is not unusual at all to have one side of the assembly countersunk for a flush rivet. This time, though, I had to countersink both sides and do a "double flush" rivet. Sorry, no pithy comment on that will be forthcoming. It's a target rich environment and I just don't trust myself.

I had to look up what it meant and more importantly, how to do it. Basically you just squeeze the ever-luvin' stuffing out of the rivet and it will (in theory) end up being flush on both sides. The second countersunk hole is to provide room for the shop head (the one I squeeze) to expand.





I can't say that it worked all that well.



There's only so much squeezing for me to give, alas.

If push comes to shove, I'll grind them flush with the Dremel. You know how I am with the Dremel: just give me an excuse...



Next was what should have been a routine separating and marking of parts. You know what happens any time I say "should have been," don't you?

Here's the directive:



Here is the "raw" part to compare against:



Note the relative positions of the holes that I labeled '1' and '2' with the holes in the hatched are of the drawing. Looks just right, right? But you also have to consider the "THESE TWO SETS OF HOLES SLIGHTLY FARTHER APART THAN THE OTHERS" statement. Because it is so very explicit, it is the only choice for determining the correct orientation of the part. The problem was, I couldn't see any difference in the spacing, at least not definitively enough to overrule the bias introduced by the overwhelming certainty that I was correctly gauging the relative positions of holes '1' and '2' - pretty compelling evidence in my book.

I needed to consult an expert for a tiebreaker. I called in Mr. Micrometer.





According to him, holes '1' and '2' were to be ignored. I'm glad I asked!

This is all in preparation for putting together yet another bulkhead. This one will require drilling with a Uni-bit, and I keep that particular device at the hangar. It will have to wait until tomorrow.