Friday, January 15, 2010

The Final Stretch, or The End of the Beginning

There's not much left to do on the tail cone. There's still some riveting to be done, but about a third of that got knocked out a couple of afternoons ago when we had temperatures in the mid 30's. After the single digits and low teens of the last few weeks, it was nice to be able to work with the natural light from having the hangar door open and without the roar of the Cone of Comfort heater. All that's left to do is rivet on the top skin:

I found when I got to the step before clecoing on the top skin that there was still a small part back in the shop the needed to be prepped. It's nothing more that a small half rib that will be used to screw the bottom of the vertical stab fairing into. It has eight nutplates for the screws to go into. The nutplates and the rib itself need to be dimpled to allow the screws to go in flush with the outer skin. The dimpling of the rib flanges is quite easy and only took a few moments:

The nutplates themselves need to be dimpled too. If you remember back to the early days of the vertical stab, I had to do it then too. I was momentarily taken aback by this problem when I tried to dimple the first one:

See how the edge of the female dimple die will cause the nutplate to bend if I squeeze it this way? That had be befuddled for a minute or two until I remembered that there is a special carved down die for this kind of job.

Here's a side by side comparison:

You can see the difference when using the cut down die:

See? Nice and flat. The thing is, though, those dies aren't cheap. Cutting one down like that has got to be somewhat painful in a pecuniary sense. Given that the role of these nutplates is nothing more than providing a threaded receptacle for a few screws, I'm not convinced that I would even bother. I have the luxury of borrowed tools, so I never needed to make this decision. Just to see what it would look like, I went ahead and clecoed an undimpled nutplate next to one that had been dimpled:

The difference is discernible, but I don't know that I'd call it significant. What? You can't see the difference? Well, the nutplate on the left in the top image is the undimpled one. See what I mean? Discernible but not significant. Let your conscience be the judge as to whether the difference is worth the sacrifice of a dimple die or not.

Here's the half rib all ready to go out to the hangar:

Having had a riveting session interrupted by my failure to bring all of the parts that I needed out to the hangar, I read ahead to make sure that it wouldn't happen again. Lucky I did!

I was going to need an F-1210B to slide through the slot in the F-1278 Top Skin. And therein was a problem. I went over to the parts shelf to retrieve the part for deburring and preparation, but it wasn't there. In fact, there wasn't much of anything there. All I could find were a few parts that will eventually become the tray the holds the electric trim motor. I thought that maybe I had already grabbed the part off of the shelf to get it ready back when I was first preparing to install the tail skins, but it was nowhere to be seen on my work bench. A frantic search of the workbench and its environs produced no sign of the wayward part.

"Now where could I have put it?"

"Is it hiding in the toolbox? Nope. Behind the drill press? Nope. Oh for crying out loud, how could I have lost it??"

Five minutes of ever more frantic searching later:

"Oh, here it is!

"Already installed!!"

"Man, what an idiot I am!"

"I'm done with this for tonight. I think I could use a little helicopter flying."

And that's what I did.

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