Monday, December 7, 2009

Starting on the tail cone

It's been awhile since I've worked on the RV-12, primarily due to competing demands from my other (still broken!!) airplane and a smattering of Xmas preparation chores. I'm also slightly reluctant to start on the part of the kit that will inexorably take me down the path of working out in the winter elements when the assembly gets to big to keep in the basement shop. That may not be too bad, at least until January and/or February. I've spent quite a few hours out in the 30-ish degree hangar working on the RV-6 and, while not completely comfortable, have not yet lost any digits to frostbite.

The two most daunting prospects in the construction of the tail cone, at least from where I'm standing, are the preparation of the skins and the preparation of the skins. I mention the skins twice because these particular skins require a relatively particular preparation. Sure, there's the normal drudgery of removing the blue vinyl and deburring dozens and dozens of holes, but there's the new wrinkle (cue José Jiménez (2:40): "Oh, I hope not!") with these skins: the edges have to be "broken."

Broken?? Again, "Oh, I hope not!"

My 'broken' they mean that the edges need to be bent down a few degrees where they will join or overlap other edges. By bending the edges down, the tightening caused by pulling the rivets will not curl up the edges as much. Or so they say.

The breaking of the edges requires a specialty tool (presumably called an edge breaker) which, clever fellow that I am, I ordered at the same time I ordered the 120 degree countersink bit. It's an odd looking little device:

But that would come later. First, the blue vinyl has to go. I used the same "cut it into boxes" methodology introduced in the peeling of the horizontal stab skins, but this time I added a sophisticated step that I hear all of the pros use: I let the soldering iron roll off of the heat-proof stand on rest on the side of a rubber glove left lying around after some of the fiberglass work that I had recently done on the RV-6 cowls:

Naturally you're wondering how that simplifies the job of removing the onerous blue vinyl. Well, it doesn't. But golly, it sure does generate an awful stench! What's the benefit of that, you say? Nothing. Nothing at all. In fact, you force me to admit it: I had no deliberate intention of burning the rubber glove. In retrospect, though, I wish it had been the least of my careless moments...

Anyway, on to deburring:

That took awhile. These skins are huge!

Finally it was time for the step that I have been stewing about for weeks. You see, the correct tool and method for breaking the edges has generated quite a bit of discussion on the forums. I've read every available opinion on which tool to use and exactly how to use it. I've seen the horror stories. In short, I've worked myself into a state of nerves over the whole thing.

The rectification for that is, of course, careful study of the plans and instructions, followed by an introspective visualization of the process. Concentration is key. There's no room for a mistake here. Caution is of the utmost importance.

Which is why I could have just screamed when I was a third of the way down the edge of the first skin and realized that I was bending (breaking) it in the precisely wrong direction. Out, not in. Twisted down, not up. One hundred and eighty degrees off course.

Well then.

What to do.

As it turns out, all you have to do is start over and bend it in the correct direction and all is forgiven.

Phew, that's a relief!!

That was enough stress for one night, so I set the tools down. Besides, I have another problem to figure out. As I was reading ahead in the plans, I ran into a little confusion:

If you can't read that, it says "align the holes in the four-hole flange of the angle to the full-scale illustration in Figure 2."

Sounds easy enough, but if you look closely you will see that the holes do not line up. And what have we learned about this kit? If it doesn't look right, it probably isn't. What I need to determine is whether the holes are supposed to line up after the fluting. It's hard to believe that they will, but I've learned that fluting can make a pretty big difference in a lot of ways. To be safe, though, I'm going to do a little forum research and see if anyone else has mentioned anything about this before doing anything to this part.

1 comment:

Anonymous said...


I've never read or heard of anyone trying this but would using a hair dryer to warm up the blue vinyl help it to come off more easily? Not hot - just warm! Not sure how it would affect the alclad if at all.

Gene Spooner
Greensboro, NC

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