Tailcone tab fluting

A simple instruction in the manual (Tailcone construction, Page 10-12, step 3) has me a bit puzzled and I was looking for the "Ah ha" moment that hasn't come. So, I'm reaching out. The instruction states:

"The flange along the top of the F-1006 bulkhead and the F-1007, -8, and -9 Frames is comprised of tabs with either one, two, or three punched holes. In preparation for clecoing on the F-1074 and F-1075 top skins, heavily flute the tabs of the bulkhead and frames which have two punched holes".

What? Why? Which way? Why only the ones with 2 holes? Why didn't this get done prior to clecoing the bulkheads and frames into the skins?

Again, I'm probably overthinking this, but I would sure love some clarification.

The flute goes in-ward so the skins can lay flat against the bulk heads.

The flutes pull the "2-holes" together enough to make them align with the holes in the skins.

The question you should be asking is "What is heavily?" The answer is one full-sized (deep) flute right between the two holes. Not many flutes between them.

With one flute on the two hole tabs everything will match up like a dream.

Ah ha moment (courtesy of Phil)

Thanks Phil. It's odd that the instructions say "heavily" and don't define what it is you are trying to achieve. That said, I followed your lead and things turned out well. Thanks for the quick reply!

Glad you got it... I still think the tailcone is the most enjoyable part of the entire kit to assemble. That was a blast and unfortunately that section when by way too quickly.

I just did that today and got me puzzeled at first. I realized most of those tabs with two holes on the corners. I did not flute the one in the middle on top.

Sorry for bringing this thread back from the dead, but I have a question related to the same step.

I purchased my empennage kit in a partially completed state. The previous builder had obviously gone through this step, as subsequent steps that relied on it have been completed, however, the tabs in question were not fluted.

I'm not sure it's necessary, since almost all of the holes in the tabs match very well with the holes in the skins already. Is fluting these tabs strictly necessary, or is it simply to make the holes line up?

IIRC, it's so the rivet holes on the bulkhead will sit flat against the skin more than just getting the holes to line up.

Jesse said:

IIRC, it's so the rivet holes on the bulkhead will sit flat against the skin more than just getting the holes to line up.

Click to expand...

Makes sense. The less contact between the tabs and the skin, the more the skin can follow its natural curve between anchor points.