·:[ Darryl's Coot Building Journal ]:·
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[7 hrs] Here are some ribs for the vertical fin I built over the last couple of weeks.

The two ribs with lightening holes are flanged. These ribs were built out of some old paper-coated 2024-T3 aluminium 0.02″ stock that I had laying around. The material underneath is a brand new sheet of 12′ x 4′ x 0.02″ 2024-T3 for more parts. I also got a new sheet of 12′ x 4′ x 0.016″ 2024-T3 to use in the vertical fin and other tail components.

This evening, I rough-cut out the vertical fin skins from the 0.02″ 2024.

[4 hrs] After taking a detour to build a brake, I’ve actually created what appears to be an airworthy part. This is the 314-1-6 rib that is at the bottom of the vertical fin. It starts with 0.02″ 2024 T3 aluminium (coated with paper), with the pattern transfered onto it:

After drilling corner holes, cutting, bending and drilling lightening holes, the resulting rib looks like this:

Notice that there is also a 314-1-18 rib below the -6 rib. This is the top rib in the v. fin assembly, and I made it before making the brake. The rather mediocre result of making this rib without a brake prompted me to find a better solution. I’ll remake the -18 rib, since this is part of the structure on which a critical pulley for the elevator is mounted.

The last thing needed for the -6 rib is to flange the lightening holes. That will require making some flanging dies.

[2 hrs] I straightened out all the bent aluminum on the vertical fin, and then reassembled most of it, held together by Clecos

Don’t get me wrong…I didn’t straighten the bent pieces (seen here and here) in order to use them. Rather, I am using the old assembled vertical fin as a jig to test the fit for new pieces as I build them. (As I said before, almost everything made of aluminum will have to be replaced.)

I also sandblasted a few more steel parts from the vertical fin assembly.

[7 hrs] It turns out that my tail is probably not from Forney Engineering. Russ Milham noticed some differences in the control box that I hadn’t.

This weekend, I Disassembled the entire damaged tail except for the elevator control box.

Almost everything made of aluminum will have to be replaced. Either things are damaged beyond repair or there is some other problem, like rivet holes too close to edges, extra holes, or just plain badly made.

I’ve also started sandblasting the steel parts from the tail assembly.

[2.0 hrs] I started work on the tail pieces this week–mostly cleaning, inspection and studying drawings.

The parts-Coot I purchased in late 1999 included a crunched empennage. Sometime in the late 1980s, the 60% complete Coot was being trailered from North Dakota to Arizona when the owner suffered a heart attack and the vehicle and trailer left the road. The trailer flipped and caused damage to the engine pylon and the tail assembly. A subsequent owner started removing rivets from the assembly, and that is what you see in the photos below (click on photos for a large version).

I’ve just started cleaning and inspecting the vertical fin. Here is the assembly:


This looks to be a Forney Engineering tail assembly. I base that on the fact that (1) I received the drawings for the Forney tail assembly kit with the plane, and (2) the two center ribs are parallel to each other (see drawing 314-1 for reference). Molt Taylor had the upper of the two ribs sloping upward away from the plane.

The damage is obvious. A buckeled front spar:

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And a crinkled leading edge skin and rib near the tip:

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