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Empennage

Elevators ready for priming

I’m on holidays. Yay! Had a great Christmas catching up with the family. The outlaws (in-laws) are visiting and my father-in-law was keen to have a look at my plane. Naturally “looking” became “building”.

I needed something to dimple the holes in the narrow tapers. I didn’t want to use the sacrificial rivet method and I didn’t want to bend the flanges out. I thought of using my back riveting plate and making a female die in it, however it was too thick to fit in between the flanges. We did however manage to find some old angle iron that I had lying around.

I started by cleaning off the surface rust using my die grinder. This worked really well and was much easier than a wire brush and sand paper!

I then gave the angle a quick coat of self-etching primer so it won’t rust again, or scratch my precious parts.

Using the flanges as a guide, I then marked the position of the hole so that I could reach the holes on the ribs to be dimpled. I then set up the drill press with the #40 bit and drilled the hole using a small amount of oil for lubrication so that the bit didn’t jam.

I then replaced the #40 with a large drill that had a diameter larger than the countersink I needed. I then slowly and carefully countersunk the hole to the required diameter. I measured the female dimple die using my Vernier’s.

Once I was happy with the countersink, I checked for fit using my male dimple die. All good!


I set up my new taper die on the bench and used a spare bolt as a driver to dimple the holes I needed to. This thing worked a treat and I was able to dimple all the holes I couldn’t reach with the squeezer.


With all the elevator parts dimpled, I went back to the plans to see what edge needed to be done. It doesn’t mention it anywhere in the instructions, but the drawings show a section on the right elevator counterweight that needs to be removed to offset the weight of the paint used on the aircraft. I marked out the section that needed to be removed using some masking tape. The tape was easier that using a Sharpie on a curved surface. The old father-in-law’s idea. Thanks Bill!

Using a hacksaw, I cut most of the area to be removed out. I then used my vixen file to clean up the surfaces and to remove the last bits here and there. I also used a round file to make a radius.

Work was now complete on the elevators so I moved on to the trim tab. The plans called for the trim tab skin to be bent to the required angle. Using the bending brake and dowel, I bent the skin using my hands. This was much easier than the elevators and my first bend was enough to reach the desired angle.

Using the outboard end as a guide, I marked out the angle required for my bending block on a spare piece of timber.

I then clamped the trim tab into position and got ready to bend.

The plans called for the bottom tab to be bent first. Naturally, I had the the top tab in position so I unclamped everything and set up the correct tab for bending. 🙂

I followed the plans on how to bend the tab and it all went well. Using a wood block I managed to bend the tabby about 30 degrees. I then used my rivet gun and mushroom head set to 10 psi to bend the tab the rest of the way.

I bent the other tab without any dramas and swapped to the inboard side. I found that the taper on the bending block was too thick for this end.

Once again the old father-in-law provided the solution. By cutting a slice off the bottom edge of the bending block, I could make the taper thinner and make it fit properly.

This worked perfectly and allowed the taper to fit.

I then bent both tabs on the inboard end without too much difficulty. I noticed on both ends that the tabs don’t perfectly line up on the trailing edge and that a small gap exists between them. I’ll probably fill in these gaps with fibreglass to make it look better. I clecoed in the trim tab spar to check for fit. It was all good.

The plans then called for the trim tab horns to be clamped together. I broke out the clips from the electric trim kit and inserted both of them to make sure the horns were aligned.

I then clecoed the horns onto the trim tab and match drilled the required holes.

Next was match drilling the piano hinge. I marked the position for the first hole on the inboard side, and marked the line down the piano hinge for the required distance from the hinge for all the remaining holes. I found it difficult to keep the skin, spar and hinge all aligned for match drilling, so I removed the spar to make it easier. In hind sight, I would leave this in position as my upcoming mistake was triggered by the removal of the spar.

I then match drilled the hinge. All was going all until I went to cleco everything together and the holes didn’t line up. Uh ho! I had match drilled the bottom flange rather than the top flange. After a few moments of exploring my vocabulary of profanity, I realised I had just trashed my first part of the build. Fortunately it is a small and easily replaceable piece, however it was rather annoying. I’ll re-order the piece and build on.

I called it a night at this point. Build time 4 hours (1.5 on the elevators and 2.5 on the trim tab).

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About gstrack

Husband and father of 2. Control & Instrumentation Engineer. Flying nut. Gadget geek.

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