Continuing on with the final steps before priming, I countersunk the #40 holes in the longerons, leaving out the holes that will be used to attach the empennage fairing later. The vice worked well here to hold the longeron securely while I used the pneumatic drill.
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| Countersinking 160 holes in the two tail cone longerons |
With only the skins left to dimple, I decided to continue with tail cone modifications picking up where I left off with the Rudder Cable Fairings. After receiving an MS20668-4 eye fitting from Amazon, I was able to make some small adjustments to the fit of the fairings and re-marked the hole locations.
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| Rudder cable fairings remarked after checking for cable end pass-through |
With everything marked, I cut the spacers on the band saw, and drilled the fairing holes with a 3/32" bit. I also match drilled the common holes in the fairings with the same bit.
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| Match drilling the rudder cable fairings |
Next I trimmed the fairings to size, cut an angle on the open ends of the fairings using the band saw and disc sander, and deburred all holes and edges.
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| Rudder cable fairings trimmed, drilled and deburred |
I then measured the fairing opening length and width at various locations, and marked those on the skins in preparation for enlarging the opening.
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| Rudder cable fairing dimensions transferred to side skins |
I am also putting an antenna doubler at the aft end of the tail cone as several other builders have done. The consensus is that if I do end up putting an antenna in that location, it is far easier to rivet in a doubler at this stage than later when the tail cone is assembled.
I used a paper template to determine the general location where I wanted the doubler, and also ensured that the template was at least 6" in length and 2" wide, as I have seen in my antenna research so far that most antenna bases are around 5" - 6" long and 1 1/4" - 1 3/4" wide.
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| Paper template used to determine size of aft tail cone antenna doubler |
I then traced the paper template onto a piece of 0.032" Aluminum from my empennage trim kit, and cut it out with the band saw. I decided to mark and space the rivet holes roughly 1" apart to match the rivet spacing in the tail cone skins, and then drilled those to 3/32".
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| Doubler cut from aluminum sheet, and holes marked and drilled |
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| Doubler ready for priming and attachment to tail cone bottom skin |
Prior to enlarging the skin rudder cable openings, I decided to practice first to make sure I had the technique dialed in as I didn't want to mess up the skins. I marked the dimensions of the opening on a scrap piece of aluminum, and proceeded to perform some test cuts. I found the following to work best
- Drill 5/16" holes in the left and right ends with a #30 pilot followed by the step drill
- Drill 3/32" holes in the top and bottom where the angle of the opening changes
- Use a dremel with a cut-off wheel to cut the remainder of the opening, cutting very carefully to ensure that the wheel does not go outside the marked lines. Notice the inadvertant cut beyond the opening in my first attempt below.
- Drill and cut 1/32" inside the lines, and use files to smooth the cuts to the line.
Below is the result of my two attempts. My first attempt (bottom) resulted in some mistakes as I got used to using the dremel and cut-off wheel, but my second attempt (top) came out much better, and I now feel more confident about working on the skins.
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| Practicing rudder cable fairing opening cuts prior to working on the skins |
In preparation for working on the bottom and side skins, I reorganized the tail cone parts so that I could keep the top skins out of the way, and cleaned up my workbench.
I then match drilled the aft antenna doubler to the bottom skin with a 3/32" bit, and reamed the holes to #40.
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| Magnets used to initially hold the doubler in place while match drilling |
After deburring the doubler holes, I proceeded to dimple the bottom skin and doubler holes. These were all accomplished using the DRDT-2.
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| Bottom skin holes all dimpled... |
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| ...except for the front row of holes that attach to the F-1006 bulkhead |
Next I tackled enlarging the holes in the side skins for the rudder cable fairings. I went very carefully here because I did not want to risk damaging the skin while cutting, but I was very happy with the end result.
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| Fairing hole edges measured, marked and center punched for pilot holes, and skin clamped to table. I used my 1" square aluminum tubes to support the skin above the table |
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| 3/32" and 5/16" pilot holes drilled using step drill |
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| Hole rough cut using cutoff wheel in Dremel. I made sure to stay at least 1/32" inside the lines. |
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| Finished hole after using files and scotchbrite pad |
I then cut the same opening in the left side skin.
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| Left side skin opening for rudder cable fairing |
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| Fairing temporarily help in place using magnets. Very nice fit! |
I'll use filler later to smooth over the edges, but I think the rudder cable fairings will give these holes a nice finished look.
The only task left on the fairings was to match drill the side skins to the fairing holes. After aligning the fairing pieces in place, and clamping them down, I match drilled the holes to 3/32", and final drilled all holes with a #40 reamer followed by a light deburring.
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| Fairing held in place with magnets and clamp |
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| Skin match-drilled to fairing |
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| Skin modifications for the fairing are complete! |
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| Fairing fits nicely into opening, and is angled to match the previous opening |
Returning to dimpling the remaining tail cone parts, I first dimpled the rudder cable fairing pieces, taking care to ensure the dimples were going in the right direction.
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| Rudder cable fairings dimpled and ready for priming |
Next I dimpled the side skins. All holes were dimpled using the DRDT-2 or the pneumatic squeezer, with some careful positioning and use of the narrow 3/32" female die for the holes around the curves.
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| Side skin dimpled and ready for priming |
As I was starting to prepare parts for priming, while reviewing the instructions for installing the autopilot servos, I saw that the pitch servo installation requires a #12 hole to be drilled into the bellcrank. This is easier to do prior to riveting, so I marked the hole location and drilled/reamed it to #12 to accept an AN3 bolt.
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| Autopilot servo bolt hole marked on bellcrank |
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| Bolt hole being enlarged to #17 on the drill press, followed by reaming to #12 |
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| Bellcrank bolt hole for servo drilled and deburred |
Time Taken: 12.1 hours
Dates: March 22 - April 2 2023
Tail Cone Total Time: 96.9 hours
RV-10 Build Total Time: 352.9 hours
Priming Total Time: 26.4 hours (not included in build time totals)
