Horizontal Stabilizer 8-8-1 to 8-9-6
With all skeleton parts (edges and lightening holes) deburred, it was now time to start assembling the horizontal stabilizer. I attached a couple of 2x4 pieces to the edge of my workbench so that I could place the spar on it, and have the ribs hang down as I match-drilled the ribs to the spar.
When all the ribs had been clecoed in position, and in the correct orientation to the front spar, I proceed to match-drill all 1/8" holes common to the ribs and spar.
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| Horizontal stabilizer starting to take shape off the end of my workbench |
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| Laying the horizontal stabilizer skeleton on the work bench gives a sense of the size of this piece at about 11ft long |
Next I took the horizontal stabilizer skins down from the shelf and removed the inner blue film along with a strip around the outside edges. I then deburred all the skin edges and placed the skins into the cradles I had build earlier.
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| Skins resting in their cradles |
I quickly realized that the strap cradles I had built will not hold the skins tightly enough to insert the nose ribs, so I decided to build the plywood forms as described in the plans to pull the skins together. These will easily clamp to the existing cradles.
While waiting for a scroll saw to be delivered so that I could cut the rib outlines out of the plywood forms, I decided to cleco the long and short stringers together and final drill the outermost #30 holes at each end. I also radiused the nose ribs a little more to ensure that no dents would appear in the skins when inserted.
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| Cradles built as per the plans |
After cutting the plywood to the shape of the ribs, I clamped them to the sides of the cradles and gently lowered the skins in. It was not too hard to push the skins down into the cradles, and they held the skins together well, I just had to take care to support the skins as I dropped them in.
It was now relatively easy to cleco the 8 nose ribs into the skins. I took my time to make sure the nose ribs were held in place evenly and securely. I then dropped in the front spar assembly, and clecoed the skins to the flanges. That really helped to pull the skins in.
Next I removed the plywood forms and let the skins rest in the strap cradles. This allowed me to easily install and cleco the stringers on each side by pulling the skins out slightly. I then proceeded to cleco the inspar ribs to the skins.
The stringer web was the next piece to be attached. After deburring the edges, I clecoed it into place and final drilled the 1/8" holes into the stringers and innermost inspar ribs using an angle drill.
The final piece to attach was the rear spar. I clecoed it to the inspar ribs and then to the skins. I had to spread out the clecos somewhat as I was starting to run out of the 3/32" size. I have 500 of those, but I'll be ordering some more soon as I anticipate needing more as I get into construction of the larger parts.
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| All clecoed together, view from the left side... |
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| ...and from the bottom |
Next I final drilled all holes in the skins using a #40 reamer. Even though the holes are final sized, there are areas where there is a very slight mismatch in alignment of skins to rib flanges, and the reamer helps to clean that up. As I reamed each hole, I marked the hole, so that when I went to move the clecos over it was easy to keep track of which holes were already drilled.
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| All holes final drilled on the bottom of the stabilizer... |
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| ... and on the top |
All that was left now was to disassemble all parts to prepare them for riveting and final assembly. This was a quick process, but I used the plywood cradles again when I got to removing the front spar and nose ribs. as they helped to keep the skins together as the clecos were removed.
I also went ahead and removed the blue film along the inner rivet lines of the two skins.
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| All parts ready for deburring, dimpling and countersinking |
Build Hints
- While match-drilling ribs near the ends of the front spar/spar caps, be sure to hold the spar cap tightly against the spar flange, as the spar caps are relatively unsupported in these areas and have a tendency to bend inward slightly, or cleco the ends of the spar/spar cap flangess using #40 clecos
- Strap cradles allow to move the skins as needed to install the skeleton, but plywood forms are very useful to pull the skins together while installing the nose ribs. 2 plywood forms are adequate as each skin can be worked on separately when installing the nose ribs
- Use as many clecos as possible to hold the skins to the ribs when final drilling. The rib flanges generally have only 2-3 holes per section, and if only one hole in a section is clecoed, the flange has a tendency to not perfectly align with the skin hole. For ribs at the edges of the skins, where necessary hold the flanges in line while drilling
Time Taken: 12.5 hours
Dates: September 11 - September 17 2022
Horizontal Stabilizer Total Time: 39.6 hours
RV-10 Build Total Time: 115.6 hours
Priming Total Time: 10.8 hours (not included in build time totals)