Horizontal Stabilizer 8-10-1 to 8-13-1
I started riveting the horizontal stabilizer skeleton together, specifically the inboard in-spar ribs to the stringer web, followed by the stringers to the stringer web and to each other.
I was able to get all the rivets squeezed using the flange nose yoke, but decided to switch to using the Cleaveland Main Squeeze for more control over squeezing some of the rivets in the corners of the stringer web. The rest of the 1/8" rivets were squeezed using the pneumatic squeezer.
I don't think I would have been able to squeeze the rivets without the flange nose yoke, but it was still awkward maneuvering the yoke over the stringers, as I had to open the set holder as much as possible to get it to fit over. I then had to adjust the set spacing while the squeezer was held over the stringers.
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| Stringer web riveted in place |
I had a small issue squeezing one of the rivets into the stringers and stringer web. As I was starting to manually squeeze the rivet, the rivet slipped out so that the shank was flush against the stringer web and the rivet head was raised above the stringers.
I didn't notice this until the rivet was partially set, and the only way to drill it out was to drill through the rivet shank. I took it slow, but was able to drill the shank using a #40 drill while making sure the drill was held parallel to the shank. Once I had drilled down sufficiently to clear the stringers, the rivet was easily hammered out using a 3/32" pin punch with no damage to the holes.
After drilling out this rivet I was particularly careful to ensure that subsequent rivets were correctly positioned as I squeezed them.
Next I riveted most of the other inspar ribs (all except the most outboard 2 on each side) to the front spar. The pneumatic squeezer with flange nose yoke handled all of these easily.
I then moved on to attaching the nose ribs to the stabilizer skins. I reattached the cradles along with the plywood forms to the workbench and started with the left stabilizer skin. After clecoing the nose ribs into place, I started working on a strategy to rivet the inner nose ribs to the skin and decided to start with the aft most hole going forward.
Then next hole (2nd most forward) presented a problem. Here the rib flange did not sit flush against the skin. Even using the rubber washer to hold it tight, I was not able to get a good set on the rivet. After having drilled out several improperly set rivet attempts, and a lot of head scratching, I was finally able to determine the cause of the issues I was having.
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| The heart of the horizontal stabilizer |
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| Shop heads all squeezed to spec. I kept a label on the stringer web to help with orientation |
Next I riveted most of the other inspar ribs (all except the most outboard 2 on each side) to the front spar. The pneumatic squeezer with flange nose yoke handled all of these easily.
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| Inspar ribs attached to front spar |
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| 2 different length rivets used to attach inspar ribs to front spar |
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| Horizontal stabilizer skeleton taking shape |
I then moved on to attaching the nose ribs to the stabilizer skins. I reattached the cradles along with the plywood forms to the workbench and started with the left stabilizer skin. After clecoing the nose ribs into place, I started working on a strategy to rivet the inner nose ribs to the skin and decided to start with the aft most hole going forward.
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| Ready to start riveting the nose ribs into position |
I noticed when I removed the aft most cleco that the skin pulled away from the rib flange as there was nothing to hold the skin tight above the rib. I decided to use a spare inspar rib I had laying around to keep the skin tight by clecoing it in just above the nose rib. This worked well and I was able to set the aft most rivet easily.
I then proceeded forward along the nose rib (alternately on each side) and was able to set the next 2 rivets without any issues (although I used the rubber washer trick on the third hole forward to keep the rib flange tight agains the skin).
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| Spare inspar rib used to hold skin tight above nose rib |
Then next hole (2nd most forward) presented a problem. Here the rib flange did not sit flush against the skin. Even using the rubber washer to hold it tight, I was not able to get a good set on the rivet. After having drilled out several improperly set rivet attempts, and a lot of head scratching, I was finally able to determine the cause of the issues I was having.
The main issue was that even though the rubber washer was holding the rib flange against the skin at the start of riveting, only the forward edge of the flange was touching the skin. The aft flange edge (where the rib web curves over into the flange) was still pulled away from the skin. This resulted in the rivet partially setting behind the flange and not forming a good shop head over the dimple.
After more head scratching on how to tackle this, I determined that I had to push the skin tight against the flange from the outside. I didn't have a helper available, so my solution was to take a 4" ratchet clamp and use it to hold the skin tight. I used duct tape to hold the clamp in place on the skin as it had a tendency to slowly slide off, but I was able to gradually increase clamping pressure until the skin was visibly tight (from the inside) against the rib flanges on both sides of the skin.
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| Ratchet clamp holding the skin tight to the nose rib |
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| Clamps are amazing helpers to hold skins tight! |
Once the clamp was in place I was easily able to set these rivets along with the forward most rivets (although space was tight).
Prior to tackling the second inner rib in the same manner (although this time starting by riveting the 2nd most forward rivet first), I used the pneumatic squeezer to rivet in the outer nose ribs. These were easy to do, I just had to pay attention to keeping the squeezer tight against the skin during riveting.
The clamp technique, and starting with the 4th rivet down, worked well for the remainder of the inner nose ribs. I only had one issue where a rivet cracked, and after I drilled it out the tab on the nose rib bent inwards slightly. I had to drill out the rest of the rivets in that nose rib so that I could remove it and bend the tab back out. I then had no issues riveting the rib back in.
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| Inner nose ribs riveted in place... |
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| ...another inner nose rib |
With the nose ribs installed I was able to insert the front spar assembly and cleco it into place.
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| Horizontal stabilizer taking shape |
Next I riveted the front spar to the nose ribs using LP4-3 blind rivets for the inner nose ribs and AN470 4-4 rivets for the outer ribs at the far ends. The outer ribs near the center of the stabilizer will be riveted later when I remove the stabilizer from the cradles. This went well, even in the confined space between the skins. I used a manual rivet puller for the blind rivets, and the pneumatic squeezer for the universal head rivets.
I then clecoed the remaining 2 outer ribs in place on each side of the stabilizer, and riveted those in with a combination of blind and universal head rivets. The only difference here was that I used the Main Squeeze manual squeezer to rivet the outer ribs due to the limited space available.
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| Blind rivets used inside the stabilizer |
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| Outer ribs riveted with universal head rivets |
I am now ready to rivet the skins to the skeleton, but that will be for another day... days... weeks maybe?!
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| Clecos will slowly disappear as the skin is riveted |
Build Hints
- Rivets around the stringers are best squeezed using a flange nose yoke. The other option is to buck them.
- 1/8" rivets can be drilled out from the shank if needed as long as the shank does not exit the hole. Use a #40 drill bit and keep as centered and parallel to the shank as possible. Once drilled past the sheet metal use a 3/32" pin punch to push out the rivet.
- Put blue painters tape over the rivet set to avoid scuffing the skin while riveting. When the tape starts to break up, just replace it.
- Ensure that skins are tight against all parts of the flanges prior to riveting. If the flanges were correctly bent to 90 degrees from the web when parts were prepared, this will eliminate the need for any rubber washer tricks to hold the flanges tight.
Time Taken: 10.8 hours
Dates: September 29 - October 5 2022
Horizontal Stabilizer Total Time: 63.1 hours
RV-10 Build Total Time: 139.1 hours
Priming Total Time: 15.8 hours (not included in build time totals)