Having received a replacement E-919 elevator trim tab skin from Van's (to replace the one I had accidentally creased while bending the tabs) as well as replacement trim tab spars (as the original ones had been laser cut), I proceeded to debur the edges and holes of these parts, and mask off and scuff the foam rib locations in the skin.
I eventually got around to priming the replacement trim tab skin, and could now continue with bending of the tab, hopefully learning from previous errors. I'll post separately on the techniques I used for trim tab bending, but after some experimenting, I was able to successfully bend all 8 end tabs at the exact locations specified in the plans. Each bend also had a nice 1/16" radius to ensure the skin won't crack.
 |
| Both trim tabs with end tabs bent to 90 degrees |
Next I used another homemade tool to ensure that the trailing edge of the trims tabs was evenly creased with no bulging across the trim tab. The homemade bender (described in section 5.7 of the plans and seen in the photo above behind the trim tabs) worked well to bend the tabs to their approximate final angle, but I did notice some bulging increasing toward the center of each tab that had to be taken care of.
Section 5.7 of the plans also discusses the use of a homemade trailing edge tool that can be used to finesse the trailing edge bend using additional squeezing to remove any bulging. This tool consists of two pieces of hardwood connected with 2 pieces of hinge pin.
I used channel lock pliers to gently squeeze the trailing edge where there was a bulge, and checked several times while gradually increasing squeezing force until a straight edge place across the trim tab indicated that the skin was flat under it.
 |
| Using the trailing edge tool to squeeze the trailing edges a little more and remove any bulging in the skins |
 |
| The trailing edges of both trim tabs sit flat against the workbench, and the skins are completely flat across the trim tabs |
 |
| Very happy with how the trailing edges turned out after the edge squeezing |
After clecoing the trim tab spars in place, I was able to add the 15 degree bend along the bottom skin leading edge by using a 2x2 3ft length of hardwood. Other builders have just pushed the skin edge against the workbench to achieve this bend, but I found it much easier to create the initial bend by pushing down on the hardwood.
After the initial bend was made, it was easy to run a piece of scrap wood along the bend to coax it to the final 15 degree angle where required.
 |
| Using a 3ft piece of hardwood to apply pressure along the bottom skin and create a 15 degree bend |
 |
| Small adjustments to the bend angle were easy to make using a scrap piece of wood |
 |
| Bend angles came out uniformly on both trim tabs... |
 |
| ...with barely any waviness in the skin along the length of each trim tab |
Next it was time to match drill the outer end tab holes into the inner end tabs. I decided to first insert clecoes in all the trim tab spar holes to ensure everything was held together tightly, and then match drill and cleco each hole in turn to #30.
 |
| Trim tab spars fully clecoed to the skins |
 |
| Match drilling holes in the end tabs. Care was taken to ensure the drill bit was perpendicular to the tab while drilling |
 |
| 3-D printed v-blocks were used to help support the trim tabs while drilling. Above are the inboard tab holes after match drilling... |
 |
| ... and these are the outboard tab holes after match drilling |
With all holes drilled and deburred, it was time to start dimpling the remaining holes in the trim tab horns, spar bottom flanges, and skins. I was able to reach all holes using the pneumatic squeezer except for the aft most trim tab horn rivet hole in the skins. These were easily dimpled using the close quarters dimple dies.
 |
| Trim tab horns dimpled |
 |
| Dimpling the skin to spar holes |
 |
| End tab holes were dimpled using 120 degree dies made especially to accommodate 1/8" blind rivets |
 |
| I did have to switch to using regular #30 dimple dies (and the narrow female dimple die) to dimple the aft most holes in the end tabs to avoid interference with the bend |
 |
| Using the close quarters dimple dies to dimple the aft most trim tab horn holes in the skins |
 |
| Here you can see which hole had to be dimpled using the close quarters dies. This hole was out of reach of the regular 3" yoke |
 |
| All trim tab horn holes dimpled in the skins |
The final step prior to final assembly of the trim tabs is to countersink the holes in the top flanges of the spars. This is required so that a hinge can be attached, which will then allow the trim tab to be attached to the elevator.
Since the trim tab spar flanges are relatively thin, I was able to make a doubler out of the previously received laser cut trim tab spars. I cut off the flanges of those spars, and clecoed them under the replacement trim tab spar flanges prior to countersinking. This resulted in perfect countersinks with absolutely no wallowed out holes.
 |
| Using the vise to hold the trim tab spar steady while countersinking the holes along the top flange |
 |
| From this angle you can see the doubler (made from old laser cut trim tab spars) I attached under the top trim tab flange prior to countersinking |
 |
| All holes dimpled and countersunk as required |
 |
| Trim tab spars with countersunk and dimpled holes, along with the doubler that was used for countersinking |
After a quick priming session of the trim tab spars, final assembly of the trim tabs began with riveting the trim tab horns to the bottom skins (except for rivets that were common to the spars). I was able to reach all these with the pneumatic squeezer and the 3" yoke, but had to switch to the 4" no hole yoke to reach the aft most rivet.
 |
| Trim tab horn clecoed in place |
 |
Using the 3" yoke to reach most of the rivets for the trim tab horns
|
 |
| Using the 4" no hole yoke to set the aft most trim tab horn rivet |
 |
| Rivets were set in only those trim tab horn holes that were not common to the spar, on the left trim tab... |
 |
| ...and on the right trim tab |
 |
| Shop heads all look good on the right trim tab... |
 |
| ...and on the left trim tab |
I then clecoed the trim tab spar in place, and used the longeron yoke in the pneumatic squeezer to squeeze rivets along the bottom flange of the spar. These are done somewhat blindly because you cannot actually see the rivet being squeezed. Therefore prior to squeezing each rivet, I made sure that the flat set was centered on the manufactured head and the squeezer was held at the correct angle. Luckily all rivets set well on this first try and I didn't have to redo any.
 |
| Using the longeron yoke to squeeze rivets along the trim tab spar bottom flange |
The spar rivet at the inboard end of each trim tab lies right next to the trim tab horn. This makes it hard to center the flat set on the manufactured head. I was however able to use a 3/8" diameter flat set on the manufactured side and a 1/2" diameter flat set on the shop head to set the rivet without issue.
 |
| Carefully squeezing the inboard most spar bottom flange rivet next to the trim tab horn |
 |
| You can see the inboard most spar rivet sits slightly under the trim tab horn, but it was not an issue squeezing this one as described above |
 |
| Spar shop heads all set within spec |
 |
| Squeezing rivets using the longeron yoke. It fit over the trim tab spar if I used a 1/2" long flat set on the shop head side |
 |
| Both spars fully riveted along the bottom edge, ready to move on to attaching the foam ribs |
After setting all the rivets in the spar bottom flanges, the next steps involved adding the foam ribs. I mixed up about 30g of tank sealant, applied sealant to each foam rib in turn and carefully inserted them in place within the trim tabs.
Before leaving the sealant to cure, I set blind rivets in the end tabs, and used my 3-D printed v-blocks to hold the trim tabs flat and secure to ensure there would be no twist. The trim tabs were then left for a few days to cure.
 |
| Sealant applied in a thin layer along all edges of the foam ribs |
 |
| Blind rivets set in the end tabs after the top skin was clecoed to the spar |
 |
| V-blocks and wood to keep the trim tab flat and secure while the sealant cured |
Primer used: ~30g + 3g distilled water
Time Taken: 11.3 hours
Dates: January 21 2023, October 26 2023, November 5 2024 - November 12 2024
Elevators Total Time: 103.6 hours
RV-10 Build Total Time: 861.5 hours
Priming Total Time: 104.2 hours (not included in build time totals)
