Elevators 9-16-4 to 9-16-5, 9-17-5
Prior to using tank sealant to attach the elevator foam ribs and trailing edges, I decided to work on the trim tabs so that foam ribs could also be sealed in those at the same time.
Since all the holes in the trim tabs, spars and horns are already final drilled, I decided to skip ahead a few steps and debur the holes now, since I would not need to touch them again until riveting. The only holes I did not debur, and will do so later, are the holes on the close out tabs as these will need to be match-drilled. Deburring the skin holes, especially the inside, is significantly easier prior to finishing the skin bend.
I then used my homemade bending brake (constructed a month ago) to bend the skins as close as I could to their final positions. I applied the bend gradually, and frequently checked by holding the spar in place to see how much further I needed to bend, being very careful not to overbend.
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| Trim tabs bent to their final positions |
Bending the skins using the brake worked very well. I ensured the tab was held in place by hand in the brake while applying the bending force, and also that the tab was far enough into the brake so that the surfaces of the brake would contact the tab evenly and not pinch the trailing edge, and the resulting bend was even along the length of each trim tab with no pillowing when the spar was clecoed in place.
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| No unintended pillowing or compression along the length of each trim tab |
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| Trim tabs are also straight spanwise |
Next I moved on to bending the close out tabs on the trim tabs. I followed the directions in the plans and clamped two wedges in place. The edges of the inner wedge were radiused a small amount and the wedge was positioned 1/32" back from the skin edge as described in the plans.
I proceeded to bend the bottom skin tab (on the left trim tab) and it went well, using a wood block to start the bend and the rivet gun on low pressure with a peening tool to complete the bend. I did notice the bend was quite sharp compared to the bend I put in the elevator skin tabs (1/16" radius), but seemed in line with bends I had seen on other builder logs.
I then bent the top skin tab and here I ran into problems. The initial bend with the wood block went well, but using the rivet gun I noticed distortion starting to appear on the tab close to the bend. I also noticed that the wedge had moved back little near the leading edge of the trim tab while bending. I was not happy with this!
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| Skin distortion close to the bend. Not sure if it is due to stress, or the wedge moving slightly inward as I was bending |
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| Wedge moved inward a little at the leading edge of the trim tab causing the bend to be pushed inward slightly |
Two lessons learned from this effort
- The radius I put on the inner wedge edges should probably have been slightly larger than it was for a gentler curve
- I had read about issues other builders faced with the wedges slipping as the bend was being formed, but even with secure clamping, and bracing the back of the bottom wedge with an additional MDF 1/4" panel, I still experienced some movement.
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| Wedge used between the skins with a slight radius along the edges, which in hindsight should be a little bigger |
I will be reordering a left trim tab from Van's and redoing this tab, but now that I have a trim tab to practice on I spent some time figuring out how to make a better trim tab bend. To accomplish this, I have created a wedge that only requires clamping and bending one skin side at a time. This wedge can be clamped down securely at multiple locations to prevent movement.
I tested it by bending the angled tabs on my now practice trim tab and it worked well. I will share more details in a future post when I redo the left trim tab, but I feel confident that my next attempt will work out much better.
Build Hints
- Ensure that after bending the trim tabs to their final angle, the skins are completely straight from leading edge to trailing edge as well as spanwise. Bulges or compressions should be rectified using the techniques described in Section 5 of the Van's manual.
- The build plans specify a recommended way to perform certain steps. This may not necessarily be the best way though. Research other builder blogs/vlogs to see alternate options, especially when other builders have faced similar issues while following the plans as described.
Time Taken: 1.7 hours
Dates: December 27 - December 28 2022
Elevators Total Time: 79.6 hours
RV-10 Build Total Time: 243.3 hours
Priming Total Time: 26.4 hours (not included in build time totals)