It been a while since my last post and my progress has been fairly slow due to a misstep in bending the left elevator tabs. The tabs in question were not photographed before they were originally bent so there won't be any before and after. Shucks. The tabs in question, close off the end of the trim tab cut-out on the elevator.
According to the build manual, one simply bends the lower tab up and the upper tab down over the lower and shazzam! An instant mini-rib. Well this is, no doubt, the least expensive way to go. It is also a sure fire way to induct new members into the club of tab bending goofer uppers. Fortunately, membership does have its privileges. For example, I now know what not to do next time.
To join this fine, and apparently quite popular club, one begins by following the instructions to build a tapered bending block. I used some plywood shown below. The double sided tape is suggested to prevent the blocks from sliding during the bend process.
Then, the blocks are arranged inside and on top of the elevator skin such that the tabs can be bent over the edge of the block, 90 degrees. In the picture below, the tabs have already been bent over so the lower block is only just visible inside the elevator.
To bend the tabs one is instructed to strike the tab with a hammer using a small block of wood to spread out the force across the length of the tab. This is where things go south, because the force of the hammer blows cause the bending block to move inward an undetermined amount. This causes the finished tab to be located too far in. The undetermined part is especially troublesome as the bending of the opposite tab will most likely be a completely different undetermined value. The bottom line is that in my case, because of this issue, the tabs were not perpendicular to the surface of the elevator skin.
At this point, I had no choice but to unbend the tabs and apply for membership in the aforementioned club. Unfortunately, this horror story doesn't end here because unbending the tabs, I knew, would distort the skin. And the tabs can not be rebent in the same place anyway without significant risk of stress fatigue in the aluminum and in the builder.
Still, the tabs had to go, so the new plan was to unbend it, but then cut those SOBs right off! I have read online many accounts of intrepid builders doing just this; and so I did.
Good so far, but what about the distortion caused by the unbending? No problem, I'll just hammer it out flat using the mushroom set on the rivet gun. Genius! So, the skin does get flattened, but now there is a little too much of it as the skin has been stretched out by the jackass with the pneumatic hammer.
Now there is a definite bow to the skin along the edge and the corner is pretty ugly as well. But, I'm not about to let this elevator die on the table, so I begin to think about what can be done to correct the stretched out skin.
I was vaguely aware that it is possible to shrink metals using heat, some hammering, and a rapid quenching process. After a quick consultation with the oracle that is the internet, I'm pointing a propane torch at my elevator.
Since I had one hand on the torch and the other holding an infrared thermometer, there aren't any pictures of the shrinking process. Suffice it to say that what is said about making sausage may also apply to airplanes. Consider yourself lucky you didn't have to see it. After the quenching process, the skin lays mostly flat and I'm thinking... I can't believe that actually worked!
The next step then, is to fabricate rib to close the elevator in place of the amputated tabs.
After final adjustment and then counter sinking, the new rib was ready for installation.
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