It was again time to roll some aluminum. Rolling the leading edge of the right elevator actually ended up being more frustrating than the rudder. It took multiple attempts with a lot of force to complete the initial roll, and after massaging the roll by hand I still couldn't get very good results like the rudder.
My problem was that I used a different diameter pipe for each side of the skin, causing one side to have a larger radius than the other and causing the completed roll to appear lopsided. I did what I could to unroll and flatten each side so I could retry. After much trial and error (and a lot of cursing) I was finally able to get acceptable results.
I'm really glad I'll only have to do this one more time in the entire build. The ailerons and flaps both have a riveted-on piece for the leading edge instead of having you roll the two sides of the skins together, so I'll only have to roll the leading edge of the left elevator.
I propped up the (mostly) completed assembly on some wood blocks. I haven't decided whether I want to try mounting these on the wall above the vertical stabilizer or if I want to just build a ground stand for the elevators instead like the rudder. I'm leaning toward the stand so I don't run the risk of one of these things falling. The last thing I need is to have to spend another fifty hours rebuilding an elevator.
I put away the right elevator on its temporary stand and brought out the left elevator skin. Before it can be riveted to the skeleton I'll need to do something about the tabs in the cutout for the trim tab. They'll need to be folded over one another, drilled, and riveted to close out the opening in this part of the skin.
The plans' method for accomplishing this is to make some wood bending blocks in the shape of the opening. These blocks get clamped in place and end tab gets bent - first by hand, then the final crease is made with the flush set on the rivet gun. I cut out the blocks and sanded them until they were as close to the shape of the cutout as I could.
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| Pretty close. Let's see how this goes... |
I clamped down the whole assembly as tightly as I thought I could without blocking the tabs or damaging the skin.
I then went to work with another block of wood, slowly starting to bend down the bottom tab. Everything was looking good thus far.
I had a couple times where the inside block began to shift inward, but the plans did mention this happening so I simply readjusted the block back to its proper position and continued on.
Once I had the initial bend to about 45 degrees I brought out the rivet gun and set it to low pressure. What I didn't count on was the fact that the gun puts out quite a bit of kickback even with the pressure on low. The crease started okay at first as I went slowly up and down to the tab, but one slightly larger feather simultaneously forced the interior block further into the skin and put a nice dent into the crease.
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| :( |
After the initial storm of cursing had died down, I went back in for a closer look and realized that the inside block had obviously shifted inward while I used the rivet gun. The bend line was almost an eighth of an inch away from where it needed to be, way closer to the relief cutout near the trim spar than was probably safe.
Looking back at the instructions I realized that I had conveniently missed the part where double-sided tape should be placed on the blocks to keep them from moving. Feeling like an idiot I called it a night.
After some meditation and research I gave myself an ultimatum: I'll use the hand seamer to bend the tab flat and try the wooden block method again, with the appropriate tape this time. If that doesn't work then I'll do what some other builders have done - cut off the tabs and install a riblet to close out the skin. I happened to still have the ribs from my unfinished practice kit, and out of curiosity I placed a bending block into one and it fit almost perfectly. Instead of fabricating riblets from scratch I may be able to trim this rib to fit into the space the tabs would have covered.
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| Like Cinderella - a perfect fit! |
