More Work on the Left Elevator   January 28th, 2007

Last week I finally got the replacement front spar, and spent some time dimpling/countersinking the holes. Today I put everything together and started riveting the elevator.

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The Dreaded Left Elevator Tabs   January 4th, 2007

While waiting for the new parts from the factory, I decided to tackle the elevator tabs. These are two overhangs on the skin that need to be bent 90 degrees to cover the triangular gap where the trim-tab meets the elevator. Supposedly this is a pretty hard task to do without cracking the skin because of the sharp bend. Some people end up replacing the entire skin, which I REALLY don’t want to do. Another option is to just cut off the tabs and build a little rib to support he skin instead.

So, I decided to try my hand at bending some scrap sheet aluminum. What better than to try and make a little rib! I installed the little rear spar on the skin to keep the right shape, and then drew the outline of the rib on a piece of scrap 2×4. Using a miter saw, I cut a wedge out of the 2×4 with the same shape, and made sure it fit inside the skin. I then transferred the outline to one of the pieces of scrap 0.020 aluminum provided with the kit (same thickness as the skin). Then I drew two parallel lines about the same distance away from the wedge as the flanges on most ribs. Finally, I cut out the shape using tin snips and put the piece on the wood block.

I re-assembled the cut 2×4 and clamped it to the end of my table surface. I then used another piece of 2×4 to bend one of the flanges down. As you can see, it looks OK but not great.

As stated in the kit instructions I then finished up the bend by whacking it with my rivet gun and flush set. I set the pressure down to about 20psi and just ran the gun back and forth over the bent flange.

The result was actually a lot better than I had expected. Here’s a picture of the little rib after doing the other side with the same technique:

So, this wasn’t so bad. Sure, time consuming but not bad. So, I decided to go ahead and bend the real thing on the elevator. I fabricated another wood wedge to fit the constrained dimensions in the elevator and proceeded to bend the flanges. Well, I didn’t crack the skins, but honestly they turned out looking like crap. First, it was a lot harder to do the actual bends because the skin and the clamps can’t be moved out of the way like with the rib above. Second, the wood form was not cut from the ‘middle’ of a 2×4 piece like the one above. Rather, I used one of the ‘edges’ of the 2×4 for one of the bends. Needless to say, the edge on the 2×4 is rounded, and it’s impossible to get a good quality bend. So, the lesson here is to ALWAYS use wood forms with nice sharp edges.

So, considering how good my rib turned out and how crappy the actual bend ended up looking, I decided to just cut it off and use my rib! I used a dremel tool to cut off most of the flange, and then used snips to finish with a clean straight cut.

Here’s what the edges look like after a bit of filing and deburring..

Finally, I test fitted the rib, both with the web on the inside or outside. I will wait until I’m ready to install the trim tab before drilling this in.

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Rear Left Elevator Spar Screwup..   January 1st, 2007

I went ahead and dimpled both sides of the front spar (used to attach the trim tab). It turns out the top half needs to be countersunk so the piano hinge can later be match drilled. I would just dimple the piano hinge too (have done it before on a training project with no problems), but match drilling it to the already-dimpled holes of the skin and spar is going to be a major pain.

It’s not very expensive, so I just ordered another one from Van’s. I had a couple more things I needed anyway, so it’ll be (somewhat) worth the handling and shipping fee….

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