Project: Mike     -     Entry

Mar 21, 2023 4 Simple task takes hours..... Category: Empennage
Never ceases to amaze me that sometimes, the easiest of tasks, ends up taking hours. This is how you end up with those dents in your forehead as you repeatedly bang your head against the wall in a vain attempt to right what is wrong.

Anyways..... All I needed to so was to attach and match drill one half of the hinge section so that the new trim tab would sit perfectly aligned with the rest of the elevator. Easy enough right...? Wrong!

For starters, I didn't pay attention to the direction of the new section of hinge was getting attached to the underside of of the elevator. I had the two half sections of hinge, that attach to one another, 180 degrees out from what they should have been. IOW when you set the two parts of the hinge down on a flat surface, the two flat parts should both be on the same side as one another laying flat on the surface. I fiddled around with this hinge section attached backwards for about an hour before I realized my mistake.

So take two or three or four....... Anyways I fiddled and fiddled around with the hinge (once I had it oriented correctly) trying to get the trailing edge of the trim tab to align with the trailing edge of the elevator as the plans have you do. The issue I ran into was that if I made the two trailing edges perfect with one another, there wasn't enough material on the upper hinge section to drill an attach hole and still have proper edge distance. IOW I was having to push the upper hinge section too far away from the edge of the elevator cutout to get a good alignment but also have enough distance to drill and ultimately rivet a hole.

As always having a line drawn down the middle of the hinge attach point was helpful here as it allowed me to see just how far off it would need to be to be perfectly in line with the elevator's trailing edge. So in the end, I had to compromise a little bit to get enough material to drill into in the hinge. That's why this took forever. Once I finally settled on the alignment of the upper hinge to to the elevator to get the trim tab to sit where it needs to sit, I was then able to match drill the attach holes for the upper section of the trim tab hinge.

Again, hours of frustration which fortunately was interrupted by a visit from a friend and fellow RV builder (RV14) who stopped by to look at my project and talk shop. Dan lives about 10 minutes away and is just getting started on an RV-14A build so will be a valuable resource to have close by.

So I was finally able to hang the trim tab to the elevator temporarily to at least see a somewhat finished piece! Now it was time to disassemble everything and prime the parts. So took some time to do that and prime the internal parts. I am not going to prime the interior of the trim tab this time around.

With those parts primed and readied, I riveted the two control horns to the lower side of the trim tab. Despite all of my planning and dimpling ahead of time, I still could not reach that aft most hole to get a rivet in there. I finally gave up and went with another MK319BS rivet for that spot which I'm fine with.

I also primed the little section of skin on the bottom of the trim tab on which the control horns sit. Good place for water to collect so better to be safe than sorry.

With all of that done it was a good place to stop for the day. I noticed now that the blue vinyl is off the trim tab, it has a pretty good bulge in the center of one side of the skin. It's really noticeable if you put a straight edge down the lateral axis of the trim tab.

So new task next time out, build the straightening tool from section 5 of Van's plans to help remove this bulge. I need to do this anyways because the trailing (folded) edges of the elevators need a bit of tweaking before I'm done. So I will build one of those squeezing tools and see if I can get the trim tab a little bit better shaped before I start the final riveting. Not sure I can get rid of all of it. Again there's no internal structure to the trim tab for support so I will do the best I can without ruining it and then live with it.

Also this time around I think I can get a squeezer in to the side of the tab that gets riveted to the lower half of the trim tab spar. Riveting that by hand with a bucking bar (blindly) last time around wasn't fun. Hoping to avoid that this time around.


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