08/13/2018 Horizontal Stabilizer – Going Backwards and Learning From Mistakes

I haven’t made much progress in the past 10 days again due to flight instruction and family duties. When I did get a chance to work on my horizontal stabilizer, I made mistakes 🙁

Let’s talked about tonight first. Today I was about to start riveting the reinforcement bars and back spar together, and I noticed a few small spots are missing a little primer when I laid out the bars and spar. So I sprayed a little primer and set the wet parts aside. At the mean time I decided to tape over a few holes on the dry reinforcement bar and spar that I didn’t apply primer today, which went smoothly(I guess it’s pretty hard to screw up taping a few holes). About half an hour later, I only had one reinforcement bar that’s not completely dried, and I had everything else on my workbench. I decided to change the yoke on my pneumatic squeezer while waiting at the workbench. Big mistake! As I removed the bolts from the squeezer, I lost hold of the yoke. The yoke fell right on to my left back spar, creating a dent on the flange and leaving a few more scratches nearby.Stupid me! I should have never prepared tools right over precious airplane parts! Well, that set me back for another night as I had to get my precision files out to smooth out the dent, and I even took it to the bench grinder for a few passes. Then I need to re-apply primers and wait for it to be completely dried.

Now, why did I waited almost ten days to start riveting? Well, that’s because I made mistakes when priming the horizontal skins last Thursday before a family road trip over the weekend. Sanding the inside of the skin was no problem for me after spending those ridiculous 7 hours sanding the skeleton parts earlier, I started to figure out the sanding process and it didn’t take that long when I worked on the skins. It’s the priming part that I messed up. When I was priming the skeleton parts, I sometimes apply too much primers to some areas. As a good observer and learner, of course I decided to fix the issue. When priming the skins, I intentional left a much much bigger distance between the rattle can nozzle and the surface when I sprayed the primer, hoping that the powder like droplets falling onto the surface will create a nice thin layer. I could not be more wrong! With the hot temperature around 90s, the droplets completed dried off even before they hit the surface, so as a result there’s not much of a primed layer at all on the horizontal skins. The dried primer droplets look more like cat litter than anything else. As much as I hate the toxic chemical products, I had to spray mineral spririt to wipe off most of the primer droplets and re-apply the primer again. Because the first time I screwed up so badly, after reapplying primer I had another round of sanding and applied another round of primer to make the primed skin look reasonably smooth.

I really wish to complete my horizontal stabilizer this week since I’ve been “stuck” with this supposedly simple first project for almost a long three months now. But with flight lessons and my own proficiency flights planned from Wednesday all the way through Sunday, I had to change my goal to maybe at least get the skeleton riveted together by this weekend. It’s ironic that in the past years I would be thrilled to be able to fly everyday, now I get excited whenever a student has to cancel with me for whatever reason, because I get to work on my airplane.