The temperature today got up almost to 70, so I just had to take advantage of the weather to get in a bit of work in the garage. Basically, I had two things on my short list: start riveting the elevator, and prep/prime the trim motor mount angles that I drilled last time out.
First things first: the riblet I fabricated, as well as the inboard portion of the trim cutout spar, have limited access and thus will need to be attached with MK-319BS blind rivets. These require a slightly larger hole than #40, so I decided to start by drilling those out to size. This way I could get any nasty metal shavings out of my elevator before closing it up. I went and grabbed my drawer of MK-319BS rivets, and noticed…well, there aren’t very many in there at all. Ten, to be exact, and I need…let’s see…eighteen. Hrm. Looks like it’s time for another Aircraft Spruce order…I’ll have to wait on those before I can put the elevator together. (I could probably work around some of the holes while I wait, but it seems better to just hold off on the whole thing)
OK, next order of business, the trim motor mounts. Gave them a good deburring, dimpled for the flush rivets, gave them a good scrubbing, blew the air off, hung them on the front of the heater to fast-dry. (sort of ironic that even on a warm day like this, I found a reason to run the heater) I went inside to scarf down some dinner and sit with Josie for a bit, and once I went back out, the pieces were nice and dry. Normally I prime in the driveway, but in this case, since I had just a couple little pieces, I opened the garage door and set up just inside the overhang. Shooting primer on those pieces was quite easy.
In between primer coats, I riveted the hinge reinforcements and nutplates to the spar. While doing this, I noticed a spot that I didn’t quite cover perfectly with primer, so since I had the primer out anyway, I gave it a little touch-up after finishing the riveting. Then I moved on to riveting the E-703 and -704 tip ribs together. The next steps called for riveting the E-705 root rib and other items to the spar…but since I’d shot some extra primer on that, those steps would have to wait.
Well then, I’ll start looking at the trim tab itself. It starts out easy enough; there are two pieces that make up the control horn for the tab. The tab spar is clecoed in place, the two horn pieces are clamped together, and then they get drilled to the tab itself. Only some of the holes for the horn assembly are drilled, so the rest have to be drilled from scratch using the horn pieces as a drill guide. No sweat there, though the instructions were kind of badly written here. For whatever reason, they only tell you to drill one of the horn pieces, even though both need to be drilled. I read all the way through the tab instructions and saw nowhere that it specified drilling the other (ie if there was a particular reason to wait), so I assumed it was an oversight and went ahead and drilled both pieces.
Next step is to take care of the top half of the spar-tab interface. Now things get interesting; in addition to the spar and skin, the hinge on which the tab pivots has to be attached. The spar and skin are both prepunched, but the hinge is not. So the spar and skin need to be aligned very precisely so the holes will match up; normally this is what clecos are great for, but they can’t be used here because the (hole-free) hinge has to be clamped and drilled in assembly as well. So basically I have to figure out how to align three pieces at once and clamp them in place. This seemed like the kind of operation I might want to do some research on before proceeding, so I decided to call it a night. At least it leaves me with something else to play with while I wait on my shipment of rivets.
The lovely trim tab assembly: