Dave’s RV-7A Building Log

I drilled the second bellcrank-to-aileron push tube. This one seemed much easier than the first. Two tips here. First, drill just a tiny bit until there’s a small divot. Check to make sure the drill bit hasn’t walked on the slippery surface. If it has, adjust the tube so that the drill will go straight through. The second tip is to make sure the threaded rod end doesn’t creep out. For some reason, it seems to want to pop out just as the drill bit is going through. Hold it in place.

Both push rods are now ready for primer and then riveting. Since only the outside is powder coated, I’m going to shoot some rattle can GBP-988 in there.

I pulled down the super long aluminum tube very carefully and cut it for the stick-to-bellcrank push tubes. I cut it at 66″ with a hack saw and then used the stationary disk sander and Scotch-brite wheel to trim it down to the 65-25/32″ called out on the plans. I wrapped a piece of tape around the tube and measured the circumference as 3.55″. After dividing by 6, I marked the tape every .59 inches. I never thought I’d use the side of the ruler with the 1/100″ marks, but it came in handy for this.

I was showing a neighbor the project, showing him the pre-punched parts. He said, “So you just put it together.” Yeah, after final drilling, deburring, dimpling, countersinking, priming, etc. I’m finally to the point where I “just” put things together.

I riveted the flap reinforcement parts to the front spar and end rib. I also riveted the psuedo rear spar to the ribs. This step isn’t mentioned in the instructions, but it’s obvious these will be impossible to set after the skins are on. I then clecoed on the skins and got everything ready for some riveting. It’s really narrow inside the flap. I might have to get creative with the bucking bar.

Started riveting on the aileron brackets. I was trying to use the squeezer, but it involved changing the sets and yokes around and really wasn’t worth it for the few rivets that it could reach. I got out the rivet gun and had very good luck doing some solo riveting… until the last rivet. I had to use the offset rivet set for that one and the shop head cleated over. Not sure why. But overall the rivet gun (especially the 3X gun) works really well. I shouldn’t be so afraid of it.

Also primed all of the flap parts.

I took Julie flying and yesterday helped my friend Steve move his boat from Anacortes to Everett, so I didn’t do much on the project this weekend. I basically just primed some wing and flap parts. For the wings, I primed the aileron gap seals and flap braces. I also touched up the primer on the aileron brackets where I had to do some smoothing on the Scotch-brite wheel to get the brackets to fit to the rear spar nicely.

I bought a “Center-It” jig a while back, so I pulled that out for drilling the bellcrank-to-aileron push tubes (the smaller ones). The dimensions aren’t called out on the drawing. It’s a full-scale drawing, so I just measured off the drawing. I drilled both ends of one of the rods. It turned out pretty good. The drill had a tendency to walk a bit on the powdered coated smooth, round surface. I’ll probably try using a punch on the other rod to get the holes placed more accurately.

I know some people weld the ends on these rods. It seems like a weak point to have two rivets holding it together. I can always order replacement rod stock and ends if I decide to get these welded. For now, I’ll use what hundreds of other RV’s are flying with.

I bought a drill extension from Sears that fit perfectly with the countersinker. That enabled me to better countersink the holes on the aileron brackets. The brackets are ready for some touch-up primer and then I’ll attach them to the wings.

I then moved on to the aileron push rods, getting out all of the parts and figuring out how they go together. I cut the rod stock into two pieces with a hack saw (not going to ruin another band saw blade on steel) and cleaned up the ends with the grinding wheel and Scotchbrite wheel. I bought a centering jig for drilling round stock a while back. I got that out and started to figure out how to use that to drill the rivet holes in the ends of the rods.

The weather has not been cooperating lately for some outdoor priming. It’s been very windy, rainy, and cold. I have a bunch of stuff waiting to be primed. This weekend it’s supposed to improve. I guess I’ll have to eventually set up the indoor priming booth again. Bummer.

I thought about the flap brace some more. Reading through the RV-7 Yahoo archives, the best approach is to dimple the bottom skin, countersink the flap brace, and just drill the flap hinge. This is the sequence I’ll try:
1. Prime the flap brace and rivet it to the rear spar. Also install the aileron gap seal and brackets.
2. Install the aileron.
3. Cleco on the bottom skins.
4. Align the flap with the aileron and drill the bottom skin to the flap brace to the flap hinge.
5. Remove the bottom skins, dimple the holes along the trailing edge that connect to the flap brace.
6. Countersink the flap brace (with the bottom skins off, this will be easy).
7. Rivet on the bottom skins including the skin to flap brace to flap hinge.

Now that I’ve thought about it for a minute, it seems easy. Getting the sequence right is half the battle.

While searching the archives, I answered two other questions. There are two methods of handling the flap hinge pin. Cutting it into two parts and securing it in the middle seems to be the most popular option. The other question I had was about the flap hinge material that hangs off a little on the wing side. Dan just cut off the extra.

I noticed on Dan’s site (3rd picture down on this page) a reference to some easy-to-miss flush rivets connecting the aileron bracket to wing rear spar. Sure enough, I didn’t countersink those holes. I messed around trying to countersink them, but it’s very difficult to get the countersink straight in there with the brackets assembled, even with the cage removed. I’ll need to find an extension or right-angle drill to do it correctly. I want to take care of it before I touch-up the primer on the brackets this weekend.

I also messed around with the flap braces. I never drilled them to the bottom skins, so I hauled out one bottom skin and clecoed things together. I need to think a bit about the best sequence here. I need to match drill the flap brace to bottom skin, match drill to the flap hinge (after aligning with the aileron), and then I think countersink the flap brace. Ideally, I would rivet on the flap brace somewhere in there. I noticed at least one other builder had to countersink the flap hinge. I’d rather countersink the flap brace, so I’m trying to figure out how to do that. I’ve looked in the instructions and plans, and don’t see any help for this area.

Deburred the rest of the flap skins, dimpled the holes around the edges with the squeezer and did the rest with the C-frame. Unless I’ve forgotten something, the flap parts should be ready for priming and assembly.