Dave’s RV-7A Building Log

I made some new rudder stops. I started with the aft outside edge about 3/16″ further out than called for in the plans. I ended up sanding that down to about 1/8″ over a few iterations. The rudder now stops 1-1/8″ from the elevators in the neutral position. I considered making some Delrin stops as outlined on Jeff’s site here and here, but ultimately decided that just using the aluminum stops is easier.

With that complete, it was time to remove all of the empennage parts so Julie can get her car back in the garage. I deburred everything as I removed the parts and cleaned up quite a bit.

I didn’t do too much today. I tinkered with the rudder a little bit. It looks like I’ll end up making new rudder stops. Rather than start that, I read over the instructions for the cabin frame. I pulled out the raw stock I’ll need and started to cut a few parts.

Julie and Adele went to Portland for the weekend, so I spent some “quality” time with the plane. I made the bushings for the push tube. I made sure they fit and then removed the push tube. I tried torquing down the jam nuts on the push tube bearings. I think they are AN6 nuts, which means quite a bit of torque (160 in-lbs min). I wasn’t able to hold the tube and apply that torque. I just tightened them down as best I could for now.

The next task was to attach the vertical stabilizer. I marked a line where the top of the longerons should be, centered up the VS, and clamped it down. After numerous measurements to make sure it was square with the horizontal stabilizer, I drilled the two holes into the up stop and temporarily installed bolts.

I next drilled the attach plate that holds the VS front spar to the HS. It took some weird maneuvering with the right angle attachment, but I finally got it drilled. I didn’t need a shim to keep the hinges lined up, but I did put the VS spar behind the attach plate.

Last step was to drill the bottom of the VS rear spar from the holes in the tie down I installed quite a while back. Getting at those holes was very tricky. I could drill the top two with a right angle attachment, but could only barely start the bottom two holes. I ended up taking the VS back off, drilling the holes to #30, reassembling, and then final drilling to #12.

In order to make enough room for the rudder, I lowered the tail quite a bit. Looks like a tail dragger like this.

From there I attached the rudder and adjusted the bearings. The counterweight was hitting the VS a tiny bit, so I backed out the top bearing slightly and cranked down the bottom bearing. The middle bearing needed a little tweaking as well. I fabricated the rudder stops exactly according to the plans, but I do not have very good clearance between the elevators and the rudder. It started at about 1/8″ on the right side. I cranked down the bottom bearing quite a bit and was able to squeeze out 1/2″ of clearance. The instructions say it should be 1-1/8″. I searched the archives and it seems that some people have no problem with the stops and others do. Strange. Not sure what to do about it yet.

Other than the minor problem with the rudder stops, it was a very productive day. The empennage is bascially fitted at this point. I can safely say that I’ve removed and installed each empennage part at least a half dozen times, and some parts (like the elevators and rudder) are up in the 20-30 range. Yikes!

Started off my countersinking the two holes in the VS and installed flush rivets. It’s the top left and top right rivets in this picture, which is the VS upside down.

Adele helped hold the push tube while I drilled holes in it.

I installed the pop rivets, and the tube was done. Nothing to it.

I installed the elevators on the horizontal stabilizer and attached the push tube. With the elevators clamped in the neutral position, I adjusted the push tube length very slightly (I think it was maybe 1.5 turns) until the bottom bolt of the bellcrank was centered in the access hole. I unclamped the elevators and admired the smooth action of the whole assembly for a while.

You can see the attachment of the push tube to the elevator horns in the second picture. I hadn’t made the bushings yet at this point. I installed the up elevator stop. Interestingly, the elevators horns just touch the F-712 bulkhead before the stop. I’ll have to grind them down just a tiny bit.

Adele had a soccer game (scoring her second goal of the season!!), so I just primed a few empennage attachment parts including the outside of the main elevator push tube.

I started prepping the push tube ends and some other parts for priming, but the weather was not cooperating. We had some some very cool thunderstorms–unusual for Seattle.

Instead I finished drilling the horizontal stabilizer to the fuselage. I re-measured that everything was square (for at least the fifth time) and drilled away. Nothing to it.

I pulled out the vertical stabilizer and started getting it ready for assembly to the fuselage. I trimmed off the required 5/8″ from the front spar with a Dremel cut off wheel and cleaned it up with a Vixen file. I also noticed that there are two rivets on the bottom-most hinge that need to be installed. It would have been much easier to install those when I made the VS, but I guess I was still contemplating a tail dragger at the time. In that case, those two rivets would have been bolts that held on the tail wheel weldment. I drilled out the holes to #30, and quit for the night.

Reading ahead, I noticed the push tube from the elevators to the mid-fuselage bellcrank will be needed soon. Since it will take a few days to prime and assemble, I started working on it by cutting the raw tube material to length. On the last push tubes, I tried the rattle can primer for the inside and it didn’t work very well. This time I washed and etched the inside of the tube as best I could and poured in the AFS epoxy primer. That worked much better.

While that was drying, I made sure the HS is ready for drilling the rear spar. The only thing of concern is that the instructions say the tooling holes in the inside HS ribs should be the same distance above the aft deck. While this is nearly impossible to measure accurately, it seems that the front rib is different than the aft rib. I double checked all of the HS to fuse attachments against the plans, and it all seems correct. I’m not going to worry about the tooling holes.

After more careful measurement confirming the HS was properly centered, I drilled the front HS spar to the fuselage. It’s difficult to drill straight through 3 layers of 1/8″ aluminum using an angle drill attachment in a tight space, but I think I did pretty well. The holes are almost exactly centered in the angles underlying the aft deck. It took quite a bit of time to drill the holes to #40, #30, #19, and finally #12, all the while keeping things clamped together. I put some bolts in to hold things together temporarily. The pictures show the top and bottom views.

The next step was to drill the holes in the elevators horns for the push rod. In order to make it easier to center the elevators, I moved the whole assembly to a couple of saw horses with a board on top. That way the counterbalance arms could hang over the ends. I got everything aligned perfectly and determined that the right elevator horn was further aft. According to the instructions, the aft horn gets drilled according to the dimensions on the plans. I then built up a spacer out of some wood and a few select thicknesses of aluminum. With the elevators re-installed (for about the 10th time), lined up, and the spacer between the horns, I drilled the second horn.

And finally the cool part, setting the horizontal stabilizer on the fuselage. I had to move the fuselage a bit. It’s certainly getting very tight in the small garage. I got the HS right where it needed to be and then realized that I should have previously drilled holes in the reinforcement bars on the F-711 bulkhead. I disassembled everything and did that.

I got the HS centered again and measured from the HS tips to the front of the corresponding longeron. Everthing looked lined up nicely. It took a while to find the dimensions for the holes that hold down the front HS spar. I marked those on the HS and then spent some time making sure those would hit the proper spot on the longerons.

After all of the tweaking and measuring, I decided it would be good to wait for the final drilling. I want to re-check all of the dimensions and measurement with a clear head.

With the tubing mostly done, the next logical area of work would be to attach the empennage to the fuselage. I’ll probably disassemble it all to save space afterward, but I can at least get everything fitted.

I pulled out the horizontal stabilizer and elevators, and wiped off all of the dust. It turns out that I never fine tuned the distance between the elevators and HS. That was a good place to start.

I spent about half an hour trying to get one bolt inserted through the bearing with various tools before I decided I needed a different approach. Cleaveland sells a nice hinge bolt tool, but I didn’t want to wait a week for that to show up. Instead I fashioned a bolt holder out of some .025 sheet. My first attempt didn’t work very well, but the second version was awesome. I used a couple of bent nails to hold things temporarily and then inserted the bolts with my handy tool.

I fine tuned the bearing distance. On both sides, the inner bearing distance ended up being 7/8″ (the max) and the outer bearings were 13/16″. I previously trimmed back the HS skin to account for the longer weight arm of the RV-7 elevators, but one side still needed further trimming once the bearings were set correctly.

I pulled out the drill bushing I bought from McMaster and used that to drill a hole in each elevator horn. The bushing was a little too large (about .003″) to fit in the bearing, so I chucked it in the drill press and sanded it down with some emory cloth. It still wouldn’t go in all the way, but it was in far enough to align the drill bit correctly.

I also removed about 3/8″ of the HS rear spar below the elevators horns in order to get a good amount of down travel. This was another step I skipped back when working on the empennage. I’m glad I skipped it. Now it seems like a trivial thing to do, whereas 1.5 years ago I was very nervous to cut into the HS spar. I just drilled out the corners and then cut out the sections with a cut off disk in the Dremel.

I reassembled the elevators to the HS and called it a day. Working on the empennage again was rather fun. I can’t wait to get the HS mounted to the fuselage.