Dave’s RV-7A Building Log

Deburred the rest of the holes in the left fuel tank skin. Countersunk the holes in the filler flange. The flange comes pre-bent to match the curvature of the tank. I put the flange down on a flat surface to figure out the orientation of the bends. One side looked a little more bent than the other, so I put that toward the front side of the tank. Drilled the drain flange to the skin. Fabricated the vent line clip that attaches to the flange.

Dimpled the holes around the edge of the fuel tank skin. Adele dimpled the fuel tank stiffeners with the 3T dimple dies, and I made sure she was very safe with the pneumatic squeezer. But her worrisome mother didn’t approve.

I went back and forth trying to decide whether to remove all of the plastic protective covering or just the necessary strips around the rivets. On the empennage, I removed just the strips. It was time consuming. And you end up scratching the skins anyway around the rivets. It’s inevitable when you’re maneuvering around there with a deburring bit, dimple dies, the squeezer, a bucking bar, and rivet gun. It’s impossible to prevent every scratch. The surface gets scuffed up anyway for painting. On the bottom of the fuel tank skin, you have the ribs going one direction and the stiffeners going the other. You’d end up with small little patches of plastic, which wouldn’t do much anyway. With all of that in mind, I bought some scrap carpet to try to protect the skins as much as possible and just removed all of the plastic.

I’m getting very close to having the left fuel tank ready for assembly. However, I think I’m actually going to put together the leading edge first. I’d like to get some more practice riveting before I take on the challenge of ProSeal.

Deburred the inside of the left fuel tank skin.

Received my order from Van’s containing two fuel pickups (you can make your own, but Van’s sells these pre-made ones with a nice screen as an option for $6.25 each), an assortment of “oops” rivets (I ordered .2 pounds of each size for a total of about $30–should be enough for the rest of the project), wing conduit, 3/4″ snap bushings (still not sure if I’m going to use the conduit or go with just snap bushings for the wing wiring), clear plastic tubing (for plumbing the pitot tube), and a whole bunch of ProSeal in the tubes.

I put the NAS1097AD3 rivets to use right away. A recent RVator (Van’s newsletter) mentioned that these rivets are good for attaching nut plates to items that are too thin to countersink. The rivets have a smaller head than normal, so they can’t be used in structural locations. For holding on a nut plate, they are perfect.

I countersunk the capacitive plates just a bit with the deburring tool and attached the nut plates with NAS1097AD3 rivets. Worked great.

I also cut the notch in the snap bushings for the fuel tank vent. It took me a while to figure out a good way of doing that. The bushings are tough, so filing had little effect. Drilling didn’t work. The notch is so close to the edge and the surface so slick, the bit just slipped right off the bushing, even in a drill press. I finally used the Dremel with a bit that looks like a mini reamer. Tested the fit with the tubing and a small chunk of wire.

Adele also helped me dimple all of the fuel tank ribs. I put the squeezer in a vice. She loves running the trigger on the pneumatic squeezer and I move the part around. She’s never punched an extra hole, so she’s doing much better than me, so far. I used the “3T” dimple dies from Cleaveland that make a slightly deeper dimple. That’s supposed to allow some extra room for the sealant so the skins way lay flatter.

Drilled the fuel filler flange using the skin as a guide.

I also set up the fly cutter for making the access hole in the inboard end rib of the fuel tank. I’m really tired today after my first solo cross country, so I’m going to leave the actual hole cutting for tomorrow when I can double check my measurements with a more alert mind.

Countersunk the holes in the left fuel tank skin that attach the rear baffle. I’d much rather dimple than countersink, but the instructions say countersinking will make it easier to slide in the baffle during assembly.

That’s the last step with the fuel tank clecoed together, so I took it all apart. I drilled the attach angle and tip reinforcements to the innermost and outermost ribs. I didn’t see a pattern for the rivets for the outermost ribs, so I used the same pattern as the innermost. Turns out the instructions later say to use just 4 or 5 rivets. Oh well. A couple extra won’t hurt.

I started working on the capacitive senders by drilling the plates to the appropriate ribs and cutting notches in the outboard plate to clear the stiffeners. I think the notches are only needed on one of the plates.

I deburred all of the left fuel tank ribs, the sender plates, and a few other doodads. You know you’ve deburred a lot when the cordless screwdriver battery gives out. That’s always a good sign to stop.

Artsy photo of Adele’s reflection in the fuel tank skin.

Final drilled all of the holes in the left fuel tank. Drilled the fuel tank skin to the joint plate.

Tried to find some other stuff to do while waiting on some help. I fabricated the fuel pickup anti-rotation brackets. A lot of work for two tiny pieces of aluminum.

Julie helped me rivet the three nut plates onto the spar for the inboard-most fuel tank Z bracket. Of course after we went through this hassle, I read Dan’s site some more and he used blind rivets there. Oh well.

With the last Z bracket installed, I went to town. I back-drilled the inboard bracket through the tank baffle using the long #30 drill bit.

Removed the leading edge. Drilled the outboard bracket.

Removed the fuel tank skin and internal ribs.

Drilled the remaining brackets.

Re-assembled the fuel tank so that it’s now ready for final drilling.

I also worked on the hole for the tie-down ring. I didn’t like the method in the instructions of finding the hole. With the leading edge off, I marked the location of the tie down hole on the spar. Put the leading edge back on and transferred the marks. Worked great. Filed the hole in the right direction. Drilled it to #10. Filed it a bit more in the right direction. Drilled with the Unibit to 5/16″. I’ll drill the rest (7/16″ should be enough) with the leading edge off. I don’t want to screw up the tie down threads.

Finished up the fabrication of the fuel tank attach brackets. Deburred some other miscellaneous tank parts: the access plate and reinforcement ring, and the backing plates for the tips of the inboard and outboard ribs.

Since I’m using the capacitive senders, but the regular fuel pickups, I guess I’ll use the access plate without the holes. I’ll use the plate with holes as a template to drill for the fuel pickup.

Adele reminded me that it’s been exactly 6 months since the first box arrived. I think my progress has been pretty good. I’ll just keep building away–a little bit every day.

While waiting for some help attaching the nut plates to the main spar for the innermost tank attach bracket, I’m doing some other tank prep stuff. I spent some time fabricating the fuselage attach angles for the tanks, doing the rough cuts on the band saw and cleaning up with the stationary belt/disk sander, a small round file, and the Scotch-brite wheel. The band saw is an invaluable tool for fabrication. It’s probably 5 times faster than using a hack saw.

I’m not spending as much time on the project this week. I decided to concentrate on finishing up my private pilot license. At this point, I basically need to do my solo cross country time, a little more simulated instrument time, polish up my ground and performance maneuvers, and study for the practical exam.

After flying 4 days in a row (2 solo), I’m pretty tired tonight. Didn’t do much on the project. Just deburred the holes in the left tank stiffeners.

Julie helped me cleco the ribs into the left fuel tank. This is not an easy task. It’s much easier with two people. I push down on the ribs from the top. She sights through the hole, tells me when it’s lined up, and puts in the clecos. Hopefully it’s easier the next time when it’s all slathered up with ProSeal.

Earlier in the evening while waiting for Julie to get home, I final drilled the fuel tank stiffeners to the skin and numbered them.

I also riveted the nut plates onto the tank attach Z-brackets, and bolted the Z-brackets to the spar. Putting bolts into a brand new nut plate is not fun. Boelube helps, but doesn’t make it easy.

I countersunk the spar for the nut plates that hold on the inboard-most Z-bracket. Not sure why they don’t tell you to put that nut plate on at the very beginning with all of the other nut plates. It will be fun bucking those nut plates on with the wing ribs in the way.

I clecoed the rear baffle onto the fuel tank and set it on top of the wing. Looks awesome! Yet so far to go.