Dave’s RV-7A Building Log

I spent a lot of time today fitting the rear bulkheads of the baffles. I finally got smart today and pulled out the Dremel with a rotary cutter bit and went to town. Filing is for the finishing touches.

There is quite a bit of trimming necessary on the right rear and left inner rear bulkheads. This was the trouble spot on the right side, right around the engine mount bolt.

This shows a little tab on the bottom of the right rear bulkhead. It’s not mentioned anywhere in the plans, but I noticed a little notch while I was deburring that usually indicates a bend line. Sure enough, bending the tab a little bit makes it fit better around the base of the cylinder.

Don’t do this! I saw this little modification on another builder’s site. I thought I needed the same thing. Later in the day I realized that by moving the hose clamp on the line behind the flange, the whole thing moves back and up out of the way. I didn’t need to make the notch, but it’s not going to hurt anything.

At this point the sides and rear bulkheads are fitting really well and are all deburred. That may not sound like much, but it took a lot of time.

For a short diversion during the day, I drilled the oil door hinge I made the other day to the cowl and door. Turned out quite excellent. Now I just need the Hartwell latches and a spring from McMaster for the hinge.

I worked a bit more on the baffling. I fitted the rear bracket to the back of the engine. It took quite a bit of tweaking to get it to fit. I guess every engine is cast a little differently. It sits a way back from where I think the back bulkheads will end up. I might have to bend it a bit more.

I also deburred the side baffles and drilled some of the bolt reinforcements.

I officially started working on the baffling. I basically just did a test fit of the sides and back. The sides fit really well. The back left fit OK, and the back right required some major filing. I guess every engine is slightly different. On mine the baffle hung up right around the top right engine mount nut. I also messed with the front floors a bit. The prop oil line is in the way of the right floor. The instructions says to remove it temporarily. That won’t help me, though. My line is a rigid aluminum line. It won’t move very much. I remember seeing someone else cut a slot in the floor and then make a filler plate behind it. I also tried to picture how the engine air intake snorkel fits with the left floor. I’ve been warned by other builders that the snorkel will need some surgery in order to fit. So far, I can’t figure out how it’s going to work.

I sanded the cowl a little bit, but quickly decided to do something else. Cowl boredom is setting in.

I pulled out the exhaust pipes. Considering all of the tricky bends and twists, these things fit amazingly. I just put them together, installed the gaskets and put the nuts on the studs. A couple of spots have very limited access. I didn’t tighten down the nuts yet. Getting a wrench on a couple of them is going to be impossible.

Pete James sent me some more photos of his engine. The engine mount on the taildragger definitely makes it easier to route the fuel line between the pump and the servo. I tweaked the clamps a little bit and got the fuel line to sit better. I’m sure it’s just a matter of tweaking and maybe adding a clamp at the engine mount, although the mount moves independent of the engine. It’s probably better not to secure it to the engine mount.

I also installed a 90 degree fitting into the fuel pump and attached the fuel line from the pump to the firewall. I don’t like the looks of the flex in the line, but maybe it’s OK. I’ll get a second opinion on it.

One of the first steps of working on the cowl is to make sure the engine is in its final position. I re-checked the torque on all of the engine mount to firewall bolts. I haven’t secured the cotter pins yet, just in case I might need to remove it still. I think once the P-mags get here (the check cleared so they must be close) and I install them, I’ll be confident the engine is on for good.

Next up were the engine mount bolts. The instructions say that you can’t use a torque wrench on the engine mount nuts, which is true. There just isn’t enough room. I can barely get a box wrench on them. Torquing from the bolts doesn’t work because the rubber mounts put a lot of drag on the bolts. In spite of all that, I looked up the torque value for AN7 bolts. The minimum value is 450 in-lb! My click torque wrench doesn’t even go that high. I have a beam-style torque wrench that does. I clamped it in the vise and reefed it up to 450 in-lb. That’s a lot of torque. With my shorter wrenches, it would be hard to even get that much torque on the bolts.

With that info in mind, I re-checked the engine mount bolts. The top left bolt was good. The top right bolt seemed like it could use more torque. But that caused the cotter pin hole to not line up. I tried a dozen combinations of washers, but nothing worked well. I finally settled for slightly less torque, but having the hole line up.

When I checked the bottom bolts, I discovered that I hadn’t even tightened them all the way up up against the inner metal sleeve. When I did tighten them, the cotter pin hole was too high on the nut. I removed both nuts and added another washer on each. I tightened both bolts until they were hard against the sleeve and then lined up the cotter pin hole. One side is tighter than the other, but they’re both nicely secured. I bent down the cotter pins on all 4 bolts, so they’re not going anywhere now.

I never thought it would take so much time just to secure the engine mount bolts, but I’d rather get it right. As my family and friends keep pointing out, “There’s only 4 bolts holding the engine on.” Ahhh, yeah. How many did you expect?

I picked up four 1/2″ x 3″ x 20 tpi bolts at Lowes for about a buck a piece. Eventhough they were individually packaged, the threads were really banged up. I spent quite a bit of time with a file cleaning up threads. I then cut 4 chunks of 3/4″ PVC to 2-1/8″. The FAQ on Van’s site says to cut them to 2-1/4″, but a few people on the forum suggested making them slightly shorter for a Hartzell constant-speed prop. The holes in the spinner back plate are larger than the bolts, making it difficult to get the plate positioned correctly. I drew a 1″ circle around each hole so I could center the bolt head. I then temporarily installed the spinner back plate to the starter ring/crankshaft with the PVC spacers and the bolts. It’s ready for cowl fitting.

I next decided to tinker with the fuel lines. The fuel-pump-to-servo fuel line that Van’s supplied in the FWF kit was not long enough. I’m guessing that maybe there’s a gusset on the nose wheel mount that is different than the tail wheel mount? Luckily, Mattituck supplied a fuel line that was a few inches longer. It seems that there are two options for routing it around the engine mount, neither one ideal. For one route, the line rubs on the engine mount gusset and the other route makes the line take some awkward bends. I’m hoping I can install enough adel clamps to make it work. Right now the thing wants to rub on the engine mount and back left intake tube and interfere with the mixture bellcrank.

The fuel line from the firewall to the fuel pump is even worse. The mount for the prop governor is in the way of the fuel pump inlet. Again, Mattituck supplied an extra fuel pump elbow, so I can point the inlet downward. However, that makes the fuel line way too long.

It’s pretty frustrating when these $70+ hoses don’t fit. I know I’m not the first person to install an IO360-M1B clone on a 7A.

I drilled the heads of the bolts for the throttle bracket. Using a new cobalt 1/16″ drill bit made it easy. I used Dan’s trick and threaded a nut part way onto the bolt to help hold the bolt steady in the drill press. I had to file the holes in the bracket a tiny bit to get the bolts to fit. The holes in the sump were just a millimeter closer together than the bracket. I then torqued and safety wired the bolts in place. I was told that this bracket might cause interference with the exhast pipes, but we’ll see.

I next worked on the engine bolts again. I added an extra washer to each top bolt. On the right bolt, the cotter pin hole just would not line up on the nut. I tried two different sets of washers and finally found a combination that caused the hole to line up perfectly.

I started to mess with the breather tube, but it seems that the oil filter adapter that Mattituck uses puts the filter right in the way. I’ll have to see what others have done.

Happy 2006!

I worked on getting the mixture brackets installed. The aft bracket (that holds the control cable housing) installed very easily. I was slightly nervous about messing with the sump bolts, but forged ahead.

The bracket that holds the swing arm didn’t install quite as easily. A tiny bit of extra aluminum around the sump bolt holes was in the way. I carefully used a file and cleared it away. The bracket then fit perfectly. Hooking up the bearing end to the mixture arm was easy. The mechanism works at kind of a weird angle, but it does work very smoothly.

I didn’t spend too much time on the plane today. Yesterday was a big day.

I returned the hoist, cleaned up the garage, and re-arranged a bit. I did work on the engine bolt torque a bit. The left top bolt is the tough one. A push rod tube is in the way. On all the others, I can use a box wrench quite easily. The bottom bolts look great. On the top bolts, I’m not quite happy with how the cotter pin hole is situated in the slot of the nut. I might add another washer, as the instructions suggest.

I called up the rental place this morning and they are going to be closed starting at noon tomorrow until Monday. I didn’t want to rent the hoist for 2 days, and didn’t want to wait until Monday. I guess today is the day. I swung by and picked up the hoist. It is an ugly beast–about 3X larger than it needs to be. I assembled it fairly easily, but took a while figuring out how to rig something on the end of it to lift the engine. With that done, I discovered the thing wouldn’t fit around the pallet that the engine was sitting on. Time to pull out the Sawzall. A few quick cuts and the hoist was in position.

Getting the engine unbolted from the pallet was a bit of a hassle. Once I figured out that the nuts on the bottom mounts were 11/16″, things went much quicker. It took quite a bit of jockeying to get the hoist into position, especially since one wheel on the darn thing would not pivot. I was planning on just pushing the plane into the driveway, but it rained all afternoon. Julie helped keep the engine steady while I wheeled and lifted it into place. I had to remove the oil filter since it’s on an adapter, but I expected that. The prop governor was not in the way at all. I’m very glad I mounted that while the back of the engine was more accessible.

I followed the guide in the 24 years of the RVator. The first and second bolts went in very easily.

The third bolt was a bit more of a challenge.

The fourth bolt looked impossible. I took a break for dinner. After re-reading the guide, I loosened two of the previous bolts and was able to apply just the right leverage on the rubber mount with a large screwdriver and some wood blocks. The bolt slipped right into place!

This is quite an inspiring step. If I wasn’t so beat, I would pull out the exhaust, fuel lines, baffles, and cowls and start going to town.