Dave’s RV-7A Building Log

Julie was nice enough to jump up after breakfast and help with some riveting, all of which happened to be under the fuselage. We riveted in the floor stiffeners, this time in the right direction. We also got to the COM antenna doublers. And finally finished the riveting on the pitch servo mounting bracket. It all went very smoothly. It’s great to have an experienced riveter around.

Since the doublers were in place, I decided to mount the COM antennas. Looks great except for one minor problem. I didn’t have long enough screws. I added those to the perpetual list. Meanwhile, I’ll leave them clecoed in place. One’s for the GNS-430 and one’s for the SL-40. It’s a little bit of a drag (literally) having two antennas out in the wind, but I’m willing to pay that price to have two good radios. Too many times I’ve heard on the radio “Experiment… shh… shh… two… shh… shh… turning… shh…”. I want to hear and be heard.

Later in the day I started permanently riveting the subpanel structure together. I started with the subpanel ribs to firewall. I realized this was going to be some tough riveting because the engine mount is in the way, so that’s where I started. I back riveted with a bucking bar on the front side. It was really tricky as the firewall is slick and the rivet gun is pretty wiley. I had to drill out and re-do a few of them. And then wouldn’t you know the stupid bucking bar slipped on one of the rivets and I got a little bit of a bump. Oh well. I tried hammering it out a little bit, but it is what it is. Good thing I didn’t bother polishing the firewall.

I finished up the stick wiring. Now that I knew the trick for the Molex Microfit 3.0 connectors, it went really smoothly. I followed my sketched out drawing carefully, stripping wires and crimping pins. The stick, relays, indicators, and servos all connect here with the Molex connectors. I can easily remove and replace any component. Looks a little messy now–a wiring job only a builder could appreciate. I’ll get it all wire-tied and pretty as soon as I test the direction of the elevator servo.

I trial fitted one of the AN3-60 bolts to the brake pedals a few days ago. Figured it should do the rest before riveting in the subpanel structure. It wasn’t fun leaning over the side of the fuselage and messing with the bolts in a tight space, but I got it done.

I originally ordered 2 Hartwell latches from Wicks and got two different types. One looked like it would work well for mounting in fiberglass and the other aluminum sheet. I asked them to send a matched set, and unfortunately didn’t specify which I wanted. Of course I got the aluminum sheet ones. So I placed another order for a matched set this time and nicely asked for ones that have the latches approx 0.1″ proud of the mounting plate. Bingo! These look perfect. I did a tiny bit more filing to improve the fit and then drilled them to the oil door. I’ll need to use some washers or epoxy filler or something before riveting so the latches will follow the curve correctly. Still need to figure that out.

For some reason, Julie wanted a picture of the Guest Room, rechristened the Wing Room. The picture doesn’t even do it justice. The wings, flaps, and ailerons are visible, but the empennage is tucked way in the back. The canopy is off to the right and all the wheel pants are behind that. Plus all the stuff that would normally be in the garage is packed in here. I promise it will all go to the hangar soon, Julie.

I messed with the stick wiring some more. I was swearing a good deal at the Molex Microfit 3.0 connectors that I decided to try. I couldn’t get the pins to sit right. I was shoving them in, they were going in too far, bending the tabs, getting stuck, etc. I was really getting frustrated and burning through the fairly expensive pins.

I was about to go back to the DB-9 style pins, when I finally figured out my issue. The pins insert into the connector in one direction and one direction only. When it’s all lined up right, they just slide right in and click very subtley. Now that I know what’s going on, I think I have the wrong extraction tool, because I can’t see how it could depress the tabs on both sides of the pin at the same time. But with the right tool, the pins should come right back out again. That’ll be handy for swapping wires if servos are running backward.

Now that I’m on the right track, I should be able to cruise on the stick wiring.

It’s time to step up the picture taking. This first one is for Jeff on the VAF forum who was asking about the adjustments on the camlocs. Turns out I did have to push them up quite a bit. Still plenty of threads engaged, though.

I checked around on various builder logs and most seem to make this bracket work. I tweaked it a bit with a Crescent wrench and seamer and was able to get just enough clearance to the exhaust pipe while still getting the cable lined up pretty good with the lever arm. Vans recommends a heat shield and firesleeve for the cable, so hopefully that’s enough. Of course after I got the whole thing in there, I realized I forgot the retainer rings for the firewall eyeball. It’s always something. Hopefully this is the final time I’ll have to touch it other than safety wire and cotter pins. I had to dink with the location of the bulkhead nuts in order to get the full swing of the throttle. This picture is looking back along the bottom of the engine at the throttle cable.

This is a shot of the mixture cable. I took the whole darn thing apart again to add the star washer for the bulkhead nuts. The lever operates stop to stop and doesn’t interfere with anything. Looking great.

I loosely installed the firewall eyeballs. They’re a tiny bit too big, so I slipped some heat shrink over the cable that I’ll shrink into place once I establish the correct position. These eyeballs are definitely much more hassle than the one-hole variety. This shows the mixture cable on the left and prop on the right. As noted by other builders, the prop cable takes quite a bend at the firewall but still operates fine.

I removed the prop cable as well to add the star washer (after this shot). I’m also going to replace the lock-nut with a castle nut and cotter pin once I order the correct length bolt. Every other control connection is using a castle nut, which is much more secure than a lock nut. No problem getting the full swing on the prop control. It’s much less than the travel provided by the cable. This shot is looking down at the back of the engine.

Now to work on the other end of the control cables, which is hopefully much easier.

EAA 1440 meeting last night, so no work on the plane. No organized program for the meeting. We just showed pictures and told stories from the summer air shows. Fun meeting.

Tonight Julie was out with some women from work and Adele was staying at grandma’s house. That means the evening is all about the plane, after a short walk for Leo.

I spent a fair amount of time inventorying a few orders that arrived recently. I try to take notes on what everything is for when I order it, but it was still hard to sort out what hardware was for what purpose.

The long brake pedal bolts AN3-60 arrived from Wicks. A guy on the VAF forum suggested these as a way to improve the action of the brake pedals to keep them from dragging. I decided to try one out. It was a bear to remove the old bolts and install the new one with the whole pedal assembly in place in the plane, but I didn’t want to take it out. The hassle was well worth the effort. There’s much less friction in the pedal and it does a much more positive return to the stop when released. A shorter bolt would have been better, but they’re much more expensive. I put a few extra washers on this one and it works great.

The custom engine control cables arrived from Vans over the weekend and the larger aluminum eyeballs arrived from Spruce. Time to finally get the controls hooked up. These cables are going to work perfectly. The prop cable takes kind of a sharp bend at the firewall, but seems OK. The mixture cable is perfect, although a bit difficult to hook up in the small space. The throttle cable is the trouble-maker. I removed the steel bracket and tried bending it some more so the cable would clear the exhaust pipe underneath. It’s just pointing at a weird angle. Pulling the cable all the way to idle isn’t smooth and the bracket bends a bit. That can’t be good. I tried putting the bracket on backwards so the cable goes on the other side of the mount. There’s more clearance to the exhaust that way, but it’s still at a weird angle. I might follow Pete James’ lead and fabricate my own bracket out of some .125 angle.

The worst part about the control cables is that I always get the entire assembly hooked up and then realize that I forgot to put the seals back on the cable. The whole assembly has to come out again. Arggggh! And then to top that, the custom control cables only had one star washer for the two bulkhead nuts. I thought that was strange, but installed it that way anyway. Turns out the original knob cables from Vans had two star washers, so I’ll end up taking the whole darn thing apart again to put that extra star washer in. Better safe than sorry.

Didn’t get at far as I would have liked tonight, but at least it’s forward progress on these stupid control cables.

After a 3-day weekend of camping, I’m back to building. It was good to get away for a little while and not think about the plane every waking moment. Instead I only thought about it every other moment.

As an easy task to get back into it, I installed the push tube between the control stick and the bellcrank. I almost made this impossible by installing the autopilot servo, but it was doable. At first I couldn’t figure out how to get it in without bending or cutting something. Then I checked the back-up building manual, Dan’s site. Easy as pie.

I connected the push tube to the bellcrank, but didn’t secure the other end yet so I could still move the tube out of the way for riveting the seat pan nut plates. Going to do that soon.

Speaking of getting the seat pans installed, I first needed to get the wiring done for the pilot’s control stick. I’ve spent a few hours figuring out the best way to wire up the trim servos, relays, switches, and indicators, and drawn up a wiring diagram. It’s not rocket science, but it’s definitely not straight-forward. I have a back-up switch for the elevator trim on the panel, so that complicates things a little bit as well.

I bought some cool, tiny connectors from Digikey, Molex Microfit 3.0. Turns out I needed a different crimper for the pins, and that just arrived last week. My first attempt at crimping the tiny pins worked great. I did the connectors for the relays first. No sweat. I started working on the connectors in the plane, but didn’t finish them.

I called up Advanced Flight Systems and talked to Ken to check on the status of the AF-3400. Sounds like more delays. The wiring harness and probes will be available in a few weeks, at the end of August. The screens are out to late September, October at the latest. Not great news, but I’ve got plenty to work on for the time being.

I started off by priming the autopilot servo parts, the pitch servo mount and the push tubes.

I decided to verify the connections in the harness from Stark, starting with the autopilot. I also wasn’t quite sure which output from the GPS had been hooked up to the autopilot, so I verified that. Then I found the little slip of yellow paper from Stark with handwriting on it. I thought they accidentally dropped their notes in the box, but it actually spells out exactly which serial or ARINC connection goes where. I also initially thought Stark had wired up the ARINC connections to the GPS in an odd way, but they’re actually perfect. It took about half an hour to verify the autopilot connectors. I started doing the GPS connectors, but soon realized it’s going to take forever to verify everything. I’ll just trust the rest based on my findings with the A/P connectors, which turned out 100% correct. I can’t imagine how long it would have taken to wire up all this stuff. Money well spent.

I clecoed the pitch servo mount in place and set the rivets into the bottom fuselage rib. Adele helped me with the pop rivet dimpler on the bottom skin, but I’ll need Julie’s help to set the rivets. I figured I might as well install the pitch motor. And the push rod. I had to mess around quite a bit with washers to get a satisfactory fit. I ended up using some of the extra small diameter washers I ordered for the engine control linkages. They allow the rod end bearings to pivot more. Initially the push rod was rubbing on the bellcrank, so I added another washer there. I also put a washer inside the bellcrank, since the two sides are spaced apart. The dimension for the push rod in the drawing looked pretty good, but I might still adjust it later. I safety wired the mounting bolts for the motor and called it good for now.

FedEx Ground screwed up and didn’t hold my package like I requested, but luckily someone was home to sign for it. The Trutrak DigiFlight II looks great. I tested the fit in the panel and it’s perfect–maybe a little too snug considering the panel isn’t painted yet. I will need to trim the Nulites I have on either side for the altimeter and airspeed. Should be no big deal.

A few builders have commented about the weight of the servos. They definitely feel heavy, but they’re only 2.5 pounds each. They’re just heavy for how small they are. Dense is the word I’m looking for. 5 pounds is nothing. I’ve gained that much weight since Spring since I’ve been working on this crazy project instead of bike riding like I usually do in the summer.

I started right in on installing the pitch servo. Immediately I noticed the drawing provided by Trutrak did not correctly depict the bottom fuselage rib. A little searching shows this has been a problem for years. Just forge forward using the dimensions from the drawing. However, even the dimension aren’t correctly depicted on the drawing. The dimension on the bellcrank is 2.5″ on a 1:1 scale drawing, but measured out to 2-3/8″. Also, the drawings don’t show what fasteners to use or how to attach the servo support. Ok. Trutrak’s drawings are lousy and they obviously don’t care. Move on.

In a nutshell, here are the steps for mounting the servo support: Lay out four #40 holes along the bottom of the support. Drill out the four rivets in the fuselage bottom rib covered by the support. Clamp the servo support in place. Drill the fuselage rib holes to the support and cleco. If you place the support correctly, the four rivets will be perfectly positioned on the support. Now use a long #40 drill bit to match drill the holes you made in the bottom of the support to the fuselage skin. Countersink those 4 #40 holes in the support. Dimple the fuselage skin. Rivet. Miller time.

I did all but the last two steps, plus I want to prime the support before I rivet. It doesn’t appear to be alclad. It was cool to get so far with the autopilot considering it just showed up today.

The only thing preventing me from riveting down the seat floors is the wiring for the pilot’s stick. That means I needed to figure out how to wire up the trim. It’s the most complicated system on the plane because I have a hat switch on the stick connected to two relays plus a back-up elevator switch on the panel. Add to that wires to the AFS engine monitor for trim indicators. The stick also has switches for push-to-talk and control wheel steering for the auto pilot. I’m trying to get all of that wired up without a tangle of wires running everwhere. I think I can do it with two of the Ray Allen 5-conductor cables running from the panel to the stick.

I spent some time with the parts, a pencil, and some paper and got it all figured out. I was ready to start connecting wires together when I realized I don’t have the right crimper for the nifty Molex Micro-Fit 3.0 connectors I bought from Digikey a while back. I ordered the crimper and pin insert/remove tool from Digikey.

My major task for the day was to replace the floor stiffeners. I ended up putting them in backward way back. I guess I got confused the the left/right, up/down reversal when the fuse was upside down. All this time, I figured it wouldn’t matter much, but the precut carpets from Classic Aero won’t fit. I could try to re-cut the foam, but I’d rather just make the stiffeners go the right direction. I drilled out the old stiffeneers, as seen in the picture below. Ironic that the one moment Julie decided to capture is when I’m ignobly trying to correct a stupid mistake. I drilled the new stiffeners to the bottom skin, countersunk them, and painted them. They’re now ready for riveting, which probably won’t happen for quite a while the way things are going.

I also worked on the forward upper structure a bit. I riveted a couple of spots that I left undone for some reason. They were tough rivets, but not impossible.

I also dimpled the firewall and the ribs as needed. Dimpling the 1/8″ holes in the firewall was tricky since I don’t have that size pop dimpler set. I ended up using the 1/8″ dimple set in the rivet gun turned way down. Worked great. Trying to rivet in that spot is going to be tight.

I also cut off the front part of the right subpanel rib. I left it on for quite a while, but it’s obviously going to be in the way of the AF-3400 EMS screen. I might move it over. I might leave it out. We’ll see.

I did some other miscellaneous riveting on the structure, but I don’t want to put it in until the floor stiffeners are in. That structure will severly hinder access for riveting the stiffeners.