Dave’s RV-7A Building Log

I epoxied an AD5-4 rivet in the end of this fitting for the manifold pressure. It’s difficult to see, but there’s a 1/16″ hole drilled through the middle of the rivet. Should make an effective restrictor.

The fuel hoses arrived back that Spencer Aircraft modified for me. The hose from the firewall to the mechanical pump looks OK, although now I’m reading reports that having a 90 degree fitting in the pump inlet is a bad idea.

The modifications for the fuel flow sensor did not work out as well. The sensor block with the fittings is a long stretch that wants to remain straight. Not good for bending around the engine mount. The fuel line gets way too close to the exhuast. Might install a 45 or 90 degree fitting in the outlet. Not ideal for the flow sensor, but I don’t see another solution.

Started messing around with the wing tip fitting, but couldn’t figure out why the ailerons seem to be in the way.

Pop riveted the seals in place. The RTV didn’t hold so well. The seal material puckered between the rivets and lifted right off the RTV. Maybe I should have riveted them with the RTV not set up?? It won’t be a big deal. It seems like the seal will still push tightly against the baffle.

Worked on trimming the baffle seals to fit. I cut a few notches to allow the seal material to conform to the cowl and trimmed around the inlets a bit. The cowl seems to be sitting down pretty good. The process reminds me of trimming the baffles. It’s a lot of taking the cowl on and off and trimming.

Finished drilling the baffle seals. I read on one of the RV forums, that applying some RTV between the baffles and seals is a good idea. The seal material tends to pucker, so the RTV will hold it in place. We’ll see.

Julie helped me move the wings and stuff out of the guest room and back into the garage. Time to get the wings finished off and moved down to the hangar.

I decided it was time to drill the seals to the baffles. Not much to it. I laid out the holes on the baffles 1/2″ down from the edge, about 1-1/2″ between. I then clamped the seal material in place and drilled to #30.

I decided to leave a little more extra above the baffles for a total of about 2-1/4 inches. I marked on the material with a ball point pen and cut them out. Not too tricky.

I spent a bunch of time looking through the Mouser catalog for some better knobs, push button switches, and mini toggles. I also found the coax and Molex connectors that SteinAir sells. I’d rather get them from Mouser, plus they sell them cheaper. The coax connectors are Mouser part# 523-31-320-RFX. The Molex connectors can be found by searching for “Molex .084″. I was going to order the coax connectors from B&C, but they are now selling a genuine mil-spec connector that costs $5 each. The connectors that I’ve been using from SteinAir seem just fine and cost $1.33 in quantities of 10, which is how many I need. $13.30 sound much better than $50 for 10 connectors.

While I’m waiting for a few electrical parts from B&C, I decided to finish off the baffles. The only remaining task is to cut and install the rubber baffle seal material around the top. I looked all over for the baffle instructions, but I seem to have hidden them somewhere. I ended up cleaning up the workbench in the process, which isn’t a bad thing. If I remember right, the only thing they say about the seals is to install them. I don’t think there was much helpful information. I did some searching on the forums to find some advice. Leaving 2″ of material above the baffle walls is a good starting place. I’m going to try 1″ below.

I used some paper grocery bags to make templates, holding them up to the baffles, drawing a line, and then cutting them out. Looks like I’ll be able to use one strip for each side, front, back, and sides. I’m not sure if that’s a good idea. Getting the baffles off will be impossible without a break in the middle of each side where there’s a seam in the baffles. Time for more research.

The debacle with the control cables just won’t end. I spent a week and a half working with Spruce to see if I could get the correct travel/throw on the custom control cables. I finally got the word yesterday that they could do it. The price would be $80 each. That’s almost twice the cost of the Vans custom cables, but I need the smaller diameter cable for the firewall eyeballs that I have, so I placed the order. Spruce called back today and said they quoted me the wrong price. It’s going to be $139 per cable because they’re custom. That’s crazy. I cancelled the order. It’s back to the drawing board. I’m going to use Vans cables. I’ll try contacting the maker of the eyeballs to see if they make one with a larger hole. If not, I’ll have to go with aluminum firewall eyeballs and somehow cover up the mounting holes I already spend hours drilling.

This throttle quadrant has been a huge waste of time and money. I will give credit to the people at Spruce. They charge ridiculous prices for their stuff, but at least their staff is helpful and responsive.

I wasn’t feeling well today. Don’t know if it was a bug or simply being over-tired. I had reserved a plane for 1pm to practice some landings and maneuvers. The weather was absolutely perfect, but I just didn’t feel up to it. I spent time with the family and messing around on the plane instead.

I finally came to terms with the control cable quandry. I read through the entire section in the Spruce catelog and didn’t find any information that would have prevented me from mis-ordering. I did find one helpful thing, an optional polyolefin covering for the cables. I’ll get that on the next ones.

I also decided to double (and maybe triple) check that the lengths were correct. I placed all of the various arms and adjustments to their mid-position. I mounted the panel and quadrant back in the plane and placed the levers to their mid positions. While I held the cable roughly where I wanted it to be routed, Julie measured the difference between the end of the cable and the mounting hole in the quadrant lever. Adding on 7/8″ for the clevis end, I then calculated the correct length for each cable: mixture 51″, prop 48″, throttle 50″. There’s a fair amount of adjustability at each end and in the routing, so +/- 1″ would even work OK.

The mixture cable especially has a lot of flexibility since the arm angle can be changed to any position and the end on the lever arm can be adjusted. I put everything at its mid-position and mounted the mixture arm so the lever arm doesn’t hit the bracket. Hard to describe, but you’ll understand when you get here.

I got some great responses from the Yahoo Lycoming group. The standard mag wiring is right mag to upper-right and lower-left spark plugs, left mag to upper-left and lower-right spark plugs. This is to balance out the RPM drop when doing a magneto test. Dan also suggested just wiring one side to all upper and the other to all lower just to make troubleshooting easier, which was a good idea. In the end, I decided to go with the standard wiring. EmagAir provides all the parts, a crimper, and great instructions for making the ignition harness. I put on 6 of the 8 coil ends onto the wires. It’s time consuming work, but I’m going very carefully.

I also ran down to the hardware store and picked up a couple parts for a poor-man’s prop torque extension. I wish I could claim that I thought of this, but I got it off the VAF forum. Buy a bolt and nut (and washer for good measure) that are the same size as the prop nut. In my case this was 3/4″

With my 3/4″ wrench on the prop nut, I put the bolt/nut “adapter” in the other end and then attached the torque wrench to it. I used the formula that came with the torque wrench to de-rate the torque value appropriately for the extension. Unfortunately, my good torque wrench doesn’t go high enough for the prop bolts. I’ll have to borrow one.

I worked further on the throttle quadrant control cables, the time hooking up the mixture cable. Again, I wasn’t able to get the full swing out of the mixture arm. No matter how I adjusted things, it just wasn’t working. And then it dawned on me what the problem was. The bulkhead nuts are not located in the same position relative to the end of the cable as the standard Vans cables. In the picture, the top cable is the end of Vans standard push/pull knob cable. The bottom cable is the standard Spruce A-1550.

When I figured that out, I was at first furious and then frustrated. I tried to think of how I can remedy the problem. I could fabricate new brackets for all the cables. But that would be a huge hassle, especially for the prop governor. The Aircraft Spruce catalog doesn’t mention this dimension anywhere. There are some mentions of the “travel” for a control cable, but now how that affects the bulkhead nut placement. I figured more travel was a good thing, but not in this case. It puts the bulkhead nuts further back on the cable. In the end I decided to just order new cables. They’re not cheap at $50 each, but I’d rather get them right as controlling the throttle, mixture, and prop pitch are kinda important. My main concern is that Spruce took 2 months to make them last time. Hopefully I can get that expedited somehow.

I wasn’t feeling much like working on the plane at this point. I looked around for the Pmag manual, but couldn’t find it in the usual piles. I decided to clean up the paperwork. Every little part for the plane comes with it’s own instruction manual. I grabbed a big 3-ring binder, a 3-hole punch, and some plastic Postit tabs and got it all organized by major category. Much better.

I eventually found the Pmag manual in the electrical pile and started figuring out how to wire up the spark plugs. Aircraft engines have two spark plugs for each cylinder. I know each cylinder should be fired by two separate sources, but I wasn’t sure if there was a standard approach to that. I asked the Lycoming Yahoo group.

Decided to install the seals I bought a long time ago from Aircraft Spruce. These seals allow the ignition wires to pass through the baffle. I could have used snap bushings, but these seals look cool and cover a larger area that will allow the wire to be installed/removed while keeping the bulky terminals intact.

The big drawback is that the seals have a really odd-shaped cut out. It took quite a while to figure out how to do it. In the end, it was fairly easy. Drill four holes in a line. The two outer ones get drilled to #10 for the AN3 bolts. The two inner ones get drilled out to 3/4″ each. I was worried about using the Unibit to enlarge the overlapping holes to 3/4″, but it ended up not being a problem. I just applied sideways pressure on the drill to keep the Unibit from catching in the overlapping area. I made a template out of stiff paper of the desired cut out shape and used that to draw an outline on the baffle. That helped quite a bit for coaxing the Unibit in the right direction. A little bit of filing to clean up, and they turned out great. Another item crossed off the list.

I spent a few hours while watching TV trying to figure out the innerconnects between the avionics. Talking to Carl down in NZ kind of confirmed my worries that Stark only hooks up what you tell him to. I’m figuring out what each line on each unit does and whether/where I want it connected to something else.