Dave’s RV-7A Building Log

A local RV-6A builder, Dave Burton, stopped by with a 2″ Greenlee punch. He read on my site that I was having trouble cutting the holes with a hole saw, so he offered to help. The punch worked great. It’s definitely the easiest way to cut a hole in sheet metal. It would be nice to have a set of punches, but I wouldn’t get enough use out of them for the cost. Luckily, I was outbid on the punch I tried to buy on Ebay. It was for 2″ conduit, so it ended up making a hole larger than 2″. Dave said some of the punches are labeled for a conduit size and some are labeled for the cutout size. I think for the few small wiring and firewall holes I still need to make, a Unibit will work fine.

Anyway, we punched the hole in the firewall for the cabin heat very easily. After that, we finished up the lightening holes in the battery box. Well, I actually just did lightening holes on the front side. The small weight savings wasn’t worth the hassle of cutting the holes on the back. I just wanted to finish up the front so that it looked symmetrical.

Reading through some old messages from the Yahoo Group email list, I found some advice on wiring sizing. Read AC 43-13. There’s a whole chapter in there on wire sizing with tables and graphs. You can really go crazy with calculating the wire size if you want. The main point is to make the wire big enough so that 1) the wire won’t burn up before the fuse blows during a short circuit, and 2) the voltage drop in the wire is kept to a minimum. I’m still reading through the chapter, but I’ll summarize it when I get it figured out.

Also, the stick grips I ordered from Michael Lewis showed up, only a week after I ordered them! He doesn’t have a web site, but will send you information via email (michael at kalama dotcom). The grips looks awesome. You can completely customize the sticks, left-handed, right-handed, ambidextrous, any number of switches up to 5, etc. I ordered both grips ambidextrous. They don’t have the cool finger contours, but they are comfortable for either hand. The pilot’s grip has a trim coolie hat, push-to-talk button, and frequency flip-flop button. The co-pilot gets nothin’. It’s too much hassle to wire anything in the co-pilot stick since it’s removable. I’m still debating about whether I want to stick (sorry about the pun) with the ambidextrous grip for the pilot or go with a left-handed grip. The only drawback with the ambi is that the PTT button is on the top of the grip instead of under the index finger. When I fly the Cessnas, I always fly with my left hand. And I’m used to having the PTT button under my index finger. Hmmm, decisions, decisions.

I re-worked my electrical plan, identifying how I wanted to route wires through the fuselage. Most wires will travel up through the central tunnel and through the middle holes in F-704. Wiring from the wing will enter the side of the fuselage just aft of the pushtube openings and go through the outermost holes in F-704. By locating the strobe power supply under the pilot-side baggage floor, most of the wires from the tail (elevator trim servo, tail strobe) will go under the floor to the left of the tunnel.

It’s all working out very well. The only unknown is whether there’s enough room in the F-704 holes for all of the wiring going up to the panel.

I also started to work on sizing some of the wiring. I’m still rather confused on how exactly to pick the wire size. House wiring is so much easier, 14 for lights, 12 for outlets, etc.

I decided to install the rudder cables, at least up to the baggage compartment. I’m not sure why I put this off so long. It’s cool having them in place.

I also worked on positioning the rudder cable fairings I made a few days ago (or was that yesterday…). I drilled them to the fuselage, dimpled, and then realized I don’t have enough MK-319-BS rivets. There just isn’t good enough access to use solid rivets, so I’ll order more of the MK’s.

With the canopy set aside for the time being, I started doing a bunch of miscellaneous stuff.

Julie helped me rivet the nutplates to the firewall for the contactors. I had to trim the tab on the master contactor just a tiny bit to get them to fit.

While Julie was in the riveting mood, she also rolled under the fuselage on the creeper and shot the 4 rivets holding in the bellcrank support. Those rivets have been waiting a long time, mainly because I kept forgetting about them. Thanks Jules.

I also made some rudder fairings following Sam’s directions. They turned out pretty good for 20 minutes worth of work.

Going back to the canopy directions, I realized I didn’t attach the handle. I already fabricated the whole thing, except for drilling the hole for the cotter pin at the top. Unfortunately, the screws called out by Van’s were a tiny bit short. I’ll order one size longer and install those instead.

I then started to contemplate wiring. I decided I really needed a plan. I sat down with pencil and paper and drew out a schematic and then a wiring plan for the fuselage. It was a fun exercise, but took literally hours to do. I used info from Aeroelectric, Van’s sample wiring diagram, and various other diagrams that I’ve printed along the way.

I stopped by Sears at lunch time to pick up a mandrel for the funky hole saw, but the check-out line was moving verrrry slowly. And the mandrel is $20. And I’d rather use a punch anyway. I checked out Spruce for Greenlee punches–$100 each, ouch! I looked on Ebay and found a “2 inch punch” for $6. I bid on it and later found out the punch is actually intended for a 2″ conduit and produces a 2-3/8″ hole. Bummer. A -6 builder in the area emailed me and said he might be able to borrow a punch from work. That would be excellent, since I really only need the punch for a few minutes.

A neighbor stopped by with his son and daughter to check on the plane progress. His 6 year old son was totally into the plane, asking all sorts of questions and asking if he could have a ride when it’s finished. Nothing like a little youthful enthusiasm to re-energize me on the project. The fuselage is kind of a mess with tools and aluminum chips everywhere. After they left, I did some clean up in there. I’m sure I’ll create more chips, but it’s nice to get the thing vacuumed out.

I mounted my fabricated ELT frame to the baggage ribs with some LP4-3 pop rivets. The access wasn’t great, but I got it in there. The ELT rattles a tiny bit in its mount, so I might shim it a bit. Otherwise, it looks great.

I started to think about how I want to run the wire for the ELT remote panel. A few builders have said they don’t like running wires up the central tunnel and through the center spar because of possible interference with the pitch/roll control mechanism. (After re-reading Dan’s log, the problem is actually with the wiring holes right at the front edge of the rib–not the tunnel.) I decided to mount the control sticks to see exactly how much space they occupy.

It took a while to get the bolts and washers into the very tight spaces. I used the digital level to sort of align the two sticks to each other while installing the lower connecting rod. It’s cool to have the sticks in there again. Of course after I got everything perfectly aligned, I realized I’ll have to remove the pilot stick to drill a hole for wiring.

I picked up a new 2″ hole saw at Sears, since the old one is just not able to cut through the steel battery box. Wouldn’t you know it has a different type of mandrel. Frustrating.

Instead I laid out the rest of the holes that need to go through the firewall. There’s the cabin heat, fuel line, throttle, mixture, prop control, and some sort of line for the manifold pressure sensor. Using the dimensions from the plans in Van’s firewall forward kit, I carefully marked the location for each hole on the firewall. I’m going to do a little more online research before I actually drill the holes.

Another thing I did was to wash the canopy frame. I need to spray some touch up interior paint on the inside, and I picked up some “ultra-flat” black Krylon paint for the glare shield. The easiest way to prep for painting it to just wash down the frame outside with Dawn and rinse really well.

The last thing I did for the day was to drill the ELT mount to the baggage ribs and debur. I was putting off doing that until I was absolutely certain that’s where I wanted it. I was 99% sure, so I drilled it. This project would go so much faster if I didn’t have to double and triple think about every little detail. However, it’s easier to think about something three times than to do it wrong and have to fix it.

I’m skipping around a bit, mainly because the other parts are all waiting for something. I decided to work on mounting the battery box and contactors to the firewall. There are a few rivets that need to be drilled out of the firewall and then enlarged for AN4 bolts. You have to be very careful because some of the drilled out rivets become the bolt hole, but some are just a rivet hole for a nutplate. Drilling through the stainless firewall is not fun. This part would definitely be much easier to do before the firewall is assembled.

I managed to do all of the drilling, dimpling and countersinking. Now I just need Julie to help me buck the rivets to attach the nutplates.

I pulled out the parts for the battery box and started working on them. I almost immediately screwed up the battery tie-down bar by drilling the lightening holes too close together. I added a new one to my “order from Vans” list.

I then drilled the side angles to the battery box, using a piece of .020 under the right hand side to simulate the firewall recess, per the note on the plans. I deburred the holes (never fun with steel) and dimpled the holes for flush head rivets on the inside.

I started to cut the lightening holes in the battery box with a hole saw, but it quickly dulled. I need to get a better hole saw. It’s quite a mess. I’m now wishing I hadn’t bothered with the lightening holes.

I started off by using the spacers I made to pop-rivet down the canopy skin to the aft tube of the frame at the outboard ends. 3 of the spacers on each side worked great, but the 4th wasn’t thick enough. Back to the band saw. I made two new spacers (one for each side) out of .250 material, thinning it down to 3/16″, and then painting.

Julie helped me heft the bubble back onto the frame to mark the outline on the front skin. I’ll paint a flat black inside that line for the glare shield.

I also worked on assembling the parts I made for the ELT mount. I used countersunk rivets to attach the frame to the stringers at the front and back, and also to attach the clamp band to the frame. I then riveted the angles at each end of the stringers. Making this mount has been a pain, but it’s going to work out great.

After consulting the “ELT mount” thread in the VansAirForce Forum, I decided on a different approach for the ELT mount. Instead, I’m going to use some simple angles stretching between the baggage ribs like Jeff (a.k.a. RV_7A) did. I thought about mounting it to the back side of the cover like Mike Shipper, but was worried that it wouldn’t be sturdy enough. I guess I didn’t take a picture, but I will when it’s done.

I also spent a ridiculous amount of time fabricating these stupid little spacers for the front of the canopy frame.

And most significantly, I riveted the reinforcement pieces into the canopy frame and riveted on the aft part of the frame. I left a few rivets for later when Julie can help again. This thing feels much more solid now.

One last thing I almost forgot. I bought some West Systems resin and hardener during the week. I played around with that stuff a little. Julie asked me to fix a tile that fell off the fireplace surround. Well, I think I’ll just use some marine epoxy on that!!