Dave’s RV-7A Building Log

I had some scrap .040 laying around that already had a 90 degree angle (from the old cabin frame support). I used that to secure the back of the GNS430 tray to the subpanel. I would have liked to secure the SL-40 as well, but none of the mounting holes lined up. I also cut some straps out of .063 to hold the middle of the stack in place. That will sandwich the other units around the GNS430 and should hold everything in place nicely. The angles at the back of the GNS430 also stabilize the subpanel quite a bit. Another nice side effect is that the whole panel is much sturdier. I’ve been debating about how to re-locate the ribs between the panel and subpanel, but am now thinking I may be able ditch them altogether. I’m going to leave them out for now and re-evaluate once the AFS units are installed.

I also finished fabricating the mount for the throttle quadrant. I put a slight bend in the angles at the back to match the subpanel rake and drilled holes for rivets to the subpanel and AN3 bolts to the quadrant mount angles.

I had to trim the hat section that holds the canopy release mechanism a little more. I think it’s still going to be workable. I should even be able to put the release handle above the avionics. I know lots of people leave it out, but I’m going to try to keep it if at all possible.

Good progress this weekend. I just need to prime some parts and I can rivet together the whole structure.

Went down to BFI to do my BFR (biannual flight review). We got the ground part done, but the clouds were too low for the flying we needed to do. Had to re-schedule the flight part.

Carefully marked and cut the subpanel where the avionics need to stick through.

Drilling the avionics trays to the mounting angles is a slow process. I did a lot of measuring and careful alignment. I used some .063 under the bottom tray for two purposes. First, the Garmin transponder has a cam at the bottom of the unit for securing it in the tray. If you mount the tray too close to the bottom of the opening, it’ll be tough to insert and remove. I also wanted to make sure there was no visible gap at the top of the stack.

Some people recess the trays so the bezels of the units don’t stick out so far. I went with the standard mounting. I made the front edge of the tray flush with the surface of the panel. I marked and drilled the trays one at a time, but I probably could have done them all at the same time. I drilled to #40 and then to #28 for #6 screws.

It looks like two of the trays use countersunk screws and two use pan head. Crazy. I temporarily installed countersunk screws in all of them just to test the fit. The SL40 fit great with one #6L washer on each side. There’s some slop in the PMA-8000B mount, but I’ll nail that down once I get the GNS-430 GPS. The stack looks really good. Now to cut the subpanel…

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 pre-drilled the side angles for some rivets that will hold it to the panel. I found a combination of wood that would hold the trays at the perfect height to match the opening. The vertical dimension of the opening actually looks pretty good now. I drew some guide lines on the back of the panel and used that to center the trays and clamped the angles into place. I did lots of measuring to make sure everything was even and right where I wanted it. All of the trays except the SL40 are snug, as expected. I’ll have to use some thin washers for the SL40. I’ll sleep on it and drill the angles to the panel tomorrow.

I started looking more seriously at how to mount the avionics to the panel. The cutout Ross made in the panel is 6.25″ wide. The bezels on most of the avionics are 6.30″. The exceptions are the PMA 8000B audio panel which seems to be 6.33″ and the SL-40 radio which is about 6.27″. Also, the SL-40 does not leave a gap between the bezel and tray. The cutout must be at least 6.27″ wide for it to fit. So I spent the better part of an hour filing the edges of the avionics cut out. I’d like to actually have only half of the bezel stick out, but I’d have to make the whole cutout 6.33″ to fit the audio panel. That would leave a bit of a gap around all the other avionics.

The PMA tray is strange. Instead of securing the instrument via a cam at the bottom front like the Garmin units, it uses a weird screw/nutplate arrangement at the back. That would be fine except the tray is pretty loose at the front. I’m going to have to stick some UHMW tape in there or something to keep it from flopping around. (Edit 9/14/06: Mark from PS Engineering contacted me. Since the PMA8000B is plug and play replaceable with the GMA340, they have the exact same mount. I don’t have any doubt that the mount will be secure once everything is permanently installed. It’s just odd that Garmin hasn’t tried to standardize their equipment over time. I guess it’s an artifact of them buying up other products.)

I propped up the avionics at the back and did a dry fit in the panel. Looks like there’s a bit of a gap top to bottom. I’ll try to put most of that at the bottom where it’s less visible. I installed a couple switches under the avionics to make sure they were still accessible–no problem.

I cut a couple of lengths of 3/4″x3/4″x.063 angle to the height of the opening plus 1/4″. Now I just need to figure out how to hold the avionics in place so I can drill them to the panel. Mounting the trays to the panel is definitely not a plug-and-play process.

Between the Tour de France (kudos to Floyd) and the mid-80 temps in the garage, productivity has been very low lately. Both seem to be done, so hopefully I can crank on the plane again.

Some of the avionics arrived today. The autopilot is shipping direct from Trutrak, which I’ve read has been slow about filling orders lately. I also waited to order the GNS-430 GPS. Garmin, as expected, announced their WAAS-capable version of the 430 on Sunday. It’s only about a grand more than the old non-WAAS model, so I’ll get that for sure. Should be available in the Fall.

What did arrive was the GTX-327 transponder, SL-40 back-up radio, PMA 8000B audio panel, a tray for the GNS-430, and a mess of wires. The wiring looks to be pretty close to correct. For some reason Stark wired the ARCIN IN A and IN B together rather than the ARINC IN A and OUT A. That would have made more sense. I might have to snip and crimp a few things. Overall the harness looks good.

I spent some time looking at the harness, messing around with the trays, testing the fit in the panel, etc. The cutout that Ross made in the panel for the avionics is actually not wide enough for the trays or bezels to fit through. I’m not sure if that’s correct or not. Seems like it will work OK for the audio panel and transponder. There’s a bit of a gap between the bezel and tray that will hold the panel quite nicely. The SL-40 however doesn’t have a gap. This will take some head scratching to figure out.

I also received my order from Vans containing some miscellaneous hardware I needed, and some .040 sheet I’m going to use as a shelf for the fuse blocks and other modules. A lot of builders attach these to the subpanel or ribs, but they’ll be much easier to reach through the access hatches on the shelf. Thanks to JimP for that idea.

The good part is that I can move forward with a lot of stuff now. Many things were waiting on the avionics to arrive.

It’s been way too hot around here. Friday was a record temp for Seattle, over 95 degrees. It’s just been too hot to work much in the garage. Today I did go out for a while and finish the segment of the fuel line from the pump to the firewall. A little tweaking here and there and it fits great.

I also started working on fitting stuff in the panel. The cutouts for the CO detector and ELT remote were very tight. I filed them a bit until the fit was better. I was going to drill the mounting holes (not sure why Ross didn’t do this part), but discovered I didn’t have the right site drill bit. I need a #33 drill bit for the #4 screw holes. Then I noticed everything that gets mounted to the panel seems to need a different size screw. I made a complete list of all the hardware I’ll need to mount everything. Looks like I’ll be placing another order with Spruce soon.

I realized a while back that I never finished the fuel lines. There’s still a chunk missing from the the Airflow Performance boost pump to the firewall. It’s a fairly tricky line as it has to do an extended 180 degree turn under the pump and then another 90 up to the firewall fitting. I wish I had done this one when I was doing the others. I’m a bit out of practice. However, at the time I didn’t know exactly where the firewall fitting was going to end up.

I made an initial stab at the line and almost messed it up right off the bat. I’m not sure how, but the 180 degree bend ended up too wide. That mistake actually turned out well as I just tilted the line a bit and it lined up with the firewall fitting even better. My old nemesis eventually bit me in the end. I flared the tube without putting on the nut and sleeve. Dang it. Cutting off the flare left too little left to redo the flare. Luckily I had just enough extra line for a second attempt. I know I bought a bunch of extra 3/8″ aluminum soft tubing a while back, but I’m getting down to the end of it. I started making a replacement. It was just so nice outside that I didn’t get much further. Went on a walk to the store for ice cream with the family and chatted with some neighbors until fairly late.

It’s almost impossible to work the pop rivet dimpler on the bottom of a completed fuselage. I talked Adele into helping me out, which made it go very quickly. The mounts are now ready for riveting, which hopefully Julie will help with this weekend. It’s great to have the family help out with the project.

I also made some labels for the ignition wires. I cut some 3/8″ white shrink wrap into little chunks for labeling each end of each wire. Maybe it’s overkill, but wiring the engine up correctly is pretty important.