Repair oblong holes

I drilled out the existing subpanel a year or more ago. Let's just say my technique wasn't perfect. I'm a little better at it now, but at least one of these holes is unacceptable. These are the holes for matching the F-768 outboard subpanels to the vertical longerons (insert part number)

As you can see, the middle row left column hole is not good. The one below it isn't much better.

So as a solution, I decided to make a patch plate that will sandwich the longeron and the subpanel

The first attempt I made didn't have very good edge distance for the holes I was trying to fix. Especially since I'm going up a size to a -5 rivet. So, I made this part twice, but the second time I made it extend as far as I could. 

Here's a shot of the repair plate in position:

Avionics wiring re-do

The wiring needed to be changed since the GEA 24 moved from its original spot.

I don't have a wire stretcher handy, so the old wiring for the CAN bus had to be chopped up and replaced. It seemed easier the second time around, until I forgot that I ran out of solder splices. Fortunately, an avionics shop located on the field hooked me up. Thanks guys!

I want to get the AOA sensor installed since it works off the CAN bus, so I might as well order and install it while I have the wiring all chopped up. Other than that, not much to update other than the longer CAN wiring to the GEA, now to make room for the AOA sensor wiring when it comes in.

I noticed that the electric fuel booster pump that Vans supplies has changed. The old one that I have looks like this:

Holy shit, what a plumbing nightmare, right?

The new one looks like this:

Which one would you rather have in your plane?

I think the pumps are the same, just the manifold that connects the relief valve and filters have been optimized to reduce the number of fittings (aka potential failure/leak points). I'll see if the pump and filter can be re-used with the new setup.

Subpanel rebuild complete

Got the floating rivet nutplates installed, so now the GSU 25 ADAHRS,  GEA 24 engine monitor, and the GAD 29 IFR box are now mounted to the subpanel. Here you can see the doubler plates that were installed to hold the 2 units.

Also, got the angles installed, which act as a shelf for the radio. I'll probably end up putting more equipment up there if I need to, since there is a lot of room.

The subpanel was also re-mounted on the plane. Starting to look better with parts going on instead of off. The CAN bus wiring is too short from the GAD 29 to the GEA 24, so I have to rework that so wiring will reach the relocated GEA 24. If I had to start all over, I'd probably loose-assemble EVERYTHING and see if there are any interferences before starting the wiring. Being clever and working on it at home was very comfortable, but I didn't realize there would be clearance issues, even though I had done some rough measurements.

Supanel rebuild almost done

Today, I riveted the parts that were fabricated and primed yesterday.

The GSU 25 mounting using the Sketchup technique was the easiest one yet. I've struggled with drilling 4 holes that line up exactly with the part I'm mounting. When I can match drill, I do that, but on these avionics I don't want to use their mounting holes as drill guide bushings. Plus, the aluminum parts are about 0.025 in thick, so there is some play in them. I suspect when I clamp them down on my uneven work surface (long story, crooked hangar floor + homemade welded table..) it puts some bend into the material. Anyway, this one lined up great! I'll definitely be using this in the future.

The top right bolt is not mounted yet.. I'm waiting on some floating nutplates for that application. Oh yeah, I'm using nutplates to facilitate any maintenance. Hopefully the floating nutplate will allow me to final position the GSU perfectly square. Turns out, you can get floating nutplates with the rivet mounting holes pre-dimpled. For the GSU 25 the mounting bolts are sized 10-32, so the corresponding nutplates are  MS21059-L3K for the dimpled rivet holes and MS21059-L3 for the regular, un-dimpled rivet holes. Not the cheapest hardware at about $0.75 from Wicks aircraft, but will save some time hopefully.

The back of the subpanel also got some stiffeners.

On the other subpanel rib the doubler/doubler got riveted too.

It looks kind of funny but stiffens it up quite a bit and will do a good job of housing the GEA 24. Ran out of nutplates/time so I didn't get to install, but you get the idea. Sorry for the blurry photo, but I'm no good at selfies evidently. 

Finally, here's the subpanel kind of put back together

GSU 25 install

The GSU 25 was installed on the F-768-R outboard subpanel. Just like the GEA 24, the spot I picked for it wasn't going to work because of clearance issues. In this case, the subanel has a slight angle to it at the bottom few inches. It may have worked, but I decided to move it upwards into the 'flat' part so I would have a nice even planed surface to work with.

The GSU 25 is an accelerometer and pneumatic to electrical converter that takes the airplanes acceleration and pitot/static pressures and converts those into electrical signals. Those signals are passed with other signals, like the GMU 22 magnetometer for the compass heading, into the digital display that is then processed and displayed on a screen.

Anyway, it's important that the GSU 25 is mounted securely and "level" with the plane's axes so that you get good information on your screen. My fear was that if I left it in the original position, because of the slight angle on the bottom half of the sensor unit I could get erroneous readings... not good for a pilot.

So I used Google sketchup to model the GSU 25. I should have been doing this a long time ago because it is a good layout tool. Basically I made a template with sketchup, using the Garmin installation manual's dimensions for the GSU. Then I overlaid where the mounting holes are, and printed it 1:1 on paper so I would have a nice dimensioned piece.

Once it was positioned on the right edge, I made sure that it was square.

Finally, I taped down my paper template and used a centerpunch to punch the centerpoints of each mouting hole to the F-768-L subpanel. 

Because this is an accelerometer, it was important to make sure the mounting area was stiff enough, so I wouldn't resonate the GSU sensor and get bad readings. Some J-hat channel riveted to the back seemed to stiffen the area up nicely.

Once the parts were prepped I tried my luck with a new Harbor Freight HVLP sprayer. My first go round at it was not great, but OK for primer I guess. I'm a little heavy handed and have a tendency to spray too much. My hangar neighbor Doug is a real life airplane builder and he gave me some tips on gun setup and use. Basically, do light coats, start with the edges, and don't hold the trigger at full blast the entire time :)

No photos of that, but got the subpanel primed all one color now. 

Need to order some 10-32 nutplates to mount the GSU, but I'm getting pretty close to finishing this out.

GEA 24 doubler cntd

Not a good start to the day:

The red stuff is blood - for the first time since I took the sheet metal class, I drilled my finger. Not the smartest move but fortunately it wasn't a huge injury and it didn't mess anything up that I was working on too badly. I suppose this is karma for drilling Laura's hand about a month ago. Maybe I'm getting sloppy. 

Anyway, I had to install a doubler on the doubler to accommodate a nutplate. Kind of odd, but here it is:

You can see I only dimpled the holes that will take a nutplate, or would interfere with the GEA box sitting flush. My goal was to use 1/8 in. universal head rivets where possible. 

Tomorrow the weather is supposed to be warm so I'll prime these parts and rivet the nutplates and parts into place.

Hopefully this new location for the engine sensors will work better than the old one.

The wiring is pretty much done, I need to make the CAN bus line that runs from the GAD 29 to the GEA 24 a little longer so it can live in its new spot.

GEA 24 doubler

Just like the GAD 29, I had to install a doubler for the GEA 24 engine sensors.

These would have been more accessible on the front side of F-768, but I could not get them to fit without interference from either the canopy longeron gusset, the tip up canopy reinforcement angle, or whatever.. so it will match the other side.

The GEA 24 is a little bigger than the GAD 29, so obviously the doubler is too. I tried to minimize the size (weight) but it needed to span the lightening holes in the F-745-R rib.