Brake Resevoir

Time: 0.75hrs

Installed a -4AN connector on the brake line that connects to the brake resevoir. I also torqued the other AN fittings on the Y splitter and marked them with some torque seal just so I know that I torqued them


Brake reservoir with -4AN to NPT fitting. 


From the Y fittings that feeds to both the left and right brake pedals. I just put a dot of torque seal so I know these are torqued. 

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GMU11 Part 2

Time: 3 hrs

Things done today:

  • Removed old cabling for GMU22
  • Ran new #22-3 between GMU11 location and instrument panel
  • Ran CANbus cable between GMU11 and pitch servo
  • De-pinned CANbus pins from pitch servo connector
  • Pinned and installed 9 pin connector for GMU11

Today I did some prep work for the GMU11 even though I don’t have the new mount yet. The factory said they should be shipping them by the end of the week and sent me a drawing of where it will be mounted.

TAF photo of the new GMU11 mount and location in the rear fuselage. It should be doable from the access hole in the bottom.

I ran the power and CANbus wire for the GMU up the left center longeron. I probably would have picked a different route if I had more access to run the wire. I think this was the  best way for my situation since I can get to most of the longeron to drill and install cable ties. The cable splits here near the pitch servo. The #22-3 (power1&2 and ground) go to the instrument panel and the CANbus wire runs to the pitch servo connector to tie into the CANbus there. I ran a single bundle back from here to the GMU. I used a multicore wire wire for the power and ground rather then single wires just because the Garmin manual said to do this to cut down on any EMF.

Note (9-3-2017): Just realized that I should have used #20-3 wire since I’m tying this into a 5A breaker. Well the device isn’t going to pull nearly enough to heat up the wires (it only pulls 0.1A), but the wire would technically fry before the breaker pops. So I think I may move it to a smaller breaker (it was on a breaker shared by other Garmin stuff) and then it should be fine. Also it’s really hard to find #20-3 cabling so I probably would have had to use #18 which is really overkill.

The one problem with this route is the wire gets a bit close to the pitch servo. The tie in the upper right of the photo helps keep it away from the servo. I didn’t shrink the heat shrink here yet because I may have to adjust the split point a bit once I get the GMu installed. I wanted to leave enough cable on the GMU side so I could put the connector on.


Cables on the GMU side with pins and labels.


Connector almost done. I put silicon tape where the cable strain relief is to protect the wire and add some resistance. One important note is that the metal bar part of the restraining clamp has the raised part facing away from the wire. If you flip it over then it can eventually damage the wire.


All done, just need to get a stainless steel 8-32 screw and lock washer to attach the shield of the CANbus. I didn’t put a drain wire on the other multicore wire because you really should only connect the shield at one end of a shielded cable to minimize ground loop issues. The CANbus is one except to that rule. It would probably be OK to ground the shield for the other wire, but just keeping consistent. Also the terminator will be installed here as well since this will be the end of the CANbus. The GMU11 uses an external adapter for termination rather then a jumper.

NOTE: The ring terminal is a Raychem B-106-1401, I believe I ordered it from Mouser Electronics. It’s nice because it’s a crimp connector, but also is heatshinkable. This saves a step of crimping the connector and then adding heatshrink over the end of the connector.

Now just need to wait for the new mount and get that riveted in.

TO BE CONTINUED…

GMU Mounting Part 1

Time: .75hrs

Drilled holes and installed M4 rivnuts in GMU mounting bracket. The mounting bracket from TAF is for the GMU22, but Garmin has released a new version of the GMU, GMU11 which is about half the price of the GMU22. The GMU11 is also standard if you buy the G3X package while the GMU22 come with the high performance package (which also has the ADHRS for faster aircraft). I decided to use rivnuts because I’m going to move the bracket as far back under the luggage area as possible which will mean is going to be a pain to get to it so I wanted to make mounting it as easy as possible. I’ll prewire the connector when I get the connector kit from Spruce (it was back ordered). So next is to drill and rivet the bracket under the luggage floor, wire the connector and then mount the GMU.


M4 rivnuts just fit.

NOTE (8/26/2017): I believe the rivnuts are carbon steel which is a ferromagnetic metal so if I plan to mount the GMU this way I’ll need to replace these with type 300 stainless steel rivnuts. Type 400 stainless steel is also ferromagnetic so they need to be type 300.


Fits nice onto the bracket and it’s straight. I’ll have to make sure the bracket gets installed straight and level as well. A few degrees off will increase errors in turns, etc.

Note (8/26/2017): After speaking with Craig (another Sling 4 builder) I’m thinking of moving the GMU to the rear fuselage near the bottom access panel. TAF is supposedly making a new bracket for the GMU11 for mounting further back in the rear fuselage. The real challenge will be running and securing the cabling with limited access.

To Be Continued…

Nose Wheel Spat Finished

Time 1.25 hrs

Things done today:

  • Filled in unused holes in nose wheel spat (factory pilot hole for mounting)
  • Cut top of nose wheel spat flush
  • Drilled holes for tow bar
  • Connected and torque rudder pedal to nose wheel push rods

The forward part of the nose wheel spat is a little longer then the rear so I cut it flush with the rear and sanded it to finish the edge. The front part of my nose wheel spat sits about 15mm from the strut. The manual says 5mm, but it looks like the spat sits at a good angle and clearance to the front tire is good as well. Also the forward holes that screw into the mount were very close to the factory ones so I think it’s in a good spot. Also I checked the new manual and it doesn’t say anything about putting rivnuts into the nose wheel strut, but he old manual does so it’s possible that it’s not needed. I’ll have to check with the factory though.

Drilled the hole for the tow bar. That was kind of a paint in the butt. I measured the spacing from the rivnut to the center of the hole and then eyeballed the angle. Then I drilled a 1/16″ pilot hole and put a piece of wire in it and felt around the back to see where the wire came through the hole. I had to move the pilot hole back about 1/16″ or so. Then I drill a bit larger hole and then filed it out until I could see the edges of the tow bar hole. I then finished it using a step reamer to 3/8″. I’m going to consider the wheel spats done. The only thing left to do on them is to install the blond grommets for the air valve. I don’t have them so I need to find them online. Once I get them I’ll know exactly the size hole to drill.

This went quick. I just had to connect and torque up the AN5 bolts that connect the rudder pedals to the nose wheel. It’s steerable in the Sling. I also put some lithium grease on the rose joints (saw that at TAF).

Miscellaneous Work

Time: 1 hr

Nothing exciting done today so no photos. I had been talking to another builder about the placement of the GMU. The manual puts it under the luggage area, but both the Garmin GMU22 and GMU11 specify a 10ft clearance from any motors. Well the pitch servo is only about 3ft away. I knew this but figured TAF had tested this… and they probably did with the GMU22. The Sling 4 at Torrance is all Garmin with an autopilot and the GMU is mounted under the luggage area and there’s no issue. The only difference is I’ll be using the newer GMU11 and not the GMU22. They both have the same distance requirements but it’s never been tested in that area. The builder I spoke with can and probably will move thiers further back in the rear fuselage. This isn’t so easy for me because my rear fuselage is already closed up. Mounting the GMU wouldn’t be too much of an issue, the problem is running the cable with limited access. So after looking and thinking a bit here’s my plan. I’ll remove the GMU mounting bracket so that I can more easily drill the new mounting holes. Then I’ll mount it back under the luggage area, but as far back as possible. I can get another 2ft or so clearance from the servo… anything will help. I also need to rewire a bit because the new GMU uses CAN bus. I’ll split off the pitch server for the CAN and make sure to use a terminator on the GMU since it will now be last in the change. And then I’ll just hope for the best. If there is a problem I can mount it in the wing or move it further back in the fuselage and deal with trying to run the cables at that time. 

I also installed the BNC ends for the Com1 and 2 antennas. I still need to purchase those. And lastly I messed around with some of the AN fittings on the parking brake lever and installed an AN fitting on the brake reservoir. 

Oh yeah I almost forgot to mention. I disassembled the throttle section so I could take the mounting plate to see if I can get it made up in Carbon Fiber. I’d also like to do the instrument panel and the guy said they can do all the instrument cut outs once I have that figured out.

Wheel Spats and Luggage Door

Time: 3.5hrs

Spent some time fitting the main and nose wheel spats on. I started with the main wheel spats. At first I was thinking that this was not going to work. They seemed so far off and parts were rubbing on the tires. I trimmed about 1/8″ or less from the top of the outer wheel cover. Things seemed to fit a bit better. I marked the top of the rear part of the cover (the part that bolts onto the gear) so that it lined up with the top of the front and cut that. The fit was even better. A little more light cutting and then a final sanding ended up with a pretty good fit.


A few photos of the fitment of the left spat. I’m pretty happy with it. Still need to cut the holes for air filling. 

I ended up glueing the washer to the inside of the spat since it was nearly impossible to get it to go on. 


One more look from the front


On to the nose wheel. Glad I didn’t use the factory provided holes as they were a little off. I ended up sharpening a M5 screw and screwed it into the hole then lined up the cover and hitting it with a mallet. This leaves a mark on the inside of the spat so you know where to drill the hole. 


Almost done. I still need to cut the top even and I believe the manual says to install two rivnuts at the top into the nose wheel strut. 


All spats on. Looking good 🙂

I also added some think neoprene foam to the luggage door. I had previously installed some neoprene rubber and it wasn’t really thick enough. Also it was kind of sticky so the luggage door would stick when you tried to open it. I just added the foam over the rubber and now it seems to seal up fairly well. 


The rest of the door will get covered with carpeting. 

ADS-B Antenna

Time: 1 hr

Drilled the 1/2″ hole and mounted the ADS-B antenna. Actually it’s not really installed. I need to get a washer in place of the name plate since the name plate won’t fit in the hole in the floor. In any case the antenna will have to be removed for painting so I don’t want to tighten it down.

I also replaces one of the pieces of soundproofing near the nut of the main gear bolts. It got mauled up pretty bad when I was putting in the gear bolts. I probably should have put something to protect it from the socket wrench… well it wasn’t to hard to remove and cut a new piece.

The ADS-B antenna mounted in the front fuselage skin. I used the RAMI AV-22.

A photo of the inside. I guess I’ll just double sticky the placard (name plate) there.