Inside Front Fuselage Skins

Time: 0.5 hrs

Fit the inside front fuselage skins. It wasn’t as easy as I thought it would be. It was a very tight fit and it seemed to hand up on everything. I got a few dents in the right side… not sure how they got there since nothing is really in that area and I didn’t noticed them prior to putting in the skin.

I also receive my Tosten MS control stick grips. They look so much better then the picture on the Tosten site. I’me really happy with the and they also came prewired with pigtails so that’ll work out great. I need to wire in the connectors when I get. I’ll probably just pin the control grips since I can’t really fit them until I know how much I need to cut down the control sticks. The good news is I don’t thing the grips are going to hit the panel so no bending of the controls stick should be needed.

Front skins are clecoed in. I probably won’t rivet these for a while, I just want to get them out of the way so they don’t get damaged.

Kind of a crappy photo, but the grips look nice. They don’t look as plasticy as they did on the Tosten site and they have a good solid feel. The toggle (that I’m using for flap control) is a little stiff, but that should help prevent accidental flap actuation. There’s also a thumb button (AP Disconnect), a trigger (PTT), and a small button under the trigger which I’m planning to use for TO/GA. There’s also the 4 way hat switch which I’ll only be using the Up and Down for elevator trim

Grib on the stick. It looks like there should be enough clearance between the panel and the grip. If I have to cut the sticks back a lot then it might get close the the leather part of the panel.

Ahhhhh I thought I took a better photo. I opened up one of the grips just to see how it was wired up. Unfortunately you really can’t replace many of the buttons with your own because they are soldered onto a board. The toggle (flap) button and thumb (AP Disconnect) button could be replaced with different buttons. This is a bit of a bummer because I was thinking of changing the small index finger button with a DPST switch for the TO/GA function. Garmin calls out a DPST switch because you need to connect to a pin on the GEA24 and the GTN650 and they don’t want any interaction between the two devices. This means I will probably need to use a double pole relay that the index button will trigger instead. The other option would be to mount a button on the panel or center console somewhere. I looked at putting a button in the bolt hole in the throttle handle. It would actually work pretty well using some rubber grommets and maybe some RTV. The problem is where to do run the three wires (2 for double pole switch and a ground wire)? You can drill out the handle inside to make room, but then you’d have to run the wire down the side of the throttle lever and that doesn’t look so nice. Maybe some small conduit might work… will need to look around for ideas.

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Rivet Sanding

Time: 2 hrs

Today I just did some finish sanding on the rivets for the left, right and top of the fuselage. It goes quick so I was able to finish it all in little time. The bottom was done when I had the plane flipped over. I used a 1000 grit paper and sanded just enough to remove the scratches left by the 240 grit. The rivets will start to get a little shine to them. I didn’t want to take off any material, just enough to smooth them out… it’s actually a bit hard to do using 1000 grit paper any way, but I suppose if you sanded it long enough you’d take a bit of material off. I’m thinking I’ll start filling the rivets on the empennage next.

Waiting now on the control stick grips which I won’t really install until much later. I just want to get an idea of how much the sticks will need to be cut down and if I’ll be able to adjust the control rods enough so the grips don’t hit the panel. After looking at some of the factory photos on Craig’s site I think I have the panel it the correct spot, plus or minus an inch or two.

I also bought some of this filler from Aircraft Spruce. I figured it would come in handy for filling the remaining fuselage rivets (that I have to wait to fill) where the other epoxy resin technique won’t work and maybe on the wing tips and other areas that might need some shaping.

Instrument Panel Test Fit

Time 0.5hrs

Jean gave me an instrument panel a few weeks ago since he knows I have to buy the canopy kit :-). I thought I should see how it fit and what concerns there may be with the control sticks and control stick grips. I also fit the forward top fuselage skin which I thought would be really quick, but I had to do quite a bit of bending to the top rib flanges to get it to fit. I think a bit more bending is needed for a really good fit, but at least most of the holes line up now.

I also noticed that the control sticks are pretty close to the panel and a bit long. I had asked some other builders and a few said they had cut down the sticks a bit. It really depends on the stick grip just how much. Also I have the stick adjusted all the way forward so I think I can extend the control tube a bit and that should move the sticks back. I was originally going to use the Tosten CS8 grips but after looking at another builder’s photo of the gribs and how much they curve forward, I’m thinking they’re not going to work so well. I called Tosten and he said the MS (Military Style) curves quite a bit less and that he knew of a few Slings that had them installed. With that info I think I’ll give those a try. They’re a bit more expensive then the CS8’s and I don’t like them as much, but they can be customized with an array of buttons and other options. The MS grips have a trigger button and a small button on the front, plus a 4 way hat switch just like the CS8. You can also add thumb and palm rests with more buttons so I think I’ll add a thumb button for my AP disconnect and the small front button will be for the Go Around button.

Instrument panel and top forward fuselage skin test fit. The top skin fits very tight against the upper rib, but finally got the bottom holes close after some bending of the rib flanges.


The control sticks will need to be cut and I’m hoping that adjusting the control rods will move the stick back a little so the grips don’t hit the panel. I’ll have to wait to cut them because I don’t have the upholstery for the seats and can’t get an accurate feel for where the gribs will need to be.


This is the configuration I ordered for the Tosten MS gribs. The thumb rest button will be the AP Disconnect and the toggle switch on top will be flaps. My only concern about the flaps switch there is it may get hit by accident so I might try to find a better toggle switch. The grip comes completely apart so you can modify it as you like. The gribs are a bit expensive though, this configuration is just under $200. The right side is the opposite configuration.

Seats Finally Done

Time: .5 hrs

Just had to rivet together the two halves of one of the front seats (the other was done a while ago) and the rear seat. I’m happy these are done because I absolutely hate the Rustoleum paint I was using and the Krylon is a little different color so I couldn’t use it to finish up the seats. Anyways the seats came out OK. I might respray them with a coat of the Krylon, but I don’t know if the paint job bothers me that much. Almost all of the seat frames are covered by upholstery anyways so I won’t have to look at it every day.

Now I’ll just stow them away in plastic bags until I get the upholstery.

Well it looks OK in the photo, but the paint is a bit bumpy on the seat back… the bottom was done a while ago and actually looks pretty good (the paint gods must have been smiling on me that day). Glad I can move to just using the Krylon paint from now on.

The only downside of keeping the halves separate is that I now have an unpainted row of rivets on the rear of the seats. Pretty hard to see though. I make risk it and try to do a quick coat over them, but you never know what you’ll get with this paint. Have I mentioned how much I dislike the Rustoleum paint 🙂

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. 

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…

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.