Interior Rear Side Skins

1.5 hours

Today I got the interior rear skins ready to get riveted. I had to remove a few rivets from the rear seat floor area to get the skins to fit in. I also had to drill out a few holes for rivets. The skins fit pretty well. The only issue is that if I line up the top of the rear skins with the top of the front skins then most of the holes don’t line up so having them not even seems to work best. These will be covered with the more decorative interior panels so these will never be seen.

I noticed that the cut outs or recesses in the canopy for the seat belts don’t line up great. And since the parachute cable is right behind that area I can’t really even dremel it out more. It’s not that far off, maybe 1/4″ and the seat belt does seem to move OK, though it got a little slow retracting once while I was messing with it. I was thinking maybe the canopy isn’t far enough back (not much I can do about that now), but if that were the case then the upper hinge part of the seat belt strap would be farther back as well and so I’d have the same issue I think. It’s not that big of a deal, it would just be nice if it lined up a little better. Maybe I might need to loosen the seat belt spool and put a slight angle on it instead of it being so straight vertically. Will have to look at that.

I always thought the these flanges go in front, but I saw on the Sling at Torrance TAF that they sit behind the floor panel. Much easier to drill out as well. But now I need to remove these rivets.

OK rivets are out and had to drill one hole in the flange on the floor. On the floor I put the flange under the floor skin even though the Sling at TAF had it on top. I just think it looks better and maybe a little stronger this way.

Right skin, cleaned and clecoed. I’ll do the top row after I get all the other rivets in. Just need to rivet it when I get back from my hiking trip. I think I should be safe to install the interior skins now. I can’t think of anything else that needs to be done behind them.

And same for the left side.


Install Center Console (Cubby Hole)

Time: 1.5 hrs

Today I made the cubby hole/center console assembly a permanent resident of the plane. It’s been a long time waiting to install this piece so I’m happy it’s finally in. I also install the front seat belt buckles. I added 3 thick AN4 washers on the inside since the hole to mount the buckle is so large. The washers filled the gap well, a little bit of play in it, but much better then mounting without them. With the cubby hole mounted I was also able to install the inner seat rails.

Now I can double check that the brake lines are routed correctly and everything reaches. Next I can cut the lines at the clippers and put the -4AN ends on. I purchased some 45º fittings which look like they’ll work great.

Cubby hole and seat rails in. I will need to install the arm rest when I get that some day.

Rear cover for the cubby hole/center console. The stratus is mounted towards the bottom. This will be great for the kids and also can serve a 2 more USB chargers for the front. The Garmin GMA245R has one that I’ll need to bring up the the instrument panel with an extension, but it’s always nice to have a few more around. I’m thinking of also putting the rear LEMO plug here for the rear seat headsets.

Rear Seat Camlocs

Time: 1.0 hr

I originally installed the retaining springs for the DZUS locks that hold in the rear seat, but after a post on the Sling Builders Facebook group about using 4002 Camlocs on the cowling I decided to make everything the same and replace them with the 4002 camlocs. In my internet searching to learn a bit more on how to install the camlocs, I came across Skybolt which has some very nice 4002 compatible camlocs. The cost is a bit more then Aircraft Spruce, but they seems to be a better quality then what you get from Aircraft Spruce. The other issue was I had to order a minimum to get the ones I wanted. Since I only needed enough to do 3 anchor points I had to order a little more then I needed.

Here’s a little on what I learned about the camlocs. First there are 4 piece and 3 piece systems. Typically you use the 4 piece. The 4 pieces are the grommet, the retaining ring, the stud, and the receptacle. The 3 piece have the stud and grommet as one piece. You can get studs in different lengths which is specified by the -(number) in the part so something like 4002-14 or 4002-5. The numbering of the parts are super confusing because there are a multitude of faster types you can get like slotted, phillips, winged, etc and you can also get different materials (cad plated, stainless steel). The grommets come in basically normal width and wide width and only a few different depths. The one confusing thing for me with the grommets was that the “plus flush” are the grommets that aren’t actually flush, they don’t need to be counter sunk, that’s the “flush” grommet. To me is sounded like the “plus flush” was just better version of the “flush” grommet, but that’s not the case. The last thing I need to mention is that you can technically install these without any special tools, but its a pain in the butt and pretty much impossible to get the stud out of the grommet if you don’t have the special pliers (showing below). Same with the retaining clip. You can get the thing on, but its a pain. The tool that they make to put the retaining clip on makes it supper easy and its only around $20 from Aircraft Spruce or Skybolt (the pliers are fairly cheap as well). I haven’t purchase the retaining ring removal pliers, but maybe I will get those at some point.

So with that said I ordered some nice folding wing fasteners from Skybolt. These are the 40S47 style studs, but Skybolt calls them SK4002SFW folding wing. I like these because they sit fairly flush, but you don’t need any tools to remove them. The -9 seemed to be the perfect length. If you like them and want to use them on your Sling please let me know. I had to buy 10 and only needed 3. I will sell you them at cost which was around $8.50 or so. I also used the wider grommet which was just for aesthetics.

Parts that I ordered from Skybolt. I had also order some phillips style studs, retaining clips and flush washers from Aircraft Spruce. The pliers are for compressing the spring on the stud when inserting it into the grommet (after the grommet is installed with the retaining ring). The tool with the rubber end it the tool to install the retaining ring onto the stud.

Above is the process to installing the grommet, retaining ring and stud. I used a step drill to enlarge the hole to 15/32″ (approx. 12mm). The grommet doesn’t fit supper tight, it moves around a little in the hole, which I think is the way it is supposed to be.

I added a little more neoprene tape to the back of the rear seat so it doesn’t scratch up the luggage floor. I’m not going to install carpet on that part so it needs a little something.

The receptacle installs much like the DZUS springs using 2 counter sunk 3.2mm rivets. I did need to use a step drill to widen the original hole to 5/8″ (approx. 16mm) so that the stud and grommet fit down into the receptacle. The receptacle are the 244-16 style receptacles (from Aircraft Spruce). The -16 have the rivets spaced at 1″ as apposed the the -24 which is wider (like 1 3/8″ I think). The -16 style line up perfectly with the mounting holes for the DZUS springs so those holes can be reused.

Everything installed. The wings on the studs fold down so the sit fairly flush. Its super easy to take out the rear seat, just fold the wing up and twist 1/4 turn.

Now the big question is what was TAF’s intention for the hole towards the from of the rear seat and bracket with the 2 holes on the rear spar? The hole in the seat appears to lend it self to installing the stud side of a DZUS connector, but the bracket doesn’t look like it would get the spring installed. The Sling 4’s I saw at TAF didn’t have anything installed here, just the 3 on the rear portion of the seat. So probably not important, just more curious then anything. I was thinking I could maybe make a sliding latch here so that when you install the seat it would slide down into the latch and then you use the 3 camlocs to loc it in place. the purpose of the slide latch would just be to keep the front of teh seat from lifting up.

Miscellaneous Work

Time 1.0 hr

Wow I was looking at the app I use to log my build time and I last worked on the plane mid June. Time sure does fly 🙂 I’m really at the point that I just need to put down the cash and buy the engine. I don’t want to do any avionics until the engine is on and once the engine is mounted I can fit the cowling and get the plane painted (well I have to build the wings too). So I think I really need to make that commitment if I want to keep moving forward on the build.

Today I just did a few random things on the plane:

  • Installed the top mounts for the front seat belts
  • Fixed the switch/knob plate for the cabinet lights
  • Installed neoprene foam on back seat and ribs
  • Looked at where to put ELT antenna

I’m thinking it’s OK to go ahead and install the seat belts. It wasn’t as easy as just tightening the bolt of course. I noticed that the provided washer was a bit thin and the top holder would bind against the canopy. I ended up adding 3 AN7 washers which moved it out just enough so the holder was able to move freely. I also made sure to use some loctite on the bolts. I torqued them to 30ft/lbs. which is a little shy of what you would torque an AN7 bolt to, but since the nut is just epoxied into the canopy I didn’t want to over do it and rip the nut out. These are metric and different material, but it seemed about right.

Added 3 AN7 washers to offset the seat belt holder so it could rotate with the seat belt.

Installed the plastic cap. I hope I don’t have to remove these for anything.

I’m thinking this may be a good place for the ELT antenna. TAF mounts it on the front side on that rib in the photo, but I noticed that it’s a little in the way of someone sitting in the rear seat so it would be good to get it out of the way.

NOTE (7/8/2018): After some thought and a few comments from others I decided that this probably isn’t the best location for the ELT antenna because it does move it back into the metal portion of the cabin. For now I’m going to stick with the TAF location unless I think of a better place.

I had previously purchased some thin neoprene foam tape for the luggage door, but it was a bit too thin. I knew I’d find somewhere to use it. I installed it on the inside edge of the rear seat. I’m not going to put carpet on the luggage floor so hopefully this will keep it from getting scratched. I also put some on the ribs where the seat sits on some rivets there. I was going to install the cam locks that hold the seat to the luggage floor, but I only purchased the flush mount collars for the cowling. I ordered a few of the “plus flush” (4002-NS)  ones which are the ones that don’t need dimpling or countersinking.

Miscellaneous Work

Time: 3.5 hrs

More random stuff done on the plane:

  • Drilled extra holes in parachute skin and cut out edges as per other holes. Drilled holes in fuselage for new parachute skin holes
  • Installed vertical stabilizer covers
  • Messed around with remaining parts for canopy (door gas strut, various screws, etc.)
  • Temporary install of cabin heat and choke cables (need to be cut)
  • Messed around with mock up instrument panel and GTN650 fitting

I added 3 more rivets on the front of the parachute skin and two in the back near the antenna. Also had to cut the notches so the skin can slide out under the rivets when teh parachute is deployed.

Fits much better now

And also in the back

I saw on Peter C’s build log that he installed these (RF-SKN-008-C-A-0) so I dug them out of the box and installed them as well. One less part to have lying around and having to figure out where it goes.

To install the cover skins you have to remove two rivets and install M3 rivnuts.

The cover skins attach with M3 screws. These will need to be removed when the empennage goes on, but for now I’ll just leave them here. I’ll also need to prime the inside when I do the wings (and have the primer spray out).

I temporarily installed the choke and cabin heater cables. These aren’t supplied by TAF so they will need to be cut to size. I was hoping that I could install these before the instrument panel gets installed because I have to tighten a nut on the inside of the firewall where the bulkhead fitting goes through, but the cables are designed to be fed through the front of the panel so change in plans.

I cut a block of foam to the size of the GTN650 including the connectors (11.27″ deep) and glued it to the back of my mock up panel (which is actually fairly accurate to size). This is an old mock up, quite a few things have changed, but it will still work for this purpose.

Well someday it will look like this for real, but until then I have the paper version 🙂 I looked behind the panel and it seems like there is about 2-3″ of space between the back of the foam (fake GTN650) and the rib so with wires attached there’s not much space behind the GTN650 for anything to be mounted on the rib.

Parachute Skin

Time 2.5 hrs

Today I drilled the holes to mount the parachute skin. This will be riveted later after the plane is painted and is riveted with a small removable spacer so that the panel can be more easily removed as the rocket flies through it and deploys the chute. Like everything on the plane I figured this would be fairly quick, but even after being careful to hold down the skin as the holes were drilled I still ended up with a few spots (in front) where the skin doesn’t sit down tight enough to the other fuselage skin. I figured that putting an edge on the skin might help, but this only helped a little. I ended up unriveting the galvanized plate inside and bending it to fit the shape of the fuselage I also notched the plate to fit better into the channel where the rocket will sit so that the skin would sit more flush. This helped the most and the skin fits much better now. However after looking at a factory photo from Craig M’s site I notice that TAF added a few more rivets in the problem spot so I guess I’ll  do the same to get a bit better fit.

Lots of tape to make sure the skin was sitting flat on the fuselage. It took some time to make sure it was positioned correctly. I mainly used the forward edge as a guide to make sure it was straight with the canopy to fuselage seem.

All the holes drilled and the skin checked down. At this point I thought I was done, until I saw this….

Ahhh WTF the skin doesn’t sit flush on the fuselage and since it’s the leading edge it would be good if if sat nice and flat. I know that the rivets will be a bit more relaxed then how the clecos are holding it down now, but since I don’t think that’s going to easy the gap that much. Also I don’t know if any kind of sealant is used when the skin is installed, even if the the fit was pretty tight I would image water would still get in. I guess I’ll have to find out.

To get a better fit I decided to use the edging tool to put a bevel on the edge. This actually didn’t help as much as I hoped. Next I removing the galvanized reinforcing plate so that I could do some work to it. It’s a pretty stiff piece of metal so making that fit better should help the fitment of the skin.

I added in a slight bend to the plate and also notched the edge so it fit down into the rocket channel better.

Well that’s quite a bit better. There’s one spot on the front that still isn’t great and also on the back near the antenna. I saw from the factory photo though that TAF added in a few extra rivets. So I will probably do the same.

Here’s the factory photo taken from Craig M’s site that I was referring to. You can see about 2 extra rivets added to the front and a rivet in the back near the antenna. Also it looks like they beveled the skin as well so I guess I was on to something there 🙂


Miscellaneous Work

Time: 1.25hrs

I felt like I needed to do something on the plane so I did a few little things to make me feel better.

First thing was I installed a connector for the ELT buzzer. I previously put some leads off the 15 pin connector that connects to the ELT. I found a locking 2 position connector that uses the same Mini Universal Mate-N-Lok pins I have been using.

Next  I ran the throttle cables through the firewall bushings. I didn’t tighten them down yet since I’m not sure long far they need to extend out from the firewall. These are from TAF so I know they don’t need to be cut. My other cables for the choke and heater will need to be cut since those were just purchased online.

Lastly I messed around with the placement of some of the avionics components. I mocked up a few of this using foam block. I also simulated the connectors so that I could see the spacing needed. I think the arrangement will work. I found some Garmin tray mounts that I will try to use for the GMA245R (Audio Panel) and the GTR20 (Comm). I will just stack them on the left side using some aluminum angle. The GTX45R (Transponder) will be similar but on the right side and will use the mount that comes with it. I saw that SteinaIr mounted the GSD29 on the side of the GTN650 mount on Craig M’s panel and I think that’s a good idea since it mainly connects to the GTN650. Also I may mount the GSU25 (ADHRS) on the back of the GDU460 but I’ll have to see if the panel is rigid enough. If not I can mount it where I have it speced out.

The connector is done for the ELT Buzzer. I’ll have to zip tie it a bit once it’s all connected.

Throttle cable through the firewall. Nothing exciting.

Preliminary placement of avionics. I also need to check the spacing on the GTN650 to the rib. From what Craig M. was saying there’s only about an inch of clearance to the rib after the connectors from the back of the GTN650. I left about 4″ either side of center so it will probably work (the GTN650 is only 6″ wide). I can always adjust it when I do the actual install. I don’t have any of these avionics yet and I think I will hold off a little longer until I have the engine on. That’s going to be the next step I need to do anyways.