Fuel Tank Jigs

I spent a few hours today building the jigs for the fuel tanks. I’m still waiting on the left fuel tank skin from TAF so I can’t build the tanks yet, but I should be able to get started with assembling a the fuel level and drain components on the ribs. I’ve been contemplating alodining all the fuel tank parts since some will not be primed (the surfaces that are expose to fuel). I will probably spray the other su5faces with primer after the tanks are assembled. So I’m wondering if it’s really worth the effort.

I’m also having a bit of a storage issue. I built a wing dolly (which I’ll post about later), but there’s not that much room in the garage to store the wings. I ended up reorganizing the garage so that the front of the plane faces in towards the back wall (rather than the garage door) so that I have more room towards the garage door side. I also was able to tempoarily put on the canopy doors because the garage door isn’t above the canopy in that area. This helps free up some space and I can also mount the hydraulic lifts for the doors.

I still have to finish up the left wing so I may try to get that done first before anything else. The weather is still really nice here in CA, but I’m sure it will start getting more windy and rainy soon and I don’t want to try to be building the wings and having to deal with that. The right wing is mostly finished so I want to try to get that into the garage this week.

The fuel tank jigs are finished, now I just need the left skin and the sealant and I can do the tanks. The jigs went together pretty quick. I used some left over plywood and had to purchase 2 2×3’s for the cross bar. I also did a test fit of all the ribs and Z channels for the right tank.


Right Wing Top Skins

Time: 13.5 hrs

Wow it’s been a few weeks since I posted. In that time I prepped and primed all of the top skins for both wings. I started with installing the skins on the right wing because it’s the easiest in that it doesn’t have the pitot tube. I finished up the wiring and double checked that everything was riveted on the wing structure. I also tested the wiring for continuity, just to make sure there were no breaks or shorts (you never know). I installed the short torque tubes for the flaps and ailerons and the long tub for the ailerons that runs to the fuselage. For the long tube I had to cut a hole in the wing jig so I could pass it into the ribs.

After everything looked good I clecoed the 2 main top skins on. I had tried to also cleo the leading edge skin, but I found that it pulled the wing in such a way that buckled the 2 main top skins so I decided the just get the 2 main skins riveted and do the leading edge skin after. I’m really happy with the way the top of the wing came out. There was one area of about 5-8 rivets the rear spar that needed to be elongated just a little bit to get the holes line up with the spar hole. It wasn’t a cleo pattern issue because all the hole before and after the area lined up fine.

Once the main skins were finished I clecoed  the leading edge and wing walk (wing root) skins. The wing walk skin lined up great. I think there was one hole that was a bit off. The leading edge skin was a real pain though. The tip part lined up fairly well, but as you moved towards the root it got out a bit. What helped was using clecos in every hole on the main spar and also I clecoed the ribs before clecoing the main spar. Still there were 2 holes toward the root end that just didn’t line up. One will get covered by the fuel tank skin.

Wire run to the landing and taxi lights. I used the lightening hole bracket that I purchased for the fuselage.

Had tp make a small how in the jig to get the long torque tube in. I could have waited until the wing was done, but I wanted to get this installed.

Aileron torque tubes installed

Flap torque tube installed

This rib is a bit wonky. I reriveted the front rivets that attaches it to the main spar, but it was still a bit bent. When the top skin went on it straightened out OK.

I installed an 1/8″ stainless steel rod to help support the strobe wire. It runs all the way to the wing tip and keeps the wire from hitting the bottom skin..

Celcos are in on the main skins and it’s ready to be riveted. Too late to rivet though so will wait until tomorrow.

All done. Happy with how it came out. Also the oil canning on the bottom of the wing seems to have gone away and no oil canning on the top.

I need to get started on the fuel tanks. I’m still waiting on the left tank skin from TAF since mine is really scratched (from shipping) and needs to be replaced. I guess I’ll start prepping the parts and maybe get some of the components installed on the ribs. I ordered the sealant and a SEMCO sealant gun so hopefully will have these in the next few days.

Bottom Skins Done

Time: 16.25hrs

This week I was able to finish up the bottom wing skins. I also installed the rivnuts for the inspection panels and for the smaller panels as well. The smaller panels are supposed to be riveted, but I’d like to be able to have them come off for better access to the wing. I installed M3 rivnuts which worked fine.

I ended up purchasing a 4.9mm reamer from Amazon. The 4.9mm reamer is the absolute perfect fit for the M3 rivnuts. I first reamed the hole with the #11 reamer and then used the 4.9mm to enlarge it just a tiny bit. Perfect fit. I haven’t used too many M3 rivnuts on the build so I never bothered to find the exact fit. I think I had either used the #B reamer or the #11 and then just filed it slightly for the ones that I needed to drill out.

One time consuming thing was that while I was wiping off the skins after sanding the rivets I noticed a few spots that oil canned. One spot was especially bad so I had to start drilling out rivets and seeing how to relieve some of the tension in the skin so that it would sit better and not want to bubble. The right wing had the worst issue, but that was fairly easily fixed by drilling out the row of rivets on the leading and trailing edge between the ribs in the area with the issue, then reaming the holes, clecoing and riveting them again. I wasn’t able to completely fix the area near the first flap hinge on the the left wing and the area near the last aileron hinge on the right wing. I was able to minimize it, but it still has a slight bump in those areas. You can’t really see the bump but if you push on the skin in makes a sound like an oil can. It’s much better than before, but still does it a bit. I guess I can live with that and I noticed that maybe when the top skin is on and the ribs are straighter then it may solve the problem, but will have to see when the top skins go on.

Oh I also got my bag of stainless steel rivets from TAF (for the Service Bulletin 0014) so after I get some B2 sealer for the tanks I can install those as well.

Skins are on, rivets are filled and sanded.

I installed M3 rivnuts for the small and large inspection panels.

Bothe the left and right leading edge skins are riveted on the bottom. The top needs to wait because the top skins sit under this skin.

I also did a test fit of the fuel tank skins. One of my skins has a big scratch so I’m getting another one from TAF. Hopefully it will be here soon so I can start on the fuel tanks.

So now I need to flip the wings over so I can finish up the wiring and pitot tube install and get the top skins on.

More Wing Skins

Time: 2.5 hrs

Today I was able to attach one of the leading edge skins. I’m waiting on the other one from TAF so I can’t do that one yet. This went surprising well. It was a bit of work getting it to wrap around, but after getting a few clecos in the ribs it wrapped around fairly easily. I didn’t rivet the top portion since I still need to flip the wings over and do the top skins which fit under this skin.

I also riveted the portion of the inner most top skins (the wing walk area) so I could get all the bottom rivets done. I checked some of the top holes and they seem to line up OK. The   trailing edge didn’t fit as well on the right wing as the left, but not too bad over all.

The rivnuts for the lights also got installed without any issue. The newer bracket I resented from TAF actually had the correct hole size for the rivnuts so that saved some reaming time. SO just need to do the rivnuts for the inspection plate and fill/sand the rivets and then I can flip the wings over.

Outer leading edge on the right wing is partially riveted and rivnuts are installed for the lights. The rib to the left also gets the fuel tank skin attached to it so I can’t rivet that yet. I’ll also need to prep and prime the overlap area.

This is the inner top skin. This fit very well on the left wing and took a bit of work on the right. On the right side it seemed that the bend was a little off and I had to try to move it a bit, which is really difficult to do because it’s a very thick aluminum skin.

Wing Bottom Skins

Time: 24.0 hrs

Over the past few weeks I did quite a bit of work on the wings. I haven’t posted much because the bulk of the work is prepping and priming parts… not too exciting The wings have been going along fairly well, no big issues or problems. The only problem so far was with the fitment of the bottom skins. One particular area is the row of rivets that attach the fuel tanks to the main spar. The main bottom skin also uses those holes and if you line up the bottom skin so that most of the other holes align then this row is fairly far off. I had been waiting for the factory to let me know what to do about the alignment issue. The final fit come was that this is an issue on the Sling 4’s and to just widen up the hole in the skin (not the spar). So with that answered I could finally move onto riveting the bottom skins.

It’s a bit hard to see in the photo, but the row of hole in the primed area are a bit off. TAF said just to open them up a bit. I checked the fuel tank skin and the holes seem to line up OK so these holes will just be sandwiched in between the spar and the fuel tank skin so I guess it’s OK if the rivets don’t fit tight.

Prior to riveting the skins I installed the REV1 of the rear spar lower join angle (WG-ANG-005). When doing inventory I notice that I had a REV0 of the right one and a REV1of the left one so I had TAF send me REV1 for the right. The difference is the notches in the ends of the bends to help prevent cracking. The upper left one in the photo is REV1 and the lower right is REV0. I suppose I could have just made the REV0 a REV1 by notching it… Oh well.

Right wing bottom skins are done. It actually went pretty quick. I think only about 1.5-2 hrs. Now they need to be filled 😦

I have a stray hole in the skin. I will need to drill it out from the other side (to make a hole in the correct location) and then fill this one. I don’t want to drill out this hole because it seems like it will hit the actual rib and not the flange on the rib.

That rivet there will need to be cut. It hits one of the parts that make up the bracket that holds the bell crank for the ailerons.

Left wing ready to rivet.

And it’s finished. Only took about 2 hours. I hand riveted the rivets around the aileron and flap hinges since the pneumatic riveter didn’t fit well.

So next I’ll rivet on the leading edge skin I have (for the right wing I think). Still waiting on the other from TAF. I’ll also rivet the bottom part of the top inner skins, the wing walk area so that I have those bottom rivets done. After that I can fill and sand the rivets.. oh and install the rivets for the inspection plates.


Time: 8 hrs

Over the past week or so I’ve been working on and off on the flaps. Theres a lot of prep work, plus priming before assembly so it take a lot of time. Plus I wanted to let the primer dry for a few days before putting things together. In any event the flaps are mostly done. I’m still missing rib #1 so I’ll have to rivet that in when I get it. I also left most of the leading edge unriveted so that I can get it to match the wash in the wing when the wings are completed.

The flaps went together very quickly, no big issues in alignment or fitment. I did end up using 12mm long 4.8mm rivets in rib #102 to fit the bracket to the side of the rib since the 15mm rivets seemed a bit long. The manual only says to use 4.8mm rivets and doesn’t say a length. I assumed they wanted 15mm all around since they provide you with so many. In most cases you need the extra length because there are a few pieces to get through.

I’ve also been working on finishing up the engine. I’ve been waiting on some parts so that I can mount up some of the hose, etc. I’m also seeing if I can get the sensor cable from AirMaster for the propeller so that I can finish up all the engine wiring through the firewall. They said they’d sell it to me and I’m now just waiting on a reply to see how to pay them. So hopefully I’ll have that finished up in a week or so and I’ll take a bunch of photos.

The flaps mostly riveted. The leading edge is left unriveted so that I can match the wash of the wings when they’re done. Everything went together pretty quick.

Rear Spar

Time: 4 hrs

Finally got to do some riveting on the wings. I finished up most of the rivets on the rear spar, but still need to rivet the larger 4.8 rivets. I want to wait on riveting these ribs because I need to make sure the holes are large enough for the wiring, just in case I have to widen the holes. Everything went fairly well, I needed to up a few hole sizes and had a few alignment issues, but over all not too bad. The manual shows to rivet the skin support channel onto the rear spar first, but it seemed like it would be difficult to rivet the ends of the ribs so I decided to do the trailing edge of the ribs first and then fit and rivet the support channel. That seemed to work well.

I also fit the AN3 bolts on ribs 12 and 13 and will tighten them later. The manual says to fit them with AN3 bolts but not the size so I just matched the existing bolts which appear to be AN3-14A with a thin washer on the head side and a thick on the nut side.

Rear spar mostly done with the trailing edge of the ribs and skin support channel riveted. All the rivets are done from this side.

This is a photo of ribs 12 and 13. The top and bottom holes of these ribs are fitted with AN3 bolts to continue the row of bolts used to hold the spar together.