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.

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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.