Riveting the leading edge to the main spar.^2h

Today I riveted the leading edge to the main spar.

The next step was to rivet the leading edge to the main spar. There are different ways to do it, the easiest is probably just to use LP4-3 and LP4-4 pull rivets. However, in a few places, the holes are very close to the main rib webs -- not sure if folks pull them from inside of the leading edge then?

Also, I somehow managed to mis-drill the holes in one of the ribs. I'm not sure when exactly I did that, possibly, when I drilled two new holes in the rib (on some of the ribs, two outermost holes on the flange are not used and instead you drill new ones through the spar). So, I upsized them to #27 drill bit, for a NAS1242AD4 rivet (they are the same as AN470AD4, but with shank size being 9/64").

So, I went with the option of using solid rivets. It is possible to rivet them from the bottom. To do that, you need to grind a double offset rivet set a little bit. However, I decided against that because I thought that keeping the bucking bar straight would be difficult with the bucking bar being inside the leading edge.

Instead, I chose to follow the steps of one of the builders on VAF who put the rivet gun inside the leading edge, with the shop end being at the rear side of the main spar. This also places the factory head over the thinner flange material, which also helps.

I experimented with the positioning of the rivet gun, and with some work, it could be positioned over all of the rivets, with the hand holding the gun through various lightning holes.

This is the 3X rivet gun inside the leading edge. I taped the double offset to make sure it was always "clocked" the same way ("forward").

This is roughly how it goes over the flange.

Overall, it was a relatively smooth procedure, except that one time I did not notice that my gun was not positioned correctly and damaged part of the flange.

I don't think this part of the flange does much work, so I'm not going to do anything about it.

The one station in the middle of the leading edge was particularly hard to position the gun because I wasn't able to reach there with both hands to "guide" the rivet gun by feel. So I used my cheap Wi-Fi borescope instead, which worked perfectly.

The end result (photo taken by the borescope).

On the outermost main rib, the flanges are lifted during the riveting process. I checked with the gauge, and I cannot reach the rivet stem with the feeler gauge, so I don't consider them to be of any concern. Thinner flanges tend to lift when I rivet them with AD4 rivets.

After riveting the leading edge, I installed the fuel tank on the main rib. I still haven't riveted the spanwise rivets, I will do it once I check that the top skin still fits well (to make sure the main spar didn't bend).

The fit of the fuel tank is very good. Everything matched perfectly.