Alphalpha
Well Known Member
This is meant to be discussion based on my observations in building the left wing frame. They have us build up the inboard mixer box to include attaching the main rib that closes out the fuel tank skin on its outboard edge. Having this rib in place creates substantial access problems for some steps that show up later in the KAI. They also have you start the build by installing the next outboard rib first thing.
Leaving these two ribs out for a bit makes it much more possible to get into that area to buck the nose rib to spar to outboard tank rib AN470AD4-12 rivets. It also allows you to get in there and glue on the stringer step-down tabs. Another tip is use two tables to support the project so you can split them right there and get in from underneath.
As long as the rest of the mixer box is riveted (or clecoed) to the rear spar those two main ribs should be easily riveted (in sequence) to the mixer box and spars with them in place. As well, this tank skin outboard rib is riveted to the rear spar with CherryMax rivets according to the KAI, but you could conserve those expensive CherryMax rivets by riveting this aft flange with conventional rivets.
I also had an issue where the inboard mixer box false rib aft flange didn't cleco down well to the rear spar. For some reason the top hole clecoed flat but the bottom one pushed back the lower corner of the flange so the cleco was trapped between the rear spar and the false rib aft flange. I didn't see this and it caused the subsequent rivets to pull wrong. I didn't see it until I realized the false rib top and bottom flange holes were not lining up well with the tank skins. Not seeing this was my fault because I had the main spar in place just to keep things from being so floppy. But with both spars and main ribs in place you cannot see in there without a bore scope. (Yes, I had a bit of a temper tantrum and then spent the next three hours fixing it.)
The last access issue was getting the outboard aileron push tube inboard end attached to the inboard aileron belcrank was also a PITA and will be much harder to maintain once the wing is closed out. This, once again, confirms my long held belief that any aerospace engineer must be required to maintain aircraft for at least ten years as a practical residency requirement of being an aerospace engineer... just like medical doctors. ;{)
Leaving these two ribs out for a bit makes it much more possible to get into that area to buck the nose rib to spar to outboard tank rib AN470AD4-12 rivets. It also allows you to get in there and glue on the stringer step-down tabs. Another tip is use two tables to support the project so you can split them right there and get in from underneath.
As long as the rest of the mixer box is riveted (or clecoed) to the rear spar those two main ribs should be easily riveted (in sequence) to the mixer box and spars with them in place. As well, this tank skin outboard rib is riveted to the rear spar with CherryMax rivets according to the KAI, but you could conserve those expensive CherryMax rivets by riveting this aft flange with conventional rivets.
I also had an issue where the inboard mixer box false rib aft flange didn't cleco down well to the rear spar. For some reason the top hole clecoed flat but the bottom one pushed back the lower corner of the flange so the cleco was trapped between the rear spar and the false rib aft flange. I didn't see this and it caused the subsequent rivets to pull wrong. I didn't see it until I realized the false rib top and bottom flange holes were not lining up well with the tank skins. Not seeing this was my fault because I had the main spar in place just to keep things from being so floppy. But with both spars and main ribs in place you cannot see in there without a bore scope. (Yes, I had a bit of a temper tantrum and then spent the next three hours fixing it.)
The last access issue was getting the outboard aileron push tube inboard end attached to the inboard aileron belcrank was also a PITA and will be much harder to maintain once the wing is closed out. This, once again, confirms my long held belief that any aerospace engineer must be required to maintain aircraft for at least ten years as a practical residency requirement of being an aerospace engineer... just like medical doctors. ;{)
