12 January 2014

Empennage: Aft fuselage. Bulkheads riveted.

Got all of the bulkheads riveted.  Mostly good work on my part, however I had two outcomes that will result in a lighter wallet.

First they get cleco'd up.

Then they get nailed together.

Horizontal stabilizer front attach bulkhead.   All rivets squeezed.  I actually had to remove and replace the two top rivets on the right attach bar.  On one I mangled the shop head by being off center with the squeezer and the other somehow got a rivet that was 1 mm too short.


Bulkhead with tail tiedown.  All rivets squeezed.  Notice the slight warping of the holes near the #12 screw holes in the bracket.  This was due to my dimpling those holes (per plans) only to realize that they should not be dimpled so I had to flatten them (plans need a revision on 10-07, step 1).  I also dimpled each hole in the web the wrong direction and had to re-dimple in the right direction.  Update 11-Dec-14:  I've decided to replace this bulkhead even though it's already riveted in.  Update 29-Jun-15:  The bulkhead was replaced after installation in the aft empennage.


Horizontal stabilizer rear attach bulkhead.  All rivets squeezed.


Aft bulkhead with rudder cable bracket.  I used the rivet gun to prevent warping such thin parts with the squeezer.


Forward bulkhead.  Again, I used the rivet gun to prevent warping such thin parts with the squeezer.


So now, the big mistakes.

Mistake #1:  I took the picture on the left to be manifested in the physical world as on the right.  How could that happen?  See, I got overconfident on recently finding several rivet sizes in the plans that were inaccurate and decided the AN470AD4-4s called out should be -6s.  Proud of myself for finding another error in the plans, I later found that I was the one in error, but only after squeezing 19 rivets.


I decided I could drill out those 19 rivets to separate the parts and move on.  Which I did.  The holes were slightly enlarged, but not too badly.  However in the end, I decided that I didn't want that part in the plane with the stress introduced by my error.  So I'm going to replace those parts.  The battery angle is $17.  We'll see what the ribs are.  I'm awash in surplus nutplates so I don't need to purchase any more of those.  I'm actually solving two issues at once since I also had a countersink too deep on one of the battery angle nutplate attach rivets.


Also, the plans don't call for the bellcrank rib flanges to be dimpled #40.  They need to be as they will be directly riveted to the skin.

Mistake #2:  On the systems bulkhead, I dimpled not just the nutplate attach holes (the latter highlighted in red), but the screwholes too.  Not a big deal really.  I pressed them out, but because dimpling stretches the metal (especially for #8 screw holes), the part was no longer very planar.  Looking at it, I didn't want it in the plane, so I scrapped it and will replace it.  Also, whilst working on this bulkhead, I found out I was missing MS21055-L3 (a.k.a. K3000-3) nutplates.  Apparently, I'm not the only one.  Wasn't even on my manifest.

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