Rivet rear fuselage longerons 401 and 501

For longeron 401 3.2mm rivets up front and 4mm rivets at the rear side skins, due to the need to upsize on the left hand side. The right hand side was also upsized, for "consistency". Note that some elongation of up to 0.7mm persisted in a few of the 4mm longeron holes. The 4mm rivet tails were verified to be readily able to swell and fill these elongations. Some cleaning at the 0.1-0.2mm level was required along much of existing 3.2mm longerons, due to random variations. This is typical for longerons and stringers, but the 3.2mm rivet tails were readily able to fill elongations of this amount, or even greater.

After elongating/cleaning all holes as necessary, the longerons were removed, and deburred if needed and cleaned up before final installation.

The longeron 501 position was precisely fixed by inserting the AN3 step bolts.

The absence of twist was confirmed using the laser level, and the rear top skin was clecoed into position as a further precaution.

All rivets dipped in Duralac green.