What happens if a rivet shank is not properly clinched and protrudes excessively from the surface?

When a rivet shank is not properly clinched and sticks out excessively, it can lead to significant structural issues. Properly clinched rivets are crucial for ensuring the integrity of the assembly, as they are designed to create a strong mechanical bond between materials. If the shank protrudes too much, it indicates that the rivet has not been set correctly, which can compromise the strength of the joint.

An improperly clinched rivet may not hold the components together adequately, leading to risks such as loosening, shear failure, or even catastrophic structural failure under stress or loading conditions. In aerospace applications, where safety and reliability are paramount, ensuring each rivet is set correctly is essential.

The other options do not reflect the engineering principles involved. Acceptability in riveting is based on strict tolerances for safety, while aesthetics or aerodynamic improvements are secondary to structural integrity function in such critical components.