I am installing a new storm window (vent window). Do I need to drill the rivet holes oversize, as is done for the screws in the larger windows?
Technical Editor:
No. The rivet holes in the storm window hinge line and latch attachment need not be oversize. I also normally use soft non-structural rivets in the hinge line, not the hard AD rivets.
The non-structural rivets don’t have the tiny dimple in the center of the head.
The soft rivets will still fill slightly oversize or misshapen holes.
They won’t tend to create stress risers, when they expand in the hole.
They take less force to set, so you are less likely to damage the window during the work.
There are several reasons you do not use oversize holes there.
A rivet requires snug holes, or it will not set properly; it will bend over if it is not held straight. It is also designed to collapse when set, and fill the hole (rivets provide more strength in shear than in tension).
The rivet holes are all in a straight line, and the window is very small (compared to a cabin window). There is almost no differential expansion across the span of the acrylic, which could create a stress riser.
And to wrap up, there is no significant twisting force, such as occurs on a cabin window when the fuselage warps a bit during turbulence or landing, that could force a screw shank against its hole and start a crack.