The first time a builder new to blind or pulled rivets (sometimes incorrectly referred to as “POP®” rivets) sets a rivet, they glance at the rivet’s tail and see it isn’t perfectly round and straight, like the plans show. And they worry. Rest easy, my friends, a rivet tail will seldom form in the perfect form illustrated in plans. They form oblong in diameter, and they are prone to curving one way or another.
Rivets have an effective grip range. A rivet whose grip range is tasked to hold parts whose total thickness is on the lower end of a rivet’s grip range will tend to deform more. A rivet tasked to hold parts whose total thickness is near the maximum of a rivet’s grip range will tend to deform less.
The only control a builder has over the shape of a blind rivet’s tail is to make sure the rivet’s grip range is correct for the thickness of the material being fastened, the rivet’s hole has been drilled to the proper diameter, the air compressor’s pressure setting isn’t excessive when using a pneumatic rivet gun, and the head of the rivet is flat on the surface of the material being fastened. If you ticked all those boxes, the tails will do what they do—deform.
None of our blind pull rivet tails look like your picture and that’s because we use avex rivets, not your local hardware “pop” type rivets… there is a difference.
The rivets in the photo are Cherry N rivets, which are used to assemble all Sonex airframes. Builders should never substitute the type/brand of rivet a designer intended for an airframe. (“POP” rivet is brand name that has become synonymous with pulled/blind rivets in the same way the “Kleenex” brand name has become synonymous with tissue.)