Engineering....
Not that I'm any riveting or building expert. But after 30 years of engineering I know something about perfectionism, and value engineering.
.........
That doesn't mean I--or others--are throwing together aircraft "not up to scratch" and I resent the strong implication that because I voted to move on I'm therefore probably building a crappy airplane. It's fine if the OP does want to learn to properly drill out rivets and make better ones, but understand that it is not for structural reasons. Pride of craftsmanship is fine so long as we understand all the tradeoffs.
There is an engineering view on this, and it is not perfectionism....
Designers use MIL-HDBK-5 (since re-numbered to MMPDS-01, but essentially the same data) called "METALLIC MATERIALS AND ELEMENTS FOR AEROSPACE VEHICLE STRUCTURES" as the only approved source of strength data for aluminum structures.
Check page 3 of this recent Battelle presentation....
http://projects.battelle.org/mmpds/Aeromat 2007_MMPDS_060407.pdf
This document gives the strength data for our aluminum material and riveted joints... but as with everything in engineering, there are tolerances. The document does not assume that all rivets are perfect, it assumes a strength tolerance with every rivet meeting a certain specification.
The long standing rivet specification is here on my web site (since copied by many, including Vans...
...) - other specifications exist, such as the Boeing one, but they are basically the same standard.
http://home.earthlink.net/~gilalex/rivet_spec/rivet_a.htm
Any other data (even the Alcoa stuff and certainly Bill Marvel's data) is speculative and not done under controlled conditions. Imagine a certified IA writing up a 337 on a factory plane and referring to that data... it just would not fly.... in more ways than one...
Engineering is full of tolerances and we should build within those tolerances...
perfect 0.5/1.5D rivet heads are not needed, and the tolerance on them is given in the the specification above... there actually is a
large range that makes a "good" rivet rather than a "perfect" rivet.
I believe we should strive for "good" on our rivets, and then we know we are not "eating into" any of the design strength that was calculated when Van designed our planes. He probably over-designed....
... but do we know where, and the actual margins on every joint?
"Good" is not perfectionism.
However, you are the manufacturer, so it is your choice....
gil A -
a 40 year engineer...