Riveting decision

I'll spare you the suspense: I'm not going to do it.

Here's why:

  • From a strict engineering perspective, I shouldn't:
    • The holes are over-sized, even for an over-size rivet. Rivet manufacturer says I should not do this.
    • Even the clamping force doesn't seem to do enough to provide proper full grip. The hole does not "close in around the rivet" as I had hoped.
    • As it turns out, the best-bet rivet for this application does NOT have an expanding shank. It really wants a tight fit from the get-go.
    • My tests were done without reaming, which would enlarge the holes even more, and make the problems previously identified even worse.
    • Being in a slightly too large hole, the rivet can set off-center, which is highly undesirable.
  • I can't find any other combination of rivets/tooling that comes close to the over-sized CherryMAX approach.
  • These rivets are quite expensive, would likely add 1000$+ to the project. I probably wouldn't be ahead financially in the end, as the very small efficiency gain wouldn't give me that amount back in fuel savings!
  • I was enjoying the experimentation, but a LOT more would be needed to convince me, more than I'm willing to undertake. I'd have to test with various thicknesses, do shear and tensile testing, etc. and spend more money going through all that.
  • I can sell the solid/flush rivet tooling I have and put the money on the plane instead! Net gain = decent coin.
  • I can't afford to take any risk. If my engineering/decision isn't 100% solid to my satisfaction, I end up with a useless airframe with loose rivets, joints being torn apart, or some other equally horrible consequence. No thanks!
And ... I still have some more fun ahead of me! See my next post on lighting issues!