Rivet spacing

[Nev]

I’m current doing the boot cowl (4-place) and have decided to rivet the main boot cowl to the firewall, with removable panels at lower portion beside the tunnel attached with nut plates.

Is there a rule of thumb or convention for rivet spacing and rivet size ? The book Aircraft Sheet Metal (and Bearhawk Tips) both give a minimum and maximum spacing, however I could not find a reference in the AC43. Is there perhaps a standard spacing that is considered best practice?

Any guidance appreciated.

[Mark Goldberg]

It seems to me that the boot cowl is not really so structural a part of the plane. I would think spacing could be from 2 inches to 4 inches. It just needs to look nice and not "bulge" up between rivets. Spacing could vary as needed in different parts of the boot cowl to make it fit and look right. Mark