Page 35-13, step 2 calls for the F-01467B panel flange doubler (the thin strip at the top) to be countersunk. I couldn't figure out why that's called for given just how thin that piece is (0.032"). Seems like dimpling the mating parts would be a better way to go as, even though 0.032" is acceptable to countersink (page 5-08), it's too easy (for me, anyway) to elongate the holes, as I experienced with my original fuel tank skins.
I
put in a query to Van's to see why countersinking was called for rather
than dimpling. Their response was simply that "The .032 material
could be dimpled or CSK. In this case we chose to CSK it." Whilst that
doesn't answer my question, that ultimately isn't important as it
confirms that dimpling would be okay. So that's what I chose to do for F-01467B and the F-01467A-L/R instrument panel angles. Because this will be a visible and touchable part of the plane for the occupants, it's important to me that it look and feel nice, with no prideful or sunken rivets due to any less-than-optimal countersinking on my part.
Van's may have wanted this part countersunk because the dimpling would cause the thin, curved piece to distort, just like the W-1019-L/R splice strips on the wings. Effectively, the stretching of the aluminum around the dimple can aggregate over many dimples to deform an entire piece. And it turns out the piece did just that following dimpling. But it's easy enough to bend it back.
Van's may have wanted this part countersunk because the dimpling would cause the thin, curved piece to distort, just like the W-1019-L/R splice strips on the wings. Effectively, the stretching of the aluminum around the dimple can aggregate over many dimples to deform an entire piece. And it turns out the piece did just that following dimpling. But it's easy enough to bend it back.
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