Rear spar countersink or dimple?

[Andy Smith]

The outboard row of rivets holding W-707F/ W-707A W-712 rear spar is shown as being flush to allow the aileron attach bracket to fit over it. I notice that Dan Checkoway machine countersank the W-707F spar end reinforce plate despite being, at .040 thick, is less than Van's recommended minimum for a 1/8" rivet. Should I dimple the the plate, spar and rib, or is there something I've missed, as usual.
Andy Smith

 

[alpinelakespilot2000]

I asked Gus the same question on my -9 because I'd never stacked three dimples together before this point. His answer: dimple all 3 layers. Works just fine and my aileron brackets sit nice and flush. If the countersinked layer is sandwiched between two others, though, countersinking thinner than .050 material is OK for 426-4 rivets. My experience has been that if I follow Section 5 in the manual religously, except where Van instructs different in the drawings or instructions, then everything works out just fine. Good luck.

 

[Andy Smith]

Thanks Steve,
I thought it had to be something like that but I'm getting more and more cautious, having made a few mistakes already.
Andy Smith
Alpington
England