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CaptPausert

Well Known Member
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So I am countersinking my flap and aileron spars right now. I understand that the holes will be a bit knife edged in this .040" material but i am also ending up with out of round holes on the bottom. Does everyone have this issue? Should I get a #37 or #38 reamer and try to round out the holes?

Kind of regretting not dimpling them despite the instructions saying to countersink. Just took a Boeing repairs class and this would be an absolute no no by their standards.
 
I almost forgot i have a couple of extra flap spars from when i accidentally got sent extras during the laser cut part issue.

Does anyone have a good suggestion for a good setting for the countersink past flush for the countersink that the dimple goes in? Or is my best bet to make a backup strip to put on the underside of the flange for the pilot to ride in to prevent wandering?
 
The oblong hole result is because with thinner material, the pilot of the countersink bit doesn't have a reference hole all of the way through. Always use something to back up the hole if there is question. I usually go the easy way and just use a scrap piece of wood with holes drilled in it. It doesn't take much to keep the pilot from wandering. Van's recommends that a countersink be .007" deeper than flush for accepting dimples. There are posts somewhere on VAF that show why that's the case, but that's the bottom line for most skin dimples.
 
CaptPausert said:
... Does anyone have a good suggestion for a good setting for the countersink past flush for the countersink that the dimple goes in?...
Click to expand...
The answer is in the famous Section 5

Kit instructions page 05-08 says, in part, "For a dimpled skin riveted onto a machine countersunk surface the countersink must be slightly deeper as mentioned earlier. Proper depth is .007 deeper than when the rivet head is flush. This depth correction corresponds to seven "clicks" on a microstop countersink tool indexed in .001 inch increments."
 
Yes that is what i set my cs cage to when i started but it was causing oblong holes. When i get home tonight i am going to make a back up plate for the pilot to ride in and try that
 
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