I may be missing something obvious but on page 09-13 in the -14 plans the top trim tab spar flange is countersunk and the bottom flange of is dimpled. Why not dimple both?
I'm new at this and I'm building a -9A, but this looks to be the same at the -9 trim tab. As I understand it, the reasoning is that the hinge mates flush under that top flange, dimpling the flange would interfere with that. The top is countersunk to accept the dimpled skin above it. I think dimpling the hinges is avoided as it warps the hinge quite badly.
Claude has it right, the diagram has the hinge under the lower flange but look at the rivet lines and you will see that it nest under the top flange where the holes are to be countersunk and not interfere with the hinge.
If you dimple there you'd have to countersink the hinge. The spar flange is a bit thin for countersinking but it will be sandwiched between two other pieces. Note the instruction to cleco the hinge on, then countersink.
I agree, it's easy to envision a diagram differently than it was meant. Once you have that vision in your head it's very hard to get right without someone with a fresh look spots it for you.
