Wing Main Spar 13-3-1 to 13-3-3
![Image](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiQfmboAtJ-vYQZG7GC-PP1aPsrpUxIAGfd68WIdkRsd0EP9_uC5vsNoias66C4QO-0ZxoSQi2We4zEwDTsF16C29GGFhO7lhw8fhXyj9mMneuh2D4h_EsSy60sF0aEtcTxJYMTDMTF2ZLLJgdREMlyN5rmx79mP4Eh2j8EBthFCFSRhhrMmMwfE56i/w480-h640/20230718_212441.jpg)
The next few steps in preparing the spars have you countersinking all the (hundreds of )holes to various depths, and riveting tank attach and access panel nutplates in place. First off, I reamed all remaining 3/32" holes to #40 (those that I had not previously drilled) as they are all slightly undersized. I continued by clamping the spar on its side, and taping off any areas where metal chips could enter which would then be difficult to remove. Spar clamped to workbench and any areas where metal chips could fall in are taped off with masking tape I then countersunk all the nutplate attach rivet holes for tank attachment and access panels to flush rivet depth. I also countersunk the 7 rib to spar attach rivet holes that were in line with the tank attach nutplates to flush rivet depth on each spar flange (28 holes in total). Countersinking nutplate attach rivet holes to flush depth. I used a rivet to test each and every holes as I drilled to ensure that the countersink cage was no