This entry starts the preparation the RV-12's "other" wing spars. It not a very long section.
Step 1: Cleco one W-1208B Stub Spar Doubler to each of the W-1208C-L & -R Stub Spar Channels, on the outer web (opposite the direction that the flanges are bent.) Mark the stub spar doublers as left and right per call out. Refer to the stub spar doubler and channel as the Left and Right Stub Spar Assembly.
CAUTION: Avoid using a dimple as a guide for the countersink depth. The dimple may prevent the skin from laying flat even when the coutersink is too large.
Step 2: machine countersink 120 degree the W-1208C-L & -R Stub Spar Channel, per plans, on the outer surface of all the holes in both flanges as called out. Drill a 1/4 inch hole in a thin piece of scrap aluminum to make checking the maximum diameter of each countersink easy.
Builders note: I don't have a picture of the gauge I used. Also I found using a micrometer was easy as well.
Step 3: Machine countersink 100 degree the three holes at the inboard end of the Stub Spar Assembly to fit the head of an AN426AD3 rivet.
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