Using Scotchbrite wheel, trimmed all stiffeners' ends to 15 degree angle. Using 1x2 on drill press as fence, drilled 5/64" pilot holes in stiffeners. Measured each stiffener using 1 1/2" rivet spacing to the last 3-4 holes. Then slightly altered measurements to fit space left. Started rivet spacing at 3/8" in on stiffener end next to forward spar. Started rivet spacing at approximately 1/2" in from other end of stiffener. 1 1/2" spacing was measured out beginning at spar end of each stiffener. Drilled and clecoed stiffeners to skin and worktable. Used #41 bit. Drilled all stiffeners and clecoed on one side and then removed all at once. Deburred half of the stiffeners.
