The instructions in OP-40 show two curved inlet outer flanges but due to all the modifications I had to make, I decided to fabricate my own. First, I had to reinstall the spinner flange and realign the lower cowl to its final mounted position (Pic 1). Next, I used card-stock paper to draw a template for the right and left outer inlets (Pic 2). I used the templates and fabricated both outer inlets from stock aluminum. For the right side, to get a perfectly curved flange, marked the aluminum with a series of radiating lines from the inside of the curve to the outside. Then, I placed the upper flange lines in my vice with the edge of a block of hardwood on the lines. I carefully made a small bend on each successive radiating line until I got a curved surface. There was a considerable amount of trial-and-error making these curves; but in the end, they turned out good.
