Cowl Flap Lines
The picture below is of the cowling for my uncompleted ?red box? Corsair, which I am finishing as a U.S.S. Bennington (CV-20) based F4U-1D. The cowl flap lines have been added (removed?), and are highlighted by the flat black paint which I used to fill in the notches. I painted these areas black so that they will appear darker (and more noticeable) when the Corsair Blue spray paint is applied over the rest of the cowl. The cowl front section was also shortened by ? inch before attachment to the cowl ring, to make it more scale.
Notice how the top flap area has been gently bent downward, so that it will better blend with the fuselage and cowling profile. An alternative to bending the top: after the slots have been cut , AND top area shortened to about 1/2", AND after attachment to the cowl front, you can then use a "T" sanding tool to sand that area until it becomes flush and at the same angle as the front of the cowl.
Remember, Corsair pilots had a difficult time seeing over the nose when they were in the landing pattern (and all other times, for that matter), so they didn?t need no stinkin? cowl flaps popping up right in front of them to make things worse.
After this picture was taken (awhile back), I trimmed about ?? from the rear/ top area, where it needs to blend into the fuselage.