Here are the sketches of my NACA scoops. I've also thrown in the only 2 pics I took of the procedure. When I do the radiator scoops , I'll take more step by step pics. Kind'a spaced it this time though.
I first cut a small opening for the scoops to lead into, the width of the scoops . Then I tried carving the curved shape into the plastic but eventually cut a straight ramp as shown in the top view. The side cross section shows how the ramp leads down to the opening.
I cut strips of thin plastic for the side walls of the scoops a bit taller than the scoops. Then glued one end of each to the sides of the opening and let dry overnight.
Next, I fashioned a spacer jig ,glueing 2 toothpics side-side and another centered over the top. The jig could be made varying sizes depening on the size of the scoop.Make the top/centered part of the jig the length of the intake ramp.
With jig in taped in place , clamp sidewalls to spacer at rear of intake, then at narrow forward end ,clamp sidewalls to the spacer.
Make sure sidewalls are all the way against bottem of ramp and run a bead of liquid cement( I use Testors) along the bottom edge of side walls and verify the sides are firm against the bottem ramp of the intake. Again, allow to dry overnight.
Next ,fill in between out side of the sides and the sides of the original ramp. When dry, trim sidewalls flush and add small piece of sheet plastic to cover the opening in kit and give a top lip to the intake. Sand and smooth.
This pic shows my spacer well. the side walls are in place but only glued at the aft end of the intake. I used a couple shims at the aft end to keep the sidewalls firm in place.
Here you can see how I clamped the sidewalls to the spacer to hold the shape while cement dried. One thing to look for here is the narrow forward end is centered
I hope I've explained it clearly.It's not an overly difficult operation. But, anyone with refinements to this process , I'm all ears.
God Bless ,
Howard