Gentlemen:

These cowl flaps are done in thin sheet aluminum. the cowl mounting ring is just forward of them. Inside, of course. Cuts were made with a Zona saw, then they were bent out until the angle looked right. And they are the cooling air exhaust.

The complete cowlings, including the flaps, were made from cut off aluminum drink cans. And there are larger cans around, maybe even some big enough for a semi-scale Corsair with 40-60 engines. Or modify a cooking pot. I HAVE seen that done.

Bill.