Cooling air inlets are made from glass layed up over foam and duct tape directly on the engine.
I am building my cowling with what has to be the most labor intensive way; first a wooden frame, then a plug, a mold, and finally the cowling.
After foam, glass, contouring the top and around the spinner.
The rest of the cowling behind the oil reservoir and carb will be done now that the spinner area is done. You might notice that the cowling is a little bit wider than the firewall. The cowling is as tight as I could make it, but it was not possible to make a smooth transition to the fuselage. The gap will be filled with foam and glass to make a nice curve that blends with the fuselage.
The rest of the foam and glass work and contouring is in progress now. After that, the plug will be used to make the mold, then the mold to make the cowling.