I've a 72" span Dymond Tiger Moth that is coming along nicely, but I’m starting to have second thoughts about the cowling. Specifically, I wonder if there will be enough cooling. I took some photos and would appreciate informed opinions.

The YS91AC mounts inverted on a plywood bearer, and there are ¼” balsa “cheek cowls” that support the ply. So the air flow is pretty much into the left side (1” x 2” cutout), and out around the exhaust pipe. A bit of air can flow out the bottom of the cowl, where the gap is about ½” x 4” wide. The air is flowing around the exhaust side of the engine, but doesn’t look like it will get to the head or intake side.

The directions mention a preference for an identical 1” x 2” cutout on the right side of the cowling. Not scale, but sure beats an overheated engine. I could just try the cowling as-is, and see if there is a problem. But if it obviously needs more airflow, it would be easier to make the cutouts now.

Penny for your thoughts,