Now we need an expanding duct that goes from the NACA and slows the air on its way to the heat exchanger.

I started with a block of blue foam after planning out my size and degree of expansion. I went with 5 degrees after some research. 7 (or 11 degrees included) is the MAX but less is better if there is room.

After carving as you see in the first two pics I then microed the shape. After cure I sanded it down and then did another lot of micro. Finally I waxed the mold shape and covered it with several layers of hairspray for a release.

In retrospect, using duct tape is pretty good and a LOT faster. This job was two cure cycles and took a while. Pic three has the setup ready for glassing.

Foam carving

Shaped

Microed and waxed