I recently installed a new larger, 50mm x 50mm boom in the Milan. I purposely left both ends of the boom open for future use as an air duct. The nose end of the boom was hidden behind the bodywork. The cockpit end of the boom opened onto the rider’s lap. To add the ventilation functionality to the new boom, I needed to create an inlet opening in the nose to allow the airflow to enter the boom to cool the rider. The least aerodynamically expensive place to create an opening is on the tip of the nose where the airflow velocity is zero (stagnated) and the pressure is at its highest. This is called a SPAI (Stagnation Point Air Intake). The cockpit end of the boom just needs a simple 3D printed piece to direct or cut off the air flow. That is still to be done.

I decided to copy the Bulk velomobile’s SPAI, assuming that the Bulk (and the Milan’s) designer knows more about these things than I do. This meant that I needed to come up with a round intake of approximately 60mm in diameter with rounded edges. It needed to be made of carbon fiber in a configuration that could be flush mounted into the Milan’s nose skin. After a few false starts, I ended up making the prototype using a combination of 3D printed plastic pieces and modeling clay. I made a mold of this prototype, from which I made the actual inlet (shown below).

Here you can see the carbon fiber inlet before being surgically implanted into the nose. Feeding air from the inlet to the opening in the boom is this carbon fiber / PETG 3D printed tube. Notice in the Fusion 360 model below that the tube’s shape blends from round at the front end to square at the boom end.

Fortunately, I was able to locate some matching Avery reflective red vinyl needed to repair the stripes.