Why does the Canair use a small ducted fan instead of a large propeller?
A – Large diameter, slow rotating propellers can be highly efficient for thrust but cannot be used to also produce air at the pressure needed for the air cushion. If one is prepared to build in additional pulleys and a second fan for lift and a second bearing system, it will work. Canair is a strong believer in vehicle safety, not only for the pilot and passengers, but for the others outside the craft. Adequately guarding large propellers is not easy. The guards need to be big and strong with a mesh size to keep hands and fingers out. The problem is that a guard of this size can be heavy and the small mesh tends to restricts the airflow into and out of the propeller, thereby reducing the crafts performance. A smaller ducted multi-bladed fan may not be as efficient or as quiet as a large slow rotating propeller but has a low thrust line, is more compact and streamlined and is easily made very safe for all concerned.
