A freely (zero friction) rotating cylinder (mounted on a vertical axis) is placed on a model boat instead of a sail. The Magnus force that is created is used to power the boat. A fan is mounted on the boat to provide airflow over the cylinder. Will the required force be created to power the boat? The fan is now placed outside the boat and directed to provide airflow over the cylinger. Will the same Magnus force be created to power the boat? What would be the practical problems with such a vessel, if any?