This is not really feasible as the whole bell turns, difficult to atach a duct. Long time ago, @superlefax tried a prop with a protecting ring attached to the blades but it did not work, it was too inefficient.
This is not really feasible as the whole bell turns, difficult to atach a duct. Long time ago, @superlefax tried a prop with a protecting ring attached to the blades but it did not work, it was too inefficient.