It has promise, but I'd be mostly concerned about the clearance between the props and the shrouds. If there was the slightest movement and the props contacted the shrouds, it could be disastrous in the air. It looks really tight here. Might have to go with slightly smaller props to insure that wouldn't happen. I don't see how you could insure structural stability with the way these are attached.
Yeah agree its only a concept and a superimposed photo but just wanted to get a feel from people as to the reason why people don't or why they think it should be done, pro's and con's etc.
this might be very interesting with a coaxial Cinestar. I wonder if that might produce unwanted side effects, or if it might even provide smoother airflow with the two props spinning in opposition? You could also get a little economy of scale with one larger shroud versus two smaller ones. i'm intrigued. i wish i had a 3D printer!
You're almost on your way to creating a ducted fan motor -- which, as I understand it, does offer some increase in efficiency for higher RPM. See http://en.wikipedia.org/wiki/Ducted_fan Andy.
Coud be a nice plug and play add-on when required ... Close encounter flying amongst the trees, tight spaces near walls ... I would imagine it buffering itself if you brushed up against a wall. Weight might be an issue for general flying conditions, but well worth packing it in the box of extras! Nice one Tom.
There's a good thread on rcgroups about shrouded motors, but it seemed like it wasn't a great option and the idea was abandoned. My CS8 barely fits in the car as-is, and that would definitely be too big.