Ducted fan efficiency if engine is taken out of the equation (pure electric case)

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Well-Known Member
Jan 9, 2007
In the simplest of terms yes however, if the design is off it's optimal point, the penalties involved can add up very quickly, the net effect of which would be extremely poor performance. For optimum function the shroud design has to be matched to the airframe, to the prop and to the performance envelope. The prop position has to be pretty accurate as well as the incidence of the section. The prop tips also need to be very close to the surface since any leakage defeats the purpose of the shroud. In our case we will have a channel molded into the skin that will be filled with an artificial grass (Astroturf) within which will ride the prop tips. This has been tested by the Rohr Corporation a few decades back and seemed to work perfectly. The artificial grass provides a flow surface but its flexibility allows to prop to operate beneath the tops of the grass blades, thus effectively sealing the interface.

The airframe is moving along well, albeit slow (we're doing two projects at the same time so our time is a bit split up). We just mated the wings to the body and are now working on some of the detail stuff on the sponsons. We should be able to mate the body and sponsons within the next three months or so, after which point we'll work on the empennage and systems. If all goes well we should be taxiing by end of summer (I hope).
Hello orion,
Just discovered this post and am intrigued with the astroturf grass, It sounds practical and first thoughts spread to other applications.
Have you heard any more about it ? a thought that flashed into my mind is that of friction heat causing a softening of the material and a pressure deformation of the grass blades. I own a molding sander that makes use of horse hair to support the sanding strands and at the same time allow the conforming to different shapes (horse hair) is little affected by this friction heat.
Just a thought I'm sure they would have used at some point in their research.

Having just found this thread, I might have some answers to the thoughts in my thread "Electric Cessna". I want to thank everyone that supplied calculation information.