Has anyone explored using ducted fans for a quad (or other multi)? It would seem to me that the greater efficiency would be ideal even with the added weight. Not only that - it would save on broken props...

I don't think it's greater efficiency, infact it won't be even close
Forget about yaw unless you tilt motors and when you do that, you lose more power
And you would end up with a very loud setup

Don't get me wrong, it would be a very cool setup but that's it

Moe

I was under the impression that ducted fans were more efficient than propellers alone. As for yaw, I believe motion in yaw is accomplished by varying the speeds of the pairs of like-directioned propellers to change the overal angular momentum. I din't see why this couldn't be done with ducted fans as well.

My understanding of this is that EDF units (as fitted to scale jet models, etc.) operate at very high rpm and that their purpose is to produce high thrust in a compact package. As such, their small diameter and additional weight would make them a bit redundant for a quad. (Remember that thrust is always proportional to swept area, i.e. diameter).

"Shrouded" fans, on the other hand, might be more relevant to quads: larger diameter, using a shroud (generally a much shorter tube than a "duct"). The efficiency gain (i.e. the additional thrust/watt) is likely to be very small, but if you needed to enclose the propellers anyway (e.g. for flying indoors) then you might as well attempt to recoup some of the thrust lost to the additional weight.

But note: I've heard of some "casual" shroud setups causing problems - something to do with interference with tangential airflow. So a shroud needs to be very carefully designed.

Hi,
It has been done. Here is one link from 2007 on a quad EDF build from the Mega Index: http://www.rcgroups.com/forums/showt...light=edf+vtol
Cheers,
Jim
Vote for my Bro Joe here: Quadrocopter and Tricopter Mega Link Index

If you are asking about efficiency, amp for amp props are more efficient
EDFs have no torque, so no yaw control
They are normally used for the scale look and the sound they make

But if you are looking for the wow factor, EDFs are super cool you can even build a UFO style quad

I'd like to see a micro quad out of 30mm fans. Something in a 8-10in frame. Then wrap it with some thin depron and make a small UFO

Would be cool to see a thrust vectoring system like on a mig 28. Don't think they make a flight control system for that. Go for it!

Originally Posted by spokeshave

Has anyone explored using ducted fans for a quad (or other multi)? It would seem to me that the greater efficiency would be ideal even with the added weight. Not only that - it would save on broken props...

I am currently evaluating shrouded prop, building my own shroud like this.
I plan to build a quad with 4 shrouds, after testing.

There is a thread for this project:

Propeller Shroud Project

Very nice man.... What's the wieght of this ring?

79 grams. It is just the prototype to conduct thrust test. Later, we could have molded version.
You could read more details from:
http://www.rcgroups.com/forums/showthread.php?t=1447212