I read over the following Wikipedia page on Duct fans and it seems to me, they would be more efficient on a Multi-rotor copter (MRC) because unlike an fast moving aircraft, the thrust required for MRC is mostly static.

http://en.wikipedia.org/wiki/Ducted_fan

• By reducing propeller blade tip losses, the ducted fan is more efficient in producing thrust than a conventional propeller, especially at low speed and high static thrust level (airships, hovercrafts).
• By sizing the ductwork appropriately, the designer can adjust the air velocity through the fan to allow it to operate more efficiently at higher air speeds than a propeller would.
• For the same static thrust, a ducted fan has a smaller diameter than a free propeller, allowing smaller gear.
• Ducted fans are quieter than propellers: they shield the blade noise, and reduce the tip speed and intensity of the tip vortices both of which contribute to noise production.
• Ducted fans can allow for a limited amount of thrust vectoring, something normal propellers are not well suited for. This allows them to be used instead of tiltrotors in some applications.
• Ducted fans offer enhanced safety on the ground.

I would like to ask your thoughts on this topic. I know the general debate has been, Duct-Fans are less efficient but I think this argument was based upon the EDF with a very small OD. I believe the largest I have seen is a 90mm.

nice brought it up...

i think the adv/disadv is pretty much based on research on large vehicle( airplane, ships) and a very fast speed( comparing to multirotor)..

since it is a new dedicated post....i'll move my discussion from the other thread
this is my point in respond to chaosdestro0

Less efficient than a propeller at cruise (at lower thrust level).

if you scale down the weight/shape/volume down to multirotors, the thrust level we have is relative high .. thus the efficient should still be at a good level

This is the video that made me think it was less efficient

mwc quad // flying saucer [2] (2 min 8 sec)

What you also have to factor in is drag caused by the frame. In my opinion the best idea would be to use a wire cage around the propellers, very low drag and weight.

In the video, the drag is from the poor aerodynamic of the frame and not the ducts.

Originally Posted by rimshotcopter

In the video, the drag is from the aerodynamics of the frame and not the ducts.

I think you are right, I think there should be some testing on this. Wire cages is probably an easier method to protect people from props but I think just proper safety methods would be better for most people.

happens, we can not always plan for that.

Originally Posted by chaosdestro0

I think you are right, I think there should be some testing on this. Wire cages is probably an easier method to protect people from props but I think just proper safety methods would be better for most people.

that is not a duct fan ..... OMG... all the flat surface results in drag (esp the top)

the dust has to be like a thin layer cylinder..

like this

but we are looking for at least maintain the trust w/o duct... i wonder if there is plastic bottle having 5"~10" D... they are just barely weighted

Originally Posted by jy0933

that is not a duct fan ..... OMG... all the flat surface results in drag (esp the top)

the dust has to be like a thin layer cylinder..

like this

Yes I was wrong and didn't think about that when making that comment.
Anyway, has anyone got any ideas about how you would mount a duct to most multirotors?

Originally Posted by jy0933

that is not a duct fan ..... OMG... all the flat surface results in drag (esp the top)

the dust has to be like a thin layer cylinder..

like this

I like this and have lots of Master Airscrew props. I wanted to work with fiberglass, maybe it is time to check that one off on my todo list.

Thanks for sharing.

Edited: Looking at this picture, I am sure I can make this duct adaptable to my present bicopter.

well
mounting is not really a problem

we can just cut it from foam just like the ones for AR



foam is light weight. easy to obtain. and you can cut it in one part with fc protector...

Originally Posted by jy0933

well
mounting is not really a problem

we can just cut it from foam just like the ones for AR



foam light weight.. and you can cut it in one part with fc protector...

Yes but I was thinking about people who already have multirotors. We need a solution that people can add to their existing fleet.

The foam has to be ridged enough to withstand an impact, that is why I am not using foam now.

Added weight = less efficient. Plain and simple.

The simplest way to be safe is to not fly near people. Also know your limits, both mechanical and skill.

Originally Posted by rimshotcopter

The foam has to be ridged enough to withstand an impact, that is why I am not using foam now.

enhance it with some strong plastic ring... cut the ring from button of prot and implant it...
cf is the best.. but customization cost a lot..

Originally Posted by MCrites

Added weight = less efficient. Plain and simple.

The simplest way to be safe is to not fly near people. Also know your limits, both mechanical and skill.

the best efficient comes where the load matches the output (correct me, i might be wrong).. the lighter is always better but the weight of the prot wont even be 10% of your batt weight... which is not a big contribution

yes and no for the 2nd part.... not to fly near ppl.. but accident happens sometimes just not a human error.. like rim said... you can never prep for that/see that coming

Originally Posted by MCrites

Added weight = less efficient. Plain and simple.

The simplest way to be safe is to not fly near people. Also know your limits, both mechanical and skill.

Actually in some areas of throttle, ducted fans can increase efficiency.