Ducted Fan Multirotor !!!

[Cloudbuster]

Hi all ... just wanted to know if any of you have experimented with ducted fans over conventional props ??? have seen a few bits on youtube but seems little research has been done in this department .... really want to build a ducted fan quad as the thrust over weight could produce a real corker of a quad if it works well. all comments and advice welcome !!!

regards rob 

[teslahed]

Ducted fans are less efficient at slow speeds than conventional props. They work quite well if you want a scale look and performance on a small to medium sized radio control ';jet'; aircraft but i don';t think they would work well on a multirotor aircraft.

You';d be using a ridiculous number of amps just to keep the thing in the hover and the only real advantage in flight would be a possibly higher top speed once you got the thing moving really fast.

I think you';d spend a lot of money on this project and get something that made a lot of noise and hovered for about 2 mins before the massive high capacity high cell count lipo it needed just to stay in the air ran down.

You';d be much better off with conventional props in some kind of prop guard if it';s the safety aspect that appeals and if you want to go fast just use smaller props and a higher cell count / higher KV motor to get an increased top speed.

[guest325]

I';ve played about with an extended prop guard with an aerofoil section, only on the bench though - it';s a bit like an edf but with a conventional motor/prop setup. What it seems to do is stabilise the air vortex and improve efficiency. I';ve  not been convinced enough to spend the money to try it out on  a quad though because I know that it just complicates things and I';ve got no idea how it might affect the manoeuvrability of the model. I think it';s likely that to get the best out of such a system it would need the motors/shrouds to be movable to vector its thrust.

[robshaw]

Would be cool tho! :-)

[Biffa]

Ducted fans are less efficient at slow speeds than conventional props. They work quite well if you want a scale look and performance on a small to medium sized radio control ';jet'; aircraft but i don';t think they would work well on a multirotor aircraft.

Any EDF multi rotors I have seen just scream their nuts off hovering as the EDF units struggle to shift enough air. They don';t work like a conventional prop at all and are really good at moving air that is already moving (if that makes sense) but not when stationary.

[kilby]

As has been touched upon you would probably need to use vectored thrust as ducted fans wouldn';t work with the regular steering of a quad between very high speed fans and inertia the control would be incredibly vague (if even possible)

A tricopter may be achievable though

[teslahed]

http://youtu.be/yQILzdfmXuk

It';s been done but the above video would seem to support mine and biffa';s reservations.

Don';t let that put you off if you really want to try. You could prove us / the guys who';ve already been there and done that wrong. But i wouldn';t put money on it being much of a success.

If you try make sure you post up your results

[miniconverter]

I don';t think it will work. I have a few ducted fan planes and to be honest all they do is go fast (but not that fast).

Take off can be troublesome as they tend to accelerate very slowly needs a good run. In flight varying the throttle between mid and full make very little difference, they are just unresponsive which isn';t what you want in a quad.

Then as already mentioned flight times will be horribly short, some of mine I start to make a landing at two and a half minutes because by three minutes the battery is down to less than 20%, and that';s with only 1 ducted fan. I think for 4 70mm fans you would need a 10,000 Mha battery for 2.5 to 3 minute flights.

But don';t let me stop you have a go it will be interesting if nothing else. keep us posted

[Biffa]

This is one of those things that if it was any good it would have been marketed already or there would be lots about.

The fact that there isn';t lots about tells you something.

[Hands0n]

I was looking at this earlier in the year, having seen a few videos on YouTube also. It looked different and seemed like a neat idea.  The more research I did on it put me off the idea eventually as there were no real gains to be had other than the aircraft being a bit unique.

[Cloudbuster]

what i want to build is something with about 400mm wheelbase but with loads of thrust to spare !!! researching around the web it seem quite possible to get about 10kg of thrust from 4x 70mm EDF that in anyones book is pretty good...even using 8000mah of 6s batteries it should be able to return about 10mins of useful flight time if the weight is kept to about 3.5kilos... looking at what others have done it does seem to be a bit of a strange old bird with lots of whirring and stuff but making a small but powerful quad that cannot decapitate you seems appealing...will have to allocate some funds to RND LOL !!!

regards rob

[miniconverter]

I have 70 mm ducted fan in one of my planes it makes no where near 2.5 kg of trust, not measured it but feels about half that. As for duration 4 70mm fans on a 8000 battery or the equivalent of 2000 per fan  lucky to get 3 minutes.

Not guessing here as I fly ducted fans and know how power hungry they are for not particularly good power outputs.

But having said that I still wish you luck.

[kilby]

Just to say that despite sounding negative I would love to see a ducted fan monster in the air

[Cloudbuster]

Thanks to all for your input !!! Clearly a subject that needs further investigation and research plus a practical prototype needs building !!! I will keep you all posted ...

Regards rob   

[Biffa]

Let out negativity drive you to prove us wrong

[shazzy]

Considering normal multirotors use counter spinning props, can you get edf units with counter spinning fans?

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[Cloudbuster]

Considering normal multirotors use counter spinning props, can you get edf units with counter spinning fans?

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yes !!!