air multiplier quadcopter

I havent been in this forum for a while and the 2 posts that had been updated since I was here last were the ais-multiplier thread and the quadcopter thread. I wonder if we could make a super efficient air multiplier quadcopter?

now that would be cool. I wonder if we could make the quad copter powered by a single fan in the middle blowing air into four air multiplier ducts.. then control the thrust of each by managing the apertures to each duct. Then you could have a gas powered quad copter that was not obscenely heavy... Plus it would be super safe and crash resistant because the spinning part is hidden in the middle.

... but then you'll need a more powerfull motor and bigger blades and 4 servos controlling the ducts - this will make your copter heavier than with 4 motors on the outside.

Some twenty years ago I've built a hoovercraft with only one motor in the middle and two ducts left and right, for steering.

The motor was powerfull enough to elevate the hoovercraft 5cm, but the air passed through the ducts didn't have enough power to drive against the wind, so we used it only when there weren't any wind ...

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

Well maybe the air multipliers will Compensate for the power loss you get from channeling air through ducts... Although I kinda doubt it. Well even if you did have the same number of fans it would still be more crash resistant. In fact I'm not sure if air multipliers would even help create more lift than you'd get from just powering fan blades directly. I do think it's worth a try though...

Besides servos are much lighter than props and motors. Although I'd be interested to hear an answer to the lift question first before thinking about weight issues.

... oh, it's working - in the 50-ies the US-army built some 'flying discs' with a propeller in the middle and ducts feeding the air around.

But then drop the design for common helicopters ...

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

however in the 50s they didnt have tiny computers to control the duct apertures like we have now. Perhaps with computer control an unstable and difficult to control aircraft like that could be a lot more feasible. A lot of the reasons why "regular helicopters" are what we are stuck with now is because it's a self stabilizing design and thus easy to control. Because we are not limited any more to human reaction times in control systems we should feel more free to try more radical flight designs.

Plus it would look super cool if it worked.

I'm still interested in the air multiplier lift thing..

One thing to realize here is that the more mass you push off from, the less Force/Power you can potentially get!
F= ma, E= mv^2/2, so P=dE/dt = mva , so F/P = ma/mva = 1/v, that is equivalent to needing more mass to push off, because v is the speed it goes past the blades.

So tri/quad copters are the way to go because they can get the most area, basically. However, i think efficiency can still be improved by adding passive parts.

Windmill efficiency aught to be relevant to props too.(i think..)