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Thoughts on ducting the indoor hull

Mirumod, Macgyver, hull, cam, propeller, leg, cross, ball bearing mods... etc.
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TommyAtomic
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Thoughts on ducting the indoor hull

Post by TommyAtomic » 09 Oct 2013, 21:41

I was reading a posting over on DIYDrones about someone who built a quad using EDF's (electric ducted fan) instead of a standard open prop like on most quadcopter and there was a discussion regarding both the safety and efficiency of ducted fans.

Quoted from the comments:
"A ducted fan with the same prop diameter as an un-ducted prop is 10-15% more efficient and quieter, so that could make up for the extra weight of the duct itself. The problem is that all the ducted fans out there are designed for airplanes and have too small of a diameter for drones. "

"A properly designed ducted fan adds up to 60% lift.
that may not be offset by the added weight of the duct
(Singh, Shape Optimization of a Ducted Rotor System for Aerodynamic Performance, 2011)"

There is obviously some disagreement on the efficiency added by ducting. Regardless the AR.Drone 2 doesnt really have ducts. The Indoor hull really only has bumpers. Has anyone considered using strips of cardstock or a light flexible thin plastic to extend perhaps 2 to 3cm above and 4 to 6cm below the bumper to form actual ducts for each prop?

If light enough and of the right shape (cylindrical is probably most useful) it could certainly make use of the indoor hull less stupid. The software and sensors in the drone should automatically decrease motor rpm to maintain elevation regardless of any increase in thrust.

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Re: Thoughts on ducting the indoor hull

Post by Jayson Hanes » 09 Oct 2013, 23:29

I used to be in the Car Audio world back in the early 90's.. we used to make door pods (and other pods in general) out of a rigid frame, stretch speaker grill cloth over it and hot glue it into place.. then we'd brush on fiberglass resin. Let it harden, sand it up and cover 'em in vinyl or paint them. This method makes organic looking and contoured shapes that are light and strong. I have been toying with the idea of doing similar for a hull.. but now you have me thinking that this might be viable for ducted fan type stuff!... hmmmm..

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Re: Thoughts on ducting the indoor hull

Post by pbody2013 » 09 Oct 2013, 23:35

The key is "properly designed" I'd guess. Sounds cool though and I think you should have a go at it to see if it can be done :P . Maybe someone could 3D print some parts as well.
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Re: Thoughts on ducting the indoor hull

Post by Jayson Hanes » 10 Oct 2013, 03:09


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Re: Thoughts on ducting the indoor hull

Post by DBS » 10 Oct 2013, 03:18

So from my understanding here... simply throwing a barrel around a regular , 2 bladed prop design , isn't going to gain enough to make up for the added weight of extra materials... and the tight tolerances needed between the prop tip and duct aren't going to lend themselves well to a floppy indoor hull held on by a magnet that moves around quite a bit...

Somebody else was talking about this early last year and the weight of making just one duct on one prop location shut the whole thing down.
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Re: Thoughts on ducting the indoor hull

Post by Jayson Hanes » 10 Oct 2013, 03:29

"The ducted fan produces more thrust than an open propeller, and for the same thrust it uses 30% less power"


Direct link: http://www.youtube.com/v/WSi5zIrK7mE

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Re: Thoughts on ducting the indoor hull

Post by Schlauncha » 10 Oct 2013, 03:50

That's pretty cool. A much more simple and elegant version of this beast I built:


Direct link: http://www.youtube.com/v/ET_s5zFBV8w

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Re: Thoughts on ducting the indoor hull

Post by TommyAtomic » 10 Oct 2013, 17:43

DBS wrote:So from my understanding here... simply throwing a barrel around a regular , 2 bladed prop design , isn't going to gain enough to make up for the added weight of extra materials... and the tight tolerances needed between the prop tip and duct aren't going to lend themselves well to a floppy indoor hull held on by a magnet that moves around quite a bit...

Somebody else was talking about this early last year and the weight of making just one duct on one prop location shut the whole thing down.
Well here's the thing. I'm NOT suggesting that a bit of ducting is going to turn the indoor hull into a performance replacement. I'm just thinking that little a bit of arts and crafts materiels might turn the indoor hull into less garbage.

The indoor hull is foam so we're not talking aluminum, CF or exotic materials for ducts. Nor am I suggesting a massive ducting barrel the weight of which will absolutely exceed the utility. Its just a couple cm of material above and below the blades to direct a bit of propwash in a more usefull fashion.

Structurally for the purpose of experimenting I'm thinking stiff construction paper and a bit of doublesided tape. If I like how it performs I may give it a light coat of resin for additional stiffness, strength, and waterproofing although this may add weight. As for holding the hull on I've long since abandoned the absurd magnets in favor of velcro and rubber bands.

Regardless. I'll do some indoor experiments as the weather has turned less than pleasant lately.

Pass or fail pictures will follow eventually. I may get my wife to video the testflight of likely doom.

It seems completely impossible that anything not adding significant weight could perform worse than the indoor hull.

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Re: Thoughts on ducting the indoor hull

Post by DBS » 10 Oct 2013, 19:19

Anything is worth a try right? Interested to see how you make out :ugeek:
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