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Old 10-13-2018, 07:58 PM
  #1  
Hue
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Hello.
Im asking about electric ducted fans for a project.
This idea could be a total disaster and already tried and failed but I've never heard of anything like that.
The concept is to fill a paraglider wing with hydrogen and then power the harness with EDFs.
The hydrogen dirigible wing is not designed to lift everything, simply to contribute to the lift and maintain rigidity of the wing/canopy to prevent collapses.
So I need lightweight, high thrust EDFs to create forward momentum and lift from the aerodynamics of the wing/canopy.
I'm also interested if someone can provide information regarding whether this has been tried before and/or whether it has already been shown to be impossible.
Thanks all.
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Old 10-13-2018, 09:36 PM
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Brner
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Not sure if it's been done or not but Helium would be a much better choice for the gas....remember the Hindenburg???
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Old 10-13-2018, 09:56 PM
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Hue
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Yup. That is a definite consideration. Helium is quite rare.
Hydrogen is more plentiful and much much less expensive.
A system that could recycle helium utilizing a compressor could work but weight is a factor.
While hydrogen is dangerous, it is no less manageable than petrol etc. But again, you are correct about that concern.
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Old 10-13-2018, 10:32 PM
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pizzano
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Originally Posted by Hue View Post
Yup. That is a definite consideration. Helium is quite rare.
Hydrogen is more plentiful and much much less expensive.
A system that could recycle helium utilizing a compressor could work but weight is a factor.
While hydrogen is dangerous, it is no less manageable than petrol etc. But again, you are correct about that concern.
I haven't any idea where you are located on this globe....however, hydrogen is not a wise selection for your application for many reasons....although lighter than Helium, Nitro is 10 times more volatile and much more expensive here in the U.S.........a small tank of Helium (enough to fill 50 standard size latex balloons) costs approx. $25.00....where as the same size tank of Nitro runs about $60.00 and could take a special permit to purchase.........Just saying.......given an electrical power application to the craft, the slightest possibility of a random spark will certainly ruin your day and more than likely be cause to consider law enforcement to get involved........since you've just constructed and exploded a bomb.....!
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Old 10-14-2018, 01:15 PM
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Ignoring the considerable dangers of hydrogen for a minute is there a particular reason for using EDFs?
They are much less efficient at creating thrust than for the same power delivered through a propeller and by a factor of at least 2!
Using EDFs rather than props you would either have to carry twice the weight of batteries or have half the power endurance.

Then of course there is the fact that hydrogen forms an explosive mixture anywhere between 4 and 74% concentration in air. When you connect a battery it creates a spark and that's all it takes!
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Old 10-14-2018, 09:40 PM
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Hue
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Thanks for that.
I had my doubts about the EDF weight/thrust ratio compared to traditional propulsion. EDFs are safer in that they are enclosed and more manageable if one was to include some directional control.
But to hear they only have 50% efficiency is appreciated and probably means they wont be suitable.
In terms of the hydrogen, I'm a bit bemused someone lept to "nitro".
We have hydrogen cars, fuel tanks, storage stations etc. No dramas.
The concept I'm trying requires hydrogen in the wing. It is not connected to any electrical component. The wing doesn't have any (metal) support structure that could cause a spark.
Paramotors fly around with several litres of gasoline on board. We don't "light up" while flying. lol
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Old 10-15-2018, 01:07 AM
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Hue
Yes indeed there are hydrogen powered cars but in that case the gas is contained in very strong metal containers that have to be able to withstand accidents and fires.
The volume of hydrogen outside the canister at any one time is very small and is always fully contained within strong metal structures.

What you are proposing is 'free' hydrogen contained only by a fabric which unless fully treated with a gas impermeable membrane will leak considerably. Just to make matters worse the very nature of the hydrogen molecule means it will readily pass through a membrane that would effectively stop normal atmospheric gases like nitrogen & oxygen.

Without knowing the details of your project it certainly appears that using hydrogen for lift is likely to be more trouble than any possible advantage it may have.
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Old 10-15-2018, 01:08 AM
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"We have hydrogen cars, fuel tanks, storage stations etc. No dramas.".....Same applied to the Hindenburg, for a bit......then, well history is replete with that story....
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Old 10-15-2018, 01:19 AM
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Hue
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Titanic sunk.
We still.use boats.
Fuel tanks explode. We still use them.
Hydrogen balloons exist.
And they can stay inflated for prolonged periods despite the small.molecule.
I appreciate everyone's concerns over the hydrogen gas scenario but the enquiry was about the efficacy of the EDFs.
Thanks.
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Old 10-15-2018, 01:27 AM
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What would the bag be made out of to contain either Hydrogen or Helium?



Helium will go right through the latex used in balloons, admittedly slowly unless the interior of the balloon is coated with a sealer. Mylar is much better.


It just seams like there would be so many places that the seal would have to be perfect.
I know it would drive me nuts.
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Old 10-15-2018, 02:36 AM
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ron_van_sommeren
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You could ask this group about dealing with hydrogen
groups.yahoo.com/neo/groups/rc_airship_regatta/info

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Old 12-22-2018, 11:35 AM
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Flite-Metal
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First: Paraglider powered by an EDF ducted fan is nothing new. It should be an easy and simple project. There was one for sale at Toledo a number of years ago. I inexpensive EDF availability with anything close to 80% thrust to weight ratio should make this a rocket!

Second: Sealing a pocket area with a latex rubber sealant/waterproofer should do the trick. You may be able to literally sew the cavities in the latex rubber covered Coverite or other covering fabric or for that matter polyester dress lining.

Third: Listening to the video sound led me to believe the guy was trying to fly on a windy day...
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EDF-Para.jpg (24.9 KB, 126 views)

Last edited by Flite-Metal; 12-22-2018 at 11:55 AM.
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