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Old May 24, 2015, 05:05 AM
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1 can never have 2 many planes
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Help!
home-made edf scratchbuilt jet

hey guys, im new to the whole edf gig and am looking for some words of wisdom to possibly improve thrust and flight performance of a micro edf i have built.

the airframe is based on a eurfighter and weighs 61g auw, the edf system is a home made 26mm 8blade producing about 50-55g thrust at 5a wot.

when im flying the plane it seems to be drastically under-powered and requires a relatively high aoa to stay in the air at max power. I know the cg is right... here is a pic to give an idea.
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Old May 24, 2015, 01:52 PM
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Hello! Nice little euro!
I think you answered your own question! You either need more power or a lighter airframe. The power requirements are very different for EDF's. At minimum - I prefer around 1.5:1 thrust to weight for my EDF projects. This will give you some 'pullout' power. Otherwise, once you slow her down, she will sit in high alpha and it will be impossible to get her out of it. I've been there before! . With your current setup you need speed to keep her in the air. A bungee launch may get you there but if you slow down or loose speed changing direction you will end up in WOT high alpha again.

Also, the addition of a thrust cone may improve your performance some but I believe you main issue is lack of power. Check out the scratch built EDF forum - there is a lot of great info on EDF over there.

Good Luck! Happy building & Flying!!!
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Old May 24, 2015, 06:10 PM
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Seems to me you need to move the CG a bit forward. High AOA means high drag which you don't want. Move the CG a little at a time and see what it does. Looks like you can move the battery a bit forward.
If you can lighten the plane, all the better.
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Old May 24, 2015, 07:26 PM
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Perhaps do to the edf being mounted above centerline, thus forcing the nose down? here is a pic of my flying wing I designed with an edf. If the thrust estimate is correct it should be about .9 to one thrust ratio, more than enough o fly.
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Old May 25, 2015, 12:20 AM
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Lighter flies better.
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Old May 25, 2015, 11:41 PM
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What did you mean by the EDF system is home made?
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Old May 26, 2015, 05:36 AM
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Quote:
Originally Posted by djacob7 View Post
What did you mean by the EDF system is home made?
home made as in I designed it and made it at home.. using a 3d modelling program and a 3d printer.
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Old May 26, 2015, 06:49 AM
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Ouch !

Very creative and Innovative , but !!!
Is it going to hold up to the High speeds of EDF use.
The centrifugal forces get pretty taxing for rapidprototyping models IMHO.

Just be careful when testing.
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Old May 27, 2015, 01:50 AM
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Quote:
Originally Posted by birdofplay View Post
Ouch !

Very creative and Innovative , but !!!
Is it going to hold up to the High speeds of EDF use.
The centrifugal forces get pretty taxing for rapidprototyping models IMHO.

Just be careful when testing.
thanks birdofplay

With regards to 3d printed props and such i always spin them up to 200% of max intended rpm..

and the housing has been tested in heavy landings during operation. So it all seems to be strong enough for the moment. As for long term durability, will have to be observed over time.

Trying to be careful

88
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Old May 27, 2015, 06:13 AM
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That is good to hear and I am amazed.

When I retired 10+ yrs ago all the Rapid Prototype machines made Brittle, unusable
parts for show only. Paint em up and pass em around ( but they were dummies )

Glad to hear things have dramatically changed.
I might even have to get myself a 3D printer set up.

What are you using Printer and Material wise ?

OMG I just looked at your uploads -wow !
How did the 20 blade work out for you ?
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Old May 27, 2015, 06:42 AM
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I am using a flashforge creator dual.. the housing is abs because its stronger and the impeller is pla because its more rigid.. however if it were to come into contact with something at operating speed, well lets just say there would be much left.. the trick with printing impellers, housings and props is the design, is it structurally sound?.. build approach, will the layers assist the strength and balance of the object. Its a project ive been workin on for quite a while and its starting to work out for me. The 20blade does work however the one in the pic was the first version. Needs a slight design mod to balance properly.. also with micro edfs it seems that every gram of thrust is essential. The 20 blade impeller might be better suited to 55mm or larger edfs where a trade of less thrust for increased cool factor is acceptable.

Atm 8 blade is producing the best thrust but this weekend ill have time to tinker with it some more..

You can check the progress out here or on my fb page @ 3d aeroworks

88
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Old May 27, 2015, 03:06 PM
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With an edf you need the efflux speed to be relatively high any idea on the efflux speed of your design?
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Old May 31, 2015, 05:15 PM
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1 can never have 2 many planes
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Quote:
Originally Posted by TANGOSIERRAROM View Post
With an edf you need the efflux speed to be relatively high any idea on the efflux speed of your design?
ah ok, na i dont have any idea. maybe i need to get myself an anemometer.
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Old Jun 01, 2015, 04:47 PM
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I think it is likely to have an efflux speed of about 30mph I could of made a horrible miscalculation there, it seems low, If is is then your dynamic thrust when the model is flying at 15mph is going to be 27g
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Old Jun 07, 2015, 02:43 AM
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1 can never have 2 many planes
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Quote:
Originally Posted by TANGOSIERRAROM View Post
I think it is likely to have an efflux speed of about 30mph I could of made a horrible miscalculation there, it seems low, If is is then your dynamic thrust when the model is flying at 15mph is going to be 27g
thanks for the prediction.. i got it flying rather well now. contrary to what i said before the CG was way WAY to far forward. about 10mm to far forward for a total root chord of 160mm.. lol anyway previous to this it was still flying ok but it needed quite a lot of up elevator trim to fly level. ive moved it back to its limit and then forward a touch for good measure. now she floats around the sky with ease at about 50-60% power. i also added a thrust tube reducing to 80% FSA to max eflux at the exhaust. yeah it doesnt accelerate like a rocket but it gets goin. id say 80kph max.. only a steady cruise i get about 5min before the battery dies so say 4min 30 sec of safe flying. the first version of this eurofighter is starting to look a little used. but i was expecting this with a power system i designed and built myself. im currently building an f-86 sabre to replace the eurofighter.. but the eurofighter does look good so i may build another to fit out as well.
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