How do I know what size of edf to use?

[AeroPointIndustries]

Hey everyone! I want to start building some edf planes, but I have zero idea what size of edf to use for each size of plane. The first one I want to build is a 25ish inch long wingspan f-35 b that looks like this. Any ideas? Also, what's the best way to mount it inside?

 

[AeroPointIndustries]

Hey everyone! I want to start building some edf planes, but I have zero idea what size of edf to use for each size of plane. The first one I want to build is a 25ish inch long wingspan f-35 b that looks like this. Any ideas? Also, what's the best way to mount it inside? View attachment 201768

By the way, that's just a prototype. It'll look better when I finish the design.

 

[Ketchup]

I have no experience with EDFs, but @Mid7night, @The Hangar, and @Grifflyer may be able to help

 

[Ketchup]

Also as a first EDF I would recommend building Grifflyer's grunjet or an FT viggen. That way you can build an EDF to learn how they work and get a feel for them and their flight characteristics before designing your own.

 

[leaded50]

weight on the plane is of need, to find EDF with enough thrust

 

[AeroPointIndustries]

I don't know the exact weight, but I'd estimate around 400 grams with everything in it. 2-3 sheets of foam, 2 servos, 1 edf, 1 esc, and a 4s battery(what I would expect) Does that sound right? Also i'm open to doing a bdf style build too. Just don't know what motor or prop.

 

[AeroPointIndustries]

Maybe 500 grams?

 

[The Hangar]

A 50mm fan would be your best bet.

 

[AeroPointIndustries]

Really? That small? I wouldn't have expected that. How much bigger would ai have to go to use a 64mm? I wanna make a viggen first because of the logical suggestion, and it uses a 64mm, and I don't really want to buy 2 right now.

 

[The Hangar]

Really? That small? I wouldn't have expected that. How much bigger would ai have to go to use a 64mm? I wanna make a viggen first because of the logical suggestion, and it uses a 64mm, and I don't really want to buy 2 right now.

Let’s see, so the viggen has a 27.5” WS. You’d probably be fine at a 25” WS but I would make it a couple inches bigger for the 64mm edf.

 

[Matthewdupreez]

Also as a first EDF I would recommend building Grifflyer's grunjet or an FT viggen. That way you can build an EDF to learn how they work and get a feel for them and their flight characteristics before designing your own.

or The AP EAZY EDF

 

[AeroPointIndustries]

or The AP EAZY EDF

What's that?

 

[AeroPointIndustries]

Let’s see, so the viggen has a 27.5” WS. You’d probably be fine at a 25” WS but I would make it a couple inches bigger for the 64mm edf.

Okay! And what battery would you recommend for both?

 

[The Hangar]

Okay! And what battery would you recommend for both?

If you get a 4s fan then I would use a 1500 or 1800 4s pack, and if you get a 3S fan you could get away with a 2200.

 

[cyclone3350]

I am designing my first EDF. Too be honest I haven't much of a clue myself. So I closed my eyes and threw a dart @ a wall to came up with this formula. I am taking my estimated AUW and add 10% to that. I look @ the MFG static thrust rating and take 85% of that. If I end up with a thrust no. = or greater than the AUW + 10%, then I am assuming it will @ least get in the air. Like I said, a stab in the dark, but I hope to find out in a couple of months just how well that idea turns out.

 

[OliverW]

What's that?

Its basically a mini explorer, with an edf on top. It wouldn't give you the best jet characteristics since it would be so floaty

 

[quorneng]

How much thrust you need depends very much on the planes aerodynamics.
Modern jet fighters are designed to go supersonic which make them poor at slow speed. This does not matter too much in full size as they need plenty of thrust anyway needed to go supersonic.
However if you choose a 1950s jet subsonic design they had to have efficient aerodynamics to simply fly well given the limited thrust available from the early turbo jets.
About the only difficulty is a low powered jet only needed a relatively small area inlets. A configuration that does not suit an EDF so you may have to make the inlet oversize or add additional 'cheat holes' to allow the EDF to breath properly.
Remember for a given airframe the thrust to fly is proportional to the total weight so everything needs to be as light as possible.

 

[AeroPointIndustries]

How much thrust you need depends very much on the planes aerodynamics.
Modern jet fighters are designed to go supersonic which make them poor at slow speed. This does not matter too much in full size as they need plenty of thrust anyway needed to go supersonic.
However if you choose a 1950s jet subsonic design they had to have efficient aerodynamics to simply fly well given the limited thrust available from the early turbo jets.
About the only difficulty is a low powered jet only needed a relatively small area inlets. A configuration that does not suit an EDF so you may have to make the inlet oversize or add additional 'cheat holes' to allow the EDF to breath properly.
Remember for a given airframe the thrust to fly is proportional to the total weight so everything needs to be as light as possible.

There's not a whole lot of complex aerodynamics going on on my design. It has a flat foamboard wing since I can't make a good working airfoil for the life of me, so if there's a style of wing that has low lift that you know about, send me a pic.

 

[AeroPointIndustries]

Let’s see, so the viggen has a 27.5” WS. You’d probably be fine at a 25” WS but I would make it a couple inches bigger for the 64mm edf.

And I'll be sure to do that. I'm pretty sure this is the design thats the most likely to fly without too much effort. All of my other ones didn't work and I didn't know what to fix to make then work.

 

[AeroPointIndustries]

Is this a good battery for this edf? Edf: https://www.amazon.com/gp/product/B07C3RRKF1/?tag=lstir-20
Battery: http://www.valuehobby.com/30c-2200mah-4s-t.html