New to EDFs, Power setup question - RC Groups
Thread Tools
Mar 29, 2011, 09:14 PM
Registered User
Question

New to EDFs, Power setup question


I'm usually a parkflyer prop or a slope/small thermal type of flyer but at the moment I'm designing a balsa built up plane, 2m wingspan and i'm looking at putting in an EDF, i've room for a 70mm but i have no idea how much power these can put out. It doesn't need to have an aerobatic power to weight, maybe just a little more than an electric sailplane, or enough to takeoff from concrete would be awesome.
SO I have two questions, 1) Does a single 70mm EDF have enough power to do so, without being prohibitively expensive and 2) could someone suggest a brushless setup that might do the job (please) I have no idea even how much current EDF's draw compared to their prop'd counterparts
Sign up now
to remove ads between posts
Mar 29, 2011, 09:59 PM
Registered User
SilentHunter's Avatar
How much does your plane weigh, and how much thrust do you want, and how much battery are you willing to cary?

~2-5 pounds of thrust can be had from 70mm's, the more thrust the more expensive and power hungry. Simple.
Mar 29, 2011, 10:25 PM
Registered User
well it's still in the design stages and I have no idea how to judge weight before it's assembled.
I am in need of replacement batteries for another plane, it was running 3300mAh 20C 3cell lipos so if it could run off something same that would be a benefit, all other batteries I stock are sub 1200mAh
Mar 30, 2011, 12:32 AM
Registered User
LuvEvolution7's Avatar
typically, 70mm needs 4S or 5S packs. they are very lame on 3S at best and too powerful on 6S if you were to put two packs in series. you could always put your 3S packs and 2S packs in series to make a 5S pack. it wouldn't take too much cash to buy 2S packs, so that's always an option. on 5S, there's no reason why you can't make 4+lbs of thrust. if your plane is light enough, you may even get away with power from a 3S pack. it all depends on planform, size, weight, etc.

basically, we are missing vital information from you. what kind of plane are you building? is this a glider-type, trainer-type, etc, etc.? this will drastically affect feddback given, since it would take much less power to fly a glider than a fighter style aircraft. the point is, we need to know more information, before a proper assessment can be given.

some basic info for you though.................for EDF application, the minimum you want to go with, are 30C packs and 3300mAh packs are kinda low. remember that Amp draw will be significantly higher than your prop jobs, so you want more than enough gas in your tank and the delivery system you need to do the job you are asking of it. let's say you have a prop job that draws 18 Amps at WOT. for the same size EDF, you could be well in excess of 40 Amps, just to give you an idea. so your prop packs might not do so well in an EDF application. that being said, 30C packs should be adequate.

with your 20C 3300mAh packs, you have 3.3 Amps X 20C = 66 Amps. if you have 30C packs, you get 3.3 X 30 = 99 Amps. if you were drawing 45 Amps continuous, you can see that the 30C packs are much happier and will last longer, since a smaller percentage is drawn than the max that they can handle. furthermore, if you increase the pack capacity, the packs would last longer still because the percentage drawn would be less. these are all things to consider when designing an airplane. basically, give us more info for more help.

Rich
Mar 31, 2011, 08:32 AM
Registered User
Thanks Rich, that really is the type of info I need, particularly about running on 4S not 3, My 3.3Ah packs are virtually toast anyhow so I need replacements and the other platform I was using them in is flexible.
More info about what I'm building, It's easier to ask if you've seen the new Tron than to explain it. So if you have, it's the 3 person LightJet near the end of the movie. If you haven't, then I'm building a blended wing/body ship with a 2m wingspan, a chord that varies from 24.5cm (~10") to 11cm (~4") but with forward swept V-tail that has a span itself of 80cm (~32") and nose to tail is only about 75cm (~30"). Attached is a top down pic of the design in progress to give you an idea (I like building and designing but hate cutting parts so I send them for laser cutting once I'm ready)
It'll be flown virtually as a glider minus the thermaling plus a few rolls, I'm hoping for a low enough wingloading that I could slope soar it if I chose, but with the lack of good slopes in my area I'm putting in an EDF and landing gear
Mar 31, 2011, 09:00 AM
Registered User
Having just written all out, that's huge, thinking it'll be too heavy made of wood so I'll likely scale it it to 60"
Mar 31, 2011, 09:32 AM
Registered User
LuvEvolution7's Avatar
sounds like an interesting project. consider making it out of Depron to get the weight you want. it'll be lighter than would and just as strong, if you use Carbon Fiber in strategic locations such as wing spars, etc.
Apr 03, 2011, 03:47 PM
Registered User

pic


I need more pic's
Apr 04, 2011, 08:43 AM
Registered User

Cad


Wing not as big as i thought
Last edited by space 1; Apr 04, 2011 at 12:55 PM.
Apr 05, 2011, 03:42 PM
Registered User

better


better fuse
Apr 05, 2011, 11:36 PM
Registered User
yeah it will be similar to that but the v-tail will be lower (the pontoons attach to it) and EDF will be below the cabin. her are some movie screenshots for reference
Apr 06, 2011, 05:44 AM
Registered User
NOW i got somthing to work with. i think pontoons are for guns i did V tail at 110 deg as per design rule's ill change just quick cad to see
Apr 06, 2011, 09:27 AM
Registered User

cad


At some point one has to use physics in order to fly
Last edited by space 1; Apr 08, 2011 at 05:34 AM.
Apr 07, 2011, 09:00 PM
Registered User
Yeah that looks about right. I haven't had a chance to do any more work on it lately. I did notice the tail in the movie pics looks a too little flat to give much rudder authority, something like 130deg. And the inboard parts of the wing where the chord gets short aren't tapered at the TE so the air would be turbulent and draggy. You're right that perhaps they weren't thinking too much about physics


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
For Sale Thunder Power 3800 45C 8S setup! Brand New!! TJMoore Aircraft - Electric - Power Systems (FS/W) 1 May 30, 2011 06:08 PM
Discussion RCLander DPS EDFs thrust power testing Tim Wan Foamy EDFs 4 Feb 23, 2011 12:39 PM
Discussion Question about my new Radian receiver setup nkcook Electric Sailplanes 2 Dec 08, 2010 06:02 PM
Discussion ESC question for pair of EDFs JGuilty13 Power Systems 6 Dec 03, 2010 11:39 AM
Discussion Power setup question jwf1999 Foamy EDFs 2 Oct 10, 2010 08:40 PM